Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and potential relevance for the environment
<p><strong>Abstract.</strong> Methane (<span class="inline-formula">CH<sub>4</sub></span>) production within the oceanic mixed layer is a widespread phenomenon, but the underlying mechanisms are still under debate. Marine algae might contribute to...
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| Main Authors: | , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
28 Oct 2019
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| In: |
Biogeosciences
Year: 2019, Volume: 16, Issue: 20, Pages: 4129-4144 |
| ISSN: | 1726-4189 |
| DOI: | https://doi.org/10.5194/bg-16-4129-2019 |
| Online Access: | Verlag, Volltext: https://doi.org/https://doi.org/10.5194/bg-16-4129-2019 Verlag, Volltext: https://www.biogeosciences.net/16/4129/2019/ 
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| Author Notes: | Thomas Klintzsch, Gerald Langer, Gernot Nehrke, Anna Wieland, Katharina Lenhart, and Frank Keppler |
| Summary: | <p><strong>Abstract.</strong> Methane (<span class="inline-formula">CH<sub>4</sub></span>) production within the oceanic mixed layer is a widespread phenomenon, but the underlying mechanisms are still under debate. Marine algae might contribute to the observed <span class="inline-formula">CH<sub>4</sub></span> oversaturation in oxic waters, but so far direct evidence for <span class="inline-formula">CH<sub>4</sub></span> production by marine algae has only been provided for the coccolithophore <i>Emiliania huxleyi</i>.</p> <p>In the present study we investigated, next to <i>E. huxleyi</i>, other widespread haptophytes, i.e., <i>Phaeocystis globosa</i> and <i>Chrysochromulina</i> sp. We performed <span class="inline-formula">CH<sub>4</sub></span> production and stable carbon isotope measurements and provide unambiguous evidence that all three investigated marine algae are involved in the production of <span class="inline-formula">CH<sub>4</sub></span> under oxic conditions. Rates ranged from <span class="inline-formula">1.9±0.6</span> to <span class="inline-formula">3.1±0.4</span> <span class="inline-formula">µ</span>g of <span class="inline-formula">CH<sub>4</sub></span> per gram of POC (particulate organic carbon) per day, with <i>Chrysochromulina</i> sp. and <i>E. huxleyi</i> showing the lowest and highest rates, respectively. Cellular <span class="inline-formula">CH<sub>4</sub></span> production rates ranged from <span class="inline-formula">16.8±6.5</span> (<i>P. globosa</i>) to <span class="inline-formula">62.3±6.4</span> ag <span class="inline-formula">CH<sub>4</sub></span> cell<span class="inline-formula"><sup>−1</sup></span> d<span class="inline-formula"><sup>−1</sup></span> (<i>E. huxleyi</i>; ag <span class="inline-formula">=</span> 10<span class="inline-formula"><sup>−18</sup></span> g). In cultures that were treated with <span class="inline-formula"><sup>13</sup>C</span>-labeled hydrogen carbonate, <span class="inline-formula"><i>δ</i><sup>13</sup>CH<sub>4</sub></span> values increased with incubation time, resulting from the conversion of <span class="inline-formula"><sup>13</sup>C</span>-hydrogen carbonate to <span class="inline-formula"><sup>13</sup>CH<sub>4</sub></span>. The addition of <span class="inline-formula"><sup>13</sup>C</span>-labeled dimethyl sulfide, dimethyl sulfoxide, and methionine sulfoxide - known algal metabolites that are ubiquitous in marine surface layers - resulted in the occurrence of <span class="inline-formula"><sup>13</sup>C</span>-enriched <span class="inline-formula">CH<sub>4</sub></span> in cultures of <i>E. huxleyi</i>, clearly indicating that methylated sulfur compounds are also precursors of <span class="inline-formula">CH<sub>4</sub></span>. By comparing the algal <span class="inline-formula">CH<sub>4</sub></span> production rates from our laboratory experiments with results previously reported in two field studies of the Pacific Ocean and the Baltic Sea, we might conclude that algae-mediated <span class="inline-formula">CH<sub>4</sub></span> release is contributing to <span class="inline-formula">CH<sub>4</sub></span> oversaturation in oxic waters. Therefore, we propose that haptophyte mediated <span class="inline-formula">CH<sub>4</sub></span> production could be a common and important process in marine surface waters.</p> |
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| Item Description: | Gesehen am 31.10.2019 |
| Physical Description: | Online Resource |
| ISSN: | 1726-4189 |
| DOI: | https://doi.org/10.5194/bg-16-4129-2019 |