Chapter 4 Habitats
(e.g., oxygen, nutrients, pollution) and how these influences are stratified 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 terrestrial communities and the aquatic system (Schindler and Scheuerell 2002) . An early method categorizes streams based on connectivity patterns (e.g., as orders) with other flowing systems, and classifies streams into a dendritic hierarchical order where the smallest unit is a first order stream (Strahler 1957) . As first order streams connect to other streams the hierarchy increases to second order, third order, and on so that the largest are rivers that are higher order systems. Another method organizes streams into hydrologic units representing a defined drainage network comprising a stream and all its tributaries (Benke and Cushing 2005; Wagener et al. 2007; Sawicz et al. 2011) . These drainage networks are referred to as drainage areas (DAs), and the characteristics of each unit are influenced directly by the landscape attributes within the boundaries that define 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, freshwater, 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 influenced, 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 salt water and in most cases will have a low salinity gradient (measured as parts per thousand), but can range from mixohaline (0.5–30 ppt) to euhaline (30–40 ppt) to hypersaline (>40 ppt) depending on proximity to ocean saltwaters and fluvial, 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 influence species richness and relative abundance in aquatic communities. The presence of variable habitat types (pools, riffles, and runs in streams); the difference in water velocities, depths, and temperatures; and the types and combinations of substrate coarseness and material (e.g., sand, gravel, aquatic vegetation, woody debris) (Hrodey et al. 2009) have an influence on which species make up the community. • Moderate- to high-quality in-stream habitats will have a substrate of heterogenous substrates with low embeddedness; woody debris such as sticks, leaf packs, snags; undercut banks with root mats; frequent distribution of pools and riffles of varying
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2025 NC Wildlife Action Plan
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