#stylaster

Spotted seahorse (Hippocamopus kuda) among branching lace coral (Stylaster spp.) and sea fan (Melithaea spp.)

RARIPHOTIC: Meet what lies beyond middle light coral reefs. 

Researchers have realized out a new zone, found next to corals reefs in some areas worldwide. Beneath coral reefs, lies a middle light-zone of reefs, often called mesophitic, which usually starts at depths of about 40 m, but beyond this zone, there is a unexplored area, deeper and darker, this zones is called rariphotic, or scarce light zone. A zone with unique biodiversity. 

This newly recognized rariphotic zone ranges from 130 m to at least 310 m, too deep for professional SCUBA, for this reason, it is necessary to use submersibles and ROVs to explore these regions. Coral fauna consists entirely of non-zooxanthelate corals, (wich are no colorful and no depend on sunlight to survive as most corals do), non reef-forming hard corals, along with gorgonians. These ecosystems harbors a unique reef-fish fauna, dominated by species that are related to shallow-water families rather than deep-sea fishes.  

- The lace coral Stylaster, gorgonian Nicella, and Yellow-spotted Golden Bass  Liopropoma olneyi , part of the rariphotic fauna of Curaçao, depth 112–229 m). Photo by L. Tornabene

Researchers state rariphotic as part of a depth continuum of discrete faunal zones of tropical reef fishes, and perhaps of reef ecosystems in general, all of which warrant further study in light of global declines of shallow reefs. 

Rariphotic assemblages have been identified off Hawaii, the Marshall Islands and around Easter Island in the Pacific, as well as in the Gulf of Mexico and Curaçao.  

Also, researchers take a step, naming all three well-defined reef zones: the newly recognized and named rariphotic, the mesophotic, and the newly named altiphotic or high light, where is shallow water reefs are placed. It is crazy, but altiphotic didn’t have a name before.

Photo:  unnamed species of sand perch. Photo by Luiz Rocha.