Abstract The Hawaiian Archipelago is one of the largest and most isolated island chains in the world, and its marine ecosystems are well-studied. Research on Hawaiian mesophotic coral ecosystems (MCEs) began in the 1960s and has intensified during the past decade. In Hawai‘i, rich communities of macroalgae, corals and other invertebrates, and fishes inhabit MCEs and are associated with increased water clarity and decreasing average current strength with depth. Extensive calcified and fleshy macroalgal beds are found both in discrete patches, dense beds, and meadows over both hard and soft substrates. Several species of corals typical of shallow reefs extend to depths of ~60 m. The dominant corals below 60 m are in the genus Leptoseris, which can form extensive coral reefs spanning tens of km2. Few octocoral species inhabit shallow reefs and upper MCEs (30–70 m) but are diverse at the deepest range of MCEs (>130 m). Sponges do not represent a major structural component of MCEs. Many species of fishes occur on both shallow reefs and MCEs, but MCEs harbor more endemic species (up to 100% endemism). Several new species of macroalgae, corals and other invertebrates, and fishes have recently been documented. Over 60% of the territorial waters surrounding the archipelago are protected as the Papahānaumokuākea Marine National Monument; however, no specific protections exist for MCEs. Generally, threats affecting Hawai‘i’s shallow reefs also affect MCEs to varying degrees. MCEs may be more insulated from some threats but more vulnerable than shallow reefs to others (e.g., water clarity).

Depth range
25- 123 m

Mesophotic “mentions”
157 x (total of 7427 words)

Classification
* Focused on 'mesophotic coral ecosystem'

Fields
Biodiversity
Climate Change
Community structure
Connectivity
Ecology
Geomorphology
Management and Conservation
Molecular ecology
Oceanography
Reproduction

Focusgroups
Algae (Macro, Turf and Crustose Coralline)
Antipatharia (Black Corals)
Fishes
Octocorallia (Soft Corals)
Other invertebrates
Overall benthic (groups)
Porifera (Sponges)
Scleractinia (Hard Corals)

Locations
USA - Hawaii

Platforms
Fishing
Land-based
Manned Submersible
Rebreather
Remotely Operated Vehicle (ROV)
SCUBA (open-circuit or unspecified)