title: Impact of high CO2 on the geochemistry of the coralline algae Lithothamnion glaciale.
abstract: Coralline algae are a significant component of the benthic ecosystem. Their ability to withstand physical stresses in high energy environments relies on their skeletal structure which is composed of high Mg-calcite. High Mg-calcite is, however, the most soluble form of calcium carbonate and therefore potentially vulnerable to the change in carbonate chemistry resulting from the absorption of anthropogenic CO2 by the ocean. We examine the geochemistry of the cold water coralline alga Lithothamnion glaciale grown under predicted future (year 2050) high pCO2 (589 μatm) using Electron microprobe and NanoSIMS analysis. In the natural and control material, higher Mg calcite forms clear concentric bands around the algal cells. As expected, summer growth has a higher Mg content compared to the winter growth. In contrast, under elevated CO2 no banding of Mg is recognisable and overall Mg concentrations are lower. This reduction in Mg in the carbonate undermines the accuracy of the Mg/Ca ratio as proxy for past temperatures in time intervals with significantly different carbonate chemistry. Fundamentally, the loss of Mg in the calcite may reduce elasticity thereby changing the structural properties, which may affect the ability of L. glaciale to efficiently function as a habitat former in the future ocean.
authors: School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
authors: F
authors: F
authors: Ragazzola
authors: School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
authors: L C
authors: LC
authors: Foster
authors: Interface Analysis Centre, School of Physics, Tyndall Avenue, Bristol BS8 1TL, UK.
authors: C J
authors: CJ
authors: Jones
authors: Interface Analysis Centre, School of Physics, Tyndall Avenue, Bristol BS8 1TL, UK.
authors: T B
authors: TB
authors: Scott
authors: GEOMAR | Helmholtz Centre for Ocean Research Kiel, Wischhofstrße 1-3, 24148 Kiel, Germany.
authors: J
authors: J
authors: Fietzke
authors: Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Australia.
authors: M R
authors: MR
authors: Kilburn
authors: School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
authors: D N
authors: DN
authors: Schmidt
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry* / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism*; D017753:Ecosystem; D008274:Magnesium / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology; D000461:Rhodophyta / Q000254:growth & development / Q000378:metabolism*; D012621:Seasons; D018629:Spectrometry, Mass, Secondary Ion; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D002245:Carbon Dioxide; D002119:Calcium Carbonate; D008274:Magnesium