TOXIC EFFECTS OF DREDGED SEDIMENTS OF HONG-KONG COASTAL WATERS ON CLAMS

The present project is an attempt to study the effects of the sediment s collected from various sites on the survival of three indigenous biv alves (Circe scripta, Gafrarium fumidum and Tapes philippinarium). The preliminary trial revealed that T. philippinarium was more sensitive than the other two species in response to the dredged sediment collect ed from the pollution blackspot: Yau Ma Tei typhoon shelter. A subsequ ent experiment used T. philippinarium to assess the toxicity of sedime nts under different dissolved oxygen regimes (7.8, 8.0 and 8.2 mg L-1) . Significant correlations (p<0.05) were noted between the mortality r ates of the test animals and the total nitrogen and ammonia contents i n the seawater.