The response of benthic algal biomass to nutrient addition over a range of current speeds in an oligotrophic river

Current speed could affect algal responses to river eutrophication and flow regulation via its influence on nutrient availability to benthic algae. In laboratory experiments, the thickness of the diffusive boundary layer decreases with increasing current speed, enhancing rates of nutrient mass transfer by molecular diffusion across the layer to the algal cell wall. In rivers and streams, this phenomenon may be masked by grazing and physical losses. We used a 10-wk field experiment to test the hypothesis that the response of benthic algae to nutrient addition was a function of current speed. We deployed clay pavers at the beginning of a 3-mo period of baseflow in the Daly River (tropical Australia) at 5 sites (current speeds