Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Section 3.5. Biological Resources
during low tides), habitats. Each of these is described below. A schematic of
typical aquatic habitats by tide levels is provided in Figure 3.5-2.
Subtidal Aquatic Habitat
Subtidal aquatic habitats are areas of continuous open water that are submerged
during even the lowest tide; as a result, these areas are too deep to support the
types of vegetation found in emergent (i.e., occasionally exposed) wetland
habitat.
Phytoplankton; zooplankton; and fish, such as longfin smelt, northern anchovy,
speckled sanddab, and staghorn sculpin, occupy subtidal aquatic habitat. Benthic
(bottom-feeding) organisms such as worms and clams can be found in the sandy,
muddy bottom. Many species of waterfowl such as mallard, common merganser,
canvasback, and northern pintail and diving birds such as eared grebe, western
grebe, and Clark’s grebe use subtidal aquatic habitat for resting and feeding
areas.
Intertidal Aquatic Habitat
Intertidal aquatic habitat comprises 2 subtypes of habitat: intertidal mudflats, and
coastal salt marsh. Intertidal mudflats are made up of unconsolidated, muddy
bottom areas without vegetation and are present along coastal salt marshes that
are outboard of the perimeter levee. Mudflats are exposed twice daily during low
tide and extend to the extreme low water elevation (Figure 3.5-2). Narrow bands
of mudflat are also found at the same elevations along the margins of subtidal
channels in tidal wetlands.
Mudflats are highly productive and support large populations of benthic
organisms, including aquatic worms, crustaceans, and mollusks, which are
important elements of the estuarine food web. When exposed or covered by
shallow water, mudflats provide important foraging areas for migrant and
wintering shorebirds such as killdeer, greater yellowlegs, and least sandpiper,
wading birds such as great blue heron, great egret, and black-crowned night
heron, and gulls such as ring-billed gull and mew gull.
Coastal salt marsh contains persistent, rooted herbaceous vegetation dominated
by cordgrass and pickleweed. The vegetation in the marsh habitat is used as
direct cover and sources of food by rearing juvenile and adult fish, such as
longfin smelt, Chinook salmon, and steelhead. Emergent marsh habitat, however,
is within the tidal zone and drains frequently; it is therefore not used for
spawning. Benthic organisms use this habitat in the same way they use intertidal
mudflats.
Emergent wetland habitat provides nesting, foraging, and escape cover for
various songbirds such as marsh wren, song sparrow and white-crowned sparrow
and foraging and cover for wading birds such as those mentioned above.
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
3.5-17
April 2012