Species composition, habitat preferences, and community structure of zooxanthellate scleractinian corals in the upper mesophotic zone (UMZ, 30–60 m depth) of the central Indo-West Pacific (IWP) are described. A total of 340 species were recorded from 287 sites from the Andaman Sea across the Coral Triangle to Micronesia and Solomon Islands. This represents almost half of the reef-building coral species present in the central IWP, yet is far from complete. Species were categorized as either UMZ specialists (9 spp.), depth generalists (57 spp.), or with habitat preferences for the lower reef slope (63 spp.), mid-lower slope (172 spp.), or shallow slope (39 spp.). The five most common species in the UMZ were depth generalists (massive Porites spp.) or species that more commonly occur on mid-lower or lower reef slopes above the UMZ, such as Pachyseris speciosa, Acropora granulosa, Oxypora lacera, and Seriatopora hystrix. Only one of the ten most common corals, Acropora elegans, is an UMZ specialist. Percentages of species occurring in the UMZ ranged widely among genera, being highest in Euphyllia (100%), Leptoseris (92%), and Cycloseris (90%) and lower for speciose IWP genera Acropora (47%), Montipora (53%), and Porites (46%). Five broad, mid-lower slope coral communities extended into the UMZ, where seven coral assemblages were defined, each with greater or lesser biogeographic fidelity. We assess our findings in relation to the life histories of the species present and place these in the broader context of the “deep reef refugia” hypothesis.

Depth range
2- 50 m

Mesophotic “mentions”
48 x (total of 9896 words)

Classification
* Presents original data
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Fields
Community structure
Ecology

Focusgroups
Scleractinia (Hard Corals)

Locations
Australia - Great Barrier Reef
Australia - Northern Australia
Brunei
Indonesia
Micronesia - Caroline Islands (Pohnpei)
Papua New Guinea
Philippines
Republic of Palau
Solomon Islands

Platforms
SCUBA (open-circuit or unspecified)