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CONFUSING CORALS WITH CORAL REEFS, Widespread confusion between corals, coral reefs, and coral reef sediments pervasively pollutes popular press articles, and even the coral literature, as exemplified by debate on the coral list server. These three concepts need to be very carefully distinguished, which many allegedly professional coral reef scientists fail to do. With regard to the first two, the popular press is full of claims that coral reefs are "disappearing", when in fact they really mean that their corals are dying, while almost all of the reefs the dead corals built are still there. The pace of coral mortality from global warming and new diseases (threats no marine "protected" area can prevent) has now become such that we have certainly lost most of the coral in the world ALREADY, and will lose most of what is left in a few years (barring the sort of volcanic eruption that puts so much sulfur aerosols into the stratosphere that it reflects sunlight and cools the entire earth down, the sort of massive eruption like Tambora in 1815 and Toba 74,000 years ago that typically only happens every several hundreds to thousands of years, but is totally unpredictable). It is certainly true that there is almost no reef that I have seen anywhere in the world in the last few decades that does not have more (usually MUCH more) dead corals than live ones, but in fact we have lost very few coral reefs yet. That is because we can lose ALL of the corals without losing the reef itself, the solid limestone framework built up overwhelmingly by coral skeletons, which resists wave energy and so creates protected habitats within and behind it. Constant coral growth is needed to keep a reef growing or even static, and that has now failed in almost all reefs, which are now steadily losing ground (and height), but the death of the corals is an immediate catastrophe, while loss of the reef structure is usually only a slow motion disaster. So they have not yet disappeared. Physical erosion never sleeps, and is getting worse as global warming increases storm intensity and frequency. Bioerosion is greatly increasing in many places due to coastal eutrophication that provides more bacteria, plankton, and particulate organic carbon food for coral rock-boring filter-feeding organisms, while it simultaneously kills corals through algae overgrowth. But it can take decades or centuries for a totally dead reef to be bioeroded and collapse, even if there are no longer ANY living corals to repair damage and keep building new reef. Only a very small proportion of reefs have vanished completely, and those are almost entirely the shallow Acropora reef crests (the most important part of the reef for absorbing wave energy, reducing shore erosion, and providing fish habitat). The branching Acropora reefs that had more than 95-99% mortality after bleaching in Indonesia, Philippines, Maldives, Seychelles, Palau, etc. in 1998 have already been largely broken up by typhoons and cyclones, and sit as massive piles of rubble where erect reefs once stood, being gradually broken up and re-distributed by storms. The original locations of these reefs are still clear from the rubble, but their ecological function has almost completely vanished. In most cases new settlement has been minor, and is largely composed of other genera, like Porites and Pocillopora, whose ecosystem services are far inferior to Acropora. In the Caribbean the vast elkhorn and staghorn reefs that I learned to swim in as a boy have vanished entirely without trace almost everywhere (not even localized rubble is left in most of them, the hurricanes have now had time to redistribute them). One can find only the tiniest patches of dead framework standing in a handful of protected sites (for example there are a couple tiny areas of these left in Bonaire, Cozumel, the Grenadines, Cuba, and Aruba, but almost none in Jamaica). But the remaining reef framework of the massive coral understory remains, and is providing some reduced degree of shore protection and vastly inferior habitat for biodiversity, and will continue to do so for decades to perhaps a century or so, even after the head corals die completely. These are dead or dying reefs are incapable of keeping up but they are still reefs in the original navigational definition of the word (something that can rip the bottom out of your boat) even though they no longer function ecologically as coral reefs because they are no longer growing limestone structures overwhelmingly populated by hard corals. Because of all of this popular confusion it is really crucial to emphasize that corals are vastly more vulnerable than coral reefs and some form of inferior reef communities will remain long after almost all the corals have died (the badly degraded ex-coral reefs, now dominated by algae, soft corals, tunicates, and sponges overgrowing dead coral substrate, which are all that most divers and coral reef researchers now know because the real thing has become so rare most divers have never seen one). With regard to the second two, coral reefs and coral reef sediments, geologists have always been very careful to separate them, but biologists have often failed to, and this is the core of the confusion now exposed on the coral list server. Solid wave-resistant coral reef structures able to keep growing upward despite physical erosion from storms and bioerosion and rising sea level, are overwhelmingly made by living corals, the ONLY organisms that can keep growing solid limestone frameworks for decades, centuries, and millennia: http://globalcoral.org/coral_and_coral_reefs_commentary.htm Sure there is sand trapped in the interstices from other reef limestone producers like calcareous branching algae, foraminifera, mollusks, etc., and cementation by calcareous encrusting algae (usually after the reef has stopped growing because it has reached sea level). But the vast bulk of those loose limestone particles are washed out of the reef by storm waves, forming enormous piles of sediment both behind the reef in shallow water and cascading down in front of the reef into deep water. The organisms that produce these fragile or small pieces of limestone sediments (but are very minor components of the reef structure), are reef organisms that would not be there at all if the corals did not create the habitats in which they live, and they do produce far more limestone sediment than the reef framework itself. In fact if the reefs did not have their sediments almost entirely flushed out by waves the corals themselves would soon be smothered in sediments, buried in their own waste products. If we look at geological cross sections of living and fossil reefs there is far more reef sediment than coral reef framework, and something like 80% or more of the limestone produced by reefs can be sediments that do not contribute to wave-resistant construction and can wind up being moved very far away. Naturally the amount produced and the amount accumulating is a very sensitive function of the productivity and ecology of all the limestone producers, and of the precise physical forces on reefs. These factors vary incredibly from one reef to another, being a unique combination on every reef, so that data from one place is often irrelevant to another. It is bad enough when these mistakes are repeatedly made in the popular press, but far worse when they are spread by the very scientists who the press interviews.
Thomas J. Goreau, PhD President, Global Coral Reef Alliance President, Biorock International Corp. Coordinator, United Nations Commission on Sustainable Development Partnership in New Technologies for Small Island Developing States 37 Pleasant Street, Cambridge MA 02139 617-864-4226
No one can change the past, every one can change the future
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