Geochemistry of the Snake Pit vent field and its implications for vent and non-vent fauna

Abstract

Observations made during a cruise of the R/V Professor Logachev at the Snake Pit hydrothermal vent field provide a large database with which to examine the relationships between the geochemical characteristics of the hydrothermal sediments and the fauna that inhabit the area. Correlations between the nature and geochemistry of sediments, the distribution of hydrothermai and peripheral fauna and the hydrothermal activity are established. Three geochemical zones in the Snake Pit area are distinguished. (i) The Central Zone, located within 10-100 m of black smoker chimneys, consisting mainly of hydroxide-sulphide sediments with Fe sulphides predominant. Barite is found only in this zone and vent-associated organisms distinctly predominate over non-vent fauna. (ii) The Intermediate Zone encompasses high-temperature springs at a distance from 50 to 150 m. Sediments are chiefly sulphide-hydroxide composition and are dominated by Fe hydroxide and sulphide minerals in an oxide envelope. The non-vent specific fauna show maximum concentrations. (iii) The Outer Zone is located within a radius of 150-500m from the smokers. The sediment composition is characterized by a predominance of sulphidehydroxide transitional differences with notably varying compositions of oxide and sulphide minerals. Minor sestonophages prevail in the fauna, which is typical of communities with a pronounced oligotrophic structure. From the Central Zone towards the Outer Zone, the frequency of the bacterial mats seen on photographs decreases and the hydrothermal sediments show a similar trend. Analysis of the hydrothermal sediment obtained from the cores shows: (i) Mn is absent; (ii) barite is found only in the Central Zone; and (iii) chalcopyrite and pyrrhotite concentrations decrease and opal and quartz concentrations increase with increasing distance from the nearest smoker. Comparisons between the Mid-Atlantic Ridge hydrothermal fields of TAG, Snake Pit and 15~ indicate a decrease in the hydrothermal and biological activities with latitude (TAG, Snake Pit, 15~ which might be due to their evolutionary history.

Peripheral communities of the Eastern Lau Spreading Center and Valu Fa Ridge: community composition, temporal change and comparison to near‐vent communities

“…There is a mixed zone in between that has been referred to as the distal, intermediate and median zone. This zone is inhabited by both vent endemic and non‐vent endemic fauna, while in the outer zone further away from sources of venting, the majority of the animals present are non‐vent endemic deep‐sea species (Arquit ; Sudarikov & Galkin ; Kim & Hammerstrom ). The distances of these latter zones from sources of intense venting differs among vent fields and can range from tens of meters to kilometers.…”

Megabenthic assemblage structure on three New Zealand seamounts: implications for seafloor massive sulfide mining

“…Hydrothermally inactive areas are colonised by 'background' fauna typical of hard substrata on seamounts, such as the sponges, hydroids, corals, anemones, squat lobsters, ophiuroids and holothurians inhabiting inactive areas of the Manus Basin (Galkin 1997). Over a scale of 10s to 100s of meters, chemosynthetic and background faunal assemblages exhibit zonation based on proximity to hydrothermal flow, with chemosynthetic assemblages existing in close proximity to hydrothermal flow and background assemblages existing at the vent periphery (Arquit 1990, Sudarikov & Galkin 1995. It has also been hypothesised that a third assemblage may exist at SMS deposit sites, one specific to the unique chemical environment of weathering inactive SMS deposits (Van Dover 2007, 2011.…”

Meiofauna Community in Soft Sediments at TAG and Snake Pit Hydrothermal Vent Fields

“…The Snake Pit vent field is located at the ridge axis at a water depth between 3,480 and 3,570 m, and it consists of three elongate parallel ridges (Thompson et al, 1988). The flat areas between the ridges are covered by metalliferous sediment composed of dark granular sulfides, mainly pyrrhotite, chalcopyrite, marcasite, and pyrite, and minor sphalerite (Thompson et al, 1988;Sudarikov and Galkin, 1995). Several small SMSs are known in the field, including the Beehive, Nail, Moose, Firtree, and the Cliff deposits.…”