New science has made plain just how important the mesopelagic realm is not only to life in the sea but also to larger-scale biogeochemical cycles on the planet we share. Nearly every dive into the twilight zone reveals never-before-seen creatures, some seemingly designed as extras in “Alien” rather than as practical Earth-bound organisms. A new field of black water photography has yielded among the most stunning images ever seen-exposing just how little we know about what goes on in the abyss. In recent years, citizen scientists have joined them, exploring the nightly darkening zone in scuba gear to capture photographs of never-before-seen organisms moving up from the darkness below. Read the book, “ Below the Edge of Darkness,” for the chapter and verse of this fascinating natural history.Ī cadre of professional scientists have been exploring the twilight zone and deep sea with submersibles and autonomous robots for decades. Among the most stunning are the incredible array of bioluminescence strategies that many denizens of the mesopelagic employ to find prey, to find mates or to otherwise gain a selective advantage. This basic pattern has created selection pressures for all kinds of weird and astonishing morphological, physiological and behavioral adaptations. It constitutes a mighty-if unseen-heartbeat of the sea. The nightly vertical migration that results around the world’s oceans is among the largest animal movement patterns in existence. Perhaps most important is that, as night falls, the edge of darkness ascends towards the surface, allowing swarms of mesopelagic creatures to move upwards to forage before retreating into the abyss as light begins to return. More familiar near-surface organisms, including many marine mammals and large-bodied fishes like swordfish and tunas, know that a wealth of life is there and dive deep to hunt mesopelagic prey. The types of fish species found here are among the least familiar to all but experts: lantern fishes, bristle-mouths and hatchet fishes, among many others. This is no small matter-the organisms of this zone are among the most abundant on the planet, so densely packed in places that they create deep scattering layers, which show up on sonar returns from surface ships. The darkness creates a fabulous place for organisms of many types to hide from visual predators lurking nearer the surface. The mesopelagic zone is not the biotic desert that one might imagine, but rather a swarming sea of life. This twilight realm is called by scientists the mesopelagic zone. In clear ocean water, the light intensity decreases at least ten-fold for every 75 meters of descent, leaving insufficient light for photosynthesis below about 200 meters of depth, but still enough light to see at depths of 1000 meters. The color shifts from brilliant turquoise in clear surface waters to deep indigo and finally charcoal gray dimming to pitch black with increasing depths. We support an immediate moratorium on the development of new fisheries targeting twilight-zone species until we know enough about how these organisms accelerate the sinking and storage of carbon within the oceans to assure protection of that key function.Īs sunlight penetrates into the sea, it is transformed. New science has made it clear that life on Earth may well depend upon the startlingly strange and interesting organisms that live in the oceans’ twilight zone and that we must act now to protect it. Today, the edge of the unknown exists closer than you many think-in the sea, at the wonderful and strange, just-dark middle depths, where light fades and strange creatures lurk. The show, which focused on people’s experiences at the edge of reality, is among the best loved and highest rated television productions of all time. People of a certain age will recall being mesmerized-perhaps terrified!-by a television series called “The Twilight Zone,” which ran 156 episodes from 1959 to 1964. By Douglas Rader, Jamie Collins and Edith Widder, CEO & Senior Scientist, Ocean Research & Conservation Association
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