Sediment bioassessment in Halifax Harbour

Abstract

AbstractHalifax Harbour sediments contain heavy metals and organic contaminants. To assess the biological effects of these compounds in the sediment, seven sites spanning a range of known sediment types, water depths, metal levels, and organic contaminant levels were chosen for assessment by a series of tests. Sediment toxicity was measured by the reduction of microbial luminescence (Photobacterium phosphoreum) in three Microtoxr̀ tests (pore water, solvent extract, and solid phase), by the percentages of survival and reburial in two amphipod species (Rhepoxynius abronius and Corophium volutator), and by the survival and change in biomass of juvenile polychaete (Neanthes sp.). Uptake of contaminants from sediment was assessed by a bioaccumulation test, using a bivalve mollusc (Macoma balthica). The chronic effects of the sediment on bottom‐dwelling fish were assessed by histopathological studies on winter flounder (Pseudopleuronectes americanus) collected from the harbor. The results of this study showed detectable biological effects of the Halifax sediments on two (Photobacterium phosphoreum and Rhepoxynius abronius) of the four species of tested organisms. These effects were associated with high concentrations of polynuclear aromatic hydrocarbons (PAHs) in the harbor sediments. The order of sensitivity for the various sediment toxicity tests was Microtox solvent extract = Microtox solid phase > Rhepoxynius abronius > Microtox pore water > Corophium volutator = Neanthes sp. Mortality in Macoma was increased, although no significant uptake of contaminants was detected in the bioaccumulation test. Hepatic lesions were observed in winter flounder collected from the harbor, suggesting a chronic effect of the contaminated harbor sediment.