Wetlands act as the kidneys of the landscape (Mitsch and Gosselink, 1993) by enhancing the water quality that flows through them. However, the role of wetlands in surface water purification has been less studied globally (Verhoeven et al., 2006). In developing countries like India, where the level of water pollution and sedimentation is high, floodplain wetlands may be playing an important role in the surface water purification. To understand this, we selected Chatla— a seasonal floodplain wetland located in the Barak river basin of Assam, northeast India. We studied vegetation, surface water, soil and sediments of the wetland during the early-, mid-, and late-flood phases in the years 2014 and 2015. Sampling was done at five stations considering the major inlet points, middle points and outlet point along the wetland. Standard methods were followed to measure depth & area, and to analyze the physico-chemical properties of water, soil & sediments (at 0-15 cm depth) of the wetland. Besides, water quality index (WQI), trophic state index (TSI), nutrient retention efficiency (NRE) of the wetland, and the macronutrient stock in wetland vegetation i.e., total nitrogen (TN) and total phosphorus (TP) were also estimated.
Results/Conclusions
The present study highlights the role of the structural components of Chatla wetland viz., soil, sediment, and wetland vegetation in sequestering nutrients from the surface water. This is evident from the fact that WQI and TSI improved at the outlet point of the wetland as compared to its inlet and the middle points. Also, the nutrient load of water at the outlet point was lower compared to the inlet points indicating good NRE of Chatla wetland. TN and TP stock of wetland vegetation was highest in inlet point and lowest in the outlet point suggesting its role in nutrient sequestration. This is mainly because of higher nutrient content in both surface water column and vegetation biomass in the inlet points as compared to the outlet point of the wetland. The study also revealed that the wetland is more efficient in retaining nitrate-N in its sediment compared to phosphate-P. Thus, Chatla wetland plays a significant role in the purification of the surface water through its various structural components highlighting the regulating ecosystem service attribute of the wetland.