Abstract
Five important features appear in rough order from the surface downwards in physical and chemical profiles from high Arctic coastal meromictic lakes. These features are: 1) a supersaturated oxygen maximum, 2) the center of the oxycline, 3) a thermal maximum, 4) a major absorption maximum, and 5) an anoxic stratum. The depth of the absorption maxima and the top of the anoxic strata are both statistically correlated to light penetration and to each other. The depth of the thermal maximum also shows a statistical correlation to light penetration among lakes with a relatively shallow chemocline. The temperature of the thermal maximum appears to be maintained by inputs of light energy while the oxygen maximum is maintained to a large extent by photosynthesis. Thus, these major features are all influenced by light penetration.
With the exception of the supersaturated oxygen maximum, all of the above features are dependent for their existence upon the primary chemocline stabilizing the water column. Apparently, in at least some lakes, a near surface secondary chemocline or cool (ca. 4° C) secondary inverse thermocline will enhance the stability of the water column above the primary chemocline sufficiently to allow a supersaturated oxygen maximum to develop in this region. However, the supersaturated oxygen maximum can extend into the primary chemocline, and in highly transparent Sophia Lake (Cornwallis Island, N.W.T.) this feature extends below the primary chemocline.
Where the chemocline is found below depths with adequate illumination, features other than the supersaturated oxygen maximum should be found in deeper water as well, or they should be eliminated from the profiles. Thus, where the chemocline is relatively shallow, the depth of features like the thermal maximum or anoxic strata are related most closely to light penetration, but where chemoclines are deep, as in Lake Tuborg (Ellesmere Island, N.W.T.), the depth of the chemocline determines the depth of the oxycline, thermal maximum, absorption maximum and anoxic stratrum.