Distribution Factors

There is a lack of knowledge on the distribution of cold water coral reefs: it is limited by geographic area and available resources (Rogers 2004). All cold-water corals have similar requirements determining where they are distributed. Firstly the larvae needs a hard surface to attach to this could be either exposed rock or a piece of dead coral and secondly it has to be situated in an area with a permanent water flow or episodically strong current (Rogers 2004). Water flow is vital for food supply, egg dispersal, reproduction, removal of waste and keeping the coral surface sediment free. As a result corals are typically found on continental shelf slopes or sea mount summits where they are exposed to strong currents and high organic sediment suspension (Rogers 2004).  Corals favour pinnacles of rock where it is easy to extend tentacles into the current flow. 

Distribution of cold-water corals found in shallower waters are effected by biotic competition with other animals eg: Crinoid sponges.  They tend to occur in environments with stable physical conditions with very little variation in temperature and salinity 32-39 psu (Freiwald et al 2004). At depth they can occur in low oxygen and higher salinity’s due to the presence of bacteria (Rogers 2004). Alkalinity of the water also effects distribution due to the availability of Argonite which is important in the formation of a calcium carbonate skeletons (Roberts et al. 2009). Figure 10 shows the global distribution of cold-water corals reefs.

Figure 10: Global Distribution of Reef Framework Forming Corals (Roberts et al. 2006)

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