Acidification of streams and recovery of acidified lakes would be altered by climate changes (Yan et al., 1996; Magnuson et al., 1997; Dillon et al., 2001). In addition to direct atmospheric deposition of acids, sulfates deposited in the catchment are transported to streams during storm events as pulses of acidity. Lakes would receive less buffering materials in dryer climates and more in wetter climates. Lakes high in the landscape that receive less groundwater in dry years would be more vulnerable to acidification (Webster et al., 1996).
Climate change would interact with biogeochemical transport and transformation of toxics such as mercury, zinc, and pesticides (see brief reviews in Magnuson et al., 1997; Schindler, 1997; and related physiological understanding in Wood and McDonald, 1997). The expected influences are poorly known as well as complex and variable, depending on the toxin, the organism, and the climate scenario. Enough is known to say that toxic stresses are not independent of climate change.
Winter recreational opportunities would decline with warmer climates. Declines in safe ice conditions would reduce all ice-related activities such as ice fishing, ice skating, ice boating, and snowmobiling on lakes and rivers. Recreational uses of lakes that become more eutrophic are likely to be degraded by lower water clarity and increased blooms of noxious blue-green algae. Nonmarket values for water-based recreation are in direct conflict with greater direct uses of that water and a warmer and drier climate. These values ranged from $3-65 per thousand m3 of water for fishing, rafting, and river recreation in general in Colorado (Postel and Carpenter, 1997).
UV-B radiation can be harmful to freshwater organisms (Bothwell et al., 1994; Williamson and Zagarese, 1994; Williamson et al., 1996). Absorption of UV-B is lower in clearwater lakes. Reduction of colored DOC entering lakes during drier conditions results in greater transmission and thus greater harm to organisms (Schindler et al., 1996a; Yan et al., 1996; Schindler, 1997; Williamson et al., 1996).
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