SOME CONSIDERATIONS OF THE CHEMICAL LIMNOLOGY OF MEROMICTIC LAKE MARY1

Some features of the chemical limnology of meromictic Lake Mary were compared to similar features of neighboring dimictic Lake Rose. This dimictic lake and the mixolimnion of Lake Mary exhibited similar seasonal variations in their chemical composition. The chemical composition of the monimolimnetic waters of Lake Mary did not vary throughout the 21‐month study. Methane production in Lake Rose began soon after thermal stratification and concentrations in the anoxic hypolimnion reached about 14 mg liter−1. Methane concentrations in the Lake Mary monimolimnion increased with depth and ranged up to 21 mg liter−1. The concentration and vertical distribution of CH4, together with an alkalinity increase of 22 mg liter−1 above that in the surface waters and an NH4+ increase of 4.2 mg liter−1, indicated that biological activity helps sustain the meromixis of Lake Mary. However, the major factor allowing meromixis is the morphometry of the lake basin.