Winter Respiration of Lakes at Saqvaqjuac, N.W.T.

Winter oxygen consumption rates at64°N latitude were measured for 11 lake years. They ranged from 0.131 to 0.306 g O 2 ∙m −2 ∙d −1 . They were not correlated with lake depth, in contrast with the winter respiration rates of temperate lakes. We suggest that this difference results from lower summer temperatures and a lower proportion of planktonic respiration in arctic as compared with temperate lakes. C estimates of annual photosynthesis were generally lower than estimated annual respiration, and the 14 C-measured photosynthesis beneath the ice in late winter was generally too low to account for the actual amounts of oxygen evolved by photosynthesis. In one lake, a 50% increase in annual production resulted in an increase of only 19% in winter respiration, suggesting that lake respiration is an integrative process that averages out production over a period of years. Addition of methane gas to simulate a gas pipeline break to a lake resulted in an immediate 67% increase in lake respiration rate.