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  • 1
    Publication Date: 2018-09-27
    Type: Dataset
    Format: text/tab-separated-values, 181 data points
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    PANGAEA
    In:  Supplement to: Ramesh, Kirti; Melzner, Frank; Griffith, Andrew W; Gobler, Christopher J; Rouger, Caroline; Tasdemir, Deniz; Nehrke, Gernot (2018): In vivo characterization of bivalve larval shells: a confocal Raman microscopy study. Journal of The Royal Society Interface, 15(141), 20170723, https://doi.org/10.1098/rsif.2017.0723
    Publication Date: 2019-04-30
    Description: In vivo confocal Raman microscopy (CRM), polarized light microscopy and Fourier transform infrared spectroscopy (FTIR) were used to determine if a significant amount of amorphous calcium carbonate (ACC) exists within larval shells of Baltic mytilid mussels (Mytilus edulis-like) and whether the amount of ACC varies during larval development. No evidence for ACC was found from the onset of shell deposition at 21 h post-fertilization (hpf) until 48 hpf. Larval Mytilus shells were crystalline from 21 hpf onwards and exhibited CRM and FTIR peaks characteristic of aragonite. Prior to shell deposition at 21 hpf, no evidence for carbonates was observed through in vivo CRM. We further analysed the composition of larval shells in three other bivalve species, Mercenaria mercenaria, Crassostrea gigas and Crassostrea virginica and observed no evidence for ACC, which is in contrast to previous work on the same species. Our findings indicate that larval bivalve shells are composed of crystalline aragonite and we demonstrate that conflicting results are related to sub-optimal measurements and misinterpretation of CRM spectra. Our results demonstrate that the common perception that ACC generally occurs as a stable and abundant precursor during larval bivalve calcification needs to be critically reviewed.
    Type: Dataset
    Format: text/tab-separated-values, 143020 data points
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  • 4
    Publication Date: 2014-07-30
    Description: Ikaite (CaCO3·6H2O) has only recently been discovered in sea ice, in a study that also provided first direct evidence of CaCO3 precipitation in sea ice. However, little is as yet known about the impact of physico-chemical processes on ikaite precipitation in sea ice. Our study focused on how the changes in pH, salinity, temperature and phosphate (PO4) concentration affect the precipitation of ikaite. Experiments were set up at pH from 8.5 to 10.0, salinities from 0 to 105 (in both artificial seawater (ASW) and NaCl medium), temperatures from 0 to −4 °C andPO4 concentrations from0 to 50 μmol kg−1. The results show that in ASW, calcium carbonate was precipitated as ikaite under all conditions. In the NaCl medium, the precipitates were ikaite in the presence of PO4 and vaterite in the absence of PO4. The onset time (τ) at which ikaite precipitation started, decreased nonlinearly with increasing pH. In ASW, τ increased with salinity. In the NaCl medium, τ first increased with salinity up to salinity 70 and subsequently decreased with a further increase in salinity; it was longer in ASW than in the NaCl medium under the same salinity. τ did not vary with temperature or PO4 concentration. These results indicate that ikaite is very probably the only phase of calcium carbonate formed in sea ice. PO4 is not, as previously postulated, crucial for ikaite formation in sea ice. The change in pH and salinity is the controlling factor for ikaite precipitation in sea ice. Within the ranges investigated in this study, temperature and PO4 concentration do not have a significant impact on ikaite precipitation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2014-06-13
    Description: Many of the pigments that are widely found in coloured parts of mollusc shells are polyenes, i.e. molecules with a central polyenic chain (carbon-carbon single and double bonds). Due to a resonant coupling of these molecules at wavelengths typically used in Raman spectroscopy, this method is well suited to investigate their occurrence in biogenic materials. Here we use confocal Raman microscopy to map the spatial distribution of polyenes within the shell of the bivalve Arctica islandica and to determine their chemical characteristics (chain length). Polyene chain length does not differ between shells from different localities (off Iceland, Baltic Sea and North Sea). We also show that the pigment polyenes are not only located at the outside of the shell, but also within the shell, developing the same layered pattern typical for growth bands. This finding raises the question as to whether polyenes may play a role in the biomineralization process itself.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2015-08-13
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 7
    Publication Date: 2014-12-03
    Description: In this study we introduce a new in situ technique which allows the determination of the boron isotopic composition and B/Ca ratios simultaneously at the nanogram level using a combination of optical emission spectroscopy and multiple ion counting MC ICP-MS with laser ablation. This technique offers a new application in the paleo-field of oceanography and climatology since small samples like e.g. single foraminiferal shells can be analyzed. The simultaneous determination of the boron isotopic composition and B/Ca ratios provides two independent proxies which allow the reconstruction of the full carbonate system. To test the new technique we performed measurements on the cultured, benthic foraminifer Amphistegina lessonii. Our results yielded an average boron isotopic composition δ11B = 18.0 ± 0.83‰ (SD) with an average internal precision of 0.52‰ (RSE). The boron concentration was 53 ± 7 μg/g (SD). These results agree with the range reported in the literature. The reconstructed mean pH value is in excellent agreement with the measured pH of the seawater in which the foraminifers grew. The analysis of a foraminifer consumed approximately 1200 ng calcium carbonate containing ca. 0.06 ng boron. Compared to bulk analytical methods, this new technique requires less material and reduces the time for sample preparation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 8
    Publication Date: 2015-01-05
    Description: Consistently classified among the references for calcite simple prisms, the microstructural units that form the outer layer of the Pinctada margaritifera have been investigated through a series of morphological, crystallographical and biochemical characterizations. It is often said that the polygonal transverse shape of the prisms result from the competition for space between adjacent crystals. In contrast to this classical scheme the Pinctada prisms appear to be composed of four successive developmental stages from the concentrically growing disks on the internal side of the periostracum to the morphological, structural and compositional changes in both envelopes and mineral components at the end of the prisms. These latest structural and compositional changes predate nacre deposition, so that the end of prism growth is not caused by occurrence of nacre, but by metabolic changes in the secretory epithelium. This sequence makes obvious the permanent biological control exerted by the outer cell layer of the mantle in both organic envelopes and mineralizing organic phases.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 9
    Publication Date: 2015-02-10
    Description: Biological hard parts and skeletons of aquatic organisms often archive information of past environmental conditions. Deciphering such information forms an essential contribution to our understanding of past climate conditions and thus our ability to mitigate the climatic, ecological, and social impacts of a rapidly changing environment. Several established techniques enable the visualization and reliable use of the information stored in anatomical features of such biogenic archives, i.e., its growth patterns. Here, we test whether confocal Raman microscopy (CRM) is a suitable method to reliably identify growth patterns in the commonly used archive Arctica islandica and the extinct species Pygocardia rustica (both Bivalvia). A modern A. islandica specimen from Norway has been investigated to verify the general feasibility of CRM, resulting in highly correlated standardized growth indices (r〉0.96; p〈0.0001) between CRM-derived measurements and measurements derived from the established methods of fluorescence microscopy and Mutvei’s solution staining. This demonstrates the general suitability of CRM as a method for growth pattern evaluation and cross-dating applications. Moreover, CRM may be of particular interest for paleoenvironmental reconstructions, as it yielded superior results in the analysis of fossil shell specimens (A. islandica and P. rustica) compared to both Mutvei staining and fluorescence microscopy. CRM is a reliable and valuable tool to visualize internal growth patterns in both modern and fossil calcium carbonate shells that notably also facilitates the assessment of possible diagenetic alteration prior to geochemical analysis without geochemically compromising the sample. We strongly recommend the CRM approach for the visualization of growth patterns in fossil biogenic archives, where conventional methods fail to produce useful results.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 10
    Publication Date: 2015-02-11
    Description: Understanding the climate of the past is essential for anticipating future climate change. Palaeoclimatic archives are the key to the past, but few marine archives (including tropical corals) combine long recording times (decades to centuries) with high temporal resolution (decadal to intra-annual). In temperate and polar regions carbonate shells can perform the equivalent function as a proxy archive as corals do in the tropics. The bivalve Arctica islandica is a particularly unique bio-archive owing to its wide distribution throughout the North Atlantic and its extreme longevity (up to 500 years). This paper exemplifies how information at intra-annual and decadal scales is derived from A. islandica shells and combined into a detailed picture of past conditions. Oxygen isotope analysis (δ18O) provides information on the intra-annual temperature cycle while frequency analysis of shell growth records identifies decadal variability such as a distinct 5-year signal, which might be linked to the North Atlantic Oscillation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , NonPeerReviewed
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