Sediments from 11 locations within Pamlico Sound, North Carolina were used in a four-day acute toxicity test with Mysidopsis bahia and 10- day acute toxicity tests with Amoelisca abdita, and Neanthes arenaceodentata . Chemical analyses were performed on each sediment sample for selected pesticides, PCBs, total aliphatic and aromatic petroleum hydrocarbons, and heavy metals.

The sediments were not acutely toxic to M. bahia or to N. arenaceodentata in the 10-day acute tests. Four sediments caused a statistically significant reduction in mean percentage survival of A. abdita when data were analyzed with the t-test: Hancock Creek (p = 0.0545) and E. Prong Slocwn Creek, Kennedy creek, and oriental Harbor (p < 0.05). Mortality ranged from 12 to 37%.

Mean percentage survival in Kennedy creek sediment (94%) was higher than the mean percentage survival in other sediments that did not cause statistically significant reduction in survival. This statistical difference is attributed to the variances differing among the locations tested: 0.200 for Kennedy Creek, 1.80 for Middle Pamlico River, and 4.20 for Upper Slocum Creek.

The reasons for the acute toxicity are not known. However sediment from E. Prong Slocum Creek SLO (18- 19) contained much higher concentrations of total petroleum hydrocarbons than any of the other sediments (3680 ~g/g dry weight). Based on these acute toxicity tests, we believe the survival of Ampelisca in sediments from E. Prong Slocum creek, Kennedy Creek, Hancock Creek, and Oriental Harbor could be reduced if exposure is 10 days, and that benthic life may be adversely affected at these locations.

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