New species of fish are being discovered in what’s being referred to as the Rariphotic zone. Deep reef ecosystems could still be explored much more.
It’s always been there, but a layer of the ocean is so distinct from the waters above and below it that it needed its own category.
Scientists have just defined the newly named rariphotic zone, a layer of ocean between depths of 130 and 300 metres (400 and 1,000 feet) – a low-light or “twilight zone” in deeper reef regions.
It sits just below the mesophotic zone, between 40 and 150 metres (131 and 492 feet), where medium light penetrates – the optimal waters for tropical coral reefs. And it’s teeming with previously unknown fish – a whole newly discovered ecosystem.
These fish are closely related to reef fish, which researchers didn’t think could live below the mesophotic.
This has led to a hypothesis that the new rariphotic zone may be a refuge for shallower reef fishes seeking respite from the warming waters and coral deterioration caused by climate change.
There’s a lot we don’t know about the ocean, simply because it’s so difficult for us to access. It was only thanks to advances in submersible technology that marine scientists have been able to explore down below the reef off the coast of Curaçao.
“It’s estimated that 95 percent of the livable space on our planet is in the ocean, yet only a fraction of that space has been explored,” said study lead author Carole Baldwin of the NMNH.
“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 reefs.”