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Deoxygenation of a Florida lake during winter mixing.

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Thomas J. Whitmore

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Johnson Pond occupies a small, deep, solution basin (A = 2.2 ha, zmax = 17.5 m) in north Florida. This warm, monomictic lake gains and loses 5,945 cal cm−2 annually. Dissolved color and algal turbidity limit light and heat penetration, causing steep gradients in temperature, oxygen, dissolved inorganic C, and remobilized sedimentary P during stratification from March through November. Water below 5 m is cool (<14°C) and anoxic throughout the year. Weak chemical gradients can persist in the water column during homothermy. The lake is ineffectively mixed because of morphometry, wind sheltering by trees, and the brevity of homothermy. An unusual consequence of winter mixing is very low oxygen concentrations in surface waters (< 1 mg liter−1). Surface-water oxygen is diluted by upward mixing of deeper anoxic waters, and O2 is consumed by BOD and reduced Fe and S. Deoxygenation at mixis occurs in several African lakes, but is unreported in warm, monomictic lakes of North America.


Abstract only. Full-text article is available through licensed access provided by the publisher. Published in Limnology and Oceanography 36(3), 577-585. doi: 10.4319/lo.1991.36.3.0577. Members of the USF System may access the full-text of the article through the authenticated link provided.


Association for the Sciences of Limnology and Oceanography / Wiley

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