Acute toxic effect of sewage effluent on the early life phase of an estuarine crab Scylla serrata

The biological quality of secondary treated sewage effluent was evaluated using a toolbox approach, which combined a larval developmental bioassay and measurement of fecal indicator organisms. The zoea developmental toxicity of Scylla serrata from stage I to stage II was determined by exposing to a range of secondary treated sewage concentrations. Results indicated that the relative progress of zoea stage I to zoea stage II negatively correlated with increasing sewage concentrations. Data was analyzed statistically to determine lethal, median lethal, sublethal, low observed effect, and no observed effect concentrations. Water samples collected along the Buckingham canal discharge zone were also analyzed for its toxicity to the larval development. Fecal indicator organisms chosen to determine the water quality were E. coli, enterococci, C. perfrigens, and F+ coliphages. Concentrations of these fecal markers were determined in the raw influent, primary treated effluent, secondary treated effluent, and in four discharge zone sites. Data showed that this biological toolbox is helpful for providing baseline information on the effectiveness of the wastewater treatment and environmental health of the discharge zone.