Assessing the health of sediment ecosystems: use of chemical measurements

1. This paper outlines the use of chemical measurements as surrogate indicators of the health of sediment ecosystems. 2. For chemical measurements to be used for this purpose, links must be able to be made between adverse biological effects and the chemical composition of sediments. 3. Benchmark sediment quality guidelines allow decisions to be made about whether or not a sediment ecosystem is likely to be impacted. These guidelines are established using an effects database and a weight-of-evidence approach that gives ranges of chemical concentrations associated with known adverse biological effects. 4. If guidelines are exceeded the measured values are compared to concentrations of that contaminant in a comparable background or reference sediment. Exceedance of these concentrations leads to site-specific estimates of contaminant bioavailability. If a potential problem is indicated, laboratory sediment bioassays are used to assess the likelihood that the sediment will harm biota. 5. Trace metals are used as an example of a sediment contaminant.