Seasonal nutrient loadings in four monsoonal micro/meso tidal tropical estuaries, west coast of India

Nutrient concentrations were studied seasonally along estuarine and fluvial regions of four micro/meso tidal rivers from Karnataka and Maharashtra, west coast of India. This study was performed to assess the pathway of nutrients across the salinity gradients and evaluate the impacts of weathering and human activity on nutrient concentrations. The rivers of Maharashtra had phosphate concentrations several orders of magnitude higher than the rivers of Karnataka. Nutrient vs salinity plots suggest nutrient addition for Maharashtra rivers and removal in Karnataka rivers. The nutrients in the Karnataka rivers were mostly affected by sewage outfall and anthropogenic activities (industries), while in the Maharashtra rivers, it was influenced by fertilizer application and wastewater discharge. The seasonal nutrient distribution suggests nutrient loadings occurred from the catchments during the wet (monsoon) season in all the rivers. Significant deviations from the Redfield ratio implied occurrences of algal blooms which could threaten those ecosystems.