macroinfauna

Macroinfauna are benthic invertebrates that dwell within aquatic sediments and are large enough to be collected with standard sediment grabs or cores. Size thresholds vary, but most definitions place them around 0.5 to 1 millimeter in length. They inhabit interstitial spaces in sand, silt, and detrital layers, distinguishing them from epifauna on the sediment surface and from meiofauna that are finer.

Common freshwater macroinfauna include insect larvae (mayflies, stoneflies, caddisflies), oligochaete worms, snails, and small crustaceans; marine macroinfauna include polychaetes, bivalves, amphipods, and tanaids. They occupy most sediments from estuaries to the deep sea, though taxonomic groups vary by environment.

They contribute to decomposition and nutrient cycling, bioturbation, sediment structure, and serve as a major prey base for fishes and invertebrate predators. Community composition, biomass, and diversity respond to sediment grain size, organic matter, dissolved oxygen, salinity, temperature, and pollutants.

Sampling uses grabs or corers, followed by sorting and taxonomic identification. Common metrics include abundance, biomass, and species richness; indices such as the EPT index are used in freshwater systems. Because macroinfauna are sensitive to sediment quality and hypoxia, they are widely used as bioindicators in environmental assessments and monitoring programs.

Management aims to protect sediment quality, reduce contamination, and restore benthic habitats to support diverse macroinfaunal communities.