Hydrostatic Pressure—Temperature effects on Deep-sea Colonisation

Synopsis A diverse benthic and bathypelagic fauna was first incontrovertably established by the deep-sea samples of H.M.S.Challenger, and demonstrated the ability of organisms to live and reproduce in the deep, dark and cold abyssal environment of enormous hydrostatic pressure as high as 1000 atm (14 000 psi) on trench floors at 10 000 metres. The investigations of Regnard (1891), Fontaine (1930) and Ebbecke (1935) established that various shallow animals have the capacity to withstand increased hydrostatic pressure. This paper deals with the response of whole organisms, mainly shallow-water metazoans, to hydrostatic pressure-temperature effects. The level of occurrence of pressure-induced increased activity (R1), onset of paralysis or tetany (T) and LD50are discussed for tropical and temperate marine species in relationship to temperature and hydrostatic pressure. The pressure sensitivity and resistance exhibited by different species are examined in relation to various hypotheses and theories such as (1) group effect, in which Schlieper (1968) claims that those shallow species that belong to the group which has successfully colonised the deep sea, such as Echinodermata, Mollusca, Isopoda, have a higher pressure resistance; (2) pressure resistance as a species or genetic property; (3) environmental impact, in which deeper species have a greater pressure resistance; and (4) finally a re-examination of temperature and pressure effects as these relate to deep-sea colonisation.