Marine sediment conservation using benthic organisms

Estuaries and coastal zones used for fish aquaculture are often polluted by organic contaminants and anthropogenic chemicals. Bioremediation has been recognized as an efficient technology to clear environmental pollutants. The authors therefore studied environmental remediation using benthic organisms and have shown that some annelids are adaptable polluted environments. For example, Capitella cf. teleta, a polychaete inhabiting the sediment beneath a fish farm, displayed high protease activity, whereas Perinereis nuntia, a polychaete inhabiting an estuary, displayed high cellulase activity. Additionally, the oligochaete Thalassodrilides cf. briani was found to survive highly hypoxic and sulfidic sediments contaminated with various pollutants and was shown to biotransform 1-nitronaphthalene, a toxic and carcinogenic chemical, into substances that are nontoxic to fish. In another experiment in which these three benthic species were maintained in polluted sediments, the polychaete P. nuntia and C. cf. teleta markedly increased redox potential (Eh) and decreased the level of acid volatile sulfides relative to the oligochaete T cf. briani. Furthermore, the concentration of polycyclic aromatic hydrocarbons (PAHs) in the sediment with all three species was significantly lower than the initial level. T cf. briani, especially, showed a marked ability to degrade the PAHs in the sediment. These results indicate that benthic organisms have species-specific remediation properties and ecological functions in organically polluted sediments. We are also working on the development of a real-time measuring device for determining the Eh in the sediment under fish farms as Eh is a comprehensive parameter to monitor the degree of contamination of these sediments.