New England Fisheries

Ocean Acidification Threatens Our Shellfish

Blue mussels. Image via Bays Program.

The Massachusetts legislature is current considering a number of bills regarding ocean acidification. If passed into law, the bills will establish a special commission or task force to study the effects of coastal and ocean acidification on coastal communities, fishing and aquaculture industries, and local commercially-harvested species. These bills come at a very critical time when what we do or don’t do next to address the effects of ocean acidification could very well alter the Commonwealth’s culture and economy.

What is ocean acidification?

Excess carbon dioxide in our atmosphere from the burning of fossil fuels is driving climate change and along for the ride is increased global temperatures, rising sea levels, and increased storm intensity. We hear about it almost daily. But on a planet that’s 70 percent ocean, what’s happening below the waves? They call it global warming’s evil twin: ocean acidification.

Much like the atmosphere, the ocean is absorbing more and more carbon dioxide. As a result, ocean temperatures are not only rising, but the actual chemistry of the ocean is changing. Research estimates that the ocean has become 30 percent more acidic since the Industrial Revolution. In particular, the Gulf of Maine is especially vulnerable because its colder waters can absorb more carbon dioxide than other ocean areas. Massachusetts’ bays and sounds are among those waters impacted by ocean acidification.

Why do we need to act?

Ocean acidification should be very alarming to Massachusetts and its legislators because it poses a grave threat to the Commonwealth’s shellfish fisheries – the most valuable in the Commonwealth. Increased ocean acidity interferes with the ability of shell-forming organisms such as clams, mussels, and oysters to build and maintain their calcium carbonate shells. The planktonic larval stages of many species are also vulnerable, a concern for hatcheries and wild populations of shellfish.

Investigating ocean acidification is imperative because the Massachusetts commercial fishing industry relies heavily on shellfish. In 2016, Massachusetts fishermen landed 91 million pounds of clams, crabs, scallops, and lobsters. These landings, supporting thousands of jobs, were worth a total value of $440 million – 80 percent of the total value of commercial fisheries landings in the Commonwealth. Nationally, New Bedford, MA has been consecutively ranked as the most valuable port for over a decade due to its large scallop fleet. Also, farm-raised shellfish added another $25.4 million in 2013.

Massachusetts cannot afford to lose these fisheries. But more research is needed to better understand the effects of ocean acidification and what might be possible to combat it. It’s a big task, but it’s a promising sign that the work from previous commissions in Massachusetts has led to concrete action. For example the Massachusetts Ocean Task Force led to the Massachusetts Ocean Plan – the first ocean plan in the country. Massachusetts needs to continue to be that ocean leader. The time for action on ocean acidification is now.


2 Responses to Ocean Acidification Threatens Our Shellfish

  • Ralph Johnson says:

    Nutrient Loading is a large problem in the Narragansett Bay. This can cause greater acidification near the coast than the atmospheric CO2 emissions effect on the general open Ocean Acidification. Excessive Nutrients promote acidification by fueling growth of algae & phytoplankton, which then die & decay. The CO2 released during the decay process has the same effect on pH level of the ocean as CO2 from the atmosphere. Several fish kills & dead zones have been reported in the upper bay due to hypoxia, warming sea water & excessive nutrients. New England faces elevated risk for Coastal Acidification. Coastal waters are not well buffered against OCA. Carbonic acid is generated when CO2 is added to the water. The capacity of seawater to resist the addition of this acid is termed “buffering capacity.” Seawater with reduced buffering capacity exhibits a more pronounced pH change for given input of CO2, making corrosion more likely for shells and skeletons of marine life. Buffering capacity is lowered in the Northeast primarily because of the region’s low water temperatures, which affect carbonic acid chemistry, and because of its many rivers that deliver large inputs of freshwater, carbon, and nutrients. Plumes of water at the river mouths become overly acidic as shells & skeletons begin to dissolve. OCA coincides with hypoxia (low oxygen levels) through bacterial draw-down of the bottom oxygen. Stratification over water column prevents mixing for new CO2-rich bottom water. Creating inhabitable areas for marine species. What can you do? ‘Experts recommend people take the following steps to reduce acidification of their local coastal waters’: cut down or eliminate fertilizers on lawns, gardens, and farms, reduces nutrients that are carried by streams & rivers into the ocean. Transport of sediment carrying nutrients & other pollutants downstream during extreme storms also needs to be monitored & mitigated.

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