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FIGURE 3 in Phylogenetic relationships in the genus Astropecten Gray (Paxillosida: Astropectinidae) on a global scale: molecular evidence for morphological convergence, species-complexes and possible cryptic speciation
No full textFIGURE 3. Total evidence molecular phylogeny of 117 specimens of Astropecten and seven outgroup taxa based on combined 12S, 16S and COI sequences of the mitochondrial DNA. (a) Maximum parsimony strict consensus tree of 2600 most parsimonious trees (length = 3447). Above nodes: bootstrap support values above 50% from 1,000 replicates. Below nodes: decay indices. (b) Bayesian inference tree resulting from 9,500 trees based on the GTR+I+Γ model. Posterior probabilities are indicated above nodes. See Table 1 for collection locality of specimens. EP = East Pacific, WA = West Atlantic; CP = Central Pacific; WP = West Pacific; IP = Indo-Pacific; IO = Indian Ocean; EA = East Atlantic, EM = East Mediterranean, WM = West MediterraneanPublished as part of Zulliger, Deborah E. & Lessios, H.A., 2010, Phylogenetic relationships in the genus Astropecten Gray (Paxillosida: Astropectinidae) on a global scale: molecular evidence for morphological convergence, species-complexes and possible cryptic speciation, pp. 1-19 in Zootaxa 2504 (1) on page 12, DOI: 10.11646/zootaxa.2504.1.1, http://zenodo.org/record/530272
Spatial variation in coral recruitment around Lizard Island, Australia
No full textSpatial variation in recruitment is characteristic of marine organisms with planktonic larvae and is generally apparent at all spatial scales. In this study spatial variation in the abundance and taxonomic composition of coral recruits was examined, using settlement panels, at a number of scales between depth zones on the fringing reef surrounding Lizard Island. Within the reef crest, variations in abundance between sites were small compared to within site variation. In all taxa the scale of patchiness in recruitment was finer than the site. However, the pattern was strikingly different for recruits from the families Acroporidae and Pocilloporidae, which suggests that different processes operating at different scales are influencing recruitment in these taxa. The abundance of recruits varied significantly between depth zones, with a pronounced reduction in recruitment of all taxa on the reef slope (4m). The abundance of recruits on more exposed surfaces of the settlement panels did not increase with depth. Depth zonation of the recruit assemblage suggests that coral larvae have either the ability to regulate their position within the water column or recognise depth specific substratum characteristics. In contrast, the taxonomic composition of the recruits did not vary between sites within the reef crest despite marked differences in the adult assemblages. These patterns suggest that patterns established at the time of settlement contribute to the depth zonation of adult assemblages and that the importance of post-settlement processes varies between zones
Proceedings of the 8th international coral reef symposium
No full textIn atoll lagoons, a large part of the nutrients required for lagoon primary production are supplied by mineralization process and input from oceanic waters. However, major lagoonal primary producers are cyanobacteria, some of which are nitrogen-fixing. Rates of acetylene reduction and 15N2 fixation were measured in Tikehau lagoon between 1991 and 1994. Nitrogenase activity was observed in all cyanobacterial communities : sediments, emerged mats, kopara mats, emerged beach sand, limestone surface, beach rock and the water column. Nitrogen fixation was much more important during the daylight. N fixation for the whole lagoon contributes in averages between 0.2% (without plankton contribution) and 13% (with the calculated plankton N fixation rate) of the nitrogen requirement to support the gross primary production. (Résumé d'auteur
Proceedings of the 8th international coral reef symposium
No full textDOC is widely recognized as one of the largest carbon standing stocks on the earch but still, little is known about DOC utilization by bacterioplankton and its subsequent transfer in pelagic foodwebs. The estimation of carbon growth yield (CGY) is key to the evaluation of the contribution of bacterioplankton in pelagic networks. We examined DOC standing stocks, consumption and turn-over in some Tuamotu atoll lagoons (French Polynesia) and in the Great Astrolabe Reef lagoon (Fiji). DOC was determined by a HTCO method. DOC consumption by bacteria was computed from in situ bacterial production (following DNA synthesis) and bacterial CGY experimentally determined in unenriched batch cultures. Results of these experiments show that average DOC values range between 105 and 121 micrometers in the lagoons visited and were significantly higher than in surrounding surface oceanic waters (87-102 micrometers). The labile fraction is estimated to be 14-26% of total DOC. Bacterial CGY is very low and ranges between 4 and 7%. DOC turnover is estimated to be 11 to 32 days in the lagoons visited. These data suggest that bacteria are resource limited in these lagoons. This is in agreement with the slow growth rates of bacterioplankton in these coral reef lagoons. (Résumé d'auteur
Proceedings of the 8th international coral reef symposium
No full textLight absorbance by water samples of 16 lagoons was measured between 250 and 400 nm. From these readings, we extract absorbance at 254 nm (A254), and spectrum slope, S*. These two descriptors are negatively correlated, so that samples are distributed along a hyperbola, between an "oceanic" (= oligotrophic) pole and a "eutrophic" (or coastal) pole. We determine an "optical oceanic index", OOI as the curvilinear abscissa of each sample along the A254-vs-S* hyperbolic regression curve. OOI exhibits significant correlations with several water characteristics (particulate organic matter, total dissolved nutrients). It also correlates well with an estimator of potential flushing rate base on reef morphometry and swell energy distribution. OOI thus appears adequate as a highly sensitive, and at least semi-quantitative, estimator of the oceanic/coastal gradient. Absorbance can be used as a rapid, sensitive, and relatively cheap method for studying DOC distribution, qualitative and quantitative, in coral-reef lagoons. An improvement of the data base is planned, and necessary to confirm the present results. (Résumé d'auteur
Proceedings of the 8th international coral reef symposium
No full textInterstitial water samples, from a borehole drilled in 1992 to 150 m inside the north barrier reef of Tahiti, have been analysed monthly for : temperature, salinity, dissolved inorganic nutrients (PO4, SiO4, DIN, DIC), O2, pH and alkalinity. Other parameters such as dissolved organics (DON, DOC) were also measured in 1994 in two sets of samples. These data show : significant differences with the adjacent ocean, including a lower density for any given depth, leading to an inevitable upward movement of interstitial water ; decrease of pH, alkalinity, DIN and DIC with depth, from the reef crest down to the carbonate - basalt interface at 116 m ; strong positive gradients of DON and DOC inside the basaltic foundation (116-150 m), which then constitutes a large organic reservoir. These results suggest that the organics coming from the basalt foundation (first end-member) are, during their circulation through the carbonates, transformed into inorganic nutrients, with consumption of dissolved oxygen. A second end-member is the oceanic surface water injected by waves forcing through the top part of the reef : the mixing of the interstitial water with this nutrients-depleted, oxygen-saturated water tends to prevent anoxia and to lower nutrients concentration. The specific properties found in the basalt interstitial waters - low alkalinity, high silicate and high DON-DOC content - are convergent with data obtained in other basaltic crusts where thermally driven-hydrothermal circulation is a general rule. (Résumé d'auteur
Proceedings of the 8th international coral reef symposium
No full textThe study of the organic content of insular peloidal phosphorites was undertaken in order to get the same kind of information as those obtained through organic geochemical studies on the origin of marine peloidal phosphorites i.e. information on the sedimentological and diagenetic environments in which phosphorites were formed. The content in total organic carbon (T.O.C.) (from 0.5 to 6%, in 27 samples studied), the high proportion of labile organic carbon (acido-soluble and humics) (> 60% of T.O.C.), Rock-Eval pyrolysis results and the molecular composition of hydrocarbons, fatty acids and amino acids, all suggest an algal (essentially cyanobacterial) origin for the organic matter associated with insular phosphatic peloids. Such a result confirms the abundance of cyanobacteria in the phosphatogenic milieu which had been already suggested by the coating of peloids. Phosphatogenesis took place in closed lagoons where important cyanobacterial biomasses accumulated phosphorus. Such environments are known in recent atolls, for example in Niau atoll (French Polynesia). The source of phosphorus can vary : sea water vary inputs, leaching of biogenic phosphorus from the aerial and sub-aerial parts of the reef, avian guano or endo-upwelling processes transfering deep (ca. 500 m) marine waters from outside the reef into the lagoon through the porous body of the reef. (Résumé d'auteur
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