Bioturbating

Bioturbating, or bioturbation, is the process by which living organisms disturb and rework sediment, leading to the mixing of particles and redistribution of organic matter and pore water. It is carried out by a range of organisms that live within or on sediments, including polychaete worms, bivalves, crustaceans, echinoderms, and some gastropods, as well as soil-dwelling insects in terrestrial settings.

Activities include burrowing, digging, tunneling, ingestion of sediment followed by egestion, casting of feces, and movements that reorient grains. These actions entrain and rework material across small to large scales and can occur in the water-saturated zone or down to several meters in deep-sea environments. Bioturbation often co-occurs with bioirrigation, where burrow networks enhance exchange of water and solutes between pore water and overlying water.

Bioturbating significantly alters sediment physical properties, increasing porosity and permeability, modifying grain size distribution, and altering redox conditions. It enhances nutrient mineralization, carbon and nitrogen cycling, and promotes microbial activity by distributing organic matter. It can influence sediment stability and habitat structure, and affects the fate of pollutants through redistribution and sorption.

The rate and depth of bioturbation depend on organism size, abundance, behavior, temperature, oxygen availability, and sediment type. It is a key factor in paleoenvironments and contemporary ecosystem functioning; assessing bioturbation aids in interpreting sediment cores and managing habitats impacted by dredging or hypoxia.