Assessing the health of sediment ecosystems: use of chemical measurements

1. This paper outlines the use of chemical measurements as surrogate indica tors of the health of sediment ecosystems. 2. For chemical measurements to be used for this purpose, links must be abl e to be made between adverse biological effects and the chemical compositio n of sediments. 3. Benchmark sediment quality guidelines allow decisions to be made about w hether or not a sediment ecosystem is likely to be impacted. These guidelin es are established using an effects database and a weight-of-evidence appro ach that gives ranges of chemical concentrations associated with known adve rse biological effects. 4. If guidelines are exceeded the measured values are compared to concentra tions of that contaminant in a comparable background or reference sediment. Exceedance of these concentrations leads to site-specific estimates of con taminant bioavailability. If a potential problem is indicated, laboratory s ediment 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.