[Coral-List] deep "coral oases"

Alina Szmant alina at cisme-instruments.com
Wed Sep 16 12:04:24 UTC 2020

Hi Doug:

Well done. This could have been right out of the introductory lecture from my coral reef ecology course, which I taught for almost 30 years! I especially like that you clarify the 'shallow enough to be hit by a boat' part (most REEFS around the world are made up of non-coral rocks, not coral limestone), the term bioherm for deeper accumulations of biogenic skeletal matter (algae such as Halimeda form bioherms, e.g. Marquesas between Key West and Dry Tortugas; many places along the Great Barrier Reef in deep passes between coral reefs), and that a true coral reef needs to be accretional in nature not just scattered corals (i.e. net calcification > 1; limestone deposition > bioerosion). Some places that could form coral reefs don't because of the high rates of bioerosion (e.g. some upwelling zones).

It is important that the growth history of any particular structure being considered for designation as a coral reef be carefully considered. I recall an article from years ago where a new volcanic outcrop was quickly colonized by corals. This could have been a founding event for a coral reef, but just high coral cover does not equal a coral reef. 



CISME IS NOW SOLD BY QUBIT SYSTEMS; https://qubitbiology.com/cisme/

Dr. Alina M. Szmant, CEO
CISME Instruments LLC
210 Braxlo Lane,
Wilmington NC 28409 USA
AAUS Scientific Diving Lifetime Achievement Awardee
cell: 910-200-3913
Website:  www.cisme-instruments.com

Videos:  CISME Promotional Video 5:43 min   https://www.youtube.com/watch?v=VAYeR9qX71A&t=6s
CISME Short version Demo Video 3:00 min  https://www.youtube.com/watch?v=Fa4SqS7yC08
CISME Cucalorus 10x10 Sketch   4:03 min  https://youtu.be/QCo3oixsDVA

-----Original Message-----
From: Coral-List <coral-list-bounces at coral.aoml.noaa.gov> On Behalf Of Douglas Fenner via Coral-List
Sent: Tuesday, September 15, 2020 6:13 PM
To: coral list <coral-list at coral.aoml.noaa.gov>
Subject: [Coral-List] deep "coral oases"

Deep beneath the high seas, researchers find rich coral oases


Notice the title says "coral oases" not "coral reefs" and does not say "hard corals," but does say "rich."

There are a number of distinctions that some popular articles such as this one tend to gloss over, and they tend to talk in ways that may lead people to assume that these places are similar to shallow tropical coral reefs, but that comparison is strained at best.  So, the original meaning of the word "reef" is a structure that is near the water surface that a boat can hit.  These are not reefs, they are in deep water.  Second, a coral reef would be a reef built by coral.  There are deep sea structures built by coral, some a few hundred feet tall and can be a mile or more long.  The most famous of which are in the fjords of Norway, but others are scattered around the world.  They are better termed "bioherms" since they are constructed by organisms, but don't get close to the surface.  People sometimes talk about their high diversity, but usually the construction is built by only one species of coral, while many shallow tropical coral reefs have hundreds of species of corals on them.  Plus, in the whole world, there are only a few species of coral that can build deep water constructions, maybe less than 10, and most or all are thin branching.  I suspect, but don't know for a fact, that the diversity of other organisms inhabiting them are also much lower than most shallow water tropical coral reefs.  But much of what they are probably talking about here are "coral communities" or ecosystems, as they are not constructional, there is no geological structure built by them  The photograph for this article shows many gorgonians, or octocorals, which can also be called soft corals, and which do not build calcium structures (surprisingly, there are non-gorgonian soft corals on shallow tropical coral reefs that add to the geological structure, in a few places their contribution can actually be greater to the construction than "hard corals" like Scleractinia).  Looks like there is at least one that may be a black coral, a group which also does not build coral reefs.  Among the hard corals, most are "scleractinia".  On shallow water tropical coral reefs, most scleractinia are zooxantellate, colonial and many large, and most contribute to building the geological structure, which can be up to at least 1.6 km (one mile) thick, depending on how long it has been building.  Scleractinian corals do certainly live in deep and/or cold water, and there are about as many species known that do that as on coral reefs.  They are all azooxanthellate, most are solitary and small, and by far most of them do not build any structures other than their own skeleton.  Often they are scattered.  That doesn't mean that they aren't interesting or important, just different.
     So deep water or cold water coral bioherms are interesting, part of our world, as are deep water hard and soft coral communities.  They are generally less studied because they are much more difficult and expensive to access and study, and they are not restricted to warm, shallow water.
      I don't study them, I'm not an expert on them, so those that are, please correct me if I'm wrong about this.
     Cheers, Doug

Douglas Fenner
Lynker Technologies, LLC, Contractor
NOAA Fisheries Service
Pacific Islands Regional Office
PO Box 7390
Pago Pago, American Samoa 96799  USA

The toxic effects of air pollution are so bad that moving from fossil fuels to clean energy would pay for itself in health-care savings and productivity gains <https://nature.us17.list-manage.com/track/click?u=2c6057c528fdc6f73fa196d9d&id=c9f70ba54f&e=190a62d266>
even if climate change didn’t exist.  In the US alone, decarbonization would save 1.4 MILLION lives in the US alone.  And save $700 Billion a year.

"mitigating climate change is the critical wedge to set coral reefs on a recovery trajectory"  Duarte et al 2020 Rebuilding marine life Nature

"Already, more people die  <http://www.nws.noaa.gov/om/hazstats.shtml>from
heat-related causes in the U.S. than from all other extreme weather events."

Coral-List mailing list
Coral-List at coral.aoml.noaa.gov

More information about the Coral-List mailing list