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So far, angler education (and probably a healthy squeamishness about giant pink critters) has kept the worm away. In many cases, educating people, especially boaters, about invasives is the only strategy available. Once something like the overbite clam gets established, it's unstoppable, and scientists have to hope the altered ecosystem remains stable long enough to study before a new invader moves in. Cohen can't even estimate the long-term cost of so many invasive species. Instead, he worries in the abstract: He speaks of potential "multiplier effects," "overload," extinctions, habitat loss. "With wholesale alteration of the environment, there's almost anything that can happen," he says.
On a recent morning, Andrew Cohen is sprawled on his stomach on an Alameda boat dock. Looking down at the underwater portion of the pilings, he laments a long-ago trip where he lost his eyeglasses to the depths. "I should have bungees or something," he says with a sigh, "but I'm just terrible at personal equipment management."
The biologist rips a handful of marine life off the piling and dumps it into a white plastic tray for inspection. He pulls out a "crust-of-bread sponge" from the East Coast. "Supposedly smells like sulfur," he says, squeezing and sniffing the brown, salty-smelling, finger-size tunicate. He grabs some red-beard sponge, also from the Atlantic, and teases out its waving red arms with a mud-slicked finger. He whips out his pocket lens to examine a tiny translucent shrimp from Japan. "It looks like a creature from Mars," he says, pointing at its three back legs and the pouch where it stores its young. "Just fascinating under the microscope."
There also are bryozoa from Florida, seaweed from Japan, and a tiny colony of beautiful orange petal-like sea squirts from France, which traveled to British Columbia before spreading down the coast all the way to Baja. What's missing are the native species. The California representatives amount to a couple forms of seaweed (which may or not actually be local), some local barnacles (which have turned the tables and invaded Argentina), and a native oyster in the process of being killed by a nonnative oyster drill from Australia.
Cohen has authored what are widely considered the seminal studies of invasive species in the bay: He conducted a 1995 survey that amounted, essentially, to a roll-call of the bay's varied expat aquatic communities, and published a 1998 paper in Science magazine that concluded the rate of invasion was accelerating. He counted 234 exotic species in the bay and delta in 1998, and compiled a guide that can be downloaded at ExoticsGuide.org.
These days, Cohen says, the exotics probably number around 275, but that's just an estimate he hasn't been able to find money to update the survey. In the world of environmental funding, invasive-species research gets chump change. Consider the National Oceanic & Atmospheric Administration, which, according to Cohen, is one of the top grant-givers. NOAA offers a paltry $50,000 for annual invasive species research in the western United States an area stretching from the Rocky Mountains to Guam and just $250,000 for the entire country.
As a result, few environmental groups can spare staff time to study the problem. "Invasion for a decade has been on everyone's lips as one of the three or four most critical issues," Cohen says. "Now all of the environmental groups list it as one of the key stressors, but no one's got a dedicated hour. Everyone agrees it's a big problem, but there's no funding, and no attention."
Cohen, however, is transfixed. He can't walk past a body of water without checking to see what's there. He leaps with delicious squelches into mud and muck to pull out dripping fistfuls of clams and sea slugs, and comfortably rattles off scientific names and terms like "underlying gelatinous matrix" to describe the sea squirts coating the underside of a rock.
On this morning, besides checking out Alameda docks, he wanders along the Oakland estuary at the base of the Fruitvale Bridge and surveys the exposed sand on Alameda's Crown Beach at low tide. By day's end, he's found 65 species, of which 41 are exotic, 16 native, and 8 of unknown origin. One milky, slimy lugworm egg case appears to be of a species previously unknown to the bay.
It's not that quarter-inch sea squirts present some huge threat to our collective future, but even the less harmful invaders help contribute to the decline and extinction of local species, and rapid changes in the bay environment.
Some of the species do affect people directly, such as the egg case of the Japanese bubble snail Cohen pulls off the underside of a rock near the Fruitvale Bridge. This yellow-dotted egg case carries a parasite called a schistosome, or flatworm, that typically embeds itself in the legs of water birds. Sometimes, Cohen says, it also will burrow into the exposed skin of waders or, say, biologists who stick their hands in the water.
Unlike many schistosomes, this one doesn't target humans deliberately, but it does cause a fairly nasty rash called "swimmer's itch," similar to poison oak. There was an outbreak at Crown Beach in 2005, with more than ninety people reporting rashes after wading. This particular problem doesn't have much of a solution because, like the crabs, clams, mussels, squirts, and seaweeds, the Japanese bubble snail isn't going anywhere.
While spartina doesn't specifically target people either, it does make a mess of expensive human conservation efforts. There are several cordgrass species around the bay, including one native species that's quite crucial to its local environment. But spartina became a problem in the 1970s. The Army Corps of Engineers was breaking levees to let the tides back into some former commercial salt ponds in Hayward and Fremont, and wanted fast-growing vegetation to aid the transformation. They discovered that an East Coast cordgrass variety seemed to spread quickly, so they planted it.
Let's just say their plan worked. The Atlantic species quickly crossed with the local cordgrass to create what scientists ominously label a "hybrid swarm." The new plants have varying traits and can adapt to all sorts of conditions. They fill up habitat-crucial mudflats where the native cordgrass doesn't go, fill in natural salt ponds where the native cordgrass can't live, and outcompete everything else. Left unchecked for a few years, the swarm eventually displaces all other plants, leaving marshes as homogeneous as Nebraska cornfields. This is bad news for restoration efforts around the bay. Conservationists have long dreamed of breaching industrial levees and letting the tides replenish what were once vast bay marshes and wetlands. But spartina has forced the US Fish and Wildlife Service, which oversees most of the salt-pond restorations in its 30,000-acre Don Edwards San Francisco Bay National Wildlife Refuge, to push back plans for breaching levees at several major sites.
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