Simulation of thermal/dissolved oxygen habitat for fishes in lakes under different climate scenarios: Part 2. Cold-water fish in the contiguous US

Abstract

Fish habitat is strongly constrained by water temperature and available dissolved oxygen (DO). Thermal/dissolved oxygen habitat for cold-water fish in small lakes was therefore determined from simulated daily water temperature and dissolved oxygen profiles. Twenty-seven types of lakes were simulated with past (1961–1979) climate conditions observed at 209 weather stations in the USA, and with a 2×CO 2 climate scenario that is projected to occur at the same locations. The output of the Canadian Climate Centre (CCC) General Circulation Model for a doubling of atmospheric CO 2 was used to determine the climate data increments for a doubling of atmospheric CO 2. The methodology was described in Part 1 of this paper. Highlights of the results are as follows: winterkill that occurred due to dissolved oxygen deficiency in eutrophic and mesotrophic, shallow lakes of the north-central and northeastern US under past climate conditions, is projected to be replaced by summerkill due to elevated water temperatures in mesotrophic lakes, or by suitable fish habitat in eutrophic lakes under the 2×CO 2 climate scenario. Shallow lakes at 205 of 209 locations investigated are projected to experience summerkill of cold-water fish under the projected 2×CO 2 climate scenario. Climate warming is also projected to reduce by up to 38% of the past values the length of the good-growth period and the good-growth area/volume for cold-water fish in lakes at most locations in the contiguous US. Average reductions in the number of locations where lakes presently have suitable year-round cold-water fish habitat are 28, 90, and 65 locations for shallow, medium-depth, and deep lakes, respectively. Loss of fish habitat during the summer period (summerkill) under the projected 2×CO 2 climate scenario is a significant negative impact of climate warming on cold-water fish in lakes of the contiguous US. Geographic regions in which lakes cannot support cold-water fish are projected to extend significantly further north under a 2×CO 2 climate scenario.