Water ice deuteration: a tracer of the chemical history of protostars

Context. Millimetric observations have measured high degrees of molecular deuteration in several species seen around low-mass protostars. The Herschel Space Telescope, launched in 2009, is now providing new measures of the deuterium fractionation of water, the main constituent of interstellar ices. Aims. We aim at theoretically studying the formation and the deuteration of water, which is believed to be formed on interstellar grain surfaces in molecular clouds. Methods. We used our gas-grain astrochemical model GRAINOBLE, which considers the multilayer formation of interstellar ices. We varied several input parameters to study their impact on water deuteration. We included the treatment of ortho- and para-states of key species, including H2, which affects the deuterium fractionation of all molecules. The model also includes relevant laboratory and theoretical works on the water formation and deuteration on grain surfaces. In particular, we computed the transmission probabilities of surface reactions using the Eckart model, and we considered ice photodissociation following molecular dynamics simulations. Results. The use of a multilayer approach allowed us to study the influence of various parameters on the abundance and the deuteration of water. Deuteration of water is found to be very sensitive to the ortho-to-para ratio of H2 and to the total density, but it also depends on the gas/grain temperatures and the visual extinction of the cloud. Since the deuteration is very sensitive to the physical conditions, the comparison with sub-millimetric observation towards the low-mass protostar IRAS 16293 allows us to suggest that water ice is formed together with CO2 in molecular clouds with limited density, whilst formaldehyde and methanol are mainly formed in a later phase, where the condensation becomes denser and colder.Comment: Accepted for publication to A&A. 24 pages, 10 figure

A functional approach to the structural complexity of coral assemblages based on colony morphological features

Colony morphological features is among the best predictor of the scleractinian coral's function in reef ecosystems. However, morphological traits are categorical and to convert this information into a quantitative value as well as estimate their influence on ecosystem process remain a challenge. Here, we propose a trait-based approach to quantify morphological diversity and assess the structural complexity of the habitat provided by corals. We used a previously published dataset that is related to a bleaching event that affected the coral reef off Tikus Island in Indonesia in 1983. We found clear signs of recovery of the coral assemblage's complexity toward pre El Niño conditions five years after the event. Independent of the change observed in species richness, this return in structural complexity was accompanied by a global decrease in species number associated with each particular morphological entity (Functional Redundancy) and an increase in the number of single-species entities (Functional Vulnerability). Together with species loss, we show an overall functional erosion of the coral assemblage and suggest that the role of the coral reef habitat could be strongly imperiled under repeated or synergistic disturbances. This approach offers an opportunity for a better understanding of coral responses to natural and anthropogenic disturbances

Temporal and Spatial Variations in spatial variations in symbiont communities of catch bowl coral Isopora palifera (Scleractinia: Acroporidae) on reefs in Kenting National Park, Taiwan

Acclimatization through Symbiodinium shuffling is one of potential mechanisms in reef-building corals to survive environmental stress. In our previous study, the catch bowl coral Isopora palifera in Tantzei Bay (TZB), Nanwan, Kenting National Park (KNP), southern Taiwan was demonstrated to shuffle thermal-tolerant Symbiodinium D1a and thermal-sensitive Symbiodinium C3 in response to seasonal variations in sea surface temperatures (SSTs) in 2000 and 2001. In this study, we reexamined the temporal dynamics of the Symbiodinium community of I. palifera in TZB in 2006-2009. In addition, spatial variations in Symbiodinium communities in I. palifera were also examined at 6 other sites of Nanwan, KNP in 2009, including a site located at a nuclear power plant outlet (NPP-OL) in southern Taiwan with a yearly mean SST 0.6-1.5 degrees C higher compared to the other sites. Phylotyping and DNA sequence analyses of Symbiodinium ribosomal 28S and ITS2 markers showed that I. palifera colonies at TZB continued to show seasonal shuffling, but shifted to thermal-sensitive type C3 dominant in 2006-2009. This differed from the symbiont community originally dominated by the thermal-tolerant Symbiodinium D1a in 2000 and 2001 after the 1998 mass-bleaching event. Significant differences in spatial variations of the symbiont community in Nanwan were detected with I. palifera colonies at the NPP-OL dominated by Symbiodinium D1a. Our study results suggest that I. palifera can acclimatize to SST anomalies by shuffling to thermal-tolerant Symbiodinium D1a and can revert to thermal-sensitive C3 when the stress disappears, but will maintain the thermally tolerant Symbiodinium D1a as the dominant symbiont if the heat stress continues

Trophic plasticity of scleractinian corals under contrasted environmental conditions: evidence from stable isotope analysis

Most scleractinian corals can derive nutrition either autotrophically or heterotrophically, which allows them to use diverse trophic pathways. Therefore, when facing environmental changes, these organisms are expected to demonstrate an intrinsic ability to acclimatise through trophic plasticity. Despite the ecological importance of these corals, our understanding of their trophic plasticity is currently impaired by a lack of rigorous research approaches; a failure to consider the intraspecific variability of coral species and an oversimplification of the proxies of heterotrophic habits (e.g. corallite diameter). In order to understand how trophic plasticity could allow them to acclimatise, this study proposed to assess the trophic plasticity of morphologically contrasted coral species (e.g. Stylophora pistillata, Porites sp, Isopora palifera). We determined the stable isotope ratios of carbon and nitrogen in the coral host tissues and algal symbionts and compared these in corals inhabiting areas around Taiwan characterised by contrasted temperature (from high to low latitudes) and light levels (from shallow to mesophotic waters). For each area, we evaluated the intraspecific trophic variability by estimating and comparing coral isotopic niches as a proxy for trophic niches. Our results on Stylophora pistillata revealed no overlap of the isotopic niches for the host and symbiont from different locations, suggesting that these coral colonies are supported by different core resources. Moreover, the isotopic niche of higher latitude coral colonies was larger than those from the lower latitudes, highlighting a certain trophic plasticity that may be related to more variable environmental conditions in the higher latitudes. Analyses of additional species and locations will provide essential insights into the trophic plasticity of scleractinian corals and how these species might adjust their nutrition in response to environmental changes

Evolution and biogeography of the <i>Zanclea</i>-Scleractinia symbiosis

Scleractinian corals provide habitats for a broad variety of cryptofauna, which in turn may contribute to the overall functioning of coral symbiomes. Among these invertebrates, hydrozoans belonging to the genus Zanclea represent an increasingly known and ecologically important group of coral symbionts. In this study, we analysed 321 Zanclea colonies associated with 31 coral genera collected from 11 localities across the Indo-Pacific and Caribbean regions, and used a multi-disciplinary approach to shed light on the evolution and biogeography of the group. Overall, we found high genetic diversity of hydrozoans that spans nine clades corresponding to cryptic or pseudo-cryptic species. All but two clades are associated with one or two coral genera belonging to the Complex clade, whereas the remaining ones are generalists associated with both Complex and Robust corals. Despite the observed specificity patterns, no congruence between Zanclea and coral phylogenies was observed, suggesting a lack of coevolutionary events. Most Zanclea clades have a wide distribution across the Indo-Pacific, including a generalist group extending also into the Caribbean, while two host-specific clades are possibly found exclusively in the Red Sea, confirming the importance of this peripheral region as an endemicity hotspot. Ancestral state reconstruction suggests that the most recent common ancestor of all extant coral-associated Zanclea was a specialist species with a perisarc, occurring in what is now known as the Indo-Pacific. Ultimately, a mixture of geography- and host-related diversification processes is likely responsible for the observed enigmatic phylogenetic structure of coral-associated Zanclea

Spectral Diversity and Regulation of Coral Fluorescence in a Mesophotic Reef Habitat in the Red Sea

The phenomenon of coral fluorescence in mesophotic reefs, although well described for shallow waters, remains largely unstudied. We found that representatives of many scleractinian species are brightly fluorescent at depths of 50–60 m at the Interuniversity Institute for Marine Sciences (IUI) reef in Eilat, Israel. Some of these fluorescent species have distribution maxima at mesophotic depths (40–100 m). Several individuals from these depths displayed yellow or orange-red fluorescence, the latter being essentially absent in corals from the shallowest parts of this reef. We demonstrate experimentally that in some cases the production of fluorescent pigments is independent of the exposure to light; while in others, the fluorescence signature is altered or lost when the animals are kept in darkness. Furthermore, we show that green-to-red photoconversion of fluorescent pigments mediated by short-wavelength light can occur also at depths where ultraviolet wavelengths are absent from the underwater light field. Intraspecific colour polymorphisms regarding the colour of the tissue fluorescence, common among shallow water corals, were also observed for mesophotic species. Our results suggest that fluorescent pigments in mesophotic reefs fulfil a distinct biological function and offer promising application potential for coral-reef monitoring and biomedical imaging

Capacités et modalités d’adaptation de deux espèces de coraux zooxanthellés aux perturbations climatiques et anthropiques (île de la Réunion, Sud-Ouest de l’océan Indien)

Reef coral communities will undergo major changes in the next decades. The potentials of acclimatization and adaptation to environmental changes are compared between two zooxanthellate scleractinian corals dominant on Reunion coral reefs: the K-strategist Porites lutea and the r-strategist Acropora muricata. Different traits of the holobionts (survival, growth, regeneration, tissue biomass, protein content, lipid composition) and their zooxanthellae (genetic identity, photosynthetic parameters) are characterized in situ in two to four shallow reef flat sites, less than 11 km apart. Their environmental conditions offer a wide range of temperature, light, hydrodynamism and nutrient levels. P. lutea which is associated to the thermotolerant zooxanthellae Symbiodinium C15 has a high potential for acclimatization. After transplantation to a new environment, P. lutea quickly adjusts its growth and protein content, without suffering any mortality. In contrast, A. muricata, which is combined with the thermosensitive zooxanthellae C2/C3, does not display such a capacity for acclimatization and showed a high mortality. All the characteristics (except tissue biomass) of A. muricata and photosynthetic parameters, as well as tissue biomass of P. lutea, are marked by an "imprint" of the original site. This limited phenotypic plasticity suggests a genetic differentiation at small-scale. In A. muricata, it results in an increased tolerance to high temperatures in the most fluctuating environment. A. muricata also shows greater regenerative capacities than P. lutea. In the latter species, regeneration is correlated to solar radiation and temperature, through their control of the photosynthetic performance of symbiotic zooxanthellae. A seasonal change in autotrophy vs heterotrophy is detected in A. muricata at the site where exposition to oceanic environment is the highest. The phenotypic plasticity of P. lutea, a long-lived species, allows it to acclimatize to changing environmental conditions. Recovery capacities of A. muricata, in relation to its adaptive capacity to local conditions, would also allow this opportunistic species to live through the environmental changes that are expected in the context of global change, but within limits yet to be defined for these two scleractinian species.Les communautés coralliennes récifales vont subir de profonds changements dans les prochaines décennies. Les potentiels d‟acclimatation et d‟adaptation à des changements environnementaux sont comparés entre deux espèces de coraux Scléractiniaires zooxanthellés dominantes des récifs coralliens réunionnais : le stratège K Porites lutea et le stratège r Acropora muricata. Différents traits des holobiontes (survie, croissance, régénération, biomasse des tissus, contenu en protéines, composition lipidique) et de leurs zooxanthelles (identité génétique, paramètres photosynthétiques) sont caractérisés in situ sur deux à quatre sites des platiers récifaux peu profonds, distants au plus de 11 km. Leurs conditions environnementales offrent une large gamme de variation de température, d‟éclairement, d‟hydrodynamisme et de teneurs en éléments nutritifs. P. lutea, associée à des zooxanthelles thermotolérantes Symbiodinium C15, présente un fort potentiel d‟acclimatation. Après transplantation dans un environnement nouveau, P. lutea ajuste rapidement sa croissance et son contenu en protéines, sans présenter de mortalité. En revanche, A. muricata, associée à des zooxanthelles thermosensibles C2/C3, ne présente pas de telles capacités d‟acclimatation et montre une mortalité élevée. Toutes les caractéristiques d‟A. muricata (excepté sa biomasse de tissus) ainsi que les paramètres photosynthétiques et la biomasse de tissus de P. lutea sont marqués par une « empreinte » du site originel. Cette plasticité phénotypique limitée suggère une différenciation génétique à petite échelle. Chez A. muricata, elle se traduit par une tolérance accrue aux fortes températures dans l‟environnement le plus variable. A. muricata montre également des capacités régénératrices supérieures à celles de P. lutea. Chez cette dernière, la régénération est corrélée à l‟éclairement et la température, via leur contrôle des performances photosynthétiques des zooxanthelles symbiotiques. Une alternance saisonnière autotrophie/hétérotrophie est décelée chez A. muricata dans le site le plus exposé au milieu océanique. La plasticité phénotypique de P. lutea, espèce longévive, lui permet de s‟acclimater à des conditions environnementales changeantes. Les capacités de rétablissement d‟A. muricata couplées à une capacité d‟adaptation locale permettraient aussi à cette espèce opportuniste de survivre aux modifications du milieu attendues dans le cadre du changement global, dans des limites restant à définir pour ces deux Scléractiniaires

Acclimatization and adaptation capacities of two zooxanthellate corals to anthropogenic and climatic disturbances

Les communautés coralliennes récifales vont subir de profonds changements dans les prochaines décennies. Les potentiels d‟acclimatation et d‟adaptation à des changements environnementaux sont comparés entre deux espèces de coraux Scléractiniaires zooxanthellés dominantes des récifs coralliens réunionnais : le stratège K Porites lutea et le stratège r Acropora muricata. Différents traits des holobiontes (survie, croissance, régénération, biomasse des tissus, contenu en protéines, composition lipidique) et de leurs zooxanthelles (identité génétique, paramètres photosynthétiques) sont caractérisés in situ sur deux à quatre sites des platiers récifaux peu profonds, distants au plus de 11 km. Leurs conditions environnementales offrent une large gamme de variation de température, d‟éclairement, d‟hydrodynamisme et de teneurs en éléments nutritifs. P. lutea, associée à des zooxanthelles thermotolérantes Symbiodinium C15, présente un fort potentiel d‟acclimatation. Après transplantation dans un environnement nouveau, P. lutea ajuste rapidement sa croissance et son contenu en protéines, sans présenter de mortalité. En revanche, A. muricata, associée à des zooxanthelles thermosensibles C2/C3, ne présente pas de telles capacités d‟acclimatation et montre une mortalité élevée. Toutes les caractéristiques d‟A. muricata (excepté sa biomasse de tissus) ainsi que les paramètres photosynthétiques et la biomasse de tissus de P. lutea sont marqués par une « empreinte » du site originel. Cette plasticité phénotypique limitée suggère une différenciation génétique à petite échelle. Chez A. muricata, elle se traduit par une tolérance accrue aux fortes températures dans l‟environnement le plus variable. A. muricata montre également des capacités régénératrices supérieures à celles de P. lutea. Chez cette dernière, la régénération est corrélée à l‟éclairement et la température, via leur contrôle des performances photosynthétiques des zooxanthelles symbiotiques. Une alternance saisonnière autotrophie/hétérotrophie est décelée chez A. muricata dans le site le plus exposé au milieu océanique. La plasticité phénotypique de P. lutea, espèce longévive, lui permet de s‟acclimater à des conditions environnementales changeantes. Les capacités de rétablissement d‟A. muricata couplées à une capacité d‟adaptation locale permettraient aussi à cette espèce opportuniste de survivre aux modifications du milieu attendues dans le cadre du changement global, dans des limites restant à définir pour ces deux Scléractiniaires.Reef coral communities will undergo major changes in the next decades. The potentials of acclimatization and adaptation to environmental changes are compared between two zooxanthellate scleractinian corals dominant on Reunion coral reefs: the K-strategist Porites lutea and the r-strategist Acropora muricata. Different traits of the holobionts (survival, growth, regeneration, tissue biomass, protein content, lipid composition) and their zooxanthellae (genetic identity, photosynthetic parameters) are characterized in situ in two to four shallow reef flat sites, less than 11 km apart. Their environmental conditions offer a wide range of temperature, light, hydrodynamism and nutrient levels. P. lutea which is associated to the thermotolerant zooxanthellae Symbiodinium C15 has a high potential for acclimatization. After transplantation to a new environment, P. lutea quickly adjusts its growth and protein content, without suffering any mortality. In contrast, A. muricata, which is combined with the thermosensitive zooxanthellae C2/C3, does not display such a capacity for acclimatization and showed a high mortality. All the characteristics (except tissue biomass) of A. muricata and photosynthetic parameters, as well as tissue biomass of P. lutea, are marked by an "imprint" of the original site. This limited phenotypic plasticity suggests a genetic differentiation at small-scale. In A. muricata, it results in an increased tolerance to high temperatures in the most fluctuating environment. A. muricata also shows greater regenerative capacities than P. lutea. In the latter species, regeneration is correlated to solar radiation and temperature, through their control of the photosynthetic performance of symbiotic zooxanthellae. A seasonal change in autotrophy vs heterotrophy is detected in A. muricata at the site where exposition to oceanic environment is the highest. The phenotypic plasticity of P. lutea, a long-lived species, allows it to acclimatize to changing environmental conditions. Recovery capacities of A. muricata, in relation to its adaptive capacity to local conditions, would also allow this opportunistic species to live through the environmental changes that are expected in the context of global change, but within limits yet to be defined for these two scleractinian species

Extension of the known distribution and depth range of the scleractinian coral Psammocora stellata: first record from a Taiwanese mesophotic reef

[[sponsorship]]生物多樣性研究中心[[note]]已出版;有審查制度;具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=1867-1616&DestApp=JCR&RQ=IF_CAT_BOXPLO

Association Between The Scallop, Pedum Spondyloideum, (Bivalvia: Pteriomorphia: Pectinidae) And Scleractinian Corals From The Wakatobi Marine National Park (Southeastern Sulawesi, Indonesia)

Scaps, Patrick, Denis, Vianney (2007): Association Between The Scallop, Pedum Spondyloideum, (Bivalvia: Pteriomorphia: Pectinidae) And Scleractinian Corals From The Wakatobi Marine National Park (Southeastern Sulawesi, Indonesia). Raffles Bulletin of Zoology 55 (2): 371-380, DOI: 10.5281/zenodo.533400