Ramalho, Sofia P., Ribeiro, Carlos, Hensen, Christian , Scholz, Florian , Nuzzo, Marianne, Terrinha, Pedro and Adao, Helena (2018) Benthic nematode biodiversity of the Abzu, Tiamat and Michael Ivanov mud volcanoes located along the SWIM fracture zone (Gulf of Cadiz). Marine Biodiversity, 48 (1). pp. 423-438. DOI 10.1007/s12526-017-0809-x.

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Abstract

Studies that focus on meiofaunal assemblages of
deep-sea mud volcanoes show an unpredictable abundance
and diversity in a clear response to the different environmental
conditions of the seeped sediment. The mud volcanoes Abzu,
Tiamat and M. Ivanov (ATI), are located along the SWIM1
fracture zone, in front of the accretionary wedge of the Gulf of
Cadiz (AWGC). The geological setting and the fluid geo-
chemical characteristics of the ATI mud volcanoes are differ-
ent from those located within the AWGC. The main aim of
this study is to describe and compare the spatial and vertical
distributions of the meiofauna and nematode assemblage s
from the ATI mud volcanoes, the Porto mud volcano located
in the AWGC, and a non-seep site (Site 2) as reference. The
pore-water on the uppermost sediment layers has composi-
tions close to the near-bottom seawater. The meiofauna abun-
dances were generally lower and the vertical distribution of
the assemblages showed a typical pattern, gradually decreas-
ing towards depth. The lack of spatial patterns of the standing
stocks contrasts with the spatial variability of diversity and
biomass, related to the differences in the nematode assem-
blages that are distinct between ATI, Site 2 and the Porto
mud volcano. The ATI and Site 2 assemblages are similar to
deep-sea non-seep habitats, and are clearly coupled with the
environmental conditions of the bottom seawater. No evi-
dence of seep conditions favouring the development of
specialised fauna were found. The lower diversity and the
presence of higher dominance species could be driven by dis-
tinct seepage conditions of the Porto mud volcano.

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