Bioturbability

Bioturbability is the ability of organisms living in sediments to disturb, rework, and mix the substrate. It results from activities such as burrowing, slicing, and feeding, and from irrigation of burrows by deposit feeders and bioirrigation by sedentary species. Through these processes, bioturbators redistribute particles, modify pore water flow, and change redox conditions, nutrient availability, and sediment structure.

Bioturbation redistributes sediment, enhances mixing across layers, and affects chemical gradients in the subsurface. It alters the penetrative depth of oxygen, the distribution of organic matter, and the accessibility of buried resources, thereby influencing both physical and chemical properties of the habitat.

Ecologists quantify bioturbation using metrics such as mixing depth, the biodiffusion coefficient Db, or clearance rates, often inferred from tracers, dye patches, or radiotracers. Bioturbability is influenced by organism traits (size, feeding mode, locomotion), community composition, sediment properties (grain size, organic matter content, porosity), and environmental conditions (oxygen levels, temperature, hydrodynamics, season). Interactions among species and across life histories can modulate overall reworking rates.

Consequences of bioturbation include enhanced nutrient cycling and carbon remineralization, oxidation of reduced compounds, redistribution of metals and contaminants, and changes to sediment porosity, stability, and habitat structure. In marine, estuarine, and freshwater sediments, key contributors include polychaete worms, crustaceans, bivalves, and oligochaete worms. Understanding bioturbability informs studies of sediment biogeochemistry, ecosystem engineering, and contaminant fate.