Infaunisch

Infaunisch is an adjective used in ecology and zoology to describe organisms that live within the sediment of a body of water, i.e., the infauna. The term is used primarily in German-language literature and corresponds to the English term infaunal. Infaunisch organisms inhabit the interior of substrates rather than living on the surface or attached to other structures (epifauna).

Infaunal habitats span marine, estuarine, and freshwater sediments. Infaunal communities can occupy various depths, from the uppermost sediment layer to deeper strata, depending on species and environmental conditions. Common infaunal groups include polychaete worms, burrowing bivalves, amphipods, tanaids, nematodes, and other small invertebrates adapted to life embedded in sediment. These organisms often rely on deposit feeding, filter feeding, or detritivory and frequently construct burrows or tubes.

Ecologically, infauna play a central role in sediment dynamics through bioturbation—the physical reworking of sediment by burrowing and feeding activity. This process affects sediment structure, oxygen penetration, pore-water chemistry, and nutrient cycling, thereby influencing the distribution and behavior of other organisms and overall ecosystem functioning.

Studying infauna involves concentrating sediment samples, often with cores or dredges, followed by sieving and taxonomic identification. Infaunal community patterns serve as indicators of habitat health and sediment conditions, and changes in their composition can reflect pollution, hypoxia, or sedimentary changes.