Distribution of Nitrate, Phosphate and N/P Ratio in Maninjau Lake, West Sumatra, Indonesia

This research aim to study of spatial distribution of Nitrate and Phosphate concentration, and also N/P ratio in waters of Maninjau Lake (0°19' S; 100°12'E)), West Sumatera Province, Indonesia, collected from 11 sampling points of water samples which were performed during 3 (three periods) May, June and July 2017. Other major sources of environmental nitrogen and phosphate are fertilizers and wastewater discharged from farms and livestock facilities, and sewage from residential areas which leak into lakes. The Nitrate and phosphate concentrations in Maninjau Lake waters, the results of the analysis found that Nitrate values ranged from 0.02-0.40 mg/L mg/L (quality standard 10 mg/L), while phosphate ranged from 0.12-0.54 mg/L mg/L (quality standard 0.2 mg / L). Nitrogen (N) and phosphorus (P) generally limit the main productivity in lakes. The N/P Ratio calculation results are known that 0.29-0.58, the value shows that there has been an excessive addition of phosphate elements into the waters, so that it appears that the N element is a limiting element that affects the biological conditions of ecosystems such as phytoplankton biomass, species composition which is likely to occur dominance of certain types. This situation is quite reasonable, considering that around the study site is a residential area that discharges household wastewater that uses detergents into the waters. Anthropogenic nitrogen and phosphorus supply to natural ecosystems has increased them in many lakes.