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El Niņo: The Good, the Bad and the Ugly
Though El Niño browned the Bay and clouded the skies this spring, this periodic ocean-atmospheric disruption named for the Christ child can't be blamed for everything. Scientists looking at the life below the brown chop are finding that most critters are weathering the deluge of mud and freshwater runoff fairly well, and that in the South Bay aquatic springtime is filling the water with more blooms and blossoms than anyone has seen in the past quarter century.
The most obvious impact, the brown Bay, alarmed the local citizenry more than the biologists. This March, TV reporters listened as callers claimed the Bay was "dying" and blamed El Niño. But when the media finally questioned scientist Jan Thompson about the cause of the brown water, she pointed out that similar conditions occurred in 1997, long before El Niño's rebirth.
Like last year's "Pineapple Express" from Hawaii, El Niño's rains sent masses of new sediment and water into the Estuary. But the impacts were much more spread out and even than the sudden havoc of last year's storms. Levees haven't failed - in fact the Central Valley remains largely unscathed. And contrary to early news reports, El Niño hasn't killed all the clams and other critters living on the Bay floor - by burying them in new mud - or deprived them of their dinners. "You have to remember that widely variable conditions are exactly what estuarine organisms are adapted for," says the U.S. Geological Survey's Thompson. "Before we put in dams and reservoirs they lived in a world like this." Clams crawl in their shells and hunker down until things get better, says Thompson, and pockets of survivors easily replace any losses by reproducing with unusual speed.
On a mid-March Geological Survey cruise from the North to the South Bay, hydrologist Cindy Brown noticed a couple of inches of new sediment and a few dead clams at the mouth of the Sacramento River, but plenty of survivors crawling up out of the mud there and further down at Roe Island. At the Carquinez Strait, however, the bottom was completely "scoured clean" of mud, says Brown, much more sothan in previous high flow years. Past the strait in San Pablo Bay she found no live clams at all, but she attributes this to their intolerance for fresh water rather than smothering. Indeed the flush of fresh water has reduced San Pablo Bay salinity from a recent average of 12-25 parts per thousand to 4-19 ppt. But none of these conditions are going to "wipe out" the clams, says Brown.
Down in the South Bay, it's going to be a remarkable year in terms of biological production, according to the Geological Survey's Jim Cloern, also aboard the mid-March cruise. "It's like watching the trees bloom and the daffodils come up - the water column is coming to life. This the largest abundance of phytoplankton I've seen in 25 years," he says. The very high freshwater flows that have turned the North Bay "into a giant river" this year, according to Cloern, have also strongly stratified the South Bay water column, producing ideal conditions for a big spring bloom. The layering stimulates plant and animal growth in the fresher, sunlit upper layers. The amount of chlorophyll in the water - an indicator of plankton growth and food production - was more than double that of previous years (200 versus 70-80 milligrams per cubic meter), says Cloern.
Food out in the ocean has been scarcer, however, say others monitoring El Niño impacts. For example, some Pacific herring returning from the ocean to the Bay to spawn have been feeding instead, an unusual behavior according to Cal Fish & Game's Diana Watters. Watters says spawning biomass is down to 20,000 out of an expected 60,000 tons this year, and many of the already-tiny herring are not only underweight for their length, but are also carrying eggs with more than a normal share of abnormalities. "It's going to be a poor year for the fishery," says Watters.
Those nesting and burrowing on the wet edges of the Bay may not be faring so well either. The water level under El Niño has been a consistent 4-6 inches higher than recent averages, according to the Survey's Richard Smith. Add to this the 1-2 feet of extra water accumulating on a short-term basis with each storm and the result is flooding further up into the fringes of the Bay.
Endangered salt marsh harvest mice in these wetlands may have suffered from the El Niño flooding, particularly in backfilled marshes with steep sides and little escape cover, according to San Jose State mouse expert Howard Shellhammer. Where such species could historically flee up gentle slopes to wild hinterlands, such escapes from high water no longer exist on today's built up shores. Mice might now end up fleeing to levee tops where the "chances of them getting picked off by hawks goes up," says Shellhammer.
News of endangered California clapper rails is equally sketchy. U. S. Fish & Wildlife has had anecdotal reports of flooding in breeding territories during the season when rails begin to pair up. "It might have postponed breeding," says the Service's Jim Browning, "but the real effect is basically unknown."
While biologists may be celebrating the big blooms of phytoplankton, Jan Thompson also sees cause for hope in the citizen concern. "They're paying close attention to their Bay," she says. "Now it's up to us to better educate them about what's really going on."
Contact: U.S. Geological Survey (650)853-8300 or Howard Shellhammer (408)924-4897 or Diana Watters (650)688-6357.
For summaries of recent USGS cruises http://fbay.wr.usgs.gov/access/wqdata/index.html
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