Oregon's only native species of oyster, once deemed "functionally extinct" due to overharvesting, may hold the key to the future of the state's shellfish industry, researchers from Oregon State University said in a new study.
Researchers reported in the study the Olympia oyster is far more resistant to ocean acidification than its non-native cousin, the Pacific oyster. The results came as a big surprise to George Waldbusser, a marine ecologist in Oregon State's College of Earth, Ocean, and Atmospheric Sciences and principal investigator on the project.
"We were sort of shocked the first time" they looked at the results, Waldbusser said. "We assumed someone did something wrong, but we repeated the study with a new group of animals and got the same results."
The Olympia oyster--a smaller relative of the Pacific oyster, which is prevalent in oyster beds and on dinner plates up and down the West Coast--is a tough little mollusk, namely because it develops its shell over the course of days instead of hours, saving much needed energy that helps it resist the corrosiveness of the world's increasingly acidified oceans, Waldbusser said.
"This is a unique trait that allows native oysters to survive surprisingly high levels of acidification," he said. "But they didn't develop that trait in response to rising acidification. It has been there for some time. It does make you wonder if there may be traits in other organisms that we're unaware of that may be beneficial."
For the study, published Friday in the Journal of Limnology and Oceanography, researchers measured the calcium content of both Olympia and Pacific oyster larvae every three hours over the course of five days.
Pacific oysters have just a six-hour window after fertilization to develop their calcium carbonate shell. When exposed to corrosive water during this critical stage, the young oysters can rapidly deplete their energy reserves and, while they may succeed in building their shells, survival to adulthood becomes far less likely.
By contrast, the Olympias, or Olys, as they are often referred to in the culinary world, don't start developing their shell until two to three days after fertilization and do so at a much slower rate than the Pacifics.
Researchers found a seven-fold difference in the calcification rate between the two oyster species with the Pacific variety investing nearly all of their energy into building their shell.
That investment, however, comes at a cost.
"Pacific oysters churn out tens of millions of eggs, and those eggs are much smaller than those of native oysters even though they eventually become much larger as adults," Waldbusser said. It takes a lot of energy to build an oyster shell and because Olys produce fewer, larger eggs, each one uses less relative energy compared to the Pacifics during the early stages of development, according to the study.
Researchers at Oregon State are hoping cultivation of the Olys, with their corrosive-resistant shell-building habits, could spell some relief if a catastrophic loss of Pacifics takes hold.
Environmental experts and those who make their living farming shellfish agree, the increasing acidity of the ocean, specifically in the Pacific Northwest, is already taking a toll on the industry.
In 2015, the National Resources Defense Council released a report laying out a stark future for the region: ocean acidification -- a chemical imbalance in the water caused by carbon dioxide emissions -- is hitting Oregon and Washington harder than other parts of the country, in part because so many people here rely on shellfish to make a living.
And if you ask those who farm the the mollusks commercially, they'll tell you the same thing. A 2015 survey of shellfish farmers, conducted by Oregon State, found that 75 percent of those asked reported some level of concern over ocean acidification. Of those respondents who said they have been affected by ocean acidification, 97 percent reported financial damage, while 68 percent cited emotional stress.
It remains to be seen if the Olys can establish a foothold in Oregon after they were nearly wiped out in the early 1900s. The mollusks were abundant up and down the coast long before Europeans made their way west, but when gold was discovered in California in the mid-1800s the ensuing gold rush translated into a rush on the petite shellfish as well.
As the supply in San Francisco Bay was depleted, shellfishermen loaded hundreds of thousands of pounds of Olys onto schooners and sailed them down the coast to sate the appetites of hungry miners.
Oly beds in Oregon and Washington were virtually wiped out. The annual harvest of Olympias in Washington peaked at 130,000 bushels in the 1890s, according to the Nature Conservancy. By 1910, however, the harvest declined to just 16,000 bushels a year and a 2013 study published last year in Proceedings of the Royal Society B, a scientific journal, dubbed the species "functionally extinct."
Conservationists are working on multiple fronts to restore the Olys, however, and have expressed guarded optimism that the species can make a comeback.
Other studies have shown that Olympias can be sensitive to acidification in later stages of their lives, Waldbusser cautioned, but he said it may be possible to breed some of the Olys' beneficial traits into Pacific oysters over time -- either slowing the calcification rate of early larvae or producing fewer and bigger eggs.
Waldbusser said the study provided some hope for other species as the Olys' beneficial traits did not come about as an adaptation to ocean acidification, but were preexisting and did not require the long evolutionary adaptation process to give them a better chance for survival.
"Here's a trait they already possess," he said. "It gives us hope that there are ways organisms can persist in our changing ocean environment."
Read the study here: http://onlinelibrary.wiley.com/doi/10.1002/lno.10348/abstract
-- Kale Williams