Porites Astreoides Research Articles

Diversity and distribution of coral-associated bacteria

Coral reefs are the most biodiverse of all marine ecosystems; however, very little is known about prokaryotic diversity in these systems. To address this issue, we sequenced over 1000 bacterial 16S rDNAs from 3 massive coral species (Montastraea franksi, Diploria strigosa, and Porites astreoides) in Panama and Bermuda. Analysis of only 14 coral samples yielded 430 distinct bacterial ribotypes. Statistical analyses suggest that additional sequencing would have resulted in a total of 6000 bacterial ribotypes. Half of the sequences shared <93% identity to previously published 16S sequences, and therefore probably represent novel bacterial genera and species; this degree of novelty was substantially higher than that observed for other marine samples. Samples from the Panama corals were more diverse than those from Bermuda, paralleling diversity gradients seen in metazoans. The coral-bacteria associations were non-random. Different coral species had distinct bacterial communities, even when physically adjacent, while bacterial communities from the same coral species separated by time (~1 yr) or space (3000 km) were similar. Analysis of the branching coral Porites furcata showed that bacterial ribotypes can also be structured spatially within colonies. Therefore, corals and reefs represent landscapes of diverse, ecologically structured prokaryotic communities.

The biology of larvae from the reef coral Porites astreoides , and their response to temperature disturbances

Pelagic larvae play a fundamental role in the life history of virtually all scleractinian corals, yet much of their biology remains unexplored. One aspect of coral larvae – their response to temperature perturbations – has potentially important consequences for understanding the effects of global warming and El Nino–Southern Oscillation events on coral recruitment. The present study tests the effects of temperature perturbations on coral larvae using Porites astreoides larvae as a model system. In June 1999, larvae were collected from 18 m depth on Conch Reef, Florida, and incubated at ambient (28°C), depressed (26°C), and elevated (33°C) temperatures in outdoor tanks shaded from direct sunlight. Treatments were repeated with new larvae every 24 h, and treatment effects quantified as larval motility, mortality, metamorphosis and metabolism. Elevated temperature significantly increased mortality and metamorphosis, and a similar trend was observed at the reduced temperature, although this was not significant. Neither elevated nor reduced temperatures affected larval motility. Gross photosynthesis (P) was significantly depressed by elevated and reduced temperatures, and respiration (R) varied proportionately with temperature (Q 10≈2), although this effect was not statistically significant. At the highest temperature the P/R ratio declined to <1, indicating that thermal stress reduces the potential for autotrophy. Together, these results suggest that elevated temperatures affect coral larvae by depressing photosynthesis and creating an energy shortage, which ultimately could reduce recruitment (by increasing mortality), shorten larval longevity and favor premature metamorphosis. An unexpected finding was that larvae differed physiologically among release dates. Although preliminary, this suggests that larval fitness in Porites spp. may vary depending on the day of release, a phenomenon that could have significant ramifications with respect to the population structure of adults.

Metal Content on the Reef Coral Porites astreoides: an Evaluation of River Influence and 35 Years of Chronology

Ten metals (Al, Ca, Cd, Cu, Cr, Fe, Hg, Pb, V and Zn) were analysed in skeletal sections of the coral Porites astreoides. Each skeletal section comprised five years of growth, and a total of 35 years of carbonate deposition was analysed from 1960 to 1995. The skeletal sections were determined through the analysis of growth bands using tomography. The corals were taken from two localities that differ in their sedimentation rate and closeness to river inputs that were considered as factors that could lead to differences in coral metal content. The concentration of most metals did not differ throughout the period of time analysed. This, together with the fact that most metals showed concentrations higher than others reported for pristine locations in the Caribbean, suggests a relatively chronic contamination of the study site established at least since 1960 for the metals analysed. Only the skeletal content of Al, Fe, Cr and Ca differed significantly between localities: (a) corals from the locality closer to the river inputs had a greater concentration of Al and Fe; (b) the difference in Cr was only due to an increased concentration in one colony, although detectable in 3 skeletal sections (15 years), and; (c) the skeletal Ca difference could be associated with different growth rates between localities.

Epibiotic and free-living Porites astreoides

Epibiotic and free-living Porites astreoides

Timing of larval release by Porites astreoides in the northern Florida Keys

Annual and lunar patterns of larval release by the coral Porites astreoides in the Florida Keys were investigated. Corals were collected monthly and maintained in outdoor, flow-through systems to quantify nightly release of larvae. Planulae were released during a period from 10 days prior to the new moon through 11 days after the new moon, with a peak in release centered on the new moon. The average duration of larval release by a single colony was 9 nights. Although the correlation was low (r=0.292), there was a positive relationship between colony size and number of larvae released. The majority of larval release occurred in April and May, although smaller numbers of larvae were observed from June through as late as September. Larval release appeared to be correlated with the average water temperatures over the 30 days prior to the new moon, peaking when water temperatures were 24.5–27.5 °C.

Self-fertilization in brooding hermaphroditic Caribbean corals: Evidence from molecular markers

The occurrence of self-fertilization in natural populations of hermaphroditic marine invertebrates has seldom been documented. This is in contrast to plant systems where studies of self-fertilization dominate plant mating system literature. Randomly amplified polymorphic DNA markers were used to assess rates of natural self-fertilization in two common hermaphroditic Caribbean corals from the Florida Keys, Favia fragum and Porites astreoides. Rates of self-fertilization in the field were found to be high (34% for P. astreoides and 49% for F. fragum) indicating that selfing is an important mode of reproduction for both species. Furthermore, rates of selfing were found to be significantly heterogeneous among individuals for both species and between sites for P. astreoides; thus, both species exhibit a mixed mode of mating ranging from complete outcrossing to nearly complete selfing. These results suggest that corals and other marine invertebrates may provide a rich source of comparative data for testing evolutionary theories of selfing that have primarily been developed through studies of plant mating systems.

Relationship between light and the δ15 N of coral tissue: Examples from Jamaica and Zanzibar

Nitrogen isotope values from coral tissue collected over depth–light gradients are reported from Jamaica and Zanzibar. The Jamaica suite consists of multiple specimens of three coral species (Montastrea annularis, Porites astreoides, and Agaricia agaricites) sampled at increasing depths. For each species, combined tissue/zooxanthellae δ15N decreases significantly with decreasing availability of photosynthetically active radiation. The Zanzibar sample suite was collected from three coral colonies (all Porites lobata). Multiple samples, occupying different depths and light regimes, were collected from each coral corallum. The Zanzibar suite shows a significant decrease in δ15N over the relatively small depth range represented by each coral colony. Together, these two sample suites suggest that light is an influence on the nitrogen isotopic composition in corals containing symbiotic zooxanthellae. We propose that in high-irradiance conditions, uptake and assimilation of dissolved inorganic nitrogen (DIN) by symbiotic algae and(or) the host strongly depletes the coral internal DIN pool, leading to reduced fractionation relative to reef DIN. In lower light conditions, less dissolved nitrogen is assimilated and fractionation increases. The autotrophic portion of the diet is thought to be sufficiently abundant in nitrogen and isotopically depleted to result in lower δ15N of host tissues under lower light conditions.

Coral injury and recovery: matrix models link process to pattern

In corals, extant damage to colonies depends on the balance between injury and recovery rates. Sclerochronology — the study of scleractinian coral growth rings — provides information about these historical processes, since corals preserve traces of previous injuries and annual bands representing regrowth. Cross-sections of two Caribbean coral species, Porites astreoides (Ellis and Solander) and Siderastrea siderea Le Sueur, were examined to determine the size-frequency and incidence of partial mortality and the rate at which these injuries recover. Each year's injuries were divided into four size classes, and subsequent changes in lesion size were developed into probabilities of switching size classes each year. Matrix models, composed of a matrix of transition probabilities and a vector added annually to account for new damage, predicted a dynamic equilibrium of extant damage to corals that matches field censuses well. A census of corals was carried out at two ( P. astreoides) or five ( S. siderea) sites. In 23 of 28 comparisons, values of extant damage were within the 95% confidence intervals of model predictions. Discrepancies arose because the model underestimated small lesions in P. astreoides. Sclerochronology may fail in this instance because small, rapidly-recovering injuries do not leave permanent scars in coral skeleton, although they are common in point observations of reef damage. Based on sclerochronology, P. astreoides and S. siderea are differentially susceptible to injury, and P. astreoides tends to recover more rapidly.

Human osteoprogenitor responses to orthopaedic implant: mechanism of cell attachment and cell adhesion

Cell culture models are becoming prevalent in the investigation of tissue responses to implant materials. Cellular attachment and cell adhesion studies can aid in the development of more effective orthopaedic and dental implants. Cell attachment was studied on extracellular matrix proteins (type I, IV collagen, peptide solubilized elastin (PSE), fibronectin laminin). Human osteoprogenitor cells responded differently to these collagenous and non-collagenous proteins. PSE and type I or type IV collagen are the most effective proteins in cellular attachment and cell spreading. Cell behaviour was measured in the presence of macroporous materials (Porites astreoides from the West Indies and a bovine hydroxyapatite ceramic ENDOBON®) and bioartificial connective matrices comprising hydroxyapatite, peptide solubilized elastin, collagen, fibronectin and chondroitin-6-sulfate, components of the extracellular matrix (ECM). Human osteoprogenitor cells responded differently to the materials tested according to the content of components of ECM. About 40% of attached cells were obtained on the composite materials PSE, collagen, fibronectin and chondroitin-6-sulfate, and about 10% on the macroporous materials, whatever their porosity and their chemical components. These results demonstrate a need for more effective surface treatment to promote cell attachment, cell spreading and cell growth.

The incorporation of rare earth elements in modern coral

We report measurements of rare earth elements (REEs) which show that these trace elements are being incorporated in modern coral in proportion to their seawater concentrations. Four Bermuda North Rock coral species, Diploria strigosa, Diploria labyrinthiformis, Montastrea annularis, and Porites astreoides and two Tarawa atoll samples of the species Hydnophora microconos were analyzed by TI-IDMS following cleaning techniques to isolate the lattice-bound REEs. Based on the replicate analyses of the same piece of Diploria strigosa, excellent reproducibility was achieved. The REE/Ca ratios (0.1–3 nmol/mol) of the Bermuda and Tarawa corals are similar to those of Cd/Ca, the trace metal with the lowest seawater concentration used in coral studies.With the exception of Ce, the distribution coefficients (e.g., DNd = [Nd coral/Nd seawater] × [Ca seawater/Ca coral]) between Bermuda coral lattice and Sargasso seawater have fairly flat patterns across the REE series. The values of D range from 1 to 3, like those reported for other trace elements in corals. This suggests, but does not prove, that REEs are incorporated in the aragonite lattice of these corals. The shale-normalized REE patterns of the Tarawa corals also have seawater-like distributions; however, no local seawater data are available to calculate values of D. Two Bermuda species (D. labyrinthiformis and P. astreoides) have values of D for Ce that are high with respect to the D values of La and Nd, implying that there is preferential uptake of Ce into the lattice. This may be related to the fact that Ce is the only REE with an active redox chemistry in seawater.There is considerable interest in using the chemical and isotopic composition of coral as indicators of climatic variations. The combination of REE/Ca ratios and neodymium isotopic composition of coral has the potential to help understand important natural processes. A primary application could be directed toward a tracer for river water discharge in tropical regions and, by inference, a proxy for rainfall, climate variation, and weathering history. This application would exploit the fractionated composition of REEs in river water as a terrigenous signature in coastal corals.

Chronic and catastrophic natural mortality of three common Caribbean reef corals

Compared to catastrophic impacts from storms, disease epidemics and bleaching events, little is known about the effects of more routine chronic mortality in reef corals. To monitor this ongoing mortality, monthly visual assessments of the cause of tissue damage were related to mortality rates (changes in planar surface area) of tagged colonies of three common reef corals: Montastrea annularis, Porites astreoides and Diploria strigosa at Buck Island Reef National Monument, St. Croix, US Virgin Islands. During the study Hurricane Hugo, the most powerful cyclone to affect the area in at least 60 y, made a direct impact on the site. Effects of the hurricane were extremely localized, with certain exposed sites being almost completely razed while others showed no detectable changes in community structure. Mortality caused both by the hurricane and by other factors during the 26 month study varied between species and also between site locations around the island. Differences in susceptibility were not dependent solely on gross morphology, because two robust, massive species showed opposite responses to hurricane damage and chronic mortality. Diploria strigosa was virtually unaffected by chronic factors, but was heavily damaged at exposed sites during the hurricane. In contrast, mortality from predation and tissue necrosis was high in Montastrea annularis, but it largely escaped damage from the hurricane because it was absent from the most severely scoured locations. Porites astreoides, with populations dominated by much smaller colonies, was affected by both chronic and hurricanerelated mortality. Differences in susceptibility to the various types of natural disturbance among species, coupled with high spatial and temporal variability in the effects of such disturbances, may be critical to the maintenance of species diversity on the reef.

Differential effects of ultraviolet radiation on green and brown morphs of the Caribbean coral Porites astreoides

In waters ≤2 m deep, green colonies of reef‐building Porites astreoides Lamarck are significantly more abundant than their brown counterparts. To determine whether this distributional pattern reflects differences in the ability of green and brown colonies to tolerate high intensities of ultraviolet‐A (320–400 nm) and ‐B (280−320 nm) radiation, I enhanced UV intensities by transplanting colonies of each color from 6 to 1 m deep. After 104 d, brown P. astreoides exposed to UV radiation at 1 m exhibited algal mitotic indices and linear skeletal extensions that were significantly lower than brown conspecifics shielded from UV light. In contrast, green P. astreoides were unaffected by UV radiation incident at 1 m. These morph‐specific differences in UV tolerance corresponded with variation in the quantities of UV light‐absorbing mycosporinelike amino acids (MAAs) present in the corals. Both morphs had mycosporine‐glycine (λmax = 310 nm), palythine (λmax = 320 nm), asterina‐330 (λmax = 330 nm), and shinorine (λmax = 334 nm), but green P. astreoides had significantly greater concentrations of asterina‐330 than brown colonies both before and after transplantation. Increasing the concentration of a single MAA with a broad absorbance range may represent an effective means of countering high UV intensities, and UV light may be an important abiotic factor structuring the shallow‐water distribution of P. astreoides.

Resilience of corals to hurricanes: a simulation model

This study tested how the frequency and intensity of hurricanes, and the size and growth rate of coral colonies influence the resilience of coral populations to disturbance by severe storms. A simulation modelling approach was used to examine the resilience of four coral species with differing life history characteristics: Agaricia agaricites, A. lamarcki, Helioseris cucullata, and Porites astreoides. Resilience, defined as the rate of area (coral cover) gain, was greater for three of the species when storms were less frequent or more intense. Resilience for all species increased with colony growth rates and with increasing proportion of small and medium-sized colonies. We conclude that (1) coral populations composed of intermediate-size, fast-growing colonies the most resilient following one or more storm disturbances, and (2) that resilience of anthropogenically stressed corals depends, in part, on population size structure.

Colony size as a species character in massive reef corals

In a study of seven massive, Caribbean corals, I have found major differences in reproductive behavior between species with large maximum colony sizes and species with smaller maximum colony sizes. Four species (Diploria clivosa, D. strigosa, Montastrea cavernosa, Siderastrea siderea) which are large ( 100 cm2, except M. cavernosa). In contrast, two small massive species (<100 cm2, Favia fragum and S. radians), and one medium-sized (100–1000 cm2, Porites astreoides) massive species, brood larvae during an extended season (year-round in Panama). The puberty size of the small species is only 2–4 cm2. Given these close associations between maximum colony sizes and a number of fundamental reproductive attributes, greater attention should be given to the colony size distributions of different species of reef corals in nature, since many important life history and population characters may be inferred.

Reproductive Integration in Reef Corals.

The extent of colonial integration in structurally simple animals like scleractinian corals is poorly understood. We have used sexual reproductive characters (location of fertile polyps and colony size at maturation) to assess colony-level individuality, i.e., the development, in coral colonies, of characters above the polyp level. Ten morphologically-diverse species of reef corals were used: Acropora cervicornis, A. palmata, Diploria clivosa, D. strigosa, Favia fragum, Montastrea cavernosa, Porites astreoides, P. furcata, Siderastrea radians, and S. siderea. In no species were equally fertile polyps homogeneously distributed throughout a colony. Most inhomogeneities of fertile polyps could be attributed to intra-colony position or ontogenetic effects. The results of simple manipulations simulating natural wounds in three massive species strengthen the evidence that the position of polyps within a colony determines fertility. Small colonies are not reproductive. Puberty size (colony size at maturation) could be explained by the infertility pattern along the colony margin, which does not require colony-level integration. Shape-related growth constraints could also produce the puberty size patterns found in massive corals. Infertility in the short radial polyps of A. palmata and in the axial polyps of A. cervicornis provided the only clear evidence of reproductive integration in this study: both are related to a morphological characteristic (polyp dimorphism) commonly associated with integration in colonial invertebrates.

Patterns of Coral Recruitment and Post-settlement Mortality on Bermuda's Reefs: Comparisons to Caribbean and Pacific Reefs

The recruitment of juvenile corals and post-settlement mortality are important processes for coral population dynamics and reef community ecology. I monitored juvenile coral recruitment and survival on a severely disturbed reef in Bermuda from 1981 to 1989 and on adjacent healthy reefs from 1986 to 1990. Porites astreoides was the dominant recruiting species at all sites, due to the release of brooded planulae that may settle rapidly. The dominant corals on Bermuda's reef, Diploria spp., were poor recruiters, perhaps due to the broadcast mode of reproduction of these species. However, Diploria spp. have lower juvenile mortality rates compared to P. astreoides, which may explain their abundance on Bermuda's reefs. Brooding corals, primarily agariciids, were the dominant recruits on Atlantic reefs compared to high recruitment rates by spawning acroporids in the Pacific, which may be the result of different environmental conditions and/or evolutionary trends in the two oceans. The latter group also suffered high post-settlement mortality compared to brooding coralsin both the Atlantic and the Pacific. Massive corals in both oceans had generally low recruitment rates, related to their spawning mode of reproduction, and low rates of post-settlement mortality. The dominant role of long-lived massive corals on the Atlantic and Pacific reefs can be understood in terms of their life-history strategy in comparison to the relatively short-lived Pacific acroporids and Atlantic agariciids that rely on different strategies to maintain their populations.

Short-term ecological consequences of a major oil spill on Panamanian subtidal reef corals

A major oil spill (8,000,000 liters; 50,000 barrels) occurred in Bahia Las Minas on the Caribbean coast of Panama in April 1986, and oil slicks from the refinery landfill and mangroves were still common there after 21/2 years. We studied short-term effects of the spill on common shallow subtidal reef corals, at the individual, population, and community levels. Numbers of corals, total coral cover, and species diversity based on cover decreased significantly with increased amounts of oiling. Cover of the large branching coral Acropora palmata decreased most. Frequency and size of recent injuries on massive corals increased with level of oiling, particularly for Siderastrea siderea. Growth of three massive species (Porites astreoides, Diploria strigosa, and Montastrea annularis, but not S. siderea) was less at oiled reefs in the year of the spill than during the 9 previous years. Subtidal coral reefs, particularly those along protected coasts, may suffer extensive damage from chronic exposure after major oil spills.

Settlement patterns of Caribbean scleractinian corals on artificial substrata along a eutrophication gradient, Barbados, West Indies

Artificial substrate settlement plates (terracotta tiles) were set out on 3 fringing reefs for a period of 12 mo to study settlement patterns of juvenile scleractinian corals along a eutrophication gradient on the west coast of Barbados, W.I. A total of 716 coral planulae settled on 120 experimental plates after 12 mo of exposure. Statistically higher (p 0.05) average number of juvenile corals per plate ( R = 9.2 f 3.3; N = 40) was recorded on a less eutrophic reef compared to 2 more eutrophic reefs (X = 6.9 f 3.1; N = 40 and X = 1 9 i 1.3; N = 40) Differences in juvenile coral settlement between reef zones, within each reef, were dependent on the reef's position along the eutrophication gradient. Statistically higher number of coral planulae (;if = 7.2 + 4.5; N = 60) successfully settled on vertical plates compared to horizontal plates (X = 4.8 + 3.3; N = 60). Coral planulae did not settle on upper surfaces of horizontal plates. In terms of relative abundance, the most common coral species in the juvenile population on the experimental plates were Porites astreoides Lamarck which accounted for 42% of the settled planulae, followed by Agaricia spp. (23%); and F! porites (Pallas) (19%). Juveniles of Montastrea annularis (Ellis & Solander), Siderastrea spp, and Diplona spp , while present at 2 northern reefs, were absent from the most eutrophic reef.

Preferences of planktotrophic larvae of the tropical serpulid Spirobranchus giganteus (Pallas) for exudates of corals from a Barbados reef

The serpulid polychaete Spirobranchus giganteus (Pallas) is an obligate associate of live coral. On Barbados reefs it is known to occur more commonly on some coral species than on others. Planktonic presettlement larvae of S. giganteus have been found to respond positively to water-borne exudates of two corals commonly colonised by the worm and to be indifferent to exudates of two rarely colonised corals. In this study planktonic larvae of S. giganteus from the Barbados fringing reef were examined for preferences for six coral species not previously tested. Larvae were given a choice between a test coral, a reference coral ( Montastrea cavemosa Linnaeus) and a glass bead control. S. giganteus larvae are known to have no preference for M. cavemosa. Larvae showed a preference for Porites astreoides Lamarck and Millepora complanata Lamarck, two species of coral commonly colonised by S. giganteus, no preference for Siderastrea siderea (Ellis et Solander), Dichocoenia stokesii Edwards et Haime and Dendrogyra cylindrus Ehrenberg, three species that are rarely or never colonised and no preference for Agaricia agaricites (Linnaeus), a coral whose role as a habitat for S. giganteus is unknown. The possibility that preferences of planktonic larvae may influence their distribution at the time of settlement is discussed.

Seawater temperature and sublethal coral bleaching in Jamaica

Permanent study sites were established at 6 m, 12 m and 18 m on the West Fore Reef at Discovery Bay, Jamaica. Colonies of Montastrea annularis, Porites astreoides, Porites porites and Agaricia spp. were assessed for presence and extent of bleached tissue at two month intervals between October 1986 and September 1987. In 98% of all corals exhibiting a bleaching response, less than 25% of the colony appeared pale. In the remaining 2%, more than 25% of the tissue appeared pale. M. annularis, P. astreoides and Agaricia spp. showed a significant positive correlation between the percent of colonies exhibiting a partial bleaching response and seawater temperature. There was no significant difference in the percentage of colonies bleached between the three depths. M. annularis and Agaricia spp. exhibited a significantly higher percentage of colonies bleached than P. astreoides and P. porites. For M. annularis 15% of coral colonies studied showed 1–2 cm2 randomly seattered patches of pale tissue which remained constant throughout the study. The partial bleaching patterns observed in this study were never lethal and are considered, in part, to be a response to seasonal variations in seawater temperature.