Biology Reference
In-Depth Information
Cordgrass
The first species to protrude above the surface of the water in the lower salt
marsh zone is Pacific cordgrass (
Spartina foliosa
). It forms narrow bands
or meadows at the edges of the bay and other areas subject to tidal inunda-
tion. Its pale, yellow-green stem sprouts narrow, green leaf blades and
grows one to three feet tall, but it may be half submerged in salty water. Its
leaves often appear grayish because of silt films left by high tides. Cord-
grass manages its salt balance through leaf glands, cell sap, and sequestra-
tion, and its hollow stems deliver oxygen to its submerged roots. Cord-
grass blooms from mid- to late summer, with the flowers appearing in
clusters along the tip of the stalk. The seeds have a low germination rate, so
the plant tends to reproduce by sprouting clones from underground rhi-
zomes. Though few animals can stomach its salty foliage, cordgrass con-
tributes to the estuary in other ways. These plants grow in wide meadows
that absorb wave energy and slow the movement of water, protecting
shorelines from erosion and encouraging sediments to drop out of the
water column. Microbes, worms, and snails feed on cordgrass detritus,
contributing to the food web, while the fine clays and muds help build
marshland. Endangered California Clapper Rails rely heavily on cordgrass
cover to hide from predators.
Unfortunately, smooth cordgrass
(
Spartina alterniflora),
), an invasive
exotic cordgrass species from the Atlantic coast, has been hybridizing with
the bay's native Pacific cordgrass since the 1990s. Left unchecked, the hy-
brids would threaten Pacific cordgrass populations with extinction in the
San Francisco estuary (see p. 268, “Weeding by Satellite”).
Spongy tissues help conduct air inside cordgrass stem. (Jude Stalker)
