Scientists are reminded of how little they truly know by the ocean. In November, a team from the California Academy of Sciences resurfaced off the coast of Guam with something amazing: thousands of specimens that had been extracted from depths that most people would never see. These specimens included at least 20 species that, in terms of science, had never existed before.
Stacks of PVC plates that have been bolted together and lowered to the seafloor are the story’s almost unremarkable beginning rather than a spectacular discovery. These structures, known as ARMS, or Autonomous Reef Monitoring Structures, serve as artificial apartment buildings for marine life. In 2018, scientists left 13 of them in Guam’s reefs at depths of up to 100 meters. Sea creatures moved in covertly for eight years while the world dealt with its numerous distractions.
When Luiz Rocha and his group eventually went back to get them, they discovered something shocking about those plates. A total of about 2,000 specimens. One hundred species that have never been found in this region of the Pacific. And at least 20 that seem to be completely new—beings that had been living in the shadows, unidentified and unnamed, for a very long time before any scientist bothered to look.
According to Rocha, the ARMS are “small underwater hotels that coral reef organisms colonize over time.” That’s an exact way of putting it. The fact that no one knows what’s inside these ecosystems until they’re actually opened up is less precise, which is what makes this work truly exciting rather than merely procedurally interesting. Before anything is confirmed, DNA analysis will be necessary for some of the specimens, including what researchers believe may be a new species of cardinalfish. After that work is completed, Rocha has already suggested that the total number of new species could increase significantly.
It’s not easy to reach these depths. The twilight zone is located in an awkward middle area, between 55 and 100 meters below the surface. Standard scuba divers can only stay there for a few minutes before being forced to return due to the risk of nitrogen narcosis and decompression. However, the robotic vehicles typically used for deep-sea research are not drawn to it because it is too shallow. This zone has been strangely ignored for years due to that gap, which could be the reason why so much life has been left undisturbed.
The stories of these dives contain a detail that is difficult to refute. Tiny pink fish, no bigger than a thumbnail, were swimming in wild circles when the ARMS were raised to the surface, experiencing sunlight for the first time in their lives. It’s not exactly a dramatic picture. However, it has some weight. These creatures had only ever lived in a small area of chilly, dark water, but all of a sudden they were in an unfamiliar place. That might be the closest thing marine biology has to a first contact moment.
There is also an uncomfortable finding associated with the discovery. The twilight zone, which was previously thought to be immune to surface-level climate effects, is already experiencing warming, according to temperature sensors built into the ARMS. That somewhat alters the picture. There is no protective bubble surrounding these reefs and their unidentified inhabitants. At a depth where monitoring has hardly started, they are subject to the same stresses that affect shallower ecosystems.
The two-year project to recover 76 ARMS from deep Pacific reefs throughout the region is just getting started. More specimens, more analysis, and probably more species that science hasn’t yet named are all implied by this. The number of them is still unknown. However, the preliminary results from Guam indicate that the answer is: many more than anyone anticipated.
