THE COMPARATIVE LIMNOLOGY OF HIGH ARCTIC, COASTAL, MEROMICTIC LAKES

Five important features appear in rough order from the surface downwar ds in physical and chemical profiles from high arctic coastal meromict ic lakes. These features are: (1) a supersaturated oxygen maximum, (2) the center of the oxycline, (3) a thermal maximum, (4) a major absorp tion maximum, and (5) an anoxic stratum. The depth of the absorption m axima and the top of the anoxic strata are both statistically correlat ed to light penetration and to each other. The depth of the thermal ma ximum also shows a statistical correlation to light penetration among lakes with a relatively shallow chemocline. The temperature of the the rmal 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. W ith the exception of the supersaturated oxygen maximum, all of the abo ve features are dependent for their existence upon the primary chemocl ine stabilizing the water column. Apparently, in at least some lakes, a near surface secondary chemocline or cool (ca. 4 degrees C) secondar y inverse thermocline will enhance the stability of the water column a bove the primary chemocline sufficiently to allow a supersaturated oxy gen maximum to develop in this region. However, the supersaturated oxy gen maximum can extend into the primary chemocline, and in highly tran sparent Sophia Lake (Cornwallis Island, N.W.T.) this feature extends b elow the primary chemocline. Where the chemocline is found below depth s with adequate illumination, features other than the supersaturated o xygen maximum should be found in deeper water as well, or they should be eliminated from the profiles. Thus, where the chemocline is relativ ely shallow, the depth of features like the thermal maximum or anoxic strata are related most closely to light penetration, but where chemoc lines are deep, as in Lake Tuborg (Ellesmere Island, N.W.T.), the dept h of the chemocline determines the depth of the oxycline, thermal maxi mum, absorption maximum and anoxic stratum.