IV. A. Nearshore Habitat Classification Systems |
Nearshore habitats have been classified in a number of ways. One of the most widely used schemes is A Marine and Estuarine Habitat Classification System for Washington State (Dethier 1990) developed for the Washington State Department of Natural Resources. This scheme defines classes of habitats by their depth, substratum type, energy level (i.e., wave, currents), as well as some “modifiers” such as salinity range. The Dethier scheme expands the breakdown of habitat types, which provides more regional relevance to the national wetland habitat classification system developed by Cowardin et al. (1979).
A list of the various major habitat classes in the Dethier scheme is provided in Appendix B. Some of the major habitat types that occur within the nearshore environment include eelgrass meadows, kelp forests, seaweed beds, flats, tidal marshes, subestuaries, sand spits, and beaches and backshore. Although not part of Dethier’s classification scheme, the nearshore also includes banks, bluffs, and marine riparian vegetation. Because physical processes, such as wave energy and currents, determine where these habitats will develop, the Dethier scheme classifies habitats or groups of habitats by physical conditions. For example, the class “Estuarine intertidal mixed-fines; partly enclosed” describes a set of conditions in backwater areas of estuaries (i.e., salinity commonly less than 30 parts per thousand [ppt]) or on deltas away from large distributory channels. Within this class, vascular marsh plant communities and eelgrass predominate. Another example of a class is “Marine intertidal rock; semi-protected and protected”. The most common habitat type in this class is seaweed beds. This habitat class occurs where salinity is generally above 30 ppt, oceanic swell or extensive wind fetch is minimal, and rocks predominate because of steepness of the shore or currents. With the Dethier scheme, habitat types can be predicted for areas where physical conditions are known. This classification scheme can assist in determining both what types of habitats existed historically in areas that have been severely altered, predicting habitats in areas where only physical conditions are known, and determining what types of physical and chemical conditions need to be established in order to restore habitats.
Simenstad et al. (1991) developed protocols for monitoring nearshore habitats in Puget Sound for the U.S. Environmental Protection Agency (EPA) in a report titled, Estuarine Habitat Assessment Protocol. As in Dethier (1990), the Habitat Protocols report included a list of habitat types and the species most commonly associated with the habitat types. In addition, the report contains known linkages between habitats and species. Juvenile salmon, for example, are found in eelgrass meadows, because they are known to feed and find refuge in eelgrass. Hence, the Habitat Protocols report contains valuable information on the functions of the common nearshore habitats. The report also is useful in predicting what functions would be altered or changed if a habitat is altered or destroyed. In addition, the functions benefitting from restoration or protection of a habitat can be predicted.
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