Trophic-level determinants of biomass accumulation in marine ecosystems

Abstract

Metrics representative of key ecosystem processes are required for monitoring and understanding system dynamics, as a function of ecosystem-based fisheries management (EBFM). Useful properties of such indicators should include the ability to capture the range of variation in ecosystem responses to a range of pressures, including anthropogenic (e.g. exploitation pressures) and environmental (e.g. climate pressures), as well as indirect effects (e.g. those related to food web processes). Examining modifications in ecological processes induced by structural changes, however, requires caution because of the inherent uncertainty, long feedback times, and highly nonlinear ecosystem responses to external perturbations. Yet trophodynamic indicators are able to capture important changes in marine ecosystem function as community structures have been altered. One promising family of such metrics explores the changing biomass accumulation in the middle trophic levels (TLs) of marine ecosystems. Here we compared cumulative biomass curves across TLs for a range of northern hemisphere temperate and boreal ecosystems. Our results confirm that sigmoidal patterns are consistent across different ecosystems and, on a broad scale, can be used to detect factors that most influence shifts in the cumulative biomass-TL curves. We conclude that the sigmoidal relationship of biomass accumulation curves over TLs could be another possible indicator useful for the implementation of EBFM. © Inter-Research and Fisheries and Oceans Canada 2012.