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Bioerosion
From Wikipedia, the free encyclopedia
Bioerosion describes the erosion of hard ocean substrates by living organisms by a number of mechanisms. Bioerosion can be caused by mollusks, polychaete worms, sponges, crustaceans, echinoids, and fish. It can occur on coastlines, on coral reefs, and on ships. Mechanisms of bioerosion include biotic boring, drilling, rasping, and scraping.
Bioerosion of coral reefs generates the fine and white coral sand characteristic of tropical islands. The coral is converted to sand by internal bioeroders such as algae, fungi, bacteria (microborers) and sponges (Clionidae), bivalves (Lithophaga), sipunculans (Aspidosiphon), polychaetes (Eunicidae), generating extremely fine sediment of 10 to 100 micrometres. External bioeroders include urchins (Diadema) and chitons (Acanthopleura). These forces in concern result in a great deal of erosion. Sea urchin erosion of CaCO3 has been reported in some reefs at annual rates exceeding 20 kg/m².
Fish also erode coral while eating algae. Parrotfish cause a great deal of bioerosion, due to their well developed jaw muscle and tooth armature, and a pharyngeal mill, which grinds up ingested material into sand-sized particles. Bioerosion of reef calcium carbonate by parrotfish can range from 1017.7±186.3 kg yr-¹ (0.41±0.07 m³ yr-¹) for Chlorurus gibbus and 23.6±3.4 kg yr-¹ (9.7 10-³±1.3 10-³ m²yr-¹) for Chlorurus sordidus (Bellwood, 1995).
Belwood, D. R. (1995). Direct estimate of bioerosion by two parrotfish species, Chlorurus gibbus and C. sordidus, on the Great Barrier Reef, Australia. Marine Biology, 121(3), 419-429. [1]