A L E U T I A N I S L A ALASKA N D S (U.S.) YUKON Anchorage

Prince COURSE CORRECTION Kodiak William Island Sound Climatic shifts and periodic anomalies—such as A Changing Sized to scale El Niño, the Pacific Decadal Oscillation, and the Food Web Gulf of unprecedented warm-water “blob” that began in Alaska late 2013—can rearrange food webs, alter marine Energy moves through oceans in a complex web as animals eat algae, habitats, and change the geographic distributions bacteria, and other animals. Relationships between predators and prey are Cassin’s auklet 13-15 in of birds, fish, marine mammals, and sea turtles. in flux. Some animals change diets during their life stages, as the seasons Ptychoramphus aleuticus

)

shift, as they migrate, or as the ocean cycles between warm and cool periods. m

r

a

Pacific Coast w (

PRIMARY PRODUCERS AND CONSUMERS SECONDARY CONSUMERS TERTIARY CONSUMERS APEX PREDATORS t Ocean sunfish and From Mexico to Alaska, one of the planet’s most productive marine n e common thresher shark r r Rarely found north of systems is sustained by movement. Currents, tides, and winds help Producers such as giant kelp and These animals—which include small Dolphins, sea lions, and large fish Orcas, great white sharks, and other top u Vancouver Island, these 26% Primary C fish were seen in Alaska. produce food. Migrations, both horizontal and vertical, transport phytoplankton make their own food consumers fish, baleen whales, squid, and whale such as tuna typically eat secondary predators eat secondary and tertiary a k s through photosynthesis or, in the deep sharks—eat primary consumers, consumers, although some also prey consumers. They have few natural a energy as food, adding to the region’s diversity of life. But warming l sea, through chemosynthesis. Primary 58% Primary such as zooplankton, shellfish, on primary consumers. Most seabirds predators and promote biodiversity by A Humpback whale S producers 16% <1% <1% u Haida Gwaii These whales feed across consumers feed on producers. and jellyfish. are tertiary consumers. limiting populations of other species. m waters and other changes are transforming this ecosystem. the North Pacific coast in m (Queen Total marine biomass* e summer. A group stayed in r Charlotte Is.)

f Monterey Bay to feed instead e

e

Pacific d of migrating to Mexico.

i n

g

r

Ocean a

n

g

e

c acifi North P V

a n c ) o warm Current ( u v e BRITISH COLUMBIA B r e I Sooty shearwater 40 in Wingspan a s l C c a Vancouver Ardenna grisea a h n li i d fo n r g C n A r NA Steller sea lion 8-11 ft ia a DA n UN C g ITE Eumetopias jubatus 7 ft e D Bonaparte’s gull 33 in Black-footed albatross u Seattle ST r AT Fin whale 72-82 ft Chroicocephalus philadelphia Phoebastria nigripes r ES e Balaenoptera n WASHINGTON t physalus ( Cassin’s auklet c o Tens to hundreds of times the o l ) normal numbers were found dead on beaches during the winter of 2014-2015. Fishing OPEN-OCEAN HABITAT Humans are part of the The pelagic zone, or open sea, is marine food web. Overfishing By-the-wind sailor 2-4 in Common murre 28 in Earth’s largest habitat, home to small OREGON Bull kelp removes some species faster Velella velella Uria aalge organisms such as krill, large fish such Nereocystis than they can reproduce, and as swordfish and tuna, and seabirds Sardine luetkeana Carbon dioxide dragging nets along the Egg production such as albatrosses. Eureka Sunlight seafloor destroys habitat. moved north.

CALIFORNIA Phytoplankton Krill Zooplankton Sea otter 4-5 ft Body length Through photosyn­thesis, Small animals called Enhydra lutris microscopic plantlike zooplankton consume San organisms called phytoplankton, and Ocean sunfish 6-14 ft Francisco phyto­plankton convert in some cases, larger Mola mola Santa Cruz sunlight, carbon dioxide, ones eat smaller zooplank- California sea lion 6-8 ft TOXIC ALGAE BLOOM Monterey Bay ton. They are eaten by fish, and water into food for Zalophus californianus Giant kelp living things. birds, and mammals. Some types of the algae Pseudo-nitzschia California sea lion Macrocystis pyrifera Sea lions often suffer seizures and die grow rapidly in warm water, producing Mothers that normally prey after eating fish that consumed toxic massive blooms that contain domoic acid, a on small fish such as sardines algae. Also, thousands of California powerful neurotoxin. When consumed by abandoned their pups to Krill sea lions starved in 2014 and 2015 zooplankton, shellfish, and fish, the toxin expand their search for food. when their usual prey, sardines and Humpback whale 42-50 ft can sicken or kill birds and mammals. anchovies, moved north. Los Angeles Megaptera novaeangliae During the warm spell, millions of Leopard shark 4-7 ft anchovies congregated in Monterey Triakis semifasciata UN Bay, drawing dozens of humpback S IT whales that stayed year-round TA ED M T rather than just a few months. E ES XI CO Copepod

B Sea nettle jellyfish 1 ft Diameter A Oil sac Orca (killer whale) 23-32 ft J Chrysaora fuscescens A Orcinus orca life-size Pacific C A L I Ocean F Cold-water Warm-water O species species R N 45-60 55-70 mi 100 I 0 A Temperature range, Common murre 0 km 100 degrees Fahrenheit

NUTRIENTS Great white shark 15-20 ft Nitrogen, phos- When waters warm, Carcharodon carcharias phorus, and other cold-water species of Juveniles in Southern California nutrients in the water zooplankton such as stopped migrating south when copepods are replaced waters warmed from 2013 to act like “fertilizers” Dall’s porpoise 6-8 ft Short-beaked by subtropical species, 2015, which led to more that help primary common dolphin 5-8 ft which provide less fat Phocoenoides dalli producers grow. sightings by surfers. Kelp forest and nutrition for creatures Delphinus delphis These giant primary producers provide Cold waters carry higher in the food web. Leatherback turtle 4-7 ft food and shelter for many animals. Scien- more nutrients than Dermochelys coriacea tists are studying how some kelp helps warm waters. remove carbon dioxide from the ocean, offering a defense against acidification.

Sunflower sea star 3 ft Normal Upwelling with Pacific sardine 8-15 in Market squid 6-11 in Pycnopodia helianthoides upwelling a warm event Sardinops sagax Doryteuthis opalescens These small, fatty fish are a major food source for many larger fish and marine mammals, but they BOTTOM HABITAT naturally cycle through In the benthic zone, sediment on the boom-and-bust periods. Brain stem Albacore tuna 3-4 ft Long-beaked Common thresher shark 10-18 ft Normal Future seafloor provides habitat for bottom SUPPLEMENT TO NATIONAL GEOGRAPHIC, SEPTEMBER 2016 Hearing disrupted Thunnus alalunga common dolphin 6-9 ft Alopias vulpinus dwellers that feed on other animals and Yelloweye rockfish 3 ft EDITOR: FERNANDO G. BAPTISTA. ART: FERNANDO G. BAPTISTA. DIAGRAMS: DAISY plants or on dead and decaying organisms. Sebastes ruberrimus Delphinus capensis CHUNG. MAP: LAUREN E. JAMES Optic lobes RESEARCH: NORA GALLAGHER, PATRICIA HEALY, TARYN L. SALINAS, HEIDI SCHULTZ, AND RYAN T. WILLIAMS Vision impaired 600 ft TEXT: CRAIG WELCH AND MARLA CONE SOURCES: CALIFORNIA CURRENT INTEGRATED ECOSYSTEM ASSESSMENT; ANDREW Lack of LEISING, BILL PETERSON, AND WILLIAM J. SYDEMAN, NOAA; JOHN F. PIATT, USGS; Oxygen Expanded NICK BOND, UNIVERSITY OF WASHINGTON; (ANIMALS) SOPHIE WEBB; (BIOMASS) awareness Brain OCEAN ACIDIFICATION LOW OXYGEN ISAAC KAPLAN, NOAA; (CURRENTS) TOBY GARFIELD AND PHYLLIS STABENO, NOAA; of danger Humboldt squid 2-6 ft minimum oxygen (FISH BRAIN) DANIELLE DIXSON, UNIVERSITY OF DELAWARE; (KELP) ARLEY F. MUTH, More than a quarter of the carbon dioxide released by Pink salmon 1-2 ft Warm water holds less dissolved oxygen, and MOSS LANDING MARINE LABORATORIES; (RANGES) JULIA PARRISH, UNIVERSITY OF Dosidicus gigas zone minimum WASHINGTON; ELLIOTT L. HAZEN, NOAA; (OXYGEN MINIMUM ZONE) KAREN WISHNER, human activities ends up in the ocean, making the sea more Oncorhynchus gorbuscha because it’s lighter than cold water, there’s less mixing zone UNIVERSITY OF RHODE ISLAND; (SALMON) SCOTT HINCH, UNIVERSITY OF BRITISH Low-oxygen zones are expected COLUMBIA; (SEA-SURFACE TEMPERATURE) NATE MANTUA, BOYIN HUANG, AND acidic and reducing calcium carbonate, which oysters, to expand as climate change These fish prey on pteropods, to carry oxygen down from the surface. With climate OTHERS, NOAA; (SHARKS) GEORGE H. BURGESS, FLORIDA MUSEUM OF NATURAL 3,000 ft HISTORY; (WHALES) ANNALISA BERTA, SAN DIEGO STATE UNIVERSITY clams, and others need to grow shells. Acidifying oceans reduces ocean water mixing. tiny, floating snails that are Chinook salmon 3-5 ft change, low-oxygen zones are expanding, forcing Animals shown approximately to scale Olfactory nerves PRODUCTION: DAISY CHUNG MAP EDIT: GUS PLATIS also can disrupt the brains of fish, upsetting their ability to Oncorhynchus marine animals closer to the surface, where they are in this perspective, except for sooty Sense of smell Humboldt squid seem to thrive extremely vulnerable to tshawytscha shearwater and Cassin’s auklet diminished sense prey, elude predators, and locate their home territory. near these zones. ocean acidification. more vulnerable to predators. *PERCENTAGES DO NOT ADD UP TO 100 BECAUSE OF ROUNDING.

A Shifting Balance

Normal upwelling Upwelling with a warm event Winter downwelling Downwelling in summer +1.4 Global CALIFORNIA UPWELLING ALASKA DOWNWELLING WARMER TEMPERATURES February surface temperature THE BLOB MAY 2015 El Niño events North deviation, degrees Fahrenheit U.S. In spring and summer along the West Nitrate-rich seas flow north from British Oceans stabilize climate by capturing and Pacific In the winter of 2013-2014, a high-­pressure Surface Strong surface Weak surface +0.7 Coast, winds push surface water offshore, Columbia into the Gulf of Alaska, mixing releasing heat. El Niño produces short-term ridge blocked storms that normally cool PACIFIC winds winds winds OCEAN drawing cold water up from the deep. with iron-rich water from streams and temperature spikes in the North Pacific. the Gulf of Alaska. This created a pool of CANADA Warm, nutrient-poor Buildup of warm, Upwelling of these nutrient-rich seas feeds glacial runoff, a combination that helps Iron-rich Weak glacial But human-induced climate change also 0 unusually warm water that spread farther phytoplankton, supporting abundant marine water nutrient-poor water drive productivity. Strong winds near the warms the ocean, with global average and deeper than any other on record. The Nutrient glacial runoff Less nutrient runoff NORTH life. In El Niño years, the warm-water layer Coastal Nutrient-poor shore push surface waters down as the mixing mixing sea-­surface temperatures steadily rising -0.7 heat altered food webs, shifted migrations, upwelling coastal Strong Weak AMERICA is thicker, so upwelling draws from less Cool, nutrient-rich current circles counterclockwise along the Cool, nitrate-rich and setting new record highs. The North and fueled toxic algae blooms, offering a 0 mi 600 productive seas, reducing the food available upwelling Aleutian Islands. When winds are weak or downwelling downwelling Pacific warmed gradually until an extreme glimpse of how future warming may water water 0 km 600 UNITED in the upper ocean. runoff tapers, downwelling can stagnate. event took place from 2013 to 2015. 1880 1900 1920 1940 1960 1980 2000 2016 change the eastern Pacific. STATES