Lake Koronia, Greece: Shift from autotrophy to heterotrophy with cultural eutrophication and progressive water-level reduction |
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| Authors: | Chrysoula Mitraki Thomas L Crisman George Zalidis |
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| Institution: | 1Howard T. Odum Center for Wetlands & Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL, USA;2Laboratory of Applied Soil Science, Faculty of Agriculture, Aristotle University of Thessaloniki, Greece |
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| Abstract: | Lake Koronia, a Ramsar site, is shallow, polymictic, hypertrophic and until recently was aerially the fourth largest lake in Greece. Although exceeding 5 m in the past, lake depth has declined progressively from 3.8 m in 1980 to < 1 m in 1997, reducing surface area and water volume by 50% and 80%, respectively. Specific conductivityincreased from 1300 μS cm−1 in 1977 to >6000 μS cm−1 in 1991. Increased phosphate concentrations from the late 1970's (8–45 μg L−1) to the late 1990's (100–1000 μg L−1) document that the previously eutrophic system with a limited littoral zone switched to hypertrophy dominated by massive cyanobacteria blooms. Oxygen saturation of the water column increased progressively from about 80% in 1983 to full saturation about 1993, after which it decreased progressively to only 20% saturation in 1997. In spite of cyanobacteria dominance, community metabolism of the lake switched from progressively increasing autotrophy to rapidly advancing heterotrophy associated with progressive water-level reduction leading to fish extirpation in the lake. |
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| Keywords: | Autotrophy heterotrophy Greek lakes cultural eutrophication water-level reduction |
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