Porites Astreoides Research Articles

Coral larvae settle at a higher frequency on red surfaces

Although chemical cues serve as the primary determinants of larval settlement and metamorphosis, light is also known to influence the behavior and the settlement of coral planulae. For example, Porites astreoides planulae settle preferentially on unconditioned red substrata. In order to test whether this behavior was a response to color and whether other species also demonstrate color preference, settlement choice experiments were conducted with P. astreoides and Acropora palmata. In these experiments, larvae were offered various types of plastic substrata representing three to seven different color choices. Both species consistently settled on red (or red and orange) substrata at a higher frequency than other colors. In one experiment, P. astreoides settled on 100% of red, plastic cable ties but failed to settle on green or white substrata. In a second experiment, 24% of larvae settled on red buttons, more than settled on six other colors combined. A. palmata settled on 80% of red and of orange cables ties but failed to settle on blue in one experiment and settled on a greater proportion of red acrylic squares than on four other colors or limestone controls in a second experiment. The consistency of the response across a variety of plastic materials suggests the response is related to long-wavelength photosensitivity. Fluorescence and reflectance spectra of experimental substrata demonstrated that the preferred substrata had spectra dominated by wavelengths greater than 550 nm with little or no reflection or emission of shorter wavelengths. These results suggest that some species of coral larvae may use spectral cues for fine-scale habitat selection during settlement. This behavior may be an adaptation to promote settlement in crustose coralline algae (CCA)-dominated habitats facilitating juvenile survival.

Ocean acidification impacts multiple early life history processes of the Caribbean coral Porites astreoides

Ocean acidification (OA) refers to the increase in acidity (decrease in pH) of the ocean's surface waters resulting from oceanic uptake of atmospheric carbon dioxide (CO 2 ). Mounting experimental evidence suggests that OA threatens numerous marine organisms, including reef-building corals. Coral recruitment is critical to the persistence and resilience of coral reefs and is regulated by several early life processes, including: larval availability (gamete production, fertilization, etc.), larval settlement, postsettlement growth, and survival. Environmental factors that disrupt these early life processes can result in compromised or failed recruitment and profoundly affect future population dynamics. To evaluate the effects of OA on the sexual recruitment of corals, we tested larval metabolism, larval settlement, and postsettlement growth of the common Caribbean coral Porites astreoides at three pCO 2 levels: ambient seawater (380 μatm) and two pCO 2 scenarios that are projected to occur by the middle (560 μatm) and end (800 μatm) of the century. Our results show that larval metabolism is depressed by 27% and 63% at 560 and 800 μatm, respectively, compared with controls. Settlement was reduced by 42-45% at 560 μatm and 55-60% at 800 μatm, relative to controls. Results indicate that OA primarily affects settlement via indirect pathways, whereby acidified seawater alters the substrate community composition, limiting the availability of settlement cues. Postsettlement growth decreased by 16% and 35% at 560 and 800 μatm, respectively, relative to controls. This study demonstrates that OA has the potential to negatively impact multiple early life history processes of P. astreoides and may contribute to substantial declines in sexual recruitment that are felt at the community and/or ecosystem scale.

The impact of seawater saturation state and bicarbonate ion concentration on calcification by new recruits of two Atlantic corals

Rising concentrations of atmospheric CO2 are changing the carbonate chemistry of the oceans, a process known as ocean acidification (OA). Absorption of this CO2 by the surface oceans is increasing the amount of total dissolved inorganic carbon (DIC) and bicarbonate ion (HCO3−) available for marine calcification yet is simultaneously lowering the seawater pH and carbonate ion concentration ([CO32−]), and thus the saturation state of seawater with respect to aragonite (Ωar). We investigated the relative importance of [HCO3−] versus [CO32−] for early calcification by new recruits (primary polyps settled from zooxanthellate larvae) of two tropical coral species, Favia fragum and Porites astreoides. The polyps were reared over a range of Ωar values, which were manipulated by both acid-addition at constant pCO2 (decreased total [HCO3−] and [CO32−]) and by pCO2 elevation at constant alkalinity (increased [HCO3−], decreased [CO32−]). Calcification after 2 weeks was quantified by weighing the complete skeleton (corallite) accreted by each polyp over the course of the experiment. Both species exhibited the same negative response to decreasing [CO32−] whether Ωar was lowered by acid-addition or by pCO2 elevation—calcification did not follow total DIC or [HCO3−]. Nevertheless, the calcification response to decreasing [CO32−] was nonlinear. A statistically significant decrease in calcification was only detected between Ωar = <2.5 and Ωar = 1.1–1.5, where calcification of new recruits was reduced by 22–37% per 1.0 decrease in Ωar. Our results differ from many previous studies that report a linear coral calcification response to OA, and from those showing that calcification increases with increasing [HCO3−]. Clearly, the coral calcification response to OA is variable and complex. A deeper understanding of the biomineralization mechanisms and environmental conditions underlying these variable responses is needed to support informed predictions about future OA impacts on corals and coral reefs.

Population biology of Porites astreoides and Diploria strigosa on a shallow Caribbean reef

The detrimental impacts of anthropogenic disturbances on tropical coral reefs have been studied in detail, but there have been limited efforts to determine which corals might endure these adverse conditions. This study focused on 2 Caribbean corals that have survived better than most in recent years on shallow reefs (5 to 9 m depth) in St. John, US Virgin Islands, and it used demo- graphic models to explore their responses to disturbance. The species studied were Porites astreoides, which has weedy life-history characteristics, and Diploria strigosa, which is relatively non-weedy and in this location appears robust against environmental assaults. Populations were cen- sused on varying schedules from 1994 to 2007, and a tag-and-resurvey procedure for individual colonies was repeated annually between 1999 and 2007 (P. astreoides) or 2002 and 2007 (D. strigosa). The results were used to parameterize size-based matrix models (size classes: I, ≤40 mm; II, 41 to 80 mm; and III, ≥81 mm diameter), and bootstrap resampling was used to attach confidence intervals to population parameters and projections. In contrast to the declining population of the historically dominant coral Montastraea annularis in St. John, the intrinsic rate of population increase (λ) rose gradually for P. astreoides between 1999 and 2007. For D. strigosa, while λ behaved somewhat errat- ically from 2002 to 2007, the overall trend was also upward. For both species, λ was >1 at the end of the study, showing that the populations were growing. Over the next 100 yr, projections suggest that P. astreoides and D. strigosa will increase in abundance, even when impacted by recurrent distur- bances, variable recruitment, and varied success of the largest colonies; size-frequency distributions demonstrated that their populations will remain dominated by medium (>23 and >25%, respectively) and large (>20 and 24%, respectively) colonies, regardless of the conditions investigated. The suc- cess of P. astreoides and D. strigosa in St. John is strongly related to the dynamics of the largest colonies — notably their low mortality and high chance of remaining in the largest size class — and these characteristics favor sustained population growth in an era when many corals are declining in abundance. P. astreoides and D. strigosa now appear poised to experience a period of enhanced abundance on reefs in at least one Caribbean location.

Coral mass bleaching and reef temperatures at Navassa Island, 2006

Bleaching and associated mortality is an extreme threat to the persistence of coral populations in the projected warming regime of the next few decades. Recent evidence indicates that thermal bleaching thresholds may be affected by water quality gradients. The unexpected encounter of a coral mass bleaching event at a remote, uninhabited Caribbean island (Navassa) during a routine reef assessment cruise in November 2006 provided the opportunity to characterize bleaching responses and thermal exposure in an oceanic area with negligible continental influence or human impact on water quality. The coral taxa most susceptible to bleaching were Agaricia spp. and Montastraea faveolata. Siderastraea siderea, Diploria spp. and Porites porites were intermediately affected, while Porites astreoides and Montastraea cavernosa were minimally affected and negligible bleaching was observed in Acropora palmata. Bleaching prevalence (colonies > 4 cm diameter) ranged from 0.16 to 0.63 among sites. Deeper sites (between 18 and 37 m) had significantly higher prevalence of bleaching than shallow sites (<10 m). This general pattern of more bleaching in deeper sites also occurred within species. Though exposure to high-temperature stress was not greater at deeper sites, water motion, which may bolster bleaching resistance, was likely less. In situ loggers indicated temperatures over 30 °C initiated at shallow sites in mid-August, at deeper sites in early September, and were persistent at all sites until mid-October. Long term (1983–2007) climatologies constructed from AVHRR SSTs suggest that the mass bleaching event observed at Navassa in 2006 corresponded with greater intensity and duration of warm temperature anomalies than occurred in 2005, for which no in situ observations (bleaching nor temperature) are available.

Implications of coral harvest and transplantation on reefs in northwestern Dominica.

In June, 2002, the government of Dominica requested assistance in evaluating the coral culture and transplantation activities being undertaken by Oceanographic Institute of Dominica (OID), a coral farm culturing both western Atlantic and Indo-Pacific corals for restoration and commercial sales. We assessed the culture facilities of OID, the condition of reefs, potential impacts of coral collection and benefits of coral transplantation. Coral reefs (9 reefs, 3-20 m depth) were characterized by 35 species of scleractinian corals and a live coral cover of 8-35%. Early colonizing, brooders such as Porites astreoides (14.8% of all corals), P. porites (14.8%), Meandrina meandrites (14.7%) and Agaricia agaricites (9.1%) were the most abundant corals, but colonies were mostly small (mean = 25 cm diameter). Montastraea annularis (complex) was the other dominant taxa (20.8% of all corals) and colonies were larger (mean = 70 cm). Corals (pooled species) were missing an average of 20% of their tissue, with a mean of 1.4% recent mortality. Coral diseases affected 6.4% of all colonies, with the highest prevalence at Cabrits West (11.0%), Douglas Bay (12.2%) and Coconut Outer reef (20.7%). White plague and yellow band disease were causing the greatest loss of tissue, especially among M. annularis (complex), with localized impacts from corallivores, overgrowth by macroalgae, storm damage and sedimentation. While the reefs appeared to be undergoing substantial decline, restoration efforts by OlD were unlikely to promote recovery. No Pacific species were identified at OID restoration sites, yet species chosen for transplantation with highest survival included short-lived brooders (Agaricia and Porites) that were abundant in restoration sites, as well as non-reef builders (Palythoa and Erythropodium) that monopolize substrates and overgrow corals. The species of highest value for restoration (massive broadcast spawners) showed low survivorship and unrestored populations of these species were most affected by biotic stressors and human impacts, all of which need to be addressed to enhance survival of outplants. Problems with culture practices at OID, such as high water temperature, adequate light levels and persistent overgrowth by macroalgae could be addressed through simple modifications. Nevertheless, coral disease and other stressors are of major concern to the most important reef builders, as these species are less amenable to restoration, collection could threaten their survival and losses require decades to centuries to replace.

Growth characteristics of the reef-building coral Porites astreoides under different environmental conditions in the Western Atlantic

Skeletal extension (3.67 ± 0.65 mm year−1), density (1.49 ± 0.16 g cm−3), and calcification rate (0.55 ± 0.12 g cm−2 year−1) were determined using annual growth bands of Porites astreoides skeletons collected in three different reef systems in the Western Atlantic. The corals showed a low-density annual growth band at their apex, and seasonal timing of low and high-density band formation in P. astreoides appears to be similar at the three study sites in the Western Atlantic. The range of values presented here, for the three growth variables, spans the known range of skeletal-growth variability in P. astreoides for the Western Atlantic. The relationships between the growth parameters were similar to those previously described by other authors for massive Porites species from the Indo-Pacific, suggesting that P. astreoides has the same growth strategy, primarily investing calcification resources in extension rate. It is noteworthy that the P. astreoides population growing off the northwest coast of Cuba had similar growth characteristics as populations from the Caribbean region which were different from populations in the Gulf of Mexico, which seem to be isolated and adapted for growth at higher average sea-surface temperatures.

The effects of substratum type on the growth, mortality, and photophysiology of juvenile corals in St. John, US Virgin Islands

Coral larvae are selective with regards to the surfaces upon which they settle, but little is known about the outcome of these choices. In this study, we explored the implications for juvenile scleractinians (< 40-mm diameter) of growing on igneous versus carbonate rock on the shallow reefs (5-m depth) of St. John, US Virgin Islands. Surveys revealed that juvenile corals occurred at densities of 16 colonies m − 2 and were distributed on igneous and carbonate rocks in proportion to the abundance of these surfaces, suggesting that larvae do not discriminate between rock types at settlement. Repeated surveys demonstrated that all juvenile corals (i.e., pooled among taxa) grew 41% slower on igneous versus carbonate rock between January and August, but not between August and January when the growth was statistically indistinguishable between rock types. Although the growth of the most common juvenile coral, Porites astreoides, was similar on both substrata, the photophysiology of this species was affected by the type of rock. The maximum relative electron transfer rate (rETR, a proxy for photosynthesis) of P. astreoides was down-regulated 30% on igneous compared to carbonate rock. Phylogenetic analyses of the Symbiodinium community sequence profiles within P. astreoides revealed significant differences between substrata, with a greater diversity of co-occurring ITS-2 sequences in corals growing on carbonate compared to igneous rock. While substratum-dependent patterns in the characteristics of juvenile corals suggested there is selective value to the settlement choices made by larvae, these trends did not translate into differences in survival, at least over the time scale investigated. It remains uncertain what features of the rocks affected coral performance, but differences in the temperature of the rock may be an important feature during the warmest period of the year.

The effect of species and colony size on the bleaching response of reef-building corals in the Florida Keys during the 2005 mass bleaching event

Understanding the variation in coral bleaching response is necessary for making accurate predictions of population changes and the future state of reefs in a climate of increasing thermal stress events. Individual coral colonies, belonging to inshore patch reef communities of the Florida Keys, were followed through the 2005 mass bleaching event. Overall, coral bleaching patterns followed an index of accumulated thermal stress more closely than in situ temperature measurements. Eight coral species (Colpophyllia natans, Diploria strigosa, Montastraea cavernosa, M. faveolata, Porites astreoides, P. porites, Siderastrea siderea, and Stephanocoenia intersepta), representing >90% of the coral colonies studied, experienced intense levels of bleaching, but responses varied. Bleaching differed significantly among species: Colpophyllia natans and Diploria strigosa were most susceptible to thermal stress, while Stephanocoenia intersepta was the most tolerant. For colonies of C. natans, M. faveolata, and S. siderea, larger colonies experienced more extensive bleaching than smaller colonies. The inshore patch reef communities of the Florida Keys have historically been dominated by large colonies of Montastraea sp. and Colpophyllia natans. These results provide evidence that colony-level differences can affect bleaching susceptibility in this habitat and suggest that the impact of future thermal stress events may be biased toward larger colonies of dominant reef-building species. Predicted increases in the frequency of mass bleaching and subsequent mortality may therefore result in significant structural shifts of these ecologically important communities.

Topography and spatial arrangement of reef-building corals on the fringing reefs of North Jamaica may influence their response to disturbance from bleaching

Knowledge of factors that are important in reef resilience helps us understand how reefs react following major environmental disturbances such as hurricanes and bleaching. Here we test factors that might have influenced Jamaican reef resilience to, and subsequent recovery from, the 2005 bleaching event, and which might help inform management policy for reefs in the future: reef rugosity and contact of corals with macroalgae. In addition, we test in the field, on Dairy Bull reef, whether aggregated Porites astreoides colonies exhibit enhanced growth when exposed to superior competition from Acopora palmata, as has been found by experiment with the Indo-Pacific corals Porites lobata and the superior competitor Porites rus [Idjadi, J.A., Karlson, R.H., 2007. Spatial arrangement of competitors influences coexistence of reef-building corals. Ecology 88, 2449-2454]. There were significant linear relationships between rugosity and the increase in smallest size classes for Sidastrea siderea, Colpophyllia natans, P. astreoides and Agaricia species, and between rugosity and cover of the branching coral Acropora cervicornis. Linear extension rates of A. cervicornis and radial growth rates of P. astreoides were significantly lower (p<0.025; F>6) when in contact with macroalgae. Aggregated colonies of P. astreoides in contact with one another, one of which was in contact with the faster growing competitor A. palmata showed significantly greater growth rates than with just two aggregated P. astreoides colonies alone. These findings suggest that three dimensional topography and complexity is important for reef resilience and viability in the face of environmental stressors such as bleaching. Our findings also support the idea that aggregated spatial arrangements of corals can influence the outcome of interspecific competition and promote species coexistence, important in times of reef recovery after disturbance.

Effects of the Florida red tide dinoflagellate, Karenia brevis, on oxidative stress and metamorphosis of larvae of the coral Porites astreoides

Florida red tides, caused by the dinoflagellate Karenia brevis, produce a series of neurotoxins, brevetoxins, which have historically had a negative impact on coastal communities along the South Florida coast. While much work has examined the effects of K. brevis blooms or exposure to brevetoxins on a diverse array of marine organisms, there have been no reports studying the impact of K. brevis on coral physiology. We provide evidence that short-term exposure of naturally occurring concentrations of K. brevis and their associated toxins can induce oxidative stress in the coral larvae of Porites astreoides. Larvae of P. astreoides were exposed to aliquots of intact K. brevis cells at naturally occurring concentrations (6 × 10 5 – 4 × 10 6 cells L −1) or cellular lysates (containing 5.4–15.0 μg L −1 brevetoxin) for 20 h and a variety of larval physiological biomarkers were measured. In the presence of bloom scale concentrations of K. brevis larval respiration of P. astreoides was inhibited. This was accompanied with an increase in lipid hydroperoxide content and catalase activity indicating oxidative damage and a subsequent antioxidant response were occurring. However, when larvae were exposed to intact cells of K. brevis or their sonicated, lysed exudates stress indices including zooxanthellae expulsion (bleaching), larval protein carbonylation, and superoxide dismutase activity were not significantly altered. Even though there was evidence for short-term oxidative stress in larvae that were exposed to K. brevis there was no change in survival or settlement rates of larvae of P. astreoides.

Nutrient versus herbivore control of macroalgal community development and coral growth on a Caribbean reef

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 389:71-84 (2009) - DOI: https://doi.org/10.3354/meps08142 Nutrient versus herbivore control of macroalgal community development and coral growth on a Caribbean reef Deron E. Burkepile1,2,*, Mark E. Hay1 1Georgia Institute of Technology, School of Biology, 310 Ferst Drive, Atlanta, Georgia 30332, USA 2Present address: Marine Sciences Program, Department of Biological Sciences, Florida International University, 3000 NE 151st Street, North Miami, Florida 33181, USA *Email: deron.burkepile@fiu.edu ABSTRACT: Coral reefs are in global decline, with seaweeds replacing corals as spatial dominants. Overfishing of herbivores, anthropogenic eutrophication, and interactions between these factors have been postulated as causes, but long-term tests of these factors are uncommon. We factorially manipulated herbivorous fishes and nutrients at a depth of 16 to 18 m for 7 to 10 mo in 2 experiments over 2 yr. Herbivore exclusion increased algal cover by about 4 to 10×, algal biomass by 4 to 6×, and suppressed cover of crustose coralline algae by 80 to 100%. Nutrient enrichment had no effect on the cover or mass of upright algae, but altered species composition by suppressing cyanobacteria and facilitating red macroalgae in the absence of herbivores. Nutrient addition increased macroalgal species richness in the absence, but not the presence of herbivores. Feeding by herbivorous fishes increased by 3 to 13× on nutrient-enriched vs. control plots. This herbivory facilitated cover of crustose coralline algae, demonstrated that herbivores selectively target more nutritional prey, and suggested that herbivores could suppress macrophyte accumulation at sites with increased nutrient availability. Effects of fishes and nutrients on corals varied as a function of coral species. For the branching coral Porites porites, 56% of individuals exposed to fishes were completely consumed; however, individuals that survived grew 60 to 80% more in the presence of fishes. For Porites astreoides, exposure to fishes did not affect mortality, but increased net growth by 3 to 4 times. For this coral, nutrient addition decreased growth when exposed to fishes but not when protected from fishes, suggesting that fishes may have fed more on nutrient-enriched corals. KEY WORDS: Eutrophication · Overfishing · Parrotfish · Selective grazing · Surgeonfish · Plant–herbivore interactions Full text in pdf format PreviousNextCite this article as: Burkepile DE, Hay ME (2009) Nutrient versus herbivore control of macroalgal community development and coral growth on a Caribbean reef. Mar Ecol Prog Ser 389:71-84. https://doi.org/10.3354/meps08142Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 389. Online publication date: September 04, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Herbivory versus corallivory: are parrotfish good or bad for Caribbean coral reefs?

With coral cover in decline on many Caribbean reefs, any process of coral mortality is of potential concern. While sparisomid parrotfishes are major grazers of Caribbean reefs and help control algal blooms, the fact that they also undertake corallivory has prompted some to question the rationale for their conservation. Here the weight of evidence for beneficial effects of parrotfishes, in terms of reducing algal cover and facilitating demographic processes in corals, and the deleterious effects of parrotfishes in terms of causing coral mortality and chronic stress, are reviewed. While elevated parrotfish density will likely increase the predation rate upon juvenile corals, the net effect appears to be positive in enhancing coral recruitment through removal of macroalgal competitors. Parrotfish corallivory can cause modest partial colony mortality in the most intensively grazed species of Montastraea but the generation and healing of bite scars appear to be in near equilibrium, even when coral cover is low. Whole colony mortality in adult corals can lead to complete exclusion of some delicate, lagoonal species of Porites from forereef environments but is only reported for one reef species (Porites astreoides), for one habitat (backreef), and with uncertain incidence (though likely <<10%). No deleterious effects of predation on coral growth or fecundity have been reported, though recovery of zooxanthellae after bleaching events may be retarded. The balance of evidence to date finds strong support for the herbivory role of parrotfishes in facilitating coral recruitment, growth, and fecundity. In contrast, no net deleterious effects of corallivory have been reported for reef corals. Corallivory is unlikely to constrain overall coral cover but contraints upon dwindling populations of the Montastraea annularis species complex are feasible and the role of parrotfishes as a vector of coral disease requires evaluation. However, any assertion that conservation practices should guard against protecting corallivorous parrotfishes appears to be unwarranted at this stage.

High spatial variability of coral, sponges and gorgonian assemblages in a well preserved reef

The main goal of this research was to obtain baseline field data of the composition of sponges, corals, and gorgonian assemblages that can be used as a reference for future analyses of anthropogenic impact. We tested the hypothesis that relatively homogeneous and well preserved reef units can present notable natural variability in the composition of their communities which are unassociated with changes in land proximity or a human impact gradient. Research was carried out in July 2006 at Los Colorados reef, located in the northwestern region of Pinar del Río Province, Cuba at 12 sampling stations. The biotopes selected were crest, terrace edge and spur and grove. Ecological indicators were diversity of corals, species composition, density of corals, hydrocorals, gorgonians and sponges, and density of selected coral species. A total of 2659 colonies of scleractineans corals representing 36 species were counted. The most abundant species in the crest biotope were Millepora alcicornis, Acropora palmata and Porites astreoides; in the terrace edge and spur and grove, the most abundant species were Siderastrea siderea, Stephanocoenia intersepta, Porites astreoides, Agaricia agaricites and Montastraea cavernosa. We found differences among sites for several indicators (e.g. density of corals, sponges and gorgonians and for selected species), but they could not be associated to any gradient of land influence or human impact. Therefore, sites inside a relatively homogeneous reef unit can present notable natural differences in the composition of their communities.

Reef waters stimulate substratum exploration in planulae from brooding Caribbean corals

This study tested the hypothesis that waters surrounding reefs with healthy coral populations are more likely than degraded sites to induce planulae to navigate downward and begin benthic probing. In the laboratory, larvae from two brooding Caribbean coral species, Agaricia tenuifolia and Porites astreoides, were introduced to seawater collected at (1) 1 m above shallow, healthy reef with high-coral cover, (2) 1 m above shallow, degraded reef with high-macroalgal cover, and (3) ~400 m ocean-ward of the reef in deep, blue water. Counter to the hypothesis, water from both the healthy and degraded reef caused the larvae to swim downward and begin benthic probing. These results suggest that substances carried in reef waters may contribute to macro-scale habitat selection by planulae and that understanding how these waterborne cues mesh with other stimuli used by planulae to select a settlement site may be valuable for deciphering a site’s recruitment potential for corals.

Thermal stress assessment using carbon and oxygen isotopes from Scleractinia, Rocas Atoll, northeastern Brazil

More than 430 C and O isotope analyses were carried out on carbonates from six coral species collected during June 1995, July 1998 and February 1999 at Rocas atoll, offshore northeastern Brazil: Siderastrea stellata Verrill 1868, Porites branneri Rathbum 1887, Porites astreoides Lamarck 1816, Mussismilia hispida Verrill 1902, Madracis decactis Lyman 1859 and Montastrea cavernosa Linnaeus 1886. Samples were collected in pools within the ring of the atoll, at water depths from 1.0 to 7.0 m. Oxygen isotope chemistry demonstrated that the studied species experienced several periods of bleaching; calculated temperature for one species vary, suggesting important changes within the time scale of coral growth. The species P. branneri, P. astreoides, M. cavernosa and the Brazilian endemic species M. hispida registered temperature variations during coral growth more accurately than did S. stellata and M. decactis. Carbon isotope behaviour in coral skeletons of the species examined at this atoll seems to have maintained a close relationship between density and/or zooxanthelar productivity: the greater the algal density, the heavier the δ13C values in skeletons.

Chemical contamination in southwest Puerto Rico: A survey of contaminants in the coralPorites astreoides

Coral (Porites astreoides) from eight sites in southwest Puerto Rico were analyzed for approximately 150 chemical contaminants, to provide a preliminary characterization of environmental contamination in the corals, and assess the relationships between chemical contamination in corals and adjacent sediments. Overall, the concentration of PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls) detected in the limited number of coral samples collected were comparable to concentrations found in sediments. However, the concentration of a chemical contaminant (e.g., PAHs) in the corals at a site was often different from what was found in adjacent sediments. The level of PCBs and DDT (dichlorodiphenyltrichloroethane) in the corals appeared higher just outside of Guanica Bay, and there was some evidence of a downstream concentration gradient for these two contaminant classes. The trace elements copper and zinc were frequently detected in Porites astreoides, and the concentrations were usually comparable to those found in adjacent sediments. Chromium was an exception in that it was not detected in any of the coral samples analyzed, although it was detected in all of the sediment samples.

Spatial and temporal variability in juvenile coral densities, survivorship and recruitment in La Parguera, southwestern Puerto Rico

Juvenile coral survivorship (the proportion of juvenile colonies surviving from t1 to t2) was assessed by counting, photographing and mapping all juveniles found in 2003 within random permanent 0.25m2 quadrats at four depth intervals at each of four inshore and mid-shelf reefs and at deeper habitats (>18m) in two shelf-edge reefs (N=96/reef) in La Parguera, southwest coast of Puerto Rico. Quadrats were resurveyed and photographed in 2005 to evaluate surviving juveniles, mortality and new recruits. Total number of juveniles dropped from 718 in 31 scleractinian species in 2003 to 396 in 28 species in 2005, an average juvenile survivorship of 54.8%. Mean juvenile density decreased from 1.2 (± 0.06) colonies/0.25 m2 in 2003 to 0.7 (± 0.05) colonies/0.25 m2 in 2005. Juvenile coral composition, relative abundances, survivorship and recruitment varied significantly across depth intervals within reefs and among reefs. Some species with high relative abundances in 2003 showed high survivorship in 2005 [Siderastrea siderea (28.3% and 65% respectively), Porites astreoides (15.1% and 55.6%), and Diploria strigosa (7.5% and 45.2%)]. Other taxa had relative low abundances but high survivorship [Montastraea cavernosa (4.6% and 66.7%) and Stephanocoenia intersepta (4.6% and 48.3%)]. Survivorship was significantly higher in deeper habitats at three of the four fringing reefs. Furthermore, the semi-exposed inshore, highly sedimented reefs, showed higher juvenile survivorship than the mid-shelf and shelf-edge reefs. There was no clear relationship between survivorship and reproductive mode (brooding vs. broadcast spawning) of sexual reproduction. Overall, only 78 new recruits were found in 2005.

Community involvement in management for maintaining coral reef resilience and biodiversity in southern Caribbean marine protected areas

Climate change is posing new challenges to conservation because management policies on protected coral reefs are less effective than they were before the current ecosystem degradation. Coral reefs, the most diverse and complex marine ecosystem provide economic services for millions, but are seriously threatened worldwide because reef-building corals are experiencing bleaching phenomena and a steady decline in abundance. The resources of a Marine Protected Area (MPA) in Cartagena, Colombia, are in constant decline, despite a current management plan and on-site staff, urging new conservation actions. A multidisciplinary team gathered to evaluate management effectiveness including biophysical, socioeconomic and governance indicators. Coral cover and fish diversity and abundance were low both inside and outside the MPA, which suggests a limited efficiency of management. Currently, the MPA is a reef with low coral cover and high algae cover as well as large dead coral areas, which are generally signs of highly degraded reef habitats. Live coral cover in the MPA was represented by pioneer coral species such as Agaricia tenuifolia and Porites astreoides. Nonetheless, 35% of the scleractinian species sampled in the area harbored more than one zooxanthellae symbiont, which suggests potential resistance and resilience against coral bleaching. Maintenance of trophic structure and functional diversity is an important endeavor that should be a priority for management in order to allow ecosystem resilience. Social and governance indicators showed low-income levels and few opportunities for communities living in and around the park, low governability, weak communication among stakeholders and with authorities at different levels. As a result, problems related to over exploitation of resources were commonplace in the MPA. These results reflect low adaptive capacity of communities to comply with restrictive conservation rules, showing that establishment of a protected area is a necessary but insufficient condition to guarantee conservation goals. Ignoring the role of local communities only will exacerbate the problems associated with natural resources. Involvement of communities in strategic ecosystems management appears to be a requisite to improve effectiveness of protected areas, and participatory strategies, such as co-management, offer opportunities to improve governability while letting communities adapt to MPA needs.

Branqueamento de corais nos recifes da Bahia e sua relação com eventos de anomalias térmicas nas águas superficiais do oceano

A partir de 1993 foram registrados vários eventos de branqueamento de coral na Bahia, com recuperação total dos corais afetados. O primeiro registro ocorreu em Abrolhos no verão de 1993/1994, quando o percentual de colônias branqueadas variou entre 50 e 90%. No verão de 1997/1998, ocorreu no Litoral Norte da Bahia uma anomalia térmica de 1 ºC, com temperaturas medidas no campo de 29 a 30,5 ºC, o que causou branqueamento em 60% dos corais. De 1998 a 2005, foi observado que nos recifes costeiros, localizados muito próximos (&lt;5km) ou adjacentes à costa, a permanência de anomalias térmicas de 0,25 ºC por mais de duas semanas causou branqueamento em mais de 10% dos corais. Porém para os recifes de Abrolhos, localizados a mais de 10 km da costa, apenas anomalias acima de 0,50 ºC com duração de mais de duas semanas causaram branqueamento em mais de 10% dos corais. Mussismilia hispida, Siderastrea spp., Montastraea cavernosa, Agaricia agaricites e Porites astreoides foram as espécies de coral mais afetadas pelo branqueamento e são as espécies mais freqüentes nos recifes costeiros. Todas as espécies apresentaram graus diferentes de branqueamento, "fraco" ou "forte". Nos recifes da Bahia há uma forte relação entre o branqueamento de corais e os eventos de anomalias da temperatura da superfície do mar (TSM), e os recifes mais afetados pelo branqueamento foram os recifes costeiros. Estes recifes localizados muito próximos da costa estão mais expostos aos efeitos dos impactos provenientes de processos que ocorrem na região costeira, sugerindo que, muito provavelmente, os corais mais expostos a níveis elevados de nutriente e sedimento, e variações sazonais mais altas da TSM, podem já estarem mais resistentes aos efeitos pós branqueamento como, por exemplo, doenças infecciosas e mortalidade em massa.