Abstract
M.Sc. (Aquatic Health)
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.