*Corresponding author Email address: somsakry@gmail.com Songklanakarin J. Sci. Technol. 43 (1), 195-202, Jan. - Feb. 2021 Original Article Distribution of aquatic plants in Nong Han wetland, Thailand Somsak Rayan*, Saifon Kaewdonree, Amornrat Rangsiwiwat, and Boontiwa Chartchumni Faculty of Natural Resources, Rajamangala University of Technology Isan, Sakon Nakhon Campus, Phang Khon, Sakon Nakhon, 47160 Thailand Received: 26 August 2019; Accepted: 2 December 2019 Abstract Aquatic plants are regarded as primary producers that play a significant role in the ecosystem. Thus, the distribution of aquatic plants has a substantial impact on aquatic organisms. The purpose of this research was to study the spatio-temporal variation of the distribution of aquatic plants in Nong Han wetland, Thailand. According to the results, there were 31 species and 22 families of aquatic plants in Nong Han wetlands with the mean biomass of 13,991.44 g m -2 ; where by Potamogeton malaianus Miq was the dominant species with highest biomass. In addition, the central wetland to the east had the highest amount biomass, and the period between February and April had the greatest influence on the biomass of aquatic plants. Moreover, the mean value of chlorophyll-a was found to be 0.021±0.014 mg l -1 , indicating a high eutrophic level. Eichhornia crassipes and Salvinia cucullatas were invasive species with the tendency to cause damage to the water body in the future. Accordingly, to maintain ecological balance and sustainable output, stakeholders should implement preventive measures, eliminate invasive plants, and reduce the discharge of organic substances which are the source of plant nutrients into the water body. Keywords: aquatic plants, biomass, distribution, Nong Han wetland 1. Introduction Nong Han wetland is the largest freshwater lake in the northeastern region of Thailand and is regarded as one of the natural lagoons of international importance, covering a total area of 123 km 2 (Office of Environmental Policy and Planning, 2002). Nong Han wetland provides multiple benefits to the surrounding communities by serving as a water storage area for agriculture and livestock farming, a source of water supply, a tourist attraction, and a site for aquaculture. In addition, Nong Han wetland also accommodates fishery activities that provide income and food security to the communities (Kunlapapuk, Kulabtong, & Soontornkit, 2014; Pengsangsee & Kaewnern, 2014; Rayan, Chartchumni, Kaewdonree, & Rayan, In Press). Aquatic plants are considered an important resource of fishery on account of the fact that they are primary producers and fundamental components of the food chain in an aquatic ecosystem. Indeed, aquatic plants play a significant role in both physical and chemical processes; they serve as habitats, sources of food, hiding sites, and breeding sites for aquatic organisms (Nagmsnae, 2011). The distribution patterns of aquatic plants tend to vary over time. Meanwhile, the variability of nutrients and waterbed materials significantly contribute to the varia- tion of aquatic plant species in a water body (Pieczynska, 1990). Furthermore, an appropriate amount of aquatic plants is essential for maintaining ecological balance of a water body, hence creating suitable habitats for aquatic organisms and enabling humans to fully utilize the water body (Sripen, 1999). Aquatic plants are highly sensitive to the effects of human activities imposed on aquatic ecosystems, whereby the variation of aquatic plants is negatively correlated with the number of human activities in a water body (Nagmsnae, 2011). Concerning the fact that the topography of Nong Han wetland is flat and surrounded by communities, it is directly affected by human activities such as intrusion of humans in the wetland for agriculture, soil surface erosion in the agricultural areas, and drainage of wastewater from the surrounding communities – all of which directly affect the type and amount of aquatic plants in the wetland. Although