<![CDATA[Lembar Bay is a coastal ecosystem utilized for fisheries, port activities, aquaculture, and human settlements, making it vulnerable to changes in water quality due to natural and anthropogenic nutrient inputs. This study aimed to analyze nitrate, nitrite, and orthophosphate concentrations as indicators of water quality in Lembar Bay, West Lombok, Indonesia. A quantitative descriptive method was employed by collecting seawater samples from five sampling stations representing mangrove, open coastal, port, traditional aquaculture, and residential areas during May 2026. Water samples were analyzed for nitrate, nitrite, and orthophosphate concentrations, while water temperature, salinity, and pH were measured as supporting physicochemical parameters. The results showed that nitrate concentrations ranged from 0.02 to 0.07 mg/L, nitrite from 0.001 to 0.009 mg/L, and orthophosphate from 0.001 to 0.06 mg/L. Nitrate concentrations were relatively high compared with the marine water quality standard for aquatic biota, particularly in the mangrove area, indicating substantial nutrient inputs from organic matter decomposition and terrestrial runoff. In contrast, nitrite concentrations remained low, suggesting that nitrogen transformation processes were functioning efficiently, while orthophosphate concentrations reflected low to moderate trophic conditions that were still capable of supporting primary productivity. Overall, the water quality of Lembar Bay remains suitable for sustaining aquatic organisms. However, the elevated nitrate concentration highlights the need for continuous monitoring and effective nutrient management to prevent eutrophication and maintain the ecological sustainability of the coastal ecosystem.]]>
