Applications of Laboratory Population Responses for Evaluating the Effects of Dredged Material

摘要

Studies were conducted to determine the effect of Black Rock Harbor (BRH) dredged material on the survival, growth, reproduction, and population responses of the benthic amphipod, Ampelisca abdita, and the epibenthic shrimp, Mysidopsis bahia. Exposure system designs are described that permit continuous dosing of suspended solids at concentrations of 300 mg/1 while proportionally mixing contaminated and reference sediments with reliability and precision. Ninety-six-hour LC50 values were 290 mg BRH/1 for M. bahia and 82 mg BRH/1 for A. abdita, with reproducibility and precision being excellent. Chronic exposure indicated that survival was significantly decreased at 150 mg BRH/1 for M. bahia and at 12.5 mg BRH/1 for A. abdita. Growth was a sensitive indicator of stress for A. abdita whose effects were reflected in delays in reproduction in A. abdita but not for M. bahia. Reproduction was the most sensitive chronic response measured for both species. The number of ovigerous females of A. abdita were significantly reduced at 4.0-5.0 mg BRH/1, while the number of young produced in M bahia was reduced at 32 mg BRH/1. The population parameters, intrinsic rate of growth, and multiplication rate per generation measured for M. bahia and A. abdita were significantly depressed at 42 and 4.7 mg BRH/1 sediments, respectively.