Oysters and eelgrass, unlikely heroes in the fight against rising seas

Margot Buchbinder dipped her hand into a tank filled with murky seawater and swaying strands of native California eelgrass. She fished around with the intent of a prospector panning for gold and pulled out a small, green-striped blob, which curled up slowly in her palm.

“When we see these,” said Buchbinder, a graduate student in ecology at San Francisco State University Romberg-Tiburon Center (RTC), “that is generally a good sign.”

The curling blob, Buchbinder said, is a native sea hare, a slug-like animal that cleans parasites and algae from eelgrass. It’s one of the “good guys”—an indicator that the eelgrass ecosystem in the San Francisco Bay, partly mimicked here in the tank, is healthy and functioning, with several important organisms present.

This tiny ecosystem in a tank at RTC is one of several sites where research supports 15 regional and national organizations that are working to create reefs and underwater habitat—like that along the Richmond shoreline in spots from the San Rafael Bridge to Point San Pablo—to protect the physical shorelines lined with beaches, parks, homes and developments.

Along Richmond’s western shoreline, scientists and conservation groups working with the Living Shorelines Project, as this group of organizations is known, are now showing that species such as sea hares, eelgrass and even oysters shield the shore from erosion. And that means that protecting such species and expanding their habitat may help guard against the rising sea levels expected to accompany climate change.

“The majority of our research, at this point, has somehow to do with climate change,” said Erin Blackwood, the Education and Outreach Coordinator at the RTC, whose researchers also work to expand marine organisms’ habitat in the bay itself.

The hope behind the Living Shorelines Project is that such habitat, if restored on a large scale, can protect communities along the bay from sea levels that may rise several feet before the century’s end.

A hundred years ago, the murky habitat of the sea hare, eel grass and Olympia oyster dominated large swaths of Richmond’s shoreline. Expansive marshes reached into what is now the city of Richmond.

That habitat started to disappear with the Gold Rush in the mid-1800s. At the turn of the century, Standard Oil (now Chevron) began building a refinery on 150 acres of marshland, and in the decades that followed, developers built levees and dikes to cut off the flow of water from upstream estuaries. During the second World War, even more marshland was filled in and paved to accommodate the city’s industrial boom.

All told, between 1800 and 1998, 42 percent of mudflats and 79 percent of bay marshes were eliminated, according to a 2015 report by the California Coastal Conservancy, which manages the San Francisco Bay Living Shorelines Project. Currently, San Francisco Bay has roughly 42,000 acres of tidal wetlands, including marshes and mudflats, which is less than 15 percent of the bay’s historical coverage in the mid-1800s.

Industrial activity left much of Richmond’s waterfront heavily polluted and lined with abandoned concrete structures. Mining in the Sierras inundated the bay with sediment that came down into the watersheds. Chemical contaminants from ammunition factories and naval fuel storage facilities left tracts of land—such as Point Molate—toxically uninhabitable for decades. The abandoned wartime shipbuilding industry left once bustling structures vacant along the shoreline.

In recent years, Richmond has considered large-scale developments for its waterfront, but they’ve often been contentious. Berkeley’s Global Campus, a prospective multimillion dollar research facility, fell through after failed community negotiations and the university’s budget challenges. Projects such as the Terminal One development, a housing and park development planned for a historical pier, was stalled until recently by a neighborhood group’s lawsuit. And Richmond voters thwarted a developer’s plan to build a casino at Point Molate in 2011.

Despite such plans, Richmond’s shoreline is relatively undeveloped when compared to Bay Area cities such as San Francisco and Oakland. Much of Richmond’s 32 miles of waterfront is developed, but tidal marshes, mudflats and wetlands have kept a tenuous hold.

Over the course of the next hundred years, Richmond’s shores will face a wholly different threat: rising seas.

A 2012 report by the National Research Council, a nonprofit dedicated to informing the public about science, estimated that sea levels in the San Francisco Bay will rise at least one and possibly more than five feet by the year 2100. Scientists are fairly certain that the consequences for Richmond’s shorelines could be vast.

“Many cities and counties in the bay are really working hard on addressing climate change—doing climate risk assessments, figuring out what’s at risk and how we might adapt to that,” said Marilyn Latta, a project manager at the State Coastal Conservancy.

City officials in Richmond have already taken action. Richmond’s General Plan 2030, a framework to guide growth and development that was adopted by City Council in 2012, said the city needed to combat climate change by “restoring and expanding ecological systems” and “conserving and protecting wetlands.”

This year, in October, Richmond adopted the Climate Action Plan, which sets citywide goals for energy conservation and greenhouse gas reduction in order to mitigate the effects of climate change.

“We need to be considering ways to mitigate a sea level rise that is bound to happen, at the same time that we regulate emissions to make sure it doesn’t become any worse,” said councilmember and former mayor Gayle McLaughlin.

Richmond’s Climate Action Plan focuses on combating climate change through emissions and energy use reductions, and says far less about habitat restoration.

But habitat restoration is an important way to make shorelines resilient to climate change, said Letitia Grenier, Program Director and Senior Scientist at the San Francisco Estuary Institute, a partner organization in the Living Shorelines Project.

Oysters and eelgrass create habitats that slow waves and trap soil that runs into the bay. Softer waves and less soil, or sediment, means less erosion of the shore. As sea level rises, erosion breaks down the shoreline, as the sea moves inland and into the city.

“You could always build a sea wall or some kind of levee to reduce wave energy,” said Kathy Boyer, Science Lead at the Living Shorelines Project and a professor of ecology at RTC. “We’re trying to have a similar kind of function while providing valuable habitat.”

Boyer’s team of researchers does just that by building “reefs” out of something called baycrete, a human-made material largely composed of cement, sand and clay from the bay. The researchers place baycrete with oyster shells collected in netted bags, which attract oyster larvae floating naturally in the water. The larvae then settle on and repopulate the reef.

As oysters begin populating the baycrete reef, they immediately start doing what they do best: filtering water. Oysters in the bay essentially function like the pump on a pool: as “filter feeders,” they draw water into their bodies and then send it back out free of organic particles. They draw the water in for sustenance, but in doing so also remove sediment and contaminants, such as runoff and heavy metals. Even small oysters can filter more than two gallons of water per day.

Once the oysters are established, they also provide a base on which other species—such as small invertebrates, algae and fish—can live and grow. And by filtering the murky water, the oysters allow light to penetrate deeper into the water column, which may help plants such as eelgrass to thrive.

In short, the oyster acts as a foundational species that lays the groundwork and makes the area habitable for others. Both oysters and eelgrass beds act as basis in this ecosystem: their presence allows other species, from microscopic zooplankton to large fish, to reproduce and feed in and around them.

Boyer’s team began this work with a small reef on the San Rafael shoreline in 2012, followed by two tracts of eelgrass planted between the San Rafael-Richmond Bridge and Point San Pablo in 2015.

Already, dozens of species are using the reef, said Latta. And at one location in the bay, scientists found that the baycrete reefs have reduced wave energy by 50 percent—which in turn will mean less erosion, Latta said.

As sea levels rise over the coming decades, more and more marshland will be submerged.

Grenier said that if housing and commercial development borders the marshland too closely, the oysters and eelgrass that help protect the shoreline from erosion will have no place to go.

In anticipation of such development, the State Coastal Conservancy is also supporting efforts to expand the marshlands themselves. One such project, the Breuner Marsh expansion, began three years ago when East Bay Regional Park District (EBRPD) acquired the land by eminent domain. The project has already restored 60 acres of marsh along the Point Pinole Regional Shoreline and when finished next year will include picnic areas and walking paths, and a new connection between two segments of the San Francisco Bay Trail.

The Breuner project has been funded by $7.8 million in grants from the Environmental Protection Agency, the State Coastal Conservancy, the U.S. Fish and Wildlife Service, and other organizations, with EBRPD, the lead organization, footing an additional $6.2 million.

In the next few years, such projects could see a significant funding boost, said Contra Costa County District I Supervisor John Gioia, a governing board member of the San Francisco Bay Restoration Authority (SFBRA), a regional government agency that raises and allocates resources for restoration.

In the June 2016 election, voters in nine Bay Area counties passed Measure AA, a regional mandate to provide about $500 million over the next 20 years for bay restoration projects.

Gioia said that the SFBRA, which put the measure on the ballot, does not cover the entire cost of bay restoration, but rather uses funds to fill any gaps.

He also said that while habitat restoration projects provide many benefits, including mitigation of sea level rise, they’re not the only means of protecting against the potential consequences of climate change.

“They play a role, but they’re not the only strategy,” he said.

Currently, the State Coastal Conservancy is in the final stages of planning a design for Giant Marsh, an expansive restoration project just off Point Pinole that includes an underwater oyster reef, eelgrass and expanded marshlands.

Later this year, the State Coastal Conservancy will submit permit applications to the San Francisco Bay Conservation and Development Commission (BCDC), a state regulatory agency that oversees development projects in the bay, the US Army Corp of Engineers and other regulatory agencies. If the permits are issued, the Giant Marsh restoration could begin as early as Spring 2017.

Grenier said that continued funding for restoration projects is necessary to ensure that future city planners aren’t forced to make panicked, last-minute decisions once the effects of climate change become impossible to ignore.

“It’s hard for people to see that sea level rise is actually happening,” said Boyer. “Once they see it there could be general panic, and the inclination would be to throw up sea walls… We are hoping to get up in front of that with these projects.”