4.2 Aquatic Communities
(e.g., air and water temperatures, discharges), and water chemistry (e.g., oxygen, nutrients, pollution) and how these infuences are stratifed throughout the water body (vertical dimensions). Benthic habitats within standing waters are associated with the physical structure and substrates of the lake bottom (Eschmeyer 1936; Christensen et al. 1996b; Covich et al. 1999; Schindler and Scheuerell 2002) . Riparian or littoral habitats occur at the transition between terres- trial communities and the aquatic system (Schindler and Scheuerell 2002) . Another method organizes streams into hydrologic units representing a drainage network comprised of a stream and all of its tributaries (Benke and Cushing 2005; Wagener et al. 2007; Sawicz et al. 2011) . Tese drainage networks are referred to as drainage areas (DAs) and the charac- teristics of each unit are infuenced directly by the attributes within the boundaries that defne the basin (Huang et al. 2007; Sawicz et al. 2011) . Estuarine systems are another type of aquatic natural community that is formed at the link between land, freshwaters, and the ocean, and may be referred to as estuarine, brackish, or transitional waters (Levin et al . 2001; Tagliapietra et al. 2009) . Estuarine systems are semi-enclosed coastal waters that are tidally infuenced, have a connection with seawater, and contain brackish waters that result when seawater is measurably diluted with fresh water from land drainage (Cameron and Pritchard 1963; Pritchard 1967; Cowardin et al . 1979; Tagliapietra et al. 2009) . Brackish waters result from the mingling of freshwaters and marine saltwaters and in most cases will have a low salinity gradient (measured as parts per thousand), but can range from mix- ohaline (0.5–30 ppt) to euhaline (30–40 ppt) to hyperhaline (>40 ppt) depending on proxim- ity to ocean saltwaters and fuvial, tidal, and climatic conditions that drive saltwater (i.e., salt wedge) upstream into freshwaters (Cowardin et al. 1979; Emery and Myers 1996; Neuendorf et al. 2005; Tagliapietra et al. 2009) . Water quality is not the only variable that will infuence species richness and relative abundance in aquatic communities. Te presence of variable habitat types (pools, rifes, and runs in streams); the diference in water velocities, depths, and temperatures; and the types and combinations of substrate courseness and material (e.g., sand, gravel, aquatic vegetation, woody debris) (Hrodey et al. 2009) have an infuence on which species make up the community. Moderate to high-quality in-stream habitats will have a substrate of various sized rocks with low embeddedness; woody debris such as sticks, leafpacks, snags; under- cut banks with root mats; frequent distribution of pools and rifes of varying depths and widths; and stable banks with good tree canopy and a medium to wide riparian zone with few (if any) breaks (NCDWQ 2011c) . Poor in-stream habitats will have primarily sand sub- strates, an absence of rifes; narrow and sparsely vegetated riparian zones with breaks; and deeply entrenched channels with unstable, vertical, and sparsely vegetated banks (NCDWQ 2011c) . Species diversity is potentially greatest in large streams and medium-sized rivers, especially in rife and run habitats.
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2015 NC Wildlife Action Plan
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