Oysters — North America

“Oyster farming is the kind of business an environmentalist should love: it doesn't use harmful chemicals or deplete natural resources, and the locally grown shellfish actually help clean the water… But when that industry sits on the lone feeding ground in the western hemisphere for the largest population of a threatened species of shorebird, things get complicated. New Jersey's oyster aquaculture industry is centered on the same Delaware Bay beaches that provide irreplaceable feeding grounds for the red knot on its annual 10,000-mile journey from South America to the Arctic…. A decision this month by the U.S. Fish and Wildlife Service allows oyster growers to expand their operations on the beaches, including some spots that host the largest concentrations of red knots.... The 17 farms in the area produced 1.6 million oysters in 2014, the most recent figures available, bringing just under $1 million to growers, according to Dave Bushek, director of the Haskins Shellfish Research Laboratory at Rutgers University. 'I think there's very easily room for both of these things to coexist,' he said."

“Scientists say they have only a vague idea of how many oysters cover the reefs in the Chesapeake Bay, and can't say how many can be harvested safely each year without threatening the future of an already decimated population. Over the next year and a half, they hope to figure it out. In the waning hours of its 2016 session, the General Assembly authorized a study that advocates say will not only provide a more precise count of the bivalves, but assess how quickly they are reproducing, how fast they are growing and how they are faring against disease…. ‘It's not going to be quick and it's not going to be easy, but it means [oysters are] going to be treated like every other fishery in the Chesapeake Bay,'said Del. Kumar Barve, a Montgomery County Democrat who helped negotiate revisions to the bill. "Our objective is to have a sustainable oyster harvest and a successful oyster-producing industry.'”

“The latest figures from the Chesapeake Bay Program — showing progress against the types of pollution targeted by federal mandates — are not just well timed but provide an encouraging message for the day: If you make an effort and give nature half a chance, it can recover…Those efforts are having an impact. According to the Chesapeake Bay Program, from 2009 to 2015, throughout the bay, nitrogen, phosphorus and sediment levels have decreased by 8 percent, 20 percent and 7 percent respectively. Water quality experts attribute this to less nitrogen and phosphorus in wastewater, lower nitrogen levels in the atmosphere because of the Clean Air Act and improved agriculture conservation practices... [And] there might be even more if we can boost the bay's population of oysters, the finest natural water filters in existence.”

On average, the sea is 30 percent more acidic than it was 200 years ago. And in the last decade, it began passing the point where young oysters can survive. "It’s not necessarily the acidity that causes problems for the oysters, but rather the concomitant lack of carbonate ions in the water. Shellfish use these free-floating ions to build their shells. When seawater absorbs carbon dioxide, the number of carbonate ions available for the shellfish is reduced."

"In the last 200 years, the pH of seawater worldwide has dropped from an average of 8.2 to an average of 8.1. A change in pH from 8.1 to 7.6 may not sound earthshaking, but that 0.5 pH drop indicates a 150 percent increase in acidity from the worldwide average—an increase that larval oysters are not equipped to handle."

In just 15 years, high-acidity days will occur throughout most of the summer. By 2050, according to an article published in the highly regarded scientific journal Science, acidity days are expected to persist year-round in many places along the West Coast. Oceans worldwide are eventually expected to be at least as acidic as the San Francisco Bay is today. The same water that threatens oysters... is poised to upend intertidal ecology, and many wild shellfish, including clams, mussels, snails, and oysters, are threatened. Fewer will survive, and those that do will be smaller and weaker, with thinner shells that are more vulnerable to being crushed by waves or predators.

"Some coastal waters are already experiencing conditions that shellfish larvae cannot tolerate, but the chemistry is complex and there are still many unknowns about how corrosive conditions will impact not only shellfish (such as oysters, clams and mussels) but also lobster, shrimp and other organisms that form the base of the marine food chain," "Given the importance of seafood to global nutrition and coastal economies, it is increasingly important that we conduct critical scientific research so we can better predict how various organisms will react to increasingly corrosive waters in the coming years," "We need to develop strategies that will help us mitigate and adapt to rapidly changing conditions.

"Most of the carbon dioxide released into the atmosphere is taken up by oceans, dramatically lowering pH levels in the process, and creating a chemical change that makes the ocean water more acidic. That increase in acidity creates a hostile habitat for oyster seeds (also called spat) and other marine life. Ocean acidification is especially harmful to oysters at their larval stage, when they’re building their protective coverings. Their fragile calcium carbonate shells don’t form well under increased acidic conditions, stunting their growth, making them more vulnerable to predators, and sometimes killing them outright. This sea shift can also stress small oysters, making them more susceptible to disease."

When seawater absorbs carbon dioxide, the amount of carbonate ions available for the shellfish is reduced. “A baby oyster is trying to eat, grow, move around, and make a shell. So if it spends more energy trying to make a shell, then something else in that equation is going to suffer.”

"Here on the West Coast, we have some of the most corrosive seawater in the world, thanks to a natural process called upwelling. Upwelling occurs when strong wind patterns cause water from the deep ocean to resurface along our shores, usually during the spring and summer. This water is always more acidic than surface water—it has spent 30 to 50 years in the ocean interior, absorbing carbon dioxide from everything that sinks and decomposes there. And today’s upwelled water carries the added legacy of higher acidity from carbon dioxide absorbed during the ’60s and ’70s, the last time the water was at the surface. As it returns to us now, it mixes with the more recently acidified surface water to create an extra-acidic oyster-killing brew.

The oyster industry made up of some 120 farms recovered in part by installing monitoring systems in hatcheries that ensure the waters are safe for their oyster larvae. "Oyster hatcheries here are chemically buffering their waters to reduce the corrosiveness, exploring ways to reduce other stressors on the organisms in the hatcheries, and developing breeding programs to help find strains that are more resistant to ocean acidification. However, there are always limits to adaptation, we can only engineer so much, and for shellfish species that don't have established hatcheries, meaning they are wild spawned, the possibilities are far less. Ultimately we need to remove the primary causes of ocean acidification if we value shellfish for their economic and ecological roles."

As humans throw off the delicate water chemistry that shelled seafood species, such as oysters, scallops and clams, are accustomed to, it'll become harder for them to survive because they'll struggle to build or maintain their shells.

In 2005, the National Oceanic and Atmospheric Administration began reporting that hatcheries throughout the West Coast were seeing steep declines in production, putting the $84 million industry in jeopardy. Hatchery staff and scientists scrambled to pinpoint the cause, and extensive water monitoring was carried out up and down the coast. Bacteria, pollution, and disease were all considered—and ruled out—as possible culprits. “We didn’t know what we were dealing with,” says Barton, who has a degree in oceanography. “Everything was dying. [We have] seen a lot of dead larvae, but this time the symptoms were really different.” "The pH level of the water was drastically lower (more corrosive) than usual."

The native Olympia oyster...once dominated San Francisco Bay’s ecosystem ...Due to over harvesting, loss of habitat, and pollution, oysters virtually disappeared from the Bay...Indications that oysters were returning to San Francisco Bay were seen in the late 1990s when small, scattered populations were discovered on docks near Redwood City.