Marin Independent Journal
Aquatic plant environmentally
stressed
By Mark Prado
IJ reporter
Thursday,
December 02, 2004 - SAN FRANCISCO - A long, sinewy green weed is pumping
life into San Francisco Bay.
Scientists say eelgrass, a native marine
plant that thrives in shallow bay waters, is a vital part of San Franciso Bay
ecology, offering both protection from predators for a variety of animal species
and food for a myriad organisms.
"Eelgrass serves as the basis for a lot
of ocean life," said Jim Milbury, a spokesman for the National Oceanic and
Atmospheric Administration. "It
is the very basic part of
the food chain."
NOAA researchers yesterday presented findings from a two-year eelgrass
study that found the plant, an incubator of life in Marin coastal areas and
elsewhere, is doing better than it did 15 years ago but is still not as
plentiful as expected.
"What we discovered in our survey is that we have
more eelgrass in San Francisco Bay than we thought," said Brian Mulvey, fish
habitat specialist with NOAA. "In
1987 we had 316 acres and
today we have 2,600 acres.
That sounds impressive, but
compared with other estuaries
on the West Coast we should
probably have 20,000 to 25,000
acres."
Researchers
believe improved water quality in the bay in recent years has eelgrass making a
comeback and that the plant is trying to recover. But because eelgrass grows in
the shallows of the bay, turbidity at the bay's surface and a suspended layer of
sediment may be keeping it from a full recovery.
"San Francisco Bay is a
stressed environment," said consultant Keith Merkel, who worked on the $1
million study. "That's why
you see eelgrass come and
go."
The research
is bringing attention to the aquatic plant.
"We want to see if anything
can be done to address the problems," Mulvey said. "We
are not sure what's limited
eelgrass and we wonder why
the beds are not denser. We
are making a lot of head-way.
We are learning a lot about
eelgrass."
One of the strongest
beds of eelgrass sits in Richardson Bay off of Sausalito. Another patch rests
off Kyle Cove near Tiburon.
"We think there should be more in San Rafael
and Larkspur, but it is not there. We want to figure out why," Mulvey
said.
Eelgrass beds are in shallow waters, typically no more than eight feet
under water, and the plant's long strands reach to the surface during low tide.
The more eelgrass, the better the marine environment fares, researchers
say. Eelgrass functions as a nursery area for many commercially and
recreationally important finfish and shellfish species. Eelgrass is a major food
source, forming the base of food webs and providing a food source for organisms
that feed directly on eelgrass leaves, such as migrating waterfowl.
Eelgrass also supports tiny plants, animals, and microbial organisms
that, in turn, are eaten by other invertebrates, larval and juvenile fish, and
birds.
Eelgrass beds also slow wave and current action, trap those
suspended particulates, and reduce erosion by stabilizing the sediment. The
plant also improves water clarity, cycles nutrients and generates oxygen during
daylight hours.
The study was paid for by the California Department of
Transportation as compensation for bridge construction work on the new Bay
Bridge that damaged some eelgrass beds.
"We want to find out more and we
plan to keep monitoring it," Mulvey
said
Contact IJ reporter Mark Prado
via e-mail at mprado @marinij .com
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