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Invasion of the Bay Snatchers

Local scientists battle aquatic invaders that quash biodiversity and threaten state coffers.



Erik Grijalva stands on a levee on the Hayward shoreline, hands on hips, surveying the surrounding acres of blackened, rotting plant stalks with the air of a man who is incredibly pleased with his work. "This looks great," he says, nodding at the scarred remains of the meadow.

Grijalva and colleague Drew Kerr are weed-control specialists on a major scale, and their current task is a rather audacious attempt to save sixty thousand acres of San Francisco Bay shoreline from a fast-spreading East Coast cordgrass called spartina. Central to their plan is the mass application of herbicide to thousands of acres of bay marshes, which they hope will eventually eliminate one of the Bay Area's most extraordinarily successful invasive species. "This time last year, this was all green and happy," Grijalva says, waving at the dead plants. "We were very concerned about being able to treat it. Now that we see it, we're very pleased."

Which begs the question: What's wrong with green and happy, even if the green and happy plants aren't from these parts? Why throw millions of dollars and thousands of hours at the problem, when one species outhustling another is the whole idea that got that guy Darwin famous? Shouldn't we simply, as the famed British philosopher McCartney said, let it be?

This is a common query, and one that complicates life for everyone working to keep invaders out of the bay. The short answer is that many of these travelers, spartina included, are major destructive nuisances that spread rapidly and blot out the biodiversity around them. Spartina is just the green-and-leafy tip of things. Aquatic invasive species, many scientists agree, are the biggest environmental problem you've barely heard of. They're also one of those problems that, left unchecked, could end up costing us huge sums of money. The San Francisco Bay, by many accounts, is one of the planet's most-invaded aquatic ecosystems. It is so thoroughly colonized that most prevention efforts now focus on keeping new invaders from displacing long-established ones. The leading scientific study of the bay's invasive species, a 1995 survey by biologist Andrew Cohen, notes that it's difficult, if not impossible, to find things in the bay that were around two hundred years ago. Try it yourself: Head out to a dock, grab a fistful of stuff from a piling, and sort through it. Maybe you'll get some Japanese sea squirts, or an Atlantic sea slug, or some exciting, flame-colored red-beard sponge from Nova Scotia. Whatever you find will be a far cry from what you would have pulled out two centuries ago — not that we even know what that was. "We should spend more time thinking about that," says Cohen, who runs the biological invasions program at the San Francisco Estuary Institute, an Oakland-based nonprofit.

For example, Cohen has been reading reports from the 1830s about people collecting octopuses from the bay. The mollusks were said to be so plentiful that people walked along the shore with bags and pulled them from tide pools. "I've never seen an octopus in the bay, and I don't know anyone who has," Cohen says.

Some exotics don't cause problems. But others do: Spartina, European green crabs, Chinese mitten crabs, the ominously named water plant hydrilla, Australian oyster drills, Asian worms, New Zealand snails, and the entrenched Asian clam, to name a few. "You're not going to be able to get the Asian clam out without killing everything," says Karen McDowell, an environmental planner with the state-run San Francisco Estuary Project. (See sidebars: Spartina!, Hydrilla!, The Overbite Clam!, The Nuclear Worm!, The Asian Swamp Eel!)

Each of these invaders graces the bay or delta with its own suite of destructive tendencies — clogging pipes, fouling ship hulls, choking off water surfaces, altering the food chain, introducing parasites, or reengineering the immediate environment to suit its needs. One by one they're nuisance enough, but taken together, invasive species place major stresses on the bay ecosystem.

Among the biggest concerns is the uncertainty that creates: Scientists just don't know what the outcome will be, and because the bay is changing so quickly, it's hard for them even to keep tabs on it. "It's like the global warming change," says McDowell, who is overseeing the drafting of California's aquatic invasive species management plan. "Eventually, if we do enough damage to our aquatic environment, people will wish we hadn't."

The Asian clam — which Cohen says should be called the overbite clam, since there are actually several varieties of clams from Asia — is a good example of a reckless environmental engineer. For roughly two decades, scientists had studied the fairly stable ecology of the North Bay, and its annual summer phytoplankton bloom that constituted the base of the food chain for many bay critters. In 1986, the overbite clam arrived, probably after being dumped with a ship's ballast water. The mollusk, which sucks in and filters the surrounding water of nutrients, began to multiply rapidly. By 1988, its bay floor density was estimated in some places at fifty thousand clams per square meter. That same year, the plankton bloom disappeared entirely, possibly for good. Clams one, science zero.

Invasive species experts also fret about the baddies that aren't here yet but may be on the way, such as quagga mussels, an East Coast scourge discovered in a Southern California lake this past January. If quagga mussels make it to Northern California, they are likely to clog up the pipes of the State Water Project, which supplies drinking water to 23 million people and irrigation for the Central Valley's multibillion-dollar agriculture industry. The mussels spread so fast, grow so thick, and filter so many nutrients from the water that they also are expected to wreak havoc on local species such as salmon and Delta smelt.

Quaggas and their close relatives, zebra mussels, "are two of the most devastating invaders to arrive in North America," says Cohen, who is leading the state's scientific response to the threat. "They're responsible for hundreds of millions of dollars of straightforward economic damage on the East Coast, and there's no reason to think it'll be any different here on the West Coast."

A lot of that damage has been to nuclear power plants, which tend to have their underwater equipment clogged by mussels, but quaggas also attach to boat hulls, docks, breakwaters, navigational aids, firefighting and air-conditioning systems, water treatment gear, and so on. Quagga and zebra mussels have also threatened or destroyed native species of fish and shellfish, especially in the Great Lakes region, and left nearly barren water behind.

Cohen says he's recommended that the state attempt to eradicate the quagga mussels from Lake Havasu before they spread. Just consider that for a moment: He wants to exterminate colonies of one-inch mussels hidden who knows where within a large lake that's popular with recreational boaters. "It's daunting, and to many people it's insane," he says. "But we need to think on a military kind of scale about this thing. If you think at that scale, it's entirely possible."

While quagga mussels top the list of Things That Aren't Here Yet but Could Be Soon, several other potential invaders operate at a slightly less worrisome scale. These include giant Salvinia ferns ("one of the world's worst aquatic pests," the state's draft management plan says), Asian swamp eels, Chinese snakeheads ("a voracious predator"), and, strangest of all, a hot-pink, six-foot-long Vietnamese annelid known as "the nuclear worm," which fishermen like because they can easily cut it up for bait. "The nuclear worm is the biggest, baddest worm on the block," Cohen says. "We don't even really know what it is, except it comes from somewhere like the Mekong Delta."

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