Bioerosion

Bioerosion describes the erosion of hard ocean substrates by living organisms by a number of mechanisms. Bioerosion can be caused by mollusks, polychaete worms, phoronids, 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 (Clionaidae), bivalves (including "Lithophaga"), sipunculans, polychaetes and phoronids, generating extremely fine sediment of 10 to 100 micrometres. External bioeroders include sea urchins (such as "Diadema") and chitons. These forces in concern result in a great deal of erosion. Sea urchin erosion of calcium carbonate 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 with their well developed jaw muscles, tooth armature, and a pharyngeal mill, which grinds up ingested material into sand-sized particles. Bioerosion of coral reef aragonite by parrotfish can range from 1017.7±186.3 kg/yr (0.41±0.07 m³/yr) for "Chlorurus gibbus" and 23.6±3.4 kg/yr (9.7 10-³±1.3 10-³ m²/yr) for "Chlorurus sordidus" (Bellwood, 1995).

Bioerosion is also well known in the fossil record on shells and hardgrounds (Bromley, 1970), with traces of this activity stretching back well into the Precambrian (Taylor & Wilson, 2003). Macrobioerosion, which produces borings visible to the naked eye, shows two distinct evolutionary radiations. One was in the Middle Ordovician (the Ordovician Bioerosion Revolution; see Wilson & Palmer, 2006) and the other in the Jurassic (see Taylor & Wilson, 2003; Bromley, 2004; Wilson, 2007). Microbioerosion also has a long fossil record and its own radiations (see Glaub & Vogel, 2004; Glaub et al., 2007).

ee also

*Geomorphology:*Biogeomorphology:*Coastal erosion
*Ocean

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External links

* [http://www.wooster.edu/geology/Bioerosion/Bioerosion.html Bioerosion Website at The College of Wooster]