Articles | Volume 12, issue 18
Research article
21 Sep 2015
Research article |  | 21 Sep 2015

Comparative study of vent and seep macrofaunal communities in the Guaymas Basin

M. Portail, K. Olu, E. Escobar-Briones, J. C. Caprais, L. Menot, M. Waeles, P. Cruaud, P. M. Sarradin, A. Godfroy, and J. Sarrazin

Abstract. Understanding the ecological processes and connectivity of chemosynthetic deep-sea ecosystems requires comparative studies. In the Guaymas Basin (Gulf of California, Mexico), the presence of seeps and vents in the absence of a biogeographic barrier, and comparable sedimentary settings and depths offers a unique opportunity to assess the role of ecosystem-specific environmental conditions on macrofaunal communities. Six seep and four vent assemblages were studied, three of which were characterised by common major foundation taxa: vesicomyid bivalves, siboglinid tubeworms and microbial mats. Macrofaunal community structure at the family level showed that density, diversity and composition patterns were primarily shaped by seep- and vent-common abiotic factors including methane and hydrogen sulfide concentrations, whereas vent environmental specificities (higher temperature, higher metal concentrations and lower pH) were not significant. The type of substratum and the heterogeneity provided by foundation species were identified as additional structuring factors and their roles were found to vary according to fluid regimes. At the family level, seep and vent similarity reached at least 58 %. All vent families were found at seeps and each seep-specific family displayed low relative abundances (< 5 %). Moreover, 85 % of the identified species among dominant families were shared between seep and vent ecosystems. This study provides further support to the hypothesis of continuity among deep-sea seep and vent ecosystems.

Short summary
The absence of biogeographic barrier between seep and vent ecosystems in the Guaymas Basin offers the opportunity to assess the role of environmental conditions in the distribution of macrofaunal communities. Our results showed that community structure was primarily shaped by common abiotic factors. In addition, a high number of common species were shared, suggesting frequent connections between the two ecosystems. Overall, this study supports the hypothesis of a continuum among vents and seeps.
Final-revised paper