As often happens with inconspicuous and little-understood species, eelgrass has suffered greatly from human impacts. Yet as understanding of the plant’s many and diverse functions has grown, efforts to protect and restore it have begun. On the West Coast, the earliest restoration effort dates back to the 1970s, in San Diego. Other early projects were undertaken in Puget Sound, British Columbia, and Alaska. Elsewhere in California, numerous restoration projects are being planned to mitigate impacts of development, but most have not yet been implemented. New construction on the Oakland–San Francisco Bay Bridge has brought increased attention to eelgrass in San Francisco Bay, and has sparked active interest in bringing it back to health there.

“When a diver is swimming over bare, featureless bottom and comes to an eelgrass bed,” said Coastal Conservancy project manager Abe Doherty, who did his graduate study on eelgrass, “it’s like finding Las Vegas in the desert—suddenly there’s color and life everywhere.”

“Eelgrass provides vertical structure to an otherwise unstructured environment,” said Keith Merkel, whose company, Merkel & Associates, has pioneered in developing Zostera marina restoration techniques in California. Unlike a featureless sand or mud bottom, eelgrass creates the equivalent of an island or forest, where an abundance of creatures can live, breed, and feed.

The rich, soft bottom is an ideal home for various worms, sea pens, and other benthic (bottom-dwelling) creatures, and the long waving blades make perfect habitat for all sorts of invertebrates. Herring particularly favor eelgrass beds for spawning, and a plethora of marine species—including snails, nudibranchs, stalked jellies, and colonial bryozoans, not to mention various algae—lay eggs or make their homes on the green blades. On a recent visit to an eelgrass bed in the Seal Beach National Wildlife Refuge, Orange County naturalist Tim Anderson spotted eggs of Navanax inermis, a large carnivorous sea slug; California sea hare (Aplysia californica); and opalescent nudibranch (Hermissenda crassicornis); as well as lacelike bryozoans, calcareous tubeworms, sea stalks, and sea squirts. Eelgrass meadows provide feasts of sea stars, urchins, worms, and snails for Dungeness and other crabs, while surfperch, sculpins, and other predacious fish seek prey that hide among the leaves. Some birds feed by scraping off the many creatures and plants that make their homes on the leaf blades. Christopher Kitting, professor of biological sciences at California State University East Bay, said he and his colleagues have shown that “the tiny epiphytic algae that grow on eelgrass are the basis for eelgrass community food webs. Many of the small crawlers feed on the algae, and they in turn are eaten by larger creatures.” Other animals, from tiny snails to black brant geese, graze on eelgrass leaves. Eventually, spent eelgrass blades wash offshore, where they become food for detritivores and eventually decay and enrich the sea bottom. “We’re not sure why,” Kitting added, “but eelgrass communities in southern California bays are surprisingly rich, much more so than in San Francisco Bay.”

It may be that the growing popularity of recreational diving in southern California in the 1980s drew more attention to this important but unappreciated plant, according to Merkel. Before “people started putting their heads under water and seeing the complex communities in the beds,” he said, “eelgrass was the orphan stepchild of marine resources.” Increased appreciation led to policy changes that have raised the priority of eelgrass protection and restoration.

It’s difficult to say how much eelgrass there is in California. Merkel estimates there are at least 12,000 acres, and possibly more than twice that much. Surveys have not been comprehensive enough to provide more reliable data, and eelgrass coverage fluctuates by at least hundreds of acres annually, in response to weather patterns, variations in water temperature and salinity, and other conditions.

Extreme weather events such as El Niño may raise sea level sufficiently to cut off the sunlight that the plant needs for photosynthesis, as can excessive turbidity. With sea level rise, many eelgrass beds will be extinguished unless they can expand into adjacent shallower areas. Increases in agricultural runoff or sewage flows can kill eelgrass by eutrophication (i.e., excess nutrients induce excessive algal growth that deprives the leaves of sunlight). Variations in temperature and salinity can also have harmful results: high salinity may turn a slime mold, Labyrinthula zosterae, that normally causes little damage, into an eelgrass killer. (The pathogen has also been described as a fungus, Labyrinthula macrocystis.) The wasting disease it causes led to a collapse of eelgrass populations in the North Atlantic in 1930–33.

Even in relatively stable conditions, eelgrass beds will change in size with the seasons and the plant’s life cycle. As a flowering plant, it produces seeds and spreads through sexual reproduction, but it also reproduces asexually, putting out new plant-forming roots from its rhizomes. Either of these modes may predominate, depending on local conditions. In beds that grow mostly from seed, the plant behaves as an annual, while rhizomal propagation creates perennial colonies. Annual plants flower four or five months after sprouting, but perennials go through a longer cycle, spreading rhizomally before flowering. Perennial beds tend to be more persistent, but because the individual plants are clones, they may lack genetic diversity, which leaves them more susceptible to adverse conditions.

Eelgrass habitat has been protected since 1972 by the Clean Water Act, but only since 1991 has mitigation been required as a condition of permitting for projects that cause loss of eelgrass. The first West Coast eelgrass mitigation project was undertaken in San Diego, as an exploratory partnership between the U.S. Navy, the National Marine Fisheries Service, and the California Department of Fish and Game. “Early mitigation efforts,” Merkel said, “grew out of increased recognition of the importance of habitat linkages and the significant impacts of development and dredging.” Eelgrass not only creates its own habitat; it also improves conditions in surrounding habitats and establishes important connections between them.

Surveys done with side-scan sonar, from the air, and by divers using underwater video can put together a fairly accurate picture of the extent of eelgrass beds. This information, combined with knowledge of conditions suitable for eelgrass, provides a starting point for restoration projects. No reliable record exists of the historical extent of eelgrass in California waters, so scientists try to identify good restoration sites based on conditions that favor success. Eelgrass studies in southern California and the Pacific Northwest have gone on long enough that it is now possible to predict with considerable accuracy how the plant will respond to varying conditions and restoration methods.

Since the ’70s, techniques have been refined and developed for greater efficacy at lower costs, with considerable success. In Batiquitos Lagoon, in San Diego County, for example, one-quarter acre of transplants in 1997 have now propagated to cover more than 50 acres. (See www.batiquitos.org.) Merkel said that the projects he has been involved with have been very successful in Mission Bay and elsewhere in Southern California, helping his company to develop improved predictive models and restoration methods.

Eelgrass can either be seeded or planted. Planting requires divers to harvest plants from healthy beds, then transplant them. The less time divers need to be under water, the less the project costs, so planting sparsely is the preferred method. In about three years transplants can begin to function as natural beds—under favorable conditions they spread fairly rapidly, filling in empty spaces. In places where eelgrass behaves as an annual, seeding is more likely to succeed than transplanting. Several of the more robust beds in San Francisco Bay are annuals, so proposed mitigation and restoration projects there may require using several techniques, depending on specific sites and conditions. Katharyn Boyer, assistant professor of biology at San Francisco State University (SFSU), and team leader for fledgling eelgrass restoration projects in the Bay, hopes that using “seed buoys” will be successful. This method involves harvesting flowering reproductive shoots from a donor bed, rather than taking whole plants. The shoots are put into mesh bags attached to buoys anchored at the target site. When the seeds mature, they fall through the mesh and scatter over the soft bottom.

Restoring eelgrass beds is not always a matter of scattering seeds in good spots. Not only must site-appropriate planting methods be used, but the habitats may need considerable preparation as well. A new eelgrass bed is being planned for Middle Harbor, an obsolete industrial harbor dredged out of shallow baylands in the Oakland Estuary. The Port of Oakland will use six million cubic yards of sediment dredged from active shipping channels to raise the substrate to a level suitable for eelgrass restoration. Such opportunistic efforts are especially helpful in places where eelgrass habitat has been destroyed by dredging or filling. Current plans call for transplanting eelgrass there, though if seed buoys work well in other Bay sites, said Boyer, they also may be adopted for Middle Harbor.

Sandy Wyllie-Echeverria, a research scientist at the University of Washington, emphasized that “the data we have for the Bay now amounts to snapshots—there’s been no sustained or frequent monitoring of eelgrass there.” He is working with Boyer’s team of scientists from NOAA and SFSU’s Romberg Tiburon Center for Environmental Studies to plan a series of eelgrass restoration projects in the Bay that will be funded, in part, by the Coastal Conservancy. Better monitoring would include assessing variations in bed size from year to year, calculating resilience and recovery rates of existing beds, and determining the impacts of, for example, ghost shrimp harvesting, bird use, and bat ray burrowing, in addition to the usual studies of water depth and quality.

First the group will conduct two experimental seed buoy projects, at sites near China Camp and the Marin Rod and Gun Club, in the North Bay. “One strength of this group is that we’re getting eelgrass genetics into the project early,” said Sarah Cohen of SFSU. “These will be among the first seagrass restoration projects in the U.S. to consider genetic diversity from the beginning. Studies show that eelgrass beds with genetic diversity do better in a whole suite of critical parameters.”

Inconspicuous as it may be, eelgrass has been used for many purposes worldwide, and continues to reveal further potential as a plant of economic significance. In northern Europe, the leaves that wash up on shore in the hottest part of the year traditionally have been gathered and used for insulation, thatching, and as fertilizer. The dried leaves are woven into rugs, mats, and baskets. The first commercial blanket insulation was made from eelgrass, but that business succumbed to the wasting disease epidemic of the 1930s. On the North American West Coast, indigenous people harvested the seed, which has high nutritional value, to grind into flour; some tribes also ate the rhizomes.

Eelgrass beds are now being restored mainly for environmental benefits: stabilization of soft bottom sediments, improved water clarity, and creation of rich habitat for a wide variety of animals foremost among them. The wave-damping effect of eelgrass beds is also drawing attention as a possible alternative to shoreline armoring in places with suitable offshore habitat. At first glance this remarkable plant seems simple and nondescript, yet the more one learns about it, the more fascinating it becomes.

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