Suspended Sediment Concentration and its Impact on Aquatic Invertebrates in the Gin River, Sri Lanka

Understanding the level of suspended sediment is important for the management of aquatic fauna and flora. This study focused on the impact of suspended sediment concentration (SSC) on aquatic invertebrates in the basin of Gin river, Sri Lanka. Sixteen sampling locations along the river basin were used for data collection. Water temperature, dissolved oxygen, pH, electrical conductivity, turbidity and SSC were determined using standard laboratory methods. Aquatic invertebrates were collected using Kick sampling and stone lifting methods and they were identified using keys. Statistical analyses were done by Principal Component Analysis, factor analysis and descriptive analysis techniques. The water temperature and dissolved oxygen concentration in the Gin river basin were 25.76 ± 2.4 °C and 6.85 ± 6.1 mg/l (mean ± SD), respectively. The mean turbidity in the basin was 10.09 ± 16.1 NTU (mean ± SD). The SSC increased towards middle and lower catchments. Thirty nine different aquatic invertebrate taxa were recorded. A higher diversity of aquatic invertebrates was recorded with lower SSC in upper catchment. A negative relationship was evident between SSC and number of aquatic invertebrate species. High SSC had a negative impact on aquatic invertebrate diversity in the Gin river basin. A positive correlation was present between SSC and turbidity and therefore, a model was developed to predict SSC using turbidity data.