May 14, 2015

Finding the local perspective on ocean acidification

Ocean acidification is not just a buzzword for the men and women who make their living harvesting shellfish off the coast of New England. The pH of coastal water directly affects the health of shellfish and that has a real and immediate impact on the livelihood of fishermen.

The Northeast Coastal Acidification Network (NECAN) coordinated an Ocean Acidification Stakeholder Workshop. The workshop brought together scientists, state and federal regulators, non-profit groups, and leaders in fishing communities across Cape Cod and the Islands to learn from one another about the local effects of coastal acidification. Held in Barnstable, Mass., this was the second in a series of workshops across New England. You can read meeting outcomes from the first workshop, held in Walpole, Maine. Further workshops are planned for Rhode Island, Connecticut, and the north shore of Massachusetts.

Sea Grant programs have been involved in these workshops from the beginning, allowing NECAN to leverage their local connections with stakeholders. This is an ongoing partnership, Maine Sea Grant Extension Educator Esperanza Stancioff helped plan the first workshop and MIT Sea Grant Coastal Ecologist Juliet Simpson and Woods Hole Sea Grant/Cape Cod Cooperative Extension Agent Diane Murphy were on the planning committee for the Cape Cod workshop. Stakeholder workshops like this help clarify existing needs and give researchers context to prioritize new research areas.

Ocean acidification is defined as a decrease in global ocean pH caused by the increase in atmospheric carbon dioxide (CO2), but isn’t the only acidification issue coastal fisherman face. Localized high acidity events have an immediate impact on the health and survival of marine life along the coast. The effects of global ocean acidification must be considered in the context of local environmental stressors that are occurring right now.

In the open ocean, the trend of increasing acidity caused by increasing atmospheric CO2 has been well documented; coastal acidification, however, isn’t as easy to measure, or define. Along the coast natural processes change quickly; freshwater inputs from land run off, tides, strong winds, and currents are among the many factors affect the acidity of the water.

Increased nutrients in runoff directly related to coastal populations is still a major water quality concern for Cape Cod and the Islands. The algal blooms that result from the increased nutrients eventually decompose, coating once sandy bottoms in thick black muck. Not only does the change in bottom type affect the settling of shellfish larvae, but as that muck decomposes it produces CO2 and that CO2 is taken up by the surrounding water causing the water to become more acidic. Scientists often talk of a global ocean pH shift from 8.2 in preindustrial times to its current 8.1, and even though this represents a 30% increase in ocean acidity, it might not sound like much to someone who runs a hatchery on the Cape. Managers routinely experience a pH of 7.5 or lower in waters off Cape Cod. If instead, researchers focus their discussions on how global acidification will increase the frequency and length of drops in local pH, the consequences of ocean acidification become more relevant for local aquaculture operations.

The wild caught shellfish industry is, and always has been, unpredictable. That is even more apparent today where aquaculturists are dealing with significant ongoing water quality issues. Hatcheries provide a critical level of control, because, without healthy seed, there is no harvest. Hatchery owners are able to monitor water quality daily, including pH, and have been adjusting these water parameters as needed for generations. Different management techniques, such as only taking in water during high tides or taking water from the top of the water column, have allowed them to keep the pH in a healthy range for larval shellfish. Access to a hatchery on the Cape is especially important when we consider the long-term impacts of ocean and coastal acidification because local hatcheries aren’t just more economical for fishermen in the area; hatcheries provide seed that is acclimated to local conditions, and therefore has a higher likelihood of survival.

Local coastal acidification must be considered when we discuss the effects of global ocean acidification. Fishermen and aquaculturists from Cape Cod and the Islands are seeing real impacts from decreasing water quality in our bays and estuaries. To what extent ocean acidification is currently making these issues worse, we don’t yet know. And while large-scale CO2 emissions may be beyond your control, helping to improve coastal water quality is something you can do. The water quality of New England’s bays and estuaries is a community issue that can be improved through hard work by local people.


For more information about ocean and coastal acidification, or about the stakeholder workshops, please visit the NECAN website: http://www.neracoos.org/necan or contact Cassie Stymiest, cassie@neracoos.org.

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Woods Hole Sea Grant/Cape Cod Cooperative Extension agent Joshua Reitsma demonstrates shell thickness of a quahog harvested in a degraded habitat.

Credit: MIT Sea Grant
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