4.2 Aquatic Communities
Water Quality. Changes in land use patterns within a watershed cause changes in water quality; land use alterations closer to stream channels typically have more impact. Runof from urban areas often contains higher concentrations of nutrients (such as nitrogen and phosphorus), sediment, metals, hydrocarbons, and microbes. Allowing livestock access to rivers can contribute to bank erosion, sedimentation, and nutrient input. Timber harvest and poorly constructed and maintained timber roads are additional sources of erosion if proper controls are not used and maintained. Climate change has the potential to increase air temperatures; therefore increased water temperatures can lead to algal blooms which reduce stream oxygen availability. Te increased water temperature alone can cause a decline in DO and DO declines can lead to fsh kills, whether as a direct result of increased water temperature or as a secondary efect of algal blooms (DeWan et al. 2010; Band and Salvesen 2009) . Invasive Species. Medium river communities in our state contain invasive species in addition to the native fora and fauna. Tese invasive species impact native species through competition, predation, and hybridization. Tey can also alter habitat and transmit dis- eases. Te introduction of any invasive species is cause for concern, and the prevalence of warmer water temperatures in the future may increase the likelihood of the invasion of additional exotic species, once thought to be nonthreatening because the winters were too cold for their survival. Invasive aquatic animal species, such as Asian Clams, Mystery Snails, Red Swamp Crawfsh, and Nutria may have negative efects on native species through competition for space and resources and as disease vectors. Te Asian Clam is an exotic species found in aquatic systems throughout the state; its efects on native mussels are largely unknown. Flathead Catfsh are a concern because of direct predation on native species. Nutria are considered a serious pest species in the United States because they eat a variety of wetland and agricultural plants and their burrowing damages streambanks, impoundments, and drainage systems. Invasive plants in the riparian area can have negative impacts on stream systems by cre- ating a monoculture (such as Japanese Knotweed) with poor nutrient inputs that reduces bank stability and shading and therefore, creates warmer stream temperatures. Alligator Weed creates foating mats that disrupt DO levels. Invasive aquatic plants such as Asian Dayfower, Hydrilla, Water Hyacinth, and Giant Salvinia could pose more of a threat to these systems with a warmer climate. Exotic insect pests may be a signifcant factor in river communities because they negatively impact native vegetation, thereby altering habitats or allowing nonnative species to fourish. Climate Impacts . Climate change is likely to have a synergistic efect with other, more impending threats to medium river systems, such as development and lack of/removal of
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2015 NC Wildlife Action Plan
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