Temporal and spatial patterns of biological community development at nascent deep-sea hydrothermal vents (9°50 N, East Pacific Rise)

摘要: The April 1991 discovery of newly formed hydrothermal vents in areas recent volcanic eruption between 9°45′N and 9°52′N on the East Pacific Rise provided a unique opportunity to follow temporal changes biological community structure from “birth” numerous deep-sea vents. In March l992, DSV Alvin was used deploy an on-bottom observatory, Biologic–Geologic Transect, monitor faunal succession along 1.37 km segment axial summit caldera 9°49.61′N 9°50.36′N (depth ∼2520 m). Photo- videographic documentation megafaunal colonization chemical analyses diffuse fluids associated with many these developing communities within Transect were performed 1992, December 1993, October 1994, November 1995. Photographic time-series revealed following sequence events low-temperature venting areas. (1) Immediately eruption, hydrogen sulfide iron concentrations extremely high (>1 mmol kg-1) microbially derived material blanketed active form thick microbial mats. (2) Mobile vent fauna (e.g. amphipods, copepods, octopods, galatheid brachyuran crabs) non-vent nematocarcinid shrimp) proliferated response this increased production. (3) Within 1 yr areal coverage mat reduced by ∼60% individuals vestimentiferan tube worm Tevnia jerichonana settled gregariously where flow most intense. (4) Two years after maximum levels H2S decreased almost half (from 1.90 0.97 dense thickets Riftia pachyptila dominated openings previously inhabited jerichonana. (5) Three declined further 0.88 kg-1 mussels (Bathymodiolus thermophilus) observed basaltic substrates. (6) Four crabs serpulid polychaetes abundance close as 0.72 kg-1. Also time had colonized tubes pachyptila. (7) Between 3 5 there 2- 3-fold increase number species assemblages. absence additional volcanic/tectonic disturbance, we predict that mytilid vesicomyid bivalves will gradually replace vestimentiferans dominant megafauna 5–10 eruption. We also anticipate suspension feeders decline during period while carnivores increase. hypothesize above series (1–7) represents general successional occur at northern contiguous ridge axes. Megafaunal is considered be consequence intimate interaction life-history strategies individual species, physical oceanographic processes, dynamic environment. Our observations indicate successful sequential Bathymodiolus thermophilus, may strongly influenced geochemical conditions. Additional evidence demonstrating link flux, fluid geochemistry, included rapid death several assemblages coincident abrupt composition local refocusing or cessation flow. These correlations suggest future models intermediate fast-spreading mid-ocean ridges should consider not only interplay species-specific strategies, productivity, but influence changing conditions species.