Effect of Water Quality on Community Structure of Bivalve at Segoro Tambak Estuary, Sidoarjo, East Java, Indonesia

Identification of water quality is an important factor because water supports the community structure of an organism. Bivalves are one of bioindicators in aquatic ecosystems in Segoro Tambak Estuary, which receive wastewater from landfill waste disposal. The bivalve community structure needs to be evaluated because the environmental changes that occur in waters can lead to structural changes of the bivalve community. The sampling was conducted in January - March, 2018. The water quality and environmental parameters observed were dissolved oxygen (DO), biochemical oxygen demand (BOD), temperature, salinity, current speed and wind speed. The bivalve community structure can be seen from the composition, diversity (H'), evenness (E) and dominance (C). The results showed that the water quality of Segoro Tambak Estuary was in accordance with the standard of quality of life of marine biota, temperature 28-30.67°C, DO 5.6-5.9 ppm, salinity 29-36 ppt, BOD 44.80 with current speed 0.68-1.81 cm/s and wind speed 2.12-3.72 knots. The dominant bivalve species found in the waters of Segoro Tambak Estuary were Anadara granosa, Anadara inequivalvis, Anadara gubernaculum, Paphia undulata and Mactra sp. The lowest diversity value was observed in January (0.61) and the highest was observed in March (1.38). The highest evenness value observed in March (0.86) and the lowest in January (0.56). The lowest dominance value was seen in February (0.28) and the highest value in January (0.68).