For many years Pollutech EnviroQuatics Limited operated a seasonal sediment toxicity laboratory at the Point Edward (Sarnia) biological research station. Recently there has been a significant increase in research and regulatory activity dealing with contaminated sediments of lakes, rivers, and streams. As a result sediment toxicity bioassays have become more important for testing the toxicity and bioavailability of chemical compounds in sediments to benthic organisms.
Sediment bioassays can provide an evaluation of the amount of degradation in an area by utilizing bioassays that examine both lethal and sub lethal effects, as well as chemical bioaccumulation. These bioassays can also provide an estimate of the spatial extent of a degraded area and can determine whether temporal differences have an effect on the bioavailability of toxicants.

Examples of previous work include:

• Sediment toxicity assessments (whole and elutriate preparations) using a multispecies approach (Hyallela azteca, Daphnia magna, Fathead Minnows, Microtox, Hexagenia spp., Chironomus riparius, Tubifex tubifex) integrated with benthic macroinvertebrate assessments and specific sediment chemical analysis.
• Development and implementation of a multitier (chemical, toxicity and benthic macroinvertebrate) study design to determine the spatial extend of St. Clair River sediments classified as degraded as well as determining if the spatial extent of these degraded sediments is undergoing temporal changes. Organisms used for this study included Hexagenia spp., Chironomus riparius, Tubifex tubifex, and Fathead Minnows.

At the present time, the sediment cultures are currently kept at a "minimum" during the winter months. Full-time culturing begins in March and the laboratory is ready for toxicity testing from May to November. As a result of increasing demand for these bioassays plans are being made to expand these culture set-ups to provide these services on a more routine basis. Methods used for the sediment toxicity bioassays follow a draft protocol set out by Environment Canada and the Canada Centre for Inland Waters (CCIW).

Benthic macroinvertebrate assessments often coincide with sediment toxicity testing, and Pollutech EnviroQuatics is fully capable of providing such investigations. We have been successfully conducting benthic macroinvertebrate assessments since 1986 and we look forward to putting our experience to work for you.