Dissolved oxygen

Oxygen concentration also appears to have an impact on influencing the distribution of L. pertusa. Oxygen is required for respiration, L. pertusa extracts O2 from the water in a dissolved state. Freiwald (2003) found that most L. pertusa locations in the NE Atlantic occurred in zones of low dissolved oxygen of 3-5ml/l, whilst other geographic locations found L. pertusa between 2.6 and 6.7ml/l (Scheroder, 2002; Wisshak et al., 2005). L. pertusa can regulate its oxygen consumption over a range of dissolved O2 concentrations, possibly by altering the surface area of the polyps to regulate gas exchange (Dodds et al., 2007). Furthermore it appears L. pertusa can survive short term periods of anoxia by using anaerobic mechanisms and switching to anaerobic respiration after 48-96 hour exposures in hypoxia conditions (Dodds et al., 2007). However the metabolism of L. pertusa in water below 3.26 ml/l of dissolved oxygen is thought to be too high to maintain over a longer period of time (Dodds et al., 2007). Furthermore Brooke and Young (2009) observed low growth rates at the Viosca Knoll, Gulf of Mexico, where relatively low oxygen levels were present in otherwise optimal conditions (Davies et al., 2010). Fink et al., (2012) observed a temporary coral extinction from cores within reefs in the Mediterranean Sea when oxygenation of the bottom waters was reduced between 11,000-6,000 years ago (fig 9). Overall it appears L. pertusa can withstand fluctuations of O2 concentrations, however survivorship over long term exposures of low oxygen concentration is likely to be effected. The oceanic suboxia volume is projected to increase by as much as 50% by 2100 (Oschlies et al., 2008), indicating it may have an important role to play in the future of habitat suitability of cold-water corals.

Fig. 9. A schematic depicting different conditions in the Mediterranean Sea. A) Well ventilated modern day system with coral growth. B) Poor ventilation due to weak Adriatic Deep Water (AdDW) flow resulting in extended dysoxia and anoxia zones leading to the demise of coral. Fink et al., 2012.

Fig. 9. A schematic depicting different conditions in the Mediterranean Sea. A) Well ventilated modern day system with coral growth. B) Poor ventilation due to weak Adriatic Deep Water (AdDW) flow resulting in extended dysoxia and anoxia zones leading to the demise of coral. Fink et al., 2012.

 

 

 

 

 

 

 

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