Deep-ocean hydrothermal vent systems can be defined as sea-floor springs, from which fluids that are enriched in hydrogen sulphide (H2S) along with other minerals; and heated by molten-rock underneath the sea floor, radiate out (Gage & Tyler 1991; Van Dover et al 2002). The fluids expelled from some vent sites, known as black smokers, can reach temperatures of up to 407°C; the hottest temperature recorded to date at an active vent site (Stafford 2006).
The discovery of hydrothermal vents occurred in 1977, with the aid of the deep-sea submersible ‘Alvin’ (Fig.2), at depths of 2,500 metres in the Galapagos Spreading-Centre, or Rift (Fig.1) (Gage & Tyler 1991; Lonsdale 1977; Tait & Dipper 1998; Van Dover 2000; Van Dover et al. 2002). The significance of encountering these hydrothermal vents was due to the presence and abundance of life forms in association with them; an oasis of life in the otherwise seemingly hostile and ‘alien’ environment of the deep sea floor, frequently at depths below 1,000m (Corliss & Ballard 1977; Gage & Tyler 1991; Pradillon & Gaill 2009; Tait & Dipper 1998). The habitat surrounding hydrothermal vents has been described as one of the most challenging for animal life situated on Earth (Pradillon & Gaill 2009; Van Dover 2000). The environment is highly unstable and unpredictable, due to the possibility of volcanic and tectonic disruptions (Pradillon & Gaill 2009). Since their discovery many new species have been described over differing geographical vent-sites, in almost all explorations (Baker & German 2004; Van Dover 2000). This diverse array of fauna and microorganisms was deemed a revolutionary scientific discovery, as solar light energy, which was once thought essential to primary-production, and hence life on Earth, is absent at such great depths (Van Dover et al. 2002).
Hydrothermal vents appear in every ocean where active, volcanic oceanic-ridges and back-arc basins are found (Fig.1) (Baker & German 2004; Corliss et al. 1979; Tait & Dipper 1998; Van Dover et al. 2002); they have also been shown to occur on seamounts, but are relatively unexplored and not discussed here (Van Dover et al. 2002). Dynamics of vent-sites vary at different geological sites over geographical scales, and they may sustain a diverse ecosystem of organisms, many of which utilise chemoautotrophic-bacteria for primary-food production (Baker & German 2004; Corliss et al. 1979; Van Dover et al. 2002).
Figure 1. Distributions of known, active hydrothermal vent sites, ‘Coloured lines show areas which have been shown to share several of the same species and solid lines show areas that are comparatively well described in scientific literature,’(Van Dover 2010).
Figure 2. 1978 ‘Alvin’ Deep-Sea Submersible, NOAA
Here I will describe and discuss the ‘extreme’ ecosystems surrounding hydrothermal vents of both oceanic ridges and back-arc basins; and the natural and possible anthropogenic impacts of these environments on some of their associated biological communities and their adaptations, if any, to survive.