Reefs in peril
Reefs in peril
Proximal causes of decline in health of coral reefs hot buttons for peril part of BIOLOGY OF CARIBBEAN CORAL REEFS overfishing/reef collecting on Caribbean coral reefs disease on Caribbean coral reefs SCUBA/snorkeling recreation on Caribbean coral reefs future of Caribbean coral reefs pollution on Caribbean coral reefs eutrophication of Caribbean coral reefs
There are several major proximal causes for reef decline. The topic of future of reefs is dealt with here, while other topics are accessible via the "hot" buttons to the Right.
hot button for bleaching part of Biology of Caribbean Coral Reefs
title button for Future of Reefs section of BIOLOGY OF CARIBBEAN CORAL REEFS

Future of reefs


Some of the scientific papers cited in this section on Future of Reefs are already out of date. Supposed legally binding and universal agreement reached at the Paris Climate Conference in 2015 to keep global warming below 2oC has led to little mitigating actions on the part of the major carbon-polluting countries participating in the Conference. Closer to home in Canada, despite promises in 2016 to address the issue the government has been notably inactive and the economy mostly continues with "business as usual". Global air temperatures are estimated to have already risen by 0.5-1.0oC relative to pre-industrial times, and this trend now seems irreversible. It may have been coincidence that 2oC was set as the global goal, but this is the ocean temperature above which many coral reefs will die. In fact, a few localised incidents of sea-temperature rise of this magnitude have already occurred in coral-reef areas, such as the Great Barrier Reef, leading to massive die-off of corals, and this is sure to worsen. Of several proposals to limit CO2 release into the atmosphere, carbon taxation and cap-and-trade seem to be the most talked about, with the former being the most popular and the one now being implemented in some provinces of Canada and elsewhere in the world. However, unless the monies gained can be directed into viable (honest and workable) mitigation programmes, all that carbon taxation will do is pass the burden of carbon-emission costs onto the taxpayer with no penalty or reduced output forced onto those responsible. An example of this kind of thinking is the recent bill (November 2018) introduced in the U.S. House of Representatives to tax emissions and return the monies to the citizens. How would this help to curb emissions? In the end, we may find that carbon-sequestration is the only solution, and this would be a colossal task even if it were possible. It is the"terra-forming" of science-fiction.

At the Climate Summit in Poland (2018), the U.N. Secretary General warned, "Even as we witness devastating climate impacts causing havoc across the world, we are stil not doing enough, nor moving fast enough, to prevent irreversible and catastrophic climate disruption". At this same meeting, the well-known British naturalist David Attenborough remarked ominously that the "collapse of our civilizations and the extinction of much of the natural world is on the horizons". Whether we just sit back and watch, or engage the problem head-on, life on this world is changing in ways not dreamed of in its entire history.


What is the future of the world’s coral reefs? A review paper published in 2003 in SCIENCE magazine states that 30% of the world’s reefs are seriously damaged; that is, degraded beyond recognition. Another 60% are in a critical state and will be gone by 2030. According to the 17 international experts on coral-reef biology and conservation who authored the paper there are no pristine reefs remaining in the world. In their view the next several decades will see increases in carbon-dioxide content of the atmosphere and associated temperature rise in the oceans that exceed conditions under which coral reefs have thrived over the past 500 million years. Hoegh-Guldberg et al. 2007 Science 318: 1737; photographs courtesy Ove Hoegh-Guldberg, Brisbane.

NOTE when this paper was published, the Great Barrier Reef in Australia was categorised as "stable". Now, 2 decades later and based on recent survey data, scientists at GBRMPA (Great Barrier Reef Marine Park Authority) would likely reclassify the Reef's status as "threatened", some areas seriously

Below: photographs showing how reefs of the Great Barrier Reef might look under two projected scenarios for the year 2100.
The most conservative estimate of CO2 emission is shown in the middle photo) and the least conservative estimate in the right-hand photo

photographs used of examples of how coral reefs may look in future under different carbon-dioxide enrichment scenarios


past and predicted seawater temperatures and their effects on coral reefs“Is it time to give up?” is the title of a paper which, among other things, stresses that rising sea temperatures, and rising atmospheric and ocean-surface carbon-dioxide levels (these reduce the availability of carbonates for skeleton production by corals) make future prospects for reef survival so poor that "business as usual" is no longer an appropriate strategy.  The 1960 baseline gives a reference point. Collapse of coral-reef ecosystems may begin when sea temperatures rise only 2oC above this baseline. Buddemeier 2001 Bull Mar Sci 69: 317.

NOTE when considering "carbon-footprint" costs for travel, the focus is usually on automobile emissions, but most airlines now provide other options. Greenhouse-gas emission (presumably mostly carbon dioxide) for a single person flying cross-continent in North America on a commercial jet airplane can be as much as 0.7 tonnes. As an example of what airlines are offering in mitigation, Air Canada suggests that the carbon-offsite price for this can be met by redeeming several thousand travel points. How this would work is roughly as follows: the equivalent cash for these points (perhaps $40 Can) is sent to an offset management company for support of various carbon-offset programmes, including such things as methane and carbon-dioxide recapture, development of more efficient cooking stoves, installation of ground-source heat pumps, and so on. What Air Canada in this instance gets in return are offset credits (possibly for use for taxation purposes). The success of this and similar carbon-offset programmes has yet to be assessed, but the idea is good. Note that anthropogenic causes are not the only source of carbon dioxide; volcanoes and forest fires add their inputs, and peat bogs and ruminants such as cattle contribute enormously

Analysis of data from 65 separate studies at 263 sites Caribbean-wide shows that there has been an 80% decline in coral cover over the past 3 decades (see graph). Major agents of mortality include white-band disease of staghorn and elkhorn corals, hurricanes, and effects relating broadly to increased numbers of humans, including overfishing, sedimentation, eutrophication, and habitat destruction. Regionally, several areas showed signs of recovery in the 1990s (Florida and Jamaica), or at least reduced rates of loss (US Virgin Islands and Puerto Rico), but rates of decline have generally increased elsewhere (Leeward Islands, Netherlands Antilles, and northern Central America regions). Gardner et al. 2003 Science 301: 958. reef degradation from 1977-2001 Caribbean-wide
a Caribbean reef in the 1970s
simulation of a degraded reef
Same reef in 2015 with simulated 80% loss of coral cover, and associated loss of fishes, sponges, and gorgonians. Note algal overgrowth

soft corals on the Great Barrier ReefHabitat degradation associated with overuse and misuse of reefs can lead to so-called "alternate states", where reefs can become dominated by algae or by small, short-lived “weedy” soft corals.  Because these latter species have limited dispersal potential the long-term risk is that reefs may become dominated by genetically isolated clusters of in-breeding organisms. The extent to which such states are stable or reversible is pooly known. Knowlton 2001 Proc Nat Acad Sci 98: 5419.




Weed-like soft corals dominate a polluted
inshore reef in Queensland, Australia


histogram template showing potential functional groups based on diet of Caribbean reef fishes
Conservationist generally believe that attention should focus principally on biodiversity “hot-spots”, that is, those with high species richness, as areas most important to protect.  This is certainly true, but scientists have noted that “cool spots”, that is, areas of low species richness or low species diversity, may be even more vulnerable because of what is termed their low functional redundancyBellwood et al. 2004 Nature 429: 827.

histogram showing allocation of Caribbean reef fishes into functional groups based on dietSo, what does this mean? Let's consider it from the standpoint of diets of reef fishes. First, examine the depiction on the Left. The axes indicate numbers of species in 6 "functional groups" based on diet. The grouping could be done on any feature, one example being habitat, but diet is a good one to start with.

Now imagine that the cluster of fishes shown above the graph represents all Caribbean reef fishes. When these are sorted into their respective functional groups, the result is as shown in the histogram on the Right. The scientists who did the study sorted the fishes into more finely scaled groups, but this gives the general idea.

Now let's see how a similar sorting of fishes in the Great Barrier Reef would compare with the Caribbean data (see graph on Right). With only 28% of the total fish species of the Great Barrier Reef, the Caribbean area is a comparatively "cool spot", and many functional groups are poorly represented. For example, loss of just a few species of zooplankton-eating fishes from Caribbean waters would effectively decimate this functional group and have enormous ecosystem-wide ramifications. A similar absolute loss in species in the Great Barrier Reef would have much less relative impact because of greater "functional redundancy"; that is, there are more similarly functioning fishes to fill any gaps. The same is true for other functional groups.

photograph of staghorn coral
Caribbean staghorn Acropora cervicornis coral (above) and elkhorn A. palmata coral (on Right) were once so abundant that they were designated as "zones", and for many years these were valid entities in reef-biology literature. In 1999 both species were added to the Candidate Species List of the U.S. Endangered Species Act
Caribbean corals, with only 14% of the species diversity of the Great Barrier Reef, have similarly low functional redundancy. For example, there is only one species of staghorn coral in the Caribbean versus 15-20 in the Great Barrier Reef, and only one species of tall table-like coral in the Caribbean versus dozens of such species in the GBR. In many areas of the Caribbean both species are now lost, along with their provision of unique 3-dimensional habitats for fishes and invertebrates.
photograph of elkhorn coral Acropora palmata
Apart from serious ecological ramifications from loss of large corals and other large species such as manatees, sharks, and turtles, there is a danger that future generations of divers and researchers will never see them in even shades of their former abundance, and that new "shifting baselines" of reef biodiversity will be accepted as the norm

No-one is prepared to throw in the towel just yet. In addition to increased focus on some of the more traditional approaches to save the reefs as discussed above, there are some exciting and innovative ideas coming from coral-reef researchers the world over. These include:

1. Increasing hybrid vigour This occurs in organisms from crosses between strains, breeds, races, and even species. Hybrid offspring can grow faster (e.g., rice), reach larger size (corn), be more reproductive (poultry), and be generally more fit. At the Australian Institute for Marine Sciences in Townsville, scientists have cross-bred different species of staghorn corals Acropora, and interbred the same species from different localities (geographic young cultured coral Acropora cervicornis ready for outplantingstrains), and produced varietals with enhanced tolerances for warmer water (see photo on Right). In the Florida Keys, pillar corals are becoming increasingly rare, and now exist in only 100 or so scattered sites. If male and female colonies are too widely separated the chances for natural recruitment become vanishingly small, especially if breeding is just a yearly occurrence. In efforts to resurrect threatened coral species, such as staghorn coral Acropora cervicornis, researchers at the Florida Aquarium Center for Conservation conduct breeding experiments involving manipulation of light cycle and temperature to disrupt normal patterns of sperm and egg release. Resulting cross-bred varieties have greater vigour and resiliance, and show great promise for outplanting. Photo of juvenile staghorn coral Acropora cervicornis courtesy Keri O’Neil, Manager, Coral Nursery, Florida Aquarium Center for Conservation.

NOTE natural vigour in hybrids may be suppressed if certain traits are selected for, such as occurs in breeding programmes. A new breed of dogs Canis domesticus can be created within just a few generations, but not without excessive inbreeding (backcrosses to parents, or between siblings) and fairly drastic culling to emphasise desirable traits (size, leg length, coat colour, temperament, etc.), and this can potentially lead to loss in vigour. The more inbreeding that takes place, the greater the gene pool shrinks. The most “vigorous” dog is still likely to be a mutt (mongrel). A mule is a cross between different species, specifically, a female horse and a male donkey. However, while mule offspring are “vigorous” in terms of strength and surefooted-ness, they are less “fit” because they are sterile. Why this last happens in mules is not well understood

Juvenile staghorn coral Acropora cervicornis recruited
to a ceramic tile and ready for outplanting

2. Related to the above is selective breeding to produce more hardy corals.
This technically simple approach involves repetitively breeding corals that have been subjected to heat stress and selecting the most temperature-tolerant offspring. Trials in Australia and Hawai’i show that after several generations the offspring of corals raised in this way are more heat tolerant than ones produced through random mating. Success of such programmes will require massive culture facilities for many coral species with release of both spat and competent larvae, and will involve huge outlays of time and money. In broader perspective, such an approach is really a compressed version of evolution, where natural selection would favour survival of offspring that are most fit to withstand the seawater-warming effect of climate change. If climate change were occuring over geological time-spans as has happened in the past, rather than decade-spans predicted from current photograph of coral colonies Acropora spp. ready for outplantinganthropogenic causes, then we might anticipate a slow migration of coral reefs towards the poles. At present, without major intervention, the world’s reefs sit in a giant pot being heated over a relatively short space of time to lethal simmering, possibly too quickly for natural selective processes to occur. Photo by Neal Cantin and AIMS.

NOTE the extent to which such selection has “naturally” operated on corals in different world reefs is illustrated by a senior scientist at the Red Sea Research Center in Saudi Arabia, who states that while Red Sea corals are perfectly adapted to conditions of high heat and salinity stress, were species from the Great Barrier Reef to be transferred to these same conditions, 99% would die


2yr-old hybrids of different Acropora coral species. These
offspring have been “artificially” selected for their tolerance
to the type of prolonged heat stress predicted for coral
reefs in the future (hence, the term “Assisted Evolution”)

3. Directed inheritance of environmental resistance.
If corals and their symbiotic zooxanthellae survive after one or more warming events they may become acclimated over relatively short term, such that future exposures to heat stress can be tolerated. Indeed, research at the Hawai’i Institute for Marine Biology shows that such resiiance can be passed on to their offspring of corals in a process known as intergenerational epigenesis. The “epi” part of the word refers to change occurring through physiological adaptation rather than genetic modification. A similar approach is taken by scientists at Central Queensland University and AIMS in Australia who have cultured many successive generations of symbiotic zooxanthellae. Repetitive selective culling of each lot has led to enhanced resistance of the symbionts to heat stress and acidification. The researchers also find that increased tolerance gained by corals Acropora spp. after heat stress may owe to a change in symbiont from a less thermally resistant type to a more resistant one. The change equates to a 1-1.5oC increase in thermal tolerance. As in #2 above, this type of acceleration of natural processes comes under the term “assisted” evolution. Berkelmans & van Oppen 2006 Proc R Soc B 273: 2305; Jones et al 2008 Proc R Soc B 275: 1359.

NOTE enriched carbon dioxide in the atmosphere both warms the planet and increases bicarbonate content of the oceans. This last leads to reduced pH of seawater in a process known as “acidification”. Decreased pH is known to interfere with normal calcification in many marine species, including essential skeletal construction in corals, as well as interrupting normal cellular processes

NOTE thus far, the researchers have identified at least 8 separate genetic lineages in different coral species, with some Acropora species hosting several. However, most Great Barrier Reef corals contain only 2 types, one of which is usually dominant; the other, recessive

4. Genetic engineering:
A topic relating to future survival of corals in face of ever-increasing seawater temperature involves heat-shock proteins, found in many or all animals. Researchers at several institutions are attempting to identify the specific genes in corals responsible for production of heat-shock proteins and antioxidant chemicals, with the intent of either selecting for them or enhancing production of them through genetic engineering. An experiment done by Stanford University researchers on a common reef-building coral Acropora hyacinthus in Western Samoa shows that colonies naturally experiencing high temperature variabilty (e.g., up to 6oC) in tidepools in summer exhibit greater levels of heat-shock proteins, host more heat-tolerant symbionts, and grow faster than individuals inhabiting less temperature-variable pools. When subjected to simulated bleaching events in the laboratory, these more heat-resiliant colonies show higher expression photograph of plate coral Acropora hyacinthus in Great Barrier Reef, Australiaof some 60 genes, including ones specifically involved in thermal tolerance. If expression of such “front-loaded” genes could be controlled through some sort of genetic engineering, coral survival in face of global warming would be improved. For overviews see Barshis et al. 2013 Proc Nat Acad Sci 110 (4): 1387 and Palumbi et al. 2014 Science 344: 895.

NOTE also known as “chaperone” proteins because their chief function is to repair damage to other proteins caused by environmental stresses

NOTE stress-related genes that are primed and ready to respond immediately to thermal stress

Plate coral Acropora hyacinthus

5. Improved settlement of coral larvae.
Although not directly related to issues of global warming, ways to increase settlement success and survival of coral larvae will be beneficial. Like larvae of other marine invertebrates, at the time of settlement the planula larvae of corals seek out suitable sites using physical and chemical features of the substratum as cues. One such cue is the presence of (settlement-inducing) bacteria, a subject of research of coral scientists at the CARMABI Research Station in Curacao. Researchers there through intensive selection and testing have identified several bacterial species and “cocktails” of same that increase settlement success.

drawing schematic of impeller system to moor over corals in the Great Barrier Reef, Australia6. Scheme to lower water temperatures around coral reefs. Of all ideas this is one of the more innovative and imaginative, but may be the least likely to work. Some time in early summer 2018 eight large, floating solar-powered impellers are to be set up along a 1km test-strip of the Great Barrier Reef to bring cooler seawater up from 10-30m depth to bathe the surface reefs. Water at this depth may be slightly richer in nutrients but, depending upon a reef’s geography, depth, and season, may not be all that much cooler than at the surface. The proposal has invited much criticism. One is that cooler waters contain more gases and, with slightly lower pH, may exacerbate acidification processes already being generated by increasingly higher atmospheric carbon dioxide levels. Just from an experimental standpoint, the project is too small in scope to provide reliable statistics, quite apart from lacking a proper control treatment. Without the last how can any measured amelioration of bleaching in the 1km test strip be linked to treatment? More than a single experimental strip would be needed to remedy this, along with matched control strips, and installation of these would require vastly greater financial commitment than than the already large amount being committed by the Australian government for this first test (estimated at almost 2m $US). The money would be better spent on more sensible proposals, such as ones listed above. Drawing and description courtesy Amy Mitchell-Wittington and the Brisbane Times newspaper.

NOTE depending upon season and local weather conditions, water temperatures at 10-30m depth may not differ much from surface temperatures, but would a deeper source be better? Several decades ago near Kona, the National Energy Laboratory of Hawai’i extended large pipes from the surface to 900m depth to access really cold water as a pilot study for generating electricity by thermal-energy conversion. An unanticipated spin-off was the immediate availability of cold (about 5oC) nutrient-rich water that allowed development of a multi-faceted intensive (i.e., land-based) mariculture industry for such temperate species as clawed lobsters, abalone, salmon, and seaweeds. No-one would recommend anything this extreme for resuscitation of a coral reef, but the actua lwater temperature resulting from the impellers may loom important to the success of the proposal


7. Biological control of seaweed overgrowth. One secondary effect of invasive lionfishes consuming seaweed-eating fishes in the Caribbean, whose numbers are already threatened by over-fishing, is exacerbation of the problem of seaweed overgrowth. Seaweed overgrowth through pollution and other sources of eutrophication is already a serious threat to many coral reefs, especially ones in newly developing countries. A suggestion presented in all seriousness by scientists at the University of New South Wales, Australia is to introduce algal-eating rabbitfishes Siganus spp. to the Caribbean area to consume excess seaweed growth, with the aim of revitilising the reefs. The first "knee-jerk" response to this brave but misguided proposal that would come from environmentalists, and really from any informed person, is "they can't be serious!". This is because almost every similar aattempt to control of an invasive species has led to failure, sometimes catastrophically. In defense of their proposal the authors argue that, based upon the success of rabbitfishes in invading the Mediterranean basin from the Red Sea and the fact that about 20% of Caribbean fish species, in any case, have originated from the eastern Atlantic region, invasion of the Caribbean by rabbitfishes seems all but inevitable. Rabbitfishes are effective photograph of a shoal of rabbitfishes Siganus sp. in the Mediterraneanherbivores, and in confrontation with lionfishes whether in the Mediterranean or Caribbean they may, because of their Indo-Pacific origin, be less vulnerable to lionfish predation than Caribbean species. Apart from a brief mention that the eating habits of rabbitfishes are different enough from native Caribbean herbivorous fishes that competition for algal foods would not be an issue, one would have to think that doing such a thing would be, to say the least, unwise. It is bad enough that such an invasion could happen naturally without risking yet another disaster with such risky human intervention. Bellwood & Goatley 2017 Curr Biol 27 (1): R13. Photo of rabbitfishes in the Mediterranean courtesy the authors.

Rabbitfishes Siganus sp. in the Mediterranean. Note the absence of algae 0.1X

some examples are brown tree-snakes in Guam (accidental introduction, but so abundant in some areas that they short out electrical lines), toads in canefields to control beetles, tree snails in Hawai'i to control giant African snails (these last also introduced), Burmese pythons in Florida (likely as unwanted "pets", but they did clean out all marsh rabbits, also introduced), mongooses in Hawai’i and in dozens of other South Pacific and Caribbean islands to control rats, and so on. The list goes on


8. Deeper reefs will be a source for coral replenishment after shallow reefs are killed. No. This popular belief stems from two assumptions, the first being that deeper or mesophotic reefs (30-150m depth) have similar species complements to shallow reefs, and the second, that deeper reefs will be schematic showing less susceptible to anthropogenic impacts than shallow ones. However, a recent report in the journal Science by a consortium of world scientists provides convincing evidence to refute these assumptions. Not only are shallow and deep reefs in both major ocean systems found to differ significantly in numbers and types of fishes and corals, but damage fom both natural and anthropogenic causes appears to be similar in both locations. Thus, hurricanes and cyclones can damage mesophotic reefs directly to well over 120m in depth, and broken-off debris and sediment burial is common to depths of 135m, both well within the mesophotic zone. In fact, deep reefs are mostly unsurveyed and may already have suffered from destructive fishing such as trawling,from mining, and from sedimentation and rubbish deposition. Bleaching occurs in deep reefs just as in shallow reefs. The authors' observations suggest that the potential for deep reefs to function as a refuge is actually much less than previously thought. Rocha et al. 2018 Science 361: 281. Photographs courtesy the authors and Science Magazine.

NOTE lit. "middle light" representing depths of about 100-490ft in depth. Corals at this depth are specially adapted to exist in low light conditions, with special complements of low-light sensitive algal symbionts to provide nutrition and energy products. They could no more live at shallow depths than shallow corals could live at deep depths. This is true also for many fish species, which have strong depth specificities



Depth profile of Pacific and Western Atlantic reefs showing
the extent of dissimilarity in fish species between shallow
and deep (mesophotic) reefs. The species shown are just
samples and are a mixture of Caribbean and South Pacific
forms. The authors note that corals exhibit the same pattern.
In short, shallow and deep reefs are quite different



Views of mesophotic reefs in the Caribbean, some in pristine health; others sediment-covered or with bleached corals, just as shallow reefs might be

photograph of a healthy reef at 80m depth in the Bahamas photograph showing sand-covered reef after 2016 Hurricane Mathew in the Bahamas photograph of bleached sheet coral Agaricia lamarcki at 85m depth in the Bahamas photograph of a healthy reef in Grand Cayman Island at 115m depth with a lionfish Pterois volitans
Healthy reef at 80m depth in the Bahamas complete with grey angelfish Sand-covered reef slope at 120m depth in the Bahamas after Hurricane Mathew 2016 Bleached plate coral Agaricia lamarcki at 85m depth in the Bahamas Reef at 115m depth in Grand Cayman complete with lionfish Pterois volitans

9. Invest in a global coral-reef conservation portfolio. Along the lines of investing in a stock portfolio with the surest returns, a consortium of 19 world experts on coral-reef conservation and preservation have come up with a clever proposal not to attend to all reefs in the future, but to focus on the ones with best prospects for survival. This would be a tall order were it not for an existing formula for stock-market investment known as Modern Portfolio Theory. Just as an investor's stock portfolio is selected on the basis of risks, so the authors categorise the world's reefs into a more easily dealt with subset of reefs. How is the selection made? The authors assess risk levels for each reef, both present and future, and assign scores to each. Such risks are of the kind that can't be easily changed as, for example, climate, past and projected future thermal stresses, storms, geographical connectivity, and so on. Opposed to these are risks such as extents of commercial fishing and pollution, deforestation, coastal over-development, uncontrolled aquaculture, degree of recreational use, and so on, that have the potential to be changed through carefully monitored future programmes of mitigation and conservation. The goal is to identify a portfolio of 50 "bioclimatic units", each about 500km2, a size large enough to contain a range of habitat types, sufficient genetic breadth, and broad ecological diversification. The final iteration of 50 selected reefs (see figure) contain 95% of all known coral species. Each selected bioclimatic unit will then be assessed for potential for improvement, including some of the novel interventions outlined in this section (Nos. 1-4), such as assisted colonisation or assisted evolution. The authors remark that transformation of now degraded reefs to healthy state in this way can restore now-absent ecological, economic and social benefits. The authors see their proposal as a sensible investment of time, effort, and finances to ensure the availability of replacement reef components when and if the climate stabilises. Beyer et al. 2018 Conservation Letters e12587.

NOTE hedging your bets in investment is an old idea, but has been formalised by a 1950s investment expert Harry Markowitz into a series of mathematical algorithms. Basically, the Theory works on the idea of diversifying investment into more than one stock, in other words, spreading the risk. This concept of not putting all your eggs in one basket is the basis for an investment counsellor asking the time-honoured question, "how much risk are you comfortable with?". The risk of holding a portfolio of diverse individual stocks is less than the risk of holding any single stock. And so it may be with investing in the future of coral reefsworld map showing 50 reef-sites with optimal features for selection for future remedial attention

map showing distribution of bioclimatic units, that is, selected reef systems throughout the world designated for future remediation

"SECURING A LONG-TERM FUTURE FOR CORAL REEFS" Hoegh-Guldberg et al. 2018 Trends Ecol Evol 2438 9pp.

Further clarity relating to the above entry on bioclimatic units is provided by four Australian and one American scientist (the former having co-authored the earlier article).

The same arguments are reiterated as in the first article, but the map is clearer. In particular, note the comparative richness of the reefs on the Bahama Islands, Cuba, and Hispaniola. No other Caribbean island is deemed by the scientists as worthy of bioclimatic-unit status.


10. Cryofreeze coral larvae and wait for better days. Sperm and plant spores can be frozen, then revived to perfect functionality after periods ranging from years to thousands of years (in the case of spores). So, why not coral larvae? Freeze them, store them, then wait for better conditions in the future for revival and outplanting. The problem is that in comparison with say, mammalian eggs, coral larvae are much larger, more complex, and thus more susceptible to damage from crystallisation. Despite much research on the matter, it has taken several decades to surmount these problems. However, research by a consortium of American and Taiwanese scientists has led to successful freezing and revival of 2d larvae of the mushroom coral Lobactis scutaria. How long a frozen larva can be maintained and successfully revived are questions that will be answered over time. In this initial study 2d Lobactis larvae are kept frozen for only a short time, with about 40% being revivable, and their free-swimming life is truncated by the researchers after 12h. This is a small but promising first step, and may indeed offer hope for more widespread reef restoration in the future. Daly et al. 2018 Scientific Rep 8: 15714.

photographs of mushroom corals Lobactis scutaria from Palau, Micronesia

NOTE cryopreservation of mammalian embryos has been possible for the past 3 decades but,
for a variety of reasons, success for non-mammalian species such as birds, amphibians, and
fishes has been slow in coming. Issues of cryopreservation include much larger size, fatty
yolk, and barriers to movement of cryoprotectants across cell and compartment membranes.
In fact, only in the past 3yr have scientists successfully frozen embryos of a non-mammalian
species, a zebrafish, using ultra-modern techniques, and research into cryopreservation of
invertebrates is still in its infancy

Mushroom coral Lobactis scutaria (formerly Fungia scutaria) is a common shallow-water species throughout the Indo-Pacific. It is monotypic, that is, with just a single species in the genus. The inset photo is a juvenile only a few weeks or months of age. Lobactis is hermaphroditic, with eggs and sperm being released from the mouth and fertilisation occurring in the plankton. The resulting planula larvae have only 2 cell layers, with no other differentiation, and are among the most morphologically simple larval form of marine invertebrates

schematic showing extent and timing of summer 20-15 bleaching event in American Samoaphotograph of bleached and unbleached coral Acropora gemmifera11. Select heat-resistant coral strains, cultivate in bleaching-resistant coral nurseries, and outplant into post-global-warming habitats. This sensible idea parallels other "selection"-type breeding proposals outlined in 1 and 2 above. Researchers from Stanford University, California have investigated the idea in American Samoa. They initially collect 800 coral bits from colonies of 4 species of corals from a shallow lagoon. The lagoon has limited water circulation and is subject to marked temperature variations. The scientists reason that corals from the lagoon would be adapted to tolerate such temperature shocks, and tests in the laboratory confirm this. The researchers then select 400 of these heat-resistant fragments and, along with another 400 from other areas to act as controls, translocate them into a nearby lagoon characterised byless extreme temperature fluctuations. They leave the corals to grow for a time until they can be experimentally tested for differences in heat tolerance. Eight months into this period, however, extremely hot ocean temperatures (bleaching episode summer 2015, see schematic on Left) cause extensive bleaching on the reef. On examination the researchers find that the first, acclimatised, batch are 2-3fold less bleached than the controls. The fragments have retained the temperature-resistance of the parent colonies (see schematic below). The propensity of coral fragments to attach and grow coupled with these findings provides hope for reseeding reefs damaged in the future by effects of global warming. Morikawa & Palumbi 2019 Proc Nat Acad Sci 6pp. 10.1073 Photograph courtesy the authors.

NOTE the acroporids Acropora hyacinthus and A. gemmifera, the pocilloporid Pocillopora damicornis, and the poritid Porites cylindrica

schematic comparing bleaching susceptibility of 4 species of corals from habitats with high- and low-temperature variabilities in American Samoa

Storm/earthquake damage

before and after photographs showing storm damage to a coral reef off the Kona coast, Hawai'iWhat about storm damage? Cyclonic storms like hurricanes and typhoons can quickly destroy a reef but, as mentioned elsewhere, if basic conditions are healthy the damage may not be permanent. There have been several published “before and after” accounts of storm effects on coral reefs, but one of the more complete describes a severe storm that struck the leeward Kona coast in Hawai’i in January, 1980. It lasted for several days with sustained 80kph winds, rain, and onshore swell and high waves (3-5m). The study answers the question: “What happens to fishes in a storm?”. Prior to the storm’s arrival, the author had been doing day and night SCUBA surveys of fish abundances for 2yr, and followed this up with 1.5yr of post-storm assessments. The storm decimated the shallow fringing reefs that consisted mainly of extensive growths of lobe-coral Porites lobata, the commonest coral in Hawai’i, interspersed with finger coral P. compressa and other corals (see photos) along with all associated invertebrates. Afterwards, various algal species opportunistically and sequentially colonised the rubble. These disappeared after a few months, in part because of the return of herbivorous fishes. The answer to the above question is that the storm barely harmed the fishes, as evidenced by just a few washed-up bodies, mainly comprised of surge-zone- and tidepool-inhabiting species. When the storm hit, the majority of fishes apparently moved en masse offshore into deeper water where they waited it out, then later returned to re-establish their territories. Overall, despite the considerable destruction of habitat caused by the storm, the author found no significant decreases in numbers of species or population abundances of fishes monitored for 23mo before and 16mo afterwards. Walsh1983 Coral Reefs 2: 49. Photographs courtesy the author.

NOTE the author reports on some 90 species observed during daytime and 50 species seen during nighttime (with some overlap), most with both pre- and post-storm abundance data

Before and after views of the Kona-coast reef that consisted mainly of mounds of lobe coral
Porites lobata and finger coral P. compressa. The storm broke off and tossed about massive
mushroom-shaped heads of the former, and reduced much of the latter to finger-sized rubble


photograph of hurricane damage to coral reefs around Cozumel, Mexico in 2005Two successive hurricanes, Emily and Wilma, struck the coast of Cozumel Island in 2005 with winds of up to 215km per h. Both inflicted major damage to the reefs, with plate corals overturned, finger corals churned up and deposited in “windrows”, and sponge “cemeteries” created. In some areas sand to a depth of 2m or more was removed and deposited elsewhere. With photograph of hurricane damage to coral reefs around Cozumel, Mexico in 2005continuance of global warming and the strength and frequency of such storms apparently increasing, this vulnerable area of the Caribbean may have to withstand even more such storms in the future. Alvarez-Filip & Gil 2006 Coral Reefs 25: 583; photographs courtesy the authors.

Broken and heaped-up lettuce coral Agaricia tenuifolia off the southern tip of Cozumel

Windrows of finger coral Porites porites

photograph of hurricane-damaged elkhorn corals Acropora palmata in Jamaica 1980 Prior to the arrival of Hurricane Allen to the north coast of Jamaica on 8 August, 1980, elkhorn corals Acropora palmata formed a "continuous thicket of huge tree-like colonies" in the offshore wave-break zone of Discovery Bay. All that was left afterwards was a rubble rampart. The corals never recovered. Woodley 1993 Coral Reefs 12: 138.

photograph of earthquake damage to Boiling Point reef in the Gulf of Honduras May 2009One tends not to think of earthquakes as potentially damaging to coral reefs but, of course, in some places at some times such must occur. photograph of earthquake damage to Boiling Point reef in the Gulf of Honduras May 2009 One recent example described by researchers in Belize was a 7.3 magnitude event that occurred at 10km depth, 125km northeast of the coast of Honduras in May 2009. Damage to most of the Belize/Honduras coastal area was light or non-existent, but a region of the Port Honduras Marine Reserve in the Gulf of Honduras suffered heavy damage. At Boiling Patch at 10-13m depth, for example, a section of reef slid away and cracks appeared (see photographs). Large areas of hard-coral lobster habitat were destroyed, and sponges, boulder corals, and lettuce-corals overturned. Foster et al. 2010 Coral Reefs 29: 19.

New escarpment at the reef edge


Cracks appear (15cm width)


photograph of starlet-coral colonies Siderastrea siderea illustrating peculiar "punctuated" growth patternAn interesting observation by researchers investigating shallow back-reef areas of the Florida Keys National Marine Sanctuary, is that several adjacent large colonies of starlet coral Siderastrea siderea have similarly peculiar, stacked-growth morphologies. Based on the height of each demarcation and estimated growth rates of S. siderea in this area of Florida, the authors have correlated each line with major hurricanes that occurred in 1935, 1960, and 1992 (see photograph). Each hurricane moved sediments that smothered the colonies. The last hurricane to strike the area in 2006 is thought to have cleared the sand from the tiered mounds, thus creating the odd-looking configurations seen in the photograph. The pattern of growth between these major storms is termed “punctuated growth” by the authors. Precht & Precht 2015 Coral Reefs 34: 771; photograph courtesy the authors.

“Punctuated growth” of Siderastrea siderea. Each
upper stack is about 10cm in height. Overall age of
each colony is about 75yr. Hurricanes thought to be
responsible for each section are the Great Florida Keys
Hurricane in 1935, Hurricane Donna in 1960, Hurricane
Andrew in 1992, and Hurricane Wilma in 2006, the
last of which cleared away the accumulated sand


photograph of unusual "pancake-stack" appearance of brain corals Diploria strigosa in St. CroixFor some reason the above authors missed an earlier 1998 account on the same subject, also published in the journal Coral Reefs. This earlier paper describes how survival of brain corals Diploria strigosa in Buck Island Reef National Monument, St. Croix is promoted by periodic clearing of sediment by hurricanes. The schematic below shows the process step-by-step. Following the last stage, new storms again remove the sediments, growth patterns are repeated, and the unusual “pancake” stack- appearance shown in the accompanying photograph is produced. Hillis & Blythell 1998 Coral Reefs 17: 262. Photograph courtesy the authors.

NOTE the blame for this, if any is to be assigned, is not just on the authors but also on the journal Editor and on reviewers of the article prior to publication

The dead mounds in the photograph are brain corals
Diploria strigosa that have “given up”. Other colonies
have survived 1-2 previous exposure/regrowth events

first of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology second of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology third of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology fourth of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology fifth of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology sixth of a series of drawings explaining how mound and brain corals attain unusual "pancake-stack" morphology
Normal globular shape in
8m water depth
Sediment accumulation kills the lower part of the colony More sediments might kill the colony completely Hurricane storm removes part or all of the sediments Vigorous growth may now produce a downward lip Downward growth stops as sediments again rise
Marine protected areas

photograph of sign in Little Cayman Island indicating locations of Marine Protected Areas
Establishment of underwater parks, self-guided snorkelling and SCUBA trails, and reef interpretation centres are useful in drawing attention to reef-conservation issues.  However, essential even for short-term survival of Caribbean reefs will be the establishment of “no take areas” (NTAs) in Marine Protected Areas (MPAs).  Useful guidelines for this have been established by the Great Barrier Reef Marine Park Authority in Australia for their reefs and, more recently, by the Marine Life Protection Act of 1999 in California.  Cousteau 2002 Skin Diver 51: 20. 

NOTE rules are fine, but what is most important is hands-on management with effective policing. While almost 20% of reefs (total world reef area of 527,000sq km) are within government-mandated MPAs, only a small fraction of these (>0.01%) are effectively managed in ways that will ensure their survival. Christie & White 2007 Coral Reefs 26: 1047.

 Conservation programmes in the Cayman Islands include the
establishment of “marine parks” where fishing is completely
banned, and of “replenishment” areas where line fishing is
apparently allowed. The truth is that all such plans are
only as good as is the commitment to enforcement



Glover’s Reef Atoll in Belize has had a “no-take” area designated at its south end since 1998.  What beneficial effect it may be having is still being determined.  At the time of writing it was apparently the second such reserve thus far established in Belize.  Illustration courtesy McClanahan & Karnauskas 2011 Coral Reefs 30: 9.

Although benefits of the no-fishing reserve at Glover's Reef have not clearly been shown for corals and fishes, numbers of commercially important spiny lobsters Panulirus argus responded quickly and significantly to absence of fishing pressure (see graph). However, abundance of a second, smaller species P. guttatus in the lagoon, not fished commercially, remained basically unchanged. The study emphasises the variable responses of even closely related species to establishment of fishing bans in the Glover's Reef area. Acosta & Robertson 2003 Coral Reefs 22: 1.

drawing of Glover's Reef Atoll, Belize showing location of the Glover's Reef Marine Reserve Glover’s Reef Atoll in Belize has had a “no-take” area designated at its south end since 1998.  What beneficial effect it may be having is still being determined.  At the time of writing it was apparently the second such reserve thus far established in Belize.  Illustration courtesy McClanahan & Karnauskas 2011 Coral Reefs 30: 9.
graph comparing abundances of 2 species of spiny lobster Panulirus argus and P. guttatus in Glover's Reef lagoon following imposition of fishing ban in 1998Although benefits of the no-fishing reserve at Glover's Reef are unclear for corals and fishes, numbers of commercially important spiny lobsters Panulirus argus responded quickly to absence of fishing pressure (see graph). However, abundance of a second, smaller species P. guttatus in the lagoon, not fished commercially, remained basically unchanged. The study emphasises the variable responses of even closely related species to establishment of fishing bans in the Glover's Reef area. Acosta & Robertson 2003 Coral Reefs 22: 1.






Spiny lobsters Panulirus argus 0.5X

photograph of spiny lobsters Panulirus argus

map showing location of Hol Chan Marine Reserve in Belizephotograph of school of gray snappers in Hol Chan Marine ReserveThe first marine reserve in Belize was that of Hol Chan Marine Reserve just south of Ambergris Quaye, established in 1987. Has it worked? Indeed, it has, and well, according to reports published 6 & 7yr after its establishment. The entire Reserve is less than 3sq km, but almost half of several target species, most notably snappers, grunts, and certain parrotfishes, show significantly increased abundance, size, or overall biomass in shallow sites of the Reserve. Standing stock of several commercially important species in the centre of the Reserve is over 4-fold greater than at its periphery, and more than 10-fold greater than in lightly fished areas of the Caribbean island of Saba. Polunin & Roberts 1993 Mar Ecol Progr Ser 100: 167; Roberts & Polunin 1994 Coral Reefs 13: 90; photograph courtesy Rod Bigelow, N.Y. bigeolowsociety.

photograph of parrotfish Scarus gauacaimicaNOTE the authors describe a second Reserve in Saba, also established in 1987 and, while small (0.9km2), is also enjoying similar protective results







The rainbow parrotfish Scarus guacamaia is one of the many target species that
has significantly increased in abundance and biomass in the Hol Chan "no-fish"
Reserve. Snorkellers have noted large shoals of large- bodied parrotfishes and
groupers, and also snappers (see photo above),moving through the reef channels at dusk


histogram comparing fish abundances within and without the Anse Chastanet reserve in St. Luciaphotograph of Anse Chastanet reserve in St. LuciaA protected reserve needn’t be large to be effective. Indeed, the smallest Caribbean reserve on record is only 2.6 hectares (150 x 75m) in size. Known at the time of this publication as the Anse Chastanet reserve, and now part of the larger Soufriere Marine Management Area in St. Lucia, the reserve originated as a roped-off area near a hotel designed to exclude fishing boats. However, its effectiveness in enhancing local fish stocks belies its small size. In only 2yr, not only had biomass of commercially important fish species more than doubled within the reserve than without (see histogram), but individual body sizes were greater. Roberts & Hawkins 1997 Coral Reefs 16: 150; photograph courtesy the authors.

NOTE 1 hectare =100 x 100m = 2.47acres

NOTE apparently biomasses of both predatory and herbivorous fishes increased, but one wonders about the extent to which a growing mass of predatory snappers and grunts would be attractive as a protected “refuge” to their prey. One visualises the tiny reserve as a hopper teeming with predators that would before-long outstrip its capacity to sustain more new recruits. Feeding of fishes within the reserve was not allowed


overlay map of Glover's Reef, Belize showing location of study sites in relation to location of Marine Protected Area (1998)As noted above, MPAs (Marine Protected Areas) have proven successful in maintaining and enhancing fish abundance and diversity in various coral-reef areas, but beneficial effects on corals have not been so apparent. For example, Glover’s Reef Atoll in Belize has had a “no-take” area designated at its south end since 1998, but assessments by researchers from the University of Miami reveal no significant benefit on coral cover, size of colonies, or abundance of juvenile corals. In fact, cover of broadcast-spawning species actually decreased over the decade of observation, driven mainly by an almost 4% decrease in cover of the dominant reef-building boulder coral Montastraea annularis. In contrast, coral species that brood their eggs showed only non-significant decreases in cover over the same 10yr period. Additionally, several coral-reef fish species, most notably acanthurid surgeonfishes and scarid parrotfishes, actually declined in numbers within the reserve as compared with fished areas outside of the reserve. Huntington et al. 2011 Coral Reefs 30: 1077.

NOTE this is the second such reserve established in Belize (see foregoing account)

NOTE other fish species, for example, hogfishes, black groupers, and lane snappers, did show increased numbers in the reserve, but the reason for increase in some species and decline in others is not known


Glover's Reef is one of 3 atolls in the Belize Barrier Reef. It consists
of several island cayes (black areas in the illustration) surrounding
a shallow lagoon. Within the lagoon are several hundred patch reefs

  map showing location of the Florida Keys National Marine SanctuaryHas the Florida Keys National Marine Sanctuary worked? This 10,000km2 marine protected area extends from Key Biscayne southwest to the Dry Tortugas (see map) and was established in 1998 as a “no-fish” sanctuary. Transect-survey assessments by SCUBA in selected parts of the Sanctuary over a 14yr period from the Sanctuary’s inception suggest that the answer for fishes, most notably commercially fished species such as groupers and snappers, is a resounding “yes”, but that for corals is a “no”. Although the latter conclusion is based mainly on significant declines at all sites in cover of mound corals Orbicella (Montastraea) annularis, other coral species also declined, both at the specific sites surveyed and also in nearby areas of the sanctuary. The authors blame the overall decline on disease, bleaching, hurricane damage, and declining water quality. Toth et al. 2014 Coral Reefs 33: 565.

A basic premise in the establishment of marine reserves is that the now protected breeding stocks of fishes and invertebrates within them will provide new recruits to neighbouring areas that may themselves be overfished or otherwise depauperate of certain species.  This often happens, but may not, depending upon the species.  For example, a study on recruitment of bicolor damselfishes Stegastes partitus on reefs along the coasts of Belize and Mexico shows, in fact, that there is little movement of new recruits beyond the area in which they are spawned.  Thus, damselfishes originating in areas such as Turneffe Atoll in the south do not tend to colonise Banco Chinchorro Reef in the north, and vice versa.  Such findings are schematic showing otolith shape and locationuseful to fisheries scientists who set up and manage such reserve areas.  Chittaro & Hogan 2013 Coral Reefs 32: 341.

NOTE  the scientists analyse an adult fish’s otolith for its elemental chemical composition and then determine the liklihood that it originated from one natal (birth) area or another


X-section of otolith of (in this case) a dusky damselfish.
Note the annual growth lines indicating an age of 14yr. The
paired otoliths provide balance and acceleration input


Another example of positive effects of fishing bans on increasing long-term fishing yields relates to parrotfishes in Bermuda. Prior to the Bermuda Department of Environment & Natural Resources banning trap-fishing in April 1990, sex ratios of terminal-phase males to initial-phase individuals of 4 common species were skewed at about 0.10 (i.e., 1 male: 9 initial-phase). Four years later the ratio had rebounded to about 0.45, similar to that in unfished sites in the Bermuda region. O’Farrell et al 2016 Coral Reefs 35: 421.

NOTE the 4 species include stoplight Sparisoma viride, redband Sparisoma aurofrenatum, queen Scarus vetula, and princess Scarus taeniopterus


Another aspect to consider regarding marine protected areas is that protection provided to carnivorous species within the reserve may mean enhanced predation by them on their own prey species within the reserve. An example of this is given by researchers monitoring a protected area (Exuma Cays Land & Sea Park) in the Bahamas over a 2mo period in springtime where density of black sea-urchins Diadema antillarum significantly decreased, presumably owing to photograph of white grunt Haemulon plumieriincreased numbers of their own predators. Harborne et al. 2009 Coral Reefs 28: 783; photograph courtesy Geoffry Schultz BLUEJACKET SAILING SITE.

NOTE actually, the researchers find zero black sea urchins within the reserve, as compared with a baseline number of 25 present in a 350m2 sample area outside the reserve

NOTE predators include 8 species of fishes, the most important one based on biomass within the reserve and preference for sea urchins in its diet, being white grunts Haemulon plumieri


White grunt Haemulon plumieri 0.5X

  photograph showing diversity of an Indo-Pacific reef
"Too little, too late"? Scientists with interests in reef conservation note that No-Take Areas thus far established for world reefs are mostly of inadequate size. Even the largest are not self-sustaining because they are too small relative to scales of natural and human-induced disturbance, and to the potential for colonisation by invertebrates and fishes. In an attempt to redress this, in 2004 the Great Barrier Reef Marine Park Authority increased the size of its NTAs from 5% of total park area to 33%, and U.S. government authorities have proposed similar, more modest increases to 20% for reefs under jurisdiction to start in 2010. Bellwood et al. 2004 Nature 429: 827.

graph showing reduction in worldwide coral cover since 1988Recent assessments suggest that about 40% of world-coral stocks have disappeared in just the last 3 decades.  In a very nice review paper on wildlife losses in the world oceans from historical to present-day times, the authors’ summary is that we now must play catch-up not just in establishing marine-protected areas, but in tailoring them to be operational in our changing oceans.  McCauley et al. 2015 Science 347 (6219): 247.


photograph of Roatan Marine Park offices, RoatanA ray of hope for coral-reef conservationists in the extreme western Caribbean region has come with the establishment in 2010 of a National Marine Park encompassing the Bay Islands of Honduras. Marine waters surrounding the islands are classified into 3 zones, each with restrictions on activities that can take place within it. Earlier in 2005 the creation of Roatan Marine Park in Roatan, the busiest SCUBA-diving and snorkelling island of the Bay-Island archipelago, has led to an active programme by its enthusiastic and dedicated staff that includes educational visits to schools, establishment of guidelines for activities of tourist-, sportsfishing-, and SCUBA-boats, and enforcement of bag limits for fished species and of no-take rules for other species.

A jewel in the crown of Roatanian reefs, and perhaps the finest and most pristine example of growth of staghorn corals Acropora cervicornis in the entire Caribbean area, is a region on the south side of the island known as Cordelia Banks. For anyone who yearns to have seen what Caribbean reefs may have looked like several decades ago, this is the place to visit. Somehow, in close proximity to the largest towns on the island, two busy cruise ports, and ports housing fishing and prawning fleets, the 3 reefs making up the Banks have remained in near perfect condition. Coral-reef experts think the explanation may be in the presence of a deep channel between the island and the Banks with associate along-shore currents that maintain high-quality water conditions. But it must have involved much more than that, including respect by Roatanians of a precious and unique resource that has kept boat, fishing, and tourist traffic to a minimum. The Banks are so shallow that even a medium-sized vessel could remove much of the coral coral cover in a single misguided pass. CLICK HERE to see a video of the Banks courtesy Jon Slayer & Roatan Marine Park.

NOTE based on the presence of evident scars on portions of the Banks, this has happened in the past, but because basic conditions for good health remain unchanged, the reef is able to heal itself

NOTE the video begins with comments from Giacomo Palavicini, Executive Director of Roatan Marine Park, Roatan

map of Roatan showing location of Cordelia Banks photograph of staghorn coral Acropora cerviconis at Cordelia Banks, Roatan photograph of corals at Cordelia Banks, Roatan Giacomo Palavicini
Map of Cordelia Banks, Roatan. Map courtesy Alicia Medina, Mesoamerican Reef Program & WW Fund Diver from Roatan Marine Park conducts a survey at Cordelia Banks. Photo courtesy Dano Pendygrasse Close view of staghorn corals Acropora cervicornis. Photo courtesy Giacomo Palavicini, Executive Director, RMP

Along the same lines, university researchers in Columbia have recently discovered a pristine and what they term “paradoxical” coral reef in Cartagena Bay, Columbia. It has high diversity (>30 spp) and is dominated by large colonies of mound coral Orbicella (Montastraea); see photographs below). With an estimated 80% coral cover, it is in the scientists’ view perhaps the best coral reef on the continental shelf of Columbia. The situation is “paradoxical” because Cartagena Bay is characterised by seasonal turbidity, eutrophication, and high levels of sedimentation that appear to have killed off most other coral reefs within it; this reef has, then, an unlikely probability of existing. The authors recommend further study of the reef and its environs to attempt to understand the unique factors involved in its survival. In this regard, one feature of interest is the common, flattened growth of most of the mound corals, possibly a strategy that increases the light-intercepting area for photosynthesis. Lopez-Victoria et al. 2015 Coral Reefs 34: 231; photographs courtesy the authors.

NOTE the principal cause of reef destruction in Cartagena Bay is thought to stem from construction during 16th Century Spanish occupation of a transportation canal system that diverts freshwater into the Bay. The Canal del Dique is 118km in length and connects the Bay to the Magdalena River

photograph of unusual coral reef in Cartegena Bay, Columbia photograph of unusual coral reef in Cartegena Bay, Columbia photograph of unusual coral reef in Cartegena Bay, Columbia
Much of the 3-5m-depth reef in Cartegena Bay is dominated by mound corals Orbicella (Montastraea) spp. Despite being in shallow water some of these flattened Orbicella spp. colonies reach diameters >3m Some parts of the reef have high species richness, as shown by the 6-or so species visible here

photograph of regrowth of elkhorn corals Acropora palmata showing new branches and "re-sheeting"Although regrowth of dead Acropora spp. coral is heartening to see, scientists are concerned that new branching growth and “re-sheeting” of original surfaces in elkhorn coral A. palmata may not be sturdy enough to withstand severe wave forces, especially from storms of the magnitude and frequency predicted over future decades. Bonito et al. 2006 Coral Reefs 25: 46. Photographs courtesy the authors.

NOTE it is not clear whether this is truly regrowth from some still-living part of the coral framework, or whether the new growth derives from settlement of new larvae






Re-growth of elkhorn corals Acropora
from dead framework. An example
of "re-sheeting" is shown in the inset


photograph of new growth of elkhorn corals Acropora palmata in Los Roques National Park, VenezuelaAnother note of optimism relating to elkhorn corals Acropora palmata is an observation by scientists at Simon Bolivar University, Caracas of a resurgence in the species’ abundance in an area of Los Roques National Park, Venezuela. The specific area, Cayo de Agua, is a coralline caye with high density of A. palmata including adults, juveniles, and new recruits. The new corals are mostly disease-free, but the authors note signs of white-band disease in a few of the older colonies. Re-population of the reefs is occurring both by sexual and asexual (fragmentation) means. Other than naming the entire area a “Park” in 1972, the Venezuelan government appears not to have designated any part of it a protected reserve. However, while sports fishing is allowed, development and tourism seem to be carefully monitored. Zubillaga et al. 2005 Coral Reefs 24: 86.

NOTE the Park is an archipelago of some 350 islands and cayes located 130km off the Venezuelan coast approximately midway between Grenada to the east and the ABC Dutch islands to the west. It seems to be mainly an area of tourism but not, fortunately, a cruise-ship stop as is neighbouring Margarita Island, Venezuela (but here the ships stop in a remote part of the island). Photographs online show the islands of Los Roques National Park to be pristine, beautiful, and mostly undeveloped; reminiscent of many areas in the Caribbean that 60yr ago were also pristine and untouchedc

  What do SCUBA-divers and snorkelers want to see on their dives?  More broadly, what attributes of coral-reef ecosystems are important in deciding whether to make a Marine Protected Area, and what management measures would enhance existing features of MPAs for dive tourists?  In a survey in Jamaica 195 divers were asked to rank the following 13 attributes of coral-reef ecosystems from most wanted to least wanted. Check them over, think of what you would like to see yourself, then CLICK HERE to see what the SCUBA-divers in Jamaica selected. Williams et al. 2000 Envir Conserv 27: 382. 

coral cover

sharks/marine mammals

coral variety


reef structure

fish abundance

large corals

unusual corals


unusual fishes

fish variety


big fishes



photograph of a pristine Caribbean reef taken in Barbados in 1967In this ranking study, the first of its type done in the Caribbean, the authors conclude that if fishing restrictions are well enforced, MPAs in the Caribbean will be effective in ways photograph of a Caribbean reef overgrown with algaeappreciated by divers. Interestingly, a comparable survey on the Great Barrier Reef shows corals and their attributes to be more important that fishes.  The authors point out that such a survey in Jamaica may have yielded biased responses based on the present poor state of its reefs (over-fishing, hurricane damage, algal overgrowth), and different responses may have been obtained had the survey been done in a more pristine area.

Two reefs: one pristine...


...the other, overgrown with algae

Farming corals for benefit

Reef organisms are being investigated for pharmacologically active compounds.  Rather than considering such medicinal use of reef organisms negatively, reef conservationists can use them to focus attention on the value of maintaining reefs in healthy condition.
photo composite showing different uses to which reef organisms are being put


photograph of a sign at the Waikiki Aquarium explaining about coral farming
The propensity of corals to grow from fragments has enabled the development of unique conservation programmes involving in situ pruning, gardening of the coral explants, and transplantation after attachment and growth to denuded areas.  It also permits the culturing and shipping of live corals to display centres worldwide.  Rinkevich 2000 Mar Biol 136: 807; Becker & Mueller 2001 Bull Mar Sci 69: 881; Epstein et al. 2001 Restoration Ecol 9: 432.  

NOTE fragments or branches obtained from donor colonies and attached to the sea bottom

NOTE in concept this is good, but in practical terms it is difficult. This is because areas that have lost their coral cover have usually done so because conditions have changed for the worse. Unless the underlying conditions are identified and improved, such "farming" has little chance of success





Sign at Waikiki Aquarium, Honolulu


photographs of "farmed" elkhorn coral Acropora palmata from a 2006 conservationist project in Puerto Rico involving commercial aquariumsDuring a meeting in the Tres Palmas Reserve, Rincon in Puerto Rico in 2006 a group of 20 commercial aquarists and researchers collected eggs of threatened elkhorn corals Acropora palmata, fertilised them in the lab, and took 450,000 of the resulting larvae back with them to participating public aquariums. There, about 20% of the larvae were settled successfully onto small ceramic tiles and cultured in 10 worldwide aquariums. Eighteen months later and a little before this account was published, about 800 colonies of up to 9cm diameter had been produced. Since then, more have been produced. Have they been disseminated within the Caribbean basin? We don’t know. The authors refer to the project as a “Noah’s Ark” and anticipate success in future similar world endeavours. Petersen et al 2008 Coral Reefs 27: 715.

NOTE the achievement is, indeed, wonderful and the participants can be proud of their accomplishments. However, a naive reader, while joining in the celebrations might at the same time ask, “What’s taken them so long?”

Stages in "farming" of elkhorn coral
Acropora palmata
in commercial aquariums
around the world. Top: a colony a few weeks
of age; bottom: 18mo of age, 9cm diameter

before and after restoration of damaged area of a reef in Puerto Rico using farmed colonies of staghorn coral Acropora cervicornisGood use of farmed colonies of staghorn coral Acropora cervicornis was made in restoration of a reef in Tallaboa, Puerto Rico damaged in 2006 by accidental grounding of an oil tanker. Here, fragments of coral found near the damaged area along with several hundred cultured colonies of 20-40cm diameter obtained from a nearby coral nursery were used by coral conservationists from Florida and Maryland to restore the approx. 7500sq m impact area. The corals were attached with nails, caging, screws, glue, and cable ties, and these, in combination with stabilisation of loose corals and coral rubble on the site, have led 9yr later to a marvelous rejuvenation (see before and after photos). Griffin et al. 2015 Coral Reefs 34: 885. Photographs courtesy the authors.






Before and after photos of the restoration. Note the healthy
stands of staghorn corals Acropora cervicornis in the previously
damaged area. Interestingly, prior to the incident staghorn
coralswere absent from the actual site of the grounding, but
were observed by divers to be present in adjacent regions


photograph of bath sponge Euspongia sp.The realisation by sponge-fishers in Florida that bath sponges could be fragmented and the pieces readily grown in sea farms caused a resurgence in the market for natural sponges.





Bath sponges Euspongia sp. for sale in a tourist shop, 0.25X.
Judging by their diverse shapes and textures, these
specimens have likely been fished rather than cultured


graph showing nests of hawksbill turtles counted each month of the year in BarbadosNumbers of turtles in the Caribbean region have greatly declined through over-fishing.  Re-stocking programs have been underway for several decades but their effects on population size and distributions are not yet well understood. In Barbados, turtle-fishing has been banned since 1998. Data from researchers involved with the Barbados Sea Turtle Project based at the University of the West Indies show that nesting hawksbill photograph of hawksbill turtleturtles Eretmochelys imbricata in Barbados have increased nearly 8-fold over a 7yr period after the ban came into effect (see graph). Beggs et al. 2007 Endangered Species Res 3: 159.


Hawksbill turtle Eretmochelys
, 0.1X


photograph showing baby turtles being released in Barbados


These young green turtles Chelonia mydas are from a hatchery in Costa Rica operated
in years past by the legendary conservationist and green-turtle specialist Archie Carr.
The hatchlings shown here are being released in Barbados in summer 1967 as part of
"Operation Green Turtle", a cooperative effort at that time with the U.S. Navy to
distribute eggs and hatchlings to beaches in the Caribbean Sea and Gulf of Mexico


  Giant clams are not found in the Caribbean but are of great commercial importance in other reefs in the world.  Pioneering studies on their culture done at the Micronesian Mariculture Demonstration Center in Palau have led to prospects of widescale restocking programmes.
photograph of a giant clam Tridacna sp. in the Red Sea
Giant clam Tridacna sp. in Red Sea 0.25X
culture facility for giant clams Tridacna maxima in Palau
Tridacna gigas being cultured in Palau
photograph of giant clams Tridacna maxima under culture in Palau
Closer view of clams in their culture trays
photographs of giant clams Tridacna maxima in culture in Palau at a young age
Shows a juvenile & one even younger (inset)

Unfortunately, while techniques of rearing Tridacna gigas are now well-established, the costs of maintaining juvenile stocks in captivity until they reach size-refuge from predators such as rays, triggerfishes, and turtles (up to 4yr) is impeding the success of the programme especially in small island nations. Another photograph of culturists restocking giant clams into natural habitat obstacle is poaching, as out-placing of clams in unprotected and/or unmonitored areas is rarely successful because of poaching. A programme in the Solomon Islands begun about 20yr ago has co-opted a number small-scale culture operations that mainly proide giant clams for the aquarium market. Local ICLARM scientists encourage the farmers to set aside 2% of their marketable stock for restocking purposes, done when the clams attain a self-sustaining size. The juvenile stock is distributed to diverse reefs under the farmers’ tenure, thus providing protection, and enhancing population dissemination and genetic diversity. Bell 1999 Coral Reefs 18: 326. Photo courtesy M. McCoy and the author.

NOTE International Center for Living Aquatic Resources Management, initially established in the Philippines, now endorsed by at least 12 countries and involved in resource development and management, aquaculture, and training and education

Restocking of juveniles brings up problems of where, for best
growth and survival, and how many, for maximal fertilisation
success balanced against restocking as many reefs as possible

Creation of artificial habitat

photograph showing a patrol boat sunk for tourist viewing in Cuba
Sunken ships and other debris provide a diversity of habitats for invertebrates and fishes similar to that of natural patch reefs. 




Patrol boat sunk for viewing by
SCUBA-divers off the coast of Cuba

Intentional sinking of ships to create novel dive sites has the double benefit of providing new substratum for colonisation by sessile reef organisms and population by fishes, and of drawing SCUBA-traffic away from other, perhaps more environmentally sensitive reef areas. photograph of tugboat wreck on west coast of Barbados
This tugboat wreck off the west coast of Barbados is a popular spot for SCUBA-divers. . Although the ship was not sunk intentionally as a "novel dive site", it serves the same purpose
photograph of soft corals on the Fuji Maru in Truk Lagoon, Micronesia
Soft corals are abundant on the wreck of the cargo ship Fujikawa Maru in Truk Lagoon, Micronesia. This vessel and many others were sunk as part of a military strike in 1944, and the area is a popular dive spot

: a brilliant idea for regeneration of reefs is to set out reef balls, the more the better. Reef balls are large concrete structures with holes scattered over their surfaces. The holes allow ingress and egress for fishes and invertebrates, and provide greater surface area for attachment of sessile organisms. The concrete used in their construction has a larger component of silicon than normal, and is buffered to reduce acidity. photograph of reef balls set out as an artificial reef at Marriott Hotel, Grand Cayman IslandAdditionally, the outer surface is pitted, enabling easier attachment of larvae of organisms such as corals, sponges, gorgonians, and so on. Apparently, more than half a million balls have been deployed thus far in over 60 countries. Caribbean islands that have adopted the idea include Antigua, Barbados, Cayman Islands, and Florida, to name a few. The balls are relatively inexpensive to manufacture and install and, although still in the category of "artificial", are more attractive and certainly more functional than rubber tires, old automobiles, and other rubbish that has been used in the past. Photograph on Right courtesy Barbados Trident Tours; Photograph on Left courtesy Marriott Grand Cayman Hotel.

photograph of reef balls arrayed in BarbadosNOTE the REEF BALL FOUNDATION, established in 1993 has more information about this innovative restorative technology REEFBALL




Although initially not as attractive as the real thing, the balls will create the foundation
for natural coral growth and, in time, should be indistinguishable from natural coral reef


photograph of pristine Caribbean reef
In this ranking study, the first of its type done in the Caribbean, the authors conclude that if fishing restrictions are well enforced, MPAs in the Caribbean will be effective in ways photograph of a Caribbean reef overgrown with algaeappreciated by divers. Interestingly, a comparable survey on the Great Barrier Reef shows corals and their attributes to be more important that fishes.  The authors point out that such a survey in Jamaica may have yielded biased responses based on the present poor state of its reefs (over-fishing, hurricane damage, algal overgrowth), and different responses may have been obtained had the survey been done in a more pristine area.

Two reefs: one pristine...


...the other, overgrown with algae