Environment impacts of undulated surf clam dredging operation off Prachaup Kirikharn province, Thailand

Abstract

Environment impacts of experimental dredging operations for the undulated surf clam, Paphia sp. around Paknam-Pran and adjacent coastal areas (Amphur Pranburi and Amphur Sam-roi-yod, Prachaup Khirikhan Province, Thailand) were investigated in collaboration with Department of Fisheries, Thailand. Data were collected on physical parameters from water samples at surface layer (30 cm below sea surface), and nutrient parameters from surface as well as overlying water (50 cm above bottom sediment level). Results show that water quality changed by dredging operation in the following ways: the most significant impact was increase in Total Suspended Solids (TSS), and consequently, decrease in water transparency. Dissolved oxygen concentration was marginally higher in several stations after dredging, possibly due to disturbance caused by dredge boat propellers. Concentrations of Ammonium-Nitrogen (NH4+-N), Silicate-Silicon (Si(OH)4-Si) and Orthophosphate-Phosphorus (PO43--P) marginally increased in almost all stations after dredging. There is a possibility that increase in nutrient concentration may lead to occurrence of red tide during and after the surf clam dredge fishing season.