Nutrient excretion by fish in wetland ecosystems and its potential to support algal production

Zimmer, Kyle D., Brian R. Herwig, Leah M. Laurich

Limnol. Oceanogr., 51(1), 2006, 197-207 | DOI: 10.4319/lo.2006.51.1.0197

ABSTRACT: We used both direct measurement and bioenergetic methods to examine nitrogen and phosphorus (P) excretion by fathead minnows in two wetlands over 2 yr. We also assessed the potential importance of nutrient flux from fish by comparing excretion estimates to empirically derived estimates of algal P demand. Population-level estimates of P excretion across the four lake-years were high relative to other published studies, peaking at 11.7 mg m-3 d-1 and occurring when fish densities exceeded 69 fish m-3. Excretion rates peaked in late summer during maximal algal demand, and P excretion by fish exceeded algal demand in two of the four wetland-years. Detritus was a major diet component (up to 90% by mass), making fish excretion a major nutrient flux from wetland sediments to the water column. Consumer-driven effects could have strong influences on nutrient dynamics in prairie wetlands, ecosystems historically thought to be constrained largely by abiotic factors.

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