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- Henderiks, Jorijntje, et al.
(författare)
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Coccolithophore growth, chemistry and calcification under decoupled ocean carbonate chemistry
- 2008
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Excess anthropogenic atmospheric CO2 is absorbed largely by the oceans, causing acidification of the biologically productive surface waters with potential detrimental effects on marine biocalcification (The Royal Society, 2005). Despite the intracellular nature of coccolithophore calcification, previous experimental work confirmed that some (but not all) modern coccolithophores decrease calcification as pCO2 increases. However, from these culture experiments, it has been impossible to determine which carbonate system parameter is fundamental to coccolithogenesis across different species of coccolithophore because the DIC is fixed and the carbonate saturation state and pH are inversely proportional to pCO2. Additionally, these culture scenarios do not accurately capture the chemistry of the modern evolving ocean where increasing pCO2 drives a decrease in ocean pH but also an increase in dissolved inorganic carbon (DIC). Our aim was to decouple the pH from the DIC in culture experiments of three species: Emiliania huxleyi, Gephyrocapsa oceanica and Coccolithus braarudii (pelagicus), representative of two distinct phylogenetic orders and major families of coccolithophore, in order to disentangle which carbonate system parameter is crucial for calcification and develop a mechanistic view of coccolithophore response to elevated pCO2.Cultures were grown in North Sea water, under a constant pH of 8.13 ± 0.02, but with manipulated dissolved inorganic carbon (DIC) concentrations to represent surface water conditions ranging from the last glacial maximum to ~5 times pre-industrial pCO2. Our results confirm that there are strong species-specific responses and potentially fundamental differences in physiology between E. huxleyi and G. oceanica on the one, and C. braarudii on the other hand. At pH 8, algal growth rates, cell size and calcite production by E. huxleyi and G. oceanica remained unaffected by large increases in carbonate ion and DIC. By contrast, C. braarudii showed drastically lowered growth rates, significantly smaller cell and coccosphere diameters as well as coccolith malformation, under highly elevated carbonate ion and DIC. Due to the distinct isotopic composition of bicarbonate and carbonate ions, the isotopic composition of coccolithophore calcite could provide additional information on the physiological pathway of calcification. Both δ13C and δ18O of G. oceanica remained constant across all culture treatments. But the isotopic composition of C. braarudii was significantly depleted under low carbonate ion and DIC conditions, most likely as a result of kinetic controls at the higher growth rates under these conditions. G. oceanica therefore appears to respond primarily to pH, and C. braarudii to carbonate ion. This contrasting behaviour likely reveals fundamentally different physiological pathways of carbon metabolism and calcification between these two species, which could be reminiscent of adaptation to ambient conditions at the time of evolution of each lineage (Henderiks and Rickaby, 2007).ReferencesHenderiks, J. and Rickaby, R. E. M.: A coccolithophore concept for constraining the Cenozoic carbon cycle, Biogeosciences, 4, 323-329, 2007.The Royal Society: Ocean acidification due to increasing atmospheric carbon dioxide, Policy Document 12/05, 60 pp., 2005.
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| 2. |
- Schiebel, Ralf, et al.
(författare)
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Advances in planktonic foraminifer research : New perspectives for paleoceanography
- 2018
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Ingår i: Revue de Micropaleontologie. - : Elsevier BV. - 0035-1598 .- 1873-4413. ; 61:3-4, s. 113-138
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Forskningsöversikt (refereegranskat)abstract
- Planktonic foraminifer tests are major archives of environmental change and provide a multitude of proxies in paleoceanography and paleoclimatology. The application of such proxies is contingent upon a collaborative effort to better understand how the living organisms record the properties of their environment and how the resulting signals are recorded in marine sediments. In this contribution, we provide a review of the rapidly developing sub-fields of research, where new advances have been made possibleby technological developments, and by cross-disciplinary work of the scientific community. Following brief historical overviews of the sub-fields, we discuss the latest advances in planktonic foraminifer research and highlight the resulting new perspectives in ocean and climate research. Natural classification based on consistent species concepts forms the basis for analysis of any foraminifer-derived proxy. New approaches in taxonomy and phylogeny of Cenozoic planktonic foraminifers (Section 2) are presented, highlighting new perspectives on sensitivity and response of planktonic foraminifers to the changing climate and environment (Section 4). Calibration of foraminifer-specific data and environmental parameters is improving along with the technical development of probes and the access to samples from the natural environment (Section 3), enhancing our understanding of the ever-changing climate and ocean system. Comprehension of sedimentation and flux dynamics facilitates maximum gain of information from fossil assemblages (Section 5). Subtle changes in the physical (e.g., temperature), chemical (e.g., pH), and biological (e.g., food) conditions of ambient seawater affect the abundance of species and composition of assemblages as well as the chemical composition of the foraminifer shell and provide increasingly-detailed proxy data on paleoenvironments (Section 6).
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