A team of researchers was able to identify a “twilight zone” hidden in the ocean several hundred meters deep, filled with unknown fish. The details of the study were published in the journal Scientific Reports.
A team of marine biologists announced that they have discovered a new ocean life zone — the rariphotic — between 130 and 309 meters below the surface and with very little light. You will find it just below a previously defined reef area — the mesophotic — which extends from about 40 meters to 150 meters deep. This new area could serve as a refuge for reef fish seeking to free themselves from the warming of surface waters, or wishing to escape the deterioration of their environment.
Many researchers question whether deeper reef zones, sometimes known as the “coral reef twilight zone”, can serve as refuges for organisms. While researchers at the Smithsonian Institution (USA) were trying to answer this question, it became clear to them that scientists had only scratched the surface in terms of understanding fish biodiversity reef.
“It’s estimated that 95% of our planet’s living space is in the ocean,” says Carole Baldwin, curator at the Smithsonian National Museum of Natural History and author of the study. “However, only a fraction of this space has been explored. That’s understandable for areas that are thousands of miles offshore and miles deep. But tropical deep reefs are just below popular, highly studied shallow reefs – essentially our own backyards. And tropical deep reefs are not barren landscapes on the deep ocean floor: they are highly diverse ecosystems that warrant further study. We hope that by naming the deep-reef rariphotic zone, we’ll draw attention to the need to continue to explore deep reef.”
The authors defined this new area based on observations of approximately 4,500 fish representing 71 species for approximately 80 submersible dives up to 309 meters deep. Exploring a zone of deep reefs of only 0.2 square kilometers, researchers have also discovered six new genera and about 30 new species of fish and invertebrates.
Most of these fish not only resemble shallow reef fish, but are also related to them rather than true deep-water fish — which belong to very different branches of the evolutionary tree. This new area could ultimately serve as a refuge for reef fish seeking to escape the warming of shallow waters and the deterioration of corals caused by climate change.