Contribution of mollusc culture to control eutrophication in the coastal bay: a case study of Bandon Bay, Surat Thani, Thailand

Abstract

An ecological survey using measurements of water quality parameters was conducted monthly from January to December 1999 at 29 sampling stations in the river mouth, mollusc culture beds, and open bay areas of Bandon Bay. Information on water level, water discharge, wind, nutrients and Chlorophyll a (Chl-a) concentration in Bandon Bay were used to simulate Chl-a concentration and distribution around the mollusc culture area using hydrodynamic and water quality modules of MIKE21 model. The results showed that low conecntration of Chl-a can occur in mollusc culture areas. The difference between simulated and observed values was used to evaluate Chl-a content reduced by molluscs in the culture area. It was found that MIKE21 model can be successfully used to determine Chl-a distribution in reastion to nutrient loading, water discharge and wind conditions in Bandon Bay. The modeling results showed that the simulated Chl-a concentrations in November in the mollusc culture area ranged from 11.2-37.5 µg1^-1  probable due to relatively higher water discharge from river and shrimp farm effluents. The modeling results also showed that Chl-a concentration was approximately 72% lower in the mollusc culture area than in non-mollusc culture areas. These simuated and observed results indicated that mollusc farming can be effectively used to recycle the nutrients discharged from the river and shrimp farms and to control eutrophication in Bandon Bay.