Environmental Pressures and Adaptations

In comparison to many habitats in the ocean, hydrothermal-vent ecosystems are subjected to an array of ‘extreme’ physical and chemical stressors (Gage & Tyler 1991; Pradillon & Gaill 2009; Van Dover 2010). These include enhanced temperatures, acidic pH conditions and high levels of H2S, which is potentially very toxic to living organisms (Craig 2010; Gage & Tyler 1991; Pradillon & Gaill 2009).

Hydrothermal vent systems may be active over a scale of 10 to 100 years (Pradillon & Gaill 2009). This is dependent upon the geographical and geological area in which they are situated and the extent of the possible volcanic and tectonic activities of that area; the result is a dynamic and unpredictable environment (Pradillon & Gaill 2009; Tait & Dipper 1998; Van Dover 2000). Collectively, these stressors cause vent sites to have a high level of instability and patchy distributions of organisms (Pradillon & Gaill 2009; Van Dover 2000).

Due to the unpredictability of H2S production from hydrothermal vents, which is essential to their environmental community, dispersal of organisms to new vent sites must be paramount in order for species to persist in the oceanic-ecosystem when dynamics of the vent site change (Gage & Tyler 1991; Pradillon & Gaill 2009).

Hessler et al 1988, showed that with subsequent visits to an area on the Galapagos Rift known as Rose Garden, the ecosystem exhibited ‘change in community structure over time’ (Gage & Tyler 1991; Hessler et al. 1988).This hydrothermal vent was shown to be primarily colonised by species such as marine tube worms (vestimentiferans), clams and mussels, such as Bathymodiolus sp. (Hessler et al. 1988).

Following disruptions to vent sites, such as after eruptions of lava or tectonic activities, causing H2S flux and water flow to stop, dynamics of the vent change (Fisher et al. 1988; Gage & Tyler 1991; Hessler et al. 1988). Vestimentiferan-species decline and Bathymodiolus sp. in the community remain unchanged, or may even increase (Hessler et al. 1988). This could be due to the mussel’s ability to filter feed as well as utilise chemoautotrophic bacteria in vent plumes and surrounding seawater (Desbruyères et al. 2006; Fisher et al. 1988; Gage & Tyler 1991; Hessler et al. 1988).

Further information on chemosynthetic bacteria and the adaptations of selected key-invertebrate species (Riftia pachyptila, Calyptogena magnifica, Bathymodiolus thermophilus, Alvinella pompejana, Rimicaris exoculata) surrounding vent sites is provided on the adjoining links of this page.

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