Ocean Acidification

A Global Issue Gets Local

by Catherine Schmitt

The changing chemistry of the ocean threatens the state’s most important fisheries. Yet ocean acidification seems diffuse and global, too overwhelming for any one person, or fisherman, to do much about. But, in fact, there’s a lot of things people in Maine can do to address the problem, according to participants in a workshop hosted by the Northeast Coastal Acidification Network at the Darling Marine Center in December.

Much of the carbon dioxide that gets emitted to the atmosphere ends up in the ocean, where it is transformed in a series of chemical reactions that cause an increase in acidity. These same reactions use up carbonate, a substance that clams, mussels, oysters, scallops, crabs, and lobsters need to build their shells. Acidic water also causes problems for fish and other marine animals.

Scientists have documented that the ocean is now thirty percent more acidic than just a century ago. The effects on life in the ocean are still largely unknown, although laboratory studies suggest thinning and weakening shells in everything from algae and zooplankton to mollusks and crustaceans. Are people in Maine seeing anything like this? What are they concerned about? What should be done about the acidifying sea?

Getting answers to these questions was the goal of the workshop, attended by people who make their living harvesting and growing shellfish, people who eat shellfish, and members of watershed and stream groups who monitor pollution in waters where shellfish lives and grows.

In the last 50 years, more carbon dioxide has been added to the atmosphere and at a faster rate than at any time in the last 35 million years, according to a presentation by Mark Green, a shellfish grower and professor at St. Joseph’s College who has studied the effects of acidic water and mud on soft-shell and hard clams.

Reducing carbon dioxide emissions will slow ocean acidification, said Green. “According to Henry’s Law, the concentration of a gas in solution is in proportion to its partial pressure in the atmosphere. There’s not a lot of gray area here.”

Acid doesn’t just dilute throughout the entire ocean, but stays in the surface “mixed” layer, which takes hundreds of years to mix with the deep ocean. So it’s not going away anytime soon.

Green pointed out that ocean acidification is not something scientists are predicting for the future. It’s happening now.

Bill Mook agreed. He has operated an oyster hatchery and sea farm on the Damariscotta River for more than three decades. “On the West Coast, the oyster industry experienced a massive failure of both wild and hatchery oyster sets that was later linked to acidity,” said Mook, who also presented at the workshop. “A few years later, we started having similar problems.” Oyster larvae stopped or slowed their feeding, taking another week to grow—a delay that according to Mook equates to a production loss of $100,000. After much time, money, and effort, he identified that the pH of the water pumped into the hatchery from the river had changed, and developed a suite of management and mitigation tactics to adjust the carbonate chemistry. Last year he had the first 100 percent successful spawning and larval survival, evidence that he had correctly identified that acid-driven declines in carbonate were affecting oyster growth.

“Through observation, trial, and error, we reached the same conclusion made by controlled, replicated experimentation. But this doesn’t really equate to what’s happening in the wild,” he said. As to what’s going on out there, in Maine’s rivers and bays, “We are really clueless.”

Other laboratories and culture facilities, including the UMaine Center for Cooperative Aquaculture Research, are concerned about effects on finfish. Because hatcheries focus on the sensitive early stages of marine organisms and pay close attention to daily, even hourly conditions, they could act as early warning signals of potential problems for commercial shellfish beds.

The Gulf of Maine is susceptible to acidification for several reasons. The Gulf is relatively cold, and colder water is more acidic. Unlike other coastal areas such as the Gulf of Mexico, the Gulf of Maine doesn’t have much capacity to “buffer” against acid increases. The numerous large rivers bring in a lot of fresh water, and fresh water gets more acidic than salt water. And the volume of runoff has been increasing, sending even more fresh water into the coastal ocean as well as nutrients, which contribute to the production of algae, which creates more acid when it decomposes.

Bill Mook noticed a correlation between problems at his hatchery and storm events and increased flows in the Damariscotta River. “When I started my business, I would always say the salinity was 30 parts per thousand,” said Mook. “Now it rarely, if ever, gets there.”

Lower salinity, warmer temperatures, and increased acidity combined create a toxic environment in clam flats already devastated by green crabs. “A clam has twenty-four hours to decide whether or not to settle in mud,” said Green. If the mud is undersaturated with carbonate minerals like aragonite because of acidity, the clam will reject it. “This isn’t just about clams. Low pH stresses fish, too, by affecting their ability to consume oxygen,” said Green, who noted that seaweeds—plants—actually do better in a high-carbon-dioxide environment.

Mook wonders about the implications of fresher water, which is more prone to acidification, for mussels and lobsters, which represent 87 percent of the value of Maine seafood landings.

“We’re scared,” lobsterman and Maine Lobstermen’s Association President Dave Cousens told the gathering. It’s unclear to what degree, if any, acidity is affecting Maine lobster since so many changes are taking place at once. Lobsters are moving around in different patterns. Shell disease is lurking to the south. Strange creatures and unfamiliar fish are showing up on boat rails, in lobster traps, and at the ends of fishing lines.

Warming water is having an effect, however. The early shed and subsequent market-crashing glut of lobsters in 2012 “wasn’t just a blip,” said Cousens. There’s been an explosion of lobsters twenty to forty miles offshore, and the landings have shifted north. Cousens attributes recent increased landings to warm, sixty-degree water that enhances larval lobster survival. “Right now we’re in the sweet spot. But every year it moves north,” he said. Fishing has also become unpredictable. Old timers could count on the osprey arriving in April, and the herring would follow. Now, everything is haywire, said Cousens. “If our kids can’t make a living lobstering in the future, we need to know that now.”

Ru Morrison of the Northeastern Regional Association of Coastal Ocean Observing Systems (NERACOOS) coordinates the Northeast Coastal Acidification Network. A buoy in southern Maine off the Isle of Shoals is the only location where acid parameters are being continuously measured, although a new shore-based system was installed in Casco Bay in 2014. And Maine has a lot of marine research institutions that could conduct monitoring and experiments, efforts which might be boosted by a potential $2.5 million increase in the budget for NOAA’s Ocean Acidification Program, depending on how Congress votes on the appropriations bill. Workshop participants expressed a need to know more about estuary zones, since fresh water seems to be an important factor.

Mook, Cousens, and several others at the workshop are members of Maine’s Commission to Study the Effects of Coastal and Ocean Acidification; they expected to submit their report to the Legislature at the end of December. Among their recommendations are to reduce runoff of fresh water and nutrients by strengthening and augmenting existing pollution control efforts.

The additional factors that influence acidification in the Gulf of Maine complicate the situation, but they also mean that there are things people can do on land to prevent the situation from getting worse: keeping water clean, retaining stormwater, fixing broken infrastructure, etc.—actions that many of the water monitoring groups at the workshop have been advocating for years. Others suggested adding kelp aquaculture upstream of shellfish farms to “soak up” carbon dioxide.

Bill Mook said that one of the points made in the Ocean Acidification Commission’s draft report is that identifying and developing new technologies that have global marketability and which would have the added benefit of creating economic opportunities here might be the best way for Maine to contribute to reducing greenhouse gases and slowing acidification.

“We are off to a great start with Maine leading the way,” said Esperanza Stancioff of Maine Sea Grant and University of Maine Cooperative Extension, who helped organize the workshop. More meetings are planned in the Northeast region to gather input from others working on the water, leading to an implementation plan.

The discussion of tangible actions seemed to energize workshop participants. As one lobsterman noted, the things we can do for ocean acidification are things we can bring to our homes, houses, rivers, lives. “Don’t worry about what’s going on in Cashes Ledge, but worry about what you and your neighbors are doing in your hometown.”

Ocean acidification involves complicated chemistry and its causes are distributed throughout the globe. But some solutions are actually quite simple, and fishermen may well take the lead.

For more information, visit http://www.neracoos.org/necan.