Acute and sublethal effects of cadmium on ingestion, egg production and life-cycle development in the copepod Acartia tonsa

The acute toxicity of cadmium (expressed as 96-h LC,,) to the suspension-feeding copepod Acartia tonsa was highly influenced by temperature.The LC,,-value was 151 ppb Cd at 13'C, but only 29 ppb Cd at 21 "C.Salinity influenced the toxicity of cadmium.At 40 ppb Cd the clearance of algal cells (Rhodomonas baltica) was reduced at 9 and 17 %O S, but not at 25 Ym S.There was a tendency to reduction of both algal cell ingestion and egg production at cadmium concentrations above 10 ppb, and the reduction was significant above 30 ppb.The development of copepodites and adults was influenced by both salinity (9, 17 and 25 i S) and cadmium (5, 10 and 40 ppb).The general tendency was increasingly longer developmental time at higher salinities and higher cadmium concentrations.The quickest development took place at 17 %a S and no cadmium whlch was probably a consequence of genetic adaptation to intermediate salinity.The slowest development was observed at 25 %a S and 40 ppb Cd where the cephalothoracic length in adult copepods was significantly reduced.Adult fertdized egg-producing females developed under all experimental conditions, and it is concluded that the 96-h LCS0 values were close to the higher sublethal concentrations of Cd which reduced ingestion, egg production and developmental time, but allowed the copepod to accomplish an entire life-cycle.