Lophelia - Biology

Biology

Lophelia pertusa is a reef building, deep water coral, which is unusual for its lack of zooxanthellae - the symbiotic algae which lives inside most tropical reef building corals. Lophelia lives between 80 metres (260 ft) and over 3,000 metres (9,800 ft) depth, but most commonly at depths of 200–1,000 metres (660–3,300 ft), where there is no sunlight, and a temperature range from about 4–12 °C (39–54 °F).

As a coral, it represents a colonial organism, which consists of many individuals. New polyps live and build upon the calcium carbonate skeletal remains of previous generations. Living coral ranges in colour from white to orange-red. Unlike most tropical corals, the polyps are not interconnected by living tissue. Radiocarbon dating indicates that some Lophelia reefs in the waters off North Carolina may be 40,000 years old, with individual living coral bushes as much as 1,000 yrs old.

The coral reproduces by budding off new polyps and by producing free-living planktonic larvae which float in the water until they find a suitable surface to attach to and grow on.

Lophelia reefs can grow to 35 m (115 ft) high. The largest recorded Lophelia reef measures 3 km × 35 km (1.9 mi × 22 mi) and lies at a depth of 300–400 m (980–1,300 ft) off the Lofoten Islands, Norway. When this is seen in terms of a growth rate of around 1 mm per year, the great age of these reefs becomes apparent.

Polyps at the end of branches feed by extending their tentacles and straining plankton from the seawater. The spring bloom of phytoplankton and subsequent zooplankton blooms, provide the main source of nutrient input to the deep sea. This rain of dead plankton is visible on photographs of the seabed and stimulates a seasonal cycle of growth and reproduction in Lophelia. This cycle is recorded in patterns of growth, and can be studied to investigate climatic variation in the recent past.