Individual and combined effects of temperature and polychlorinated biphenyls on the growth of three species of phytoplankton

Two marine diatoms and a marine green alga, grown in axenic batch cultures, were exposed to polychlorinated biphenyls (PCBs) at different temperatures. PCBs did not affect the green alga's growth rate but did inhibit the growth of both diatoms. One of these, Rhizosolenia setigera, was affected by concentrations of PCBs as low as 0·1 part per thousand million. Sensitivity of both diatoms to PCBs was highly dependent on temperature; PCB toxicity increased as the temperature tolerance limits for each species were approached. The data suggest that phytoplankton growing under suboptional condition may be more vulnerable to stress than when growing under optimal conditions.