A coral fall refers to a large section of coral that detaches from its original reef structure and descends into a different marine setting, frequently the deep ocean. Corals are animals, not plants, consisting of numerous tiny polyps that collectively build structures. These polyps secrete calcium carbonate to form hard skeletons, which accumulate over time to create massive underwater formations. This phenomenon introduces hard material into often soft-sediment environments, altering the local seafloor.
How Coral Falls Are Created
The detachment of coral sections can result from powerful natural forces. Intense storms, such as hurricanes or cyclones, generate immense wave energy capable of breaking apart substantial coral structures. Bioerosion, where marine organisms bore into or weaken the coral’s calcium carbonate skeleton, can also compromise the structural integrity of a reef, making it more susceptible to fracturing.
Human activities also contribute to coral falls. Physical damage from ship anchors dragging across reefs or vessel groundings directly dislodges coral colonies. Destructive fishing methods, including bottom trawling or the use of explosives and cyanide, can shatter large coral formations. The laying of submarine communication cables has also been observed to damage ancient coral mounds.
Ecological Role of Coral Falls
Once a coral fall settles, its primary ecological contribution is providing a hard substrate in typically soft-sediment deep-sea environments. The deep-sea floor often consists of mud or sand, which many marine organisms cannot inhabit due to the lack of stable attachment points. These fallen coral structures provide a foundation, enabling colonization by organisms requiring a firm surface.
These sunken coral fragments transform into distinct “islands of biodiversity.” They serve as attachment sites for various deep-sea organisms, including deep-sea corals, sponges, and anemones, which filter food from the water currents. The complex architecture of the fallen coral also provides shelter for mobile species such as deep-sea fish, crabs, and other invertebrates, fostering diverse communities in an otherwise sparse landscape.
Initially, decaying organic tissue on the fallen coral provides a temporary, concentrated food source for scavengers in the deep sea. This nutrient input is significant in the deep ocean, where food resources are generally scarce. Deep-sea corals, unlike their shallow-water counterparts, do not rely on sunlight for nutrition and instead filter feed on organic material such such as marine snow or small plankton. This process enriches the local environment, supporting a unique ecosystem.