Symbiont diversity in scleractinian corals from tropical reefs and subtropical non-reef communities in Taiwan

We examined zooxanthellae diversity in scleractinian corals from southern Taiwan and the Penghu Archipelago, a tropical coral reef and a subtropical non-reefal community, respectively. Zooxanthellae diversity was investigated in 52 species of scleractinian corals from 26 genera and 13 families, using restriction fragment length polymorphism (RFLP), and phylogenetic analyses of the nuclear small-subunit ribosomal DNA (nssrDNA) and large-subunit ribosomal DNA (nlsrDNA). RFLP and phylogenetic analyses of nuclear-encoded ribosomal RNA genes showed that Symbiodinium clade C was the dominant zooxanthellae in scleractinian corals in the seas around Taiwan; Symbiodinium clade D was also found in some species. Both Symbiodinium clade C and D were found in colonies of seven species of scleractinian corals. Symbiodinium clade D was associated with corals that inhabit either shallow water or the reef edge in deep water, supporting the hypothesis that Symbiodinium clade D is a relatively stress-tolerant zooxanthellae found in marginal habitats.Communicated by Biological Editor H.R. Lasker     

Chronic parrotfish grazing impedes coral recovery after bleaching

Coral bleaching, in which corals become visibly pale and typically lose their endosymbiotic zooxanthellae (Symbiodinium spp.), increasingly threatens coral reefs worldwide. While the proximal environmental triggers of bleaching are reasonably well understood, considerably less is known concerning physiological and ecological factors that might exacerbate coral bleaching or delay recovery. We report a bleaching event in Belize during September 2004 in which Montastraea spp. corals that had been previously grazed by corallivorous parrotfishes showed a persistent reduction in symbiont density compared to intact colonies. Additionally, grazed corals exhibited greater diversity in the genetic composition of their symbiont communities, changing from uniform ITS2 type C7 Symbiodinium prior to bleaching to mixed assemblages of Symbiodinium types post-bleaching. These results suggest that chronic predation may exacerbate the influence of environmental stressors and, by altering the coral-zooxanthellae symbiosis, such abiotic-biotic interactions may contribute to spatial variation in bleaching processes.     

Highly stable symbioses among western Atlantic brooding corals

The reproductive mode of corals largely determines how zooxanthellae (Symbiodinium spp.) are acquired. Typically, broadcast spawning corals obtain symbionts from the surrounding environment, whereas most brooders transfer symbionts from maternal parent to offspring. Brooding corals are therefore predicted to harbor stable communities of Symbiodinium. This study documents the associations between Symbiodinium spp. and brooding corals in response to seasonal environmental fluctuations. Between March 2002 and December 2005, endosymbiont identity was determined seasonally from replicate colonies (n = 6) of three brooding species, Agaricia agaricites, Porites astreoides and Siderastrea radians, from shallow environments (1–4 m) of the Florida Keys and Bahamas. Symbionts were identified via denaturing gradient gel electrophoresis (DGGE) of the internal transcribed spacer 2 (ITS2) region. No change was detected in the Symbiodinium communities harbored within these brooding colonies. Additionally, no change in symbiosis was observed through a moderate bleaching event, thereby demonstrating that some bleached corals recover without changing symbionts.     

Quantifying the colony shape of the Montastraea annularis species complex

The reef coral Montastraea annularis has been used in a wide range of investigations. Recently, it has been recognized as a complex of three species based on field observations of the variation in colony shape. These observations have also been confirmed by molecular methods as well as morphometrics on individual corallites in the colonies. This paper presents a new quantitative method for measuring overall colony shape based on geostatistics. Seventeen colonies collected from San Blas, Panama in 1995 and 1996 were examined using the Polhemus 3SPACE FASTRAK system to construct three-dimensional coordinates of the center of several hundred corallites in each colony. This method measures the larger bumps or “ridges” as well as the smaller bumps or “lumps” of the colonies. Variograms were then calculated for all the specimens and the lag distances and the values of the variogram were used in a multivariate statistical analysis. Overall, this method indicated that M. annularis and Montastaea faveolata overlap in their relative amount of bumpiness in colony shape while Montastraea franksi is distinct from the other two species. This method has implications for both the modern and fossil record of Montastraea as well as other organisms with similar shapes.     

The distribution of the thermally tolerant symbiont lineage (Symbiodinium clade D) in corals from Hawaii: correlations with host and the history of ocean thermal stress

Spatially intimate symbioses, such as those between scleractinian corals and unicellular algae belonging to the genus Symbiodinium, can potentially adapt to changes in the environment by altering the taxonomic composition of their endosymbiont communities. We quantified the spatial relationship between the cumulative frequency of thermal stress anomalies (TSAs) and the taxonomic composition of Symbiodinium in the corals Montipora capitata, Porites lobata, and Porites compressa across the Hawaiian archipelago. Specifically, we investigated whether thermally tolerant clade D Symbiodinium was in greater abundance in corals from sites with high frequencies of TSAs. We recovered 2305 Symbiodinium ITS2 sequences from 242 coral colonies in lagoonal reef habitats at Pearl and Hermes Atoll, French Frigate Shoals, and Kaneohe Bay, Oahu in 2007. Sequences were grouped into 26 operational taxonomic units (OTUs) with 12 OTUs associated with Montipora and 21 with Porites. Both coral genera associated with Symbiodinium in clade C, and these co‐occurred with clade D in M. capitata and clade G in P. lobata. The latter represents the first report of clade G Symbiodinium in P. lobata. In M. capitata (but not Porites spp.), there was a significant correlation between the presence of Symbiodinium in clade D and a thermal history characterized by high cumulative frequency of TSAs. The endogenous community composition of Symbiodinium and an association with clade D symbionts after long‐term thermal disturbance appear strongly dependent on the taxa of the coral host.     

Molecular identification of symbiotic dinoflagellates (Symbiodinium spp.) from Palythoa spp. (Anthozoa: Hexacorallia) in Japan

In Japan, zooxanthellate Palythoa tuberculosa Klunzinger and Palythoa mutuki Verrill (Anthozoa: Hexacorallia: Zoantharia) are found over a 1,000 + km latitudinal range, often in environments where most other zooxanthellate anthozoans are not found (i.e. tidal lagoon pools, around shallow water hydrothermal vents, subtropical rocky shorelines). Sequences of internal transcribed spacer of ribosomal DNA (ITS-rDNA) of the symbiotic dinoflagellate genus Symbiodinium (zooxanthellae) Freudenthal (Order Suessiales) from P. tuberculosa and P. mutuki from several locations in Japan (34°11′N–24°16′N) were analysed. Unexpectedly, despite the ability of the genus Palythoa to be flexible in association with different Symbiodinium subclades, most (35 of 36) Palythoa investigated here specifically associate with subclade C1 and closely related types. Symbiodinium subclade C1 has been characterized as a “generalist” in terms of the ability to associate with a range of hosts, but present results suggest that subclade C1 may also be a “generalist” in terms of being able to live in a variety of environments over a latitudinal range. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Reef Endemism,Host Specificity and Temporal Stability in Populations of Symbiotic Dinoflagellates from Two Ecologically Dominant Caribbean Corals

Background

The dinoflagellate genus Symbiodinium forms symbioses with numerous protistan and invertebrate metazoan hosts. However, few data on symbiont genetic structure are available, hindering predictions of how these populations and their host associations will fair in the face of global climate change.

Methodology/Principal Findings

Here, Symbiodinium population structure from two of the Caribbean''s ecologically dominant scleractinian corals, Montastraea faveolata and M. annularis, was examined. Tagged colonies on Florida Keys and Bahamian (i.e., Exuma Cays) reefs were sampled from 2003–2005 and their Symbiodinium diversity assessed via internal transcribed spacer 2 (ITS2) rDNA and three Symbiodinium Clade B-specific microsatellite loci. Generally, the majority of host individuals at a site harbored an identical Symbiodinium ITS2 “type” B1 microsatellite genotype. Notably, symbiont genotypes were largely reef endemic, suggesting a near absence of dispersal between populations. Relative to the Bahamas, sympatric M. faveolata and M. annularis in the Florida Keys harbored unique Symbiodinium populations, implying regional host specificity in these relationships. Furthermore, within-colony Symbiodinium population structure remained stable through time and environmental perturbation, including a prolonged bleaching event in 2005.

Conclusions/Significance

Taken together, the population-level endemism, specificity and stability exhibited by Symbiodinium raises concerns about the long-term adaptive capacity and persistence of these symbioses in an uncertain future of climate change.     

<Emphasis Type="Italic">Symbiodinium</Emphasis> associations with diseased and healthy scleractinian corals

Despite recent advances in identifying the causative agents of disease in corals and understanding the impact of epizootics on reef communities, little is known regarding the interactions among diseases, corals, and their dinoflagellate endosymbionts (Symbiodinium spp.). Since the genotypes of both corals and their resident Symbiodinium contribute to colony-level phenotypes, such as thermotolerance, symbiont genotypes might also contribute to the resistance or susceptibility of coral colonies to disease. To explore this, Symbiodinium were identified using the internal transcribed spacer-2 region of ribosomal DNA from diseased and healthy tissues within individual coral colonies infected with black band disease (BB), dark spot syndrome (DSS), white plague disease (WP), or yellow blotch disease (YB) in the Florida Keys (USA) and the US Virgin Islands. Most of the diseased colonies sampled contained B1, B5a, or C1 (depending on host species), while apparently healthy colonies of the same coral species frequently hosted these types and/or additional symbiont diversity. No potentially “parasitic” Symbiodinium types, uniquely associated with diseased coral tissue, were detected. Within most individual colonies, the same dominant Symbiodinium type was detected in diseased and visually healthy tissues. These data indicate that specific Symbiodinium types are not correlated with the infected tissues of diseased colonies and that DSS and WP onset do not trigger symbiont shuffling within infected tissues. However, few diseased colonies contained clade D symbionts suggesting a negative correlation between hosting Symbiodinium clade D and disease incidence in scleractinian corals. Understanding the influence of Symbiodinium diversity on colony phenotypes may play a critical role in predicting disease resistance and susceptibility in scleractinian corals.     

Occurrence of the putatively heat-tolerant <Emphasis Type="Italic">Symbiodinium</Emphasis> phylotype D in high-latitudinal outlying coral communities

Biogeographic investigations have suggested that coral-symbiont associations can adapt to higher temperatures by hosting a heat-tolerant Symbiodinium, phylotype D. It is hypothesized that phylotype D is absent in high latitudes due to its heat-tolerant characteristics. In this study, this hypothesis was tested by examining the symbiont diversity in a scleractinian coral, Oulastrea crispata, throughout its entire latitudinal distribution range in the West Pacific. Molecular phylotyping of the 5′-end of the nuclear large subunit of ribosomal DNA (lsu rDNA) indicated that phylotype D was the dominant Symbiodinium in O. crispata from the tropical reefs to the marginal non-reefal coral communities. Several colonies of tropical populations were associated with phylotype C, either alone or simultaneously with phylotype D. Analysis of the polymerase chain reaction products using single-strand conformation polymorphism (SSCP) detected relatively low densities of phylotype C in most of the O. crispata colonies surveyed. These results provide evidence for the occurrence of phylotype D in cold-water outlying coral communities. The dominant occurrence of phylotype C in some O. crispata colonies on tropical reefs and the relatively low densities of phylotype C identified by SSCP in subtropical and temperate populations show that the dominant symbiont type can vary in this coral species and that multiple symbionts can co-occur in the same host.     

The Relative Significance of Host–Habitat,Depth, and Geography on the Ecology,Endemism, and Speciation of Coral Endosymbionts in the Genus Symbiodinium

Dinoflagellates in the genus Symbiodinium are among the most abundant and important group of eukaryotic microbes found in coral reef ecosystems. Recent analyses conducted on various host cnidarians indicated that Symbiodinium assemblages in the Caribbean Sea are genetically and ecologically diverse. In order to further characterize this diversity and identify processes important to its origins, samples from six orders of Cnidaria comprising 45 genera were collected from reef habitats around Barbados (eastern Caribbean) and from the Mesoamerican barrier reef off the coast of Belize (western Caribbean). Fingerprinting of the ribosomal internal transcribed spacer 2 identified 62 genetically different Symbiodinium. Additional analyses of clade B Symbiodinium using microsatellite flanker sequences unequivocally characterized divergent lineages, or “species,” within what was previously thought to be a single entity (B1 or B184). In contrast to the Indo-Pacific where host-generalist symbionts dominate many coral communities, partner specificity in the Caribbean is relatively high and is influenced little by the host’s apparent mode of symbiont acquisition. Habitat depth (ambient light) and geographic isolation appeared to influence the bathymetric zonation and regional distribution for most of the Symbiodinium spp. characterized. Approximately 80% of Symbiodinium types were endemic to either the eastern or western Caribbean and 40–50% were distributed to compatible hosts living in shallow, high-irradiance, or deep, low-irradiance environments. These ecologic, geographic, and phylogenetic patterns indicate that most of the present Symbiodinium diversity probably originated from adaptive radiations driven by ecological specialization in separate Caribbean regions during the Pliocene and Pleistocene periods.     

Photobiology of Symbiodinium revisited: bio-physical and bio-optical signatures

Light is often the most abundant resource within the nutrient-poor waters surrounding coral reefs. Consequently, zooxanthellae (Symbiodinium spp.) must continually photoacclimate to optimise productivity and ensure coral success. In situ coral photobiology is becoming dominated by routine assessments using state-of-the-art non-invasive bio-optical or chlorophyll a fluorescence (bio-physical) techniques. Multiple genetic types of Symbiodinium are now known to exist; however, little focus has been given as to how these types differ in terms of characteristics that are observable using these techniques. Therefore, this investigation aimed to revisit and expand upon a pivotal study by Iglesias-Prieto and Trench (1994) by comparing the photoacclimation characteristics of different Symbiodinium types based on their bio-physical (chlorophyll a fluorescence, reaction centre counts) and bio-optical (optical absorption, pigment concentrations) ‘signatures’. Signatures described here are unique to Symbiodinium type and describe phenotypic responses to set conditions, and hence are not suitable to describe taxonomic structure of in hospite Symbiodinium communities. In this study, eight Symbiodinium types from clades and sub-clades (A–B, F) were grown under two PFDs (Photon Flux Density) and examined. The photoacclimation response by Symbiodinium was highly variable between algal types for all bio-physical and for many bio-optical measurements; however, a general preference to modifying reaction centre content over effective antennae-absorption was observed. Certain bio-optically derived patterns, such as light absorption, were independent of algal type and, when considered per photosystem, were matched by reaction centre stoichiometry. Only by better understanding genotypic and phenotypic variability between Symbiodinium types can future studies account for the relative taxonomic and physiological contribution by Symbiodinium to coral acclimation.     

<Emphasis Type="Italic">“Pseudoalteromonas januaria”</Emphasis> SUT 11 as the Source of Rare Lipodepsipeptides

The marine bacterium “Pseudoalteromonas januaria” SUT 11 isolated from a seawater sample produced the rare cell-bound cyclic lipodepsipeptides A/A′, B/B′, and C/C′. The matrix-assisted laser desorption/ionization mass spectra indicated that one bromine atom presented in the peptides B/B′ and C/C′, whereas the component A/A′ contained no bromine atom. The acyldepsipeptides A/A′–C/C′ have an identical amino acid sequence, Thr-Val-Asn-Asn-Leu/allo-Ile, but differed in C-terminal amino acid and acyl moieties. Peptides A–C have Leu as a C-terminal amino acid, whereas peptides A′-C′ have allo-Ile. Acyl moieties in peptides A/A′, B/B′, and C/C′ have been found to consist of 11-(4′-hydroxyphenyl)-undeca-2,4,6,8,10-pentaenic acid, 9-(3′-bromo-4′-hydroxyphenyl)-nona-2,4,6,8-tetraenic acid, and 11-(3′-bromo-4′-hydroxyphenyl)-undeca-2,4,6,8,10-pentaenic acid, respectively. The structure of a main pair of peptides B/B′ with molecular masses 843/845 Da has been determined by means of ultraviolet, infrared, and two-dimensional nuclear magnetic resonance spectroscopy. We have demonstrated that tandem nano-electrospray ionization mass spectrometry is a very efficient way for the fast and sensitive investigation of lipopeptides A/A′ and C/C′ with molecular masses 791 and 869/871 Da, respectively, which have been isolated in small amounts.     

Polymorphism in a common Atlantic reef coral (Montastraea cavernosa) and its long-term evolutionary implications

Recent advances in morphometrics and genetics have led to the discovery of numerous cryptic species in coral reef ecosystems. A prime example is the Montastraea annularis scleractinian coral species complex, in which morphological, genetic, and reproductive data concur on species boundaries, allowing evaluation of long-term patterns of speciation and evolutionary innovation. Here we test for cryptic species in the Atlantic species, Montastraea cavernosa, long recognized as polymorphic. Our modern samples consist of 94 colonies collected at four locations (Belize, Panamá, Puerto Rico in the Caribbean; S?o Tomé in the Eastern Atlantic). Our fossil samples consist of 78 colonies from the Plio-Pleistocene of Costa Rica and Panamá. Landmark morphometric data were collected on thin sections of 46 modern and 78 fossil colonies. Mahalanobis distances between colonies were calculated using Bookstein coordinates, revealing two modern and four fossil morphotypes. The remaining 48 of the 94 modern colonies were assigned to morphotype using discriminant analysis of calical measurements. Cross-tabulation and multiple comparisons tests show no significant morphological differences among geographic locations or water depths. Patterns of variation within and among fossil morphotypes are similar to modern morphotypes. DNA sequence data were collected for two polymorphic nuclear loci (β-tub1 and β-tub2) on all 94 modern colonies. Haplotype networks show that both genes consist of two clades, but morphotypes are not associated with genetic clades. Genotype frequencies and two-locus genotype assignments indicate genetic exchange across clades, and ϕst values show no genetic differentiation between morphotypes at different locations. Taken together, our morphological and genetic results do not provide evidence for cryptic species in M. cavernosa, but indicate instead that this species has an unusually high degree of polymorphism over a wide geographic area and persisting for >25 million years (myr).     

Spawning of hermatypic corals in Bermuda: a pilot study

This study investigates spawning of 4 hermatypic coral species from the subtropical environment of Bermuda. Laboratory evidence of spawning behaviour is supported by synchronous field observations. Development of scleractinian planulae to postlarval stages is recorded. Diploria strigosa, D. labyrinthiformis, Montastrea annularis and M. cavernosa shed highly buoyant, pigmented eggs (300–440 µm diam.) during July to September 1986. Brief spawning periods, synchronous between conspecific colonies, were recorded for M. annularis (July and August) and M. cavernosa (August) within 1 d of the last quarter of the lunar cycle. In August, there were overlaps amongst the spawning dates of D. strigosa and the Montastrea species. Nocturnal spawning periods differed between M. annularis and M. cavernosa. This constitutes the first evidence from an Atlantic community of overlapping spawning dates amongst several faviid species, and of the accumulation of scleractinian eggs and planulae in surface slicks.     

Yellow band and dark spot syndromes in Caribbean corals: distribution,rate of spread,cytology, and effects on abundance and division rate of zooxanthellae

Yellow band and dark spot syndromes have been frequently observed to affect coral species throughout the Caribbean within the last 10 years. These syndromes significantly impair at least three important reef-building species. Yellow band (also known as yellow blotch) appears as rings or blotches on Montastrea annularis throughout the Caribbean. The coral tissue necrosis occurs at a rate of approximately 0.6 cm/month. Transect measurements at various locations indicated that as many as 90% of M. annularis were affected by yellow band during 1997–98. Tissue samples reveal a 41–96.9% decrease in zooxanthellae/sample compared to healthy specimens, depending on distance from healthy tissue. Mitotic indices (MI) of zooxanthellae (symbiotic algae appearing as doublets) for M. annularis are 2.5%. MI in yellow band samples directly bordering healthy tissue are less than 0.9%, and zooxanthellae directly within the band bordering exposed skeleton had a mitotic index of 0.0%. This indicates impairment of zooxanthellae cell division in yellow band specimens. Zooxanthellae are not expelled and appear vacuolated and devoid of organelles. Dark spot, characterized by tissue necrosis as well as a depression of the colony surface, affects Stephanocoenia michelinii and Siderastrea siderea throughout the Caribbean. Transects showed that as many as 56% of S. michelinii and S. siderea showed signs of dark spot during 1997–98. Affected tissues of S. siderea died at a rate of 4.0 cm/month. In dark spot samples from S. siderea, the total number of zooxanthellae was 56% of that in healthy tissue; dark spot-affected specimens of S. michelinii showed a 14% decrease in the number of zooxanthellae compared to healthy tissue samples. Mitotic indices of zooxanthellae from healthy specimens of S. sidereawere 1.20% compared to 0.40% in dark spot samples. Mitotic indices of healthy S. michelinii were 1.54% compared to 0.23% in dark spot samples, also indicating a decrease in algal cell division. Zooxanthellae from dark spot tissue are swollen and darker in pigment. Due to the changes that are evident in the symbiotic algae, we suggest that both syndromes act primarily on the zooxanthellae symbiont, and secondarily on the cnidarian host.     

Water flow influences oxygen transport and photosynthetic efficiency in corals

Recent studies indicate that the incidence and persistence of damage from coral reef bleaching are often highest in areas of restricted water motion, and that resistance to and recovery from bleaching is increased by enhanced water motion. We examined the hypothesis that water motion increases the efflux of oxygen from coral tissue thereby reducing oxidative stress on the photosynthetic apparatus of endosymbiotic zooxanthellae. We experimentally exposed colonies of Montastrea annularis and Agaricia agaricites to manipulations of water flow, light intensity, and oxygen concentration in the field using a novel mini-flume. We measured photosynthetic efficiency using a pulse amplitude modulated fluorometer to test the short-term response of corals to our manipulations. Under normal oxygen concentrations, A. agaricites showed a significant 8% increase in photosynthetic efficiency from 0.238 (± 0.032) in still water to 0.256 (± 0.037) in 15 cm s⁻¹ flow, while M. annularis exhibited no detectable change. Under high-ambient oxygen concentrations, the observed effect of flow on A. agaricites was reversed: photosynthetic efficiencies showed a significant 11% decrease from 0.236 (± 0.056) in still water to 0.211 (± 0.048) in 15 cm s⁻¹ flow. These results support the hypothesis that water motion helps to remove oxygen from coral tissues during periods of maximal photosynthesis. Flow mitigation of oxidative stress may at least partially explain the increased incidence and severity of coral bleaching in low flow areas and observations of enhanced recovery in high-flow areas.     

Acquisition of symbiotic dinoflagellates (Symbiodinium) by juveniles of the coral Acropora longicyathus

Scleractinian corals may acquire Symbiodinium from their parents (vertically) or from the environment (horizontally). In the present study, adult colonies of the coral Acropora longicyathus from One Tree Island (OTI) on the southern Great Barrier Reef (Australia) acquired two distinct varieties of symbiotic dinoflagellates (Symbiodinium) from the environment. Adult colonies had either Symbiodinium from clade C (86.7%) or clade A (5.3%), or a mixture of both clades A and C (8.0% of all colonies). In contrast, all 10-day-old juveniles were associated with Symbiodinium from clade A, while 83-day-old colonies contained clades A, C and D even though they were growing at the same location. Symbiodinium from clade A were dominant in both 10- and 83-day-old juveniles (99 and 97% of all recruits, respectively), while clade D was also found in 31% of 83-day-old juveniles. Experimental manipulation also revealed that parental association (with clade A or C), or the location within the OTI reef, did not influence which clade of symbiont was acquired by juvenile corals. The differences between the genetic identity of populations of Symbiodinium resident in juveniles and adult A. longicyathus suggest that ontogenetic changes in the symbiosis may occur during the development of scleractinian corals. Whether or not these changes are due to host selective processes or differences in the physical environment associated with juvenile versus adult colonies remains to be determined.     

Coral disease physiology: the impact of Acroporid white syndrome on <Emphasis Type="Italic">Symbiodinium</Emphasis>

Acroporid white syndrome, a disease-like syndrome from the Great Barrier Reef, results from degenerative host tissue at lesion borders. Tissue preceding lesion borders appears visually healthy, but it is currently unclear whether the endosymbiotic zooxanthellae (Symbiodinium) are physiologically impacted. Compared to healthy colonies, this study found no significant differences in symbiont density, mitotic index or chlorophyll a content in tissue bordering (0 cm), and 8 cm away from white syndrome lesions. Using chlorophyll a fluorescence techniques, the border tissue did not appear to be photosynthetically compromised, and Symbiodinium extracted from this area were photosynthetically competent. Transmission electron microscopy revealed extensive degeneration of host tissues surrounding symbionts in affected areas, however, Symbiodinium cells were structurally intact with no sign of in situ degradation. Collectively, these results suggest that Symbiodinium at white syndrome lesion borders exist in a dynamic intra-cellular state during active host tissue loss, yet remain physiologically uncompromised.     

Spatial Epidemiology of Caribbean Yellow Band Syndrome in <Emphasis Type="Italic">Montastrea</Emphasis> spp. Coral in the Eastern Yucatan,Mexico

Caribbean yellow band syndrome (YBS) is a poorly understood, progressively fatal disease primarily affecting Montastraea spp. coral. This disease has exhibited rapid spread throughout the entire Caribbean over the last few decades. In this study, geographical information systems (GIS) and spatial statistics were used to analyze the distribution of YBS in Akumal Bay, Mexico, and host and environmental risk factors for YBS were evaluated epidemiologically. In this Bay, there are hundreds of colonies of Montastraea annularis from 1 m depths inside the fringing reefs to reef crests and beyond. Of 63 corals that were evaluated, the overall prevalence of YBS in Akumal Bay was 28.6%, with 35.7% in large colonies, 23.8% in medium-sized colonies, and 23.8% in small colonies, where small colonies were <200 cm diameter, medium-sized were 200–500 cm, and large were >500 cm. Lesions covered 3.8% (±1.3 s.e.) of the surface of colonies assessed, compared with a mean percentage of dead colony cover of 54.4% (±4.2 s.e.). Analysis for spatial clustering documented that M. annularis colonies (well and sick) were highly spatially clustered, compared to expected complete spatial randomness. However, compared with all M. annularis corals, colonies with YBS tended to be less spatially clustered (i.e. within the overall clustered spatial distribution of M. annularis colonies, YBS-affected colonies’ distribution was more regular). These findings are consistent with several hypotheses for the etiology of YBS, including near-shore pathogens or toxins either directly inducing disease or indirectly leading to disease by increasing host susceptibility. Ongoing investigations into the management and cause of YBS can use this information to develop management strategies and more efficiently target future sampling.     

The effects of prolonged “bleaching” on the tissue biomass and reproduction of the reef coral Montastrea annularis

Colonies of Montastrea annularis from Carysfort Reef, Florida, that remained bleached seven months after the 1987 Caribbean bleaching event were studied to determine the long term effects of bleaching on coral physiology. Two types of bleached colonies were found: colonies with low numbers of zooxanthellae with normal pigment content, and a colony with high densities of lowpigment zooxanthellae. In both types, the zooxanthellae had an abnormal distribution within polyp tissues: highest densities were observed in basal endoderm and in mesenteries where zooxanthellae are not normally found. Bleached corals had 30% less tissue carbon and 44% less tissue nitrogen biomass per skeletal surface area, but the same tissue C:N ratio as other colonies that either did not bleach (normal) or that bleached and regained their zooxanthellae (recovered). Bleached corals were not able to complete gametogenesis during the reproductive season following the bleaching, while recovered corals were able to follow a normal gametogenic cycle. It appears that bleached corals were able to survive the prolonged period without nutritional contribution from their zooxanthellae by consuming their own structural materials for maintenance, but then, did not have the resources necessary for reproduction. The recovered corals, on the other hand, must have regained their zooxanthellae soon after the bleaching event since neither their tissue biomass nor their ability to reproduce were impaired.