Epibionts

An epibiont is an organism that lives on the surface of another living organism, the host. Epibionts are found in both aquatic and terrestrial ecosystems and include a wide range of life forms, such as algae, barnacles, bryozoans, diatoms, small invertebrates, and microbial communities. They attach to surfaces like skin, fur, shells, or carapaces, often using adhesive secretions or specialized structures.

The relationship between epibiont and host is typically commensal or neutral, but it can be parasitic or mutualistic depending on the species and circumstances. Epibionts influence the host in various ways, including changes to surface texture and hydrodynamics, added weight or drag, and potential impacts on disease dynamics or camouflage. Colonization usually begins with free-living larvae or spores that settle on a suitable surface, followed by growth and community succession that can produce complex biofilms or fouling assemblages.

Ecologically, epibionts contribute to habitat complexity, create microhabitats for other organisms, and alter movement or feeding of the host. They are also important in applied contexts: biofouling on ships and underwater structures can affect performance and maintenance, while epibiont communities can serve as indicators of environmental conditions and ecosystem health.

Taxonomically, epibionts span multiple groups, from macroorganisms like barnacles and algae to microalgae and bacteria. The term emphasizes their external association with the host rather than an internal or deeply integrated relationship.