Food-Web Complexity in Guaymas Basin Hydrothermal Vents and Cold Seeps

Type Article
Date 2016-09
Language English
Author(s) Portail Marie1, Olu Karine1, Dubois StanislasORCID2, Escobar-Briones Elva3, Gelinas Yves4, 5, Menot LenaickORCID1, Sarrazin Jozee1
Affiliation(s) 1 : Inst Carnot Ifremer EDROME, Ctr Bretagne, REM EEP, Lab Environm Profond, Plouzane, France.
2 : IFREMER, Ctr Bretagne, DYNECO, Lab Ecol Benth, Plouzane, France.
3 : Univ Nacl Autonoma Mexico, Inst Ciencias Mary & Limnol, Mexico City, DF, Mexico.
4 : Concordia Univ, Geotop, Montreal, PQ, Canada.
5 : Concordia Univ, Dept Chem & Biochem, Montreal, PQ, Canada.
Source Plos One (1932-6203) (Public Library Science), 2016-09 , Vol. 11 , N. 9 , P. e0162263 (1-33)
DOI 10.1371/journal.pone.0162263
WOS© Times Cited 15
Abstract In the Guaymas Basin, the presence of cold seeps and hydrothermal vents in close proximity, similar sedimentary settings and comparable depths offers a unique opportunity to assess and compare the functioning of these deep-sea chemosynthetic ecosystems. The food webs of five seep and four vent assemblages were studied using stable carbon and nitrogen isotope analyses. Although the two ecosystems shared similar potential basal sources, their food webs differed: seeps relied predominantly on methanotrophy and thiotrophy via the Calvin-Benson-Bassham (CBB) cycle and vents on petroleum-derived organic matter and thiotrophy via the CBB and reductive tricarboxylic acid (rTCA) cycles. In contrast to symbiotic species, the heterotrophic fauna exhibited high trophic flexibility among assemblages, suggesting weak trophic links to the metabolic diversity of chemosynthetic primary producers. At both ecosystems, food webs did not appear to be organised through predator-prey links but rather through weak trophic relationships among co-occurring species. Examples of trophic or spatial niche differentiation highlighted the importance of species-sorting processes within chemosynthetic ecosystems. Variability in food web structure, addressed through Bayesian metrics, revealed consistent trends across ecosystems. Food-web complexity significantly decreased with increasing methane concentrations, a common proxy for the intensity of seep and vent fluid fluxes. Although high fluid-fluxes have the potential to enhance primary productivity, they generate environmental constraints that may limit microbial diversity, colonisation of consumers and the structuring role of competitive interactions, leading to an overall reduction of food-web complexity and an increase in trophic redundancy. Heterogeneity provided by foundation species was identified as an additional structuring factor. According to their biological activities, foundation species may have the potential to partly release the competitive pressure within communities of low fluid-flux habitats. Finally, ecosystem functioning in vents and seeps was highly similar despite environmental differences (e.g. physico-chemistry, dominant basal sources) suggesting that ecological niches are not specifically linked to the nature of fluids. This comparison of seep and vent functioning in the Guaymas basin thus provides further supports to the hypothesis of continuity among deep-sea chemosynthetic ecosystems.
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Publisher's official version 33 17 MB Open access
S1 Table. Mean stable isotope composition (expressed in ‰) of the species, sediment and methane samples from the ten studied assemblages. 8 699 KB Open access
S1 Fig. Illustration of the copepod species nov deeply attached to Acharax aff. johnsoni gill lamellae (A) and zoom on the copepod head (B). 1 76 KB Open access
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