Microfauna

Microfauna are the smallest tier of animals in soil and aquatic ecosystems. They are typically less than a millimeter long and include protozoa (such as amoebae, flagellates, and ciliates) as well as microscopic metazoans such as nematodes, rotifers, and tardigrades. Definitions of size boundaries vary by field, but microfauna are generally those organisms viewed only with light microscopy.

Ecological role and interactions: Microfauna feed on bacteria, algae, fungi, detritus, and other microscopic organisms, forming a crucial link between microbial producers and larger consumers. Through grazing, they influence microbial community composition and activity, contribute to nutrient mineralization, and aid in the release of nutrients from organic matter. Some microfauna act as detritivores, while others are predators of smaller protists or nematodes. Their short generation times allow rapid responses to environmental changes, helping stabilize microbial ecosystems.

Distribution and habitats: Microfauna inhabit soils, leaf litter, freshwater and marine sediments, and biofilms. They occur in a range of moisture and salinity conditions, with abundance and composition shaped by factors such as moisture, temperature, pH, and organic matter availability.

Life history and reproduction: Protozoa reproduce mainly by asexual division, while other groups such as rotifers can reproduce sexually or asexually (e.g., parthenogenesis in many rotifers). Nematodes and tardigrades exhibit diverse life cycles and strategies, including dormant or resistant stages in some species.

Importance and methods: Microfauna are used as indicators of soil and water quality and as models in ecotoxicology. Study methods include microscopy and culture, supported by molecular approaches such as DNA barcoding and metabarcoding, alongside extraction techniques designed to isolate these tiny organisms from environmental samples.