The meeting programme can be downloaded here


Ken Andersen

The mechanistic trait-based approach to fish

Fish are the dominant aquatic organisms in the body size range from about 1 g to 1 kg. Further, they are one of most diverse vertebrate groups with over 26 known species. Their exceptional high productivity support about 1% of global human consumption of protein with a value of about $1 bn/yr. Despite the huge functional and taxonomic diversity among fish I will demonstrate that just three fundamental assumptions — metabolic scaling, scaling of clearance rate with size, and the rule that big fish eat smaller fish — makes it possible to calculate the major relations relevant for fish demography, community structure, and evolutionary ecology. These relations can be used in evolutionary ecology and to support practical management of fish populations and communities, including fisheries induced evolution. In my talk, I will introduce the foundations of the trait-based framework for fish. I will demonstrate the applicability with examples and with a trait-based analysis of all fish species and an exploration of the differences between the two major groups, teleosts and elasmobranchs. Finally I will outline open questions and future applications and extensions of the framework.

Poster Session 2 on Tuesday at 17.30.


Lise Bacouillard

Raphaël Dupont, Céline Houbin, Cédric Leroux, Pascal Riera, Éric Thiébaut

Comparative evolution of functional diversity and isotopic indices in the Bay of Morlaix

Functional diversity through functional traits analysis is an approach which is more commonly used to evaluate the functional response of ecosystems to various natural and anthropogenic pressures. In parallel, the food web analysis by stable isotopes also allows to study the functioning of ecosystems by focusing on the matter and energy flows. These two distinct approaches can be complementary, describing in one hand the theoretical trophic niche from biological traits related to the feeding mode of species, and in the other hand the realised niche from isotopic signatures. The joint use of these two approaches has been tested on the multi-year food web monitoring set up in 213 in the Bay of Morlaix at the "Pierre Noire" station in the framework of the long-term monitoring program of the fine sand macrobenthic community established since 1977. This monitoring is based on the measurement of isotopic signatures (δ13C, δ15N) of (i) food sources, (ii) the 2-3 macrobenthos dominant species and (iii) demersal fish fauna. Biological traits related to feeding were determined from a literature review. As with functional diversity and its functional diversity indices, functional isotopic indices were calculated on the same principle to describe trophic diversity. Metrics take into account functional/isotopic richness, functional/isotopic diversity and functional/isotopic eveness. An analysis of the seasonal and interannual evolution of these metrics as well as the structure of the community was performed to see how the interannual changes in benthic community structure in terms of species diversity and functional diversity translate into changes in the food web.

Poster Session 1 on Monday at 17.30.


Dominik Bahlburg

Stefanie Moorthi, Bernd Blasius

Stoichiometric dynamics in a simple aquatic food web with implications for a changing Antarctic ecosystem

Rapidly increasing temperatures off the Western Antarctic Peninsula (WAP) directly and indirectly effect the complex network of geochemical, physical and biological processes within the local marine pelagic ecosystem. One of the proposed changes is a shift in the grazer community from Antarctic krill to the salp Salpa thompsoni with unknown consequences for the rest of the ecosystem. This study focuses on the feedback of internal macro-nutrient (N:P:C) composition of the dominant grazer (Antarctic krill or Salpa thompsoni) on the external nutrient pool and consequently phytoplankton stoichiometry in the WAP pelagic food web. Experimental data, long-term field data from the Palmer LTER as well as an NPZ-model incorporating the effect of variable phytoplankton stoichiometry suggest that changes in macro-nutrient composition of the dominant grazer have little effect on the phytoplankton macro-nutritional composition. The data shows that concentrations of bioavailable N and P are commonly very high in the waters of the WAP throughout the entire growth season which theoretically enables phytoplankton to take up both resources with almost maximum rates. Modifications of the supply ratio are then not reflected in the primary producer composition. Absolute external concentrations remain high and other factors such as light or iron limit growth before macro-nutrients can be exploited. As a consequence, a shift from Antarctic krill to Salpa thompsoni would have no notable effect on the phytoplankton macro-nutrient stoichiometry.

Poster Session 2 on Tuesday at 17.30.


Neil Banas

Copepod life-history traits along Arctic Ocean transport corridors: Scaling up from the lab to a rapidly changing seascape

Session B: Food-webs and Trophic Interactions



Joey Bernhardt

Anita Narwani

The evolution of competitive ability in phytoplankton

Competition for limiting resources is one of the most fundamental ecological interactions, and has long been considered a key driver of biodiversity patterns. Species' minimum resource requirements, their R*, are key traits that link individual physiological demands to the outcome of competition. Until recently, evolution was seen as a slow, varying constraint on species traits, rather than a dynamic feedback mediating shifts in abundance and the outcome of species interactions. A key question remains unanswered -- to what extent are species’ competitive traits able to evolve over ecological time scales? To address this knowledge gap, we tested the hypothesis that competitive traits of phytoplankton are able to adapt in response to selection under resource limitation. Alternatively, there may be limits to adaptive trait evolution; for example if resource requirements for different essential resources (i.e. nitrogen or phosphorus) are genetically or physiologically correlated. To identify potential constraints on evolved competitive trait variation, we grew five populations of Chlamydomonas reinhardtii for ~ 3 generations under seven different environmental conditions. We quantified the minimum resource requirements of the ancestral and descendant populations and the potential for rapid adaptation to alter the outcome of competition.

Session A: Traits, environments, ecology and evolution



Melanie Bon

Joao B. Gusmao, Maritza Fajardo, Jacques Grall, Chris Harrod, Aldo S. Pacheco

Biological trait analysis for revealing macrobenthic functioning along a depth gradient from normoxia to hypoxia in the Humboldt upwelling system

Decreases in dissolved oxygen (DO) concentration is a key stressor in marine environments. When DO concentrations fall below 2mL/L (i.e. hypoxia), benthic organisms are particularly affected due to their limited capacity to move to well oxygenated habitats. Hypoxia occurs naturally at shallow depths in some highly productive systems such as along the Humboldt upwelling ecosystem, particularly in South and Central Peru and Northern Chile. Such habitats are inhabited by opportunistic species characterized by their small size, short life cycle, and little or no parental care. In order to better understand how hypoxia affects the functioning of these benthic systems, macrobenthic functional diversity was studied along a gradient from shallow normoxia to deeper hypoxia. Macrobenthos were sampled monthly at 1, 2, 3 and 5m depth between October 215 and October 217 in two sites of Mejillones Bay, Northern Chile. We found that along a gradient from normoxia to hypoxia, feeding modes switched from carnivore and herbivore, to filter and surface feeders, and then to subsurface deposit feeders. In the deeper habitats with acute hypoxia, organisms were characterized by traits such as reduced movement and body protection, as well as asexual reproduction. In general, functional richness were lower in deeper habitats and this pattern was roughly maintained through the study period. However, in the deeper habitats of one of the site, macrobenthic functional richness and divergence (using Rao’s Q based on abundance) showed a tendency to decrease with depth and time. The results suggest a complete restructuration of the benthic trophic structure driven by hypoxia with potential to affect local food webs. Besides, the changes in the trait structure of such benthic communities also suggests that bioturbation-mediated sediment processes might be affected.

Poster Session 1 on Monday at 17.30.


B. B. Cael

Nick Hawco, Siobhan Braybrook

A tale of two cobalts // Quantifying leaf cell shape

Cobalt (Co) is an important micronutrient in the ocean whose geochemistry is relatively poorly characterized. In particular, the global turnover of Co is not well-constrained as different processes have been argued to control this turnover that have also been argued to operate on a wide range of timescales. Using corresponding radiocarbon measurements, we assign ages to a database of Co and labile Co (LCo) concentration measurements. We then use a regularized inverse Laplace transform to tease apart the multiple timescales of Co turnover. Surprisingly, Co turnover is robustly best characterized by a relatively sharp, bimodal distribution, with ~1/3 of Co turning over on a ~250a timescale and ~2/3 turning over on a ~1500a timescale. LCo, which is independently measured and constitutes ~1/3 of total Co, is robustly characterized by a relatively sharp, unimodel diststribution turning over on a similar multi-centennial timescale. LCo is chemically similar to the Co2+ ion and is susceptible to scavenging by Mn-oxidizing bacteria, whereas other Co is strongly bound by organic molecules and inert. Thus, somewhat surprisingly, it appears that the deep ocean total Co inventory is well-described as comprising two distinct pools, turning over on two distinct timescales, potentially by distinct mechanisms (e.g. bacterial scavenging & ventilation). // Leaves’ epidermal cells display a diversity of shapes, from regular and rectangular to complex and jigsaw-like. Understanding of the function(s) as well as the phylogenetic or environmental patterns of cell shape arguably remains elusive because of the unsatisfying shape metrics used to date. Drawing inspiration from potamology (river science), we argue that the natural shape metric is mean total absolute curvature. This metric is surprisingly weakly correlated with the more commonly used solidity metric for cells from hundreds of different plant species. We describe additional insight available from a curvature-based approach and discuss next steps.

Poster Session 2 on Tuesday at 17.30.


Pol Capdevila

Maria Beger, Iain Stott, Patrick Barks, Gwilym Rowlands & Roberto Salguero-Gómez

Are marine species more resilient to global change than terrestrial ones?

Despite drastic loss of biodiversity during the last decades, few documented extinctions exist in the marine realm when compared to terrestrial ecosystems. The underlying causes of such differences in extinction rates remain unclear, inevitably leading to the question “are marine species more resilient to global change than terrestrial species?”. To address this question, we used open-access databases including demographic information for over 4 marine and terrestrial species from around the globe and across the tree of life. To determine differences in the demographic resilience of marine and terrestrial species, we evaluated two components of resilience: (i) resistance to disturbances, and (ii) time to recovery. We also estimated the vulnerability of species to increases in environmental variability and to changes in environmental autocorrelation, using stochastic elasticity analyses. Our results suggest that marine species do not show higher demographic resilience, nor are more vulnerable to environmental change, than terrestrial ones. Instead, phylogenetic relationships and environmental factors were more important in determining species’ resilience and vulnerability to environmental change. Nonetheless, marine species’ population growth rate was more sensitive to changes in environmental autocorrelation than terrestrial ones. Considering that climate change will alter the natural regimes of environmental fluctuations, these findings suggest that marine species may be even less resilient than terrestrial species to global change. Overall, our results do not support the hypothesis that marine systems are more resilient than terrestrial ones, and indeed point towards the opposite conclusion.

Poster Session 1 on Monday at 17.30.


Laura Cappelatti

Alizée Mauffrey, John Griffin

Applying continuous functional traits to large brown seaweeds: variation across tidal emersion and wave exposure gradients

A functional trait-based approach seeks a general understanding of organism - environment interactions, but, among primary producers, its empirical basis rests on vascular plants. We hypothesised that with increasing intertidal elevation, traits of large brown macroalgae would reflect a resource-acquisition vs. conservation (stress tolerance) trade-off at species and community levels. Across the elevation gradient at four UK sites of varying wave exposure, we: i) screened species’ relevant morphological traits, using principal component analysis to reduce dimensionality; and ii) up-scaled species’ traits using community weighted trait means (CWMs). The first principal component (PC1) strongly related to specific thallus area and thallus dry matter content, representing an acquisition - conservation trade-off. Although species generally shifted to the conservative end of this axis as elevation increased, mid-shore Ascophyllum nodosum sat at the extreme conservative end. PC2 associated with holdfast ratio, thickness and length, with A. nodusum scoring higher than other mid-shore species. CWMs of PC1 decreased with elevation at two sites indicating a shift from ‘fast’ to ‘slow’ ecosystem functioning, but this relationship was disrupted by A. nodusum at the sheltered site, and by the up-shore extent of Laminaria digitata at the most exposed site. The anomalous traits of A. nodusum reflect its unique competitive strategy (slow, persistent growth) in the relatively stressful mid-shore. Seaweed functional traits show promise in linking species’ identities to their strategies and ecosystem contributions. However, because resource conservation traits can be related to competitive as well as stress tolerance strategies, predicting seaweed trait responses to environmental stress gradients is challenging.

Poster Session 1 on Monday at 17.30.


Emelia Chamberlain

Hyewon Kim, Scott Doney, Jeff Bowman

Leveraging microbial community structure data to inform traits-based modeling, an approach based on microbial community segmentation.

Numerical modeling is a critical method for understanding ecosystem processes. However, current approaches are typically not informed by microbial diversity data despite the rapidly growing availability of these data. One reason for this is that diversity data is high dimensional, with hundreds or even thousands of variables defined for relatively few time/space observations. This creates a discrepancy between the observed and modeled biological dimensionality that dramatically simplifies the diverse functionality of the microbial community within the ecosystem. In Bowman et al. (217) we introduced a technique to “segment” the microbial community into functionally coherent units (“modes”) that can be described by a single categorical variable. This categorical variable reflects the key genetic traits of the microbial community. From these genetic traits we can make reasonable estimates of physiology (e.g., respiration, bacterial growth efficiency, cell size), providing realistic initial conditions and a useful “check” against parameter optimization with data assimilation. Here we describe a strategy for implementing this approach with the Regional Test-bed Model, a 1-D data assimilative ecosystem model with parameters optimized for the pelagic western Antarctic Peninsula near Palmer Station. In a recent analysis of 16S rRNA gene data from a 5-year time-series of the region, we identified 8 recurrent modes in the bacterial community. Estimates of genome parameters estimated for each mode showed logical temporal trends in 16S rRNA gene copy number, genome size, and GC content. From these parameters we can make reasonable estimates of 1 key bacterial parameters in the model. During a model hind-cast of the time series, we will compare parameter estimates derived from data assimilation with our estimates for the observed mode. When the difference in parameter estimates exceeds a threshold, the model can be “corrected” to match the observed mode and the time-point flagged for further investigation. Ultimately, we expect this approach to improve the fidelity of traits-based ecosystem models, leading to a better understanding of complex ecosystem processes.

Poster Session 2 on Tuesday at 17.30.


Samuel Chan

Huang Danwei

Long-term monitoring reveals decline in trait-based functional diversity on coral reefs in Singapore

Long-term monitoring of coral reefs in Singapore has revealed changes in both live coral cover and diversity over time driven mainly by coastal reclamation, shipping and industrial activities. Data from these studies have only been used to examine community diversity and assembly in terms of species richness, which may not fully encapsulate differences among communities. Based on a 3-year reef monitoring dataset, we investigate temporal and fine-spatial patterns of taxonomic, phylogenetic and trait-based functional diversity measures for reef-building corals. Our analyses reveal that while most diversity metrics have remained relatively stable, the observed decline in functional diversity through time may highlight losses of particular reef functions. The temporal change is examined in the context of the small spatial separation among Singapore’s reefs, over which we detail divergences in trait diversity trajectories that may be related to specific environmental drivers. This trait-based diversity assessment thus offers the most consistent evaluation of the general decline that is apparent on the urbanised coral reefs of Singapore.

Poster Session 1 on Monday at 17.30.


Bingzhang Chen

D.J.S. Montagnes

Thermal diversity affects responses of phytoplankton community to warming

In order to reconcile the apparent dichotomy between the intra- and inter-specific activation energy and scale up from individual temperature performance curves to the community level, we propose to use optimal temperature as the master thermal trait to model the temperature responses of each species and the distributions of the thermal traits of the community. We parameterize the model using a global dataset of phytoplankton growth rates, in which significant thermal compensation is observed. Both the intra- and inter-specific activation energy can be well incorporated into the theory. The model simulations suggest that the community level activation energy is affected by the diversity of the thermal trait, which also indirectly influences community mean optimal temperature. We propose that the community level activation energy may not be a static quantity and urge that distributions of optimal temperature of natural plankton communities ought to be made.

Poster Session 2 on Tuesday at 17.30.


Chris Clements

Trait-based signals of collapse and recovery

Predicting population declines is a key challenge in the face of global environmental change. One potentially powerful approach to achieving this is to use shifts in fitness-related phenotypic traits such as body size as predictors of the response of populations to future stressors. Here I will detail recent work which has demonstrated how trait shifts can be used as early warning signals of approach population collapse, as well as community recovery, with a particular focus on marine systems.

Poster Session 1 on Monday at 17.30.


Larry Crowder

Elliott L. Hazen, Stephanie J. Green, Natasha A. Hardy

Oceanic Predators under Climate Change: Changing Distributions and Dynamic Trophic Connections in the California Current

The California Current provides an excellent opportunity to enhance our understanding of the role of climate factors in the changing distributions of pelagic predators. These changing distributions have been documented empirically in response to both short term (El Nino/La Nina) climate variation and longer term environmental changes along the Pacific coast. Current food web models involving these predators tend to be temporally or spatially limited and often frame trophic connections based on sparse and dated diet data. A traits-based approach to these trophic interactions should allow us to better understand and manage emerging food webs under climate change. We have modeled responses of pelagic predators to fixed and dynamic features using dynamic habitat models that link remotely sensed oceanography and satellite tracking data to forecast distributions and seasonal movements of these animals relative to environmental variation. This research has allowed us examine the spatial and temporal dynamics of protected species relative to bycatch in fisheries and to ship strikes. We have also extended this work to forecast the changes in distribution and habitat volume of 15 pelagic predator species over the next century. Although these approaches can be powerful and foster the possibility of dynamic ocean management, the models are currently limited by the lack of a robust approach to novel trophic connections.

Poster Session 2 on Tuesday at 17.30.


Stephanie Dutkiewicz

Phil Boyd and Ulf Riebesell

Biogeochemical and ecological redundancy in phytoplankton communities

Global change driven stressors such as warming, ocean acidification and alterations to resource supply are likely to have differing effects on the diverse set of phytoplankton species. Differing responses are likely to lead to extinction of some species. Here we explore how losses of species, and their specific traits, might impact the marine biogeochemistry and ecology. We use a global three-dimensional model that includes functional and size traits to capture complex regional diverse planktonic communities. The communities encompass size classes from .6 to over 2um, and several functional groupings (e.g. diatoms, diazotrophs) and trophic strategies. We run a series of experiments where we remove a single size class, functional group or combination of phytoplankton types to explore redundancy in phytoplankton communities. We find that removing nitrogen fixing phytoplankton has the largest impact on biogeochemical properties such as global primary production. However, interestingly, we find that removing size classes and functional groups (other than diazotrophs) has little impact on globally integrated primary production, but many of the experiments do show large regional shifts in biogeochemsitry. We also find non-intuitive ecological changes, with shifts in the rest of the communities and large impacts on higher trophic levels in almost all experiments. Our results suggest a lack of ecological redundancy, though potentially more biogeochemical redundancy, but only when placed in a global context.

Session E: Biodiversity and ecosystem function



Kyle Edwards

Grieg F. Steward, Christopher R. Schvarcz

Size as a master trait in viral ecology

Body size is often called a 'master trait', due to the pervasive effects of size on metabolic rates, predator-prey relationships, biomechanics, etc. Viruses vary substantially in size (~5-fold in diameter and ~1-fold in genome size), but the selective forces that drive the origin and maintenance of viral size diversity are poorly understand. Here we develop theory and synthesize data for key virus traits and how they scale with virus size, to consider the fitness advantages of small vs. large size and how these may be selected for under different conditions.

Poster Session 1 on Monday at 17.30.


Brian Enquist

The past, present, and future of trait-based ecology: Toward a more predictive framework

Session A: Traits, environments, ecology and evolution



Emile Faure

S.D. Ayata, L. Bittner

From genes to functional traits in the global ocean : building de novo plankton functional types from environmental metagenomics data

One global challenge of the XXIst century is to understand and predict the impacts of anthropic climate change on ecosystem functioning. In the ocean, planktonic organisms play a crucial role in climate regulation, global biogeochemical cycles, and marine trophic networks. Models coupling physics and biogeochemistry are a widely used tool to quantify biogeochemical cycles through the simulation of planktonic ecosystems dynamics. But these models often rely on a biogeochemical view of marine plankton, since they describe dynamics of functional groups historically described by marine biogeochemists (known as Plankton Functional Types, or PFT). These groups have been criticized for their lack of ecological justifications, potentially leading to an oversimplified representation of planktonic diversity in models. However, the lack of data-driven methodologies to determine and quantify the potential and realized functional traits of planktonic communities still prevent marine ecosystem modelers from implementing realistically diverse planktonic communities into models. Here, we addressed this problem by building de novo plankton functional types from metagenomics data. More precisely, we used a set of 885 procaryotic metagenome-assembled genomes (MAGs) built from the Tara Oceans metagenomics data by a precedent study. For each of these MAGs, we detected and translated gene domains to protein sequences, and gathered the genes relative abundance in the Tara Oceans samples. A sequence similarity network was then built to create groups of homologous proteins that potentially participate to the same metabolic pathways. The functional annotations of these sets allowed to define groups of proteins linked to biogeochemical functions, e.g. photosynthesis or nitrogen fixation. We investigated the distribution of each of these sets across the global Ocean in perspective of the environmental conditions. This non-arbitrary and data-driven approach allows to quantify the relative abundances of groups of sequences assimilable to plankton functional types in any metagenomics sample. It will help modelers defining realistic sets of traits as input to their models, and offer them new ways to validate models outputs using sequence relative abundance.

Session 5: Traits, Networks and Ecosystem Function



Øyvind Fiksen

Nadia Fouzai, Anders F Opdal, Christian Jørgensen

Dying from the lesser of three evils - facilitation and non-consumptive effects emerge in a model with multiple predators

Prey modify their behaviour to avoid predation, but dilemmas arise when predators vary in hunting style. Behaviours that successfully evade one predator may reduce foraging or facilitate exposure to another predator, forcing the prey to choose the lesser of two evils. Theory therefore separates between direct (or consumptive) effects of a predator and all the indirect consequences (or non-consumptive and trait-mediated indirect effects) the predator incurs. We model optimal behaviour of Atlantic cod Gadus morhua larvae in a water column, and find the minimal vulnerability to three groups of predators with different hunting modes. The predators are: i) ambush predators that sit-and-wait for approaching fish larvae; ii) cruising invertebrates that eat larvae in their path; and iii) fish which are visually hunting predators. We use a state-dependent model that finds optimal behaviours (vertical position and swimming speed) under any given exposure to the three distinct modes of predation. We then vary abundance of each predator and quantify direct and indirect effects of predation. The nature and strength of direct and indirect effects varied with predator type and abundance. Larvae escaped about half the mortality from fish by swimming deeper to avoid light, but their activity level and cumulative predation from ambush predators increased. When ambush invertebrates dominated, it was optimal to be less active but in more lit habitats, and predation from fish increased. Against cruising predators there was no remedy. In all cases, the shift in behaviour allowed growth to remain almost the same, while total predation were cut by one third. In early life stages with high and size-dependent mortality rates, growth rate can be a poor measure of the importance of behavioural strategies.

Session B: Food-webs and Trophic Interactions



Christopher Follett

Matthew J. Church, Stephanie Dutkiewicz and Michael J. Follows

Geometric Niche Partitioning of Nitrogen-Fixers in the Sea

Nitrogen fixing organisms play a key role in alleviating nitrogen limitation and stimulating new production in oligotrophic regions of the global ocean. Shifts in the elemental ratio of resource supply help explain the biogeography of nitrogen fixation, but the factors which control the functional class of nitrogen fixer (Diatom-Diazotroph Associations, Trichodesmium, UCYN-A, Crocosphaera) remain poorly understood. Focusing on the generation, diffusion and reduction of oxygen, we use the trait of cell size to derive a cap on the growth efficiency of multi-cellular, nitrogen fixing, consortia. We find that under certain conditions, this maximum efficiency depends entirely on the relative sizes and locations of fixing and non-fixing cells. This geometric theory correctly predicts the temporal and spatial niche partitioning between UCYN-A and Crocosphaera as demonstrated by 1 years of monthly nifH gene abundance data at Station ALOHA, an oligotrophic time series site in the oligotrophic Pacific Ocean. We further explain how this geometric efficiency factor could be straightforwardly encoded in computational, trait-based, models. When combined with previous work, this theory provides a blueprint for understanding the unique size structuring of nitrogen fixing consortia and their spatial-temporal structuring in the oligotrophic sea.

Session C: Multifarious lifestyles of marine microbes



Bethany Fowler

M.G. Neubert, K.R. Hunter-Cevera, A.R. Solow and H.M. Sosik

One Million Matrices: Size-structured modeling reveals in situ phytoplankton dynamics.

The picoeukaryotes are an abundant and diverse group of marine photosynthetic plankton. Understanding their population dynamics is key to understanding the role they play in the marine food web and in global biogeochemical cycling. Phytoplankton vital rates are difficult to quantify in situ due to their large population sizes, short generation times, and high mortality from viral lysis and zooplankton grazing. Building from the work of Sosik et al. (23), we fit a matrix population model to a 14-year time series of observations of individual cell traits, including size and pigmentation. Using the model, we are able to 1) identify apparent populations within the picoeukaryote assemblage, 2) estimate rates of cell division and loss and 3) investigate how those rates change over time. We find that the picoeukaryotes at Martha's Vineyard Coastal Observatory follow a strong seasonal cycle, with division rates ranging from an average of .1 /day in January to 2.1 /day in August. Division and loss rates are seen to be closely coupled throughout the year and to increase with increasing sea surface temperature in the spring. Over the 24-hour cycle, loss rates are not constant, and our analysis suggests that the picoeukaryotes may be preferentially grazed or subject to viral lysis during daylight hours. This work demonstrates that our population model can be usefully applied to heterogeneous phytoplankton groups and can be a powerful tool for studying their ecology in a natural system.

Poster Session 2 on Tuesday at 17.30.


Ursula Gaedke

Elias Ehrlich, Ruben Ceulemans, Toni Klauschies, Christian Guill

The role of trade-offs and mutual trait adaptation across three trophic levels: Evidence from a natural plankton food web and simulation models

Functionally diverse, multi-trophic communities can adapt to altered environmental conditions. This may strongly feedback to their trait diversity and population dynamics in which trait changes on one trophic level can cascade towards the others. Theory predicts that the shape of trade-offs between traits crucially affects these trait dynamics, but field evidence is rare. The talk will cover three main aspects: (1.) We show how the shape of a defense-growth trade-off in phytoplankton governs seasonal trait dynamics using high-frequency, long-term measurements from Lake Constance. We observed a concave trade-off curve and a dominance of relatively fast-growing species with intermediate defense levels . The pronounced seasonal changes in selective forces were clearly reflected by changes in the trait distributions. By combining data and modelling, we show that low fitness differences can promote maintenance of phytoplankton trait variation along the trade-off curve. (2.) We demonstrate how such temporal trait changes alter the ecological dynamics across the first three trophic levels in the food web of Lake Constance. Phytoplankton and herbivorous and carnivorous zooplankton all exhibited mutually interacting biomass-trait feedbacks. The observed temporal order of trait changes between herbivores and primary producers was counterintuitive and only explicable by accounting for trait changes in the carnivores. (3.) To generalize our understanding of trait variation in tritrophic systems, we modelled how adding gradually trait variation to each trophic level influences population and community dynamics. We show that trait variation enhances resource use efficiency, productivity, stability, and resilience of the entire food web. Examining the phase relationships between different species both across and within trophic levels revealed how top-down or bottom-up control affects biomass production, and how compensatory dynamical patterns between functionally different species affect community variability.

Session C: Multifarious lifestyles of marine microbes



Irene Gallego Nogales

Anita Narwani

Phytoplankton Trait Evolution under Resource Limitation: An In-Lake Mesocosm Experiment

The high genotypic diversity and turnover observed over space and time in marine and freshwater phytoplankton populations suggests that rapid evolution occurs in natural phytoplankton populations, but the role of competition in drivingevolutionary change in these populations is unknown. While lab studies have considerably advanced our understanding of eco-evolutionary dynamics, they have some limitations as most experiments use only single species or very simplified “communities”, neglecting any effect of complex community structures. Given these limitations, we aim to investigate adaptation to competition in natural phytoplankton populations. Using in situ lake mesocosm experiments in Lake Greifensee (Switzerland), we will manipulate the identity of the primary limiting resource (N, P or light) and track changes in community structure, species traits, and population-level genotypic diversity. We will also testwhether changes in community structure occur due to changes in individual species’ traits or due to changes in the identity and associated traits of dominant species. The contribution of evolution to trait change will be quantified by measuring associations between the degree of trait change within a certain population and changes in population genotypic structure.

Poster Session 1 on Monday at 17.30.


Stephanie Green

Natasha A. Hardy, Larry B. Crowder

A traits-based framework to account for the influence of predator-prey interactions on species distribution under global change

The distribution and abundance of species across our globe is changing at an unprecedented rate due to human-mediated processes such as climate change, biological invasion, and exploitation-mediated population decline and recovery. As a result of these global change forces, novel combinations of species are now co-occurring—and interacting—for the first time. How will the structure and function of ecosystems, and the socio-economic benefits they provide, respond to changing species composition? Reviewing studies of species’ range and abundance change reveals that much of the effort thus far has focused on the role traits play in conferring information about abiotic requirements and dispersibility in response to environmental change. However, a key challenge for forecasting species distribution under global change is a lack of general principles from which to predict the strength of novel species interactions as they emerge within re-assembled systems. Here we synthesize evidence for the pervasive role behavioural and morphological traits play—independent from species identity—in determining the strength of predator-prey interactions, which structure the flow of energy through communities. We use this synthesis to develop a framework in which foraging interactions occur between species based on their trait typologies, rather than taxonomic identity. Such an approach facilitates general mechanistic predictions can be made about the interaction strengths between species that do not co-occur now, but are likely to in future. We outline ecosystem characteristics for which a predator-prey traits approach could greatly aid in forecasting species redistribution, identify data needs and analyses for testing and validating the approach, and illustrate its application to two marine case studies in the tropical Western Atlantic and temperate Eastern Pacific in which the ecological consequences of rapid predator redistribution are understood through the application of a trophic traits framework.

Session E: Biodiversity and ecosystem function



Maria Grigoratou

Fanny M. Monteiro, Jamie Wilson, Andy Ridgwell and Daniela N. Schmidt

Exploring planktonic foraminifera ecology in present and future climate conditions using a size-structured ecosystem global ocean model

Planktonic foraminifera are main zooplankton calcifiers, contributing to 23-56% of the modern total pelagic carbonate production. Adult species are categorized into two groups; herbivorous non-spinose and carnivorous spinose. Here we developed the first global trait-based ecosystem model of planktonic foraminifera, ForamEcoGEnIE, to investigate in combination with observations, the ecology and biogeography of non-spinose adults in present and future climate scenarios. The trait-based model accounts for the traits of calcification, size and feeding behaviour. Our model suggests an energy penalty of calcification equivalent to a 10% reduction of the growth rate, and a benefit of calcification represented by a 30% reduction in background mortality. This would indicate a potential important role of the shell to protection from pathogens. The model captures the observed seasonal and annual distribution of non-spinose species with maximum abundance in the subpolar, temperate and upwelling regions and minimum in subtropics and tropics. We find that global warming has a strong impact on planktonic foraminifera with an overall reduction of their stocks which potentially can be associated with a major decrease in the ocean CaCO3 production.

Poster Session 2 on Tuesday at 17.30.


Josephine Grønning

Thomas Kiørboe

Grazer induction of shell-thickening in diatoms

When exposed to predators, many phytoplankton species increase their defense; e.g. toxin production, reduction of chain length, bioluminescence, etc. The silicified cell walls of diatoms are believed to serve as a defense towards grazing and experiments have shown that thin-shelled cells are grazed less upon by mesozooplankton than thick-shelled ones. Moreover, one experiment has indicated, that diatoms exposed to chemical cues released from herbivores become significantly more silicified than ones not exposed. To investigate this inducibility of silicification in diatoms, we exposed 7 different diatom species to waterborne copepod cues in induction experiments. We measured the population growth rate and silica content per cell volume and found no difference in those two parameters between induced and non-induced cells. Hence we found no indication that any of the tested diatom species can upregulate their defense in the presence of grazers. All experiments of this study were conducted under non-limited conditions with respect to temperature, light and nutrients. Therefore, future experiments should test the inducibility of silicification of diatoms cells under resource limited conditions.

Poster Session 2 on Tuesday at 17.30.


Lionel Guidi

High-throughput sequencing and imaging: New avenues for trait based modeling?

Session D: Traits, Networks and Ecosystem Function



Jeneen Hadj-Hammou

Timothy McClanahan, David Mouillot and Nicholas Graham

Comparing taxonomic and functional changes of coral reef fish over time in protected areas

Coral reef fish are increasingly confronted with a range of environmental disturbances. However, they also contribute to crucial ecosystem processes and services in a number of ways. Functional traits and corresponding metrics of functional diversity provide a mechanistic link between species and their responses to disturbances and effects on processes. They provide different insights into how future ecosystems might function and deliver ecosystem services to the people dependent on them. A long-term chronosequence dataset spanning 4 years of fish and benthic monitoring data from Kenyan coral reef Marine Protected Areas has previously been analysed using taxonomic-based time-series approaches. We apply a trait-based approach to the same dataset to determine what further insights traits might provide to understanding changes in ecosystem functioning over time. Traits identified in a previous systematic review as both response and effect traits were used to build a functional space. General Additive Models were used to assess the changes in individual traits and functional diversity over time. Results indicate an increase in functional diversity over time with protection and the immediate insignificant impact of climate change is demonstrated. Increasing body size in protected areas over time contributed to rates of increase of key feeding groups of fish. Such shifts in the functional space of coral reef fish over time will likely have an impact on key ecosystem processes such as herbivory and predation, as such processes are directly dependent on traits including size and diet. By applying a response and effect trait framework to this dataset, the impacts of disturbances and management on ecosystem functioning is illustrated.

Poster Session 1 on Monday at 17.30.


George Hagstrom

Trait-Based Models of Phytoplankton Stoichiometry: Nutrient Uptake, Environmental Drivers, and Genomics.

Trait-Based models have helped reveal how environmental conditions control phytoplankton elemental stoichiometry. Despite these successes, limitations to our data and our understanding of physiology have prevented us from modeling the trade-offs between different nutrient uptake traits, the effect of limitation by different nutrients on elemental stoichiometry, and from distinguishing the effects of environmental co-variates like temperature and the nutrients. Here we develop a new trait-based model of phytoplankton stoichiometry which captures investments in the uptake of different types of N, P, and Fe, and thus predicts the effects of different types of nutrient limitation on phytoplankton stoichiometry. We parametrize this model in a Bayesian framework using a new, high quality dataset and show how the resulting model revises our understanding about the roles of N, P, Fe, and temperature in the regulation of stoichiometry. Lastly, we discuss how this framework can be extended to incorporate 'omics data derived from both field work and experiments.

Session D: Traits, Networks and Ecosystem Function



Natasha Hardy

Will Figueira, Elliott Hazen, Larry B. Crowder, Stephanie J. Green

Trait-based frameworks for understanding predator-prey interactions along gradients of ecological change from the coast to the open ocean

Species distributions and interactions are rapidly changing in response to increasing human-induced drivers of environmental change, including overexploitation of resources and climate change. Novel combinations of species are giving rise to new trophic dynamics within communities, and large-scale changes to the structure and function of altered ecosystems. We examine trends in marine predator-prey interactions in a series of case studies of changes in predator population and distribution from across the Pacific Ocean: the rapid recovery of large coastal predators following federal protection of previously harvested species; and, large-scale spatial and temporal shifts in the distribution of large oceanic predators in response to warming and increased variability in oceanographic habitats. We illustrate the relevance of a trait-based framework for understanding shifts in trophic interactions between predators and complex prey communities in changing ecosystems. We use a fourth-corner modelling approach to analyzing statistical relationships between multiple arrays of data and to assessing the power of trait-based analyses for predicting changing ecological interactions. Analytical tools that incorporate predictive traits informing the predation process will add salient and cost-effective information to existing species distribution and ecosystem-based models, such as identifying key groups of prey that are being exploited by predators in changing ecosystems, or for example in identifying spatio-temporal shifts in ecological interactions. This information can be communicated to and applied by managers, responsible for achieving physical objectives for conservation and mitigation of human impacts with finite resource budgets. As climate change is shifting fisheries resources across jurisdictional boundaries, our team hopes to foster international collaborations on predator diet data to produce predictive tools for predator-prey interactions across gradients of environmental change.

Poster Session 2 on Tuesday at 17.30.


Chris Hill

Oliver Jahn, Steph Dutkiewicz, Zhen Wu, Greg Britten, Ali Ramadhan

Sub-mesoscale induced variability in trait based ecosystem models

This talk will look at a suite of emerging activities aimed at examining how state of the art trait based models based on the MIT Darwin ecosystem code and algorithms respond to physical ocean model variability at spatial scales down to below 1 kilometer and at temporary scales that capture the diel cycle. The talk will describe some initial results from a family of models and will look at ways we are trying to synthesize the rather complex systems into big picture insights. It will discuss current dilemmas on how to appropriately interpret classical ecosystem statistical methods such as Bray-Curtis diversity and Shannon index in the context of a moving, Lagrangian frame of reference with potentially vigorous physical mixing present. 

Poster Session 1 on Monday at 17.30.


Helmut Hillebrand

Charlotte Kunze

Functional traits explaining species-specific and community wide responses to disturbances

Resistance to and recovery from pulse disturbances are two dimensions of ecological stability that have been addressed in a broad range of global change experiments. Here, we use this existing literature in a meta-analyse to ask i) how much functional and compositional stability are connected to each and ii) whether each form of stability is related to (the same) traits of component species. We use a recently published method to decompose responses to pulse disturbances and apply it to a cross-system database currently consisting of several hundred experiments. We find strong correlations between different aspects of stability, which are linked to differences in experimental setup and organisms traits.

Poster Session 1 on Monday at 17.30.


Nils H. Hintz

Poelman Y., Wacker A., Striebel M.

Phytoplankton response to changing light spectrum

Light is considered as key driver of energy and material flow on earth. In aquatic systems the light availability for photosynthetic organisms rapidly decreases with water depth and thus limits phytoplankton growth and primary production. Besides the general decrease in light intensity, the spectral composition of the available light also changes. Different findings proof that light cannot only be considered as a single resource for phytoplankton but as a multitude of resources in terms of spectral quality. To utilize different parts of the light spectrum, phytoplankton taxa possess diverse accessory pigments in addition to chlorophyll a in specific combinations and quantities. Therefore, different phytoplankton species with specific light-utilization traits can harvest the available light complementary, which enables coexistence and a higher diversity. To estimate effects of different spectral qualities on single phytoplankton strains as well as a natural North Sea community three different light colors (red, blue, green) as well as the full control spectrum (white) at the same irradiance level were tested. We conducted small (up to 200 mL) and large-scale (600 L mesocosms) experiments and monitored species composition-, pigment- and nutrient (stoichiometry) analysis. We expected the monocultures to respond species-specifically in both, growth rate and changes in pigment composition. For example, cyanobacteria performed better at green light than diatom or green algae and exhibited a relative increase in pigments absorbing the green part of the light spectrum. Within the natural communities we expected pigment composition to change prior to changes in species composition. Our results indicate responses of the phytoplankton communities to light quality on the short- and long-term scale. The specific utilization of the light spectrum enables coexistence of species under the full light spectrum but competitive exclusion occurred under constrained light spectrum conditions. This is important in understanding phytoplankton biodiversity under changing light conditions.

Poster Session 2 on Tuesday at 17.30.


Pei-Chi Ho

Chun-Wei Chang, Fuh-Kwo Shiah, Pei-Ling Wang, Chih-hao Hsieh, Ken H. Andersen

Body size, light intensity and nutrient supply determine plankton stoichiometry in mixotrophic plankton food webs

Trophic strategy determines stoichiometry of plankton. In general, heterotrophic zooplankton and mixotrophs have lower and more homeostatic C:N and C:P ratios than photoautotrophic phytoplankton. Body size may be the key trait influencing the development of trophic strategy and thus plankton stoichiometry: resource (light, inorganic nutrients, and food particles) uptake rates depend on body size. Here, we measured plankton size-fractionated C:N ratios under different intensities of light and nutrient supply in subtropical freshwater and marine systems. Furthermore, to determine the biological mechanisms that critically shape plankton trophic strategy and stoichiometry, we constructed a plankton food web model in which the affinities to light, inorganic N nutrient and food particles of an organism allometrically scale with its body size. We found a unimodal body size-C:N ratio pattern with a maximum C:N ratio at 44-74 μm and 5-14 μm diameter in freshwater and marine systems. Moreover, the change of C:N ratio with light and inorganic nutrient is the largest at 44-74 μm freshwater phytoplankton size class. These patterns are reproduced by our model simulation: C:N ratio of photoautotrophs (≤ 51μm) increases with body size, and C:N ratios of mixotrophs (≥ 71μm) decrease with increasing heterotrophy due to low photoautotrophic C gain and high respirational C loss. We also found that C:N ratio change with light and inorganic nutrient is the largest at size class 51 μm, corresponding to the observations in the freshwater system. Based on our field observations and simulation, size-dependent trophic strategy and respiration are critical to plankton stoichiometry.

Poster Session 2 on Tuesday at 17.30.


Rucha Karkarey

Mahesh Sankaran, Mayuresh Gangal, Elrika D'souza, Teresa Alcoverro and Rohan Arthur

Habitat degradation over a decadal scale drives functional shifts in mesopredatory coral reef fish assemblages

Climate-change is rapidly degrading the structural complexity of ecosystems which is unraveling habitat-associated species assemblages. Understanding how changes in biodiversity is impacting ecosystem function is an urgent imperative. On coral reefs, benthic mesopredatory fish represent a guild of closely competing species, with widely divergent life-history traits and susceptibility to habitat degradation. Mesopredators can play critical functional roles on reefs by either directly consuming prey or by modifying prey behaviours, yet few studies have explored how changing mesopredator assemblages are likely to affect ecosystem function. We tracked changes in reef structural complexity and mesopredator fish assemblages since 1998, in the lightly fished Lakshadweep archipelago, Indian Ocean. Based on our long-term data from twelve permanent monitoring sites across three islands, encompassing three mass-bleaching disturbances (1998, 21, 216), we studied how a loss of habitat structural complexity impacts the taxonomic and functional diversity of mesopredators (12 species, 15 families). Reefs that remained structurally intact since 1998 declined rapidly after 21. In these reefs, we found no significant changes in mesopredator biomass, density and richness but a significant shift in species composition since 21. We used five commonly measured fish traits (maximum body size, diet, mobility, water-column position and foraging strategy) to functionally classify the species. These traits are proxies for two important mesopredator functional roles: food acquisition and locomotion, that are likely impacted by habitat structure. Functional diversity of mesopredators was quantified using four indices - richness, evenness, divergence and specialization. Most interestingly, we found a two-fold increase in ‘functional divergence’ and a three-fold increase in ‘functional specialization’ since 21. This functional shift can be attributed to an increase in the abundance of species with a particular combination of traits that appear to be favoured in structurally degraded reefs (ie., large body size, high mobility, omnivorous diets, flexible foraging modes and bentho-pelagic habits). Shifts in mesopredator assemblages from small, site-attached, ambush predators to large, widely-ranging, roving predators likely represent major shifts in predation and associated ecosystem function which need to be addressed further.

Poster Session 1 on Monday at 17.30.


Kasia Kenitz

Eric C. Orenstein, Paul L.D. Roberts, Peter J.S. Franks, Jules S. Jaffe, Melissa Carter, Andrew D. Barton

Environmental and ecological drivers of variability in chain-forming marine diatoms

Colony formation is common among marine phytoplankton, yet little is known about abundance patterns and fitness of colonies relative to competing taxa. Particularly, formation of chain-like colonies in diatoms has important implications for diatom growth, survival and carbon transfer. We used supervised machine learning to distinguish diatom chains from 6 million images of suspended particles and organisms taken by the Scrips Plankton Camera System, an underwater microscope which images particles in situ without mechanically disturbing them. Using a novel, high-resolution time series generated by automated classification of underwater images, and observations using traditional microscopy, we identify environmental drivers underlying temporal variability of chain-forming and single-cell diatoms off the coast in Southern California Bight. Lower abundances of diatom chains were recorded during anomalously warm and more stratified period, compared with the cooler part of the record. Diatom blooms were dominated by chain-formers, whereas single-cell diatoms prevailed during low-biomass conditions. We hypothesize that nutrient-limited conditions are dominated by better nutrient competitors, whereas species best adapted to escape predation from microzooplankton form blooms. Our results show that single-cell and chain-forming diatoms have contrasting ecological dynamics driven by both bottom-up and top-down ecological processes.

Session C: Multifarious lifestyles of marine microbes



Christopher Klausmeier

Thomas Koffel, Kaito Umemura, Elena Litchman

Trait-based approaches to species abundance distributions

Species abundance distributions (SADs) are an intermediate-level description of the diversity in a community. Studied by ecologists for over a hundred years, SADs are seen as an example of a general law in ecological communities: few species are common while most are rare. More precise descriptions have been suggested, such as the lognormal distribution, but appreciable variation exists. Over 25 theories have been put forward to explain SADs, but most are unconnected to population dynamics. Here we present a trait-based theory of SADs in open systems subject to immigration. We find that these models readily generate realistic SADs where species abundance varies over orders of magnitude, but no universal distribution emerges. Instead, the details of the SAD depend on local selective forces and regional patterns of abundance. Species can be dichotomized as "core species" that would persist in the absence of immigration and "satellite species" that require immigration for persistence. Core species dominate ecosystem functioning, but satellite species provide adaptive capacity in changing environments.

Poster Session 1 on Monday at 17.30.


Carla Kruk

C. Piccini, G. Beamud, L. Sampognaro, F. Lepillanc, A.M. Segura

Predictable species coexistence mediated by functional equivalence

Morphological traits are useful to investigate phytoplankton dynamics and community assembly both in freshwater and marine environments. Historical divergence in the approaches requires an effort to synthesize paradigms and reach an unified framework. Here, we use a morphology-based functional groups (MBFG) approach and show that community structure and coexistence of species depends on organisms traits related to ecological and functional aptitude. Our hypothesis is that species with similar functional traits, organized in functional groups have similar niche. Within each functional group, species are relatively equivalent and therefore functionally interchangeable. We predict successful invaders will be species of the same functional group with equal or higher fitness than resident species.To evaluate these hypothesis we analyzed the temporal succession of phytoplankton species retrieved from several natural communities (species pool from lakes in a subtropical region) under different nutrient and temperature levels emulating subtropical shallow oligotrophic and eutrophic lakes in winter and summer.Total phytoplankton and particularly large filamentous potentially toxic cyanobacteria, with high surface/volume ratios, developed most in high nutrient and temperature treatments. However, different species with similar morphological traits alternatively dominated or coexisted, presenting similar fitness which was estimated as R* using individual morphological traits and literature reviewed scaling relationships. In experiments defined by same environmental conditions (high resources and temperature), were MBFG III dominated, the invasion of the cyanobacteria Cylindrospermopsis raciborskii (belonging to MBFG III) was successful, but its relative abundance varied among replicates. Community metagenomic analysis evidenced that despite the observed changes in specific composition of both autotrophic and heterotrophic microbial communities, main functions remained similar among treatments. This suggests that MBFG do indeed contain functionally equivalent and interchangeable species. In line with the emergent neutrality theory, this means that selection from the species pool is acting on functional groups and the identity of a particular species within such groups could be essentially a stochastic process. The application of trait-based approaches to summarize the niche and estimate fitness changes along environmental gradients was useful to evaluate underlying mechanisms and predict microbial invasion success. Comparing present framework to those used in the marine realm is straightforward and could provide benchmarks to find gaps and opportunities to advance into a comprehensive trait-based aquatic ecology.

Poster Session 1 on Monday at 17.30.


Suzana Leles

Luca Polimene, Jorn Bruggeman, Jeremy Blackford, Stefano Ciavatta, Aditee Mitra, Kevin John Flynn

Mixotrophy and the succession of plankton trophic strategies within ecosystem models

Carbon acquisition among plankton is usually assigned to one of the two trophic strategies: autotrophy or heterotrophy. In reality, many plankton combine both strategies; these are called mixotrophs. Mixotrophy is widespread among protist plankton displaying diverse functional forms across a wide range of sizes. Mixotrophs are distinguished between those with innate capacity for photosynthesis (constitutive mixotrophs, CMs) and those which acquire phototrophy from their prey (non-constitutive mixotrophs, NCMs). However, little is known about the niches of different mixotrophs and how they may affect biogeochemistry and trophodynamics in marine ecosystems. Here we explored these dynamics using a plankton food web model describing diverse forms of mixotrophs. Simulations were performed of ecosystems limited by different light and nutrient regimes. Our results show that cell size is an important determinant of success for CMs; smaller cells dominate in nutrient poor conditions and larger cells dominate in light-limited environments. The specificity of the prey from which NCMs acquire phototrophy affects their success, with forms able to exploit diverse prey dominating under nutrient limitation. In turn, strict auto- and hetero- trophic competitors increased in relative importance in the transition from nutrient to light limitation, consistent with observed biomass ratios. Overall, we show that mixotrophy has the potential to impact nutrient availability, mass transfer to higher trophic levels and the microbial loop, radically changing our understanding of plankton food webs.

Session C: Multifarious lifestyles of marine microbes



Aleksandra Lewandowska

N. Aberle

Does initial diversity influence phytoplankton response to environmental change?

Numerous studies in different systems have shown that local biodiversity and the resistance of ecosystems to environmental perturbations are positively linked. Here we argue that this relationship will strongly depend on the initial community assembly and the niche overlap between the local set of species. We performed experiments with natural marine phytoplankton (control and heat stressed) in five different locations to test the effects of changing salinity on ecosystem productivity. More stable communities that were better adapted to the local conditions were more resistant to salinity change. This effect was independent on the number of species, but influenced by the identity of dominant taxa and their sensitivity to salinity fluctuations. Our study emphasizes that the response of local ecosystem productivity to environmental change will not simply depend on local species richness, but on the entire set of interactions within communities.

Session E: Biodiversity and ecosystem function



Christian Lindemann

Scaling buoyancy regulation in marine diatoms

Diatoms are an important part in the marine ecosystem, contributing as much as 4% to the marine carbon uptake. Due to the absence of flagellum or cilia they are often modeled as passively sinking particles, where the sinking velocity is determined by the cell size. However, many diatom species exhibit variable sinking rates not only with changes in cell size, but driven by active buoyancy regulation through changes in cell density linked to cell physiology and growth condition. Several hypothesis regarding the dominate factor controlling the variations in cell density have been suggested; with changes in vacuole density and vacuole size, as well as the macromolecular composition (carbohydrates, lipids, proteins and silicate), being the most dominate ones. This study presents a model linking allometric-scaling and physiological buoyancy control in marine diatoms. This mechanistic trait-based model accounts for variable vacuole proportion and vacuole density as well as changes in macromolecular composition, as a function of cell size and growth condition. The results show that both, the macromolecular composition and vacuole density play an important role in controlling cell density, with shifting dominance depending on cell size and growth. These findings are supported by literature values and have not only important implications for the biological understanding of the persistence of diatom cell in the mixed layer, but also unify several hypothesis regarding the dominate driver in diatom buoyancy regulation. In addition to the full model, a simplified version of the model, suitable for the implementation in larger ecosystem models, is presented.

Poster Session 2 on Tuesday at 17.30.


Elena Litchman

Katabuchi, Masatoshi; Umemura, Kaito; Koffel Thomas; Klausmeier, Christopher

Traits and immigration determine species abundance distributions in experimental phytoplankton communities

Understanding what determines species abundance distributions (SADs) should provide insights into processes structuring ecological communities. Here we test a novel theory that combines niche-based processes with immigration using experimental phytoplankton communities. We assembled multispecies communities and grew them at three different temperatures crossed with three different levels of immigration. The resulting SAD shapes depended on level of immigration and species abundances correlated with how well their optimum temperatures for growth matched the treatment temperature. Species with the Topt close to the experimental temperature had the highest abundance, species with the mismatched thermal trait were maintained in the community through immigration. The study demonstrates that the niche-based processes and immigration can produce realistic SADs and that experimental phytoplankton communities provide an effective way to test new theories of community assembly.

Session E: Biodiversity and ecosystem function



Diana Lopez

Amy Freestone

Predation pressure increases functional diversity and changes functional structure of marine communities at low latitudes

The intensity of biotic interactions is hypothesized to increase towards the equator. Predation can have a stronger effect on prey composition, biomass and taxonomic diversity in tropical regions compared to higher latitudes. Whether predation shapes patterns of functional diversity and structure of prey communities, however, has not been explored across a latitudinal gradient. Theory suggests consumer pressure increases functional diversity by reducing competitive dominance and promoting trait heterogeneity. Therefore, we hypothesize that predation will increase functional diversity and shape functional structure of prey communities at lower latitudes. In contrast, we hypothesize that predation will have a weaker effect at higher latitudes. We further hypothesize that evolutionary history of co-occurrence can shape biotic interactions, and novel interactions among non-coevolved species may lead to stronger interaction outcomes if prey lack adequate defenses to native predators. To test these hypotheses, we conducted a large-scale predator exclusion experiment on nearshore sessile marine invertebrate communities across 12 sites in four regions of the Pacific coast: Alaska, California, Mexico, and Panama. Prey communities developed under ambient or reduced predation pressure at each site. We then assessed the effect of predation on functional divergence (FDiv) of fourteen traits and community weighted means (CWM) of all traits that define functional space in terms of palatability, competition, and survival. To test for differential effects of predation on native and novel interactions, we also built the indices separately for the native and introduced components of each prey community. Overall, predation increased functional diversity and shaped functional structure more strongly for low latitude prey communities, but effects differed among native and non-native species. Specifically, predation increased FDiv of introduced species in Panama and native species in Mexico. Predation also influenced the CWM of introduced species and whole communities from Panama, native species from Mexico, and native species from Alaska, with the strongest effect occurring in the tropics. Key traits that drive these patterns are being identified and may elucidate trait mismatches between introduced prey and local predators. Therefore, predation had a stronger influence on the trait distribution of prey communities at lower latitudes where biotic interactions are expected to be more intense, but trait responses can also hinge on evolutionary history of co-occurrence.

Poster Session 1 on Monday at 17.30.


Tom Lorimer

Francesco Pomati, Carlo Albert, Stuart Dennis, Marta Reyes, Christian Ebi

Revealing and exploiting the non-convexity of trait distributions

Trait distributions in multiple dimensions are used to make inferences about species niches or interactions. These distributions are often assumed to be convex, but in more than one dimension, the underlying nonlinear processes may break this assumption. Moreover, restricting analysis to one dimension (or treating dimensions as independent) can obscure potentially important higher-dimensional differences, thereby increasing the apparent "noise" in the system behaviour. To better understand and overcome these potential problems, we have developed novel graph-based measures for trait distribution non-convexity, and trait distribution proximity. These measures do not make assumptions about the intrinsic dimensionality or shape of the data. We will present these measures, as well as some results of their application to in situ plankton imaging data from a new dual-magnification automatic underwater microscope in a lake in Switzerland.

Poster Session 2 on Tuesday at 17.30.


Séverine Martini

Emile Faure, Floriane Larras, Aurélien Boye, Nicole Aberle, Lise Bacouillard, Beatrix Beisner, Lucie Bittner, Emmanuel Castella, Michael Danger, Olivier Gauthier, Lee Karp-Boss, Fabien Lombard, Frederic Maps, Lars Stemmann, Eric Thiebaut, Philippe Usseglio-Polatera, Meike Vogt, Martin Laviale, Sakina-Dorothée Ayata

Trait-based approaches: a common framework for freshwater and marine ecologists

Freshwater and marine ecologists face common challenges: to identify the general rules of the functioning of aquatic ecosystems and to develop a more predictive ecological understanding of them. However, they traditionally form two distinct scientific communities with little crossover between them. We argue that a common framework is needed to bridge communication gaps and foster knowledge sharing. This framework should transcend local specificities and taxonomy in order to provide a common ground and shareable tools to address common scientific challenges. Here, we advocate the use of trait-based approaches as a common language for freshwater and marine ecologists. We propose a unification of existing definitions and present a synthesis on traditional as well as recent and promising methods for the study of traits in aquatic organisms, including imaging, genomics, and numerical modeling. Finally, we highlight challenges and perspectives that are common for freshwater and marine ecosystems and for which trait-based approaches should foster opportunities for future research. By bridging the gap between freshwater and marine ecology, as well as between pelagic and benthic ecosystems, this framework provides a clear path forward in using traits-based approaches in aquatic ecology.

Poster Session 2 on Tuesday at 17.30.


Alizée Mauffrey

L. Cappelatti, J.N. Griffin

Traditional functional groups capture limited variation in the trait space of macroalgae

Macroalgal functional ecology rests on a tradition of classifying species into groups based on gross morphology or anatomy. However, applications of these traditional grouping approaches have yielded contradicting results across large sets of species and spatial scales, as they do not relate to ecological roles in consistent ways. Here we explore the use of multiple, directly measured functional traits to characterise ecologically-relevant variation, i.e., trait space, among macroalgae. We screened 96 British rocky-shore species for 12 qualitative and quantitative traits relating to competitive dominance and resource utilisation. We found all traits to be reliable at the species level, i.e., interspecific > intraspecific variability. Consistent with results from vascular plants, the first axis of ecological variability related mostly to resource utilisation, while competitive dominance laid separate. Traditional grouping methods poorly captured variation of individual traits or dispersion in multivariate trait space. We argue that macroalgae could eventually be placed along the extended primary producer spectrum that already encompasses many autotrophic organisms. We caution that traditional groups do not efficiently capture macroalgal variation, while emergent classifications or direct use of traits have the potential to better represent physiology and morphology and hence, to better explain the ecological role of macroalgae.

Poster Session 1 on Monday at 17.30.


Aurore Maureaud

K.H. Andersen, L. Zhang, M. Lindegren

Food web structure and species interactions reveal mechanisms underlying biodiversity-ecosystem functioning relationships

The relationship between biodiversity and ecosystem functioning has been extensively studied over the last three decades using experiments, theoretical models, and more recently observational data. While most studies focus on species richness effects on ecosystem functioning, a large degree of variation remain unexplained, highlighting that other factors besides species richness are needed to fully understand and predict differences and changes in ecosystem functioning. In this study, we use a trait-based food web model to investigate the role of food web structure on multiple ecosystem functions (e.g. biomass, production, productivity, and metabolism). We demonstrate that the relationship with species richness depends on the type of ecosystem function considered. Furthermore, we show that the level of ecosystem functions is determined by particular food web configurations, as well as the degree of species dominance. Dominance plays a major role in determining the level of biomass in the food web, occurring via species interactions and occupancy of the trait space. By manipulating the structure of the food web, we show that species using a wider niche space (generalist communities) result in more connected food webs compared to species with a narrow niches (specialist communities), and generally reach the same level of functioning with a fewer number of species. We show that a trait-based approach can help understanding ecosystem structure and functioning of marine food webs, and help building research hypothesis for field-based studies.

Poster Session 2 on Tuesday at 17.30.


Donna McCullough

B. Calfee, E. Zinser, D. Talmy

Modeling reactive oxygen species as a possible control in cyanobacteria community selection

Reactive oxygen species (ROS) are ubiquitous in the ocean and are detrimental to all cell types. Cells that carry enzymes involved in ROS detoxification have costs associated with enzyme maintenance and repair, and lower diffusive nutrient uptake due to larger cell volume. By considering trade-offs between efficient nutrient acquisition and maintaining ROS detoxifiers, we plan to use resource competition theory to assess how nutrient supply and ROS concentration gradients exert control on the selection of microbial communities. Mathematical models will be developed and parameterized with an experimental system allowing competitive and mutualistic interactions among Prochlorococcus (Pro), Synechococcus (Syn), and heterotrophic bacteria. Having previously demonstrated its ability to elucidate the differences that cell size and ROS detoxification can make on a community structure, this system is a good fit for the empirical testing we have planned. Our models will be used to ask how protection against ROS and nutrient competition drive large-scale distributions of Pro, Syn, and heterotrophic bacteria. Our modeling will provide a quantitative base to understand ROS production and detoxification, and the impact of these dynamics on marine primary productivity.

Poster Session 1 on Monday at 17.30.


Mark Miller

Maria Beger

Stability and persistence of reef fish functional groups

Distance-based measures of functional diversity are sensitive to input parameters and methodology. The identification of functional groups is particularly challenging, and is conducted either using a-priori knowledge or clustering algorithms. Differing communities of species, sets of traits, and clustering algorithms have been used to define fish functional groups, however little attention has been paid to whether similar clusters emerge across studies. Here, we use a detailed and accurate fish trait database, and well-sampled reef communities to identify and compare functional groups emerging from tropical Japan and Australia. We use novel metrics to compare the identity of functional groups in trait space, and determine which species are ‘core’ to each group and which species ‘jump’ between groups. We also evaluate the impact of sampling strategies and trait selection on resultant functional group stability and persistence. We explore our results in the context of reef ecosystem functioning, and present a best-practice approach to identifying fish functional groups.

Poster Session 2 on Tuesday at 17.30.


Holly Moeller

Michael G. Neubert, Matthew D. Johnson

Trait-based evolution of acquired phototrophs: New models for complex endosymbiosis

Among an organism's most fundamental traits are those that govern its metabolic capacity, because metabolism constrains how species gather resources through interactions with abiotic and biotic elements of their environments. Yet metabolic capacity may also be surprisingly plastic: organisms can gain access to novel forms of metabolism through interactions with other species. For example, kleptoplastidic (chloroplast-stealing) acquired phototrophs retain photosynthetic machinery from other lineages, transforming their metabolism from heterotrophic to mixotrophic (combining photosynthesis and heterotrophy). These lineages represent hypothetical evolutionary intermediaries along the endosymbiosis pathway that has allowed numerous eukaryotic lineages to permanently incorporate chloroplasts. In this talk, we use a combination of empirical and mathematical models to examine the traits that govern this evolutionary pathway. We focus on two main classes of traits: those that govern an organism's ability to retain and replicate plastids. We use adaptive dynamics to map the fitness landscapes that may drive selection for acquired, and permanent, phototrophy. We then test the model's predictions using a genus of marine ciliates, Mesodinium, whose members span a gradient of reliance on stolen chloroplasts. This empirical model system allows us to identify traits that co-vary with photosynthetic capacity, in order to identify mechanistic tradeoffs that constrain evolutionary capacity. Combining these two approaches reveals the environmental and trait space that favors the evolution of different metabolic strategies.

Session C: Multifarious lifestyles of marine microbes



Fanny Monteiro

Jamie Wilson, Joost de Vries, Glen Wheeler

Investigating the effect of size and life cycle on coccolithophore ecology and ocean carbon cycling in a trait-based global ocean model

Coccolithophores are a key group of marine phytoplankton contributing to the global oceanic production of calcium carbonate via the production of coccoliths. While most studies rely on the small calcifying Emiliania huxleyi, coccolithophores have a large diversity in size, shape and ecology with about 2 species present in the modern ocean and a bi-stage life cycle. For instance, within the dominant placolith-bearing species (e.g., E. huxleyi, Calcidiscus leptoporus, Coccolithus pelagicus), cell diameter ranges from 4 to 2 µm and PIC:POC ratio from .2 to 3. Coccolithophores have also 2 main life stages, haploid and diploid phases, in which they change cell size and coccolith properties. This highlights the need to include different traits and trade-offs in coccolithophore studies. Here we use a trait-based model of the global ocean to explore the effect of size and life cycle on the distribution, diversity and both primary and CaCO3 production of the placolith-bearing coccolithophores. The model combines the trait-based Darwin ecosystem model which accounts for a diverse and adapted population of plankton, with the Earth System model of intermediate complexity cGENIE, which is capable of running large ensembles. We present here on-going results on how to model size diversity and life cycle of coccolithophores, as well as show sensitivity experiments on the effect of these key traits on coccolithophore ecology and ocean carbon cycling.

Poster Session 2 on Tuesday at 17.30.


Javier Murillo

Benjamin Weigel, Marieve Bouchard Marmen, Ellen Kenchington

Marine benthic functional diversity on the Flemish Cap (Northwest Atlantic)

The functional diversity of trawl-caught benthic invertebrate communities was described for the Flemish Cap, a plateau of ~2 km radius in the northwest Atlantic. Through the use of Hierarchical Modelling of Species Communities, a statistical framework for analysis of multivariate data, we have identified response-traits to the environment and evaluated the influence of such traits on the community assembly processes. Although the amount of variation explained by the species’ responses to the covariates mediated by the functional traits was relatively high, the relationships between particular trait categories and the covariates were weak and only pointed out broad trends. Assemblages from the top of the Bank (<5 m depth) were characterized in terms of biomass by small- and medium-sized species with short lifespans, whereas large species with longer lifespans, and broadcast spawners where dominant in the deeper assemblages (5 – 15 m depth). Higher biomasses of crawlers, scavengers and predator species were found in the regularly fished grounds. Assemblages characterized by deep-sea corals and sponges showed higher functional diversity and were associated with three discrete functions: structure forming (and hence biodiversity), nutrient cycling, and bioturbation activity. Although current closures to protect Vulnerable Marine Ecosystems from the adverse impacts of bottom fishing activities protect most of the functional diversity, the spatial scale of influence for each of the functions is unknown and therefore we cannot conclude that the high level of functional diversity found in the current closed areas is sufficient to maintain ecosystem processes over the whole of Flemish Cap.

Poster Session 1 on Monday at 17.30.


Anita Narwani

M. Reyes, A.L. Pereira, H. Penson, S.R. Dennis, S. Derrer, P. Spaak, B. Matthews 

Foundation species determine ecosystem properties and stability by changing community structure and multivariate trait evenness 

A major challenge in ecology is to understand determinants of ecosystem functioning and stability in the face of disturbance. Foundation species can strongly shape community structure and ecosystem functioning, but their impacts on ecosystem-level responses to disturbance are less well known. Shallow ponds provide a model system in which to study the effects of such species because particular taxa can mitigate transitions between alternate ecosystem states. We performed pond experiments to test how two foundation species (a macrophyte and a mussel) affected the biomass of planktonic primary producers and its stability in response to nutrient addition disturbances. In particular, we were interested in determining how taxonomic and multivariate trait variation are affected by foundation species and mediate ecosystem-level effects. We found that each of the foundation species individually reduced phytoplankton biomass and tended to increase rates of recovery from disturbance. When found together, however, these species reversed these effects, leading to repeatable phytoplankton blooms, a loss of recovery from large disturbance events, and increases in temporal autocorrelation of primary production. These changes also caused shifts in other ecosystem properties including increases in dissolved oxygen and turbidity and a decrease in grazer abundances. A structural equations modeling approach showed that blooms of the cyanobacterium, Synechococcus, and a resulting loss of multivariate trait evenness played key roles in driving these changes. Our findings highlight the important effects that foundation species can have in governing ecosystem functioning and stability in the face of disturbance due to their influence on community structure and trait variation. 

Poster Session 1 on Monday at 17.30.


Anna Neuheimer

J.A.T.K. Wong-Ala, C. Chang, E. Goetze

Trait-based explanations of genetic connectivity patterns for zooplankton and fish.

Connectivity is the rate of exchange of individuals across populations – a metric thought to be a major controlling factor for a species’ adaptation potential. While connectivity is often estimated genetically, explaining connectivity patterns requires us to relate observed genetic structure to the underlying biophysical mechanisms controlling connectivity. Identifying these mechanisms also allows us to predict population structure patterns under future environmental conditions as well as for non-target species. Here we present trait-based models of individuals as tools to explore the biophysical mechanisms underlying genetic connectivity. Our models link life history traits (reproductive timing and location, developmental rate, migration behaviour, etc.) to the 3D physical environment to explore how variations in traits change our expectation of modelled connectivity patterns for zooplankton and fish. Examples from our lab include explaining connectivity patterns for coral reef fish communities around Hawai’i Island, and zooplankton species (holoplanktonic copepods) spanning the Atlantic Ocean.

Session D: Traits, Networks and Ecosystem Function



Spiridon Papoulis

Steven Wilhelm, David Talmy, Erik Zinser

Nutrients Explain the Distribution of Restriction Modification Systems in Prokaryotic Genomes

The need to understand the principles that control microbial populations is ever increasing as we learn how microbial communities impact the biological processes of the planet. In this study, we focused our efforts in understanding the top-down control of prokaryotic populations by investigating genomic markers indicative of viral predation. Initially, we took a bioinformatics approach to quantify the number of Restriction Modification (RM) systems in prokaryotic genomes as an indirect measurement to infer which organisms are under extreme selection to maintain innate defense systems. RM systems function by cutting viral DNA to prevent infection, where more RM systems increase the defense potential of an organism. After the analysis of over 13, prokaryotic genomes, we found Prochlorococcus, a marine picocyanobacterium well-known for its domination of the low-nutrient, or oligotrophic ocean, consistently had few RM. Contrastingly, we found that the high end of the RM distribution was dominated by cyanobacteria that generate dense harmful algae algal blooms in eutrophied freshwater systems. Subsequent to our bioinformatic analysis, we undertook an interdisciplinary approach using mathematical modeling to rationalize how nutrients can drive selection for the retention and loss of defense systems in high and low nutrient environments, respectively. We found that despite a variety of viral-host interactions, high nutrients always select for an additional defense and that the retention of RM systems is driven by environmental nutrients through viral predation. This suggests microbial communities with a higher influx of nutrients will select for defensive traits relative to communities with lower available nutrients.

Poster Session 2 on Tuesday at 17.30.


Andrew Pershing

N.R. Record

Changes in community properties under rapid warming

The organisms in an ocean community have traits that allow them to thrive under the prevailing conditions at that location. Climate change is now causing rapid shifts in these conditions. We use an idealized trait-based modeling approach to simulate how marine communities will respond to warming and other climate trends. We initialize our simulations with species that differ in their temperature preferences and temperature tolerances. We impose a trade-off in which maximum population growth is higher for specialists (narrow tolerance) than for generalists (wider tolerance), but growth rates in the latter group decline more slowly away from their preferred temperature. We allow the communities to adjust to a stationary environment (stable mean and variance) and then expose them to different rates of warming. We find that rapid warming causes a decrease in the total abundance of organisms. Diversity also declines under gradual warming but may increase under extreme warming. To test our theoretical predictions, we compared the landings of fish in New England following periods of warming, cooling, or little change. We found a dome-shaped relationship, with maximum landings following periods with little or no trend and reduced landings following both warming and cooling.

Session B: Food-webs and Trophic Interactions



Jérôme Pinti

Thomas Kiørboe, Uffe H. Thygesen, Andre W. Visser

Trait-based modelling of multi-trophic diel vertical migrations and active carbon transport

Diel Vertical Migration (DVM) is a key feature of pelagic and mesopelagic ecosystems, mainly driven by predator-prey interactions along a time-varying vertical gradient of light. The migration pattern of each organism is intrinsically linked to the patterns of its conspecifics, its prey and its predators, through feedbacks that are hard to understand—but important to consider. DVM is not only important for trophic interactions, but also for the biogeochemistry of the world’s oceans. Organisms preying at the surface and migrating vertically actively bring carbon to depth, accelerating the rate of the biological pump, and directly connecting surface production with the mesopelagic ecosystem. Using game theoretic principles, we present a trait-based mechanistic model to infer the DVM patterns of different classes of pelagic organisms simultaneously, shedding light on the direct effects that different trophic levels can have on each other. Based on key traits each population (size, feeding mode), the model is parametrized very simply allowing testing different community assemblages and environmental conditions. The model is then used to estimate the active carbon transport mediated by DVM.

Poster Session 2 on Tuesday at 17.30.


Christoph Plum

Philipp Wenta, Dominik Bahlburg, Stefanie Moorthi

Interactive effects of resource supply, phytoplankton composition and macrozooplankton grazing on phytoplankton stoichiometry along the West Antarctic Peninsula

Climatological changes along the West Antarctic Peninsula (WAP) have resulted in shifts in krill and salp populations as well as phytoplankton composition. Krill and salps represent the most important macrozooplankton grazers at the WAP but differ profoundly in feeding biology, population dynamics, excretion rates and stoichiometric demands. Changes in dominance of these grazers may have major implications for phytoplankton composition and (via recycling) resource stoichiometry with subsequent consequences for the elemental composition of the phytoplankton community. Cellular elemental composition of herbivores and phytoplankton represents an ecophysiological trait that has a strong potential to modify food web dynamics and biogeochemical cycling. However, our knowledge on stoichiometric relations in planktonic food webs of remote ecosystems such as the WAP is limited. The aim of this study is to identify spatial differences in phytoplankton stoichiometry at the WAP ecosystem in relation to grazer abundance, phytoplankton composition as well as cell size distribution. To assess these relations, we sampled 1 stations around Elefant Island and the South Shetland Islands during a field survey aboard the RV Polarstern in austral summer 218. Spatial differences in phytoplankton stoichiometry were observed and assigned to resource availability and spatial patterns of dominant macrograzers. This study enhances our understanding of the consequences of climate-change induced shifts in plankton community composition on food web dynamics and stoichiometric interactions.

Session B: Food-webs and Trophic Interactions



Friederike Prowe

Bei Su, Markus Schartau

Can mesocosm observations inform model trophic structure?

Traits controlling plankton trophic interaction structure the lower trophic levels of the food web, with consequences for both higher trophic levels and the element cycling of carbon, nitrogen and phosphorus. Observing feeding traits in a complex natural food web is challenging. Controlled laboratory conditions facilitate the observation of traits, but are typically restricted to specific species. A variety of species and the variability of natural plankton communities can be investigated in mesocosms. Here we investigate whether a model-based analysis of mesocosm observations of food webs can inform about the underlying trophic pathways. We base our study on the existing model of Larsen et al. (Limnol. Oceanogr. 6, 215, 36-374) that describes the shift from a diatom- to a bacteria-dominated community by adding a trophic link between ciliates and diatoms. An alternative model includes a pathway where ciliates and diatoms are targeted separately by copepods with passive and active feeding traits. For both model configurations we perform parameter identification analyses, including maximum likelihood estimation of the models’ parameter values. We compare the optimised solutions of these models and evaluate whether the available observational data suffice to identify and constrain either of the potential trophic pathways. We discuss the explanatory power of observed changes in community structure, which may guide the development of trait-based models for large scale biogeochemical applications.

Poster Session 2 on Tuesday at 17.30.


Deepa Rao

Stephanie Dutkiewicz, Michael J. Follows

Modeling morphotypes: A trait-based approach to modeling transitions between single cells and colonies of the Phaeocystis genus

The Phaeocystis genus is a cosmopolitan phytoplankton species that has massive, recurrent seasonal blooms in high-latitude coastal environments. Although Phaeocystis plays a fundamental role in carbon and sulphur biogeochemistry, it is often not well represented in marine microbial ecosystem models, partially due to limited observational data. Phaeocystis is a haptophyte with a polymorphic life cycle, that alternates between free-living, flagellated unicell stage (3-8 µm diameter) and a colonial stage consisting of hundreds to thousands cells living in a mucus matrix (1s µm - mm in diameter). In its colonial stage, Phaeocystis forms near monospecific blooms, indicating that it has a distinct fitness advantage. In essence, Phaeocystis can be considered as a population with a single genotype with multiple phenotypes. In this study we explore the trait-trade-offs of multiple morphotypes. First we use proteomics data to develop mechanistic insights into the differences between unicell vs colony stage traits expressed in culture treatments based on the KEGG orthology database of molecular functions. Second we incorporate this Phaeocystis model in a 1D water column model to examine competition dynamics and the seasonal transitions between single vs colonial cells. We focus on examining colony-specific traits that can infer a fitness advantage and observation-based size scaling for the number of cells per colony. These advantages include reduction in top down control, changes in how iron is acquired, and increased (size-dependent) internal quota of larger colonial cells. Initial results show that having multiple morphotypes can expand the theoretical and realized niche of model Phaeocystis, potentially enabling it to persist until conditions are favorable.

Poster Session 2 on Tuesday at 17.30.


Marina Rillo

Mauro Sugawara, Brenno Cabella, Lukas Jonkers, Michal Kucera, Thomas Ezard

On the mismatch in the strength of competition among fossil and modern species of planktonic Foraminifera

Many clades display the macroevolutionary pattern of a negative relationship between diversity and diversification rates, and competition among species has been proposed as the main mechanism underlying this pattern. However, we currently lack empirical insight into how the individual-level effects of ecological interactions scale up to affect species’ diversification. Here we investigate the planktonic foraminifera clade that shows the negative diversity-diversification relationship across the Cenozoic fossil record, and test whether modern communities are regulated by interspecific competition. We explore two patterns expected under interspecific competition, under the assumption that ecologically similar species compete more strongly. (i) Spatial pattern: by globally combining species relative abundances in seafloor sediments and a community phylogenetics approach, we test for signs of local competitive exclusion among ecologically similar species (defined as closely related or of similar sizes). (ii) Temporal pattern: using sediment-trap time series spanning from one to 12 years, we analyse whether population abundances of co-occurring species co-vary negatively through time. The great majority of our seafloor assemblages show no significant co-occurrence patterns in space regarding phylogeny or size, and are indistinguishable from randomly assembled communities. Through time, most species pairs correlated positively, indicating synchronous population dynamics instead of compensatory dynamics. Synchronicity is also observed between species pairs of similar sizes, closely related or with similar symbiotic strategy. Thus, we found no evidence for interspecific competition structuring extant planktonic foraminifera communities. Neutral processes seem to dominate how these communities are assembled, and population dynamics are likely regulated by the abiotic environment and distantly related species, rather than intra-clade density dependent processes. To bring community ecology and macroevolution closer together, we need to consider defining the species pool of macroevolutionary dynamics ecologically rather than only phylogenetically.

Poster Session 1 on Monday at 17.30.


Alex Ryabov

A. M. de Roos, B. Meyer, S. Kawaguchi, and B. Blasius

Competition-induced starvation drives large-scale population cycles in Antarctic krill

Age structured models allows us to analyze the influence of asymmetries in the traits between different developmental stages on the age structure and stability of a population. Here we show how changes in starvation mortality with krill age can lead to large scale population cycles.Antarctic krill exhibits a five to six year population cycle, with oscillations in biomass exceeding one order of magnitude.Using data analysis complemented with modelling of krill ontogeny and population dynamics, we identify intraspecific competition for food as the main driver of the krill cycle, while external climatological factors possibly modulate its phase and synchronization over large scales. Our model indicates that the cycle amplitude increases with reduction of krill loss rates. Thus, a decline of apex predators is likely to increase the oscillation amplitude, potentially destabilizing the marine food web, with drastic consequences for the entire Antarctic ecosystem. 

Poster Session 2 on Tuesday at 17.30.


Fredrik Ryderheim

Thomas Kiørboe, Erik Selander

Quantification of trade-offs of toxin production in PST-producing dinoflagellates

Studies dedicated to defense mechanisms in plankton have often focused on the benefits of the defense, but have rarely established potential costs. Dinoflagellates and the toxins they produce are well studied, but so far many experimental assessments of the trade-offs have shown defense costs to be insignificant. However, for defense mechanisms to be considered adaptive there must be associated costs; otherwise, non-defended strains would be outcompeted and all species would be equally defended, which they are not. In addition, toxin production is inducible; i.e., it is upregulated in the presence of grazers, further suggesting that costs are substantial. The failure of experiments to demonstrate the costs may simply be because experimental assessments are done under resource replete conditions, while costs may be more significant when resources are deficient. To explore the potential trade-offs, we established chemostat cultures of Alexandrium spp. under nitrogen-limitation and induced elevated toxin production using chemical grazer cues. We used direct video-observations to quantify the benefits of toxicity, as the fraction of captured cells that are rejected by copepod grazers. We finally quantify the trade-off by exploring the relation between mortality and growth rate of induced vs non-induced cells under different regimes of nutrient limitation.

Poster Session 2 on Tuesday at 17.30.


Angel Segura

A constraint envelope approach test for competing theories explaining the fluctuations and variability of natural population and communities

Unveiling the mechanisms that molds populations fluctuations is central for understanding the dynamic of pest outbreaks, harmful algal blooms or extinction risk. We hypothesize that metabolic restriction to maximum population abundance shapes single population and community fluctuations. Here, we derive a formal theoretical model linking metabolic limits to maximum population abundance with the distribution of fluctuations of single populations and communities. First, we show that the emergence of fat tails in the distribution of single population fluctuations is caused by the metabolic effect on maximum population abundance of periodic changes in resource supply or temperature. Second, we show an explicit link between single population fluctuations and the Laplace distribution of aggregated community fluctuations. Third, we derive a general relationship between population variance and body mass (called variance-mass allometry; VMA). Predictions were evaluated on an exceptional data-set of plankton with 15 years of weekly samples encompassing ~25 planktonic species from three trophic levels, sampled in the western English Channel (L4 station). This framework provides a theoretical mechanism to explain fat-tailed distributions of population fluctuations and the double exponential or Laplace distribution of community fluctuations observed in the L4 data. Finally, it provides a generalization of the VMA model which is able to generate predict patterns of variability among species lifestyles. Alternative competing models were compared to empirical data furthering our understanding about the determinants of abundance fluctuations.

Poster Session 2 on Tuesday at 17.30.


Camila Serra-Pompei

A.W. Visser, T. Kiørboe, K.H. Andersen

Emergent patterns in size-structured models of copepod communities

Copepods (small aquatic crustaceans) link primary producers to fish, thus influencing the dynamics of both lower and higher trophic levels in marine food-webs and associated biogeochemical cycles. Life cycle of organisms strongly influences population dynamics, yet plankton-ecosystem models often omit copepods life cycle. Here we develop a size- and trait-based ecosystem model that includes copepods and their life cycle, protists, detritus, and nutrients dynamics. Using mechanistic individual-level processes, we model population dynamics of key copepod group, characterized by size and feeding mode. Size resolves physiological rates and organisms’ predator-prey interactions. By means of approximate analytical solutions and dynamic simulations, in steady and seasonal environments, we investigate the patterns and traits that emerge within the community. We show that, competition between large protists and juvenile copepods (intraguild predation) defines feeding mode in small copepods. In productive systems, copepod’s growth is strongly regulated by density-dependent competition, and therefore productivity increases at higher mortality rates. Finally, we discuss the mechanisms that lead to observed seasonal dynamics for different latitudinal scenarios. This simple, yet more realistic model, opens the possibility to improve end-to-end size-structured models of marine systems and investigate biogeochemical processes such as carbon export and trophic transfer.

Session B: Food-webs and Trophic Interactions



Shlomit Sharoni

Itay Halevy

The population structure of exponential-growing phytoplankton is the main determinant of marine particulate organic matter stoichiometry

As phytoplankton biosynthesize biomass from inorganic substrates, their elemental stoichiometry dictates the amount of nutrients transferred to higher trophic levels, and the amount of carbon sequestered in the ocean’s interior. Thus, the ratio of carbon to nitrogen to phosphorus (C:N:P) in phytoplankton, is a key component of global biogeochemistry and climate regulation. Recently observed meridional variation in the C:N:P of particulate organic matter (POM), lacks a robust, process-based explanation. On the basis of global datasets, local observations and phytoplankton population models, we suggest that the population structure of well-adapted phytoplankton is a dominant control on POM stoichiometry, and that fine-scale variations in cellular C:N:P, perhaps driven by environmental stresses, play a more minor role. While a change in environmental conditions leads to acclimation of some species, more importantly, it selects out of the standing diversity for species suited to the local environment, which grow to dominate the assemblage and the composition of POM.

Poster Session 2 on Tuesday at 17.30.


Nuno Simoes

a review of mega-fauna symbiotic species associated with sponges from the Gulf of Mexico and the Caribbean Sea

Ecological interactions on coral reefs play a fundamental functioning role and could explain the high species richness of these habitats. The nature of symbiosis have been recognized as an important speciation mechanism. Sea sponges are a dominant element of these environments that contribute to the vertical complexity and texture of the reef matrix, providing a variety of micro-habitats for a myriad of reef species. This role is particularly important in the Golf of Mexico and Caribbean sea, where upon the decline on reef building species and flattening of the reefs due to an increased erosion rate, sponges help compensate such habitat structure reduction, and provide shelter to many invertebrate and fish species, significantly contributing to the resilience of the region reefs. The specificity, importance and role of the sponge symbiotic species interaction is poorly described. A single sponge can host a single symbiont or more than one? Symbionts are so specialized that their relationship is exclusive to a single sponge species or, can they colonize multiple sponge species? Or, is the symbiont species an obligate, facultative or general comensalist? This review describes and compares all known records of mega-fauna species associated with sponges in these two regions. The obtained results quantified the diversity of symbionts associated with each species of sponge, determined some patterns that may be molding the diversity of associated species, and finally enabled a tentative classification of the symbiont species along the incidental-obligate interactions. The results conclude that the sponge-symbiotic species diversity in the Caribbean Sea is greater than that of the Gulf of Mexico, although such diversity is dominated by alpheid shrimps and amphipods. In contrast, the taxonomic diversity at the family level is larger at the Gulf of Mexico.

Poster Session 1 on Monday at 17.30.


Lan Smith

Phenotypic plasticity sustains modelled phytoplankton size diversity by flattening fitness gradients, but may confound observed relationships

Inducible phenotypic plasticity has long been known to impact the growth response of a wide variety of organisms, and more recently has been appreciated as a determinant of biodiversity, production, and ecosystem function. However, considerable uncertainty remains about how intra-specific trait variation may contribute to biodiversity. Photo-acclimation is a well known example of physiological flexibility for phytoplankton, and a variety of models have been developed to represent its effects on their growth, chlorophyll and nutrient content. I apply a sized-structured model accounting for the photo-acclimation response of phytoplankton (FlexPFT), as well as a control model lacking this response, to two contrasting time-series observation sites from the North Pacific ocean: a relatively calm subtropical site (stn. S1) and a more variable subarctic site (stn. K2). As previously reported (Smith et al. J. Plankton Res. 216), compared to the control, the FlexPFT model reproduced better the available observations of size fractionated chlorophyll, nutrients, and primary production and predicted greater size diversity. Here I clarify that this is because phenotypic plasticity flattens fitness gradients, quantified here as specific growth rate vs. size. This effect contributed more to enhancing size diversity at the more variable subarctic site than at the calmer subtropical site. However, at both sites modelled size diversity differs substantially as calculated in terms of chlorophyll, carbon or nitrogen biomass, because the degree of flexibility differs with cell size, as a result of the size-scaling of traits. Modelled distributions of chlorophyll over size tend to be substantially less even (lower diversity) than those of either fitness or biomass. This suggests that, although much more widely available than observations of biomass or growth rate, chlorophyll-based size distributions should be interpreted with care.

Poster Session 1 on Monday at 17.30.


Karen Stamieszkin

Using allometry to model copepod-mediated carbon flux – how well do we estimate key rates?

Ecosystem modeling and trait-based approaches go hand-in-hand because efficient computation necessitates simplification of natural complexity. Ideally, trait-based approaches distill this complexity to reveal the mechanistic underpinnings of an ecosystem, without losing functionality. Size is used as a master trait because it is consistently linked to metabolic rate, and shows coherent patterns along environmental gradients. It also captures trophic dynamics via idealized predator:prey size ratios. The biological carbon pump is an important component of the ocean’s carbon cycle, but it is hard to measure on large enough spatial and long enough temporal scales to see major changes. We developed a size-based model to estimate carbon flux through different export pathways associated with copepods, the most numerous metazoan in the ocean. These pathways included organic carbon production as sinking fecal pellets in surface waters, and respiration of dissolved inorganic carbon at depth during diel vertical migration. We also measured these rates on the 218 NASA EXPORTS field campaign to the Subarctic Northeast Pacific Ocean. I compare the predicted carbon flux pathways with measured values, and discuss the efficacy of the size-based model. I also highlight traits other than size that could improve model outputs.

Poster Session 2 on Tuesday at 17.30.


Maren Striebel

Miriam Gerhard, Apostolos M. Koussoroplis, Helmut Hillebrand

Phytoplankton community responses to temperature fluctuations under different nutrient concentrations and stoichiometry

Nutrient availability and temperature are important drivers of phytoplankton growth and stoichiometry. However, the effect of temperature fluctuations on phytoplankton communities and its interactions with nutrient supply is unclear. Using a natural phytoplankton community, we conducted a laboratory experiment under two temperature regimes, fluctuating and constant, across 25 different combinations of N and P supply. In comparison with constant conditions, fluctuating temperatures decreased phytoplankton growth rate (rmax) supporting Jensen´s inequality prediction. In addition, the thermal performance curve shape was altered by nutrient conditions. Stoichiometric responses to temperature treatments supported the idea that phytoplankton cellular nutrient allocation can be adjusted according to the temperature regime. However, the responses shown by the phytoplankton communities to the temperature conditions were not highly explained by differences in the species diversity and composition. Our results suggested that temperature fluctuations interacting with nutrient conditions strongly affect the phytoplankton physiology and stoichiometry at the community level.

Poster Session 2 on Tuesday at 17.30.


Bei Su

A. Tagliabue

Phytoplankton utilisation of dissolved organic phosphorus: Insights from an optimality-based model

Phosphorus (P) is essential nutrient to life in the ocean, regulating oceanic primary production in tropical regions and acting as the ultimate limiting oceanic nutrient on long timescales. The major dissolved inorganic P (DIP) pool in the ocean is phosphate (PO4) and P stress may occur due to excess nitrogen (N) supply from both anthropogenic N deposition or N2 fixation, as well as via a decline in absolute physical supply of PO4 in response to enhanced stratification. Under PO4 scarcity, some phytoplankton exploit the larger dissolved organic phosphorus (DOP) by synthesizing the hydrolytic enzyme alkaline phosphatase (AP), which then alleviates P-limitation, but also requires increased N investment. It is unclear how the relative trade-off between P acquisition and N allocation to P acquisition enzymes affects DOP-utilising phytoplankton in the context of biogeographic variations in the availability of N, DIP and DOP across the tropical ocean. Here we extend an existing optimality-based chain model of the phytoplankton cell, to include the physiological response of phytoplankton to DOP utilisation, via trade-offs associated with AP synthesis. Our model represents the observed inverse hyperbolic relationship between DIP concentration and AP activity (APA) via dynamic feedbacks between the intracellular P demand and ambient DIP availability. APA, regulated by the internal P demand, responds rapidly to environmental DIP fluctuation in our model. Via a set of competition experiments with a non AP producing competitor, we find DOP-utilising phytoplankton have an advantage in regions with high DIP-limitation, but only alongside sufficiently high DOP and DIN concentrations. This arises due to the trade-off between P acquisition and N allocation to AP synthesis and is not affected by varying the model assumptions regarding nutrient supplies, N-demand and key physiological traits. Extrapolating our results to the global ocean using NO3, PO4 and DOP datasets permits us to highlight key regions where optimal conditions for APA occurs, which compare well to the patterns that available APA observations inform of. Given the future P scarcity in the tropical ocean in response to enhanced N addition and stratification, DOP-utilisation will become a key trait for understanding the future biogeographical shift of different microbial groups. Further work is needed to include the parallel role for the trace metal co-factors iron and zinc in driving AP synthesis and its spatial distribution.

Poster Session 2 on Tuesday at 17.30.


David Talmy

Selina Vage

Trade-offs modify ecosystem biomass structure along trophic gradients

In a broad range of terrestrial and aquatic environments, predator biomass scales with prey biomass following power laws with exponents less than one. Prey production and prey biomass has also been shown to scale sub-linearly in diverse systems. We present a general model to interpret widespread patterns of predator-prey and production-biomass scaling. The model allows competition along trophic gradients among prey with traits governed by a trade-off between resource acquisition, and defense against predation. We show that low resource supply selects prey that persist at low biomass density but take up resources rapidly and are subject to intense top-down control by predators. High resource supply selects prey that persist at high biomass density, but with low affinity for resource acquisition, and high ability to resist predators. In the plankton, cell size may be associated with a trade-off between resource acquisition and defense against predators, and there are clear increases in average cell size along trophic gradients. In fish and terrestrial ecosystems, defensive behaviors may be less tightly linked with organism size, and instead may be driven by allocations of time, energy and resources toward predator deterrence and avoidance. Our theory explains density-dependent variation in behavioral, physiological, and morphological traits observed in diverse systems.

Session A: Traits, environments, ecology and evolution



Davi Tavares

Jailson Fulgencio de Moura, Esteban Acevedo-Trejos, Agostino Merico

Traits shared by marine megafauna and their relationships with ecosystem functions and services

Trait-based approaches are being promoted for studying community structure and functions of various groups of organisms, including terrestrial plants, phytoplankton, zooplankton, corals, mammals, and microbes. However, we still lack a consistent trait-based framework for the study of marine megafauna, here comprising large fishes (e.g. billfishes, tuna and sharks), sea turtles, marine mammals (i.e. pinnipeds, sirenians and cetaceans) and seabirds. Here we (1) present key traits that are measurable and comparable among marine megafauna, (2) summarise the relationships between the identified traits and critical ecological functions and services, and (3) discuss the relevance of the trait-based approach for marine megafauna research and conservation. Although body size has a remarkable impact on the organisation of animal communities, attributes such as dietary preference, feeding strategy, metabolic rate, and dispersal capacity, have a strong influence on nutrient transport, trophic-dynamic regulations of populations, and community structure. We show, for example, how feeding strategy is correlated to the exposure of marine vertebrates to plastics, with potential cascading impacts on population abundances. We also suggest how a typically overlooked trait like the charismatic potential can be associated with critical ecosystem functions like the maintenance of biological diversity via the economical revenues generated from tourism. A considerable amount of information on the physiology and ecology of marine megafauna has been collected by naturalists over centuries and, more recently, by a vast network of scientists. This information, we argue, constitutes a solid foundation for the development of a trait-based framework for a new wave of studies on marine megafauna.

Session A: Traits, environments, ecology and evolution



Josefin Titelman

Kim Aalborg, Jan Heuschele, Tom Andersen

Copepod pigmentation – more colorful and plastic than we acknowledge?

While often considered little escape machines with sophisticated behaviors acting at both small and large spatial scales to reduce predation risk, copepods also vary dramatically in pigmentation. Common to all pigmentation patterns, or lack thereof, is that they affect the detectability of an organism to visual predators. We therefore hypothesize that copepod pigmentation is a plastic trait that will vary with other traits such as size and life style, as well as with the optical environment. We present preliminary results from a field study in a 2m deep fjord with varying optical environments. We quantified both apparent coloration and pigment concentrations of individual copepods across a wide range of species and sizes. Both apparent coloration and pigmentation concentrations seemed related to the optical environment, also when subtracting food pigments. We discuss our results in light of the consequences of pigmentation for predation risk in different optical habitats.

Poster Session 2 on Tuesday at 17.30.


Ioannis Tsakalakis

Stephanie Dutkiewicz, Mick Follows, Joseph Vallino

Patterns of phytoplankton diversity driven by resource fluctuations in a global ocean model

Resource fluctuations is a main driver of temporal niches among phytoplankton taxonomic or functional groups, affecting species composition and diversity. In this study we focus on the two major periodic processes of resource fluctuations in the ocean, the seasonal and the diel cycle, and study their importance for understanding large-scale patterns of phytoplankton biogeography and diversity. We consider three phytoplankton functional groups of differing size that represent distinct adaptations to resource fluctuations: small-size gleaners (high affinity for nutrient uptake), medium-size opportunists (high maximal growth rate) and large-size hoarders (high capacity in nutrient storage). We will present preliminary results on the biogeography of the three functional groups in the global ocean, with a special focus on the latitudinal and productivity gradients. Our analysis includes idealized modelling on the effects of resource fluctuations and analysis using the MIT General Circulation Model. In addition, we use a thermodynamic-based analysis to estimate energy flow through phytoplankton community and the abiotic environment, focusing on the role of trait adaptations to fluctuating resources.

Poster Session 1 on Monday at 17.30.


Daniel van Denderen

Ken H Andersen

Vertical feeding strategies and pelagic-benthic energy flows determine fish food-web structure across marine ecosystems

Size-based fish community models have been developed to characterize the structure of fish communities and to describe energy flow between the upper trophic levels in marine ecosystems. Thus far, these models have overlooked important aspects of fish diversity that emerge due to variation in feeding straAbsrtegies (e.g. zooplanktivorous, benthivorous) and behaviors (e.g. diel vertical migrations) that are all associated with the vertical habitat strategy of a fish. Here, we present a size- and trait-based fish community model that resolves the vertical structure of a fish community from shelf systems to open ocean environments. Fish individuals interact with each other through predator-prey interactions that are determined by a combination of habitat overlap in the water column and body sizes of predator and prey. Our results show how pelagic-benthic energy flows, in combination with seabed depth, change the vertical structure of the fish community and determine the dominant fish functional groups. We furthermore show that in open ocean regions with a substantial detritus flux to the seabed (typical for temperate and polar environments), fish feeding interactions may drive a feeding cascade of carbon to depth. Such cascades do not occur in areas that are primarily structured around the pelagic pathway. Our results highlight the driving forces of fish community structure in marine ecosystems. The model can be used as a tool to predict global fish and fisheries production and to examine climate impacts on upper trophic level marine ecosystems.

Session B: Food-webs and Trophic Interactions



Ben Ward

S. Collins, C.R. Young, B. Sauterey

Functional and taxonomic diversity in a global ocean metacommunity model

Recent global surveys have unveiled enormous levels of diversity in marine microbial communities, with molecular analysis suggesting the existence of up 15, genera of marine eukaryotes in the photic layer of the ocean alone. Analysis of this data suggests a division between taxonomic diversity (identified by neutral genetic markers) and functional diversity (identified by association with genes of known function). We present results from am new 'matrix metacommunity model' that allows the emergence of both functional and neutral diversity. Environmental dispersal, ecological selection and the adaptive generation of new phenotypes are manipulated within the model, allowing assessment of their influence on community assembly, in terms of both functional and taxonomic diversity.

Poster Session 1 on Monday at 17.30.


Jamie Wilson



Poster Session 1 on Monday at 17.30.


Alexandra Worden

Session C: Multifarious lifestyles of marine microbes



Emily Zakem

Martin Polz, Mick Follows

Incorporating metabolic diversity into trait-based modeling frameworks with metabolic functional types

Microbial activity mediates the global flow of carbon, oxygen, nitrogen, and other elements, including climatically significant gases. However, non-photosynthetic microbial activity is typically not resolved dynamically or mechanistically in global models of the marine and terrestrial biospheres, inhibiting predictive capability. Understanding the global-scale impact of complex microbial community activity requires a consistent framework with which to constrain the parameterizations of diverse metabolisms. Here, we describe how the key redox chemistry underlying specific metabolisms can be exploited to parameterize diverse metabolic strategies. By quantitatively relating metabolic yields to chemical gradients, the growth and respiration of microbial biomass is systematically related to stoichiometries of substrate consumption, oxidation, and reduction that constitute biogeochemical fluxes. Linked with parameterizations of resource acquisition rates, whole organism metabolism can be integrated into trait-based modeling frameworks as metabolic functional types. Benefits of this approach include prognostic metabolic biogeography and ‘gene-fluent’ predictions of community metabolism. The theoretically grounded, electron-balanced framework progresses the description of microbial ecosystems towards conservation of energy as well as mass.

Session D: Traits, Networks and Ecosystem Function