47 Photos - Mar 22, 2015
Photo: This is a good news story about corals for a change!

Corals in the genus Acropora, which contains close to 150 species, are major reef-building corals worldwide. There are only 3 species in the Caribbean. The elkhorn coral, Acropora palmata, is among the 2 or 3 most important reef-building species. It was largely  killed off in Barbados by the mid 1900s, due to sedimentation. Acropora cervicornis, the staghorn coral, was abundant at about 30 ft depth on the west coast when I attended a field course at the Bellairs Research Institute in 1966, but with A. palmata,  died off through most of the Caribbean in the early 1980s due to a disease.  I never saw either species here in visits and snorkelling ventures from the late 1980s though to 2012.*

So I was very surprised on one of my first snorkel outings during a 3 month visit to Barbados in 2015 to encounter a perfect little colony of A. palmata!  I wrote a government biologist about it and she told me that they has seen a few on the west coast, but they seem to stop growing early on. A month or so later, I was thrilled to see several patches of living A. cervicornis near to a popular wreck site In the Recreational Zone of the Barbados MPA (Marine Protected Area) in about 30 feet of water. More snorkelling revealed only one more A. palmata in the area, and no other areas of A. cervicornis. I hadn't explored much in the shallower reef flat areas, but when I did, I made an even more surprising discovery: numerous, healthy colonies of A. prolifera, a hybrid between A. palmata and A cervicornis! Moreover, they recalled some of the beauty I had encountered swimming over Acropora sites in the Grenadines in the 1960s. A little literature research made me optimistic that Barbados reefs could host a lot more of the hybrid species in future - with a little help to ensure that conditions are favourable for such an outcome.

Acropora prolifera was recorded in Barbados historically (http://discover.odai.yale.edu/ydc/Record/2944643), but not, as far as I can determine, in recent years.  I am told by Hazel Oxenford of the Centre for Resource Management and Environmental Studies at the University of the West Indies in Barbados (March 26, 2015) that "We have been mapping the come-back of acroporids on the southwest and west coasts of Barbados and doing a number of tests (toxicity, reproductive capacity, healing rates etc)... A number of excellent scientists on the team – publications will follow."

These three coral species are easily recognized.
I am posting these photos with a few comments in the interest of documenting their occurrence, fostering public support for coral conservation and to encourage some citizen science to identify more sites, to monitor them, and nurse these species along in Barbados and elsewhere in the Caribbean. As well, I simply want to celebrate a little Good News about corals.

The original photographs are available on this site. I encourage  use of these photos for educational purposes and nature-oriented advocacy under a Creative Commons License (http://versicolor.ca/reeflicense)

- David G Patriquin
Professor of Biology (retired)
Dalhousie University
Halifax, Nova Scotia, Canada

I welcome feedback. My e-mail address is
patriquiATdal.ca
(Please put Acropora in the subject line.)
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*With one exception: In 1994, I encountered a large single colony or small stand of Acropora palmata at Bath on the east coast.  It was in an area of high surf and currents and I was not able to relocate it. It was perhaps 5 m across, 75-100 cm height, and very healthy.Photo: A. prolifera originates as a hybrid between A. palmata and A. cervicornis. Current evidence suggests it cannot propagate sexually on its own, but can backcross with either of the parents. It can also propagate by asexual fragmentation.
(Richards and Hobbs, 2015)

Richards, Z.T   & Hobbs, J-P.A. 2015. Hybridisation on coral reefs and the conservation of evolutionary novelty. Current Zoology 61 (1): 132–145.Photo: A small specimen A. palmata at about 2 m depth in the Recreational Zone of the Barbados MPA. It is one of the two parent species for A. prolifera.

"This species is structurally complex with many large branches. The coral structure closely resembles that of elk antlers. These branches create habitats for many other reef species, such as lobsters, parrot-fish, snapper shrimps and other reef fish...Historically, the majority of elkhorn coral reproduction has occurred asexually; this occurs when a branch of the coral breaks off and attaches to the substrate, forming a new colony, known as fragmentation. 

-Elkhorn coral in Wikipedia, accessed 24 March 2015/Photo: A. cervicornis at about 30 ft depth in the Recreational Zone of the Barbados MPA. It is the other parent species for A. prolifera.

"The staghorn coral (Acropora cervicornis) is a branching, stony coral with cylindrical branches ranging from a few centimetres to over two metres in length and height....The dominant mode of reproduction for staghorn corals is asexual, with new colonies forming when branches break off a colony and reattach to the substrate. This life history trait allows rapid population recovery from physical disturbances such as storms. However, it makes recovery from disease or bleaching episodes (where entire colonies or even entire stands are killed) very difficult.

"Sexual reproduction is via broadcast spawning of gametes into the water column once each year in August or September. Individual colonies are both male and female (simultaneous hermaphrodites) and will release millions of gametes. The coral larvae (planula) live in the plankton for several days until finding a suitable area to settle; unfortunately, very few larvae survive to settle and metamorphose into new colonies. "

-Staghorn coral in Wikipedia, accessed 23 March 2015.Photo: A. prolifera.

"Acropora prolifera is very similar to staghorn coral (Acropora cervicornis) in appearance but usually forms smaller, denser clumps. The branches are mostly horizontal and often divide near the tip, sometimes fusing with other branches. It also resembles elkhorn coral..."

- Acropora prolifera in Wikipedia, accessed 24 March 2015

Both A. palmate and A. cervicornis are listed on the ICUN Red List of Threatened Species (http://www.iucnredlist.org/). A prolifera is not listed as such, because hybrids are excluded from the ICUN lists. Richards and Hobbs (2015)  argue that exclusion of hybrids needs to be re-evaluated, referring specifically to Acropora:

 "We consider avoiding hybrids in coral reef conservation could result in a serious mismatch between policy and real-world conservation needs. Corals from the genus Acropora make a case-in-point. Amongst this group of highly threatened corals, putative hybrids are spread right across the web-of-life ... hence failing to protect hybrids could lead to large potential losses of phylogenetic diversity."Photo: Approximate locations of the three Acropora species in the Recreational Zone of the Barbados MPA.
Acerv= Acropora cervicornis; Apal=Acropora palmata; Apro=Acropora prolifera with no. of individual units in parentheses.

Six Zones corresponding to those of Lewis (1960) were identified: Reef Flat, D-P (Diploria-Palythoa Zone), Reef Crest, Seaward Slope, Reef Front and Deep Water Communities.

Photographs and description of the zones and other species are posted at https://plus.google.com/u/0/photos/110155833567072600167/albums/6107944577768953265Photo: It's quite possible that A. prolifera will spread and become more widely established in Barbados.:

"In the Caribbean Acropora system, hybrids were documented previously as being rarer than the parental species (Goreau, 1959; Lang et al., 1998; Cortes, 2003; Willis et al., 2006). Within the past 5 years, as the parental species have declined the relative abundance of hybrids has increased and hybrid recruits have extended their known range into areas typically dominated by the parental species (Fogarty, 2010, 2012; Japoud et al., 2014). Thus, in this period of coral reef degradation, the Caribbean hybrid Acropora prolifera has proliferated and now occurs as a variety of morphologies, in a range of habitats and in both overlapping and distinct communities from the parental lineages. If A. prolifera continues to expand its abundance and range, the functional role this species plays in the coral reef ecosystem will increase. Given that stony corals provide food and habitat for a myriad of associated flora and fauna (e.g. fish, crustaceans, molluscs, worms, sponges); an increase in habitat provided by hybrid corals would have flow-on benefits to biodiversity. Hybrids are likely to also provide other important ecosystem services such as reef construction.
- Zoe T. RICHARDS &  Jean-Paul A. HOBBS. 2015. Hybridisation on coral reefs and the conservation of evolutionary novelty. Current Zoology 61 (1): 132–145.Photo: I counted 17 discrete colonies or patches of A. prolifera within an area of approximately 100 square meters. Another, single colony was sighted approximately 50 meters from that site. 

The photo at left (Specimen #1) shows the largest single, discrete patch or colony, which is 180-200 cm  across in the longest dimension. It probably involved fusion of several smaller, individual colonies. The top is approximately 50 cm below Mean Low Water. GPS Coordinates: 13 10.763, -059 38.414

Note the highly thickened, short branches which form a palmate structure at right where it meets the colonial zoonanthid Palythoa caribaeorum, grading into bushier forms towards the edges.
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March 22, 2016: I counted 30 discrete colonies, two of which were clearly composites (several individuals that grew together). Some were likely recently established from fragments, others are ones that I missed in 2015. (The water was exceptionally clear when I did the count in 2016, while in 2015, it was quite turbid.) Clearly these colonies should be properly mapped and monitored. There were 6+ loose fragments in 2016, which would be great candidates to move elsewhere in a similar zone. I am hopeful that the recently formed Barbados Coral Reef Restoration Alliance (CORALL) will be pursuing such options.Photo: Area of Specimen #1 was exposed during a very low tide. Photo at 12:31 a.m. on April 21, 2015.Video: Video centred on the largest discrete colony or patch and illustrating other discrete colonies nearby. The camera was held steady, but moves about due to wave action.Photo: Specimen #1, showing at right the highly thickened knobby branches.

Subsequent photos show each of the other 17 A. prolifera colonies or discrete (connected) groups sighted in the Recreational Zone of the Barbados MPA, followed by photos of A. palmata and A. cervicornis.Photo: A. prolifera Specimen #2. Scale is 30 cm. Estimated Maximum Linear Dimension:  46 cm

To provide scale, I placed a 30 cm plastic tie over the colony, took a photograph, removed the tie and took another photo, and applied the scale to the latter accordingly. The Maximum Linear Dimension is an estimate based on this scaling, rather than a direct measurement.

How old might this speciment be? Lewis et al. (1968)  recorded a mean monthly increment for branches of A. cerviocrnis in Barbados of 1.2cm or 12 cm/year (2.2 cm in Jamica).  A study in the northeastern Caribbean (Gladfelter et al., 1978) reported growth rates of  71 mm/yr for A. cervicornis, 59–82 mm/yr for A. prolifera, and 47–99 mm/yr for A. palmata, i.e similar magnitudes for the thee species. Assuming 1.2 cm per month for A. prolifera in Barbados, this colony would be approximately 2 years old (23/1.2). The largest, specimen clearly derived from one individual propagule was 52 cm MLD, so not much older. The smallest was only 13 cm, so perhaps it is less than 6 months old. The 3 largest  colonies (specimens 1,5, 16 with MLDs of 190, 100, 62 cm appear to have involved fusion of 2 or more  separate colonies, so might be up to 5 years old, possibly younger. The largest colony was likely the founder colony,  others developing by asexual fragmentation from that colony or one of its early offspring.

Lewis, J.B. et al. 1968. Comparative Growth Rates of Some Reef Corals in the Caribbean. Available at http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA080111

Gladfelter, E.H. et al. 1978. Growth Rates of Five Reef-Building Corals in the Northeastern Caribbean. Bulletin of Marine Science,  28:. 728-734.Photo: A. prolifera Specimen #3 Scale is 30 cm. Estimated Maximum Linear Dimension:  34 cmPhoto: Specimen #4 Scale is 30 cm. Estimated Maximum Linear Dimension:  49 cmPhoto: A. prolifera Specimen #5 Scale is 30 cm. Estimated Maximum Linear Dimension: approx 100 cm. The colony extends from the scale bar at left to the white box at right and may have involved  fusion of 2 or more individual colonies. More detail in the next four photosPhoto: A. prolifera Specimen #5, section 1. Scale is 30 cm.Photo: A. prolifera Specimen #5, section 2. Scale (the red tie) is 30 cm.Photo: A. prolifera Specimen #5, section 3. Scale is 30 cm. It is not clear whether parts of the colony have been overgrown by Palythoa OR A. prolifera is growing through and displacing some of the Palythoa.Photo: A. prolifera Specimen #6. Scale is 30 cm. Estimated Maximum Linear Dimension: 52 cmPhoto: A. prolifera Specimen #6, closer view.Photo: A. prolifera Specimen #7. Scale is 30 cm. Estimated Maximum Linear Dimension: 50 cmPhoto: A. prolifera Specimen #8.   Scale is 30 cm. Estimated Maximum Linear Dimension: 49 cmPhoto: A. prolifera Specimen #9.   Scale is 30 cm. Estimated Maximum Linear Dimension: 35 cmPhoto: A. prolifera Specimen #10.   Scale is 30 cm. Estimated Maximum Linear Dimension: 26 cmPhoto: A. prolifera Specimen #11.   Scale is 30 cm. Estimated Maximum Linear Dimension: 42 cmPhoto: A. prolifera Specimen #12.   Scale is 30 cm. Estimated Maximum Linear Dimension: 44 cmPhoto: A. prolifera Specimen #13.   Scale is 30 cm. Estimated Maximum Linear Dimension: 24 cmPhoto: A. prolifera Specimen #14.   Scale is 30 cm. Estimated Maximum Linear Dimension: 23 cmPhoto: A. prolifera Specimen #15.   Scale is 30 cm. Estimated Maximum Linear Dimension: 38 cmPhoto: A. prolifera Specimen #16.   Scale is 30 cm. Estimated Maximum Linear Dimension: 62 cmPhoto: A. prolifera Specimen #16.  Likely some fusion of 2 or 3 individual coloniesPhoto: A. prolifera Specimen #17.   Scale is 30 cm. Estimated Maximum Linear Dimension: 13 cmPhoto: A. prolifera, Specimen 18. This specimen occurred in isolation, approximately 50 m shoreward of the other specimens. Estimated Maximum Linear Dimension: 24 cmPhoto: A new colony in 2016Photo: 2016: Several individual colonies had snagged fishing line (such fishing is illegal in the MPA)Photo: Loose fragment (2016)Photo: A. palmata, one of 2 specimens sighted in the Recreational Zone of the Barbados MPA. Scale is 30 cm. Estimated Maximum Linear Dimension: 14 cmPhoto: A. palmata, second of two specimens sighted in the recreational Zone of the Barbados MPA. Scale is 30 cm. Estimated Maximum Linear Dimension: 46 cmPhoto: A. cervicornis at approximately 30 ft depth in the Recreational Zone of the Barbados MPA.Photo: A. cervicornis at approximately 30 ft depth in the Recreational Zone of the Barbados MPA.Photo: A. cervicornis at approximately 30 ft depth in the Recreational Zone of the Barbados MPA.Photo: A. cervicornis at approximately 30 ft depth in the Recreational Zone of the Barbados MPA. I counted 30 discrete assemblages within an area of approx. 60 m diameter. The largest was ~ 5 m Maximimum Linear Dimension. Larger patches included older dead coral. Most or all coral in the smaller patches (circa 1 m and less) was living .Photo: Reef A is the area where A. palmata, A. cervicornis and A. prolifera described above were found. I have looked at Reefs B and C which are much more degraded than Reef A. Acropora palmata was found at at one site on Reef C, not on Reef B. No A. prolifera were observed on reefs B and C.Photo: A palmata on Reef C (April 1). Estimated Maximum Linear Dimension: 88 cmPhoto: Another view of A palmata on Reef CPhoto: A. palmata - one of two colonies sighted in the Scientific Zone of the Barbados MPA. Scale is 15 cm. Estimated Maximum Linear Dimension: 21 cm.Photo: A. palmata: a second specimen in the Scientific Zone of the Barbados MPA. Estimated Maximum Linear Dimension: 36 cm. Scale is 30 cm

I looked for but did not find A. cervicornis in the Scientific Zone, where it was once abundant. Nor did I find any A. prolifera.

It may be noteworthy that there are no large hotels dumping waste water in the area of the Recreational Zone (there are in the area of the Scientific Zone). However  developments are planned or occurring onshore of the Recreational Zone. I do hope that special precautions will be taken to ensure that effluents from such developments are not released into the nearshore environment. I would love to think that future generations of Bajans might enjoy some of the underwater beauty I was so privileged to enjoy in the 1960s - not to mention their significance to so many marine species!

A 2016 report by R. MacLean and H.A. Oxenford provides a comprehensive perspective on the current state of Acroporoids in Barbados. "A total of 46 fringing reefs were surveyed along the west coast of Barbados from Six Mens Bay in the north to Batts Rock in the south, from June 13th to August 22nd 2015, by free-divers. The GPS co-ordinates, appearance, condition and size of every Acropora spp. colony found were recorded. A total of 707 colonies, consisting of both A. palmata and A. prolifera, were found..." The Recreational Zone. identified as "Reef No 34" (Vauxhal), is apparently the only one where A cervicornis has been reported (citing this photoset), and most of the known colonies of A. prolifera occur at this site. 

CERMES Technical Report No 80
Mapping the return of acroporid corals on fringing reefs along the west coast of Barbados
R. MACLEAN AND H.A. OXENFORD
http://www.cavehill.uwi.edu/cermes/docs/technical_reports/maclean_oxenford_2016_mapping_recovery_acroporids_.aspx