Ecosystem response to benthic-derived nutrient subsidies from omnivorous fish

Fish are important in coupling benthic and pelagic habitats by consuming benthic prey and providing essential nutrients (nitrogen-N and phosphorus-P) to algae. However, because a complete understanding of fish effects on nutrient dynamics is still lacking, I measured how fish excretion rates (N and P) are affected by variable consumption rates under laboratory and field conditions and how these changes in excretion rates affected community and nutrient dynamics. Results showed that variable consumption rates can alter fish excretion rates of nutrients and that algal biomass and sedimentation increased when fish fed on benthic prey, compared to fish not fed benthic prey. This study provided experimental evidence that benthic-pelagic coupling, via fish induced translocation and sedimentation shapes pelagic food-webs and cycling of nutrients between pelagic and benthic habitats. Lastly, fish body and excreted N:P both increased with consumption rate, suggesting that stoichiometry models need to incorporate consumption rate.