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



status of the world's remaining reefs
What is the future of the world’s coral reefs? Data published 2 decades ago show that 10% of the world’s reefs are devastated; that is, degraded beyond recognition. Another 30% are in a critical state and will be gone in a couple of decades, while another 30% of the worlds’s reefs are threatened and are predicted to be gone in 40 years. The remaining 30% are stable and will last for the forseeable future. Wilkinson 1992 Proc 7th Intern Coral Reef Sympos 1: 11.

NOTE when this paper was presented and later published, the Great Barrier Reef in Australia was categorised as "stable". Now, only 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"


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 Air Canada provides something else to think about. Greenhouse-gas emission (presumably mostly carbon dioxide) for a single person flying cross-continent on a commercial jet airplane can be as much as 2.3 tonnes. Air Canada also suggests that the carbon-offsite price for this can be met by redeeming 5,406 travel points. How this would work is roughly as follows: the equivalent cash for these points (perhaps $40-50 Can) is sent to an offset management company to use to support a variety of carbon-offset programs, 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 or other companies get out of it are offset credits (for use for taxation purposes?). The success of this and similar carbon-offset programs has yet to be assessed, but the idea is good

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
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 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 untouched

  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 rwell-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