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A chemosynthetic ecotone—"chemotone"—in the sediments surrounding deep-sea methane seeps

Ashford, Oliver S. and Guan, Shuzhe and Capone, Dante and Rigney, Katherine and Rowley, Katelynn and Orphan, Victoria and Mullin, Sean W. and Dawson, Kat S. and Cortés, Jorge and Rouse, Greg W. and Mendoza, Guillermo F. and Lee, Raymond W. and Cordes, Erik E. and Levin, Lisa A. (2021) A chemosynthetic ecotone—"chemotone"—in the sediments surrounding deep-sea methane seeps. Limnology and Oceanography, 66 (5). pp. 1687-1702. ISSN 0024-3590. doi:10.1002/lno.11713.

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Ecotones have been described as “biodiversity hotspots” from myriad environments, yet have not been studied extensively in the deep ocean. While physiologically challenging, deep-water methane seeps host highly productive communities fueled predominantly by chemosynthetic pathways. We hypothesized that the biological and geochemical influence of methane seeps extends into background habitats, resulting in the formation of a “chemotone” where chemosynthesis-based and photosynthesis-based communities overlap. To investigate this, we analyzed the macrofaunal assemblages and geochemical properties of sediments collected from “active,” “transition” (potential chemotone), and “background” habitats surrounding five Costa Rican methane seeps (depth range 377–1908 m). Sediment geochemistry demonstrated a clear distinction between active and transition habitats, but not between transition and background habitats. In contrast, biological variables confirmed the presence of a chemotone, characterized by intermediate biomass, a distinct species composition (including habitat endemics and species from both active and background habitats), and enhanced variability in species composition among samples. However, chemotone assemblages were not distinct from active and/or background assemblages in terms of faunal density, biological trait composition, or diversity. Biomass and faunal stable isotope data suggest that chemotones are driven by a gradient in food delivery, receiving supplements from chemosynthetic production in addition to available photosynthetic-based resources. Sediment geochemistry suggests that chemosynthetic food supplements are delivered across the chemotone at least in part through the water column, as opposed to reflecting exclusively in situ chemosynthetic production in sediments. Management efforts should be cognisant of the ecological attributes and spatial extent of the chemotone that surrounds deep-sea chemosynthetic environments.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ashford, Oliver S.0000-0001-5473-7057
Orphan, Victoria0000-0002-5374-6178
Mullin, Sean W.0000-0002-6225-3279
Dawson, Kat S.0000-0001-8856-4609
Cortés, Jorge0000-0001-7004-8649
Rouse, Greg W.0000-0001-9036-9263
Levin, Lisa A.0000-0002-2858-8622
Additional Information:© 2021 Association for the Sciences of Limnology and Oceanography. Issue Online: 19 May 2021; Version of Record online: 29 March 2021; Manuscript accepted: 18 December 2020; Manuscript revised: 17 October 2020; Manuscript received: 16 May 2020. We are thankful to the Ministerio de Ambiente y Energía of Costa Rica (Sistema Nacional de Áreas de Conservación/Comisión Nacional para la Gestión de la Biodiversidad) for granting collection permits (AT37-13: SINAC-CUS-PI-R-035-2017, AT42-03: SINAC-SE-064-2018). We are very grateful to the Captains, Crew, Science Party, and Alvin team of RV Atlantis legs AT37-13 and AT42-03 for facilitating sample collection. We thank Jennifer Le and Odalisca Breedy, Lillian McCormick, Natalya Gallo, and Olivia Pereira for their help with sectioning and preserving push core samples. We thank Jennifer Gonzalez and Olivia Pereira for their help with processing specimens for stable isotope analysis. We thank Sujung Lim for their part in generating the geochemical data analyzed here. We are grateful to three anonymous reviewers, whose insightful and constructive comments helped to strengthen this article. This work was funded by National Science Foundation Ocean Sciences grant numbers 1634172 and 1635219. Author Oliver S. Ashford additionally received support from Scripps Institution of Oceanography as a Postdoctoral Scholar. Conflict of Interest: None declared. Data Availability Statement: All data utilized by this study are freely available through “Figshare” (DOI: 10.6084/m9.figshare.10070282), and as Supplemental Material.
Funding AgencyGrant Number
Scripps Institution of OceanographyUNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20210430-123641944
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Official Citation:Ashford, O.S., Guan, S., Capone, D., Rigney, K., Rowley, K., Orphan, V., Mullin, S.W., Dawson, K.S., Cortés, J., Rouse, G.W., Mendoza, G.F., Lee, R.W., Cordes, E.E. and Levin, L.A. (2021), A chemosynthetic ecotone—“chemotone”—in the sediments surrounding deep-sea methane seeps. Limnol Oceanogr, 66: 1687-1702.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108904
Deposited By: Tony Diaz
Deposited On:30 Apr 2021 20:06
Last Modified:26 May 2021 21:12

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