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EXPECTED EFFECTS OF RESIDUAL CHLORINE AND NITROGEN IN SEWAGE EFFLUENT ON THE ESTUARINE ECOSYSTEM OF GREENWICH COVE, RI: AN ENERGY SYSTEMS AND RISK ASSESSMENT OF EFFECTS
Citation:
Campbell, D E., D. Hattis, AND E H. Dettmann. EXPECTED EFFECTS OF RESIDUAL CHLORINE AND NITROGEN IN SEWAGE EFFLUENT ON THE ESTUARINE ECOSYSTEM OF GREENWICH COVE, RI: AN ENERGY SYSTEMS AND RISK ASSESSMENT OF EFFECTS. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Baltimore, MD, November 11-15, 2001.
Description:
Physical, toxicological, and energy systems modeling were combined to make estimates of likely ecosystem-level effects due to residual chlorine in sewage effluent. The energy systems model also allowed us to make estimates of the effects of nutrient loading on the estuary both separately and combined with the toxic effects of residual chlorine. We have developed, and adapted for use in risk assessment, an energy systems model of the pelagic biota of Narragansett Bay. This allowed us to assess the indirect implications of toxic effects on one type of organism for other organisms at the same or different trophic levels in the ecosystem. We also used emergy accounting to compare the relative magnitude of these direct and indirect effects across trophic levels. We found that indirect food web mediated effects were likely to be the primary mode of loss for one important species of interest (bluefish), but not for another (menhaden). Organism responses were modeled by assuming that lethal toxic responses occur as individual organism thresholds are exceeded, and that in general these thresholds are log-normally distributed in a population of mixed individuals. In the ecosystem model, temperature is integrally incorporated into the functions determining metabolic rates, reproduction, respiration, gross primary production, bacterial recycling of nutrients, etc. Our models project a greater potential for toxicity in the warmer summer months, even though expected concentrations of chlorine in the receiving waters averaged only a third of those expected in the winter. The major dependence of so many model elements on temperature indicates a general need for researchers to record and report temperatures whenever observations are made that may be used to assess risk to estuaries and other coastal ecosystems. This basic practice is not universally followed at present.