Lakes dimictic

Spliethoff, H.M., Mason, R.P. and Hemond, H.F. (1995) Interannual variability in the speciation and mobility of arsenic in a dimictic lake. Environmental Science and Technology, 29(8), 2157-161. 

McMahon, J. W. 1969. The annual and diurnal variation in the vertical distribution of acid soluble ferrous and total iron in a small dimictic lake. Limnology and Oceanography 14 357-367. 

Hvpolimnetic Sulfate Reduction. Little Rock Lake exhibits dimictic circulation, but the volume of the hypolimnion is only about 3% of the total lake volume. Oxygen depletion occurs in late summer, and a buildup of H S and Fe2+ is observed following the development of anoxia. Sulfate depletion is observed (Figure 4), but hypolimnetic reduction is a minor sulfate sink for the whole lake because the hypolimnion is small and because much of the hypolimnetic H2S entrained in the water column during turnover probably is reoxidized. Using an oxidation- diffusion model we estimate that about half of the hypolimnetic H S entrained in the water column during turnover is oxidized and tne other half is lost by diffusion to the atmosphere no more than 5% of annual S input leaves by emission of H2S produced within the hypolimnion. 

A lake that is not meromictic is called holomictic. Holomictic lakes have one of the mixing types described previously, i.e. warm or cold monomictic, dimictic, etc. In conclusion, holomictic and meromictic properties refer to chemical characteristics of the water bodies, whereas epi-, meta- and hypo-limnion refer to the thermic regime of lakes. Obviously, both concepts are linked. 

Dimictic lakes. Represent the average temperate lake. They have two mixing periods, spring and autumn, when the temperature (and hence density) of the water column becomes uniform throughout, enabling strong winds to effect an overturn. 

When the water column reaches a uniform temperature (and hence density) from top to bottom it is susceptible to mixing (overturn), which is usually caused by wind action.The unusual density behaviour of water is a controlling factor. In contrast to normal seawater, which exhibits a continuous increase in density with decreasing temperature because of the salt content, the density of fresh water reaches a maximum at 4°C (i.e. while it is still a liquid), which causes ice to float.We can examine the consequences of this property by considering a typical temperate dimictic lake (one that mixes twice a year). In winter, under ice, the water tempera-... 

In short, tlie most common lake type is a fairly small dimictic lake, with ice coverage from the beginning of November to the end of April. It is situated in forested surroundings, has a high content of humic matter compared to most European lakes, low alkalinity, four species of fish, and the biodiversity of other animals and plants is also low. 

Meyer S, Kubsch G, Lovric M, Scholz F (1997) Speciation of mercury in two dimictic lakes of North-East Germany during a period of 6(X) days. Int J Environ Anal Chem 68 347-368... 

Lakes with two turnover events per year are dimictic. Monomictic lakes may have a single turnover event, while other lakes described as polymictic experience multiple episodes of weaker stratification and turnover events. Some permanently ice covered lakes never turn over, are amictic and maintain isothermal temperatures due to a lack of wind induced mixing. At times of calm, stable weather during the period of... 

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