A Big Climate Warning from One of the Gulf of Maine’s Smallest Marine Creatures
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For all the escalating climate-related threats to iconic and commercially valuable marine life in the Gulf of Maine, though, scientists say there is one creature we should especially keep our eye on—a barely visible creature that helps those whales, puffins and cod survive: the zooplankton Calanus finmarchicus.
Often likened to a grain of rice, this “copepod”—or microscopic crustacean—is the keystone of the sub-polar food web that makes the Gulf of Maine one of Earth’s richest marine ecosystems. By munching on phytoplankton and microzooplankton invisible to the naked eye, Calanus pack themselves so densely with fatty acids that researchers call them “butterballs” of the sea. Species that directly eat Calanus at some point in their lives include herring, mackerel, cod, basking sharks, haddock, redfish, sand lance, shrimp, lobster and right whales. The tiny crustaceans fuel the vast North Atlantic food web, where bigger fish forage on smaller fish until the bigger fish end up in the bellies of seabirds, seals, tuna, other flesh-eating sharks and whales—or on our dinner plates.
Bigelow Laboratory zooplankton biologist David Fields has said that the ideal timing of the Calanus finmarchicus life cycle for fish larvae in the spring and whales in the late summer is one of the top examples of why the Gulf of Maine “is beautifully intertwined and synchronous. It is what has made the ecosystem so productive.”
That very synchronicity, Fields said, also makes Calanus highly vulnerable to the gulf’s warming. It makes these tiny creatures a giant symbol of climate change. These metaphoric grains of rice in the ocean are now, like grains in an hourglass, slowly draining away.
Dramatic declines
The Gulf of Maine already marks the southern end of the range for Calanus finmarchicus on this side of the Atlantic. With record warmth in recent years, the species is in a decline that correlates with right whales bypassing the gulf in search of food hundreds of miles to the north in the Gulf of St. Lawrence. There are also early correlations with a decline in baby lobsters. While scientists are often careful to say that correlations do not necessarily mean causation, the decline of Calanus populations coincides with current and projected declines for many fish populations in the gulf.
Last summer, a major summary paper on expected climate-driven changes to the Gulf of Maine by 2050 estimated that current global warming projections mean that populations of lobster, cod, haddock, pollock, herring, northern shrimp, Acadian redfish, and red hake will all be diminished further than they already are. That finding adds to a 2016 assessment by two dozen scientists at the National Oceanic and Atmospheric Administration which found that more than half of more than 80 fish species on the Northeast US Continental Shelf have a high or very high probability of distribution shifts due to climate change.
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Core populations of lobster have moved northward more than 100 miles over the last half century, giving Maine a momentary boom while lobstering has crashed in Rhode Island, Connecticut, and Long Island Sound. Last year was the most valuable in the history of Maine’s lobster industry, with 108 million pounds of crustaceans bringing in $725 million in value. But lobsters are moving so fast toward Canada that there are signs that Maine has already peaked in volume.
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Compound impacts
The bedeviling thing about the shifts, according to Andy Pershing, director of climate science at Climate Central, and one of the authors of the 2050 summary paper, is that warming is unleashing “compound events” that can spur species’ declines. As a human parallel, Pershing cited Hurricane Ida’s landfall last year in New Orleans. He noted that while some people died during the actual hurricane, far more succumbed to the heat wave that followed because of a lack of power and air conditioning.
In the oceans, the climate-driven warming temperatures set catastrophe in motion. One example is Maine’s northern shrimp, which was a sweet, crawfish-sized regional winter delight. The shrimp fishery has been closed since a crash of the species following the hottest waters on record in 2012. A study last year found that the crash was not directly due to the heat. It was more likely that shrimp were gobbled up by longfin squid attracted by the warmer waters. The study’s authors said their findings “provide further evidence that changing species interactions will have major impacts as ecosystems face disruptions due to climate change.”
Catastrophic effects on seabirds
Last summer, I personally saw how “compound events” create chaos for seabirds at one end of the Calanus food web. I spent several nights on three islands managed by National Audubon’s Seabird Institute and the Maine Coastal Islands National Wildlife Refuge. I had visited there many times since 1986, but had never previously seen so many carcasses of tern and puffin chicks strewn across the landscape. Nor had I experienced what I realized was a funereal quietude from the absence of terns screeching to help protect their chicks.
The die-off was the result of a relentless double whammy of heat waves and record rain events. Some chicks starved because the heat drove traditional puffin and tern prey—such as haddock, hake and herring—too far away or too deep for parents to catch. Others died of hypothermia because they could never dry out from the rain. Steve Kress, the retired founder of the 49-year-old Project Puffin, told me that Eastern Egg Rock, the first island he repopulated with that bird, endured 54 days of rain events. The prior record was 32.
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Record heat
What a tern, whale or puffin will return to after their winter migrations depends increasingly on whether humans act to curb the warming. The Gulf of Maine Research Institute (GMRI) recently announced that last fall was the warmest on record in the gulf. Average sea surface temperatures in early October that used to hover around 60 degrees Fahrenheit were nearly five degrees warmer. Even in November, a month where temperatures historically descended into the high 40s, they stayed in the low 50s.
The data shows that sea surface temperatures last summer were the second warmest ever recorded in the gulf, four degrees Fahrenheit higher than the historical average. The six warmest summers ever recorded for sea surface temperatures in the Gulf of Maine have all been logged since 2010. In 2020, the gulf hit a single-day sea-surface record temperature of nearly 70 degrees. The primary reason is that the warm Gulf Stream is expanding its presence as cold currents coming down from Labrador are losing their power.
“We’re getting to levels that are really exceptional,” Mills said. “We’re already running ahead of climate models. There’s always going to be some year-to-year variability, but the warming has become a persistent pattern where variability doesn’t get us back to ‘normal,’” she added.
For cold-water sea animals, such a four-to-six-degree difference in sea temperatures is akin to stepping out of an air-conditioned home into punishing Arizona summer heat. The big question is can humans keep nature’s “air conditioner” running in New England.
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https://blog.ucsusa.org/derrick-jackson/a-big-climate-warning-from-one-of-the-gulf-of-maines-smallest-marine-creatures/
