Abstracts Biological Sciences

The development of preliminary laboratory based culture methods for selected macro-invertebrates used in sediment toxicity testing

by Yolandi Clignet Cloete

Sediments can contain a variety of organic and inorganic contaminants. These contaminants accumulate, resulting in extremely high concentrations even once the overlying water concentrations are at or below acceptable water quality guidelines. Any changes in the physical parameters of the overlying water can cause these pollutants to be released back into solution. Accumulated contaminants can be released at even higher concentrations than previously detected. In recent years, sediment contamination has highlighted the need to monitor these previously overlooked pollutant sources that have accumulated in aquatic ecosystems. South Africa does not currently have standardised methods to assess sediment toxicity. Although international methods exist, they are largely untested in South Africa and the organisms needed to conduct these tests are not readily available. Over the years numerous culture methods have been develop globally for culturing organism to be used for water and sediment toxicity tests. In South Africa, the focus has mainly been on culturing organisms for water toxicity testing. Sediment toxicity testing with indigenous organism however, was not developed. Established international culture methods from the United States Environmental Protection Agency, the Organisation for Economic Cooperation and Development, and Environment Canada were taken into consideration when developing the laboratory culture method for two(2) of the selected organisms (Chironomus spp. & Hydra sp.) from this study. A preliminary culture method was also developed for the third selected organism, Melanoides tuberculata (gastropod). The organisms cultured in this study were selected based on their extent of contact with the substrate, ease of handling, availability, culture maintenance as well as their reproductive cycle. The Hydra, Chironomids and M. tuberculata cultures were successfully breeding under laboratory conditions and remained stable. The Chironomus sp. and M. tuberculata maintain contact with the sediment making them suitable as ecologically relevant organisms for use in whole sediment toxicity testing in South Africa.