Part I

Big Blue

In the middle of the Pacific Ocean, late in the year 1820, a colossal sperm whale rammed the Essex, a 240-ton whaling ship from Nantucket, crushing the bow and sending the wooden vessel gurgling to a watery grave. The high seas battle was dramatized by Herman Melville in his classic novel Moby Dick. After the whale struck, Captain Owen Pollard, first mate Owen Chase, and the ill-fated crew took refuge in three shallow-draft dories. These twenty men had the misfortune of being marooned in one of the most remote and lifeless places on the planet: the open ocean of the southern Pacific. Its seemingly hospitable, equatorial waters are so devoid of fishes and marine life that the castaways very nearly starved to death. In the weeks that followed, the men were unable to catch even a scrap of food to sustain themselves. More than half perished. In a gruesome plot twist, they even resorted to eating the deceased, in a wretched attempt to stave off starvation. Earth’s marine world, in places and at times so bountiful that schools of fish can be measured in miles and by tons, here was so barren as to sentence Pollard and Chase to death by famine. How, they must have thought, can such warm tropical waters, so transparent and welcoming, afford us so little to eat?

Life in the oceans, as on land, starts with sunlight. The sun’s rays filter into just a thin skin of the sea, down to only a few hundred feet. Living in those illuminated surface waters are tiny algae which, like the lowly grasses of the Serengeti, sustain a multitude of animals and the ecosystem that knits them together. Sunshine powers photosynthesis, the biochemical magic trick that turns carbon dioxide into sugar and starch (and oxygen). Photosynthesis fuels algae that sprout into a fast growing, and nutritious, floating lawn on which all other marine life graze. Such plant-like algae are dubbed phytoplankton, and their photosynthetic output is so immense that they manufacture nearly three-quarters of the oxygen in Earth’s atmosphere.¹ Miniscule animals called zooplankton voraciously consume phytoplankton, creatures like copepods (tiny shrimp relatives, occasionally sold as “sea monkeys”), and both mini-animals and pseudo-plants are gulped and strained by a ravenous bevy of fishes.

Virtually the entire web of marine life rests on this proverbial lawn of plankton. Where algae struggle to thrive, the ocean is clear and fishing is meager; but where seawater is a thick, luxuriant broth, fishes abound. Schools of anchovy, sardine, and herring achieve spectacular abundance by feeding on zooplankton. Powerful tuna, marlins, and sharks hunt those schools. Gentle behemoths like manta rays and whale sharks are content to feed directly on the soup of plankton, sieving them from the water just as the giant whales do.

As the crew of the Essex discovered, the distribution of ocean productivity is agonizingly uneven. Much of the sea is barren, and marine life booms in only a select few regions, and on intermittent occasions. Essentially, if plankton can thrive, then marine life flourishes. Just like land plants, phytoplankton rely on sunlight and carbon dioxide for photosynthesis. They require nutrients to flourish, including nitrogen, phosphorus, and iron. And they need oxygen to power their own metabolism, growth, and reproduction. Where, or when, any of these requirements are lacking, the sea is a desert; where they are abundant, it is a banquet.

Sunlight only reaches the upper lamina of the ocean, about 5 percent of all the seawater in the world, leaving the vast depths cloaked in darkness and robbed of productivity. Carbon dioxide is widely available, and increasingly so in recent decades, but oxygen is most abundant only in cold seas. This happens because warm water accelerates the atomic dance of dissolved oxygen molecules, which more frequently bump one another from the aquatic dance floor and into the atmosphere. Most of the great fisheries of the world—sardines, halibut, herring, cod, and more—are found in cold, plankton-rich waters far from the equator.

Nutrients are plentiful near coastlines, where they are transported by rivers like the Mississippi, a watery goliath that injects around 2 million tons of nitrogen annually into the Gulf of Mexico.² Nitrogen and phosphorus fertilize enormous phytoplankton productivity that sustains immense fisheries, but the flow of nutrients soon sinks below the sunlit zone just a few dozen miles offshore. Not just river nutrients, but also the inert bodies of deceased plankton, fish, and all manner of marine life fall to the depths, succumbing to the relentless pull of gravity. Plankton counter this force by packing themselves with buoyant oils that float them near the sunlit surface; breakdown of those oils liberates a unique odor (dimethyl-sulfide) widely recognized as the characteristic smell of the sea.³ Once it sinks beneath the surface, all that nourishment slowly settles to the ocean bottom, in whose inky depths it is greedily awaited by abyssal fishes.

There is only one force on earth that can lift marine nutrition off the seafloor, and that is an upwelling, a vertical current that carries nutrients to the surface like an escalator. Upwellings are driven mostly by global wind patterns, with the trade winds wafting steadily from the east throughout the tropics and the westerlies gusting in the opposite direction in temperate latitudes, both blowing surface water away from the margins of continents. Deep water is drawn upward to fill the void, and a rich brew of fallen plankton, river sediment, phosphorus, fish feces, and other nutrients rises to provoke booms of plankton and explosions of fish populations. Along with the polar seas, the upwelling zones off the west coasts of North and South America, and Africa, are the richest and most productive on the planet.

Unfortunately for Captain Pollard and his crew, their ship had sunk about as far from marine productivity hot spots as one can get. The middle of the south Pacific Ocean boasts sunny skies and warm breezes, but low oxygen levels, no nutrient inputs, and no upwellings. They were stranded in the marine equivalent of the Sahara Desert. The sperm whales hunted by the Essex had gathered in these waters not to feed, but to give birth: the equatorial latitudes offer a balmy and tranquil nursery for newborn calves who would not survive infancy in icy polar waters. Only once they are generously fattened by their mothers’ rich milk can the young leave the tropics and swim poleward, to feed in the fruitful but frigid seas found there.

Other than polar and coastal waters, much of the world’s ocean realm is cursed with low productivity. Upwellings, for example, where nearly half the fishes on Earth are caught by hooks and nets, account for only one percent of all ocean waters.⁴ The remainder of the seas present slim pickings. In the barren zones, predators must be exceptionally mobile, cruising vast empty spaces in search of food that is few and far between. To meet this challenge, tuna and marlins and other top carnivores have evolved into pinnacles of hydrodynamic efficiency that boat designers and Olympic swim teams can only dream of approaching. Powerful and graceful, these finned predators literally crisscross the globe to find outbreaks of phytoplankton and gorge themselves on the bountiful schools of fish that attend them.

One of the most spectacularly fertile places in all the world, and a dining destination for millions of predatory fishes, is the massive upwelling system off the coast of Chile and Peru. There, a combination of polar and deep-ocean waters stimulates a level of productivity that beggars the imagination. Stretching over 2,500 miles, the Peruvian upwelling sustains the world’s greatest population of anchovies and supports the largest fishery on the planet.⁵ We may regard these small, oily fishes merely as a salty pizza topping, but in the ocean they are highly evolved machines for transmuting plankton into muscle. If Captain Pollard’s ship had tussled with the sperm whale near this upwelling, he and his men would have encountered schools of anchovies so dense they could have practically walked to shore on the backs of more than a trillion fish. So copious is their abundance that annual harvests by the Peruvian fishing fleet comprise a fifth of all fish landings on the planet.⁶

For schooling anchovies, the danger does not relent beyond the edge of a knotted net. All manner of predators devour these hand-sized delicacies, plump with oils from feasting on phytoplankton. Bluefin tuna, striped marlins, mackerels, swordfish, and even dolphins commute from far-flung corners of the sea to fatten themselves. But menace can also arrive in the form of a furred sea lion striking from below, or a feathered seabird plunging from above. The immense schools of anchovies sustain sprawling colonies of seabirds, from penguins and boobies to gannets and pelicans. Collectively, those fowl have been dining on anchovies for millennia, and carrying their catches back to hungry beaks in millions of nests that liberally speckle the coastline and nearby islands. Powered by bountiful anchovy feasts, those humble seabirds were not just rearing chicks, but amassing an invaluable resource that would solve one of the greatest problems in human history.