Discovery of a black smoker vent field and vent fauna at the Arctic Mid-Ocean Ridge - PubMed (original) (raw)

Discovery of a black smoker vent field and vent fauna at the Arctic Mid-Ocean Ridge

Rolf B Pedersen et al. Nat Commun. 2010.

Free PMC article

Abstract

The Arctic Mid-Ocean Ridge (AMOR) represents one of the most slow-spreading ridge systems on Earth. Previous attempts to locate hydrothermal vent fields and unravel the nature of venting, as well as the provenance of vent fauna at this northern and insular termination of the global ridge system, have been unsuccessful. Here, we report the first discovery of a black smoker vent field at the AMOR. The field is located on the crest of an axial volcanic ridge (AVR) and is associated with an unusually large hydrothermal deposit, which documents that extensive venting and long-lived hydrothermal systems exist at ultraslow-spreading ridges, despite their strongly reduced volcanic activity. The vent field hosts a distinct vent fauna that differs from the fauna to the south along the Mid-Atlantic Ridge. The novel vent fauna seems to have developed by local specialization and by migration of fauna from cold seeps and the Pacific.

PubMed Disclaimer

Figures

Figure 1

Figure 1. Location of the Loki's Castle Vent field.

A polar projection map showing the Arctic Mid-Ocean Ridge north of Iceland and the location of the Loki's Castle vent field (red dot). The map also shows the locations of the vent fields within the Atlantic and the Pacific ocean hosting vent endemic fauna belonging to different biogeographic provinces: white, Mid-Atlantic Ridge; yellow, Azores; orange, Western Pacific; green, North-East Pacific (biogeographic provinces from ref. 11).

Figure 2

Figure 2. Geology of the Eastern Mohns Ridge.

(a) Map showing: (1) the 30-km-long AVR hosting the vent field; (2) core complexes at the western flank of the ridge; and (3) the eastern flank that is buried by the distal parts of the Bear Island sedimentary fan, which developed during repeated Arctic glaciations during the last 3 million years. (b) Bathymetry of the AVR and surrounding terrain viewed obliquely from the south. The map shows that the vent field is located next to a rift that runs along the crest of the ridge, where normal faults appears to represent the main channel way for the hydrothermal fluids.

Figure 3

Figure 3. Characteristic invertebrates at the Loki's Castle vent field.

(a) Siboglinid tubeworms (S. contortum) associated with low-temperature diffuse venting at the flank of the hydrothermal mound. White microbial mats and small barite chimneys in the back. (b) Close-up of the siboglinid tube worms in front of white microbial mats. Note the dense populations of small gastropods (P. griegi and Skenea sp.) on the tubes. The scale bar is 5 cm. (c) Amphipods (Melitidae sp. nov.) on a chimney wall. (d) Close-up of a ∼1.5 cm juvenile Melitid amphipod. (e) Scanning electron microscopic image of chemoautotrophic gill symbionts from the Melitid amphipod (the scale bar is 3 μm). Based on 16S rDNA clone libraries, the two most abundant sequences are affiliated with a gamma proteobacterium, known as a sulphur oxidizer in the bivalve Anodontia fragilis, and sequences with 98% similarity to an uncultured Methylococcaceae known as a methanotrophic ectosymbiont on the vent crab Shinkaia crosnieri. (f) Small gastropods (P. griegi) populating a chimney wall, with an individual shown as an inset picture (∼3 mm across).

Figure 4

Figure 4. Depth of reaction zone and lithospheric structure.

(a) Along-axis profile of the central and eastern part of the Mohns Ridge showing the variations in water depth. The profile shows the 30-km-long and 800-m-high AVR hosting the Loki's Castle vent field and the distribution of similar AVRs to the south-west along the ridge. The lines marked b and c show the locations of the along-axis profiles shown in b and c. (b) Profile of the water depth along the AVR hosting Loki's Castle, and the subsurface depth of the reaction zone, as estimated by EM vent fluid composition using a Si-Cl geothermobarometer. The estimated depth of the reaction zone corresponds to the seismic layer 2–3 transition as seen further west at the Mohns Ridge (c). The depth of the reaction zone combined with the crustal thickness suggests that as much as 50% of the crust is convectively cooled by hydrothermal circulation. (c) Seismic structure across two of the AVRs shown in a (marked c) that document the unusually thin ocean crust (∼4 km) and the boundary between the different oceanic layers within the crust (data from ref. 28).

Similar articles

Cited by

References

    1. Rona P. A. et al.. Black smokers, massive sulfides and vent biota at the Mid-Atlantic Ridge. Nature 321, 33–37 (1986).
    1. Dick H. J. B. et al.. An ultraslow-spreading class of ocean ridge. Nature 426, 405–412 (2003). - PubMed
    1. Michael P. J. et al.. Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel ridge, Arctic Ocean. Nature 423, 956–961 (2003). - PubMed
    1. Baker E. T. & German C. R. On the global distribution of hydrothermal vent fields. in Mid-Ocean Ridges: Hydrothermal Interactions Between the Lithosphere and Oceans (eds German, C. R., Lin, J. & Parson, L. M.) 245–266 (Geophysical Monograph Series 148, AGU, 2004).
    1. German C. R. et al.. Hydrothermal activity along the southwest Indian Ridge. Nature 395, 490–493 (1998).

LinkOut - more resources