Unexpected scarcity of ANME archaea in hydrocarbon seeps within Monterey Bay
<p>Marine hydrocarbon seeps typically harbor a relatively predictable microbiome, including anaerobic methanotrophic (ANME) archaea. Here, we sampled two cold seeps in Monterey Bay, CA – Clam Field and Extrovert Cliff – which have been known for decades but never characterized microbiologicall...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-01-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/385/2025/bg-22-385-2025.pdf |
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| Summary: | <p>Marine hydrocarbon seeps typically harbor a relatively predictable microbiome, including anaerobic methanotrophic (ANME) archaea. Here, we sampled two cold seeps in Monterey Bay, CA – Clam Field and Extrovert Cliff – which have been known for decades but never characterized microbiologically. Many aspects of these seeps were typical of seeps worldwide, including elevated methane and sulfide concentrations, <span class="inline-formula"><sup>13</sup></span>C-depleted dissolved inorganic carbon, and the presence of characteristic macrofauna. However, we observed atypical microbial communities: extremely few ANME sequences were detected in either 16S rRNA or <i>mcrA</i> gene surveys at Clam Field (<span class="inline-formula"><</span> 0.1 % of total community reads), even after 6 months of incubation with methane in the laboratory, and only slightly more ANME sequences were recovered from Extrovert Cliff (<span class="inline-formula"><</span> 0.3 % of total community reads). At Clam Field, a lack of ANME <i>mcrA</i> transcription, a lack of methane-dependent sulfate reduction, and a linear porewater methane profile were consistent with low or absent methanotrophy. Although the reason for the scarcity of ANME archaea is still unclear, we postulate that non-methane hydrocarbon release excludes anaerobic methanotrophs directly or indirectly (e.g., through competitive interactions with hydrocarbon-degrading bacteria). Our findings highlight the potential for hydrocarbon seeps without this critical biofilter and therefore greater methane emissions from sediments.</p> |
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| ISSN: | 1726-4170 1726-4189 |