Tidal_PAD_V1_Sec4.pdf - Snohomish County PUD

Snohomish County PUD –Pre-Application Document
4 – Existing Environment
substantially greater complement of organic material than is found in the more exposed beaches of
Washington’s outer coast (DON 2006).
Like salt marsh habitats, beaches exhibit distinct community zonation based on the degree of tidal
inundation. The upper inter-tidal beach is a somewhat hostile area, as it is only submerged for
brief periods and often exposed to a wide range of temperatures. Moreover, sources of food in this
region are scarce and unreliable (DON 2006). As a result, few species venture to inhabit this
section of the habitat, although, for a variety of pinnipeds and birds, it offers a suitable
environment for breeding. The middle inter-tidal beach, on the other hand, is alternately
submerged and exposed for moderate periods of time, and is populated by highly mobile species
such as isopods, crabs, and polychaetes (see Table 4-14) (DON 2006). Below this portion of the
habitat are the lower inter-tidal beach and the surf zone – regions that are only exposed for short
spans of time during the lowest tides, and where organisms are often subject to regular physical
agitation (Airamé et al. 2003; Proctor et al. 2006). Here, faunal assemblages are primarily
comprised of species that are capable of burying into the sediment for protection (see
Table 4-14).
In Puget Sound, beach habitats are associated with essentially the entire coastline, except around
the San Juan archipelago (Williams et al. 2003). Sandy beach is the dominant beach in Hood
Canal, the southern reaches of the basin, northern Bellingham Bay, Birch Bay, and Boundary Bay,
while gravelly sand lines the remainder of the basin, except the western half of the Strait of Juan de
Fuca, which is characterized by gravel beach (DON 2006).
Table 4-14. Select faunal species associated with beach habitats
Common Name Scientific Name Common Name Scientific Name
Razor Clam Siliqua patula Beach Hopper/Sand Flea Traskorchestia spp.
Pismo Clam Tivela stultorum Beach Hopper/Sand Flea Megalorchestia spp.
Purple Olive Snail Olivella biplicata/O. baetica Rove Beetle Staphylinidae
Predacious Polychaete
Nephtys spp.
Goose Barnacle
Lepas spp.
Shrimp Crangon spp. Blood Worm Euzonus mucronatus
Opossum Shrimp Archaeomysis grebnitzkii Isopod Excirolana spp.
Amphipod Haustorridae/Phoxocephalidae Mole Crab Emirita analoga
Source: Kozloff 1993.
4-46 January 31, 2008