Journal of the Marine Biological Association of the UK



Deep-sea hydrothermal vent communities of the Logatchev area (14°45′N, Mid-Atlantic Ridge): diverse biotopes and high biomass


A.V.  Gebruk a1p1c1, P.  Chevaldonné a2, T.  Shank a3p2, R.A.  Lutz a3 and R.C.  Vrijenhoek a3
a1 P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovsky Pr. 36, Moscow, 117851, Russia
a2 CNRS-UMR DIMAR, Station Marine d'Endoume, Centre d'Océanologie de Marseille, Rue de la Batterie des Lions, 13007 Marseille, France
a3 Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521, USA

Abstract

Results from recent biological studies (including three Alvin dives in July 1997) of the southernmost deep-sea hydrothermal area known on the Mid-Atlantic Ridge (MAR), the Logatchev hydrothermal area, are described. The Logatchev area includes three vent fields, each with a different geological setting corresponding to: (1) a large sulphide mound with ‘smoking craters’; (2) an active chimney complex (known as ‘Irina-2’); and (3) a diffuse flow through soft sediment (‘Anya's Garden’). Hydrothermal communities found at these fields differ considerably: Anya's Garden is dominated by vesicomyid clams, Ectenagena sp. aff. kaikoi, Irina-2 by mytilid mussels, Bathymodiolus sp. aff. puteoserpentis, with swarms of shrimps and other rich associated fauna, whereas on the main mound the fauna as a whole is less abundant and less diverse. This is the first record of a living clam population on the MAR. Other bivalves found on the clam field included thyasirids, Thyasira (Parathyasira) spp., not reported previously from deep-sea hot vent communities. The biomass on the mussel bed at Irina-2 exceeds 70 kg m−2 (wet weight with shells) and is the highest known on the MAR. The large shrimp population at Irina-2 includes swarms of Rimicaris exoculata. A diverse shrimp fauna (including a new species Alvinocaris sp. aff. muricola) on the mussel bed is dominated by Mirocaris keldyshi. Overall the Logatchev area is dominated by mussels which may be attributable to the presence of both methane-oxidizing (dominant type) and sulphur-oxidizing bacterial symbionts in their gills. The diversity of vent organisms and biotopes at Logatchev appears to be the highest on the MAR.

(Received April 23 1999)
(Accepted December 13 1999)


Correspondence:
c1 E-mail: avgebruk@mtu-net.ru
p1 Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK
p2 Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA