II. B. Habitat Classification |
The nearshore environment is generally defined as the area encompassing the transition from subtidal marine habitats to associated upland systems. Williams and Thom (2001) define this in practical terms as the zone where direct functional interactions occur between upland and marine habitats. In Puget Sound specifically, this area typically includes habitats from the marine riparian zone to the lower limit of the photic zone (generally to a maximum of 30 m below mean lower low water [MLLW]). Within this range occur the strongest interactions between the marine environment and coastal processes. For example, upland vegetation (marine riparian habitat) contributes to beach and bank stability, provides shade for the upper intertidal zone, and contributes organic matter (leaf litter, woody debris) to the nearshore marine ecosystem (Williams and Thom 2001; Williams et al. 2001) (Figure II-1).
Figure II-2. Generalized distribution of major intertidal habitat types along an elevation (depth) gradient (from Nightingale and Simenstad 2001a., adapted from Krukeburg 1990, artist Sandra Noel).
Within these vertical classification zones, other physical, geological, and chemical factors (specifically, wave energy, substrate, and salinity) interact to constrain the distributions and interactions of marine plants and animals (Dethier 1990). A natural community can be defined as a distinct and recurring assemblage of plants and animals naturally associated with each other and with a particular physical environment. Thus, habitats are distinguished by their physical constraints and biotic communities. Habitat types found in Puget Sound include eelgrass meadows, kelp forests, banks, flats, marshes, sand spits, subestuaries, and marine riparian areas. The structure and typical species composition of habitat types relevant to Bainbridge Island are described in detail in Chapter IV of this document.
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