VOYAGE INTO DARKNESS on March 18, 2016 Researchers Are Learning That Arctic Organisms Aren’T Dormant During the Long Polar Night Downloaded From

NEWS

FEATURES

VOYAGE INTO DARKNESS on March 18, 2016 Researchers are learning that Arctic organisms aren’t dormant during the long polar night Downloaded from

By Eli Kintisch, on the RV Helmer Hanssen, northwest of Svalbard, Norway

t is lunchtime, but the sun is nowhere size of rice grains. with life, even in the dead of winter. They’ve in sight. Just the moon and stars il- Not long ago, researchers would have documented foraging birds and fi sh, masses luminate a black sky above a blacker considered such a scene unlikely. They gen- of surprisingly active zooplankton, and even sea as we motor a small skif along an erally believed marine life this far above signs that some animals are continuously island fjord. The fi ve of us—three re- the Arctic Circle was dormant during the growing and reproducing despite the cold searchers, a crew member, and long polar night, when temperatures and darkness. “We make fantastic discover- a reporter—are encased in plunge and the winter sun dis- ies every time we do a cruise,” Berge says. bulky, full-body survival appears below the horizon for Those fi ndings are driving a “reevaluation” suits in deference to the Svalbard roughly 4 months. “The think- of how Arctic ecosystems behave during the sub-zero January tempera- ing has been: Those who can, polar night, writes marine biologist Geraint Itures here in the high Arctic. migrate out of the Arctic [in Tarling of the British Antarctic Survey in Our eyes acclimate slowly. winter]. Those who can’t … Cambridge, U.K. Forty minutes into our foray, turn of ,” says marine biologist Much about life in the polar winter still we see a green aurora above a Jørgen Berge of the University remains “essentially … a black box,” Berge majestic rock wall that appears, of Tromsø - The Arctic University says. That is why, earlier this year, he led out of nowhere, along the shore. “Can of Norway (UiT). a 17-day research cruise from northern you believe we’re being paid for this?” one Now, Berge and other researchers are Norway into the Arctic Ocean, an environ- scientist marvels. A black-and-white sea- challenging that paradigm. On voyages ment he calls “the least known realm on bird called a little auk emerges from the deep into the polar night—when research the planet.” The 28 researchers aboard the gloom. It dives nonchalantly into the shad- vessels have traditionally stayed away— ship had goals that included testing new

ows to hunt, pursuing tiny crustaceans the they’re ﬁ nding that Arctic waters can pulse technologies for monitoring remote seas, DEJA KAJETAN PHOTO:

1254 18 MARCH 2016 • VOL 351 ISSUE 6279 sciencemag.org SCIENCE

Published by AAAS Northern lights bathe the high Arctic city of Tromsø, Norway, the departure port for a recent polar night cruise by the RV Helmer Hanssen (opposite page).

obtaining better measurements of the polar Arctic expeditions during the eight lighter physical oceanographer with the Scottish night’s eerie “lightscape,” and gaining a bet- months of the year—when the sun is some- Association for Marine Science (SAMS) in ter understanding of how Arctic organisms times above the horizon for 24 hours—and Oban, U.K. cope with the sun’s absence. stay away during the roughly 4 months of Other surprises followed, sometimes There was also a sense of urgency: Climate constant night. aided by fate: In 2012, a cruise scheduled change is remaking the Arctic, and melting In 2007, however, Berge and colleagues for November was delayed until Janu- ice will allow more light to penetrate win- retrieved some unexpected data from a sen- ary 2013 because of ship repairs, enabling ter seas. “This will have a major impact sor moored in a fjord of Svalbard, a rocky biologists to discover unexpected bio- on the ecology,” Berge says. “So under- archipelago that sits about halfway between luminescence and zooplankton at odd standing the relationship between light and the Arctic Circle and the North Pole. The depths, whetting their appetite to learn more. organisms is crucial to understanding the device used sound to track the movements Since then, each winter a tight-knit group of biological future of the Arctic.” of marine organisms, and readouts showed researchers—mostly Norwegian, British, zooplankton periodically migrating up and and American—has reunited in Norway to AS BERGE TELLS IT, the emerging subfield down the water column. That’s typical be- sail into the dark. of polar night biology was born almost by havior during much of the year, when the The goal of this year’s expedition was luck. The conventional wisdom was that creatures rise en masse to the surface at to explore several Svalbard fjords, as well the high Arctic only came alive each spring, night and sink deep during the day, in part as waters adjacent to the Arctic’s ﬂ oating after there was enough sunlight to fuel the to avoid predators. But these movements sea ice. Our vessel was the 64-meter-long growth of phytoplankton, the tiny marine were occurring in January, when Arctic zoo- Helmer Hanssen, named for an early 20th plants that anchor the polar food web. As plankton were expected to be dormant. “We century Norwegian who explored the re-

PHOTO: HINRICH BÄSEMANN/CORBIS HINRICH PHOTO: a result, biologists tended to launch their were ﬂ abbergasted,” recalls Finlo Cottier, a gion by wooden ship and ice sledge. In

SCIENCE sciencemag.org 18 MARCH 2016 • VOL 351 ISSUE 6279 1255

Published by AAAS NEWS | FEATURES contrast, we enjoyed cozy, quiet cabins, microwaves. Crouched behind a bulwark as ate student sorts the krill while wearing a shockingly good Wi-Fi when the satellite co- the wind howls, Cohen programs the sen- headlamp that glows red, a wavelength the operated, and hot Norwegian food, courtesy sor with a small keyboard. No fl ashlights, he crustaceans can’t see. of a chef who jammed on his electric guitar warns bystanders. To study their light sensitivity, research- of shift. The Helmer Hanssen also boasts Repeated measurements show that aver- ers glue live krill to an apparatus that uses well-stocked labs, cranes able to deploy age winter light levels are tens of millions electrodes to measure how their nerves re- sensor-laden buoys into the sea, trawl nets of times lower than those measured during spond to fl ashes of light of dif erent wave- for sampling seafl oor life, and autonomous the Arctic summer. Still, there are subtle lengths. Last year, Cohen showed that krill undersea vehicles bristling with cameras patterns within the winter lightscape: “Fifty react most strongly to the bluish wave- and sensors. shades of gray,” Berge jokes. Sunlight re- lengths that penetrate deepest into the wa- Still, conditions can be harsh. Team fl ected from below the horizon makes the ter column, reaching a depth of 25 m even members spent hours on icy decks wran- day a little brighter than the night, for during the polar night. The experiments, gling wet nets and gear, or below decks example, and the aurora, the moon, and combined with a model of the underwa- fi ghting seasickness and claustrophobia in even the stars add measurable photons. ter light fi eld, strongly suggest the krill labs that often smelled like can “cue upon ambient light fi sh. (“I keep wanting to take during the dark polar night,” a shower, but then I know Cohen and his colleagues re- there’s a trawl coming up so I ported in PLOS ONE last year. put it of again,” said fi sh bio- Other research has high- logist and UiT graduate stu- lighted the unexpected role dent Marine Cusa.) Cruise of the moon’s glow. One study leaders had to cope with by Last and his colleagues— storms that repeatedly reshuf- dubbed “the werewolf paper”— fl ed their plans. Eventually, analyzed several decades of they stopped printing out revi- acoustic data on the move- sions, opting instead to write ments of krill and other zoo- changes on a whiteboard. plankton at 28 sites in the Arctic Ocean. They found that WHEN I COMPLAIN of sea- in December 2015 and January sickness during breakfast one a daily migration can occur morning, a researcher points on a 24.8-hour cycle—which to a porthole. “The best thing synchronizes the organisms’ is to look out at the hori- movements with the rising zon,” advises marine biologist and setting of the moon— Kim Last of SAMS. Everyone rather than a 24-hour, sun- laughs, because there is noth- based cycle. The zooplankton ing to see. During early Janu- also performed a “mass sink- ary here, at about 79° north, ing” to a depth of about 50 the sun never rises; it stays m every 29.5 days in the win- at least 11° below the hori- ter, which coincides with the zon. With luck, at high noon brightest full moon, the re- you might see a gorgeous but searchers reported in January short-lived red and purple sky, in Current Biology. caused by sunlight reflected On this cruise, Last and his around the curve of Earth. colleagues explore whether Scientists want to quantify Polar night cruises give researchers a rare chance to study the winter habits of a krill “have an inherent rhythm” that darkness, to know just wide range of marine organisms, including (from top, clockwise) f sh such as cod, shaping their ability to sense how much light is available f amboyant cnidarians that sift food from the water column, and little auks. the subtle light dif erences during the polar night. The between night and day dur- measurements aren’t easy. Satellite instru- THOUGH SCARCE, the rays are enough to ing the winter. Many animals have bio- ments, which rely on light refl ected from shape the behavior of many Arctic organ- logical clocks that keep track of the time of land, and conventional light meters aren’t isms. In particular, studies of common, day, helping regulate gene activity and other sensitive enough to count the relatively few shrimplike crustaceans known as krill are functions. To see whether the crustaceans photons. So the researchers have hacked a yielding new insights into light sensitivity. have similar internal clocks, the researchers device—originally designed to detect fl uo- During a snow squall, one of the ship’s keep some in cold storage until a time cor- rescence in biomedical labs—that provides cranes hauls up a net shaped like a dead responding to the crustaceans “night”—say, accurate readings. giant squid. Kneeling, Last peers into a 12 hours after a noontime capture—then One day, Last and biologist Jonathan canister at the net’s dripping bottom. Bio- measure their sensitivity to light. They do Cohen of the University of Delaware (UD), luminescent krill, collected from a depth the same for another set, but take the mea- Newark, pull on heavy winter gear and of 100 m, coat the can with a blue glow. surement during the krill’s “day.” climb up to the top deck, above the bridge, He wraps the container tightly in a black Late one night near the end of the cruise, to take a daily light measurement. The trash bag to protect the animals from light Cohen and Last sit reviewing data from the captain has turned of the radar so the and hurries a few decks down to a dark- experiment on a laptop. Their eyes widen.

scientists won’t be exposed to its powerful ened walk-in refrigerator. There a gradu- Indeed, the numbers suggest the krill be- JOHNSEN/NTNU/UNIS ANDRIGHT) GEIR LEFT (BOTTOM, DEJA; KAJETAN (TOP) PHOTOS:

1256 18 MARCH 2016 • VOL 351 ISSUE 6279 sciencemag.org SCIENCE

Published by AAAS Rhythms in the dark In the Arctic fall and spring, krill and other zooplankton dive when the sun is out to avoid predators, and rise to the surface at night. During the polar night, the zooplankton tend to stay deeper in the water column. They rise and fall with lunar cycles, sinking deep to avoid the light of the full moon.

Fall Polar night Spring Daily cycle driven by sun Monthly cycle driven by moon Daily cycle driven by sun

24 days –30 m Krill

6 days –60 m –120 m 24 hr 24 hr

24 Appoximate 12 hours of daylight 0 OCT. NOV. DEC. JAN. FEB. MARCH

come more sensitive to light during their says, “someone is shitting, and if someone is down” regime in which organisms thrive night hours. “Yes!” shouts Cohen, as he and shitting, someone is feeding.” without primary production. “It could be Last exchange a high-fi ve. The fi nding may That is true of the few species of Arctic a system that changes between two states,” help explain how the creatures have evolved birds that don’t fl ee the polar night. In 2014 he says. The zooplankton’s winter diet, to most ef ciently use what scant light ex- and 2015, the researchers observed six spe- however, is still a mystery. One scientist ists here, a crucial aspect of survival. cies actively foraging, including little auks. on the cruise was fi ltering seawater for mi- Many are known to rely on visual cues, but crobes, which might be the missing source SCIENTISTS ARE also examining how the darkness doesn’t seem to bother them. of energy. larger animals, such as cod and birds, can When researchers caught several and exam- Revising ecological dogma in the Arctic eat during the dark winter, when prey can ined their stomachs, they discovered plenty will require more data covering greater be invisible. Deep in the ship, Marine Cusa, of prey; one guillemot had recently swal- spans of ocean, over longer time periods. the fish biologist, spends a good chunk of lowed 214 krill. The birds also appeared to So polar researchers are designing instru- the cruise cutting open the stomachs of cod be specializing on specifi c organisms, not ments that could increase the data yield collected by trawl nets and using a micro- catching a random assortment. Such data from each cruise. During this trip, for in- scope to examine the contents. What she “confi rm active feeding by top predators,” stance, scientists spent one afternoon test- sees at first seems to confirm that the fish Berge wrote last year, but don’t reveal how ing a “jetyak”—an autonomous kayak that can use the meager light of polar night to they’re doing it. could be programmed to conduct biological hunt. Cod netted from a southern fjord that surveys away from the light pollution of a gets more winter light are stuffed with prey, SUCH FINDINGS are prompting new ways ship. Although it performed what one re- but those caught farther north in Rijpfjor- of thinking about the Arctic. One idea is searcher called some “crazy” turns, the team den, which gets less light, are nearly empty. that the existing notion of seasons, which fo- concluded it could be a useful platform. Later, she realizes that something is “re- cuses on temperature, should be expanded ally weird” about that pattern. On a winter to include levels of light, especially in the WHEN THE SHIP FINALLY DOCKS at the cruise just 3 years ago, polar cod netted from water column. The middle of the dark po- Svalbard town of Longyearbyen, most of the Rijpfjorden had full bellies. What might lar night can be relatively warm compared scientists amble to a bar for a long-awaited explain the di! erence? Acting on a hunch, with later months, for instance. In contrast, drink. But Last and Cohen stay aboard, rac- she climbs three fl ights up to the ship’s in- the spring bloom—which is triggered by in- ing to complete preparations for a new ex- strument room—think laptops, body odor, creased light—often occurs when tempera- periment aimed at understanding the genes and dirty co! ee cups—and checks an on- tures are still at a minimum. governing the krill’s biological clock. At line lunar calendar. “Please be full, moon, Textbooks suggest that the bloom kicks regular intervals, they freeze freshly caught please be full,” she pleads. Sure enough, the o! the growth and reproduction cycle of krill in order to stop the ticking of the moon was full when researchers caught most Arctic organisms. But scientists have clocks at different points. Later, back in the the 2013 batch of Rijpfjorden cod; on this netted eggs and larvae that suggest the lab, colleagues will run tests to see which year’s cruise, it wasn’t. “Dun-dun-dun,” she creatures are not only feasting in the dark- genes are active at which times. announces later. “Maybe it’s the moonlight ness, but reproducing, too. “If we hadn’t learned what we did on SCIENCE that helps them hunt!” Such activity might mean that the Arctic this cruise we wouldn’t have done this last Other creatures are also feeding in the has alternating ecological regimes, Berge experiment,” a bleary-eyed Last says. He darkness. Berge and his colleagues have says. In brighter months, it supports a food hopes it will reveal a little more about how found plenty of fecal pellets in the winter web that is driven from the bottom of the the creatures survive their long night. If so, waters, apparently from krill and other zoo- food web, by phytoplankton fl ourishing in a journey into darkness will have shed a bit

ILLUSTRATION: C. BICKEL/ C. ILLUSTRATION: plankton. “If there is shit in the water,” he the sun. But in winter it shifts to a “top- more light on the Arctic. ■

SCIENCE sciencemag.org 18 MARCH 2016 • VOL 351 ISSUE 6279 1257

Published by AAAS