Sunlight drives life in the ocean, just as it does on land. Reefs are epicenters for converting sunlight into nutrients via photosynthesis. As you descend in the water column, light disappears, and life becomes less abundant (excluding hydrothermal vent ecosystems). However, scientists have discovered a hidden oasis for life at the bottom of the photic zone, where light just barely penetrates.

The recently dubbed ‘rariphotic’ zone spans 150m to 300m down, and amazingly, it supports life. Not just any life, though. Previously thought not sustainable due to the lack of light at these depths, an entire ‘deep reef ecosystem exists near Curacao where scientists thought the only life were deep-sea inhabitants. They have observed 4,300 specimens, with 71 newly described fish species. The fish are more closely related to modern reef fish than to deep-sea fish.

That is particularly notable because it suggests that reef fish have started moving deeper rather than deep-sea fish moving up into lighter and warmer waters. One potential hypothesis is that climate change has caused these fish to retreat from the warming waters into colder, more comfortable temperatures. Scientists also postulate that this rariphotic zone could be a missing link between reef life and deep sea life. However, this study mostly sampled from the Caribbean, and its finding should be validated in areas around the globe before the rariphotic zone becomes part of the standard model.

Managing Correspondent: Zane Wolf

Image Credit: Pim Bongaerts. Mesophotic reef system around Bunaken Island, Sulawesi.

Original Article: Below The Mesophotic – Scientific Reports

Related SITN Articles: Snapshots in ocean reef evolution and what to expect going forward

Other Popular Media: Scientists Discover a Hidden Ocean ‘Twilight Zone’ Filled with Unknown Fish – ScienceAlert; Smithsonian report reveals an unexplored underwater ‘twilight zone’ – BigThink

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