CS35 Trophic Dynamics
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
DrennerRW, Texas Christian University, Ft. Worth, USA, r.drenner@tcu.edu
Hambright, K, D, Oklahoma University Biological Station, Kingston, USA, dhambright@ou.edu
We searched the scientific literature for field experiments and surveys testing the hypothesis that effects of piscivores will cascade down through the food web yielding a decline in phytoplankton biomass. We found 17 non-confounded experiments and surveys examining piscivore effects on phytoplankton biomass. Most (10 of 17) did not detect piscivore effects on phytoplankton biomass and therefore did not support the trophic cascade hypothesis. However, regression analyses of chlorophyll-total phosphorus (chl-TP) relationships found that the slope of the chl-TP regression was lower in lakes with planktivores and piscivores compared with lakes containing only planktivores but no piscivores. Our analysis suggests that the difference between chl-TP ratios in lakes with and without piscivores is greatest in high phosphorus, eutrophic lakes. We hypothesize that the slope of the chl-TP regression can be used as an indicator of “functional piscivory” and that communities with extremes of functional piscivory (zero and very high) represent 3- and 4-trophic level food webs.