CoML-MarBEF-EuroCoML modelling workshop

Novel modelling approaches to relate biodiversity of marine sediments to ecosystem functioning

We propose to hold an expert-meeting on innovative modeling approaches in marine benthic biodiversity research. This joint CoML-MarBEF-EuroCoML workshop will take place on 15-17 October 2007, in Amsterdam.

Aims of the workshop
- We will develop new modeling approaches for benthic marine biodiversity research that are strongly linked to active empirical work within CoML, EuroCoML and MarBef.
- We aim to establish a collaborative new research project, if possible in relation to .
- The meeting will result in a paper on the mechanistic modeling of marine benthic biodiversity.
- Our overall aim is to strengthen collaborative links between the leaders in this field.

Selection of participants
Selection is based on submitted statements by participants explaining why they want to participate, what their expertise is and what they intend to contribute to the workshop. MarBEF participants may use their own budget.

Modeling within the Census of Marine Life

The world's oceans are changing, and a prime goal within the Census of Marine Life (CoML) is to collect information on marine life and the physical and chemical characteristics of the marine environment, so that the causes and effects of these changes can be understood. In order to make predictions, we need mathematical modeling approaches that synthesize our current data and understanding. Based on these models we will formulate hypotheses for focused research and generate future scenarios of change. This crucial task of model development is taken up by the Future of Marine Animal Populations (FMAP), which is the predictive modeling component of the CoML.

FMAP: The benthic component. The changes that act upon the marine environment are evident in the pelagic ecosystem, but they are equally affecting the diverse communities of organisms that inhabit marine sediments (the soft-bottom benthos). The marine sediment ecosystem supports a high biodiversity and provides key ecosystem services (Snelgrove et al. 2000), especially in the productive shallow waters of the continental shelves.

A considerable body of knowledge is now available on the relations between benthic biodiversity and these ecosystem functions. Our knowledge on food sources, redox processes and general ecological processes in marine sediments has reached the point where much insight and synthesis can be reached through mechanistic modeling.

We propose to develop a series of models that predict relations between benthic biodiversity, organic matter input, macrofaunal engineering activities, carnivory and microbial-geochemical rates. Explicitly defining the main mechanisms underlying benthic biodiversity and its relations to ecosystem functioning will enhance our ability to predict the behavior of marine benthic systems and their response to both present and future human-imposed change. Mechanistic models can further be used to evaluate our understanding of the existing gradients in marine benthic biodiversity.

Summary of proposal
To further discuss the development of such models and the data requirements to support them, we propose a joint workshop between the Census of Marine Life, (CoML & EuroCoML) and the EU Network of Excellence MarBEF ( The aim is to discuss a variety of mechanistic approaches to predict future changes in benthic marine communities based on the parameterization of natural and human impacts (climate change, eutrophication, mechanical disturbance, overfishing). The overall goal is a better mechanistic understanding of the sediment ecosystem, allowing predictions of how benthos would react to global change in the ocean. MarBEF is preparing a project on the Modeling of Marine (Benthic) Biodiversity, and invites CoML and Diversitas to join this project.

Le Quere, C; Aumont, O; Monfray, P; et al. (2003) Propagation of climatic events on ocean stratification, marine biology, and CO2: Case studies over the 1979-1999 period. Journal of Geophysical Research-Oceans. 108
Kristensen, J. Kostka, and R. Haese (Eds) Interactions between micro- and macroorganisms in marine sediments, AGU.
Snelgrove et al. (2000) Linking biodiversity above and below the marine sediment-water Interface. Bioscience, 50: 1076-1088.
Van Oevelen et al., (2006) Carbon flows through a benthic food web: Integrating biomass, isotope and tracer data. Journal of Marine Research 64:453-482.
Vézina, A.F. and T. Platt (1988) food web dynamics in the ocean .1. best-estimates of flow networks using inverse methods. Marine Ecology-Progress Series 42:269-287.

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Event programme:


To provoke further thoughts and initiate discussions we pose 4 major questions.


Four questions

[1] What governs patterns in benthic biodiversity, at different scales?

At the scale of the world ocean, large differences exist in the diversity of macrobenthic species. In general, the number of species increases when going from shallow, highly productive estuarine systems towards deeper and less productive sites, while diversity may decrease again towards very oligotrophic deep-sea sites. For shelf systems, numerous studies describe a relationship between organic input to the sediment and biodiversity (the Pearson-Rosenberg / Rhoads gradient). One modeling challenge is to relate macrobenthic biodiversity to the quantity and quality of organic matter reaching the sediment. Using new tools available for the study of food webs in benthic communities as well as new developments in the microbiology of sediments, we should be able to conceptualize and model the important links in these detritus-based systems.


Explanations of benthic biodiversity may span scales ranging from a cubic inch of sediment to the floor of the world ocean. The scale relevant to explanations of diversity may strongly differ between different groups (macrofauna, meiofauna, microbial communities). While continuous functions may apply to the activity of microbial communities, it will in some cases be important to consider both individual and population level behaviors of macrofaunal species. Modeling approaches could address the links between these levels of ecological organization as well as the importance of temporal and spatial variation around means. Since such heterogeneities are primary factors promoting diversity, they will be at least as important as average behaviors in our predictions. The concepts derived from our mechanistic modeling can be used by research groups that mainly employ statistical approaches. Such concepts and mechanisms can be fed into statistical model analyses that aim to explain gradients of biodiversity.


[2] Which ecosystem functions are most strongly affected by (or related to) benthic biodiversity and how can we model them?

In the present literature the most well-studied ecosystem functions are those that are easiest to measure (especially nutrient fluxes across the sediment-water interface). These fluxes are important in terms of benthic-pelagic coupling, but other key functions of the marine benthos remain relatively under-studied. To more fully understand a wider range of benthic macrofaunal functions we may have to encourage empirical research to become more inclusive of additional processes and rate-modifiers, such as secondary productivity, denitrification, carnivory, bio-turbation, bio-irrigation and habitat modification.


Formulating a mechanistic model makes clear how different ecosystem functions can differ tremendously in the complexity of their relation with benthic biodiversity. For example, we could expect a straightforward relation between secondary production and the diversity of macrofauna (similar to that in terrestrial plant species) due to for instance complementarity effects. In contrast, functions such as nutrient fluxes constitute a complex integration of microbial and macrofaunal activity. A mechanistic prediction of such diversity-flux relations thus requires an opening of the benthic ‘black box’. This black box is in fact the sediment ecosystem, with all species (typically macro-fauna) being placed on the left of the box, and all ecosystem functions (typically fluxes across the sediment-water interface) being placed on the other side.


[3] How important are ecosystem engineers in controlling marine benthic biodiversity?

Heterogeneities and gradients created by burrowing and reef building species provide habitat, structure, food and refuges for a great variety of endobenthic species. Empirical studies clearly show that the occurrence of bioturbators relate to the overall organic flux to the sediment. The chemical ‘hostility’ of the (anoxic) environment and the possibilities to overcome this hostility seem to be a major cost of bioturbation. It is less clear, but probable, that concentration and quality of food are worse at depth in the sediment. On the benefit side is enhanced protection from predators (see question 4), which may allow populations to survive on low quality food. However, many other processes (e.g. growth of chemo-autotrophs on chemical gradients; alteration of microbial degradation pathways and enhancement of microbial growth efficiency; better anoxic preservation of organic matter and buffering of peaks in organic matter input) may be involved. An interesting question is also whether there is a minimum threshold of bioturbation that should be reached before the advantages in the distribution of organic matter and microbiota appear. Apart from these challenges to model and understand the occurrence of bioturbation, the interaction of the process with biodiversity is of primary interest. Here we especially think of the relative contributions of competition for food, commensalisms and mutual facilitation among different associated endobenthic species and (large) bioturbators.


[4] How important are communities of higher-level consumers in structuring marine benthic biodiversity?

Food web theory holds that predation by carnivores, widespread omnivory within the benthos itself and patterns in the strength of food web links in general all greatly affect the possibilities for persistent biodiversity in benthic ecosystems. However, the sediment matrix makes direct observations of trophic interactions in the benthos notoriously difficult. Therefore indirect approaches have been developed, which make use of the body composition (e.g. stable isotope signatures or fatty acid composition) or gut content analysis to discern trophic relationships. To translate these observations to trophic interactions, one employs inverse modeling. Inverse modeling combines a connectance food web, which describes the food web compartments as a set of coupled mass-balances, with observations on biomass, trophic interactions or processes to quantify all trophic interactions in a food web (Vézina & Platt 1988). Uncertainty analyses and the introduction of additional data sources can reveal and decrease uncertainties on trophic flows (Van Oevelen et al., 2006). Inverse modeling thus provides a powerful tool to bridge the gap between empirical data and benthic food web analysis.

Benthic animals are subject to both lethal and sub-lethal fish-predation, and they adjust their feeding and engineering activities (f.e. burial depth) accordingly. In addition, the burrowing activities of some macrofaunal species (crabs) strongly affect where different bird species do and do not feed on other macrofauna (polychaetes) in tidal mudflats. Complex feedbacks thus exist between macrofaunal activity (bioturbation, bioirrigation), predation pressure, microbial metabolism and mineral geochemistry, all of which are intricately linked with benthic marine biodiversity.


Integration of modeling approaches

Given the complexity of the interactions and multiple feedbacks, a further integration of one or more of the following existing modeling approaches (food web modeling/inverse techniques, sediment bio-geochemistry/transport models, mechanistic diversity-function modeling, and modeling of the relation between environmental conditions and marine benthic diversity itself) could provide a way forward.


Modeling change

Mechanistic models allow us to evaluate different scenarios for environmental change. These may include, among others:

- global warming / low-oxygen zones / winter storms / freshwater inflows

- changes in organic matter input / eutrophication

- changes in fishing pressure on benthic macrofauna and higher-level carnivores

- local and regional catastrophes / increased mortality rates / partial habitat destruction

- increased CO2 levels / acidification / problems for calcifying organisms

- changes in natural resource management

- changes in physical stresses


Collaborators and organisers:


Carlo Heip, Peter Herman, Johan van de Koppel, Filip Meysman, Jack Middelburg, Dick van Oevelen, Karline Soetaert, Matthijs Vos

Netherlands Institute of Ecology, Yerseke, The Netherlands


Organization / Contact: Dr. Matthijs Vos,
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