Feeding and Nutrition

Lophelia pertusa polyps used for feeding

Lophelia pertusa polyps used for capturing prey. google images.

Tropical coral reefs contain a symbiotic algae called zooxanthellae, this algae captures light penetrating through the water column which is then used as an energy source for the coral. Cold-water corals are known as azooxanthellates, they do not contain zooxanthellae so they have to rely on alternative methods to capture their prey. It has been suggested that cold-water corals use their polyp tentacles to capture particles suspended in the surrounding water (Freiwald et al. 2004) and zooplankton up to 2cm in size (Freiwald 2002; Mortensen 2001). Corals found in areas containing hydrocarbon seeps are thought to gain nutrients from the bacteria found in the seeps (Howland et al. 1997).

As cold water corals are fixed in one place or ‘sessile’ they have to rely on surface and deep ocean currents to bring food to them. Many corals are found in areas with complex topography such as on slopes, on seamounts and in trenches (Flach & Thomsen 1998; Gage et al. 2000; Hughes & Gage 2004) so currents are an important factor in the transportation of food to these remote areas. Davies et al (2009) talks about how internal waves have been thought to carry suspended particles and plankton through the water column, these waves are seen to play a role in supplying food and enhancing growth in cold-water corals. This was proved by Frederiksen et al (1992) where studies carried out in the Faroe Islands showed that the abundance of the Scleractinian Lophelia pertusa increased in areas with internal waves. Without currents and internal waves nutrients and food would not available to corals located at depth and in areas of complex topography.

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