The Gulf of Maine is growing warmer. From 1982 to 2013, the Gulf warmed by an average of 0.05 degrees F per decade. The rate of that increase in temperature took an upturn in 2004. The Gulf is now warming by an average of 0.04 degrees F per year, according to data from the Gulf of Maine Research Institute in Portland. The consequences of a warmer Gulf of Maine are many, ranging from the introduction of new marine species to alterations in the chemistry of the ocean itself.
During the next several months, Landings will explore some of the changes that Maine fishermen are experiencing due to changes in the Gulf’s environment and look at what may face them in the near future.
We all have our “home turf.” It’s the place that we know the best, whether it’s a congested urban neighborhood or a sparsely populated stretch of the Maine coast. It’s the place where we know exactly what’s normal and what’s not: what trees and plants are to be found, what creatures live in the woods or under the nearby dumpster, who starts his boat engine each day at 4:45 a.m. or who loiters around the street corner at late hours.
Our oceanic home turf, the Gulf of Maine, is the region where cold water masses from the Arctic and warm water masses from the Gulf Stream intersect. Marine species from the boreal zone (subarctic climate between 50° to 70°N latitude) and the temperate zone (between 35° and 50°N latitude) can both flourish in the Gulf, as long as things stay the same.
But the Gulf of Maine is warming, and warming quickly. The change has come about because of the gradual warming of the world’s oceans as air temperatures and greenhouse gas concentrations rise. The Gulf is also feeling the effects of ice melting in Greenland and the Arctic Ocean and the northerly meanderings of the Gulf Stream, which brings warm water into the region.
Back in 1605 English explorer George Waymouth made his way to Monhegan Island where he and his crew remarked on the huge fish they caught from vast schools of haddock and cod. For centuries the Gulf of Maine has been renowned for its high biological productivity, a result of strong tides, currents and cold, oxygen-rich water. Seasonal blooms of phytoplankton undergird the robust populations of groundfish which have made the Gulf a lucrative fishing region for many centuries.
With warmer water, however, long-term residents of the Gulf, such as cod, are making their way north to avoid the warmer temperatures. Other migrants from more temperate waters are making the Gulf their new home turf.
Research by scientists at Rutgers University predict that marine habitat suitable for Atlantic cod could shrink by as much as 90% by the end of this century. The researchers used data from more than 130,000 bottom trawls and 16 different climate models to estimate the current and future distribution of 686 fish and invertebrate species along the Atlantic and Pacific coasts. In addition to cod leaving the Gulf of Maine, lobsters could also find their present home too hot for comfort. The study predicted that Gulf lobsters could shift 200 miles to the north into Canadian waters. Sea scallops could also shift more than 430 miles northward, putting a dent in Maine’s lucrative fishery.
“It’s quite striking how fast the Gulf of Maine is warming and is projected to warm in the future, so we do expect large impacts on the Gulf of Maine,” said Malin Pinsky, an associate professor at Rutgers University’s Department of Ecology, Evolution and Natural Resources and one of the lead authors of the study at the time of the article’s release. “Some species are moving out, but other species are moving in.”
One of the species that seems to be moving out is a tiny copepod called Calanus finmarchicus. C. finmarchicus is the bread-and-butter staple of the Gulf of Maine. Whales eat it, juvenile fish eat it, tiny lobsters eat it, and then dozens of other species eat those creatures. They do so because the tiny zooplankton are lipid-rich, meaning they are full of fat.
But in the Gulf of Maine C. finmarchicus is at the southern extent of its range. Warm the water and the copepod will seek cooler areas. Scientists also have found those C. finmarchicus that don’t migrate out of the Gulf are losing weight. These copepods go into a long period of dormancy during the winter months, called diapause, when they sink down into deep water. It’s during that time that they build fat reserves. They wake in the spring and rise to the surface. Researchers have found that a shorter diapause period results in reduced fats in the copepod. That’s important because C. finmarchicus is a critical food source for visiting North Atlantic right whales, among other creatures. Thinner C. finmarchicus means fewer calories for these endangered whales.
Another species affected by a warmer Gulf of Maine is kelp. The macroalgae, which is at the southern end of its range, reacts sharply to warm water temperatures. If the ocean temperature reaches into the 60os, the fronds and leaves of kelp fall apart. Above 68o, the algae dies.
A study by University of New Hampshire researchers, published in November 2019, revealed that warming water off of southern Maine and the Isles of Shoals in New Hampshire has reduced the growing season for kelp. The number of days of 60o or greater water grew more than forty-fold since the 1980s. Into that seascape have come other algae, loosely termed turf algae, which have a much broader temperature range. The influx of short, stubbier algae in places that once hosted dense kelp forests has changed which species use the area. Kelp offer sanctuary for juvenile and adults of species such as lobster and cunner. What the loss of kelp means in the long term is unclear, but, as lead author Jennifer Dijkstra stated, “Our study indicates that in cases of foundational induced transformation of seascape patterns, these changes will likely propagate up the food web, specifically affecting those species that are residential and seek refuge and food within the seascape.”
Along the northern and eastern edges of the Gulf of Maine, kelp is seeing a resurgence. Doug Rasher, a scientist at the Bigelow Laboratory in East Boothbay, is conducting a detailed survey of kelp forests on the Maine coast. In Downeast Maine, where the water temperatures remain cool, he has found that kelp forests may actually be returning, although the actual kelp species are likely different than those that historically thrived in the region. The return of kelp forests in this case may be due to the lack of animals that eat kelp, namely sea urchins.
A warming Gulf is also providing new opportunities for species formerly absent from the region.
Marine heat waves have become common in the Gulf of Maine. A marine heatwave is a period when water temperature is above the 90th percentile (of average temperatures) for more than five days. In 2018, the Gulf of Maine spent more than 180 days above the 90th percentile.
Six years earlier, in 2012, the Gulf of Maine warmed up earlier than ever before in recent memory. As a result, longfin squid moved north into the Gulf’s coastal waters in great numbers, prompting fishermen to rig for squid throughout the region. During that year Maine lobstermen found southern triggerfish in their traps, and scientists reportedly even spotted tropical species like filefish and snowy grouper in Maine waters.
Black sea bass, a reef fish common from the Gulf of Mexico to Cape Cod, are now regularly caught in the Gulf of Maine. In 2014 Maine set recreational regulations for harvest of the fish and proposed a commercial quota of 10,850 pounds, illustrating the growing importance of the species within state waters.
Invasive green crabs in the Gulf of Maine are one species that has blossomed as a result of warming waters. While entrepreneurs are trying different ways to extract some commercial value from the aggressive crabs, those involved in the soft-shell clam fishery see them only as a dangerous pest. The green crabs, among other stressors, have had a dire effect on the state’s clam beds: commercial landings were a little over 7 million pounds, the lowest in decades, in 2018.
But other shellfish species, better adapted to warmer waters and with tougher shells, may find the Gulf a welcome home. Manomet, a non-profit Massachusetts environmental organization, is working with four shellfish aquaculture operations in Harpswell, Georgetown and West Bath to test out growing quahogs and finding markets for the shellfish. Quahogs, which are typically harvested in the warmer waters of Rhode Island and Massachusetts, can be found naturally in the New Meadows River area of West Bath. The aquacultured quahogs are grown in bags located in 10 to 30 feet of water to keep them safe from the green crabs, which will prey on juvenile shellfish when the young settle in mud.
It can be unsettling to find that one’s home turf is no longer the place one remembers. The temperature is different, the makeup of plants and animals is changing, even the timing of the seasons has altered. Maine fishermen, however, are nothing if not resilient. As former fishing opportunities begin to wane, fishermen are ready to make the most of the new opportunities that are coming their way in the Gulf of Maine.