Concerns about invasive species, right whales and fisheries were among the questions BDN readers had on climate change. Credit: Natalie Williams | BDN

In recent decades, the Gulf of Maine overall has been warming faster than 99.9 percent of the world’s oceans. The gulf’s average daily surface temperature hit a record high last month, while over the past 15 years its deeper waters have been warming twice as fast, according to scientists.

But even without a thermometer, the gulf’s changing climate has been apparent to fishermen and others who keep tabs on its marine life. Lobster harvests in the gulf have soared over the past three decades, though there has been a downturn in catch volume in the past three years, and lobsters also have shifted farther east, where temperatures are lower than those off the southern Maine coast. Other commercially harvested species, however, have seen their numbers sharply decline.

To share information about the effect warming temperatures in the Gulf of Maine are having on Maine communities and ecosystems, the Bangor Daily News hosted an online event on Sept. 17, bringing together four experts to share their work on the topic. The webinar was the second of four BDN Climate Conversations, which will help shape our coverage of climate issues.

The conversations bring together scientists from the University of Maine and other research institutions as well as other local subject matter experts.

During last week’s event, to which more than 150 people tuned in, people posed questions about the gulf’s rising temperatures to the panelists. Here are some of their biggest questions.

Paloma Henriques, Orono: Do you think seaweed farming could help offset warming and/or acidification to some extent locally if done on a large enough scale?

A 2017 study by Bigelow Laboratory for Marine Sciences in Boothbay found that seaweed harvesting can help to reduce carbon levels and acidification in the surrounding water column, though other observers have raised concerns about the effect such harvests might have on juvenile creatures that inhabit the shallow waters where seaweed is removed.

When it comes to carbon levels, seaweed is known to absorb carbon when it grows and then to release it back into the ocean when individual seaweed plants die and decompose. By cutting healthy seaweeds and then having stalks regrow, the carbon absorbed by the harvested seaweed is removed from the ocean, helping to mitigate acidification, the study suggested.

Cipperly Good, Searsport: Besides northern shrimp, what other species are at risk of their range moving north out of the Gulf of Maine?

One of the reasons scientists think the gulf’s lobster population began to rise steeply in the 1990s is because that is when the gulf’s cod population plummeted, primarily due to overfishing. Hopes of restoring the gulf’s cod numbers have been derailed due to climate change, which has pushed cod’s habitat further north. Other groundfish species such as hake and flounder also have had their populations decline sharply since the 1990s, as have urchins and mussels, though warming water may be only one of several reasons for these declines.

Michael San Filippo, Lynbrook, New York: What about invasive species which are increasing in number, such as Asian shore crabs and green crabs? Can the industry pivot and find value in these and other similar species as the Gulf of Maine continues to warm?

Invasive crab species are known to prey upon Maine shellfish such as softshell clams, and could be one reason why clam harvest volumes have declined since the 1970s. University of Maine researchers have been experimenting with food products that can be made with green crabs.

There already is market demand for other more southerly species that are being seen more frequently in Maine, such as black sea bass and squid, but the difficulty in harvesting those species is getting federal permission to do so. States often have their own catch limits for certain species, which add up to overall national catch limits. For Maine to be given part of a species’ overall national catch limit, other states would face having their catch quotas for that species reduced, which is expected to be an uphill political battle.

Alan Brooks, Lubec: How is ocean acidification likely to affect future growth of the shellfish farming industry?

Oyster farmer Bill Mook has said that in 2009, a warm winter boosted the gulf’s acidity levels, making it very difficult for him to grow oyster spat to an adolescent stage. He now treats oyster spat in their nursery to counteract the effects of acidification, he said.

One possible way to address the problem, scientists and shellfish growers say, is to pair up seaweed and shellfish aquaculture operations, so that the growing seaweed can help absorb carbon in the water, and improve conditions for nearby shellfish growing sites.

Paul Weeks, Bangor: What effect does warming in the Gulf of Maine have on right whale feeding, mating, traveling through the gulf. Where are these whales feeding and breeding now?

There has been an increase in seasonal right whale activity in the Gulf of St. Lawrence in Canada, north and east of New Brunswick and Nova Scotia, likely because the main type of copepod that the whales eat, calanus finmarchicus, has moved north to get away from warmer temperatures in the Gulf of Maine and the Bay of Fundy.

Right whales have been observed wintering in the Gulf of Maine and are known to congregate in Cape Cod Bay in winter and spring, with females heading south off the coasts of Georgia and Florida to give birth. Whale researchers are trying to learn more about places where groups of right whales might gather at other times of the year.

The next Bangor Daily News Climate Conversations webinar, scheduled for 4 p.m. on Oct. 15, is “Snow Business: What do shorter, milder winters mean for the outdoor industry?” Click here to register.

Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....