Lipids and nitrogen isotopes of deep-water corals

The lipid and organic nitrogen isotopic (delta15N) compositions of two common deep-water corals (Lophelia pertusa and Madrepora oculata) collected from selected locations of the NE Atlantic are compared to the composition of suspended particulate organic matter, in order to determine their principle food source. Initial results suggest that they may feed primarily on zooplankton. This is based on the increased abundances of mono-unsaturated fatty acids and alcohols and the different ratios of the polyunsaturated fatty acids, 22:6/20:5 of the corals when compared to those of the suspended particulate organic matter. There is enrichment in L. pertusa of mono-unsaturated fatty acids and of delta15N relative to M. oculata. It is unclear whether this reflects different feeding strategies or assimilation/storage efficiencies of zooplankton tissue or different metabolism in the two coral species.

Boron isotopes, pH and pCO2 calculation for one Fiji coral specimen Porites (1898-1998), 2012

delta11B results and deduced pH, pCO2 and omega values obtained for a tropical coral specimen Porites collected in 1998 at Yasawa (16°48'S- 177°27'E) on the western side of the Fiji archipelago, location in the north western part of the Pacific Warm Pool. Such Porites specimen grew during the XXth century (1898-1998). Boron isotopes results allowed the reconstruction of surface ocean acidification in the vincinity of Fiji Islands with strong interdecadal influence of the ENSO at regional scale. pHT calculation parameters (Hönisch et al., 2007): a=0 PER MIL; alpha=0.9804; delta11B=39.5 PER MIL; salinity=35.02; pKB from Dickson (1990). pCO2 and omega calculation parameters: TA= 2350 µM; Ca= 10.2 mM; Dickson et al.(2007); Mucci 1983.

(Table 2) Chemical composition of skeletons of scleractinian non-zooxanthelate corals

The first data on chemical composition of nonreef-building non-zooxanthellate deep-sea corals presented in this publication allow us to identify following tendencies manifested in the biomineralization process. Comparison of concentration levels of some chemical elements in scleractinian corals and ambient ocean waters suggests that corals do not accumulate K in the process of biomineralization and weakly accumulate Mg, whereas Ca, Sr, Si, Al, Ti, Mn, Zn, Cu, Cd, Pb, and Fe are concentrated in skeletons of corals with enrichment coefficients of 10**3 to 10**7. Correlations between components contained in the skeletons of scleractinian corals suggest that the source of Al, Si, Fe, and Ti in them is the clayey constituent of bottom sediments and zooplankton, while trace elements are likely accumulated via bioassimilation from seawater. Such elements as Mn, Sr, Pb, and Cd can structurally substitute Ca in calcite and aragonite. Variations in concentrations of the elements in coral skeletons depending on their habitat depths are fairly significant. As could be expected Ca and Mg concentrations are prone to decrease with depth (R = -0.55 and -0.51, respectively), which can possibly be caused by partial dissolution of carbonate skeletons with increasing depth, whereas the Sr/Ca ratio does not depend on depth.

Age determination and geochemistry of corals from the North Pacific

A depth transect of deep-sea bamboo corals along the California margin provides evidence that coral strontium to calcium ratios (Sr/Ca[coral]) record seawater Sr/Ca ratios (Sr/Ca[sw]). A calibration was constructed utilizing Sr/Ca[coral] ratios and previously published Pacific Sr/Ca[sw] data (R**2 = 0.53, n = 12, p < 0.01): Sr/Ca[coral] (mmol/mol) = 4.62*Sr/Ca[sw] (mmol/mol) - 36.64. Sr/Ca[sw] is ultimately governed by the remineralization of Sr-containing shells of surface water-derived marine organisms (e.g., Acantharia) at intermediate water depths. California margin Sr/Cacoral records from 792 and 1295 m document fluctuations in Sr/Ca[sw] that appear decadal-scale. These results suggest that Sr/Casw may not be as stable as previously assumed and may be influenced by surface productivity on short timescales.