Toxicity delayed in cold freshwaters?

There is increasing evidence of a delay in the manifestation of toxicity with exposure to contaminants and other stressors in polar (Arctic and Antarctic) marine environments. This phenomenon has not been shown to occur in cold (i.e., < 4 °C) freshwater environments. Toxicity testing protocols have not been designed to investigate the existence of this phenomenon; toxicity testing is typically conducted in the laboratory at warmer than ambient cold water temperatures (i.e., 10-15 °C) and for pre-determined time periods. The hypothesis of delayed toxicity in cold freshwaters is viable based on a review of available literature; this hypothesis should be tested. If this phenomenon occurs in cold freshwaters (i.e., northern, southern, and high altitude freshwaters), and if the exposure period is not adequate to account for a delayed response, sensitivity to tested toxicants under cold water conditions may not be adequately estimated, resulting in an underestimation of toxicity and an overestimation of predicted no effect concentrations.