4.2 Aquatic Communities
cover contributes to rising water temperatures, especially where water depths are shallow enough that the entire water column is subject to solar heating. Climate Variability. Research conducted by Eaton and Sheller (1996) and Mohseni et al. (2003) assessed the efects of climate warming on 57 species of fshes in streams across the United States. Depending on minimum temperature tolerance assumptions, species requiring coolwater habitats could experience a 12%–15% decrease in available habitat (DeWan et al. 2010) . When the connectivity between streams and rivers within drainage basins provides adequate dispersal corridors, species at the southern extent of their geographi- cal distribution may shift their distributions northward into cooler habitats ( Allan et al. 2005 ). Where adequate dispersal corridors are limited or restricted, access to or availability of cooler water habitats may limit the range of those species subject to narrow temperature tolerance ( DeWan et al. 2010 ). Increased air temperatures may lead to increased water temperatures and potentially lower DO levels; however, increased air temperature may have varying efects on coolwater systems due to factors such as the degree of groundwater infuence, amount of shading by riparian vegetation, and watershed aspect. Hot spells can have the same efect as overall increased air temperatures but on a much more acute scale. Problems such as increased evaporation and therefore, lower amounts of fowing water, will vary depending on factors such as groundwater infuence. Chronically warmer water temperatures and lower DO levels may increase stress on organ- isms. Te increased water temperature alone can cause a decline in DO and any decline in DO can lead to fsh kills, whether as a direct result of increased water temperature or as a secondary efect of algal blooms. Termal stratifcation will likely not be an issue when aquatic systems are relatively shallow; however, the large river systems of the Piedmont and Coastal Plain ecoregions and deep water reservoirs could experience stratifcation, algal blooms, and potential fsh kills related to higher than normal water temperatures (DeWan et al. 2010; Band and Salvesen 2009) . Drought. Severe and prolonged droughts may decrease stream fow, decrease groundwa- ter recharge, and increase evaporation. Lower water levels during dry times will increase stress to the system. Connectivity to contributing waters within the system will be restricted or eliminated by low and no-fow conditions. Changes in fow regime will likely result in changes in the overall stream morphology and transport of sediment that leads to altered habitat composition. Te balance between surface fow and groundwater recharge may be altered. Decreases in overall summer precipitation may cause reduced water fows, which can further contribute to warmer water temperatures and water quality stressors (DeWan et al. 2010; Karl et al. 2009; Band and Salvesen 2009; Holman et al. 2010) .
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2015 NC Wildlife Action Plan
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