The influence of increased pCO2 on the calcification of Mytilus edulis

One of the most important and abundant calcifying organisms in several marine ecosystems is the blue mussel, Mytilus edulis. It has a wide geographic distribution (Gosling 1992 Developm. Aquacult. Fish. Sci. 25, 1-20) and tolerates a broad range of environmental conditions (Seed and Suchanek 1992 Developm. Aquacult. Fish. Sci. 25, 87-170). Blue mussel beds are also common features in the Kiel Fjord (Baltic Sea), a habitat dominated by low salinity (10-20 PSU), low alkalinity (1900-2150 μmol kg-1), low pH (minimum values < 7.5) and high pCO2 (maximum value of 2340 ppm). The resulting calcium carbonate saturation state (min. values: Ωarag = 0.34 and Ωcalc = 0.58) is significantly lower than in the open ocean (Thomsen et al. submitted). Therefore, pCO2 in Kiel Fjord during summer is already higher than what is predicted for the future (e.g., Caldeira and Wickett 2003 Nature 425, 365). Additionally, Meier (2006 Clim. Dyn. 27, 39-68) projected an increase of temperature (2.6 to 5.0 °C) in the next 100 years for the Baltic Sea. To contribute to the understanding of the ability of calcifying organisms to live under ocean acidification conditions and of biomineralization mechanisms, M. edulis from this naturally CO2-enriched habitat were cultured in a flow-through system. Experiments were conducted using CO2 concentrations ranging from 380 ppm to 4000 ppm and temperatures ranging from 5° to 25°C. At the end of the experiments, hemolymph and extrapallial fluid (EPF) were taken and analyzed for pH, pCO2, bicarbonate and elemental ratios. Fluids showed decreased pH and increased CO2 with increasing water pCO2. Elemental ratios (Mg/Ca and Sr/Ca) in the fluids did not show pCO2 or temperature-related systematic changes. Furthermore, boron isotopes ([Delta]11B), used in isotope geochemistry as a pH proxy, were investigated by LA-MC-ICP-MS in shell portions precipitated during the experimental treatment. We observed high [Delta]11B variability between different individuals, but also within single shells. Average [Delta]11B values showed a weak positive correlation with pH. When comparing our results to published studies, boron isotopes appeared to represent internal pH conditions (EPF) instead of ambient water pH (Kasemann et al. 2009 Chem. Geol. 260, 138-147; Reynaud et al. 2004 Coral Reefs 23, 539-546; Sanyal et al. 2000 Geochim. Cosmochim. Acta 64, 1551-1555)

Experimental evaluation of elemental behavior during LA-ICP-MS: influences of plasma conditions and limits of plasma robustness

Matrix effects are one of the frequently observed and discussed issues challenging the accuracy of LA-ICP-MS results. The specific role of the ICP as a source of elemental fractionation seems not fully understood. We report the results of an experiment using six internationally available reference materials (five silicates, one carbonate) measured under 11 different plasma conditions. The thermal/energetic state of the plasma was estimated based on the ratio of Ar-38(+) and Ar-40(2)+ ions. We show that element specific behavior (volatile vs. refractory) dominates at cool but vanishes under hot plasma conditions. For robust (hot) plasma conditions matrix-tolerance seems to be achieved. Additionally we address the problem of matrix-load with respect to the plasma conditions. We've estimated practical limits for the amount of matrix which can be introduced into the ICP without significantly changing the plasma condition

Massenspektrometrische Untersuchungen zur Verteilung natürlicher Radionuklide im Arabischen Meer

The distribution of 231Pa, 228Th, 230Th, 232Th and 234Th in the Arabian Sea was studied on water samples, sediment trap matter and surface sediments. Strong variations of the particle flux forced by the monsoon are influencing the vertical and lateral radionuclide fluxes. The strong boundary scavenging effect was studied on the distributions of 231Pa and 230Th. In the central Arabian Sea 40...50 of 231Pa produced in the water column are exported to the coasts. Near the shelf of the Arabian Peninsula up to 150 231Pa more than produced in the overlying water column are deposited in sediments. With radionuclid budget calculations the trapping efficiencies of sediment traps deployed in the Arabian Sea was estimated. For deep traps (3000 m) efficiencies of 90...118 and for a shallow trap (500 m) 50 were calculated. These results corroborate those of other investigations, finding a strong undertrapping for shallow traps. A new method for radionuclid determination using HR-ICP-MS was developed and applied. With this method detection limits and precisions comparable with TIMS were achieved, while the requirements of measurement time and sample preparation were reduced

A simplified procedure for the determination of stable chlorine isotope ratios (δ37Cl) using LA-MC-ICP-MS

Stable chlorine isotopes (37Cl, 35Cl) are considered as important tracers of geochemical processes, especially in subduction zone systems. However, high-quality chlorine isotope data are scarcely available. Here we present a comparatively simple procedure for the precise and accurate determination of stable chlorine isotope ratios (δ37Cl) using LA-MC-ICP-MS. Chlorine was extracted from solid samples by pyrohydrolysis. After quantitative precipitation as AgCl the dried precipitates where analysed in a sample-standard bracketing approach using a weak laser ablation (0.3 J/cm2) for sample evaporation. Atlantic Ocean sea salt and the sea water standard IAPSO were used as SMOC (standard mean ocean chloride) for normalisation (δ37Cl = 0 ‰). The precision and accuracy of the presented method was validated analysing the reference materials JB-1a and JB-2. The chlorine isotope ratios of these standards were determined as δ37ClJB-1a = (−0.99 ± 0.06) ‰ and δ37ClJB-2 = (−0.60 ± 0.03) ‰ (errors 2SE), respectively, in accordance with published data. Applying the presented method a total amount of less than 1 μg of chlorine was consumed during a typical measurement including 10 ablation periods on the sample

Proposal for International Agreement on Ca Notation resulting from discussion at workshops on stable isotope measurement held in Davos (Goldschmidt 2002) and Nice (EGS-AGU-EUG 2003)

A proposal is made to standardise the reporting of Ca isotope data to the δ44Ca/40Ca notation (or δ44Ca/42Ca) and to adopt NIST SRM 915a as the reference standard

Distinct fine-scale variations in calcification control revealed by high-resolution 2D boron laser images in the cold-water coral Lophelia pertusa

Coral calcification is a complex biologically controlled process of hard skeleton formation, and it is influenced by environmental conditions. The chemical composition of coral skeletons responds to calcification conditions and can be used to gain insights into both the control asserted by the organism and the environment. Boron and its isotopic composition have been of particular interest because of links to carbon chemistry and pH. In this study, we acquired high-resolution boron images (concentration and isotopes) in a skeleton sample of the azooxanthellate cold-water coral Lophelia pertusa. We observed high boron variability at a small spatial scale related to skeletal structure. This implies differences in calcification control during different stages of skeleton formation. Our data point to bicarbonate active transport as a critical pathway during early skeletal growth, and the variable activity rates explain the majority of the observed boron systematic