|Newly found coral, Acropora gemmifera on the Big Island D. Ward photo|
The word acropora comes from acro, or "extremity" and pora, for "with a pore." So it is not surprising that many of the corals in this group are characterized by having a single pore or corallite (skeletal cup) on the tip of each branch. This makes these corals fairly easy to recognize. Note that the "Branching Coral" in the diagram below is an Acropora - it has a polyp hole (corallite) right on the end of the branch.
|From the Coral Hub.|
|Acropora gemmifera. Madagascar. Surface detail of a plate. Charlie Veron.|
Corals in the genus Acropora are what most people in the world think of when they think of coral reefs. These are the staghorn, elkhorn and the table corals of Florida, the Caribbean, and virtually all of the Indo-Pacific. As such, I suspect that they are the most commonly photographed corals that exist.
However Hawaii is a bit different. Take a look at the images below (from Keoki Stender's Marinelifephotography.com).
Which of the common corals found in Hawaii are Acropora's?
Rice coral - note placement of polyps in closeup.
Lace and cauliflower corals: hint - note multiple polyps on tips.
Are any of these in the Acropora genus? If you answered 'No," you are correct.
Hawaii is distinctly different than the rest of the Pacific and Caribbean in this respect. Anywhere else the common corals are various types of Acroporids, but not Hawaii, and I can't tell you why that is. They have just not expanded into our waters well. They are at Johnston Atoll. French Frigate Shoals in the Northwestern Hawaiian Islands has a wonderful reef filled with them. Actually, our rice corals are fairly closely related (in a same larger family group), but other than a few true Acropora genus colonies off of Kauai and a colony off of Oahu - they just don't exist much in the main Hawaiian islands.
|Acropora gemmifera colonies on the Big Island D. Ward photo|
Check out this video link: Kona Acropora Dive, via DLNR. I have to admit that although I liked looking at the coral beds, I also want one of those propulsion units strapped to the diver's tank - very cool.
My favorite on-line resources for ID of Indo-Pacific corals are currently the Australian Institute of Marine Science coral site and Coral Hub, from which the diagram of the coral polyps and their corallites (cup) came.
AND - for the full DLNR article from their Jan 29th Facebook post (nice site by the way):
"A coral species new to the main Hawaiian Islands has been discovered in West Hawaii by a research team of the state Department of Land and Natural Resources (DLNR) Division of Aquatic Resources divers, under the leadership of senior biologist Dr. Bill Walsh.
While doing reconnaissance SCUBA dives along the Kona coast of the Island of Hawaii, the dive team came across a large number of coral colonies, which none of the researchers had ever seen before. These robust finger-like colonies didn’t even look like they were related to any other corals in the vicinity of the main islands.
After returning the next day and photographically documenting the colonies, the coral was tentatively identified as Acropora gemmifera. Not only is this the first record of Acropora gemmifera in the main Hawaiian Islands, it’s the first record of any Acropora species occurring around the island of Hawaii.
Visual identification of the coral was subsequently confirmed by genetic sequencing done by Narrissa Spies of the Richmond Lab at the Kewalo Marine Laboratory, Pacific Biomedical Research Center in Honolulu.
“The presence of these coral colonies is a significant contribution to our understanding of local reef diversity and opens up speculation about what other rare corals may be found on the reefs of Hawaii island,” Walsh said.
Several Acropora species have been identified in the Northwestern Hawaiian Islands; previously, several small colonies of the table coral Acropora cytherea have been reported from Kauai, and a single colony was recently sighted off Oahu.
The discovery of this rare species in the main Hawaiian Islands emphasizes the need for local marine and land-use conservation practices. Members of this genus have a low resistance and low tolerance to bleaching and disease, which can be made worse by pollution, overfishing, and climate change. They are also a coral species preferred by Acanthaster planci, the crown-of-thorns starfish, which is a coral predator.
Acropora gemmifera is common in shallow, tropical reef environments in the Red Sea, Australia, the Indo-Pacific, and central and western Pacific, but there are few records from the Northwestern Hawaiian Islands. It does occur at Johnston Atoll, approximately 900 miles southwest of Hawaii.
There have been no historical reports of any Acropora species occurring around the Island of Hawaii nor were any observed in more than 4,500 DAR coral reef monitoring/research dives over the past 15 years.
Typically, this species is found intertidally and subtidally from 1 to 15 meters. The colonies can vary in color from tan/brown to green, blues and even purples. The Kona population is located in waters 4 to 10 meters deep and consists of tan/brown colonies ranging from young encrusting forms to mature colonies estimated to be at least 80 years old. A total of 75 A. gemmifera colonies were found at the Kona site along a 50-meter stretch of reef.
Still images of Acropora gemmifera are available on Google plus at https://plus.google.com/101613020396360217549?hl=en#101613020396360217549/posts?hl=en