The Ocean Twilight Zone, officially called the Middle Ocean Zone, exists about 2001,000 meters below the surface. There are various species inhabited here, from monkfish to vampire squid, to fairy light siphon, here is a place full of weirdness. In the dark, the eyes are small and the teeth are large; many species are transparent, and many are bioluminescent. And in the dark, the dominant creature, the ubiquitous pricked mouth, is smaller than a human’s little finger.
A field that is difficult to study and often overlooked by science. New technologies are helping to explore it, forcing researchers to reassess how many lives there are. Heidi Sosik, a senior scientist at the Woods Hole Oceanographic Institution (WHOI), said that researchers now believe that biomass is 10 times as much as previously thought, perhaps 100 times as much as before.
With each answer, more questions. “What we know now is how much we don’t know,” she says.
Now this quest for knowledge has become a race against time.
Some scientists are concerned that commercial fishing operations may expand in this ecosystem, with small, abundant species eventually being converted to fish oil, used in cosmetics and dietary supplements, or fishmeal, used in aquaculture to feed agriculture for human consumption.
“There are some very basic things that we don’t know about the twilight zone,” explained Sosik, including the lifespan of some species and how long they take to mature and reproduce. If you don’t understand the life cycle, you won’t be able to know how to fish for species sustainably.
For a long time, technology has been an indispensable friend of those who study Twilight. But it is not always advanced or detailed enough to provide an accurate description of the area. Take the bristly mouth as an example. The dense formations of these small fish were once mistaken for the seabed by sonar equipment. Now, researchers have the tools to estimate that there may be as many as trillions (1,000 trillion) of bristled mouths in the ocean, making it the most abundant vertebrate on earth.
“The unique challenge of working in the twilight zone is that we don’t want to disturb the animals,” said Dana Yoerger, WHOI Chief Scientist. These creatures are sensitive to light and sound, so monitoring them means that the equipment must be quiet and cannot disturb the water surface, and use red lights that most animals cannot see.
So far, the test has lasted 40 minutes, but Yoerger hopes to eventually be able to track the target within 24 hours. “Ultimately, we hope that Mesobot will think like a human scientific explorer, looking for the most unusual animals and observing their behavior for a long time,” he said.
In July, WHOI researchers will set sail for the first phase of research to map the twilight zone near the continental shelf of the northeastern United States. A team will deploy a network of sensors capable of tracking drifting research robots called “minions” and tagged specimens from the upper waters entering the twilight zone, covering an area of approximately 1 million square kilometers (386,000 square miles).
Sosik explained that scientists are not only trying to understand the twilight zone, but also to understand how it adapts to the wider ocean. “Whales and sharks are all we know. The more we learn about the enchanting creatures of the ocean, the more they seem to depend on their interaction with the twilight zone,” he said.