Shellfish dying, lobster leaving: Mass. marine ecosystem faces hotter, harsher future as climate warms – The Boston Globe

The Boston Research Advisory Group report found that deadly hot marine heat waves — once extremely rare — could become commonplace. Scientists warn that those and other impacts are only going to get worse if the climate continues to warm with dire and possibly irreversible impacts on the ocean.

If the planet does not stop emitting planet-warming greenhouse gasses, marine heat waves could occur off the coast of Massachusetts once every decade if the planet reaches 2 degrees Celsius of warming and perhaps every other year with 3 degrees of warming. The vast majority of excess heat generated by anthropogenic warming is absorbed by the planet’s oceans.

“The possible impacts described in this report are not pleasant,” said Paul Kirshen, a professor of climate adaptation at the University of Massachusetts Boston and an author of the report. “We need to get to net zero emissions and below as soon as possible.”

Unlike on land, where humans can build a seawall to protect from coastal flooding, for example, there is very little that can be done to help ecosystems adapt to warmer water and higher acidity, experts said. The trends noted in the report will be “very difficult” to respond to, Kirshen said.

The report was created to answer questions posed by leaders of coastal Massachusetts towns and cities about what communities could expect over the next few decades as the climate continues to warm. Many of those towns have local economies that are at least in part dependent on commercial fishing, an industry that is likely to be dramatically changed by a warmer and more acidic Massachusetts Bay.

Native fish populations will likely continue their decline off of Massachusetts’ coast, while species from further south will move in, scientists found. The bay will continue to get acidic and inhospitable for the many fish, plants, and shellfish that live there now.

Oceans absorb about 30 percent of the carbon dioxide that’s released into the atmosphere. When absorbed, carbon dioxide makes sea water more acidic through chemical reactions, putting the entire food web in the marine ecosystem at risk, according to the National Oceanic and Atmospheric Administration.

One example: Higher acidity causes shells to deteriorate, which kills shellfish. That will be an early marker of a shift in fishing ecology in Massachusetts Bay, the Boston-area researchers warned.

“Shell fisheries should be monitored … for warning signs,” the report said. As acidity increases, there are fewer carbonate ions in the water, an essential ingredient to build shells.

Meanwhile, the Atlantic Cod’s numbers have already declined and the American lobster population is moving north. Scientists further expect populations of winter flounder, silver hake, and Atlantic herring to decline as well.

As others move out, species more suited to warmer temperatures are expected to move in, such as summer flounder, black sea bass, blue crab, and butterfish among them.

Jason Krumholz, an oceanographer and associate professor at the University of Connecticut, said that when he started graduate school in 2005, only very rarely did he catch blue crabs in nets. Now, more than half the crabs he catches are blue crabs, he said.

“I’m not that old yet, and this is a change that I’ve seen just in my career,” said Krumholz, one of the authors of the report. “It’s pretty fast.”

The fishing industry could likely adapt to this change by convincing buyers to push different offerings on the menu, Krumholz said. “We may have a lot more flags outside of restaurants with blue crabs on them instead of lobsters in 20 years.”

Scientists have also observed that the Atlantic Meridional Overturning Circulation is slowing down. It’s one of the planet’s most prominent and powerful ocean currents and helps to moderate the climate at sea and on land near the shore.

That’s a wild card for ocean temperatures, said Bruce Anderson, an oceanographer and professor at Boston University and one of the lead authors of the report. The phenomenon could weaken and broaden the Gulf Stream, which brings warm tropical waters to the region.

“It’s really unclear what the Gulf Stream is going to do and how that change is going to affect things like the fisheries or even our climate here in Massachusetts,” Anderson said.

If the Gulf Stream slowdown continues, the water offshore of Massachusetts could see “substantial” warming as subtropical waters diffuse northward into the region, scientists found, further compounding the problems.

Another area of uncertainty: How President-elect Donald Trump’s administration could impact the trajectory of offshore ecosystems.

Environmental advocates are worried that the incoming Trump administration will try to slash budgets for federal environmental agencies, which could both slow the energy transition from fossil fuels to clean energy and affect efforts to clean up marine pollution.

Many federal grants finance beach cleanups, water quality testing, and other programs to manage the marine environment, said Jeff Watters, vice president of external affairs of the Ocean Conservancy, a nonprofit organization.

“I think they’re more at risk now than they were under the first [Trump] administration,” Watters said, because Congress was able to block some of those defunding efforts last time. “Pollution could absolutely go up; that’s a real possibility.”

Those fears come as marshes and coastal ecosystems are already threatened by plastic and pharmaceutical pollution, and runoff pollution is expected to increase due to stronger storms and an increase in coastal populations, according to the new report.

The pollution in Massachusetts Bay is affected by the behavior of people: What they buy, where they fish, how they recreate, and where they live, said Anderson of Boston University.

Yet, perhaps in that relationship lies a glimmer of hope: Towns, cities, and individuals can prevent further pollutants from entering the ecosystem. “This is a very sensitive environment to everyday decisions,” Anderson said.

Erin Douglas can be reached at erin.douglas@globe.com. Follow her @erinmdouglas23.