Surface Water Quality Status of the Nayaru Lagoon in Sri Lanka and its Impacts on Aquatic Organisms

Lagoon ecosystems are an integral part of the aquaculture and fisheries sector in Sri Lanka. Among the brackish lagoons around the island, Nayaru Lagoon is considered a complex socio-ecological entity of great importance since the economic value provided by the lagoon is mostly associated with the biological production of aquatic animals and plants. The lack of recent and reliable ecological information prevents the authorities from assessing the ecological importance of the lagoon and the possible impacts on Aquatic organisms. Thus, this study, in a preliminary phase, aims to determine the ecological importance of the lagoon, with the objectives of assessing the Physico-chemical parameters of the lagoon water and evaluating the impacts of water quality on aquatic organisms. Water samples were collected from 25 sampling points within the lagoon using a random sampling method, consisting of shallow and deep areas of the entire lagoon and the lagoon mouth. Both in-situ [pH, Water Temperature (WT), Electrical Conductivity (EC), Salinity, Turbidity, Total Dissolved Solids (TDS), and Dissolved Oxygen (DO)] and laboratory analysis [Nutrients and Total Suspended Solids (TSS)] of water samples were carried out using the APHA standard method. Results were compared using standards provided in the Inland water quality guidelines provided in the National Environmental Act 01 of 2019, Sri Lanka. The results showed that pH, WT, and DO levels were within the ambient levels which are suitable for aquatic organisms. However, a significant spatial variation in salinity, TDS and EC levels were identified in the lagoon water samples. A comprehensive study on this lagoon is recommended to understand the seasonal variation in parameters and their collective impacts on the aquatic organisms as a way forward