HR: 15:30h
AN: NB14E-01 INVITED     [Abstracts]
TI: Eutrophication and Trophic State in Rivers and Streams
AU: * Dodds, W
EM: wkdodds@ksu.edu
AF: Kansas State University, Division of Biology, Manhattan, KS 66506 United States
AB: Given the heterotrophic nature of many natural streams, I propose that trophic state be divided into autotrophic and heterotrophic state. This division requires consideration of external carbon and inorganic nutrients and facilitates a stoichiometric view of lotic trophic structure. Empirical results suggest that phosphorus and nitrogen are the most important nutrients regulating autotrophic state in flowing waters, and that benthic algal biomass is positively correlated to gross primary production. Published estimates of reference nutrient concentrations and nutrient to algal biomass correlations were used to characterize reference distributions of autotrophic state. Mean benthic chlorophyll exceeds 100 mg per square meter less than 30 percent of the time when nutrients are less than the upper third of the expected reference concentrations. A similar analysis suggested that reference nutrient conditions lead to sestonic chlorophyll concentrations above those considered typical of eutrophic lakes less than half the time. Less is known about heterotrophic state, but autotrophic state is probably more variable in small pristine streams than heterotrophic state because autotrophic state is more influenced by canopy (light). Nutrient enrichment often stimulates primary producers and microbial consumers of allochthonous organic materials, so nitrogen and phosphorus enrichment can influence both heterotrophic and autotrophic state.
DE: 1871 Surface water quality
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly