The Next Species: The Future of Evolution in the Aftermath of Man

by Michael Tennesen

  Still his biggest concern is the changing face of oxygen in the deep ocean, here and in the oceans around the world. Gilly referred me to a paper by Lothar Stramma, a physical oceanographer at Kiel University in Germany, who led a study in 2008 that analyzed oxygen content at six different spots in the deep waters of the Pacific, Atlantic, and Indian Oceans. That study found significant increase in low-oxygen water in most spots, and these areas, known as oxygen minimum zones, were below the livable threshold of many marine animals. These low-oxygen zones are a natural phenomenon of the eastern Pacific Ocean and occur in the upper layers of the water, but they are expanding in all directions worldwide. Scientists link this change to global warming.

  The oxygen minimum zone restricts the depth to which tropical open-ocean fishes, such as marlin, sailfish, and tuna, can go by compressing their habitat into a narrow surface layer, where they are more easily fished out. In general, the Pacific has lower oxygen minimum zones than the Atlantic. German oceanographer Stramma said that the lowest oxygen value in the Atlantic found in the 2008 study was 40 percent saturation (surface is 100 percent), whereas in the Pacific there were oxygen minimum zones that reached almost zero percent.

  This has serious consequences for marine organisms. According to Gilly, at 10 percent dissolved oxygen content in the water, microorganisms can no longer utilize oxygen and start metabolizing nitrogen compounds, releasing nitrates, which are strong greenhouse gases. “At zero percent, microorganisms start metabolizing sulfate ion compounds and releasing hydrogen sulfide, and that can be lethal,” said Gilly. During the Permian extinction the oceans went stagnant in places, caused by a loss of ocean currents. Douglas Erwin at the Smithsonian thinks that the emergence of this chemical compound into the atmosphere may have been one of the dominant killing forces at the time.

  Humboldt squid feed on lantern fish in the Gulf of California but may prefer hake in Chile and Peru as well as off Northern California. “Hake” is a term that includes any of several large marine fishes of the cod family. South American authorities struggle with problems in their hake fishery, which is squeezed between overfishing and oxygen-starved waters. Northern California’s hake fishery has not been affected by oxygen-starved waters, though bottom-dwelling creatures have.

  Off the Oregon and California coasts, the oxygen minimum layer is rising up and moving nearer the shore. “It’s intersecting the continental shelf and moving rapidly inland like a river breaching its levees,” said Gilly. “And there are a lot of things that live at the bottom that can’t swim away.”

  The presence of large numbers of Humboldt squid off the Pacific Northwest has impacted the valuable hake fishery there. For example, in 2009 there were so many squid present in the areas of hake schools that sonar estimates taken of hake numbers could not be used to set national quotas for the US and Canadian hake fisheries.

  Few predators catch squid at these depths. Gilled finfish like tuna and shark can dive to the upper limits of the oxygen minimum zone and feed on squid there, but few can go into the zone and stay there for a significant length of time. Scientists at Stanford University have tracked great white sharks, which migrate annually toward Hawaii, and have found that large numbers of these animals stop en route at a mid-ocean area called the “White Shark Café,” where they repeatedly engage in dives above the oxygen minimum zones. Whether they are mating or feeding is not yet known, but Gilly thinks they could be diving for Humboldt squid or the purple-back flying squid that may also inhabit the area.

  Fertilizer runoff from the mainland shores in the northeastern part of the Gulf may be enhancing the low oxygen effects here. Such runoff has created dead zones at the mouth of the Mississippi River in the US; the mouth of the Yangtze River in China; within the Black Sea Basin in eastern Europe; in the Skagerrak, the strait that separates Norway and Sweden from Denmark; and in the Cariaco Basin, near the coast of Venezuela. There are more than 150 such dead zones around the world.

  The difference between dead zones and low-oxygen zones is that the latter involve an oxygen deficiency in the specific layer of water that forms beneath the maximum depth of daytime surface light in coastal and mid-ocean environments. Scientists measuring that layer of water, between 650 and 3,000 feet (200 and 700 meters), have found a measurable decrease in oxygen and an expansion of the vertical and horizontal limits of the layer over the last fifty years.

  This maximum depth of daylight surface light is also known as the deep-scattering layer, a name given to it by twentieth-century naval captains who found that sonar gave a false seafloor echo as it bounced off this zone because of the high density of marine life present. Plankton and zooplankton congregate in the deep-scattering layer primarily to avoid visual predators, and their feeding habits use up dissolved oxygen in the water, creating the oxygen minimum zones.

  Few marine creatures have adapted to the oxygen minimum zones. But Humboldt squid are one of these low-oxygen-tolerant wonders. When they enter the zone, their metabolism slows and they consume less than 20 percent of the oxygen they need at the surface. Specialized gills allow them to scavenge oxygen from the water more efficiently. Their hearts don’t race wildly as they chase down their prey, since their prey are slowed down by the lack of oxygen as much as the squid are. “It’s not like a lion chasing after a gazelle,” says Gilly. “They catch fish with little effort.”

  What are known as “common market squid,” a smaller but important part of the California fishery, probably find such zones lethal. Gilly, who has studied both common market squid and Humboldt squid for decades, believes that increasing loss of oxygen in the seas will lead to the expansion of Humboldt squid from this point forward. This is bad for finfish, as the larger fish—already crowded into shallower oxygen-rich zones—will become more vulnerable to commercial fishing. Such a situation is happening now off the coast of Peru and Chile around the Humboldt Current, one of the richest fisheries on earth, where catches are high but the sustainability of these catch rates is in doubt.

  Climate change is the chief suspect in this developing tragedy. Warmer ocean waters hold less oxygen, and a warmer climate generates less wind to oxygenate surface waters. The result is a more stratified ocean with a surface layer of warm water riding on cooler, denser water, which impedes the mixing of oxygen. In addition, shrinking ice at the poles may be slowing deep-ocean circulation, which brings oxygenated waters to the deep waters of the Pacific and Atlantic Oceans.

  During that Permian extinction 250 million years ago, increased atmospheric CO2 warmed the planet, which stripped the ocean of its oxygen and wiped out more than 90 percent of the creatures in the sea. Oxygen deprivation was a major source of extinction during the Cretaceous extinction as well.

  Bigeye tuna, swordfish, and sharks can dive to the top of the oxygen minimum zone, but few finfish can go into it for any length of time. Sperm whales, elephant seals, and some sea turtles are among the best penetrators of this zone, but it takes serious adaptations to withstand the pressure and the lack of oxygen. For the few that can, the upper boundary of the oxygen minimum zone is a hidden treasure where life abounds.

  FOLLOWING STEINBECK

  To show the extent of change that has occurred over the last half century, Gilly likes to refer to descriptions by the author John Steinbeck and the marine biologist Ed Ricketts, who in 1940 took a trip around the Baja Peninsula into the Gulf of California surveying the marine life. Steinbeck wrote a book about the journey, called The Log from the Sea of Cortez—the Sea of Cortez being the more traditional, more romantic name for the Gulf—describing his trip with Ricketts and a crew of fishermen from Monterey, California. Steinbeck had featured Ricketts, who made a living at his lab on Cannery Row by preserving specimens of marine life and selling them to schools for use in biology laboratories, in two of his novels, Cannery Row and Sweet Thursday.

  The purpose of the Steinbeck/Ricketts expedition in 1940 was to collect samples in the tide pools along the shores of the Gulf of California over a six-we
ek tour. The group left Cannery Row in Monterey at a time when Hitler was invading Denmark and moving up toward Norway and “there was no telling when the invasion of England might begin,” wrote Steinbeck. But they put the world’s drama in their rearview mirror, and boarded the Western Flyer, a chartered sardine boat, heading for Baja California, Mexico.

  Three days later, they eyed the lighthouse at Cabo San Lucas, at the southern tip of the peninsula, and at about 10 p.m. they rounded the cape and entered the dark harbor. Except for the lighthouse, there were no lights in the harbor. Today, Cabo San Lucas is a full-blown mega-resort, with lights that stay on all night. Then it was a sleepy little village where it took Steinbeck and Ricketts all day to find the authorities in order to get their visas stamped.

  The first Mexican town Steinbeck described at length in The Log from the Sea of Cortez was La Paz, a large port around the southern tip of Baja coming from the Pacific. I visited La Paz last summer and witnessed the various efforts being made to compensate local fishermen for the reduced catches they and their hungry families are encountering.

  Frank Hurd is the science director of Olazul, a group of American and Mexican scientists and innovators working with local fishing communities to develop sustainable systems of aquaculture as an alternative to depleting overfished stocks. Hurd invited me to see his version of an offshore, semimobile aquaculture pen. One morning before dawn we drove out from the city to a fish camp on the northern shores of La Paz where Hurd and his associates had been testing a spherical pen, 277 cubic yards (212 cubic meters) in volume, about three miles offshore. Hurd said Gulf currents could flush out the wastes and bring in nutrients and oxygen for the shrimp he was testing. The structure was made from recycled and reinforced polyethylene timbers wrapped in coated steel mesh netting “built to withstand the occasional hurricane that rolls up the Mexican shoreline during the summer and early fall,” said Hurd.

  In his book, Steinbeck had described on their Sea of Cortez journey how they trolled a couple of lines off the back of their boat and were pretty much able to keep themselves in finfish such as yellowfin tuna, skipjack, Mexican sierra, red snapper, and barracuda the whole trip. Hurd said that the local fishermen in La Paz described similar catches in the old days but today try to make a living selling trigger fish, sand bass, bonito, mackerel, and other species that were considered trash fish back in Steinbeck’s time.

  The Sea of Cortez that Steinbeck investigated over seventy years ago is not the same body of water that Gilly and his crew motored to in 2004. In his log, Steinbeck described marlin and swordfish frequently leaping out of the ocean into the air and dancing across the surface of the water. The scientist described seeing only a couple of small squid on his entire six-week excursion in the Gulf of California. And there was nothing that resembled a Humboldt squid.

  Gilly also spent some time looking through historical records for sightings of Humboldt squid. There were isolated reports in the scientific literature going back to 1938, but no reports of large numbers until commercial fishing for them commenced in the late 1970s. He queried a number of old fishermen in the Gulf, and none of them remembered sighting the squid before that. Humboldt squid were absent in the natural history of the Gulf written by early Jesuit missionaries. James Colnett, an officer of the British Royal Navy, saw no Humboldt squid in the area south of Cabo San Lucas in 1793–94, though he described squid “of four or five feet in length” at the surface off the Galápagos Islands. “But that’s a far way off,” said Gilly. The squid must have migrated to the Gulf of California since Colnett’s time, but details of the move are lacking.

  Humboldt squid appear to have evolved in the southeastern Pacific where El Niño events warm the surface waters of the ocean every four to twelve years, creating unusual global weather patterns. Changes in the Humboldt squid fishery mirror changes in El Niño–driven weather. Though Gilly and his associates measured high concentrations of squid in the central Gulf in 2012, they had moved away from the shore and their sizes had decreased. Gilly thought an earlier El Niño event in 2009–2010 led to the animals’ accelerated sexual maturity, what he called an even more radical live-fast-die-young life strategy in the face of an uncertain future.

  Humboldt squid have two tentacles that can reach out and grab prey and eight arms to envelope them. The squid can attain eight feet in total length (mantle plus tentacles). They use their tentacles and arms to subdue prey and their razor-sharp parrotlike beaks to tear them apart. They are some of the fiercest of the cephalopods, a group of animals that includes squid, cuttlefish, and octopus.

  Humboldt squid are also famously cannibalistic. Unai Markaida, a marine biologist at El Colegio de la Frontera Sur in Campeche, Mexico, studied prey items of 533 Humboldt squid and found evidence of other Humboldt squid in 26 percent of their stomachs. Fishermen who pursue the Humboldt squid tell scientists that once squid are hooked, other squid start attacking and eating the fishermen’s catch. The fishermen have to pull their catches in fast to avoid these voracious attacks.

  The Humboldt squid is particularly fast and propels itself through the ocean as if by jet engine. It draws water into its mantle and then ejects it through a spout like a rocket. All squid have the ability to change color quickly, some imitating patterns, even textures of sandy bottoms or rocky reefs. Humboldt squid lack this patterning capacity but are able to switch back and forth from maroon to ivory, pulsing like a strobe. The capability to communicate through color change is quite profound for a creature that is related to the snail. According to Gilly, “There’s jitter [vibration], variation, and change in the frequency between two squid. It’s highly unlikely this isn’t some kind of communication.”

  Up to four million Humboldt squid hang out in the Sea of Cortez near Santa Rosalía at about one thousand feet (three hundred meters) during daylight near the shelf where the bottom starts falling off sharply, but move up at night when the deep-scattering layer moves up as well. It’s then that the fishermen initiate their attack. Hauling up a squid that can weigh up to a hundred pounds by hand lines is a rough job at night, particularly when the average price for cleaned squid is less than ten cents a pound (0.5 kilos).

  One winter day, I caught up with Bill Gilly at the Hopkins Marine Lab on Cannery Row, next to the Monterey Bay Aquarium. People claim there are differences but also a lot of similarities between Gilly and Ed Ricketts, who accompanied Steinbeck on his journey to the Sea of Cortez.

  Ricketts’s lab on Cannery Row was a hangout for authors, illustrious locals, and street people. Gilly’s lab is more of a gathering place for assorted Stanford students. Ricketts, according to Steinbeck, lived across from the local house of prostitution but never visited the house after dark unless he’d run out of beer and the stores were closed. Gilly lives next to the Monterey Bay Aquarium and goes there frequently. In Steinbeck’s eulogy he said Ricketts “loved to drink just about anything.” Gilly would admit only to enjoying the occasional beer. Their greatest similarities are that Gilly, like Ricketts, is a biologist who loves Monterey, Baja, and the Gulf of California and likes to laugh.

  When Gilly announced his plan to retrace Steinbeck and Ricketts’s 1940 voyage through the waters and intertidal zones of the Gulf of California, he received a surprising call of support when the owner of North Coast Brewing Company called and offered his services. “You know those guys drank a lot of beer on that trip,” he said. “And I’m the man that can help you with that.” Gilly reacted with a smile.

  Gilly and his team arrived at the boat on their date of departure and found two shrink-wrapped pallets of beer with a sign on it that said FOR DOCTOR GILLY. Inside the shrink-wrap were seventy-two cases. “It was the most beer I’ve ever seen outside of a Princeton reunion I once attended,” laughed Gilly when he told me the tale.

  In the end, Gilly and his crew drank only about 1,242 beers. Steinbeck and his crew drank 2,160 beers. “And they did that with a smaller crew and a shorter trip,” said Gilly in awe.

  There were ot
her differences in the two expeditions that were not as lighthearted. At the various intertidal zones that Steinbeck and Ricketts visited, the author repeatedly used expressions like spiny-skinned starfish in “great numbers,” and “knots” of brittle stars, but Gilly’s team did not observe a great number of either at any of the tide pools they witnessed.

  Steinbeck and Ricketts encountered “huge” conches and whelks (large sea snails and their shells) at several sites and a great number of large Turbo snails (shaped like a turbine). Gilly’s crew found only small living specimens of conches and Turbo at just a few sites, and dead whelk shells at one. In 1936, William Beebe, an American naturalist, explorer, and marine biologist, found a beach just north of Bahía Concepción—about midway up the eastern shore of the Baja—that was what he called “a conchologist’s paradise,” with shells “of amazing size and a host of species.” Tellingly, Gilly’s crew found a dramatic decline in all these species.

  One of the greatest and most disturbing changes in the Gulf is in the “pelagic,” or open-ocean, predatory finfish that inhabit the upper portion of the water column and aren’t associated with the shore or the bottom. Although Gilly and company traveled at the same time of year, using the same type of boat, and for about the same duration as the Steinbeck adventure, they witnessed a greatly changed community of open-ocean fish.

  Steinbeck and Ricketts wrote, “We could see the splashing of great schools of tuna in the distance, where they beat the water to spray.” The pair also saw marlin, sailfish, and swordfish, but Gilly’s team sighted few of these.