Vanishing coccolith vital effects with alleviated carbon limitation
By recreating a range of geologically relevant concentrations of dissolved inorganic carbon (DIC) in the laboratory, we demonstrate that the magnitude of the vital effects in both carbon and oxygen isotopes of coccolith calcite of multiple species relates to ambient DIC concentration. Under high DIC...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/301/2016/bg-13-301-2016.pdf |
| Summary: | By recreating a range of geologically relevant concentrations of dissolved
inorganic carbon (DIC) in the laboratory, we demonstrate that the magnitude
of the vital effects in both carbon and oxygen isotopes of coccolith calcite
of multiple species relates to ambient DIC concentration. Under high DIC
levels, all the examined coccoliths exhibit significantly reduced isotopic
offsets from inorganic calcite compared to the substantial vital effects
expressed at low (preindustrial and present-day) DIC concentrations. The
supply of carbon to the cell exerts a primary control on biological
fractionation in coccolith calcite via the modulation of coccolithophore
growth rate, cell size and carbon utilisation by photosynthesis and
calcification, altogether accounting for the observed interspecific
differences between coccolith species. These laboratory observations support
the recent hypothesis from field observations that the appearance of
interspecific vital effect in coccolithophores coincides with the long-term
Neogene decline of atmospheric CO<sub>2</sub> concentrations and bring further
valuable constraints by demonstrating a convergence of all examined species
towards inorganic values at high <i>p</i>CO<sub>2</sub> regimes. This study provides
palaeoceanographers with a biogeochemical framework that can be utilised to
further develop the use of calcareous nannofossils in palaeoceanography to
derive sea surface temperature and <i>p</i>CO<sub>2</sub> levels, especially during
periods of relatively elevated <i>p</i>CO<sub>2</sub> concentrations, as they prevailed
during most of the Meso-Cenozoic. |
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| ISSN: | 1726-4170 1726-4189 |