Epibiont

An epibiont (from the Ancient Greek meaning living on top of) is an organism that lives on the surface of another living organism. An epibiont is, by definition, harmless to its host and in this sense, the relationship between the two organisms can be considered neutralistic or commensalistic (as opposed to, for example, parasitic, in which case one organism benefits at the expense of the other, or mutualistic, in which both organisms obtain some explicit benefit from their coexistence). Although there is no direct effect of the epibiont to the host, there are often indirect effects resulting from this interaction and change in the surface of the host. This has been found to be especially important to marine organisms and aquatic ecosystems as surface qualities do impact necessary ecological functions such as drag, radiation absorption, nutrient uptake etc. Examples of common epibionts are barnacles, remoras and algae, many of which live on the surfaces of larger marine organisms such as whales, sharks, sea turtles and mangrove trees. The host of the epibiont is typically referred to as the basibiont (living underneath).

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