Long-Term Consequences of Water Pumping on the Ecosystem Functioning of Lake Sekšu, Latvia
2020
Izabela Zawiska | Inta Dimante-Deimantovica | Tomi P. Luoto | Monika Rzodkiewicz | Saija Saarni | Normunds Stivrins | Wojciech Tylmann | Anna Lanka | Martins Robeznieks | Tom Jilbert
Cultural eutrophication, the process by which pollution due to human activity speeds up natural eutrophication, is a widespread and consequential issue. Here, we present the 85-year history of a small, initially Lobelia&ndash:Isoë:tes dominated lake. The lake&rsquo:s ecological deterioration was intensified by water pumping station activities when it received replenishment water for more than 10 years from a eutrophic lake through a pipe. In this study, we performed a paleolimnological assessment to determine how the lake&rsquo:s ecosystem functioning changed over time. A multi-proxy (pollen, Cladocera, diatoms, and Chironomidae) approach was applied alongside a quantitative reconstruction of total phosphorus using diatom and hypolimnetic dissolved oxygen with chironomid-based transfer functions. The results of the biotic proxy were supplemented with a geochemical analysis. The results demonstrated significant changes in the lake community&rsquo:s structure, its sediment composition, and its redox conditions due to increased eutrophication, water level fluctuations, and erosion. The additional nutrient load, particularly phosphorus, increased the abundance of planktonic eutrophic&ndash:hypereutrophic diatoms, the lake water&rsquo:s transparency decreased, and hypolimnetic anoxia occurred. Cladocera, Chironomidae, and diatoms species indicated a community shift towards eutrophy, while the low trophy species were suppressed or disappeared.
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