4.2 Aquatic Communities
important elements in the stream and river networks in terms of infuencing water quality and quantity.
A stream classifcation system using DA as a break for size classes, similar to those described in the Northeast Aquatic Habitat Classifcation System and the National Fish Habitat Framework, has been applied to this aquatic community description. Te hierar- chical classifcation system shown in Table 4.2.1 defnes headwater streams as having a DA of 40 square miles or less (Olivero and Anderson 2008; Olivero-Sheldon and Anderson 2013) . Stream size afects the aquatic biological assemblages within a stream reach (Vannote et al. 1980; Higgins et al. 2005; Olivero-Sheldon and Anderson 2013) . Species diversity tends to be lower in headwater systems when base fow conditions are highly variable. Overall, species richness is typically lower than in small river systems and is often comprised of the most common generalist species; mussels are often absent from headwater streams. In these aquatic com- munities, the coarse organic matter from riparian vegetation provides the energy resources for what is often a consumer community dominated by shredding insects (Olivero-Sheldon and Anderson 2013) . Benthic macroinvertebrates are a very important component of the commu- nity, and aquatic insect species richness can be very high even in headwaters in agricul- tural and urban landscapes (Moore and Palmer 2005; Meyer et al. 2007) . Headwater streams in the Mountain ecoregion are infuenced by location on the landscape. Persistent water temperatures will determine whether they are considered coolwater sys- tems or coldwater systems. Headwater streams found in other areas of the state are more likely to be considered warm water systems. Warmwater systems are those that have water temperatures that are persistently greater than 25°C (77°F). Water temperature contributes signifcantly to the species assemblages that occur in aquatic environments. 4.2.7.2 Location of Habitat Tese systems can be found statewide but are more prevalent in the Mountain and Piedmont ecoregions. Headwater systems may be associated with small wetland systems and some originate at natural spring heads. Many streams in this community type are unnamed tributaries; however, examples include Morgan Creek, Parkers Creek, Little Creek, and White Oak Creek. Te 2005 WAP described riverine aquatic communities, which would include headwater streams, as a priority habitat (see Chapter 5) (NCWRC 2005) . 4.2.7.3 Problems Affecting Habitats In North Carolina, headwater systems are vulnerable to impacts because they often occur in agricultural and urbanized environments and are less likely to be protected by reg- ulatory requirements such as avoidance and minimization measures and conservation
250
2015 NC Wildlife Action Plan
Made with FlippingBook - professional solution for displaying marketing and sales documents online