Aquatic Sciences Meeting, Albuquerque 2001

SS19 Revisiting Redfield: C:N:P Stoichiometry in Aquatic Ecosystems (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 4:15:00 PM

Location: Acoma/Zuni/Tesuque

Vanni, M, J, Miami University, Oxford, Ohio, USA, vannimj@muohio.edu

Flecker, A, S, Cornell University, Ithaca, New York, USA, asf3@cornell.edu

Hood, J, M, Miami University, Oxford, Ohio, USA, hoodj@muohio.edu

Knoll, L, B, Miami University, Oxford, Ohio, USA, knolllb@muohio.edu

Braitman, L, S, Cornell University, Ithaca, New York, USA, lsb9@cornell.edu

NUTRIENT RECYCLING BY CONSUMERS IN A TROPICAL STREAM: INTERSPECIFIC VARIATION AND IMPACTS ON ALGAL STOICHIOMETRY

We examined variation in nutrient recycling by 25 fish and 2 tadpole species in a tropical Venezuela stream. Mass-specific nitrogen and phophorus excretion rates, and N:P ratio excreted, each varied more than ten-fold among species. Rates were negatively correlated with body mass, but body P content explained more interspecific variation in P excretion rate. Together, body P and mass explained 60% of the variance. Body P content was related to phylogenetic identity. Armored catfish (Loricariidae) had the highest body P (>5% dry mass), lowest P excretion rates, and highest N:P ratio excreted; tadpoles had the lowest body P (<1%) and highest P excretion rates. N excretion was unrelated to body N. In a mesocosm experiment, stream periphyton exposed to nutrients recycled by armored catfish had lower C:N ratios (15 vs. 11), but higher C:P (200 vs. 150) and N:P (17 vs. 10) ratios than periphyton not exposed to recycling. This suggests that armored catfish reduce N-limitation but increase P-limitation, as predicted by excretion rates. Our results suggest a phylogenetic constraint on interspecific variation in the stoichiometry of consumer-mediated nutrient cycling.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks