Predators reduce carbon production in multi-trophic level marine ecosystems
Authors: Stafford, R. and Spiers, E.K.A.
Start date: 13 December 2015
While the effects of climate change on top predators are well documented, the role of predation on ecosystem level carbon production is poorly developed, despite it being a logical consequence of trophic dynamics. Trophic cascade effects have shown predator mediated changes in primary production, but we predict that predators should lower the overall biomass capacity of any system with top down control. Through a variety of models of typical marine foodwebs, we show that predator removal, as is common through activities such as fishing and shark finning, results in higher biomasses of lower trophic level fish and zooplankton, resulting in higher net carbon production by the system. This is offset only slightly by a possible decrease in phytoplankton. Trophic cascade effects are not obvious when multiple levels of predators are removed from the system, as per standard fishing practices. Such results provide even more strength to the argument to protect open sea fish stocks, and particularly large predators such as sharks, cetaceans and game fish.