Ocean acidification spells trouble for shellfish industry

Photo by R. Rheault

Photo by R. Rheault

If mollusks, particularly the shelled and delicious variety, can feel emotions, then they must be getting nervous. Not of happy hour regulars eyeing the one-dollar oysters, mind you, but of the creeping acidity in the oceans. According to a new study, clams, mussels, oysters and their brethren shouldn’t be the only ones feeling anxious, because ocean acidification is a threat looming over the lucrative US shellfish industry.

Shellfish are essential to keeping coastal waters healthy; in fact, they’re tireless little workhorses. For example, just one oyster can filter and clean up to 50 gallons of water per day. Not only are shellfish good for the health of coastal waters, farmed shellfish are part of a growing, and sustainable, industry. According to the NRDC, which participated in the recent shellfish study, the “shelled mollusk” (clams, oysters, mussels, scallops) industry in the US, both farmed and wild-caught, is worth about $1 billion. That’s a rare feel-good story for the nation’s fishing industry.  Unfortunately, it means that acidification threatens not just mollusks trying to make their shells, but people trying to keep their jobs.

The new study provides a unique economic look at the impacts of ocean acidification, and the view is startling. According to the findings, 15 states are at “high risk of economic harm” because of the effect acidification could have on their shelled mollusk fisheries. In some cases that harm is already a reality, such as in the Pacific Northwest where ocean acidification has cost the oyster industry nearly $110 million, jeopardizing 3,200 jobs. The effects of ocean acidification are being amplified by other local issues, creating what the NRDC calls “hot zones,” or areas with a strong shellfish industry that face multiple environmental, social and economic risks from acidification. As NRDC describes them:

  • New England hot zones: The productive ports of Downeast Maine and southern Massachusetts where poorly buffered rivers run into the cold New England waters which are especially enriched in ‘acidifying’ carbon dioxide.
  • Mid-Atlantic hot zones: East coast estuaries like Narragansett Bay, Chesapeake Bay and the Long Island Sound where an abundance of nitrogen pollution exacerbates ocean acidification in shellfish-rich areas.
  • Gulf of Mexico hot zones: Terrebonne and Plaquemines Parishes of Louisiana – and other communities in the Gulf of Mexico – where the shelled mollusk industry is limited to oysters, giving this region fewer options for alternative, potentially more resilient, mollusk fisheries, in the short term.
  • Pacific Northwest hot zones: The Oregon and Washington coasts and estuaries where a potent combination of risk factors converge, including cold waters, upwelling currents that brings corrosive waters closer to the surface, corrosive rivers, and nutrient pollution from land runoff.

Why is the ocean becoming more acidic? Because too much carbon dioxide is being released into the atmosphere from power plants, cars and factories. The world’s oceans and the atmosphere exchange huge amounts of carbon dioxide each year, but since the industrial revolution the amount of CO2 in the atmosphere has risen 40 percent. When this increased amount of CO2 enters the ocean, a series of chemical reactions causes the water to become more acidic, resulting in a 30 percent increase in ocean acidity since the mid-19th Century. This makes it difficult for creatures that create exoskeletons out of calcium carbonate, like clams and oysters.

The study is yet another example of how our food, water and energy choices are closely connected. In this case, a healthy and sustainable source of seafood is being threatened by the effects of our fossil-fueled energy on the world’s oceans. It’s a remarkably similar situation to the connection between coal power plant emissions and mercury concentrations in seafood.

Whether or not there are shellfish available for dinner in the future, not to mention whether or not people can still make a living from harvesting shellfish, depends a great deal on how we choose to power our future. Just think: if we were to combine efforts to reduce fossil fuel emissions with other local solutions – like cutting back on polluted agricultural runoff and investing in diverse shellfish farming – then the only reason to mention acidity in the same breath with shellfish would be to complain about too much lemon.

Peter Hanlon, GRACE Communications Foundation, 30 March 2015. Article.

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