Mesophotic coral ecosystems (Figure 1) are the deeper extensions of shallow-water coral reefs, occurring at the dimly lit depths from ~30–40 m down to 150 m in (sub)tropical regions of the world. The distinct environmental conditions at these depths have led to unique biological communities that can be found nowhere else on Earth, yet they remain vastly understudied as they are beyond the conventional limits of scientific SCUBA diving. Although representing the deeper and darker section of the ocean’s surface waters, the presence of photosynthetic scleractinian corals is generally considered a defining feature of mesophotic ecosystems. Nonetheless, the benthic community is often dominated by other organisms such as gorgonians and other octocorals (Octocorallia), black corals (Antipatharia), sponges (Porifera) and algae. The boundaries of the mesophotic zone are rather open- ended, with the upper boundary representing the start of a transition to the unique communities of marine life found at greater depths. The lower boundary roughly corresponds to the maximum depth of photosynthetic scleractinian corals. Colloquially, these habitats have been referred to as the ‘coral reef twilight zone’, due to their low-light conditions and the fact that they are poorly studied.

Depth range
30- 150 m

Mesophotic “mentions”
35 x (total of 1061 words)

Classification
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Fields
Ecology
Management and Conservation
Methods and Technology

Focusgroups
Algae (Macro, Turf and Crustose Coralline)
Antipatharia (Black Corals)
Octocorallia (Soft Corals)
Scleractinia (Hard Corals)

Platforms
Manned Submersible
Rebreather