Infauna

Infauna refers to the animals that live within the substrate of a body of water or the seafloor. These organisms burrow, tunnel, or reside within the sediment, including sand, mud, or gravel, rather than on the surface. They play a critical role in bioturbation, nutrient cycling, and the overall health and structure of aquatic ecosystems. Their lifestyles often necessitate adaptations to low light, varying oxygen levels, and the challenges of moving through or remaining within their subterranean habitats. Studying infauna provides valuable insights into sediment composition, water quality, and environmental impacts.

Infauna meaning with examples

• Marine worms, like polychaetes, are a common example of infauna. They burrow through the seabed, ingesting sediment and creating tunnels that oxygenate the surrounding environment. Their presence and abundance are often used as indicators of the overall health of the seafloor ecosystem. Their filter-feeding habits also assist with water quality, keeping the water clean from pollutants.
• Clams and other bivalves are considered infauna. They bury themselves in the sand or mud, extending siphons to filter feed on organic matter in the water. Their shells provide protection from predators. They are greatly affected by pollution. Their burrows and feeding activities contribute to sediment mixing, improving nutrient availability and increasing the rate of decomposition.
• Certain species of crustaceans also live as infauna, particularly burrowing shrimp and some amphipods. These creatures create extensive tunnel systems in the sediment, providing habitat for other organisms and influencing the physical structure of the substrate. Their movements oxygenate the sediment and assist in the breakdown of organic materials. They provide food for other creatures.
• Some sea urchins, though often associated with surface dwelling, also exhibit infaunal behaviour, partially burrowing into the sediment to find food or escape predators. Their grazing habits significantly impact the structure of benthic communities. Their burrowing activities further improve the aeration of the surrounding marine sediment, stimulating nutrient cycling.