ABSTRACT 
EVALUATION OF CHESTER RIVER MORTALITY BIOTOXICITY 
i, 
Three studies were performed to determine whether the recent 
dieoffs of oysters in the Chester River can be correlated with 
point sources of toxic substances. To this end two kinds of ex¬ 
periments were performed: long-term experiments with oysters 
placed in the Chester River; and 96-hour acute toxicity experi¬ 
ments with golden shiners, Notemigo nus chrysoleucas, and cravfish. 
Procambarus acutus acutus . - 
In the long-term studies, 10 stations were established. 
Three stations were below the areas of known oysterkills, four 
were within the areas of recent oysterkills and three were in 
areas where the kills occurred in 1974 and 1975. One or two trays 
with 96 oyster specimens were placed at each station. Ten or 
twelve oysters were removed at nine intervals during 4 months. 
These were scored for condition. No significant mortality occur¬ 
red during this period, but during July and August 1978 the five 
stations most upriver had dieoff of the fouling organisms and 
reduced growth rates of the oysters. 
The 96—hour acute toxicity studies were performed by placing 
cages of golden shiners and crayfish in streams receiving ef¬ 
fluents from the Campbell's Soup plant, the Tenneco, Inc. plant 
and the sewage treatment plant for the city of Chestertown. No 
significant mortality occurred. 
No point sources of toxicants were located, but since no 
significant mortality occurred during the study these results are 
not conclusive. 
PHTHALATE ESTERS AND RELATED CHEMICALS IN THE CHESTER RIVER BASIN 
The Tenneco factory on Morgan Creek is permitted to discharge 
up to 2830 kg of organic extractables per year. These waste 
chemicals empty into the adjacent Tenneco Pond with a residence 
time of ca. 10^ days. The pond discharge flows through Morgan 
Creek into the Chester River. The residence time in the river is 
a much shorter 130 days. 
Model concepts based on available data allow plausible calcu¬ 
lations of discharge organics in the contiguous downstream sedi¬ 
ments. The possibilities range from 0.04 ppm based on simple 
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