Microbiome variation in corals with distinct depth distribution ranges across a shallow–mesophotic gradient (15–85 m)

Mesophotic coral ecosystems (MCEs) are generally poorly studied, and our knowledge of lower MCEs (below 60 m depth) is largely limited to visual surveys. Here, we provide a first detailed assessment of the prokaryotic community associated with scleractinian corals over a depth gradient to the lower mesophotic realm (15–85 m). Specimens of three Caribbean coral species exhibiting differences in their depth distribution ranges (Agaricia grahamae, Madracis pharensis and Stephanocoenia intersepta) were collected with a manned submersible on the island of Curaçao, and their prokaryotic communities assessed using 16S rRNA gene sequencing analysis. Corals with narrower depth distribution ranges (depth-specialists) were associated with a stable prokaryotic community, whereas corals with a broader niche range (depth-generalists) revealed a higher variability in their prokaryotic community. The observed depth effects match previously described patterns in Symbiodinium depth zonation. This highlights the contribution of structured microbial communities over depth to the coral’s ability to colonize a broader depth range.     

Development of an analytical method for the determination of betaines in higher plants by capillary electrophoresis at low pH

In recent years the role of betaines in higher plants has been extensively investigated in relation to environmental stress response. This paper reports the establishment of a simple, rapid and reliable method for the determination of betaines using capillary electrophoresis (CE) at low pH. Betaines were first converted to their phenacyl esters and the crude reaction mixture was then applied directly to CE without any pre-treatment. Employing an electrolyte running solution at pH 3 gave a well-resolved electropherogram for the esters of glycine betaine (1), trigonelline, proline betaine, gamma-butyro betaine, and carnitine. The content of 1 and its variation in plant samples collected from high-salinity areas in north China and west Australia are presented.     

Upper and lower mesophotic coral reef fish communities evaluated by underwater visual censuses in two Caribbean locations

Despite more than 60 yr of coral reef research using scuba diving, mesophotic coral ecosystems (MCEs) between 30 and 150 m depth remain largely unknown. This study represents the first underwater visual census of reef fish communities in the Greater Caribbean on MCEs at depths up to 80 m in Bermuda and 130 m in Curaçao. Sampling was performed using mixed-gas closed-circuit rebreathers. Quantitative data on reef fish communities were obtained for four habitats: coral reefs (45–80 m), rhodolith beds (45–80 m), ledges (85–130 m) and walls (85–130 m). A total of 38 species were recorded in Bermuda and 66 in Curaçao. Mesophotic reef fish communities varied significantly between the two localities. MCEs in Bermuda had lower richness and abundance, but higher biomass than those in Curaçao. Richness, abundance and biomass increased with depth in Bermuda, but decreased in Curaçao. A high turnover of species was found among depth strata and between Bermuda and other Caribbean upper MCEs (45–80 m), indicating that depth was an important driver of community structure at all localities. However, local and evolutionary factors (habitat and endemism) are likely the main factors shaping communities in isolated locations such as Bermuda. High fishing pressure is evident in both localities, as total biomass of apex predators was generally low, and thus may be driving a “refugia” scenario in Bermuda, as the abundance and biomass of macro-carnivores increased with depth and distance from the coast.     

植物甜菜碱合成途径及基因工程研究进展

甜菜碱是公认的在细胞中起着无毒渗透保护作用的细胞相溶性物质 ,广泛存在于植物、动物、细菌等多种生物体中。植物中甜菜碱因其结构不同 ,其生物合成途径和催化合成所需要的酶也各不相同。综述了近年来甜菜碱生物合成途径、相关基因的克隆及基因工程研究进展 ,包括从不同生物体中克隆、鉴定的甜菜碱合成的相关基因及其定位、作用机理、同源性比较及表达差异、在转基因植物中的遗传稳定性以及转基因植物的抗盐耐旱、抗寒性等。     

Combined ocean acidification and low temperature stressors cause coral mortality

Oceans are predicted to become more acidic and experience more temperature variability—both hot and cold—as climate changes. Ocean acidification negatively impacts reef-building corals, especially when interacting with other stressors such as elevated temperature. However, the effects of combined acidification and low temperature stress have yet to be assessed. Here, we exposed nubbins of the scleractinian coral Montipora digitata to ecologically relevant acidic, cold, or combined stress for 2 weeks. Coral nubbins exhibited 100% survival in isolated acidic and cold treatments, but ~30% mortality under combined conditions. These results provide further evidence that coupled stressors have an interactive effect on coral physiology, and reveal that corals in colder environments are also susceptible to the deleterious impacts of coupled ocean acidification and thermal stress.     

Calcification in bleached and unbleached Montastraea faveolata: evaluating the role of oxygen and glycerol

All reef-building corals are symbiotic with dinoflagellates of the genus Symbiodinium, which influences many aspects of the host’s physiology including calcification. Coral calcification is a biologically controlled process performed by the host that takes place several membranes away from the site of photosynthesis performed by the symbiont. Although it is well established that light accelerates CaCO₃ deposition in reef-building corals (commonly referred to as light-enhanced calcification), the complete physiological mechanism behind the process is not fully understood. To better comprehend the coral calcification process, a series of laboratory experiments were conducted in the major Caribbean reef-building species Montastraea faveolata, to evaluate the effect of glycerol addition and/or the super-saturation of oxygen in the seawater. These manipulations were performed in bleached and unbleached corals, to separate the effect of photosynthesis from calcification. The results suggest that under normal physiological conditions, a 42% increase in seawater oxygen concentration promotes a twofold increase in dark-calcification rates relative to controls. On the other hand, the results obtained using bleached corals suggest that glycerol is required, as a metabolic fuel, in addition to an oxygenic environment in a symbiosis that has been disrupted. Also, respiration rates in symbiotic corals that were pre-incubated in light conditions showed a kinetic limitation, whereas corals that were pre-incubated in darkness were oxygen limited, clearly emphasizing the role of oxygen in this regard. These findings indicate that calcification in symbiotic corals is not strictly a “light-enhanced” or “dark-repressed” process, but rather, the products of photosynthesis have a critical role in calcification, which should be viewed as a “photosynthesis-driven” process. The results presented here are discussed in the context of the current knowledge of the coral calcification process.     

Lipid class and fatty acid compositions of the zoanthid Palythoa caesia (Anthozoa: Hexacorallia: Zoanthidea) and its chemotaxonomic relations with corals

Lipid class and fatty acid (FA) compositions of the zoanthid Palythoa caesia from the South China Sea (Vietnam) were determined and compared with those of zooxanthellate reef-building and soft corals from the same region to clarify chemotaxonomic relations between zoanthids and corals. Total lipids of P. caesia and corals were formed by the same lipid classes. The lipids of P. caesia contained specific for cnidarians monoalkyldiacylglycerols and phosphonolipids. The proportion between reserve and structural lipid classes of P. caesia was similar to that of alcyonarians (soft corals), but significantly differed from reef-building corals. This similarity may be caused by the similar energy budget of cnidarian colonies without hard exoskeleton. The distribution of polyunsaturated FAs (PUFAs), such as 22:4n-6 and 22:5n-3, indicated pathways of biosynthesis of PUFAs in Palythoa to be closer to those in reef-building corals than in soft corals. The differences in the profiles of common FAs between P. caesia and reef-building corals were showed. Zoanthid lipids contained rare Δ5,9 non-methylene-interrupted (NMI) PUFAs (with two and three double bounds), which probably originated from microorganisms associated with P. caesia. Trienoic acids Δ5,9,15–24:3 and Δ5,9,17–24:3 were found in Palythoa for the first time. NMI PUFAs, as well as total FA profile, can be used for chemotaxonomy of Palythoa.     

Comprehensive model of microalgae photosynthesis rate as a function of culture conditions in photobioreactors

In this paper, the influence of culture conditions (irradiance, temperature, pH, and dissolved oxygen) on the photosynthesis rate of Scenedesmus almeriensis cultures is analyzed. Short-run experiments were performed to study cell response to variations in culture conditions, which take place in changing environments such as outdoor photobioreactors. Experiments were performed by subjecting diluted samples of cells to different levels of irradiance, temperature, pH, and dissolved oxygen concentration. Results demonstrate the existence of photoinhibition phenomena at irradiances higher than 1,000 μE/m² s; in addition to reduced photosynthesis rates at inadequate temperatures or pH—the optimal values being 35 °C and 8, respectively. Moreover, photosynthesis rate reduction at dissolved oxygen concentrations above 20 mg/l is demonstrated. Data have been used to develop an integrated model based on considering the simultaneous influence of irradiance, temperature, pH, and dissolved oxygen. The model fits the experimental results in the range of culture conditions tested, and it was validated using data obtained by the simultaneous variation of two of the modified variables. Furthermore, the model fits experimental results obtained from an outdoor culture of S. almeriensis performed in an open raceway reactor. Results demonstrate that photosynthetic efficiency is modified as a function of culture conditions, and can be used to determine the proximity of culture conditions to optimal values. Optimal conditions found (T?=?35 °C, pH?=?8, dissolved oxygen concentration <20 mg/l) allows to maximize the use of light by the cells. The developed model is a powerful tool for the optimal design and management of microalgae-based processes, especially outdoors, where the cultures are subject to daily culture condition variations.     

Recruitment and mortality of the temperate coral Cladocora caespitosa: implications for the recovery of endangered populations

Long-lived species are characterized by low recruitment and mortality. In these species, longevity buffers low recruitment, but when catastrophic disturbances alter mortality, recruitment becomes critical for population recovery. In this study, we assessed basic biological traits—recruitment, post-settlement growth, and the mortality of juvenile corals—and related these factors to the adult mortality of one of the most important populations of the Mediterranean reef-building coral Cladocora caespitosa over a period of 6 yr. Adult mortality and recruitment rates were low (~1 % and 0.30 recruits m^?2 yr^?1, respectively), whereas the juvenile colony mortality was comparatively high (29 % in the smallest size-class, <5 polyps). The low recruitment rates will hardly balance the recurrent climate-related mortality that has affected this population. Conservation plans and inclusion in the protection lists are urgently needed, given the escalating threats and slow dynamics of this species.     

Bathymetric adaptations of reef-building corals at davies reef,great barrier reef,Australia. II. Light saturation curves for photosynthesis and respiration

Light saturation (P-I) curves for oxygen production and consumption were constructed in the laboratory for corals collected from depths of 1 to 45 m on the southeastern (seaward) side of Davies Reef, Great Barrier Reef, Australia. This depth range represents a gradient of from 82.6 to 2.9% of surface light, which was measured as photosynthetic photon flux density (PPFD) between 400 and 700 nm. Adaptative changes in photokinetic parameters were observed over the entire range of light intensities. The compensation intensity (I_c), I_k, the intensity at which photosynthesis was 95% light saturated (I_0.95), and the respiration rate (?R), all decreased with decreasing light intensity. The maximal rate of photosynthesis when normalized on the basis of coral chlorophyll-a content (P_ma^g) tended to decrease with decreasing irradiance but the change was not statistically significant. The $\text{P}\text{R}$ ratio ($\text{P}{}_{\mathrm{m}}{}^{\mathrm{g}}\text{?R}$), the initial slope of a light saturation curve (α), and the maximum rate of photosynthesis when normalized by coral protein content (P_mp^g), all increased with decreasing light intensity. The logarithms of the values for each variable parameter were proportional to the logarithms of the fraction of the surface PPFD (T) transmitted to the depth at which the corals grew. This enabled changes in these parameters to be accurately estimated for corals growing at any depth on the reef. Comparison of experimental data with published values for “saturating” irradiance and P_ma^g, suggests that the endosymbiotic algae within reef-building corals are photosynthetically intermediate between classical “sun” and “shade” plants.     

Determination of betaine metabolites and dimethylsulfoniopropionate in coral tissues using liquid chromatography–time-of-flight mass spectrometry and stable isotope-labeled internal standards

A convenient procedure for determination of seven betaine analogs and dimethylsulfoniopropionate (DMSP) in extracts of coral tissues using LC–MS stable isotope dilution is described. Extraction procedures were optimized for selective extraction of polar metabolites from coral tissues. The LC–MS protocol employed a pentafluorophenylpropyl (PFPP) column for HPLC separation, with chromatographic resolution of isobaric and isomeric zwitterionic metabolites optimized by adjusting the acidity of the mobile phase. A ternary gradient was used to exploit the unusual retention characteristics of cationic metabolites on the PFPP column, with incorporation of ammonium acetate in a later gradient stage promoting elution of more hydrophobic betaines which are retained at high organic content in the absence of ammonium acetate. We demonstrate that the new LC–MS based method provides accurate measurements from nanomolar to high micromolar concentrations, and can be applied for profiling of betaine metabolites and DMSP in corals or other aquatic organisms.     

Higher de novo synthesized fatty acids and lower ω3- and ω6-long-chain polyunsaturated fatty acids in umbilical vessels of women with preeclampsia and high fish intakes

Umbilical veins (UV) and arteries (UA) of preeclamptic women in Curaçao harbor lower long-chain polyunsaturated fatty acids (LCP). The present aim was to test these findings in Mwanza (Tanzania), whose inhabitants have high LCPω3 and LCPω6 intakes from Lake Victoria fish. Women with preeclampsia (n=28) in Mwanza had lower PUFA and higher 20:0 in UV and UA, compared with normotensive/non-proteinuric controls (n=31). Their UV 22:6ω3, 22:4ω6, LCPω6, ω6, and LCPω3+ω6 were lower, while saturated FA, potentially de novo synthesized FA (Σde novo) and (Σde novo)/(LCPω3+ω6) ratio were higher. Their UA had higher 16:1ω7, ω7, 18:0, and 16:1ω7/16:0. Umbilical vessels in Mwanza had higher 22:6ω3, LCPω3, ω3, and 16:0, and lower 22:5ω6, 20:2ω6, 18:1ω9, and ω9, compared to those in Curaçao. Preeclampsia in both Mwanza and Curaçao is characterized by lower LCP and higher Σde novo. An explanation of this might be placental dysfunction, while the similarity of umbilical vessel FA-abnormalities in preeclamptic and diabetic pregnancies suggests insulin resistance as a common denominator.     

Preliminary evidence for tissue retraction as a factor in photoprotection of corals incapable of xanthophyll cycling

In a 6-h experiment where xanthophyll inter-conversion was blocked by the inhibitor dithiothreitol (DTT), corals in full sunlight showed a significant increase in oxidative damage and cnidarian antioxidant enzyme concentrations compared with controls. By comparison, antioxidant enzyme concentrations did not increase within the symbiotic algae. In addition, the normal reduction in steady state chlorophyll fluorescence (F_t) and maximum fluorescence (F_m′), in response to increased irradiance, was initially suppressed in the DTT-treated corals, but after 6 h, both parameters had reduced to levels similar to controls with a functional xanthophyll cycle. Extreme host retraction was observed in corals treated with DDT in full sunlight compared with untreated corals in full sunlight and DTT-treated corals in dim irradiance. These results suggest that the coral host is capable of using behavioural (tissue retraction) and biochemical defences (antioxidant enzymes) to protect the symbiotic algae under high natural irradiance when the xanthophyll cycle is absent. While these defences could not prevent oxidative damage, nonetheless, algal numbers and algal chlorophyll levels were not affected.     

Carbon translocation from symbiont to host depends on irradiance and food availability in the tropical coral Stylophora pistillata

Reef-building corals live in symbiosis with dinoflagellates that translocate a large proportion of their photosynthetically fixed carbon compounds to their coral host for its own metabolism. The carbon budget and translocation rate, however, vary depending on environmental conditions, coral host species, and symbiont clade. To quantify variability in carbon translocation in response to environmental conditions, this study assessed the effect of two different irradiance levels (120 and 250 μmol photons m^?2 s^?1) and feeding regimes (fed with Artemia salina nauplii and unfed) on the carbon budget of the tropical coral Stylophora pistillata. For this purpose, H¹³CO₃ ^?-enriched seawater was used to trace the conversion of photosynthetic carbon into symbiont and coral biomass and excrete particulate organic carbon. Results showed that carbon translocation (ca. 78 %) and utilization were similar under both irradiance levels for unfed colonies. In contrast, carbon utilization by fed colonies was dependent on the growth irradiance. Under low irradiance, heterotrophy was accompanied by lower carbon translocation (71 %), higher host and symbiont biomass, and higher calcification rates. Under high irradiance, heterotrophy was accompanied by higher rates of photosynthesis, respiration, and carbon translocation (90 %) as well as higher host biomass. Hence, levels of resource sharing within coral–dinoflagellate symbioses depend critically on environmental conditions.     

Tormopsolus orientalis Yamaguti, 1934 (Digenea: Acanthocolpidae) from Seriola dumerili (Risso) (Perciformes: Carangidae) in the western Mediterranean Sea

Tormopsolus orientalis Yamaguti, 1934, is redescribed from Seriola dumerili from off Corsica, Majorca and Águilas, SE Spain. The vitellarium is interrupted at the level of the ovary and both testes, and a bipartite seminal vesicle is found in many specimens. Oral sucker papillae are always seen. Type-specimens and voucher specimens from off Japan, Bermuda, Panama, Curaçao and the Great Barrier Reef have been compared with the Mediterranean species. Specimens of T. medius Reimer, 1983, from Mozambique have been studied and this species is synonymised with T. orientalis.     

The stable level of coral primary production in a wide light range

Light adaptation and photosynthetic productivity were studied in common reef-building corals on islands of the Indian Ocean and the South China Sea. When light is attenuated, both in shade and at depth, adaptations by zooxanthellae permit maximal absorption and utilization of light. Better utilization of incident light in shade-dwelling and deep-water coral forms is reflected by higher values of gross photosynthesis on the plateau and linear portion of the photosynthesis-irradiance curve. It was shown that outer branches of reef-building corals are autotrophic in a major part of their light-range distribution and have a high and stable level of primary production.     

Long-term dynamics of the brown macroalga <Emphasis Type="Italic">Lobophora variegata</Emphasis> on deep reefs in Curaçao

Lobophora variegata occurs in the eulittoral zone and in deep water on coral reefs in Curaçao. An analysis of the long-term (1979–2006) changes in the vertical distribution of the macroalga in permanent quadrats indicated a significant increase in cover of the deepwater community. In 1998, Lobophora covered 1 and 5% of the quadrats at 20 and 30 m, respectively. By 2006, these values had risen to 25 and 18%, precipitating a shift in abundance of corals and macroalgae at both depths. This increase coincided with losses in coral cover, possibly linked to bleaching, disease and storm-related mortality in deep water plating Agaricia corals. In contrast, macroalgae remained relatively rare (<6% cover) on shallower (10 m) and deeper (40 m) reefs despite declines in coral cover also occurring at these depths, illustrating the depth-dependent dynamics of coral reefs. Several hypotheses are suggested to explain these changes.     

Betaine distribution in Angiosperms

Over 140 Angiosperm species, included in 45 of the 62 orders listed by Engler, have been investigated for the presence of betaines, which were detected in 86% of the species examined and in 43 of the orders. Moreover, betaines were reported earlier in a further seven of the orders. Thus, it can be concluded that betaines are very widely distributed in Angiosperms. The most commonly detected betaines in the study were glycinebetaine and trigonelline, although others, such as prolinebetaine, trans-4-hydroxyprolinebetaine and pipecolatebetaine were found, although with a very restricted distribution. In the large majority of species tested, betaine levels were low (below 0.1%, dry weight).     

Improved methods of analysis for betaines in <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> and its commercial seaweed extracts

Beneficial effects of seaweeds and their extracts on crop performance have been attributed to a variety of compounds, including the betaines which are quaternary ammonium betaines. Methods of analysis of betaines published thus far suffer from low sensitivity, lack of baseline separation of individual betaines and from interference from other sample constituents. A rapid cleanup protocol and a sensitive LC-MS/MS method of analysis were developed to afford baseline separation of four betaines in the brown alga Ascophyllum nodosum and its commercial seaweed extract. Using this method, the presence of glycine betaine, δ-aminovaleric acid betaine, γ-aminobutyric acid betaine and laminine in A. nodosum, and commercial extracts derived from A. nodosum, were confirmed and quantified. The major betaine present was γ-aminobutyric acid betaine accounting for 0.008–0.014% of the dry weight of the seaweed and 0.014–0.027% of the dry weight of the commercial extracts. Seasonal variation in betaine content was observed. Differences in the total betaine content were observed between A. nodosum of the yellow (0.011–0.017% dry weight) and the olive green (0.017–0.021% dry weight) coloured morphologies.     

Effects of delayed settlement on post-settlement growth and survival of scleractinian coral larvae

Demographic connectivity requires both the dispersal of individuals between sub-populations, and their subsequent contribution to population dynamics. For planktonic, non-feeding marine larvae, the capacity to delay settlement enables greater dispersal distances, but the energetic cost of delayed settlement has been shown to adversely impact post-settlement fitness in several taxa. Here, we assess whether delayed settlement influences mortality rates or growth rates for the first 6 weeks following settlement of the scleractinian coral, Acropora tenuis. Coral larvae that were settled at 2, 4, and 6 weeks after spawning, and then deployed in the field, showed negligible effects of delayed settlement on post-settlement survival and time to initial budding for colony formation. Between-cohort differences in budding rate appeared to be explained by temporal variation in the post-settlement acquisition of zooxanthellae. The potential for coral larvae to remain in the pelagic zone for increased periods of time with little to no effect on post-settlement survival and growth suggests that the capacity for delayed settlement is likely to have meaningful demographic consequences for broadcast-spawning reef-building corals, and that the predicted trade-off between delayed settlement and post-settlement fitness is less applicable to reef-building scleractinian corals than other taxa with non-feeding larvae.