infaunische

Infaunische, or infaunal, describes organisms that spend all or part of their life cycle within the substrate of a sediment or soil, rather than on its surface. The term is widely used in marine ecology and soil biology to characterize animals living inside the seabed, river sediments, or terrestrial soils. In German usage, infaunisch is the related adjective.

Infauna inhabit burrows, tubes, or cavities within the sediment (endobenthic). In marine environments they include polychaete worms, burrowing bivalves, crustaceans, and some echinoderms. In terrestrial and freshwater systems, earthworms, nematodes, and a variety of other invertebrates form common infaunal communities. These organisms may be visible as aggregates or operate as solitary burrowers.

Ecologically, infauna perform bioturbation—the reworking of sediment through movement and feeding. This activity aerates sediments, enhances oxygen penetration, redistributes organic matter, and facilitates nutrient cycling. Infaunal communities influence sediment structure, porosity, and the habitat available to other organisms, thereby shaping overall ecosystem function and productivity.

Terminology distinguishes infauna from epifauna (organisms living on the surface) and from meiofauna (very small organisms living between sediment grains). Infauna range from larger macrofauna to smaller meiofauna and are often studied using sediment cores, grabs, or box corers to assess habitat quality and environmental conditions.

Because of their roles in biogeochemical processes and their sensitivity to disturbance, infaunal communities serve as indicators of environmental health and are used in ecological and paleontological reconstructions of past environments.