Abstract
Tonle Sap lake-river floodplain ecosystem (TSE) is one of the world’s most productive freshwater systems. Changes in hydrology, climate, population density, and land use influence water quality in this system. We investigated long term water quality dynamics (22 years) in space and time and identified potential changes in nutrient limitation based on nutrient ratios of inorganic nitrogen and phosphorus. Water quality was assessed at five sites highlighting the dynamics in wet and dry seasons. Predictors of water quality included watershed land use, climate, population, and water level. Most water quality parameters varied across TSE, except pH and nitrate that remained constant at all sites. In the last decade, there is a change in the chemical nutrient ratio suggesting that nitrogen may be the primary limiting nutrient across the system. Water quality was strongly affected by development in the watershed i.e., flooded forest loss, climatic variation, population growth, and change in water level. Seasonal variations of water quality constituents were driven by precipitation and hydrology, notably the Mekong’s distinct seasonal flood pulse.
Highlights
Understanding water quality is key to understanding the health of an ecosystem [1].Alterations to river hydrology, climate change, and nutrient loading due to anthropogenic pressure leads to the degradation of water quality and a reduction of biodiversity, fish survival, and fish growth [2,3,4]
We found median Total suspended solids (TSS), Total phosphorus (TP), and NH4 + concentration was highest in Phnom Krom (PR) followed by Back Prea (BP), Kampong Luong (KL), Kampong Chhnang (KC), and Prek Kdam (PK) (Figure 2)
We found that long-term water quality parameters in the Tonle Sap lake-river floodplain ecosystem (TSE) change in space and time depending on watershed land use, water level dynamics, population density, air temperature, precipitation, and flood pulse change
Summary
Understanding water quality is key to understanding the health of an ecosystem [1]. Alterations to river hydrology, climate change, and nutrient loading due to anthropogenic pressure leads to the degradation of water quality and a reduction of biodiversity, fish survival, and fish growth [2,3,4]. While the river has been an important part of culture and society for thousands of years, in the past half-century, there have been substantial alterations to the Mekong River and its watershed including hydroclimate alterations, eutrophication, and deforestation [2,6,7]. Tonle Sap Lake (TSL) is in the Lower Mekong watershed and is one of the most productive freshwater fisheries in the world [8].
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