[env-trinity] Contra Costa Times 5-18
sari at sisqtel.net
Wed May 19 13:37:00 PDT 2010
Delta decline linked to Sacramento sewage treatment in new study
Other researchers welcome information but say conclusion too broad
<mailto:mtaugher at bayareanewsgroup.com?subject=ContraCostaTimes.com:
Delta decline linked to Sacramento sewage
treatment in new study>By Mike Taugher
Contra Costa Times
Posted: 05/17/2010 05:11:51 PM PDT
Updated: 05/18/2010 07:50:13 AM PDT
A new study that shows environmental problems in
the Delta are primarily driven by toilet-flushing
in Sacramento and not the state's dams and
pumps is sure to get a lot of attention from
water agencies that contend their effect on the Delta is exaggerated.
Discharges from the Sacramento Regional County
Sanitation District and other sewer-treatment
plants have profoundly changed the food web in
ways that deprive Delta smelt and other native
fish while favoring fish considered less desirable, the study says.
The paper, which has been peer-reviewed and will
be published in Reviews in Fisheries Science,
shifts focus from Delta pumping stations to
another contributor of the Delta's problems.
Specifically, sewer discharges from Sacramento
have dramatically increased the amount of
ammonium in Delta waters, while another nutrient,
phosphorus, has declined because of its phaseout from detergents.
That shift has changed the building blocks of the
estuary's food web in ways that determine what
kinds of fish can thrive, and which ones can't,
according to the paper by Patricia Glibert, an
ecologist at the University of Maryland's Center for Environmental Science.
The paper says the way to start fixing the Delta
is to reduce the nutrient discharges from the Sacramento sewer system.
"Until such reductions occur, other measures,
including regulation of water pumping or
manipulations of salinity, as has been the current strategy, will
likely show little beneficial effect," the paper
concludes. "Without such action, the recovery of
the endangered pelagic fish species is unlikely at best."
The research was funded mostly by the contractors
who rely on water from Delta pumps.
Predictably, they trumpeted the results as proof
that the influence of water diversions from the Delta have been overemphasized.
"This study reinforces how additional
restrictions on water exports from the Delta will
not provide for the recovery of the fish species.
All the stressors harming the Delta need to be
addressed," said Laura King Moon, assistant
general manager for the State Water Contractors,
a group of agencies from the Tri-Valley to
Southern California that rely on the state's Delta pumps.
Officials at the Sacramento sewer plant attacked the funding source.
"This has been a line of thinking they (water
contractors) have been trying to draw for some
time," said Stan Dean, director of policy and
planning for the Sacramento regional sewer plant.
"You have to be careful about seeing the
relationships (in trend analyses) that you want to see."
Glibert, who has not previously published work on
the Delta but has extensive experience studying
other estuaries, is a member of a prestigious
panel of scientists that recently concluded that
restrictions on Delta pumping operations are for
the most part scientifically justified.
Researchers who have spent years studying the
Delta were critical of several aspects of the paper.
"It's really stretching it to say ammonium is the
root cause of the Delta smelt decline," said Bill
Bennett, an ecologist at UC Davis and the
foremost expert on Delta smelt. "You can see a
decline in the food and a decline in the fish,
when something else could be causing the decline in both."
Several researchers said Glibert was a solid
scientist whose paper adds to what is known about
the Delta. But Bennett and others said the
findings, which come close to fingering a silver bullet, went too far.
"I think she's taking things a little too far, a
little premature," Bennett said.
Glibert compared long-term trends to find
correlations between discharges from Sacramento,
Delta water quality and the kinds of plants and animals that grow there.
"The statistical method she used exaggerates
trends, and suppresses the very real effect of
natural variability," said Wim Kimmerer, an
estuarine ecologist at the Romberg Tiburon Center
at San Francisco State University.
"The overall approach is also based mostly on
correlation and ignores important influences that
we have learned about through more detailed
methods, such as the effects of clams and other
introduced species on the food web of the estuary."
In early 2005, state biologists who track the
Delta's fish populations noticed a sharp decline
in several fish species, setting off alarms that
the Delta was in a widespread and unexplained ecological decline.
Since then, California's salmon population joined
the collapse, for reasons that scientists have not untangled.
But in each case, most researchers agree that the
state's system of delivering water through the
Delta is at least part of the problem and other factors also contribute.
Ammonium from the Sacramento sewer plant, which
discharges an average of 145 million gallons a
day of treated sewage, has for few years been
near the top of that list of other potential
causes for the collapse, but most of the focus
has been on whether ammonium discharges might be poisoning fish.
Glibert said the problem was more subtle.
The increase in ammonium changed the kinds of
algae that thrive in the Delta, and that change
rippled up the food web, she concluded.
Before 1982, the nutrients in the Delta were
mostly nitrate and phosphorus, which fed algae
called diatoms that in turn were eaten by
zooplankton that made up the food that Delta smelt and other native fish eat.
That food web changed in the 1980s and 1990s, and
in a third "era" identified by Glibert, since
2000 the base of the Delta food web is mostly
ammonium and blue-green algae, which in turn are
favored by another kind of zooplankton that is in
turn favored by non-native fish, like inland silversides.
While her paper focused on one potential source
of stress on fish, Glibert acknowledged that the
National Research Council panel of which she is a
member would likely find other problems in the
Delta by the time it completes its study of the Delta's problems in late 2011.
"There is no doubt that when we look at other
stressors we will find additional effects," Glibert said.
Mike Taugher covers the environment. Contact him at 925-943-8257.
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