Effects of Sediment Loading on Food Perception and Ingestion by Freshwater Copepods

Seasonal influx of suspended sediments to lakes is common in many aquatic systems, particularly during periods of high flow. Suspended particles not only affect visibility and net primary productivity, as light penetration is reduced, but may also affect the ability of herbivorous zooplankton to locate and ingest food. In Swan Lake, an oligotrophic lake in northwestern Montana, the dose association between zooplankton population development and seasonal maxima in turbidity levels suggests that the community present during peak turbidity is minimally impacted by suspended sediments. This report presents the results of laboratory investigations into the effect of suspended sediments on feeding by the copepod Diaptomus ashlandii, the dominant zoo‐plankter in Swan Lake. Ingestion rate for copepods feeding on 32P labeled algae was significantly reduced in the presence of suspended particles at all turbidity levels tested (5 to 200 NTU's) compared to ingestion rate in the absence of suspended particles (0 NTU's).