Hydrocarbon and mineral extraction

Currently in the deep sea environment, two forms of resource extraction impact on echinoderms of the deep sea benthic environment. Oil extraction and Manganese nodule mining activities will both have detrimental effects of physical and biological structure of benthic echinoderm communities.

The majority of oil production is sourced from declining terrestrial and shallow water reserves. In the future it can be predicted that there will be a significant shift to exploitation of deep sea environment for oil resources as human demands for oil increase. The impact of increased drilling on the sea floor to echinoderms will be two-fold. Initially sessile echinoderm species such as stalked crinoids will suffer mortality in the locality of the metallic drilling structure, which has only a minor localized impact. The second greater impact will be the disposal of dill cuttings.

In the process of deep sea drilling under immense pressure, drilling mud is require to safety extract oil. Drill bits involved must be cooled and lubricated during extraction and are done so by drilling mud (a mixture of water, ground rock and clay) (Grant and Briggs, 2002). Drilling mud collects drill cuttings (often contaminated with heavy metals and hydrocarbons) which are then discharged onto the sea bed, where they accumulate and smoother benthic fauna (Grant and Briggs, 2002). This will cause wide spread mortality of filter and suspension feeding echinoderms as feeding apparatus is smothered.

Mining or ‘collection’ of manganese nodules on the deep sea floor will also impact on benthic dwelling echinoderms both direct and indirectly. Manganese nodules are retrieved by remotely operate vehicles (ROVs) and tracked computer vehicles from depths of 3000m for their content of value metals such as cobalt (used in the production of jet engines) (Glover and Smith, 2003).

Direct impacts of manganese nodules include disturbance and mortality cause by the paths of collection vehicles (Gage and Tyler, 1991). As the vehicles collect nodules attached fauna such as stalked crinoids will be killed and any fauna in the pathway such as holothurians and echinoids will also suffer mortality detrimental to the benthic echinoderm community. However it has been proposed that the tracks of ROVs will not be detrimental to all echinoderm species as predatory species of starfish will experience a temporal rise in food levels and an increase in diversity may result from opportunistic species taking residence in the tracks supplementing the existing community (Jumars, 1981). Similar to the impacts of drilling, manganese collections will also cause the re-suspension and deposition of sediments. Suspended sediments will remain and spread within the benthic boundary layer over a large area due to currents, smothering organism feeding apparatus and diluting organic suspended material resulting in mass mortality and starvation of benthic echinoderms (Thiel et al., 2001).

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