Nutrient excretion by fish supports a variable but significant proportion of lake primary productivity over 15 years

Animals play an important and sometimes overlooked role in nutrient cycling. The of animals cycling is spatially temporally variable, but few studies have evaluated the long-term importance animal-mediated meeting demand by primary producers. We quantified proportion phytoplankton (phosphorus, P) met excretion gizzard shad (Dorosoma cepedianum) a eutrophic reservoir where this species dominates fish biomass. From 2000 to 2014, supported variable P demand, averaging 7–27% among years over growing season (spring summer). Temporal patterns emerged, as consistently higher during summer (mean 31%) than spring (8%). In spring, from was best predicted population biomass, stream discharge, temperature. summer, only biomass young-of-year (YOY) shad. Thus, variation YOY significantly alters supply, future should explore animal dynamics Our study shows that several data are needed perform critical evaluation ecosystem demand.