Montipora Capitata Research Articles

Coral color and depth drive symbiosis ecology of Montipora capitata in Kāne‘ohe Bay, O‘ahu, Hawai‘i

Scleractinian corals form symbioses with diverse photosynthetic dinoflagellates (genus Symbiodinium) that confer varying levels of performance and stress tolerance to their hosts. Variation in thermal stress susceptibility (i.e., bleaching) among conspecific corals is linked to variability in symbiont community composition, yet factors driving heterogeneous symbiont associations within a population are poorly understood. To investigate potential drivers, we characterized Symbiodinium communities in Montipora capitata (N = 707 colonies) across the biophysical regions, reef types, and depth range of Kāne‘ohe Bay (Hawai‘i, USA), where this dominant reef-builder associates with Symbiodinium spp. in clade C (C31) and/or D (S. glynnii), and occurs as brown and orange color morphs. The distribution of these traits was primarily influenced by depth: orange, D-dominated colonies were more prevalent in shallow, high light environments (< 2 m), whereas brown, C-dominated colonies were more prevalent with increasing depth and light attenuation. Though either color morph could be dominated by either symbiont, brown colonies were almost exclusively C-dominated, while orange colonies were more likely to be D-dominated above 4.3 m, and C-dominated below, revealing a significant interaction between color morph and symbiosis ecology. The distribution of orange, D-dominated colonies extended deeper on patch reefs, where light penetrates deeper, compared to the more turbid, fringing reefs, further supporting light as the driver of these patterns. This work reveals that symbiont community variability may arise either from holobiont phenotypic plasticity or differential survival across light gradients, with implications for predicting coral bleaching responses and informing management applications such as selective breeding of robust corals.

Influence of salinity and sedimentation on Vibrio infection of the Hawaiian coral Montipora capitata.

Environmental cofactors alter host-pathogen interactions and influence disease dynamics by impairing host resistance and/or increasing pathogen virulence. Terrestrial runoff is recognized as a major threat to coral reef health. However, the direct links between runoff and coral disease are not clear. Montipora white syndrome (MWS) is a coral disease that occurs in the Hawaiian archipelago, can be caused by various bacterial pathogens, including Vibrio species, and is linked to conditions associated with heavy rainfall and runoff. The objective of this study was to determine whether a short-term hyposalinity stress (20 ppt for 24 h) or sedimentation stress (1000 g m-2 d-1) would influence bacterial infection of the coral Montipora capitata. Hyposalinity increased M. capitata susceptibility to infection by 2 MWS pathogens, Vibrio coralliilyticus strain OCN008 and Vibrio owensii strain OCN002. Specifically, hyposalinity allowed OCN008 to infect at lower doses (106 CFU ml-1 compared with 108 CFU ml-1) and reduced the amount of time before onset of OCN002 infection at high doses (108 CFU ml-1). In contrast, short-term sedimentation stress did not affect M. capitata infection by either of these 2 pathogens. Although several studies have found a correlation between runoff and increased coral disease prevalence in field studies, this is the first study to show that one aspect of runoff (reduced salinity) enhances bacterial infection of coral using manipulative experiments.

Discovery of SCORs: Anciently derived, highly conserved gene-associated repeats in stony corals

Stony coral (Scleractinia) genomes are still poorly explored and many questions remain about their evolution and contribution to the success and longevity of reefs. We analyzed transcriptome and genome data from Montipora capitata, Acropora digitifera, and transcriptome data from 20 other coral species. To our surprise, we found highly conserved, anciently derived, Scleractinia COral-specific Repeat families (SCORs) that are abundant in all the studied lineages. SCORs form complex secondary structures and are located in untranslated regions and introns, but most abundant in intergenic DNA. These repeat families have undergone frequent duplication and degradation, suggesting a ‘boom and bust’ cycle of invasion and loss. We speculate that due to their surprisingly high sequence identities across deeply diverged corals, physical association with genes, and dynamic evolution, SCORs might have adaptive functions in corals that need to be explored using population genomic and function-based approaches.

Divergent evolutionary histories of DNA markers in a Hawaiian population of the coral Montipora capitata.

We investigated intra- and inter-colony sequence variation in a population of the dominant Hawaiian coral Montipora capitata by analyzing marker gene and genomic data. Ribosomal ITS1 regions showed evidence of a reticulate history among the colonies, suggesting incomplete rDNA repeat homogenization. Analysis of the mitochondrial genome identified a major (M. capitata) and a minor (M. flabellata) haplotype in single polyp-derived sperm bundle DNA with some colonies containing 2–3 different mtDNA haplotypes. In contrast, Pax-C and newly identified single-copy nuclear genes showed either no sequence differences or minor variations in SNP frequencies segregating among the colonies. Our data suggest past mitochondrial introgression in M. capitata, whereas nuclear single-copy loci show limited variation, highlighting the divergent evolutionary histories of these coral DNA markers.

Effects of substratum on the growth and survivorship of Montipora capitata and Porites lobata transplants

Artificial transplantation of corals is a common method used to restore damaged or unhealthy coral assemblages. Though a number of studies have successfully transplanted coral fragments, there is no general consensus on the type of substratum to be used. The present study focused on the growth and survivorship of Montipora capitata (rice coral) and Porites lobata (lobe coral) fragments, which were transplanted onto different natural and synthetic substrata. No significant differences in coenosarc tissue growth or survivorship were observed between the species. Measurements after 184days of growth, found transplant growth to be significantly higher on rhyolite breccia and amorphous coral skeletons than on black ʻAʻā lava. Nevertheless, no significant differences were observed between any of the other substrata. After 365days of growth, survivorship was also observed to not be significantly different between substrata; with the only exception of being lower on glass substratum. It is hypothesized that success in a coral reef restoration project is largely determined by the actual coral fragmentation and transplantation process; as no distinct substratum affinity was observed for M. capitata and P. lobata transplants.

Investigating the spatial distribution of growth anomalies affecting Montipora capitata corals in a 3-dimensional framework

Diseases have caused significant reductions in coral populations throughout the global ocean. Despite a substantial effort to thoroughly characterize the epizootiology and etiology of coral diseases, little is known about the distribution and spatial clustering of disease lesions on affected coral colonies. This study investigated spatial clustering of the coral disease, growth anomaly (GA), which exhibits high levels of prevalence and severity in Montipora capitata and other corals at Wai’ōpae, southeast Hawai’i Island. Like many other coral diseases, the patterns of disease spread and transmissibility of GA remains unknown. We utilized cutting-edge 3D reconstruction techniques to map the precise spatial distribution of GAs on affected coral colonies. Three statistical measures, Ripley’s K, Moran’s I, and the Kolmogorov-Smirnov test were used to determine if the GA lesions were distributed in a non-random pattern. Each measure showed the GA lesions exhibited distinct spatial clustering on all ten affected colonies analyzed in this study. Our study is not only the first 3D analysis of intra-colony disease clustering, but also provides a novel approach for investigating and quantifying levels of disease clustering in order to improve our understanding of coral disease epizootiology, transmission, and etiology.

Seasonal and annual calcification rates of the Hawaiian reef coral, Montipora capitata, under present and future climate change scenarios

The response of corals to future conditions of global warming and ocean acidification (OA) is a topic of considerable interest. However, little information is available on the seasonal interaction between temperature, pCO2, and irradiance under ecologically relevant experimental conditions. Controlled experiments were performed in continuous-flow mesocosms under full solar radiation to describe the direct and interactive effects of temperature, irradiance, and pCO2 on growth of a Hawaiian reef building coral (Montipora capitata) over an annual cycle. Corals were subjected to 12 experimental treatments consisting of two pCO2 levels (present-day levels, 2× present), two temperature regimes (ambient, heated +2°C), and three conditions of irradiance (ambient, 50 and 90% reduction). A multiple polynomial regression model with full factorial fixed factors (temperature, pCO2, irradiance) was developed. Temperature and irradiance were the primary factors driving net calcification (Gnet) rates of M. capitata, with pCO2 playing a lesser role. Gnet showed a curvilinear response to irradiance and temperature, which defines thresholds at the end members. Also, high irradiance regimes under elevated temperatures showed a negative synergistic effect on Gnet. Therefore, decreasing irradiance penetration resulting from greater depth and/or higher turbidity will lower the impact of ocean warming on M. capitata. Results suggest that under future climate conditions, the interaction of environmental parameters may shift seasonal patterns in Gnet and timing of growth optima for M. capitata. Ocean warming in shallow water environments with high irradiance poses a more immediate threat to coral growth than acidification for this dominant coral species. In the future, increased temperature and the interaction between high irradiance and high temperature will be the main factors controlling Gnet with OA playing a less important role. This observation is congruent with other reports that high temperature combined with high irradiance is the main cause of high coral mortality during mass bleaching events.

Relative sensitivity of five Hawaiian coral species to high temperature under high-pCO2 conditions

Coral reef ecosystems are presently undergoing decline due to anthropogenic climate change. The chief detrimental factors are increased temperature and increased pCO2. The purpose of this study was to evaluate the effect of these two stressors operating independently and in unison on the biological response of common Hawaiian reef corals. Manipulative experiments were performed using five species (Porites compressa, Pocillopora damicornis, Fungia scutaria, Montipora capitata, and Leptastrea purpurea) in a continuous-flow mesocosm system under natural sunlight conditions. Corals were grown together as a community under treatments of high temperature (2 °C above normal maximum summer temperature), high pCO2 (twice present-day conditions), and with both factors acting in unison. Control corals were grown under present-day pCO2 and at normal summer temperatures. Leptastrea purpurea proved to be an extremely hardy coral. No change in calcification or mortality occurred under treatments of high temperature, high pCO2, or combined high temperature–high pCO2. The remaining four species showed reduced calcification in the high-temperature treatment. Two species (L. purpurea and M. capitata) showed no response to increased pCO2. Also, high pCO2 ameliorated the negative effect of high temperature on the calcification rates of P. damicornis. Mortality was driven primarily by high temperature, with a negative synergistic effect in P. compressa only in the high-pCO2–high-temperature treatment. Results support the observation that biological response to temperature and pCO2 elevation is highly species-specific, so generalizations based on response of a single species might not apply to a diverse and complex coral reef community.

Emerging coral diseases in Kāne'ohe Bay, O'ahu, Hawai'i (USA): two major disease outbreaks of acute Montipora white syndrome.

In March 2010 and January 2012, we documented 2 widespread and severe coral disease outbreaks on reefs throughout Kāne'ohe Bay, Hawai'i (USA). The disease, acute Montipora white syndrome (aMWS), manifested as acute and progressive tissue loss on the common reef coral M. capitata. Rapid visual surveys in 2010 revealed 338 aMWS-affected M. capitata colonies with a disease abundance of (mean ± SE) 0.02 ± 0.01 affected colonies per m of reef surveyed. In 2012, disease abundance was significantly higher (1232 aMWS-affected colonies) with 0.06 ± 0.02 affected colonies m(-1). Prior surveys found few acute tissue loss lesions in M. capitata in Ka¯ne'ohe Bay; thus, the high number of infected colonies found during these outbreaks would classify this as an emerging disease. Disease abundance was highest in the semi-enclosed region of south Kāne'ohe Bay, which has a history of nutrient and sediment impacts from terrestrial runoff and stream discharge. In 2010, tagged colonies showed an average tissue loss of 24% after 1 mo, and 92% of the colonies continued to lose tissue in the subsequent month but at a slower rate (chronic tissue loss). The host-specific nature of this disease (affecting only M. capitata) and the apparent spread of lesions between M. capitata colonies in the field suggest a potential transmissible agent. The synchronous appearance of affected colonies on multiple reefs across Kāne'ohe Bay suggests a common underlying factor. Both outbreaks occurred during the colder, rainy winter months, and thus it is likely that some parameter(s) associated with winter environmental conditions are linked to the emergence of disease outbreaks on these reefs.

Potential bleaching effects on coral reproduction

Bleaching profoundly impacts coral reproduction, often for years after an event. However, detailed reproductive characteristics of coral after bleaching have not been broadly described, especially as they relate to cryopreservation. Therefore, in the present study we measured several reproductive characteristics in coral in Kaneohe Bay, Hawaii, for two species, namely Fungia scutaria and Montipora capitata, during the bleaching period of 2014 and 2015. We examined spawning periods, egg morphometry, sperm concentration, fresh and cryopreserved sperm motility exposed to different concentrations of dimethyl sulfoxide, time of first cleavage, larval survival with fresh and cryopreserved spermatozoa, infection success and settlement success. Many of these reproductive parameters were reduced in 2015, especially sperm motility. Once the reduced-motility spermatozoa from 2015 post-bleach were cryopreserved, there was a steep decline in post-thaw viability and this would prevent any substantive further use of these samples in reproduction for conservation benefit. Worldwide, as bleaching events become more frequent, the ability to bank and conserve coral ex situ may be significantly reduced. Thus, it is imperative that while genetic diversity is still high in these populations, intensive efforts are made to bank coral species during non-bleaching periods.

The effects of growth anomaly on susceptibility of Montipora capitata to turf algal overgrowth

One of the most prominent coral diseases in Hawai‘i is growth anomaly (GA) of the skeleton. GA reduces key biological functions of Montipora capitata, but the effect of this disease on the ecological competitiveness of the coral has not been investigated. This study evaluated the effect of the GA on the susceptibility of an endemic Hawaiian coral M. capitata to algal overgrowth at Wai‘ōpae, Hawai‘i. Field surveys and photo analyses were conducted to collect epizootiological data. A relationship was found between GA severity and turf algal growth at the colony level; however, this relationship was weaker than expected. Despite the fact that GA lesions can provide areas of protuberant exposed coral skeleton, turf algal overgrowth was no more prevalent on GA-affected colonies than on unaffected colonies. As algal overgrowth is ephemeral compared to the progression of GA, we suggest that filamentous algae takes advantage of ideal environmental conditions regardless of the availability of new surfaces to invade presented by GA lesions.

Effects of toxic compounds in Montipora capitata on exogenous and endogenous zooxanthellae performance and fertilization success.

Studies have identified chemicals within the stony coral genus Montipora that have significant biological activities. For example, Montiporic acids A and B and other compounds have been isolated from the adult tissue and eggs of Montipora spp. and have displayed antimicrobial activity and cytotoxicity in cultured cells. The ecological role of these toxic compounds is currently unclear. This study examines the role these toxins play in reproduction. Toxins were found in the eggs and larvae of the coral Montipora capitata. Releasing these toxins by crushing both the eggs and larvae resulted in irreversible inhibition of photosynthesis in endogenous and exogenous zooxanthellae within minutes. Moreover, these toxins were stable, as frozen storage of eggs and larvae did not affect toxicity. Photosynthetic competency of Porites compressa zooxanthellae treated with either frozen or fresh, crushed eggs was inhibited similarly (P > 0.05, ANCOVA). Addition of toxic eggs plugs to live P. compressa fragments caused complete tissue necrosis under the exposed area on the fragments within 1 week. Small volumes of M. capitata crushed eggs added to sperm suspensions reduced in vitro fertilization success by killing the sperm. After 30 min, untreated sperm maintained 90 ± 1.9% SEM motility while those treated with crushed eggs were rendered immotile, 4 ± 1.4% SEM. Flow cytometry indicated membrane disruption of the immotile sperm. Fertilization success using untreated sperm was 79 ± 4% SEM, whereas the success rate dropped significantly after exposure to the crushed eggs, 1.3 ± 0% SEM. Unlike the eggs and the larvae, M. capitata sperm did not reduce the photosynthetic competency of P. compressa zooxanthellae, suggesting the sperm was nontoxic. The identity of the toxins, cellular mechanism of action, advantage of the toxins for M. capitata and their role on the reef are still unknown.

Species-specific differences in thermal tolerance may define susceptibility to intracellular acidosis in reef corals

It is widely acknowledged that temperature stress affects an organism’s sensitivity to ocean acidification and vice versa, yet it is not clear how the two are mechanistically linked. Here, we induced thermal stress in two coral species with differing bleaching susceptibilities to measure how a reduction in photosynthetic performance impacts intracellular pH (pHi) regulation in the symbiotic dinoflagellates (Symbiodinium sp.) and their host coral cells. Our hypothesis was that thermally induced photosynthetic dysfunction in the symbiont would prevent the efficient removal of additional CO2, lowering its buffering capacity and thus increasing the host cell’s susceptibility to intracellular acidosis. To test this, we exposed Pocillopora damicornis (a thermally sensitive coral) and Montipora capitata (a thermally resilient coral) to four different temperature treatments (23.8, 25.5, 28 and 31 °C) for 1 week. We then isolated intact symbiotic coral endodermal cells, placed them in a live-cell chamber attached to a confocal microscope and bathed them in CO2-acidified seawater (~pH 7.6) for 30 min, before measuring the light-adapted pHi of both the host cell and its symbiont. Cells isolated from P. damicornis were more prone to cellular acidosis (declines in pHi of 11 and 8 % in host and symbiont, respectively, at 31 °C relative to 23.8 °C) than cells isolated from M. capitata (5 and 4 %, respectively). These results highlight the important role of Symbiodinium productivity (in addition to a range of physico-chemical factors such as skeletal morphology and tissue pigmentation) in determining the sensitivity of corals to rising sea surface temperatures and ocean acidification.

Complete Genome Sequence of Pseudoalteromonas sp. Strain OCN003, Isolated from Kāne'ohe Bay, O'ahu, Hawaii.

Pseudoalteromonas sp. strain OCN003 is a marine gammaproteobacterium that was isolated from a diseased colony of the common Hawaiian reef coral, Montipora capitata, found on a reef surrounding Moku o Lo’e in Kāne’ohe Bay, Hawaii. Here, we report the complete genome of Pseudoalteromonas sp. strain OCN003.

Response of reef corals on a fringing reef flat to elevated suspended-sediment concentrations: Moloka'i, Hawai'i.

A long-term (10 month exposure) experiment on effects of suspended sediment on the mortality, growth, and recruitment of the reef corals Montipora capitata and Porites compressa was conducted on the shallow reef flat off south Molokaʻi, Hawaiʻi. Corals were grown on wire platforms with attached coral recruitment tiles along a suspended solid concentration (SSC) gradient that ranged from 37 mg l−1 (inshore) to 3 mg l−1 (offshore). Natural coral reef development on the reef flat is limited to areas with SSCs less than 10 mg l−1 as previously suggested in the scientific literature. However, the experimental corals held at much higher levels of turbidity showed surprisingly good survivorship and growth. High SSCs encountered on the reef flat reduced coral recruitment by one to three orders of magnitude compared to other sites throughout Hawaiʻi. There was a significant correlation between the biomass of macroalgae attached to the wire growth platforms at the end of the experiment and percentage of the corals showing mortality. We conclude that lack of suitable hard substrate, macroalgal competition, and blockage of recruitment on available substratum are major factors accounting for the low natural coral coverage in areas of high turbidity. The direct impact of high turbidity on growth and mortality is of lesser importance.

Lectins stain cells differentially in the coral, Montipora capitata

A limitation in our understanding of coral disease pathology and cellular pathogenesis is a lack of reagents to characterize coral cells. We evaluated the utility of plant lectins to stain tissues of a dominant coral, Montipora capitata, from Hawaii. Of 22 lectins evaluated, nine of these stained structures in the upper or basal body wall of corals. Specific structures revealed by lectins that were not considered distinct or evident on routine hematoxylin and eosin sections of coral tissues included apical and basal granules in gastrodermis and epidermis, cnidoglandular tract and actinopharynx cell surface membranes, capsules of mature holotrichous isorhizas, and perivitelline and periseminal cells. Plant lectins could prove useful to further our understanding of coral physiology, anatomy, cell biology, and disease pathogenesis.

Regional population structure of &lt;I&gt;Montipora capitata&lt;/I&gt; across the Hawaiian Archipelago

Montipora capitata Dana, 1846 is one of the most successful reef-building corals in the Hawaiian Archipelago, both in terms of geographic distribution and relative abundance. Here, we examine population genetic structure using eight microsatellite loci to make inferences about exchange among geographical regions throughout Hawaiian waters to inform management and conservation efforts. We collected biopsy samples (n = 560) from colonies at each of 11 islands/atolls along the archipelago in addition to Johnston Atoll, about 1328 km to the southwest. We found very few potential clones ( 200 d), estimates of contemporary dispersal were uniformly low, with most sites being estimated at >90% self-recruitment. These data imply that the majority of M. capitata colonies found at a given island/atoll across the Hawaiian Archipelago are derived from self-recruitment, and argue for more local-scale management of coral reef resources than has been considered to date.

Localization of sensory mechanisms utilized by coral planulae to detect settlement cues

AbstractCoral planulae are induced to settle and metamorphose by contact with either crustose coralline algae or marine bacterial biofilms. Larvae of two coral species, Pocillopora damicornis and Montipora capitata, which respond to different metamorphic cues, were utilized to investigate the sensory mechanisms used to detect metamorphic cues. Because the aboral pole of the coral planula is the point of attachment to the substratum, we predicted that it is also the point of detection for cues. To determine where sensory cells for cues are localized along the body, individual larvae were transversely cut into oral and aboral portions at various levels along the oral–aboral axis, and exposed to settlement‐inducing substrata. Aboral ends of M. capitata metamorphosed, while oral ends continued to swim. However, in larvae of P. damicornis, ¾ oral ends (i.e., lacking the aboral pole) were also able to metamorphose, indicating that the cells that detect cues may be distributed along the sides of the body. These cells do not correspond to FMRFamide‐immunoreactive cells that are present throughout the body. Cesium ions induced both aboral and oral ends of larvae of both species to settle, suggesting that oral ends have not lost their capacity to metamorphose, despite lacking sensory cells to detect natural cues. To determine whether sensory cells in larvae of P. damicornis are restricted to one side of the body, swimming behavior over substrata was observed in larvae labeled with diI, a red fluorescent lipophilic membrane stain. The larvae were found to rotate around the oral–aboral axis, with their surface against the substratum, not favoring a particular side for detecting cues. While clarifying the regions of the larval body important for settlement and metamorphosis in coral planulae, we conclude that significant differences between coral species may be due to differences in the distribution of sensory structures in relation to different planular sizes.

Expression of galaxin and oncogene homologs in growth anomaly in the coral Montipora capitata

Growth anomaly (GA) is a coral disease characterized by enlarged skeletal lesions. Although negative effects of GA on several of coral's biological functions have been determined, the etiology and molecular pathology of this disease is very poorly understood. We studied the expression of 5 genes suspected to play a role in pathological development of GA in the endemic Hawaiian coral Montipora capitata, which is particularly susceptible to this disease. Transcript abundances of the 5 target genes in healthy tissue, GA-affected tissue, and unaffected tissue (apparently healthy tissue adjacent to GA) relative to 3 internal control genes (actin, NADH, and rpS3) were compared using quantitative reverse transcriptase PCR. Galaxin, which codes for a protein suspected to be involved in calcification and thus hypothesized to be differentially expressed in GA, was up-regulated in unaffected tissue but remained at baseline levels in GA tissue. The gene expressions of murine double minute 2 (MDM2) and tumor necrosis factor (TNF) remained unchanged in GA tissue. The expression of tyrosine protein kinase (TPK) and βγ-crystallin (BGC) were both down-regulated. These expression patterns were all inconsistent with the expression patterns of homologous genes in neoplastic diseases featuring similar morphological symptoms in humans. These expression data therefore suggest that the calcification mechanism is likely not enhanced in coral GA and that coral GA is not a malignant neoplasia.

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.