Fig 1.
Location of the study sites in the Guaymas Basin.
(a) cold seeps on the Sonora margin (Ayala, Vasconcelos and Juarez sites), (b) hydrothermal vents on the Southern Trough (Rebecca’s Roots, Mat Mound, Morelos and Mega Mat sites) and (c) the off-axis reference site located in between.
Fig 2.
Images of the studied assemblages at seeps.
(A) Beggiatoa spp. microbial mat (S_Mat) and Hyalogyrina sp. Gastropoda (S_Gast), (B) Archivesica gigas Vesicomyidae (S_VesA), (C) Phreagena soyoae Vesicomyidae (S_VesP), (D) Escarpia spicata and Lamellibrachia barhami Siboglinidae (S_Sib) and vents: (E) Beggiatoa spp. microbial mat (V_Mat), (F) Archivesica gigas Vesicomyidae (V_VesA), (G) Paralvinella grasslei and P. bactericola Alvinellidae (V_Alv) and (H) Riftia pachyptila Siboglinidae (V_Sib).
Table 1.
Abbreviations and locations of the different assemblages studied in the Guaymas Basin.
Table 2.
Isotope signature estimates for the potentially dominant basal sources in seeps and vents in the Guaymas Basin.
Table 3.
Resume of the food web metrics with their acronyms and significance.
Fig 3.
Biplots of carbon (δ13C) and nitrogen (δ15N) mean ± SD signatures of consumers and food resources.
Endosymbiotic species are figured in green and heterotrophic consumers in black symbols. Isotopic signatures of the reference site POM (POM_ref) are provided as an estimator of the photosynthesis-derived organic matter, the values of POM within each assemblage (POM_loc) are used to characterise the local mixture between endogenous and exogenous organic matter. δ13C ranges of endogenous microbes are represented while their δ15N signatures are unknown. Thiotrophy I and II refer to the CBB and rTCA cycles, respectively.
Fig 4.
Trophic guilds of Guaymas seeps and vents taxa.
Species from seeps and vents are figured in blue and red, respectively, except those primarily sustained by photosynthetic organic matter that are shown in black symbols.
Fig 5.
Relative number of taxa per trophic guilds ordered along an increasing fluid-flux gradient with methane concentrations used as a proxy.
Table 4.
Biotic interactions identified at the different study sites.
Table 5.
Variability of carbon and nitrogen isotope ratios among co-occurring foundation species in the Guaymas vent and seep ecosystems.
Table 6.
Variability of carbon and nitrogen isotope ratios of endosymbiotic species among assemblages in the Guaymas vent and seep ecosystems.
Table 7.
Variability of carbon isotope ratios of heterotrophic species among assemblages in the Guaymas vent and seep ecosystems.
Fig 6.
Spatial variability of nitrogen isotope ratios.
(A) Regression between mean δ15N signatures of primary consumers and the remaining consumers for all assemblages (p_value = 0.001, adjusted R2 = 0.73), (B) Regression between mean faunal δ15N signatures and log-transformed ammonium concentrations for soft-sediment assemblages (p_value = 0.02, adjusted R2 = 0.66).
Fig 7.
(A) Solid lines enclose the standard ellipse area (SEAc), containing ca. 40% of the data. (B) Density plots showing the credibility intervals of the Bayesian standard ellipse areas (SEAb). Black squares are the mode SEA, and boxes indicate the 50, 75 and 95% credible intervals. Red squares are the sample-size-corrected SEA (SEAc). Numbers below boxes give the number of invertebrate species sampled.
Fig 8.
Bayesian results for the δ13C range (CR), δ15N range (NR), mean distance to centroid (CD) and the coefficient of variation of the nearest neighbour distance (CVNND).
Black dots are the modes and boxes indicate the 50, 75 and 95% credibility intervals, from wider to thinner.
Fig 9.
Spatial variability of food web structure.
(A) Regression lines with respect to methane concentrations for dCR (p = 0.004, adjusted R2 = 0.67), SEAb (p = 0.09, adjusted R2 = 0.25), CD (p = 0.08, adjusted R2 = 0.28) and CVNND (p = 0.02, adjusted R2 = 0.47) and (B) Regression lines with respect to alpha diversity (Es(41)) for dCR (p = 0.01, adjusted R2 = 0.58), SEAb (p = 0.01, adjusted R2 = 0.59), CD (p = 0.007, adjusted R2 = 0.62).
Fig 10.
Updated conceptual diagram of faunal community structure and food-web patterns along fluid-flux gradients within Guaymas seep and vent ecosystems.