Sediment Quality Triad Assessment in Kachemak Bay: Characterization of Soft Bottom Benthic Habitats and Contaminant Bioeffects Assessment. North Pacific Research Board Project Final Report

摘要

A baseline environmental characterization of inner Kachemak Bay, Alaska was conducted using the sediment quality triad approach based on sediment chemistry, sediment toxicity, and benthic invertebrate community structure. The study area was subdivided into 5 strata based on geophysical and hydrodynamic patterns (eastern and western intertidal mud flats, eastern and western subtidal, and Homer Harbor). Within each stratum, a stratified random sampling approach was used to select sampling sites for surficial sediment. Concentrations of over 120 organic contaminants and metals were analyzed. Ambient toxicity was assessed using two amphipod bioassays. Habitat conditions (depth, salinity, temperature, dissolved oxygen, sediment grain size, and organic carbon content) were also measured. Organic contaminants including PAHs were low relative to NOAA's sediment quality guidelines (SQG). Metal concentrations were below SQGs in all but one case. Tributyltin was elevated in Homer Harbor relative to the other strata. Diverse assemblages of benthos were collected with more than 240 taxa recorded and abundances greater than 3,000 animals m-2 at most locations. Species richness and diversity was lower in the eastern end near the Fox River input. Abundance was also lower in the east end of the bay, and in the intertidal areas near Homer. Benthic macroinfauna communities in the eastern portions of the bay appeared stressed by the sediment load from glacial meltwater, but significant chemical toxicity was virtually absent.