[env-trinity] Contra Costa Times 5-18

Sari Sommarstrom 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.

Source questioned

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.

Potential causes

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.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www2.dcn.org/pipermail/env-trinity/attachments/20100519/46d36839/attachment.html

More information about the env-trinity mailing list