Research Areas > Contaminants > Direct Effects in Bays > Development of Toxicity Indicators

Project Component: Development of Toxicity Indicators

Background and Objectives

Toxicity tests provide an integrated measure of exposure to multiple chemicals. They evaluate the combined effect of all contaminants present in the sample, as well as the influence of environmental factors that alter contaminant bioavailability. Toxicity tests have been widely used to assess sediment quality in a variety of research, monitoring, and regulatory programs. While many programs follow standardized protocols, variation remains among programs in the selection of test methods and the way data are interpreted. This is problematic when developing a sediment quality assessment program with broad applicability.

This study had two objectives: (1) to evaluate a variety of acute and sublethal toxicity tests in order to identify the methods best suited for use in a statewide regulatory program, and (2) to develop a system for classifying toxicity test results into a series of sediment quality effect categories.

Status

This study was completed in 2008.

Methods

SCCWRP researchers evaluated seven toxicity test methods to identify those best suited for use in a statewide monitoring program:

• Acute amphipod survival
• Polychaete worm growth
• Seed clam growth
• Amphipod growth
• Mussel embryo development
• Copepod growth and reproduction
• Oyster cell stability

The relative sensitivity of the methods was evaluated across samples of sediment from 15 locations. Additional data on the feasibility, sensitivity, variability, and cost of each candidate method were obtained from the literature. The data were compiled into a matrix of test characteristics, and the methods were scored based on their relative performance.

Findings

A wide range of responsiveness was observed among methods. The copepod and polychaete tests showed the greatest responses to the sediment samples. Some of the sublethal tests identified fewer stations as toxic compared to the standard amphipod survival test; however, each of the sublethal tests detected toxicity in at least one sample that was classified as nontoxic by the amphipod survival test. This suggests that sublethal tests and acute tests are complementary rather than redundant. The following five tests were identified as best suited for use in a California statewide sediment quality assessment program:

The use of multiple toxicity tests to assess sediment quality is suggested, as none of the test methods was consistently high-ranking in terms of sensitivity and reliability. The use of a diversity of test methods provides two key advantages. First, it reduces the influence of spurious results from a single test. Second, it increases the overall sensitivity of the testing program by using species with different patterns of contaminant sensitivity.

Partners

Marine Pollution Studies Laboratory of the University of California Davis

Tools

• Direct Effects Assessment Sample Calculation - Document describing the calculations needed to interpret chemistry, toxicity, and benthic infauna data for sediment quality assessment. Calculations are illustrated using a sample data set.