Effects of a spill of marine diesel oil on the rocky shore fauna of Lamma Island, Hong Kong

Abstract

The acute toxic and long-term ecological effects of marine diesel oil on common littoral fauna were studied at three rocky shores on Lamma Island, Hong Kong, which were contaminated to different degrees. Acuite mortality of gastropods was greatest at the moderately contaminated site where oil-dispersant chemicals were applied to floating slicks nearby, but long-term disturbances were most significant at the heavily oiled site where dispersants were not used. Animals were collected on the oiled beaches and taken to the laboratory, where their recovery in clean seawater was studied. This indicated that bivalve molluscs and the gastropods Monodonta labio and Thais clavigera were the most sensitive and Clypeomorus humilis and Planaxis sulcatus the least. Field observations of acute mortality were consistent with this order of species sensitivity. The greatest population reduction was observed in Monodonta labio and Nerita albicilla which were eliminated for at least 13 months from the site receiving the most oil. Species resistant to oil in recovery experiments did not show significant long-term reductions.