Physiological control on carbon isotope fractionation in marine phytoplankton
<p>One of the great challenges in biogeochemical research over the past half a century has been to quantify and understand the mechanisms underlying stable carbon isotope fractionation (<span class="inline-formula"><i>ε</i><sub>p</sub>)</span> in p...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-07-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/19/3305/2022/bg-19-3305-2022.pdf |
| Summary: | <p>One of the great challenges in biogeochemical research over the
past half a century has been to quantify and understand the mechanisms
underlying stable carbon isotope fractionation (<span class="inline-formula"><i>ε</i><sub>p</sub>)</span> in
phytoplankton in response to changing CO<span class="inline-formula"><sub>2</sub></span> concentrations. This interest is partly grounded in the use of fossil photosynthetic organism
remains as a proxy for past atmospheric CO<span class="inline-formula"><sub>2</sub></span> levels. Phytoplankton
organic carbon is depleted in <span class="inline-formula"><sup>13</sup></span>C compared to its source because of
kinetic fractionation by the enzyme RubisCO during photosynthetic carbon
fixation, as well as through physiological pathways upstream of RubisCO.
Moreover, other factors such as nutrient limitation, variations in light
regime as well as phytoplankton culturing systems and inorganic carbon
manipulation approaches may confound the influence of aquatic CO<span class="inline-formula"><sub>2</sub></span>
concentrations [CO<span class="inline-formula"><sub>2</sub></span>] on <span class="inline-formula"><i>ε</i><sub>p</sub></span>. Here, based on
experimental data compiled from the literature, we assess which underlying
physiological processes cause the observed differences in <span class="inline-formula"><i>ε</i><sub>p</sub></span> for various phytoplankton groups in response to C-demand/C-supply, i.e., particulate organic carbon (POC) production <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="880d1b22cfae9b4167ff115d05c6894c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-3305-2022-ie00001.svg" width="8pt" height="14pt" src="bg-19-3305-2022-ie00001.png"/></svg:svg></span></span> [CO<span class="inline-formula"><sub>2</sub></span>]) and test potential confounding factors.
Culturing approaches and methods of carbonate chemistry manipulation were
found to best explain the differences in <span class="inline-formula"><i>ε</i><sub>p</sub></span> between
studies, although day length was an important predictor for <span class="inline-formula"><i>ε</i><sub>p</sub></span> in haptophytes. Extrapolating results from culturing experiments to
natural environments and for proxy applications therefore require caution,
and it should be carefully considered whether culture methods and
experimental conditions are representative of natural environments.</p> |
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| ISSN: | 1726-4170 1726-4189 |