Nutrients retention function indications in the water quality of the floodplain area on the lower Batanghari River

Abstract

The Lower Batanghari River often experiences mass deaths of fish. This could be a symptom of eutrophication caused by nutrient enrichment in the water bodies. Floodplain areas are important in reducing parts of these nutrient loadings. This study aimed to examine water qualities related to the nutrient retention function within the Batanghari River floodplain ecosystem. A sampling expedition was conducted in April-May 2021, during a dry season transition period. Sampling was conducted at 20 sampling points stretching over +200 km long within the river and its tributaries. These sampling points were categorized as main river channels, tributaries, and floodplain swamps and lakes. The water quality parameters measured were temperature, pH, conductivity, dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), and total organic matter (TOM). The main river TP concentrations ranged from 0.21-0.33 mg/L, suitable for fishery activities. The overall sampling point groups have distinct characteristics regarding their DO, TP, and TOM values. The average TP in floodplain lakes was found significantly lower (t(13)=8.636, p<0.05) than in the river. Meanwhile, a decrease in TN up to 90% was also found in its lower main river channel. These lower nutrient concentrations along the river floodplain gradients indicate a nutrient retention function. Thus, to reduce eutrophication impacts, floodplain conservation is becoming important.