Distribution of Foraminifera in the Setiu Estuary and Lagoon, Terengganu, Malaysia

The Setiu wetland of peninsular Malaysia is threatened by expansion of aquaculture. Water quality of the estuary-lagoon complex is becoming affected by nutrients introduced into the system at floating fish cages and by the clear-cutting of large areas of fringing mangrove forest for the creation of land-based fish and shrimp pens. We report here on the distribution of benthic foraminifera in the estuary-lagoon and related environmental variables. These data will form the baseline against which future environmental monitoring will be compared. Four thanatofacies are recognized by cluster analysis of the dead foraminiferal abundance data; their distribution is closely related to variations in salinity and other parameters related to the hydrodynamics of the region. This relation is confirmed by DCA and DCCA analyses. A low salinity estuarine thanatofacies (D1) has a low diversity assemblage dominated by the agglutinated taxa Ammotium directum, Trochammina amnicola, Miliammina fusca and Ammobaculites exiguus. A medium salinity lagoon thanatofacies (D2) has low diversity and is strongly dominated by the agglutinated Ammobaculites exiguus. Ammobaculites exiguus and Ammonia aff. A. aoteana dominate a high diversity, high salinity thanatofacies (D3) in both the estuary and the lagoon. A normal marine salinity thanatofacies (D4), found at an inlet and in the immediately adjacent lagoon, has a high diversity assemblage dominated by the calcareous taxa Amphistegina lessonii and Ammonia aff. A. aoteana. Five biofacies recognized by cluster analysis of live foraminiferal data exhibit similar salinity-related distribution patterns as the thanatofacies.