Coral Nubbins Research Articles

Bioaccumulation of 63Ni in the scleractinian coral Stylophora pistillata and isolated Symbiodinium using radiotracer techniques

Development of nickel mining activities along the New Caledonia coasts threatens the biodiversity of coral reefs. Although the validation of tropical marine organisms as bioindicators of metal mining contamination has received much attention in the literature over the last decade, few studies have examined the potential of corals, the fundamental organisms of coral reefs, to monitor nickel (Ni) contamination in tropical marine ecosystems. In an effort to bridge this gap, the present work investigated the bioaccumulation of 63Ni in the scleractinian coral Stylophora pistillata and in its isolated zooxanthellae Symbiodinium, using radiotracer techniques. Results highlight the high capacities of coral tissues (zooxanthellae and host tissues) to efficiently bioconcentrate 63Ni compared to skeleton (Concentration Factors CF at 14 days of exposure are 3 orders of magnitude higher in tissues than in skeleton). When non-contaminated conditions were restored, 63Ni was more efficiently retained in skeleton than in coral tissues, with biological half-lives (Tb½) of 44.3 and 6.5 days, respectively. In addition, our work showed that Symbiodinium bioconcentrated 63Ni exponentially, with a vol/vol concentration factor at steady state (VCFSS) reaching 14,056. However, compilation of our results highlighted that despite efficient bioconcentration of 63Ni in Symbiodinium, their contribution to the whole 63Ni accumulation in coral nubbins represents less than 7%, suggesting that other biologically controlled processes occur in coral host allowing such efficient bioconcentration in coral tissues.

Coral translocation and farming as mitigation and conservation measures for coastal development in the Red Sea: Aqaba case study, Jordan

Coastal development is often at odds with coral reef conservation. In Aqaba, Jordan, authorities proposed a plan to relocate the existing port services to a new area on Al-Dirreh Bay towards the southern end of the Gulf of Aqaba. As a mitigation measure, 7000 endangered coral colonies were moved from Al-Dirreh and transplanted into degraded reef sites in Aqaba Marine Park. Sample survival and linear growth rates were determined biannually for 2 years and compared to growth rates at a control site. The overall survival rate for the transplanted colonies was estimated to exceed 87 % and the linear growth rates of the 16 species studied showed very similar values to colonies of the same species at the control site. Three species, Goniastrea edwardsi, Acropora arabensis and Stylophora pistillata, demonstrated more than 1 cm of linear growth per year. In addition, a nursery of coral nubbins from three species, Acropora hemprichii, S. pistillata and Pocillopora damicornis, was established to be a sustainable source of fully grown colonies. Their survival and linear growth rates were also measured over the 2-year period. The overall survival rate of the nubbins was 88 %, and the annual linear growth rate ranged from 0.32 cm for A. hemprichii to 0.99 cm for S. pistillata. High survival and linear growth rates indicate that the transplantation site selection and the techniques employed were successful. The results of this work support the premise that endangered coral colonies can be translocated to other reef areas and that coral nurseries can be set up to produce multiple fully grown colonies for future reef rehabilitation projects.

Coral Reef Restoration using Nursery-Reared Coral Fragments in a LGU-Academe Ushered Community Project in Masbate (Philippines)

With the declining state of Philippine coral reefs, the need for conservation and rehabilitation efforts are deemed crucial to sustaining ecological, biological and economic recovery in the reef system. However, there is yet a concrete and workable policy to be implemented in restoring and rehabilitating our reef areas aside from establishment of marine protected area (MPA). Here, we explored the prospects of coral restoration by demonstrating experiences in San Fernando, Masbate (Ticao Island) combined with the practices of the National Coral Restoration Program. In this project, some 20,000 coral nubbins utilizing ‘corals of opportunities’ were reared in 40 coral nursery units (CNUs) for six months and achieved 80% survival. They were then out-planted (c. 20,000 sq m) inside an MPA to ensure their protection and increase in live cover. The fragments were attached to dead corals using epoxy or tied in concrete nails using cable ties. Four coral genera were used namely Acropora, Seriatopora, Pocillopora, and Stylophora. About 70% coral survival was achieved after two months of transplantation. Involvement of the LGU, community and the private sector is crucial to project success. Results of the transplantation indicated effectiveness and viability of the CNU system to complement coral transplantation.

Temperature tolerance of the coral Porites lutea exposed to simulated large amplitude internal waves (LAIW)

Large-amplitude internal waves (LAIW) cause intense drops in sea water temperature (6–9°C) and acidity (0.6 pH units) within minutes, posing a major disturbance factor for shallow water corals in the Andaman Sea. During periods of elevated temperatures, however, they may provide a vital source of relief to heat-stressed corals. To assess the effect of LAIW on the thermal tolerance of the massive coral Porites lutea, we carried out a one-month reciprocal LAIW simulation experiment with coral nubbins collected from the LAIW-exposed and LAIW-sheltered sides of the Similan Islands, an offshore archipelago near the Thai Andaman shelf break (distance of sampling locations <3km). Corals from either origin were subjected to (1) ambient (29°C, pH8.39) vs. elevated (31.5°C) temperatures; and (2) ambient temperatures with simulated LAIW (30minute drops to 23.8°C, pH7.9, twice per day) vs. elevated temperatures with LAIW (30minute drops to 24.9°C, pH7.9, twice per day). Simulated LAIW reduced heat stress responses in all corals. However, nubbins from the LAIW-exposed site showed a higher tolerance to the heat stress than sheltered corals, i.e. lower bleaching- and mortality rates, higher photosynthetic performances and higher protein contents at the end of the experiment, despite identical algal symbiont genotypes (ITS-2, C15). Our results suggest that LAIW-induced nutrient availability, enhanced heterotrophic feeding and thermal variability increased the upper thermal resistance of P. lutea, supporting the notion that LAIW-exposed reefs might be important refugia for coral survival in a warming ocean.

澄黄滨珊瑚、大管孔珊瑚和丛生盔形珊瑚排卵前后小穗生长的研究

PDF HTML阅读 XML下载 导出引用 引用提醒 澄黄滨珊瑚、大管孔珊瑚和丛生盔形珊瑚排卵前后小穗生长特征 DOI: 10.5846/stxb201304070617 作者: 作者单位: 广东海洋大学水产学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家海洋公益性行业科研专项(201105012); 广东省自然科学基金项目(10152408801000005,S2011010000269); 广东省科技计划项目(2011B031100012,2012A020602050) Study of nubbins growth on Porites lutea, Goniopora djiboutiensis and Galaxea fascicularis during pre-spawn and post-spawn Author: Affiliation: Guangdong Ocean University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:澄黄滨珊瑚、大管孔珊瑚和丛生盔形珊瑚排卵前后分别采集珊瑚小穗,在实验室条件下进行为期60 d的养殖,观察其生长特性,结果表明:3种珊瑚排卵前后骨骼密度变化在1.541-2.137 g/cm3之间,差异不显著。3种珊瑚小穗的生长率表现出相对一致的变化趋势,同一规格珊瑚小穗排卵前期生长率明显高于排卵后期;同一时期大规格珊瑚小穗生长率明显高于小规格珊瑚小穗,而且养殖中后期生长较快,养殖前期生长较慢,差异显著(P < 0.05)。澄黄滨珊瑚小穗边缘组织延伸度排卵后期大于排卵前期,大管孔珊瑚小穗边缘组织延伸度排卵前期大于排卵后期,以上两种珊瑚的小规格珊瑚小穗与大规格珊瑚小穗组织延伸度相当。随着养殖时间的持续,丛生盔形珊瑚小穗螅体增殖速率加快,各养殖阶段螅体数差异显著(P < 0.05),珊瑚小穗规格和养殖季节对其小穗螅体增殖数量没有显著影响。3种珊瑚小穗生长指标间多呈显著正相关,仅大管孔珊瑚小穗初始直径、初始重量与组织延伸度间,以及丛生盔形珊瑚小穗初始重量与初始螅体数量、生长率间相关性不明显。 Abstract:In the present study, Porites lutea, Goniopora djiboutiensis and Galaxea fascicularis were collected to evaulate the nubbins growth performance before and after ovulation under laboratory condition for period of 60 d. The results of present study indicated that there were no significant differences were observed among all treatments, and the skeleton density of coral nubbins ranged from 1.541 to 2.137 g/cm3 during pre-spawn and post-spawn. Three kinds of coral growth rate exhibited relatively consistent trend, and the growth rate had significantly higher in corals of pre-spawn than those of post-spawn. The growth rate of large-sized coral spikelets was significantly higher than the small size of coral spikelets during the same period, especially, there were significant difference that the growth rate of the late breeding had more significantly rapid than those in the early breeding. For Porites lutea, the marginal tissue elongation of pre-spawn phase had greater than those of post-spawn phase, moreover, for Goniopora djiboutiensis, spikelets marginal tissue elongation greater than preovulatory late ovulation. Tissue extension of pre-spawn Goniopora djiboutiensis nubbins was higher than that of the post-spawn nubbins and that of the small nubbins was slightly higher than that of the big nubbins, but there were no significant differences. With the culture time increasing, polyp proliferation rates of Galaxea fascicularis nubbins became faster and there were significant differences in polyp proliferation numbers of different stages (P < 0.05). However, there were no significant differences between polyp size of proliferation numbe and culture season. Significant positive correlations of all growth index of nubbins among three coral species were obtained, however, there were no correlations between initial diameter and/or weight and tissue extension of Goniopora djiboutiensis nubbins, and there were no correlation between initial weight/polyp number and growth rates of Galaxea fascicularis. 参考文献 相似文献 引证文献

Acute survivorship of the deep-sea coral Lophelia pertusa from the Gulf of Mexico under acidification, warming, and deoxygenation

Changing global climate due to anthropogenic emissions of CO2 are driving rapid changes in the physical and chemical environment of the oceans via warming, deoxygenation, and acidification. These changes may threaten the persistence of species and populations across a range of latitudes and depths, including species that support diverse biological communities that in turn provide ecological stability and support commercial interests. Worldwide, but particularly in the North Atlantic and deep Gulf of Mexico, Lophelia pertusa forms expansive reefs that support biological communities whose diversity rivals that of tropical coral reefs. In this study, L. pertusa colonies were collected from the Viosca Knoll region in the Gulf of Mexico (390 to 450 m depth), genotyped using microsatellite markers, and exposed to a series of treatments testing survivorship responses to acidification, warming, and deoxygenation. All coral nubbins survived the acidification scenarios tested, between pH of 7.67 and 7.90 and aragonite saturation states of 0.92 and 1.47. However, calcification generally declined with respect to pH, though a disparate response was evident where select individuals net calcified and others exhibited net dissolution near a saturation state of 1. Warming and deoxygenation both had negative effects on survivorship, with up to 100% mortality observed at temperatures above 14oC and oxygen concentrations of approximately 1.5 ml·l-1. These results suggest that, over the short-term, climate change and OA may negatively impact L. pertusa in the Gulf of Mexico, though the potential for acclimation and the effects of genetic background should be considered in future research.

Toxicology of Household Detergents to Reef Corals

Ecotoxicological impacts (survivorship, growth) of two detergents, the linear alkylbenzene sulfonates (LAS) and the nonionic surfactants, nonylphenol ethoxylate (NPE), were examined on two branching coral species (Stylophora pistillata and Pocillopora damicornis). Nubbins assays (n = 1,890, 24-h exposures, 203-day monitoring) revealed high mortality in 1 and 5 mg/l detergents concentrations (for both species combined, LAS LC50 = 1.99 mg/l; NPE LC50 = 2.16 mg/l). Assays further showed detergent as species-specific mortalities (Stylophora LAS LC50 = 1.00 mg/l; NPE = 3.03 mg/l; Pocillopora LAS LC50 = 2.21 mg/l; NPE = 2.26 mg/l), also influenced by genotype-specific mortalities, phenomena which could downgrade genetic diversity of corals in the field, leaving frequently or chronically affected areas with detergent-resistant genotypes. Results revealed that LAS detergents were significantly more detrimental to coral nubbins than NPE detergents, resulting in high mortality and reduced tissue growth on substrates. Surprisingly, nubbins exposed to second and third LAS treatments exhibited significant higher survivorship levels than after the first exposure, whereas in all NPE treatments, nubbins’ survivorship did not significantly differ in the repeated exposures as compared to the first set of assays. This outcome, while adding to our knowledge for the toxicity of various detergents, highlights the need to reduce repeated sewage spills. Furthermore, it is recommended that reef managers should emphasize disparate detergents’ ecotoxicity on corals when establishing environmental policies.

Temporal changes in the growth of two Mediterranean cold-water coral species, in situ and in aquaria

In situ growth patterns of two-species of reef-building cold-water corals were investigated for the first time at different temporal scales, based on the redeployment of coral nubbins in their natural environment. Lophelia pertusa and Madrepora oculata were collected in November 2010 and May 2011 from the Lacaze-Duthiers canyon in the northwestern Mediterranean Sea (520m depth). Three in situ growth experiments were performed from November 2010 to May 2011, May to September 2011 and November 2010 to September 2011. For comparison, aquaria experiments over comparable lengths of time were conducted with coral colonies collected in November 2010. In the canyon, new polyps from M. oculata and L. pertusa displayed similar growth rates in summer (5.8±3.8 and 7.3±1.7mmyr−1 respectively), but M. oculata growed significantly slower during winter/spring than L. pertusa (4.1±1.8 and 8.4±2.7mmyr−1 respectively). Budding rates however (the rate of new polyp addition per mother polyp per year) were similar between both species in winter/spring (45±40% for M. oculata and 48±72% for L. pertusa), but were significantly lower in summer for M. oculata (14±19%) compared to L. pertusa (58±94%). This seasonal difference in the growth between L. pertusa and M. oculata might reflect differences in species-specific physiology (such as reproduction) or feeding strategy, or a higher sensitivity of M. oculata to the variability of food supply in the Lacaze-Duthiers canyon resulting from periodic cascading events. The comparison of in situ and aquaria growth experiments showed no significant differences for budding and new polyp growth rates, which supports the validity of aquaria experiments for these kinds of investigations. However the budding rates observed were consistently lower in coral maintained in aquaria than those in in situ conditions, a finding which is to be considered when extrapolating laboratory based investigation results to the naturally occurring coral ecosystem.

High natural gene expression variation in the reef-building coral Acropora millepora: potential for acclimative and adaptive plasticity.

BackgroundEcosystems worldwide are suffering the consequences of anthropogenic impact. The diverse ecosystem of coral reefs, for example, are globally threatened by increases in sea surface temperatures due to global warming. Studies to date have focused on determining genetic diversity, the sequence variability of genes in a species, as a proxy to estimate and predict the potential adaptive response of coral populations to environmental changes linked to climate changes. However, the examination of natural gene expression variation has received less attention. This variation has been implicated as an important factor in evolutionary processes, upon which natural selection can act.ResultsWe acclimatized coral nubbins from six colonies of the reef-building coral Acropora millepora to a common garden in Heron Island (Great Barrier Reef, GBR) for a period of four weeks to remove any site-specific environmental effects on the physiology of the coral nubbins. By using a cDNA microarray platform, we detected a high level of gene expression variation, with 17% (488) of the unigenes differentially expressed across coral nubbins of the six colonies (jsFDR-corrected, p < 0.01). Among the main categories of biological processes found differentially expressed were transport, translation, response to stimulus, oxidation-reduction processes, and apoptosis. We found that the transcriptional profiles did not correspond to the genotype of the colony characterized using either an intron of the carbonic anhydrase gene or microsatellite loci markers.ConclusionOur results provide evidence of the high inter-colony variation in A. millepora at the transcriptomic level grown under a common garden and without a correspondence with genotypic identity. This finding brings to our attention the importance of taking into account natural variation between reef corals when assessing experimental gene expression differences. The high transcriptional variation detected in this study is interpreted and discussed within the context of adaptive potential and phenotypic plasticity of reef corals. Whether this variation will allow coral reefs to survive to current challenges remains unknown.

Gene expression patterns of the coral Acropora millepora in response to contact with macroalgae.

Contact with macroalgae often causes coral mortality, but the roles of abrasion versus shading versus allelopathy in these interactions are rarely clear and effects on gene expression are unknown. Identification of gene expression changes within corals in response to contact with macroalgae can provide insight into the mode of action of allelochemicals, as well as reveal transcriptional strategies of the coral that mitigate damage from this competitive interaction, enabling the coral to survive. Gene expression responses of the coral Acropora millepora after long-term (20 d) direct contact with macroalgae (Chlorodesmis fastigiata, Dictyota bartayresiana, Galaxaura filamentosa and Turbinaria conoides) and short-term (1 h and 24 h) exposure to C. fastigiata thalli and their hydrophobic extract were assessed. After 20 d of exposure, T. conoides thalli elicited no significant change in visual bleaching or zooxanthellae PSII quantum yield within A. millepora nubbins, but stimulated the greatest alteration in gene expression of all treatments. Chlorodesmis fastigiata, D. bartayresiana and G. filamentosa caused significant visual bleaching of coral nubbins and reduced the PSII quantum yield of associated zooxanthellae after 20 d, but elicited fewer changes in gene expression relative to T. conoides at day 20. To evaluate initial molecular processes leading to reduction of zooxanthella PSII quantum yield, visual bleaching, and coral death, short-term exposures to C. fastigiata thalli and hydrophobic extracts were conducted; these interactions revealed protein degradation and significant changes in catalytic and metabolic activity within 24 h of contact. These molecular responses are consistent with the hypothesis that allelopathic interactions lead to alteration of signal transduction and an imbalance between reactive oxidant species production and antioxidant capabilities within the coral holobiont. This oxidative imbalance results in rapid protein degradation and eventually to apoptosis and/or necrosis when compensatory transcriptional action by the coral holobiont insufficiently mitigates damage by the allelochemicals of C. fastigiata.

Post-bleaching recovery of transplanted coral nubbins in Abu Al Abyad Island of Abu Dhabi, United Arab Emirates

Post-bleaching recovery of transplanted coral nubbins in Abu Al Abyad Island of Abu Dhabi, United Arab Emirates

Enduring physiological and reproductive benefits of enhanced flow for a stony coral

We experimentally examined the in situ, long‐term effects of flow on the coral Pocillopora verrucosa over a 2‐yr period. Eighteen coral nubbins were positioned on stages protected from the ambient flow with transparent walls. Six of the corals were exposed to “enhanced flow” with underwater pumps (15‐20 cm s‐1), while another other six were grown under “reduced‐flow” conditions (~ 1 cm s‐1), and a further six nubbins were set up as a control treatment exposed to ambient natural flow conditions on stages without walls. Mortality was 50% in the reduced‐flow experiment. Compared with the reduced‐flow and the control treatments, colonies growing in enhanced‐flow conditions developed a more compact morphology and had significantly higher chlorophyll and protein concentrations, a higher density of zooxanthellae, and, most importantly, higher reproductive output. However, corals grown in reduced‐flow conditions had lower skeleton density compared with those grown under ambient flow or enhanced flow. Flow rate had no measurable influence on average pH at the site of calcification as monitored by skeletal boron isotopic composition (δ11B). Hence, the skeletal δ11B‐pH proxy in this coral appears to be independent of flow and the biological attributes that are modulated by flow, such as zooxanthellae density, chlorophyll concentrations, and rates of photosynthesis, respiration, and calcification. Calcification site pH in all colonies was raised by +0.3 relative to ambient seawater pH. Together with light, flow should be considered a key abiotic factor determining core biological characteristics of P. verrucosa.

Assessing the effects of polychlorinated biphenyls (Aroclor 1254) on a scleractinian coral ( Stylophora pistillata) at organism, physiological, and molecular levels

Polychlorinated biphenyls (PCBs) are a group of widespread contaminants, and accumulation of PCBs has been observed in corals in the field. However, the toxic effects of PCBs on corals have not been investigated. In this study, we tested short and long term toxicity of Aroclor 1254, a commercial PCB mixture, on the scleractinian coral Stylophora pistillata. Coral nubbins were incubated in either control seawater or seawater dosed with PCBs (approximately 300 ng/L) for 96 h. The effect of PCB exposure on coral gene expression at 4 h post exposure was tested with the suppression subtractive hybridization (SSH) and quantitative PCR methods. Photosystem II activity of the zooxanthellae was measured at 96 h. After the exposure, nubbins were moved into clean seawater and their survival and growth were observed for another 50 days. All nubbins survived during the exposure and the following 50-d recovery period. Photosystem II activity and coral growth were not affected by PCB exposure in this study. Fifty-four clones were sequenced for gene expression analysis, and 15% of these sequences were identified, including genes involved in general stress response, peptide metabolism, cellular receptor, cytoskeleton organization, membrane trafficking, and oxidative stress response. However, the quantitative PCR did not show significant difference in the five selected genes. In conclusion, acute exposure of S. pistillata to Aroclor 1254 at 300 ng/L did not affect coral survival, photosynthesis or growth but may alter the expression of certain genes involved in various important cellular functions. The nubbin technique proved to be an efficient approach to simultaneously characterize the impact of PCBs on the corals at multiple biological levels.

Chemical and Physical Environmental Conditions Underneath Mat- and Canopy-Forming Macroalgae, and Their Effects on Understorey Corals

Disturbed coral reefs are often dominated by dense mat- or canopy-forming assemblages of macroalgae. This study investigated how such dense macroalgal assemblages change the chemical and physical microenvironment for understorey corals, and how the altered environmental conditions affect the physiological performance of corals. Field measurements were conducted on macroalgal-dominated inshore reefs in the Great Barrier Reef in quadrats with macroalgal biomass ranging from 235 to 1029 g DW m−2 dry weight. Underneath mat-forming assemblages, the mean concentration of dissolved oxygen was reduced by 26% and irradiance by 96% compared with conditions above the mat, while concentrations of dissolved organic carbon and soluble reactive phosphorous increased by 26% and 267%, respectively. The difference was significant but less pronounced under canopy-forming assemblages. Dissolved oxygen declined and dissolved inorganic carbon and alkalinity increased with increasing algal biomass underneath mat-forming but not under canopy-forming assemblages. The responses of corals to conditions similar to those found underneath algal assemblages were investigated in an aquarium experiment. Coral nubbins of the species Acropora millepora showed reduced photosynthetic yields and increased RNA/DNA ratios when exposed to conditions simulating those underneath assemblages (pre-incubating seawater with macroalgae, and shading). The magnitude of these stress responses increased with increasing proportion of pre-incubated algal water. Our study shows that mat-forming and, to a lesser extent, canopy-forming macroalgal assemblages alter the physical and chemical microenvironment sufficiently to directly and detrimentally affect the metabolism of corals, potentially impeding reef recovery from algal to coral-dominated states after disturbance. Macroalgal dominance on coral reefs therefore simultaneously represents a consequence and cause of coral reef degradation.

The effect of different flow regimes on the growth and metabolic rates of the scleractinian coral Galaxea fascicularis

To study the effect of water flow on coral growth, four series of ten coral nubbins of Galaxea fascicularis were exposed to four different flow regimes (0, 10, 20, and 25 cm s−1, bidirectional flow) for 42 weeks. Buoyant weight, surface area, and polyp number were measured at regular intervals. Net photosynthesis and dark respiration were measured at the corresponding flow speeds, and daily amount of photosynthetic carbon left for coral growth was calculated. Finally, skeletal density and CN content, chlorophyll concentration and dry weight of coral tissue were determined for each coral. Specific growth rate (in day−1) decreased with time in each flow treatment. Absence of flow resulted in significantly lower growth rates. Average specific growth rate calculated over the entire experiment was not significantly different between 10 and 20 cm s−1, while it was significantly higher at 25 cm s−1. From 10 to 25 cm s−1, average net photosynthetic rate decreased and average dark respiration rate did not change significantly. Scope for growth based on phototrophic carbon decreased with increasing flow. Growth was not positively correlated with either photosynthesis or respiration, or scope for growth. It is suggested that higher flow rates reduce the chance of disturbance of coral growth by competing algae or cyanobacteria, allowing corals to grow more readily with the maximum specific growth rate possible under the given environmental conditions. Notably, other effects of increased flow, such as increased respiratory rates and increased (in)organic nutrient uptake, might have been equally responsible for the increased growth of the corals in 25 cm s−1.

Response of two species of Indo-Pacific corals, Porites cylindrica and Stylophora pistillata, to short-term thermal stress: The host does matter in determining the tolerance of corals to bleaching

The role of both host and dinoflagellate symbionts was investigated in the response of reef-building corals to thermal stress in the light. Replicate coral nubbins of Stylophora pistillata and Porites cylindrica from the GBR were exposed to either 28 °C (control) or 32 °C for 5 days before being returned to an ambient reef temperature (28 °C). S. pistillata was found to contain either Symbiodinium genotype C1 or C8a, while P. cylindrica had type C15 based on ITS genotyping. Analysis of the quantum yield of photosystem (PS) II fluorescence of the symbionts in P. cylindrica showed that light-induced excitation pressure on the C15 Symbiodinium was significantly less, and the steady state quantum yield of PSII fluorescence at noon ( ΔF/Fm′) greater, than that measured in C1/C8a Symbiodinium sp. from S. pistillata. Immunoblots of the PS II D1 protein were significantly lower in Symbiodinium from S. pistillata compared to those in P. cylindrica after exposure to thermal stress. The biochemical markers, heat-stress protein (HSP) 70 and superoxide dismutase (SOD), were significantly greater in P. cylindrica before the experiment, and both species of coral increased their biosynthesis of HSP 70 and SOD when exposed to thermal stress. Concentrations of MAAs, glycerol, and lipids were not significantly affected by thermal stress in these experiments, but DNA damage was greater in heat-stressed S. pistillata compared to P. cylindrica. There was minimal coral mucus, which accounts for up to half of the total energy budget of a coral and provides the first layer of defense for invading microbes, produced by S. pistillata after heat stress compared to P. cylindrica. It is concluded that P. cylindrica contains a heat resistant C15 Symbiodinium and critical host proteins are present at higher concentrations than observed for S. pistillata, the combination of which provides greater protection from bleaching conditions of high temperature in the light.

The effect of irradiance on long-term skeletal growth and net photosynthesis in Galaxea fascicularis under four light conditions

The relation between irradiance, skeletal growth and net photosynthesis was studied for the scleractinian coral Galaxea fascicularis to provide experimental evidence for mediation of light-enhanced calcification through photosynthesis. The hypothesis was tested that skeletal growth and photosynthesis are linearly correlated. A long-term experiment was performed in a closed-circuit aquarium system, in which four series of nine nubbins (single polyp clones of a coral colony) of Galaxea fascicularis were exposed to four light treatments (10L:14D): 144 W T8 fluorescent lighting providing an irradiance of 68 µE/m 2/s and 70, 250 and 400 W Metal Halide lighting providing an irradiance of 38 µE/m 2/s, 166 µE/m 2/s and 410 µE/m 2/s, respectively. Growth of these nubbins was measured as buoyant weight at different time intervals in a 294 day experiment. A light-saturation curve for photosynthesis was measured in a respirometric flow cell using a 54 week Galaxea fascicularis colony grown at 60 µE/m 2/s. No saturation of net photosynthesis of Galaxea fascicularis was found at the irradiances tested. The specific growth rate (µ, in day - 1 ) of the coral nubbins increased with irradiance. Whereas irradiance varied 11-fold (38 to 410 µE/m 2/s), buoyant weight (increase after 294 days) increased 5.7 times (2243 to 12374 mg), specific growth rate (1-294 days) increased 1.6 times (0.0103 to 0.0161 day - 1 ), while net photosynthetic rate increased 8.9 times (0.009 µmol O 2/min/cm 2 to 0.077 µmol O 2/min/cm 2). The increase of specific growth rate with irradiance was less than expected based on the increase in net photosynthetic rate with irradiance. This discrepancy between potential energy produced in photosynthesis and energy used for skeletal growth indicates that skeletal growth is not limited by photosynthetic potential at high irradiance levels.

Coral calcification responds to seawater acidification: a working hypothesis towards a physiological mechanism

The decrease in the saturation state of seawater, Ω, following seawater acidification, is believed to be the main factor leading to a decrease in the calcification of marine organisms. To provide a physiological explanation for this phenomenon, the effect of seawater acidification was studied on the calcification and photosynthesis of the scleractinian tropical coral Stylophora pistillata. Coral nubbins were incubated for 8 days at three different pH (7.6, 8.0, and 8.2). To differentiate between the effects of the various components of the carbonate chemistry (pH, CO32−, HCO3−, CO2, Ω), tanks were also maintained under similar pH, but with 2-mM HCO3− added to the seawater. The addition of 2-mM bicarbonate significantly increased the photosynthesis in S. pistillata, suggesting carbon-limited conditions. Conversely, photosynthesis was insensitive to changes in pH and pCO2. Seawater acidification decreased coral calcification by ca. 0.1-mg CaCO3 g−1 d−1 for a decrease of 0.1 pH units. This correlation suggested that seawater acidification affected coral calcification by decreasing the availability of the CO32− substrate for calcification. However, the decrease in coral calcification could also be attributed either to a decrease in extra- or intracellular pH or to a change in the buffering capacity of the medium, impairing supply of CO32− from HCO3−.

Intensive fish farming in the Philippines is detrimental to the reef-building coral Pocillopora damicornis

To determine the effects of fish farm effluent on the reef-building species Pocillopora damicornis, we exposed different life stages of the coral to a gradient of effluent concentrations. After 81 d no juvenile coral survived at the Fish Farm site or at the site receiving intermediate concentra- tions, and survival rates were low (<20%) at the site receiving minimal effluent concentrations and at the reference site. At the Fish Farm site, juveniles (on terracotta tiles) were completely overgrown by barnacles. Coral nubbins and mature colonies displayed similar survivorship trends along the efflu- ent gradient, i.e. higher mortality with higher effluent concentrations. At the site of intermediate exposure, surviving nubbins had skeletal growth rates half of those from the site of minimal influence and from the reference site. The mean gross photosynthesis to respiration ratio of coral branches deployed at the fish farm was below the physiological compensatory value of 1, whereas values of about 1 were attained at the sites of diminishing effluent influence. Reduced larval output in mature colonies exposed to intermediate and minimal concentrations of fish farm effluent were observed as compared to those from the reference site. No reproductive measurements could be conducted for colonies at the Fish Farm site, due to high mortality. At the larval stage, metamorphosis was dimin- ished both on substrates collected from, and tiles conditioned in, the Fish Farm environment, com- pared to those from sites of diminishing effluent influence. Hence, many aspects of coral biology are impaired by exposure to effluent from intensive fish farming.

Coral nubbins as source material for coral biological research: A prospectus

The global decline of coral reefs has raised interest in diverse aspects of coral biology, resulting in steady increase in the number of studies on physiological, ecotoxicological and molecular aspects of coral reef biology. An emerging problem in these disciplines is the shortage in source material for research. Genetically identical coral nubbins that are produced with minimal detrimental impacts on donor colonies fulfill the need for the growing demand for research. Here we detail the protocol for the preparation of coral nubbins amenable for the ornamental trade, reef restoration and research purposes.