Publication Abstract

Towards end-to-end models for investigating trophic controls and changes induced by climate and fishing in marine ecosystems

M. Travers, Y-J. Shin, S.Jennings and P.Cury

End-to-end models that represent ecosystem components from primary producers to top predators, linked through trophic interactions and affected by the abiotic environment, are expected to provide valuable tools for assessing the effects of climate change and fishing on ecosystem dynamics. Here, we review the main process-based approaches used for marine ecosystem modelling, focusing on the extent of the food web modelled, the forcing factors considered, the trophic processes represented, as well as the potential use and further development of the models. First, we consider models of a subset of the food web (NPZD-type models, MSVPA, Osmose). Second, we consider those models which represent the first attempts to couple low and high trophic levels (Hermann’s model, Sourisseau’s model, NEMURO.FISH and SEAPODYM). Finally, we consider integrated models of the whole ecosystem such as Ecopath with Ecosim, ERSEM, IGBEM/BM2 and size spectrum models. Comparisons within and among these groups of models are used to highlight differences in the discretization adopted (functional groups versus species-based) according to the part of the food web considered, the representation of forcing factors and the importance of the spatial dimension used for representing organism dynamics.

The advent of an ecosystem approach to fisheries and concerns about the ecological effects of climate change have created new challenges for marine scientists. Where many existing models adequately addressed specific issues relating to bottom-up forcing of production or the top-down effects of fishing these models have not supported an easy examination of the interplay between exploitation and climate effects. This examination is most seamlessly achieved through end-to-end modelling, but a suitable model allowing a simultaneous examination of the implications of fishing and climate effects throughout an ecosystem is not available. We suggest that immediate progress is best achieved by coupling LTL and HTL models. The advantage of this process is that the extent of discretization and representation can be suited to the part of the food web considered and that processes such as predation can be coupled to allow the propagation of forcing factors effects up and down the food web. We suggest how effective coupling might be achieved by recommending approaches for developing of retroactive links between models and methods for dealing with different time and space scales, currencies of energy, nutrients and mass and different levels of species resolution.

Reference

M. Travers, Y-J. Shin, S.Jennings and P.Cury (2007) Towards end-to-end models for investigating trophic controls and changes induced by climate and fishing in marine ecosystems. Progress in Oceanography, 75; 751-770.