Annual cycles of solar insolation predict spawning times of Caribbean corals

Seasonal increases in sea surface temperature (SST) have long been considered the trigger for mass spawning events in reef corals. We critically examined the relationship between SST and the spawning activity of broadcasting corals in the tropical western Atlantic (Caribbean). This meta-analysis examined 12 species of broadcasting corals at 25 sites spanning 22 degrees of latitude (10°–32° N) from Venezuela to Bermuda in the Atlantic Ocean from 1986 to 2004. Sigmoidal logit regression models were used to examine the relationship between the release of reef-coral gametes and the environmental variables SST and solar insolation defined as (1) the cumulative response 7–10 months prior to spawning (integral); (2) the rate of change at the time of spawning (derivative); and (3) the average for the month of spawning. The Quasi–Newton method was used to estimate the maximum likelihood of the response function. We demonstrate that the recent history and rate of change in temperature correlate poorly with the timing of spawning, while the average temperature during the month of spawning was significant (with all corals releasing gametes 28–30 °C, except Montastraea annularis , which released gametes at 27–30 °C). In contrast, the rate of change and the cumulative response of solar insolation cycles was a better predictor of gamete release, but solar insolation intensity at the time of spawning was not. These models have important implications for predicting coral reproductive cycles in all oceans, and for examining other marine phototrophic systems beyond corals.     

Molecular diversity of symbiotic algae (zooxanthellae) in scleractinian corals of Kenya

In this first sequence analysis of ‘zooxanthellae’ (symbiotic algae of the genus Symbiodinium) in scleractinian corals in Africa, seven Kenyan species sampled in 2001–2002 were analysed by RFLP and sequencing of a PCR-amplified fragment of the LSU rRNA gene. Zooxanthellae of phylotypes A, C and D, all described previously in corals from other regions of the world, were detected. All sequences of phylotype D were identical, while phylotype C was variable, with 14 distinct sequences, seven of which clustered in a previously unreported subgroup of phylotype C, among the 22 samples. These data on the diversity of zooxanthellae in Kenyan corals 3–4 years after the 1998 bleaching event are of potential value for longitudinal studies of temporal changes in zooxanthella diversity in Kenyan corals, especially in relation to future large-scale bleaching episodes.     

Stony coral diseases observed in southwestern Caribbean reefs

Thirteen reef areas of Colombian territories in the Southwestern Caribbean were surveyed during the last 10 years. Coral diseases have been recorded in all these areas since 1990 and some of them have increased progressively. Six types were differentiated in the region, of which black band disease (BBD), dark spots disease (DSD), white band disease (WBD) and white plague disease (WPD) are widespread and common. Yellow band disease (YBD) was observed only since April 1998 but has been found now in seven reef areas and eight coral species (most of them recorded here as new hosts). In total, 25 species of hard corals were observed with diseases in the region, of which Colpophyllia natans, Diploria labyrinthiformis, Montastraea annularis, M. faveolata, M. franksi and Acropora spp. appear to be highly susceptible.     

Environmental implications of skeletal micro-density and porosity variation in two scleractinian corals

The correlations between skeletal parameters (bulk density, micro-density and porosity), coral age and sea surface temperature were assessed along a latitudinal gradient in the zooxanthellate coral Balanophyllia europaea and in the azooxanthellate coral Leptopsammia pruvoti. In both coral species, the variation of bulk density was more influenced by the variation of porosity than of micro-density. With increasing polyp age, B. europaea formed denser and less porous skeletons while L. pruvoti showed the opposite trend, becoming less dense and more porous. B. europaea skeletons were generally less porous (more dense) than those of L. pruvoti, probably as a consequence of the different habitats colonized by the two species. Increasing temperature had a negative impact on the zooxanthellate species, leading to an increase of porosity. In contrast, micro-density increased with temperature in the azooxanthellate species. It is hypothesized that the increase in porosity with increasing temperatures observed in B. europaea could depend on an attenuation of calcification due to an inhibition of the photosynthetic process at elevated temperatures, while the azooxanthellate species appears more resistant to variations of temperature, highlighting possible differences in the sensitivity/tolerance of these two coral species to temperature changes in face of global climate change.     

Herbivory by crabs and the control of algal epibionts on Caribbean host corals

Summary A short-term experiment was conducted to examine the relationships among the branching coral Porites porites, algal epibionts, and a facultative crab associate Mithrax sculptus in Belize, Central America. Initial field observations suggested that coral colonies supporting resident crabs generally had lower algal cover than colonies without crabs. The hypothesis was tested that Mithrax significantly depresses host coral algal cover and thereby indirectly affects host survivorship and growth. Crab accessibility to an array of coral colonies, similarly covered with algal epibionts, was manipulated in three treatments. Results strongly support the hypothesis, with significant differences in algal cover (primarily Dictyota spp.) noted among treatments after only one month. Caged heads with crabs included and uncaged natural controls allowing crabs free access averaged less than 10% cover, whereas mean algal cover exceeded 75% where crabs were excluded. The uncaged treatment, in which crabs were allowed free access to Porites heads was not significantly different from the crab inclusion treatment. Collectively, these results demonstrate that under natural conditions, crabs can have pronounced effects on host corals by reducing fouling algal epibionts. Furthermore, these facultative coral associates may have more important, albeit localized effects on Caribbean corals than has been suggested previously.     

Spatial study of juvenile corals in the Northern region of the Mesoamerican Barrier Reef System (MBRS)

Juvenile coral abundance and community composition depend on the spatial scale studied. To investigate this, an evaluation was made of juvenile coral density with hierarchical spatial analysis in the northern Mesoamerican Barrier Reef System (MBRS) at ~10 m depth. Study scope included semi-protected and unprotected areas located in this region. A total of 19 juvenile coral taxa were found, including 10 scleractinian species, 8 scleractinian coral genera not identified to species, and 1 Millepora species (Hydrozoa-Milleporidae). In terms of relative abundance, Agaricia spp., Siderastrea spp., and Porites spp. were the main juvenile taxa in the coral community at the surveyed sites, reefs, and regions levels. Greater variance was seen at smaller scales, at site level for taxa richness, and at the transect level for juvenile density, and lower variance was seen at larger scales (reefs and regions). The variance component contribution from each scale likely differed from other studies because of the different factors affecting the community and the different extensions of each scale used in each study. Densities (1–6.4 juvenile corals/m²) and dominant taxa found in this study agree with other studies from the Western Atlantic. Detected variability was explained by different causal agents, such as low grazing rates by herbivorous organisms, turbidity, and/or sediment suffocation and some nearby or distant localized disturbance (human settlement and a hurricane).     

New records of ahermatypic scleractinian corals from the Kuril Islands

Four species of caryophyllid scleractinians, Caryophylla ambrosia, C. scobinosa, C. alaskensis, and Polymyces montereyensis, were recorded for the first time in the Sea of Okhotsk off the Kuril Islands. These findings extend the range for the species, of which three had previously been considered to be restricted to the tropical and warm Indopacific waters. These data will supplement regional reports on the bottom fauna of the most fertile and extensively commercially exploited continental shelf region of the North Pacific.Original Russian Text Copyright © 2004 by Biologiya Morya, Latypov.     

Photophysiological stress in scleractinian corals in response to short-term sedimentation

Effects of short-term sedimentation on common coastal coral species were investigated in laboratory and field experiments on the Great Barrier Reef (GBR) using pulse-amplitude modulated (PAM) chlorophyll fluorometry. In the laboratory, changes in maximal quantum yields of photosystem II (F_v/F_m) in Montipora peltiformis were examined in response to the amount of sedimentation (79-234 mg cm⁻²) and duration of exposure (0-36 h). In control colonies, F_v/F_m ranged from 0.67 to 0.71, and did not show any temporal trend, while maximum yields of sediment-covered fragments declined steadily and reached levels below 0.1 in most colonies after 36 h coverage. Maximal quantum yield in M. peltiformis declined linearly in relation to both the amount of sediment deposited per unit surface area and the duration of exposure. Zooxanthellae densities and chlorophyll concentrations per unit area of sediment-treated corals decreased in the same manner, however, their responses were not quite as strong as the changes in F_v/F_m. Within the ranges measured, sedimentation stress of colonies exposed to large amounts of sediment for short periods of time was similar to that exposed to low amounts of sediments for prolonged periods of time. Colonies were recovered from short-term, or low-level, sedimentation within <36 h, whereas long-term exposure, or high levels of sedimentation, killed exposed colony parts. Field experiments comparing susceptibilities of common coastal coral species towards sedimentation showed significant reductions in effective quantum yields (ΔF/F_m′) in 9 out of 12 common coastal species after 22 h of exposure. Three out of twelve investigated species were not affected by the experimental application of sediments (Galaxea fascicularis, Fungia crassa, and Pectinia lactuca). Our results suggest that anthropogenic sediment deposition can negatively affect the photosynthetic activity of zooxanthellae and thus the viability of corals. However, the results also showed the ability of corals to compartmentalise sedimentation stress, as the photosynthetic activity only from tissues directly underneath the sediment declined, whereas that of adjacent clean tissues did not change measurably.     

Small-scale variability in the size structure of scleractinian corals around Moorea, French Polynesia: patterns across depths and locations

The size structure of coral populations is influenced by biotic and physical factors, as well as species-specific demographic rates (recruitment, colony growth, mortality). Coral reefs surrounding Moorea Island are characterized by strong environmental gradients at small spatial scales, and therefore, we expected that the size structure of coral populations would vary greatly at this scale. This study aimed at determining the degree of spatial heterogeneity in the population size structure of two coral taxa, Pocillopora meandrina and massive Porites spp., among depths (6, 12, and 18 m) and among locations (Vaipahu, Tiahura and Haapiti) representing different exposure to hydrodynamic forces. Our results clearly underlined the strong heterogeneity in the size structure of both P. meandrina and massive Porites spp., with marked variation among depths and among locations. However, the lack of any consistent and regular trends in the size structure along depths or among locations, and the lack of correlation between size structure and mean recruitment rates may suggest that other factors (e.g., stochastic life history processes, biotic interactions, and disturbances) further modify the structure of coral populations. We found that the size structure of P. meandrina was fundamentally different to that of massive Porites spp., reflecting the importance of life history characteristics in population dynamics. Handling editor: I. Nagelkerken     

Sperm morphology of scleractinians from the Caribbean

This study compares the sperm morphology of 2 hermaphroditic (Diploria strigosa, Montastrea annularis) and 2 gonochoric (Siderastrea siderea, Dendrogyra cylindrus) Caribbean reef corals. The spermatozoa of the gonochoric species are morphologically more specialized than those of the hermaphrodites. The cytological differences are apparent in the formation of a Spitzenkörper and pro-acrosomal vesicles, a mitochondrial mass (Nebenkern) and a large lipid vesicle in the gonochorists studied. Harrison (1985) first demonstrated that sperm morphology is correlated with sexual reproductive pattern and systematic position in scleractinian corals, and this is supported by the results of this study. The possible functional and phylogenetic bases of sperm morphology are discussed and a brief outline is given of further studies required.     

Local and regional scale recovery of Diadema promotes recruitment of scleractinian corals

The phase change from coral to macroalgal dominance on many Caribbean reefs was exacerbated by the mortality of the echinoid Diadema antillarum in 1983–1984, and until recently, this sea urchin has remained rare on reefs throughout the western Atlantic. By the late 1990s, Diadema started to reappear in large numbers on some Jamaican reefs, and by 2000, the high densities were correlated with significantly greater abundances of juvenile corals. Here, we show that dense populations of Diadema now occur over a multi-kilometre-wide scale at six locations scattered along a 4100 km arc across the entire Caribbean. In all cases, these dense populations are found in shallow water (< 6 m depth) on outer reef communities and are associated with reduced macroalgal cover and enhanced coral recruitment. We conclude that population recovery of Diadema is occurring at both local and regional scales, and that grazing by this echinoid is creating conditions favouring the recruitment of corals.     

A unique skeletal microstructure of the deep‐sea micrabaciid scleractinian corals

Micrabaciids are solitary, exclusively azooxanthellate deep‐sea corals belonging to one of the deepest‐living (up to 5,000 m) scleractinian representatives. All modern micrabaciid taxa (genera: Letepsammia, Rhombopsammia, Stephanophyllia, Leptopenus) have a porous and often very fragile skeleton consisting of two main microstructural components known also from other scleractinians: rapid accretion deposits and thickening deposits. However, at the microstructural level, the skeletal organization of the micrabaciids is distinctly different from that of other scleractinians. Rapid accretion deposits consist of alternations of superimposed “microcrystalline” (micrometer‐sized aggregates of nodular nanodomains) and fibrous zones. In contrast to all shallow‐water and sympatric deep‐water corals so far described, the thickening deposits of micrabaciids are composed of irregular meshwork of short (1–2 μm) and extremely thin (ca. 100–300 nm) fibers organized into small, chip‐like bundles (ca. 1–2 μm thick). Longer axes of fiber bundles are usually subparallel to the skeletal surfaces and oriented variably in this plane. The unique microstructural organization of the micrabaciid skeleton is consistent with their monophyletic status based on macromorphological and molecular data, and points to a diversity of organic matrix‐mediated biomineralization strategies in Scleractinia. J. Morphol.,2011. © 2010 Wiley‐Liss, Inc.     

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.     

Evidence of an inflammatory-like response in non-normally pigmented tissues of two scleractinian corals

Increasing evidence of links between climate change, anthropogenic stress and coral disease underscores the importance of understanding the mechanisms by which reef-building corals resist infection and recover from injury. Cellular inflammation and melanin-producing signalling pathway are two mechanisms employed by invertebrates to remove foreign organisms such as pathogens, but they have not been recorded previously in scleractinian corals. This study demonstrates the presence of the phenoloxidase (PO) activating melanin pathway in two species of coral, Acropora millepora and a massive species of Porites, which both develop local pigmentation in response to interactions with a variety of organisms. L-DOPA (3-(3,4-dihydroxyphenyl)-L-alanine) substrate-based enzyme activation assays demonstrated PO activity in healthy tissues of both species and upregulation in pigmented tissues of A. millepora. Histological staining conclusively identified the presence of melanin in Porites tissues. These results demonstrate that the PO pathway is active in both coral species. Moreover, the upregulation of PO activity in areas of non-normal pigmentation in A. millepora and increased melanin production in pigmented Porites tissues suggest the presence of a generalized defence response to localized stress. Interspecific differences in the usage of pathways involved in innate immunity may underlie the comparative success of massive Porites sp. as long-lived stress tolerators.     

The distribution of scleractinian corals in the Bay of Biscay, NE Atlantic

Studies on the distribution of scleractinian corals in the Bay of Biscay were relatively numerous during the nineteenth and the first half of the twentieth century. Yet, recent reports are scattered, sometimes unpublished, and therefore knowledge about the current coral occurrence in the area is limited. This study aims at compiling the available historical and more recently collected information on the occurrence of scleractinian corals in the Bay of Biscay. Data from two recent cruises are included and compared with previous explored coral sites from as early as 1830 up to 1995. A database of 347 records including 34 described species of scleractinians highlights that the slope of the Bay of Biscay is an important habitat for scleractinians. This could be expected due to the high topographic relief providing the necessary hard substrate and accelerated bottom current flow that corals require. Further exploration of the occurrence and ecology of corals in the area is recommended to support the conservation of cold-water coral reefs along the European margin. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Diversity and extinction in the Cenozoic history of Caribbean reefs

Occurrences of reef corals are examined at Caribbean fossil localities to determine how biodiversity has changed within the region over the past 50 million years. Analyses of 294 species (66 genera) at 58 fossil localities show that Caribbean generic diversity rose to 44 between 50–22 Ma, ranged from 32–39 between 22–2 Ma, and dropped to 25 afterwards. Regional species diversity was high at 40–36 Ma, 28–22 Ma, and 5–2 Ma. Origination rates were elevated throughout each high diversity interval, but extinction was concentrated near the end of each interval. Regional highs of origination and extinction, therefore, differed in timing and duration, causing the observed regional diversity increases during the three remarkably long intervals of turnover. Highs of generic origination decreased in magnitude as immigration from the Mediterranean ceased, but speciation highs increased in association with emergence of the Central American isthmus. Peaks of extinction coincided with regional changes in climate and oceanic circulation. Maximum species diversities within assemblages increased to 40–60 between 50–36 Ma, and have remained relatively constant ever since. Assemblage compositions differed among localities having similar ages and environments, suggesting that the timing and pattern of turnover varied across the region. Stable diversities but variable compositions within assemblages suggest that dispersal and recruitment influenced the pattern of faunal change during turnover. Accepted: 22 August 1999     

Interactive effects of ocean acidification and temperature on two scleractinian corals from Moorea,French Polynesia

This study tested the hypothesis that the response of corals to temperature and pCO ₂ is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3 °C and 25.6 °C) and pCO ₂ (41.6 Pa and 81.5 Pa) at an irradiance of 599 μmol quanta m^?2 s^?1. Using microcosms and CO₂ gas mixing technology, treatments were created in a partly nested design (tanks) with two between‐plot factors (temperature and pCO ₂), and one within‐plot factor (taxon); calcification was used as a dependent variable. pCO ₂ and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3 °C compared with 25.6 °C, and 28% slower at 81.5 Pa vs. 41.6 Pa CO₂. A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO₃ ^?], and [CO₃ ^2?]. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO₃ cm^?2 h^?1. The compilation revealed a high degree of variation in calcification as a function of pH, [HCO₃ ^?], and [CO₃ ^2?], and supported three conclusions: (1) studies of the effects of ocean acidification on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO₃ ^?], and [CO₃ ^2?], and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO ₂, similar to that expected within 100 y.     

Ecological persistence interrupted in Caribbean coral reefs

The recent mass mortality of Caribbean reef corals dramatically altered reef community structure and begs the question of the past stability and persistence of coral assemblages before human disturbance began. We report within habitat stability in coral community composition in the Pleistocene fossil record of Barbados for at least 95 000 years despite marked variability in global sea level and climate. Results were consistent for surveys of both common and rare taxa. Comparison of Pleistocene and modern community structure shows that Recent human impacts have changed coral community structure in ways not observed in the preceding 220 000 years.     

Corallite wall and septal microstructure in scleractinian reef corals: Comparison of molecular clades within the family Faviidae

Recent molecular phylogenies conflict with traditional scleractinian classification at ranks ranging from suborder to genus, challenging morphologists to discover new characters that better agree with molecular data. Such characters are essential for including fossils in analyses and tracing evolutionary patterns through geologic time. We examine the skeletal morphology of 36 species belonging to the traditional families Faviidae, Merulinidae, Pectiniidae, and Trachyphylliidae (3 Atlantic, 14 Indo‐Pacific, 2 cosmopolitan genera) at the macromorphological, micromorphological, and microstructural levels. Molecular analyses indicate that the families are not monophyletic groups, but consist of six family‐level clades, four of which are examined [clade XV = Diploastrea heliopora; clade XVI = Montastraea cavernosa; clade XVII (“Pacific faviids”) = Pacific faviids (part) + merulinids (part) + pectiniids (part) + M. annularis complex; clade XXI (“Atlantic faviids”) = Atlantic faviids (part) + Atlantic mussids]. Comparisons among molecular clades indicate that micromorphological and microstructural characters (singly and in combination) are clade diagnostic, but with two exceptions, macromorphologic characters are not. The septal teeth of “Atlantic faviids” are paddle‐shaped (strong secondary calcification axes) or blocky, whereas the septal teeth of “Pacific faviids” are spine‐shaped or multidirectional. Corallite walls in “Atlantic faviids” are usually septothecal, with occasional trabeculothecal elements; whereas corallite walls in “Pacific faviids” are usually trabeculothecal or parathecal or they contain abortive septa. Exceptions include subclades of “Pacific faviids” consisting of a) Caulastraea and Oulophyllia (strong secondary axes) and b) Cyphastrea (septothecal walls). Diploastrea has a diagnostic synapticulothecal wall and thick triangular teeth; Montastraea cavernosa is also distinct, possessing both “Pacific faviid” (abortive septa) and “Atlantic faviid” (paddle‐shaped teeth) attributes. The development of secondary axes is similar in traditional Atlantic faviids and mussids, supporting molecular results placing them in the same clade. Subclades of “Pacific faviids” reveal differences in wall structure and the arrangement and distinctiveness of centers of rapid accretion. J. Morphol. 272:66–88, 2011. © 2010 Wiley‐Liss, Inc.