Winter 2004
Growing Grass
by Drew Swayne
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Below the Boulevard Park boardwalk, life thrives in a submarine meadow of eelgrass. Sea anemones, marine worms, snails, limpets, crabs, birds, salmon and herring all depend on eelgrass.
“Many of the species that use eelgrass for habitat are species that we harvest — shrimp, crab, salmon — and when you lose eelgrass habitat you’re going to lose the fisheries,” said Glen Alexander, education coordinator at the Padilla Bay National Estuarine Research Reserve.
The native species of eelgrass found in Bellingham Bay, Zostera marina, grows in the muddy or sandy substrate of shallow subtidal zones down to a depth of 22 feet. Despite eelgrass’ importance, a variety of human activities threaten eelgrass and the species that depend on it. Dredging, filling in tidelands, prop wash from ships and urban runoff all can damage eelgrass and its habitat. Bellingham area groups, however, are making efforts to map habitat to provide information for eelgrass restoration.
The greatest value of eelgrass is the habitat it provides for valuable species, Alexander said.
Juvenile salmon are dependent on eelgrass for shelter from predators. Eelgrass also provides a home for copepods, small crustaceans that live on or near the bottom, which the salmon feed on, and provides shelter for Pacific herring eggs, which are laid on the eelgrass blades, said Erika Stroebel, Whatcom
County Marine Resources Committee resource planner.
To provide habitat, eelgrass must be able to reproduce. Reproduction occurs in two ways. Eelgrass most commonly reproduces by sending out rhizomes, which are horizontal, underground stems that send new shoots up through the ground, Alexander said. Eelgrass also reproduces as a flowering plant, by spreading seeds that produce new plants. Seeding is a slower method of reproduction but it allows eelgrass to spread over a greater distance.
“Seeds will spread on currents and tides so new plants can grow,” Alexander said.
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Because human activity has both intentionally and accidentally imported alien species to marine waters, eelgrass must fight with invasive species for its habitat. Threatening invasive species include Spartina alterniflora, a rhizomatous perennial grass that grows in salt marshes and is native to the Atlantic and Gulf coasts of the United States, and Zostera japonica, a Japanese eelgrass originally from the North Pacific coast of Asia.
Spartina is the more destructive of the two invasive species because it raises the elevation of mudflats by trapping sediments, which prevents eelgrass from colonizing in its natural habitat. Native eelgrass is no longer able to colonize because the new elevation is not within its natural habitat zone, Alexander said.
“It creates habitat that is not used by those native species,” Alexander said. “So it’s a net habitat loss.”
Alexander said the oyster industry introduced Zostera japonica to the Puget Sound area by using it to wrap imported oysters meant for cultivation in the area to keep them alive.
Chris Fairbanks, marine and fisheries biologist at Fairbanks Environmental Services, said Japanese eelgrass does not completely displace the native eelgrass because they grow at different depths. The two species overlap in the lower habitat zone of Japanese eelgrass and the upper habitat zone of native eelgrass causing them to compete for some of the same space. The non-native species has actually expanded total eelgrass habitat by colonizing in areas where Zostera marina cannot grow, and does not seem to be harming any other native species, Alexander said.
“The jury is still out,” Alexander said. “It is not clear that the introduction of Japonica is beneficial or detrimental. It is certain that it is not as detrimental as Spartina.”
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Eelgrass grows thick on the west side of Portage Island. |
The main cause of eelgrass habitat destruction in Bellingham Bay can be attributed to the expansion of Bellingham. Today, 90 percent of former estuarine habitat in the bay is dry ground, Fairbanks said. Squalicum Harbor and the rest of the Bellingham central waterfront area sit atop what used to be mudflats or near shore estuarine environment.
“(The shoreline) is so different now than it has been historically,” Fairbanks said.
Fairbanks said many types of shoreline and near shore development are threats to eelgrass habitat and restrictive management regulations are enforced to prevent habitat destruction.
The simplest type of damaging development is dock building, which shades the eelgrass from sunlight critical for photosynthesis, Fairbanks said. Other harmful developments include dredging because it removes the eelgrass and its substrate — the mud or sand on which the eelgrass grows — and large
vessels because their props create water turbulence that disturbs the substrate.
Fairbanks said for any shoreline development project to begin, it must first go through a number of regulations enforced by government bodies ranging from county shoreline management boards to the U.S. Army Corps of Engineers.
Despite increased habitat protection, protecting all eelgrass habitat is difficult because no comprehensive mapping program has ever taken place.
Fairbanks said that many unknown eelgrass beds probably exist between the known eelgrass beds, but they have not yet been mapped. When the correct habitat is available, Fairbanks said, eelgrass should grow.
“We assume that it can be continuous where the habitat is appropriate,” Fairbanks said.
So far Bellingham Bay has had one restoration project located at the Georgia-Pacific West log pond, adjacent to the G-P facility at the Whatcom Waterway, which was once used by G-P for storing log rafts. G-P designed the project to deal with contaminated sediments.
Eelgrass restoration was a side benefit. Under the Washington state sediment management standards, the Department of Ecology required G-P to cap and confine contaminated sediments located in the log pond. The contaminants in the log pond included mercury discharged from the pulp mill, wood debris from the log rafts and other contaminants, said Chip Hilarides, senior environmental engineer at G-P.
“As we were designing the project, we said ‘well, let’s design a cap to confine the contamination but also design a restoration project,’” Hilarides said. “We didn’t tell anyone that ‘darnit eelgrass is gonna grow, we’re sure of that,’ ’cause we weren’t sure of that.”
Hilarides said the cap’s design was meant to create sediment in the log pond at a proper elevation and with proper sediments to allow a habitat suited for natural colonization of eelgrass. The project was not specifically aimed at eelgrass restoration.
Hilarides said, however, that he had still hoped it would colonize naturally, which it did.
“Because our habitat action was a voluntary action, we wanted to see how it worked first before we went and did anything like (planting eelgrass),”
he said.
The project was completed in early 2001 and eelgrass appeared between the depths of two to six feet below the surface 18 months later. The eelgrass beds in the log pond are likely continuing to expand and grow, Hilarides said.
Intended to cap sediments and protect the bay, the log pond cleanup provided an opportunity for the eelgrass to come back. The eelgrass is already starting to show signs of establishing the habitat that make it such a vital part of the bay environment.