Is Acropora Palmata recovering? A case study in Los Roques National Park, Venezuela

Eight years ago (2007), the distribution and status of Acropora palmata was quantified throughout Los Roques archipelago in Venezuela. The aim was to produce a baseline study for this species which combined population genetics with demographic data. The results highlighted that A. palmata had the potential to recover in at least 6 out of 10 sites surveyed. Recovery potential was assumed to be high at sites with a relatively high abundance of the coral, low disease prevalence, high genetic diversity, and high rates of sexual reproduction. However, as noted, Zubillaga et al. (2008) realized recovery was still strongly dependent on local and regional stressors. In 2014 (this study), the status of A. palmata was re-evaluated at Los Roques. We increased the number of sites from 10 in the original baseline study to 106. This allowed us to assess the population status throughout the entirety of the MPA. Furthermore, we also identified local threats that may have hindered population recovery. Here, we show that A. palmata now has a relatively restricted distribution throughout the park, only occurring in 15% of the sites surveyed. Large stands of old dead colonies were common throughout the archipelago; a result which demonstrates that this species has lost almost 50% of its original distribution over the past decades. The majority of corals recorded were large adults (∼2 m height), suggesting that these older colonies might be less susceptible or more resilient to local and global threats. However, 45% of these surviving colonies showed evidence of partial mortality and degradation of living tissues. Interestingly, the greatest increase in partial mortality occurred at sites with the lowest levels of protection (${X}_{o}^{2}=5.4> {X}_{c}^{2}=4.5$; df = 4, p {X}_{\mathrm{cri}}^{2}=1 5.5$; df = 8; p < 0.05) in the density of A. palmata in sites that had previously been categorized as having a high potential for recovery. One explanation for this continued decline may be due to the fact that over the past 10 years, two massive bleaching events have occurred throughout the Caribbean with records showing that Los Roques has experienced unprecedented declines in overall coral cover. We therefore conclude that although local protection could promote recovery, the impacts from global threats such as ocean warming may hamper the recovery of this threatened species

Corals of the génus Acropora of the lesser Antilles : génétics, écological and conservation approaches.

Les espèces coralliennes Acropora palmata (Lamarck, 1816) et A. cervicornis (Lamarck, 1816) ont un rôle majeur en termes de bio-construction et structuration des récifs dans la Caraïbe. Cependant, les populations de ces deux espèces sont en déclin et elles sont maintenant classées en danger critique d’extinction par l’Union Internationale de Conservation de la Nature (UICN). De récentes études principalement menées sur les récifs de la Floride et des Grandes Antilles se sont ainsi intéressé à la structure et à la dynamique des populations de ces espèces, mais le statut génétique des populations des Petites Antilles est moins connu.Le présent sujet a pour but d’étudier l’état des populations des coraux Acropora palmata et A. cervicornis sur les récifs de Guadeloupe et des Petites Antilles et d’élucider les mécanismes qui président à la survie de ces espèces et au recrutement des jeunes coraux.In the Caribbean, Acropora palmata (Lamarck 1816) and A. cervicornis (Lamarck 1816) are major coral species for reef building. Since the 80’s, these species populations are decreasing and are now classified as critically endangered species by the International Union for Conservation of Nature (IUCN). Recent studies, mainly conducted on the reefs of Florida and the Greater Antilles concerned the structure and the dynamics of Acropora populations, while the genetic status of the populations in the Lesser Antilles remains less studied. The purpose of the study is to determine the status of the coral populations of Acropora palmata and A. cervicornis on reefs of Guadeloupe and Lesser Antilles and to elucidate the mechanisms governing the survival of these species and the recruitment of young corals

Unexpected high densities of the hybrid coral Acropora prolifera (Lamarck 1816) in Guadeloupe Island, Lesser Antilles

International audienceUnexpected high densities of the hybrid coral Acropora prolifera (Lamarck 1816) in Guadeloupe Island, Lesser Antilles Since the 1980s, coral populations of Acropora palmata (Lamarck 1816) and A. cervicornis (Lamarck 1816) have dramatically declined in the Caribbean and have been consequently classified as critically endangered since 2008 (IUCN). Acropora palmata and A. cervicornis can form a viable F1 offspring previously described as A. prolifera by Lamarck (Vollmer and Palumbi 2002). Few isolated colonies of that morphotype have punctually been reported on Lesser Antilles reefs in the previous decades. In January 2013, high densities of morphologically identified A. prolifera colonies were observed in the Bay of Grand Cul-de-Sac Marin (16°21¢24.19 †N; 61°35¢35.12 †W, Guadeloupe Island, Lesser Antilles), whereas no colonies were found at this exact same site prospected in May 2011 (Fig. 1). Genetic microsatellite analyses (unpublished data) verified the hybrid nature of the colonies and suggest that they may constitute a single clone. However, in other Caribbean sites, Fogarty (2010) found high genotypic diversity for that hybrid. As a consequence of decreased parental species' density, eggs likely float unfertilized, increasing the probability of heterospecific sperm encounters and thus hybrid embryo formation (Fogarty et al. 2012). References Fogarty ND (2010) Reproductive isolation and hybridization dynamics in threatened Caribbean acroporid corals. Ph.D. thesis

Geographic distances and ocean currents influence Caribbean Acropora palmata population connectivity in the Lesser Antilles

The critically endangered coral species Acropora palmata used to dominate shallow Caribbean reefs but since the early 1980s, populations have dramatically declined. At the Caribbean scale, A. palmata is divided into two genetically divergent lineages and most of previous works investigating population connectivity among populations involved the western lineage (in Florida, the Bahamas, the Mesoamerican Reef System, and the Greater Antilles). Small scale genetic connectivity among A. palmata populations was globally found, possibly enhancing populations’ recovery at the local scale. Yet, little is known regarding the genetic connectivity of populations of the eastern lineage, especially those of the Lesser Antilles, a fragmented archipelago located at the edge of the species distribution. Here, we filled this gap by investigating the genetic diversity, population structure and connectivity of A. palmata populations among 36 sampled sites from 11 islands of the Lesser Antilles using 14 hypervariable microsatellite loci. Globally, genetic diversity levels in A. palmata populations from the Lesser Antilles were lower compared to what was previously reported within the Wider Caribbean. The analysis of the genetic structure, crossed with spatial autocorrelation analysis, revealed an isolation-by-distance pattern at both reef and Lesser Antilles scales. A gene dispersal distance of less than a kilometer, and a northward gene flow direction, in agreement with ocean surface currents in the region were found. Altogether, our results suggest a restricted population connectivity and short distance dispersal of A. palmata larvae within the Lesser Antilles further limited by geographic distances among suitable habitat patches. Additionally, our results suggest that southernmost populations are potential sources of larvae for the most northerly islands and have a key role in reseeding A. palmata populations of the Lesser Antilles

High clonality in Acropora palmata and Acropora cervicornis populations of Guadeloupe, French Lesser Antilles

Since the 1980s, population densities of Acroporidae have dramatically declined in the Caribbean Sea. Quantitative censuses of Acroporidae provide information on the number of colonies (i.e. ramets), but not on the number of genetically distinct individuals (i.e. genets). In this context, the aim of our study was to provide an overview of the genetic status of Acropora populations in Guadeloupe by examining the genotypic richness of Acropora palmata and Acropora cervicornis. Using 14 microsatellite loci, we found extremely low genotypic richness for both species from Caye-a-Dupont reef (i.e. 0.125 for A. palmata and nearly zero for A. cervicornis). Because genetic diversity contributes to the ability of organisms to evolve and adapt to new environmental conditions, our results are alarming in the context of ongoing global warming as long periods of clonal growth without sexual recruitment may lead to the extinction of these populations

Singular physiological behavior of the scleractinian coral Porites astreoides in the dark phase

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Porites astreoides throughout the Caribbean: the success of one or several species?

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Complex spatial patterns of genetic differentiation in the Caribbean mustard hill coral Porites astreoides

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Comment on ``Younger Dryas sea level and meltwater pulse 1B recorded in Barbados reefal crest coral Acropora palmata'' by N. A. Abdul et al

International audienceBased on new U-Th ages of corals drilled offshore Barbados, Abdul et al. (2016) have confirmed the existence of the abrupt stratigraphic feature called meltwater pulse 1B (MWP-1B), which they interpret as being due to a very large and global sea level step change dated at about 11.3 kyr before present (approximately 15 m and equivalent to twice the amount of water stored in the present Greenland ice sheet). This contrasts with the Tahiti record, in which MWP-1B is essentially absent or very small, as Carlson and Clark (2012) and Lambeck et al. (2014) also conclude in their recent reviews of deglacial sea levels at the global scale. However, the evidence provided by Abdul et al. and their main conclusions are not convincing as they are affected by the following three main problems, which may explain the apparent discrepancies: Problem #1/Barbados is located in a subduction zone, which was also active throughout the Late Glacial period. Furthermore, the Barbados cores studied by Abdul et al. were drilled on both sides of the extension of a tectonic feature identified at the southern tip of Barbados (South Point) as underlined by several studies of the Barbados stratigraphy. Problem #2/Fossil samples of Acropora palmata may not be reliable sea level markers during rapid and large sea level rises. Indeed, the asexual reproduction strategy of this species may not be optimal to keep up when the water depth is increasing very rapidly. This may in part explain why the living depth of A. palmata at Barbados was significantly greater than 5 m during some periods of the last deglaciation, notably between 14.5 and 14 kyr B.P. and possibly between 14 and 11.5 kyr B.P. Problem #3/The slow glacio-isostatic adjustment and the rapid responses due to gravitational changes of ice and water masses complicate the interpretation of individual relative sea level (RSL) records at specific locations. Therefore, the Barbados and Tahiti record cannot be compared directly in terms of absolute sea level values as done by Abdul et al. In addition, different glaciohydroisostatic adjustments at the two sites may also have contributed to the observed discrepancy between their deglacial RSL records