Ecology of marine amphipods with special emphasis on its use as test organisms for assessing the toxicity of marine sediments

Abstract

This study aimed to examine the feasibility of using indigenous benthic amphipods as test organisms for assessing toxicity of marine sediments. An intensive ecological survey on local amphipods in the coastal environment of Hong Kong was first conducted. Intertidal amphipods (Maera pacifica, Parhyale plumulosa and Srenothoe qingdoensis) associated with macroalgae were recorded from Ma Wan, Sam Mun Tsai, Tai Tam and Wan Chai. It was found that there was significant correlation between the abundance of intertidal amphipods with temperature, salinity and dissolved oxygen in the surface water. Benthic amphipods (Corophium acherusicum, Grandidierlla japonica and Ericthonius sp.) were recorded in sediments collected from Tai Tam and Wan Chai. There was significant correlation between abundance of benthic amphipods and the particle size of the sediment. An indigenous benthic amphipod species. Melita koreana. Stephensen was finally selected for further laboratory studies. Spiked sediment toxicity tests were conducted to test the lethal and sublethal responses of this test species to selected toxicants (ammonia, heavy metals and trace organics). The lethal and sublethal response of the test amphipod species were found directly related to the level of toxicants dosed. 10- day LC50 (median lethal concentration) values of the test amphipod species derived from this study were 9.78 mg/kg (dry weight basis) for cadmium, 104.4 mg/L for ammonia, 365.2 mg/kg per organic carbon for DD1' and 1929.3 mg/kg per organic carbon for total PAHs respectively. A final sediment toxicity test using the local amphipods was conducted to assess the toxicity of four representative sediment samples (Yam 0, Tsing Yi, Port Shelter and Tai Tam) collected in the coastal waters of Hong Kong. Results of sediment toxicity tests indicated that sediments collected from Tsing Yi (a sediment seriously contaminated with copper and nickel and possessing the highest total ammonia and sulphide concentrations) had a significantly higher mortality, higher avoidance and lower reburial ability when compared with the other three sediments collected from Yam 0, Tai Tam and Porter Shelter (sediments with lower levels of heavy metals and trace organics). This reconfirmed that the selected amphipod species has a potential to be further developed for toxicity assessment of Hong Kong marine sediments.