Toxicity associated with sediments from Malaysian estuarine environment

Abstract

With the rapid industrialization in the region marine pollution assessment in South East Asia is an ongoing and increasingly important environmental science. One of the areas of concern being sediment toxicology, for it has been identified to be a sink for most pollutants entering the aquatic environment. Owing to the scarcity of information on sediment toxicity bioassays, there is a need to identify species as test organisms for this region. -- For the purposes of this study, an effects based approach known as Sediment Quality Triad was employed, where three components of environmental concern, namely sediment chemistry, sediment bioassays and benthic fauna alterations were investigated at a chosen location. The study area was a portion of coastline in Peninsula Malaysia with three estuaries, two of which, Sg. Juru and Sg. Perai, have been identified as receiving pollutants from the rivers feeding them. The third, Sg. Tambun, was included for comparison purposes. A reference location of minimal or insignificant contamination and reference sediment from a test organism collection site were also tested to obtain background or reference contamination values. Emphasis was placed on the bioassay portion of the triad to observe the applicability of local test animals to obtain reliable data from established toxicity tests and protocols. -- The data for each study site comprising sediment chemistry, sediment bioassays and benthic macroinfauna composition were compiled and normalized to the reference values to obtain ratio-to-reference figures and presented in a triangular format, the area of which depicts the degree of pollution induced degradation. -- Three local species were tested with reference toxicants, the sea urchin (Diadema setosa); oyster (Crassostrea iredalei) and mud crab (Scylla serrata), all had acceptable sensitivity and while the sea urchin was most sensitive to copper while the mud crab was most sensitive to cadmium. With regard to sediment bioassays, an amphipod, Photis longydactylus, seemed very promising for gross sediment testing, while a polychaete worm, Perinereis nuntia, has potential to being amenable for laboratory culture and subsequent use in chronic bioassays. -- The sediment quality of the three sites revealed Sg. Juru to be most polluted and toxic, but the in situ effects on the benthic community needs to be investigated further. Sg. Perai was moderately toxic and is most likely being contaminated by something other than metals. Sg. Tambun was the least polluted, and least toxic, with a better assemblage of benthic fauna.