A threefold perspective on the role of a pockmark in benthic faunal communities and biodiversity patterns

Type Article
Date 2021-01
Language English
Author(s) Sánchez Nuria1, Zeppilli DanielaORCID1, Baldrighi Elisa1, Vanreusel Ann2, Gasimandova Lahitsiresy Max1, Brandily Christophe1, Pastor Lucie1, Macheriotou Lara2, García-Gómez Guillermo3, Dupré StephanieORCID4, Olu KarineORCID1
Affiliation(s) 1 : Institut Français de Recherche pour l'Exploitation de la MER (IFREMER), Laboratoire Environnement Profond, France
2 : Marine Biology, Ghent University, Belgium
3 : School of Environment Sciences Earth, Ocean & Ecology Sciences Department, University of Liverpool, UK
4 : Institut Français de Recherche pour l'Exploitation de la MER (IFREMER), Unité Géosciences Marines, France
Source Deep-sea Research Part I-oceanographic Research Papers (0967-0637) (Elsevier BV), 2021-01 , Vol. 167 , P. 103425 (17p.)
DOI 10.1016/j.dsr.2020.103425
WOS© Times Cited 8
Keyword(s) Pockmark, Meiofauna, Macrofauna, Foraminifera, Nematoda, Polychaeta

Pockmarks are circular-shaped depressions that increase seabed heterogeneity and are characterized by discontinuous fluid emissions. To understand how environmental conditions of pockmarks affect the structure of macro- and meiofauna, we investigated two sites in a pockmark field in the northwestern Madagascar margin. In a comparative approach, we explored the community structure of the dominant taxa (Polychaeta, Nematoda and hyaline foraminifera) in each component (macro-, metazoan meiofauna and foraminifera, respectively). The investigated active pockmark showed approximately two times higher meiofauna abundance compared to in a site away from another pockmark field, but macrofauna showed the opposite trend, with almost half density at the pockmark site. However, at both sites, macro- and meiofauna showed higher richness and abundance values in the top well-oxygenated layers of the sediment than in the underlaying ones. Polychaeta and Nematoda showed lower richness in the pockmark, opposed to hyaline foraminiferans, but lower evenness in the pockmark was found for the three groups. The detection of gas flares in the water column attests of the recent activity within the pockmark. High amount of sulfur-bearing minerals (mainly pyrite) evidences a production of dissolved free sulfides (not detected at the time of sampling) by sulfate reduction process driven by organic matter degradation and anaerobic oxidation of methane. Furthermore, recent increase in sedimentation rates in the past 70 years and organic matter inputs could have led to higher organic matter degradation rates resulting in reduced conditions and a high oxygen consumption. All this together seem to act as key factors in the determination of variation in richness, abundance and community composition of macrofauna and meiofauna. Additionally, some taxa seem to be more tolerant to these extreme conditions, such as species belonging to the Nematoda genus Desmodora and the phylum Kinorhyncha, which are highly abundant in the pockmark, and hence, may be considered as potential bioindicators of pockmark activity in this area. Further studies are required for a better assessment.

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Sánchez Nuria, Zeppilli Daniela, Baldrighi Elisa, Vanreusel Ann, Gasimandova Lahitsiresy Max, Brandily Christophe, Pastor Lucie, Macheriotou Lara, García-Gómez Guillermo, Dupré Stephanie, Olu Karine (2021). A threefold perspective on the role of a pockmark in benthic faunal communities and biodiversity patterns. Deep-sea Research Part I-oceanographic Research Papers, 167, 103425 (17p.). Publisher's official version : https://doi.org/10.1016/j.dsr.2020.103425 , Open Access version : https://archimer.ifremer.fr/doc/00657/76932/