Effects of suspended sediments on reproductive responses of Paracalanus sp. (Copepoda: Calanoida) in the laboratory

Abstract

The ingestion rate, egg production, egg-hatching success and survival rate of adult female copepods, Paracalanus sp., in relation to a suspended sediment concentration gradient (control: 0 mg L, low: 10 mg L, middle: 30 mg L and high: 100 mg L) were examined in the laboratory under two concentrations (1 10 and 1 10 cells mL) of the dinoflagellate Prorocentrum minimum to understand the impacts of turbidity on the reproductive responses. Ingestion rates under both phytoplankton concentrations were significantly lower at high level of suspended sediments than at the control level. The egg production rate at the low phytoplankton concentration also decreased with increasing suspended sediment concentration, but there was no effect of suspended sediment on egg production at the high phytoplankton concentration. Egg-hatching success was relatively high at .90%; thus, there was no deleterious effect of suspended sediments on egg viability. The survival rate of adult females decreased with time in all treatments, indicating no negative effects of suspended sediments on the mortality of female copepods. These results suggest that higher concentrations of suspended sediments might have negative effects on copepod recruitment in the field. Feeding efficiency on phytoplankton decreased in the presence of suspended sediments, thus potentially decreasing the copepod egg production rate. However, the negative effects may be lessened if the copepod ingests more food in terms of both quality and quantity in favorable food environments.