Who ever said the ocean keeps its secrets in darkness? In the top layer of the twilight zone in Guam, 300 feet deep in the ocean, scientists have just revealed a wealth of bizarre creatures in such vibrant colors that they defy all former knowledge about reefs in the deep ocean. In this area, where light barely breaks through as a glow, nothing much has ever ventured because it simply can’t be reached through means other than extremely advanced diving equipment and hard-earned observation.
The group, led by the California Academy of Sciences in collaboration with the University of Guam and others, brought back 13 autonomous reef monitoring structures, or ARMS, that have been deployed in these depths for more than eight years. Every ARMS is a vertical stack of one-foot-square plastic plates made from PVC and is essentially a mini-apartment complex in shape, designed like an artificial reef a coral reef hotel in form, serving as a home for corals, sponges, worms, crabs, and fish that populate it in time. These machines gather far more biodiversity in one go than a human exploration ever can, storing not only samples of organisms in their waters but also samples of their DNA from previous inhabitants. As Luiz Rocha, ichthyology curator at the California Academy of Sciences, explained, “are essentially small underwater hotels that coral reef organisms colonize over time.”
To explore these ARMS, extremely specialized tech diving gear was required. Conventional scuba diving apparatus merely goes as far as 130 feet, where the air in the scuba diving tank is no longer safe to breathe. They used closed rebreathe systems with gas mixes, and the only way to avoid nitrogen narcosis and oxygen toxicity was to breathe a blend mostly of helium. While more hazardous, with the possibility of lethal gas mixes, it recirculates the gases, allowing deeper bottom times. However, it also takes six hours to ascend from 500 feet, while only a 10-minute bottom time at that same depth. Rocha’s November forays only permitted the team to stay for a mere half-hour of activity to commence the laborious ascent.
The payoff was stunning. Within two weeks of analysis, researchers identified 2,000 species, of which 100 had never been documented in Guam and at least another 20 are believed to be new to science. Among the specimens are what may be a new species of cardinal fish, an orange-clawed crab that has never existed in Guam before, and a sea slug that sports yellow and pink spots. Rocha’s favorite find was a hermit crab that has evolved to live in clam shells as opposed to other snails. The DNA analysis promises further revelations of what other secrets lie hidden.
But in the midst of such wonder, the team found evidence of human effects. Deep reefs, considered a refuge from the impacts of climate change, are now showing signs of warming at a similar rate to shallow areas. Evidence from the ARMS exists to suggest even in such depths, the effects of warming are being realized by the coral. Indeed, regional climate records show sea surface temperatures in the South-West Pacific have risen three times faster than the global average, and marine heat waves have doubled in frequency since 1980.
Pollution is another concern. A world-wide study of coral reefs has shown that the greatest quantity of plastics is in the mesophotic zone, with 88% of the macroplastics associated with fishing gear like ropes and fishing nets. Even in the most secluded places, human trash has been observed, which either gets transported by waves or by fishing activity. As Rocha observed, “We are almost always the first humans to set eyes on these deeper reefs, and yet we see human-produced trash on every dive.”
The ecological cost is high. Deep reef ecosystems consist of distinct species that do not migrate from shallower reefs. Thus, species that perish on deep reefs cannot simply move to higher waters. Deep reefs face the same dangers as shallower species: overfishing, the devastation wrought by storms, and non-native species. However, they do not receive the protection accorded marine reserves. Scientists emphasize that preserving these ecosystems needs the implementation of protection over greater depths and the establishment of biodegradable materials. This trip to Guam is just the start.
Over the coming two years, the group intends to return 76 ARMS to deep reefs in the Pacific region, including Palau, French Polynesia, and the Marshall Islands. These discoveries and findings will be shared with the global scientific community. For the interested enthusiast and the passionate advocate of the natural world combined, expeditions into the twilight zone are very much an exploration they are a race against time to learn and protect a hidden world before it becomes a different place entirely.
