You are here:
NUTRIENT CONTAMINATION AS A RESULT OF POINT SOURCE DISCHARGES: A SURVEY
Citation:
Lewis, M A. NUTRIENT CONTAMINATION AS A RESULT OF POINT SOURCE DISCHARGES: A SURVEY. Presented at Gulf of Mexico Symposium 2000, Mobile, AL, April 9-12, 2000.
Description:
Nutrients are common contaminants in Gulf of Mexico estuaries and when present in high concentrations, they can cause excessive algal growths and hypoxic conditions. The magnitude and biological significance of nutrient loading to estuarine waters receiving treated wastewaters is not well understood. To provide some insight on this issue, the chemical and biological effects of ten wastewaters and their in-situ impacts were evaluated in a multi-year study. Single species toxicity tests were conducted with the wastewaters and algal and vascular plant test species. In addition, the algal periphyton were colonized below the outfalls at 34 stations and analyzed for biomass and pigment content. Most concentrations of inorganic and organic contaminants in the wastewaters and receiving waters were below action levels for standard water quality criteria but nutrient concentrations were elevated by an average of 96%. Nine of the 10 wastewaters were very phytostimulatory to cultured algae in laboratory bioassays at concentrations of less than 6%. Stimulation of the periphyton was observed below nine of the 10 outfalls; the average increases in ash free dry weight and chlorophyll a were 119% and 288%, respectively. In summary, most wastewaters had in-situ stimulatory effects which are important to consider in the risk assessment process for the many near-coastal areas in the Gulf region that are in an accelerated eutrophic state.