A difficult area to study and often overlooked by science, new technology is aiding its exploration, forcing researchers to re-evaluate just how much life is down there. Researchers now believe there is 10 times, maybe 100 times the volume of biomass previously thought, says Heidi Sosik, senior scientist at Woods Hole Oceanographic Institution (WHOI).
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 fear commercial fishing operations could expand in this ecosystem, and small but abundant species could end up in fish oil, used in cosmetics and dietary supplements, or fishmeal, used in aquaculture to feed species farmed for human consumption.
“There are very basic things about the twilight zone that we just don’t know,” Sosik explains, including the lifespan of some species, and how long it takes them to mature and reproduce. Without understanding lifecycles, there is no way to know how species could be fished sustainably.
“The unique challenge about working in the twilight zone is that we don’t want to disturb the animals,” says WHOI senior scientist Dana Yoerger. These creatures are sensitive to light and sound, so monitoring them means devices need to be quiet and not stir up water, and employ red lights that most animals can’t see.
Yoerger developed “Mesobot,” an autonomous robot that discretely monitors slow moving fauna. Using stereo cameras to judge a creature’s relative position (in the same way the human brain does), the robot moves with the animal at a fixed distance, allowing researchers to watch how it swims, hunts its prey, and document delicate bodily structures that would be destroyed if a physical sample were caught in a net, he explains.
Trials have lasted up to 40 minutes so far, but Yoerger hopes to eventually follow a target over a 24-hour period. “Ultimately, we’d like Mesobot to think like a human scientific explorer, seeking out the most unusual animals and observe their behavior for long periods,” he says.
Sosik explains that scientists are attempting not only to build out knowledge of the twilight zone, but how it fits in within the wider ocean. “Whales and sharks — everything we’re familiar with, the charismatic organisms of the ocean — the more we learn about them, the more it seems that they depend on interacting with the twilight zone,” she says.
That sinking feeling
Researchers have also come to the conclusion that another species might also be reliant on the twilight zone: humans.
Marine snow is consumed by sea life including salps, gelatinous organisms living in both the surface ocean and the twilight zone and whose role may have been historically underappreciated, says Sosik. Salps are capable of clearing “huge volumes of water,” she explains, in turn excreting dense fecal pellets that sink fast into the deep ocean.
“In the past, humans have found living resources in the ocean and just went full bore over-exploiting them,” Sosik says, “and in hindsight realized that we should have been more informed and taken a more mindful approach. With the twilight zone we have that opportunity.”
“We have this amazing opportunity to bring together basic science and curiosity driven science, and try to generate solutions for the big challenges that humans face in interacting with our planet and our ocean ecosystems,” says Sosik.