Researchers document eelgrass wasting disease in Washington
By KIMBERLY CAUVEL
Nov. 12, 2017
ANACORTES, Wash. (AP) — Squatting on a muddy beach on the north end of Fidalgo Island, Morgan Eisenlord untangled several slippery strands of eelgrass.
Most of the strands were a shiny green, similar to giant, damp blades of grass. Some bore patches of brown — a sign of eelgrass wasting disease.
Eisenlord — a Cornell University doctoral student doing her dissertation at the University of Washington's Friday Harbor Labs — is searching for the disease in areas on Fidalgo Island and on the San Juan Islands.
"We know it's here, it's prevalent and it's affecting eelgrass," Eisenlord said of their findings.
The primary goal of Eisenlord and others working on the research is to document where in the region the disease is found and how much of the eelgrass in those areas is affected. That baseline data is needed in order to watch for changes in the future.
The researchers also hope to eventually answer questions such as how big of a threat the disease is in the Pacific Northwest, whether global climate change will amplify that threat and if anything can be done to prevent or stop the disease in the Salish Sea, which includes the Puget Sound, Strait of Juan de Fuca and Georgia Strait.
"We care a lot about eelgrass ... In our waters it's essential for both herring and salmon. A lot of herring spawn in eelgrass beds and a lot of salmon feed in eelgrass beds," researcher Drew Harvell said. "Given that it's such a really, really important marine habitat, anything that is contributing to its decline is a problem."
DOCUMENTING THE DISEASE
Eelgrass wasting disease has long affected the important marine plant in parts of the world. The East Coast of the United States saw a steep decline in eelgrass beds during an outbreak of the disease in the 1930s, according to the National Oceanographic and Atmospheric Administration.
More recently, the disease was documented in the Pacific Northwest. The disease does not appear to have caused a major decline in area eelgrass beds, according to research being led by Harvell, a Cornell University professor.
After studying the impacts of other diseases on coral reefs, Harvell said she developed an interest in eelgrass wasting while working at Friday Harbor Labs on San Juan Island.
In 2012, she began teaching a graduate course there on marine disease ecology.
It was through that course — during which students surveyed eelgrass beds at 11 sites in the region for signs of wasting — that Harvell realized the disease was prevalent in area waters.
"We were impressed to see how high the level of infection was at some of our sites," she said.
Since they started investigating eelgrass wasting disease in area waters, Harvell's students have helped determine the disease is caused by a type of single-celled organism called protozoa and that there are multiple strains of the disease.
Affected parts of the leaves die, turn brown and can cause the portion of the leaves above the affected areas to break off and float away.
"We haven't observed it actually killing the whole plant, but we are seeing it limiting growth," Eisenlord said.
The data collected over the years has also shown that the presence of the disease increases during the summer.
PRESENT, BUT NOT PERSISTENT
Eelgrass wasting disease is caused by a microscopic organism that is always present in marine water.
In February 2014, a research paper by Harvell, her former student Maya Groner and others concluded that more research was needed to determine why the disease only sometimes affects eelgrass.
In addition to large outbreaks, the disease is found at higher rates in some areas than in others, including within some bays in the Salish Sea.
The disease is known to affect eelgrass plants when they are not strong enough to fight it off.
"It's opportunistic, like a cold, so if you have ... other stressors, it can take over and the plant can become overwhelmed," Eisenlord said.
It's unclear what conditions allow the disease to take hold.
Using data collected in 2013, another research paper by Harvell, Groner and others in 2016 suggested that older eelgrass and denser eelgrass beds are more susceptible to the disease.
It also showed that of the 11 sites surveyed, Padilla Bay in Skagit County had the highest rate of eelgrass wasting disease in plants sampled, at about 79 percent.
The other site surveyed in Skagit County, at Ship Harbor on the north end of Fidalgo Island, was at 43 percent.
On average, wasting disease was present about 34 percent of the time across all sites sampled, including the two sites in Skagit County and the nine in San Juan County.
Some suspect the disease may worsen in certain conditions such as warmer water.
Eisenlord and Jude Apple of the Padilla Bay National Estuarine Research Reserve said if warmer water does correlate with higher incidence of the disease, it could be problematic in the future.
"There's a potential for it to have a big impact if conditions change ... Just a few degrees can make it more prevalent and severe," Eisenlord said.
Padilla Bay has seen an increase in water temperatures in recent years, according to data from the reserve. Apple said while that could be a temporary trend due to short-term climate cycles, water temperatures are expected to increase in the bay due to climate change.
WATCHING FOR TRENDS
While continuing to collect data from those 11 research sites — now as part of a partnership with Western Washington University's Shannon Point Marine Center in Anacortes — Eisenlord has seen signs of eelgrass wasting increase and decrease at different locations.
Beach Haven on the north side of San Juan Island recently saw an increase.
"We only know for sure this year that that is not normal," Eisenlord said of the need for long-term data.
Western Washington University graduate student Tyler Tran, who is also studying eelgrass, helped Eisenlord gather leaves from plants at Ship Harbor and other locations this summer for further analysis in the lab.
While at the beach July 25, Tran slid leaves between his fingers to clear them of mud before winding them up like ribbon and placing each in labeled sandwich bags.
Many students have helped collect those types of samples in recent years in an effort to find out whether eelgrass beds such as those in Padilla Bay — one of the largest on the West Coast, according to NOAA — are at risk of declining or disappearing due to the disease.
The data shows the disease appears to be most prevalent in Padilla Bay.
Eisenlord said Padilla Bay is also one of the sites where the disease has increased since the research began.
Although the disease is present, researchers have not seen a steep decline of eelgrass in Padilla Bay.
Additional research involving students at Friday Harbor Labs and Shannon Point Marine Center is being done to determine how much area eelgrass beds are declining and how much of that decline may be directly related to the disease.
Information from: Skagit Valley Herald, http://www.skagitvalleyherald.com