Development of stressor-response models for an ecological risk assessment case study

An estuarine ecological risk assessment for the Portsmouth Naval Shipyard (Kittery, ME) is being conducted following the US EPA`s Framework for Ecological Risk Assessment (ERA). As part of the Analysis phase of the ERA, laboratory studies were conducted to develop stressor-response models for lead, the primary contaminant of concern. Thirty-day exposures to adult sea urchins, Arbacia punctulata, occurred via food or suspended sediment. Exposure media were amended with lead sulfate to 10--100 or 100--300 times uncontaminated levels for the Feeding or Sediment Experiments, respectively. The sea urchin experimental model was selected because it permitted the measurement of biological endpoints with significance at the population level (e.g., adult survival and reproduction success), including those used in standard marine bioassays (i.e., fertilization and larval development). Feeding Experiment treatments produced few effects. Sediment Experiment treatments resulted in reductions in survival, growth and reproductive output of exposed adults and were directly toxic to early lifestages. However, in uncontaminated sea water, gametes from Sediment Experiment adults fertilized and completed larval development normally. Data from these experimental systems will be used to produce models relating lead exposure to specific biological responses and, ultimately, ecological risk.