Open Ocean: the Blue Desert
Offshore, away from the conceptual anchor of land, lies another world. It is a vast, open place of endless blue that seems as deep as forever. Here, the water is typically crystal clear and streaked with shimmering shafts of underwater sunlight. For an unbroken 360 degrees, there is no land in sight. No traffic jams, no screaming cell phones, and no blaring advertisements. There is no pounding surf, only gently rising and falling oceanic swells. The open ocean is a world that makes one feel tiny, insignificant, and utterly alone. It is a world that makes it very difficult to avoid imagining some toothy monster rushing up from below and dragging you down to a horrible, bloody death . . .
Near shore, the marine realm is comfortingly familiar: a murky greenish liquid universe swimming, creeping, pulsing, and crawling with an astonishing variety of mostly smallish living things. Away from the continental shelves, the ocean changes dramatically. It become an unimaginably expansive, pellucid ultramarine nothingness. Nutrients are relatively scarce here. The plankton is extra-tiny and very thinly distributed. Living things large enough to be seen with the naked eye are few and far between. But where they occur, they are apt to be either spectacularly abundant or large to downright enormous. Huge schools of thousand-pound (450-kilogram) tunas thrum and wheel, pounding through the nothingness like hyperactive automatons with a schedule to keep. Giant billfishes develop glowing white ‘feeder bars’ as they slash through glinting, wheeling constellations of mackerel. And small pods of enormous baleen whales fast as they migrate to their summer breeding grounds, ponderously pumping their horizontal flukes up-and-down, surfacing periodically to ventilate lungs the size of compact cars. Yet even the enormity of whales is dwarfed by the unfathomable vastness of the open sea, little more than specks of blubber and muscle separated by miles and miles of largely empty, blue water.
This vast, energetically depauperate pelagic realm is also home to some of the most fascinating of sharks, long-distance voyagers whose need to feed and breed compels them to a life of ceaseless searching tempered by the need for economy. No potential meal is too paltry to pass by, no distance too great to traverse if it means an opportunity to contribute genes to future generations of open ocean wanderers.