Ocean Acidification Threatens Bivalve Industry

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COURT HOUSE - Worldwide, ocean levels are rising at an accelerated pace. Cape May County is feeling the effects of exacerbated weather events, as a result. 

Yet, there is another drastic change affecting the oceans - a decrease in the water’s pH levels. This is a change that industry leaders and scientists fear will drastically affect the county, namely its bivalve (aquatic invertebrates with a hinged shell) industry that is, as marine and coastal sustainability expert Dr. Daphne Munroe said, “At the heart of the economy in this region.” 

As carbon is released into the atmosphere, it was once speculated that the ocean’s tendency to absorb emissions would be a net positive, as it spared the Earth’s atmosphere from the worst of the emissions. Dr. Feely, senior scientist at National Oceanic and Atmospheric Administration (NOAA), said, "[It's] a huge service the oceans are doing that significantly reduces global temperature."

However, scientists are coming to realize that the ocean’s absorption of carbon emissions comes at a great cost, and that the long-term effects of an ocean that has absorbed great amounts of carbon emissions mean that ecosystems will ultimately suffer. 

“Ocean acidification will disproportionately affect bivalves. The data is still coming in on this stuff, but we anticipate that because of the way that bivalves make their larval shell when they're babies, floating around as zooplankton, they are among the most vulnerable species when it comes to ocean acidification,” said Munroe. 

She continued to explain that the bivalve industry, on the West Coast, is feeling the adverse effects of ocean acidification, but that, so far, the Atlantic Ocean has been spared from the worst of it. 

She said that “on the West Coast, they’ve had big problems in their hatcheries with acidified water to the point where they have to buffer the water to successfully produce feed oysters.”

How is Shellfish Chemically Impacted? 

When bivalves are larvae, they rely on carbonate ions for the formation of their shells. The weakened state of shellfish caused by acidification has been compared to osteoporosis in humans. Their shells do not form properly, and they grow up with a brittle protective layer. 

According to the National Marine Fisheries Service, when carbon dioxide is absorbed into seawater, a weak carbonic acid is formed that releases hydrogen ions into the water. These hydrogen ions combine with carbonate, the essential ingredient in shell formation, to form bicarbonate.  

When carbonate is used in the process, it is not as readily available for shellfish to use in the formation of their shells. This increase in hydrogen increases the ocean’s acidification and will continue to do so, as carbon dioxide is released as a pollutant. 

Shellfish, when they don't have sufficient carbonate, form weak, brittle shells that provide less protection from the ocean’s prey and conditions.

Munroe outlined the ways these creatures are cornerstone species in the county and beyond: “The species we’re talking about, when they’re small, are important food resources for other species. The other thing is that, in terms of what we call ‘ecosystem services,’ they’re filter feeders and, in the case of oysters, they also produce ecosystems, like reefs, because the shells themselves become part of the habitat. They’re not only important economically and as a food resource for humans, they’re also really important ecologically.”

The change will not happen overnight. The timetable of the acidification, although it has begun, will take place over decades. 

NOAA and Intergovernmental Panel on Climate Change (IPCC) reported several times, including in a 2014 IPCC report and many graphs and data points on NOAA's website, that the accelerated pace of climate change is a result of carbon emissions.

There is concern among scientists that ecosystems, and the animals within them, won't have sufficient time to adapt to the rapid changes. 

Dr. Munroe said there is great uncertainty surrounding the bivalve’s ability to adapt. Adaptation and evolution is a slow process, one that scientists fear will not match the speed at which ocean waters are changing.

“The question is: can these shellfish … is there capacity for adaptation? That’s something that we don’t know very well. There’s been some nice work to tease some of that out, but it’s difficult to do those experiments. I think there’s a lot to be thought about in terms of the uncertainty we have coming out of the labs. This is still a valid and important thing to keep in mind.”

Why Changes are Happening? 

Brian Harmon, general manager at Cape May Salt Oyster Farms, and oyster farm manager at Atlantic Cape Fisheries, also worries about the future of the bivalve industry. Beyond ocean acidification, he spoke about the ways that the changing climate has impacted the shellfish industry in Cape May County. 

“Climate change, as a whole, definitely has us thinking, and it’s for everybody, everybody living on the planet and their livelihood. For us, as an industry, we have seen relatively predictable weather go out the door. 

"We really don’t know what to expect going season to season. We have had unpredictable winters. We have had no ice. We have had terrible ice. We are at the mercy of Mother Nature, so any kind of increase in storm intensity is bad for us. 

"Just talking to old-timers, people who have been around the bay forever, for 60-80 years, say they never have seen 70-degree days in the winter before."

“What we want, as shellfish farmers, when we go into the winter, we want it to cool off and stay cool all winter until it’s spring, just as a gradual warmup,” Harmon added. "We want a nice, gentle, in and out of winter. 

"What we saw last winter was kind of scary... We had several days in January and February where it warmed up to near 70 degrees, and that’s enough… to wake the oysters out of hibernation. 

"If they do wake up, and it’s the wrong time of year, where they’re not supposed to be metabolically active, there’s not enough food in the water in the form of microalgae. They wake up and try to feed. They starve themselves that way.” 

Munroe explained that “the ocean acidification problem is a [carbon dioxide] problem, so it's emissions, and that’s the bottom line. Things like finding ways to reduce carbon emissions are the way. However that looks locally and beyond, that’s the answer.” 

Harmon echoed that sentiment, and worries for the future of the East Coast shellfish industry. “One hundred percent we need to do what we can to try and get our planet back on track," he said. "This is just one problem of a whole slew of problems that are caused by burning too much fossil fuel… I’m sure we will start to see hatchery failures on the East Coast… but we haven’t had any issues sorting seed, so it isn’t a problem yet so much over here.” 

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