Field Verification Program (Aquatic Disposal). The Assessment of Black Rock Harbor Dredged Material Impacts on Laboratory Population Responses.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB
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Studies were conducted to determine the applicability of using population responses to assess the impact of dredged material. Laboratory methods were successfully developed to continuously expose Ampelisca abdita and Mysidopsis bahia to bedded and suspended sediments throughout their life cycle. Biological effects, including survival, individual growth, reproduction, and intrinsic rate of population growth, were measured over a range of exposures to Black Rock Harbor dredged material BRH. Short-term effects 96-hr LC50 were observed at BRH suspended sediment concentrations of 262 mg1 and 80 mg1 for M. bahia and A. abdita, respectively, while the 10-day LC50 for A. abdita was 10.5 mg BRH1. Thus, A. abdita was three times more sensitive to the acute effects of BRH sediment than M. bahia. Acute toxicity in A. abdita was strongly time dependent with 10-day exposures showing an eightfold increase in toxicity compared to the 4-day toxicity data. This may be the result of A. abditas more intimate contact with the contaminated sediments. This study demonstrates that chronic responses are the best predictors of environmental impacts.
- Water Pollution and Control