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Classification of Wetlands and Deepwater Habitats of the United States
Definition. The Marine System
(Fig. 2) consists of the open ocean
overlying the continental shelf and its associated high-energy
coastline. Marine habitats are exposed to the waves and currents
of the open ocean and the water regimes are determined primarily
by the ebb and flow of oceanic tides. Salinities exceed 30 , with
little or no dilution except outside the mouths of estuaries.
Shallow coastal indentations or bays without appreciable
freshwater inflow, and coasts with exposed rocky islands that
provide the mainland with little or no shelter from wind and
waves, are also considered part of the Marine System because they
generally support typical marine biota.
Limits. The Marine System extends from the outer edge of the
continental shelf shoreward to one of three lines: (1) the
landward limit of tidal inundation (extreme high water of spring
tides), including the splash zone from breaking waves; (2) the
seaward limit of wetland emergents, trees, or shrubs; or (3) the
seaward limit of the Estuarine System, where this limit is
determined by factors other than vegetation. Deepwater habitats
lying beyond the seaward limit of the Marine System are outside
the scope of this classification system.
Description. The distribution of plants and animals in the Marine
System primarily reflects differences in four factors: (1) degree
of exposure of the site to waves; (2) texture and physicochemical
nature of the substrate; (3) amplitude of the tides; and (4)
latitude, which governs water temperature, the intensity and
duration of solar radiation, and the presence or absence of ice.
Subtidal. -- The substrate is continuously submerged.
Intertidal. -- The substrate is exposed and flooded by tides; includes the associated splash zone.
Classes. Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Reef,
Rocky Shore, and Unconsolidated Shore.
Fig. 2. Distinguishing features and examples of habitats in the Marine System. EHWS = extreme high water of spring tides; ELWS = extreme low water of spring tides.