4.2 Aquatic Communities
and aquatic invertebrates and oxygen depletion in the water column can change commu- nity composition and structure (McDaniel 1993) . Pathogens and Microorganisms. Tese types of contaminants are primarily a concern to human health through water-based recreation activities and water-supply usage streams. Signifcant concerns include, but are not limited to, salmonellosis, shigellosis, enteropatho- genic E.coli , enterovirus, and parasitic protozoa and worms. Many of these organisms are harbored in warm-blooded animals and are shed through animal wastes or fecal con- tamination of meats during food production processes. Freshwater fsh can also harbor organisms that are consumed by humans. Other sources of these contaminants are sewage wastes, stormwater runof, and concentrated animal operations (McDaniel 1993) . Nutrient Loads. Phosphorus and nitrogen are the nutrients most often associated with enrichment problems in aquatic ecosystems. Nutrient enrichment causes eutrophication that will cause changes to aquatic ecosystem structure and function (Smith et al. 1999, 2006) . Eutrophication increases the frequency and intensity of algal blooms, especially cyanobac- teria (blue-green algae) in freshwater lakes and harmful phytoplankton (e.g., dinofagel- lates) blooms (referred to as red tides) in coastal areas (Smith et al. 2006; Downing et al. 2001; Huisman et al. 2005; Anderson 1994) . Dams . Impoundments create direct impacts through alteration of fow patterns and loss of in-stream habitats; changes in sediment transport and channel structure; impediments to genetic fow through restriction of fsh movement; and thermal stratifcation and low dis- solved oxygen (DO) content. Tey also can cause thermal or nutrient discharges from stor- age water (Yeager 1993) . Hydropower dams, as a subset, contribute to unnatural fow regimes and hypolimnetic releases that cause a cool or warmwater assemblage to be replaced by a cold or coolwater one. Dams on rivers with anadromous fsh block historical spawning grounds that can result in reduced populations due to lack of good spawning habitat and altered fsh assemblage in rivers and streams above impoundment. Withdrawals . Water withdrawals are commonly made for use in industrial processes, irrigation for crops, livestock watering, and drinking water resources. Te physical charac- teristics of streams and rivers are altered when waters are impounded to form reservoirs. Physical changes caused by withdrawals taken from rivers and streams that reduce water levels include changes to the channel dimensions, water velocities, substrate composition, and water temperature. Withdrawals can permanently reduce availability of local water resources when there is no return of any of the withdrawn water to the local hydrologic cycle. Withdrawals can also result in lowered water tables and secondary impacts to nearby riparian wetlands and littoral habitats (Zale et al. 1993) . Land Use Impacts. Converting land use from natural forest to agriculture or silviculture production and residential and commercial development continues to threaten stream
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2015 NC Wildlife Action Plan
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