The Arctic Ocean is beginning to look and act more like the Atlantic. It’s a shift that threatens to upend an entire food web built on frigid waters.
On a cool morning in late July, the Oceania, a blue and white, three-masted research vessel, maneuvers through the dark waters of a fjord on the west coast of the Arctic island of Spitsbergen. Craggy peaks streaked with snow rise sharply out of the water. Expansive sweeps of glacial ice plow between mountains and into the fjord, ending abruptly in towering turquoise walls. Chunks of ice drift by, sizzling and popping like sheets of bubble wrap as they melt and release air captured ages ago.
As the ship sets anchor, scientists in wool sweaters, knit hats, rubber boots, and insulated marine jackets spill onto the deck and begin their work. One lowers a silver box of an instrument into the water to record its temperature, salinity, and depth. Another uses a winch to drop a cone-shaped net over the side of the ship to the seafloor. On its way back up, the fine mesh gathers a menagerie of tiny sea creatures, including krill, copepods, other tiny crustaceans, and a couple of grape-sized sea jellies.
The copepods, tiny and transparent with slim red antennae, are the least beguiling of the hoard, but they are the main target. “We want to find out who they are, where they are, and how many of them there are,” says marine ecologist Sławomir Kwaśniewski who works at the Institute of Oceanology of the Polish Academy of Sciences (IO PAN) in Sopot, Poland. These minute crustaceans form the key middle links in a compressed Arctic food web: They are the primary food for Arctic cod, marine birds, and bowhead whales—and the energy and nutrients they contain help sustain seals, reindeer, and polar bears. By studying copepods, along with the Arctic ecosystem they support, from seafloor to bird-covered cliffs, the researchers hope to gain a better understanding of how climate change is restructuring that food web and changing the entire biological character of the Arctic.
At its core, the scientists’ interest in the tiny copepods lies in a relatively recent phenomenon—one they’re calling the “Atlantification” of the Arctic. Years of sampling have shown that the Arctic Ocean is losing its distinctly Arctic traits and becoming increasingly more like the Atlantic. Its sea ice is melting, its water warming. In response, animals from warmer climes are encroaching, leading to a reorganization of its biodiversity. One particular copepod species is providing clues about the extent of the disruption and just how grave it might become.
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