Food Supply

Corals that live at depth have little or no access to light, unlike tropical coral reefs they don’t have zooxanthellae to rely on for food: they have to rely on catching prey from the the water column using tractable tentacles, these extend into the direction of current flow (URL 2). Being sessile organisms cold-water corals are found living in places with a strong current flow, this allows suspended organic particles and plankton to be driven to the polyp’s tentacles in aaccordance with the direction of flow (Freiwald et al. 2004). Gorgorian sea fans are often found facing the direction of current flow allowing a large surface area for particles of food to pass through (Figure 5). 

 

Figure 9: Swiftia pallidia a gorgorian sea fan extended in water column (MARLIN URL 5)

  When food particles touch the tentacle stinging nematocyst cells stun the prey with a poison, this immobilises the prey allowing the polyps tentacles to draw the food into its mouth (Url 2) (Figure 6). Lophelia species are generalists in what they eat, they consume anything from chaetognaths and zooplankton to crustaceans (Roberts 2006); this is an advantagous in an environment where food can be sparse.

Figure 6: Extended polyps of Lophelia showing tentacles used in feeding (URL 1)

 Current meters and specialised benthic landers (Figure 7) have been used to investigate the interaction between physical habitat and coral feeding (Davies et al. 2009). It was found that reef colonies were influenced by tidally driven down-wellings of surface water, this brings a food supply and warm nutrient rich water from the surface. Particles were also delivered to the polyps tentacles horizontally in accordance with the direction of water flow (Davies et al. 2009).   

     

Figure 7: Specialised Benthic Lander (Image taken from S.A.M.S Url 3)

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