Soil protists — the invisible engines of ecosystems

Exploring protist diversity and habitat

• Diversity: As eukaryotes, protists are more closely related to plants, animals and fungi than to bacteria (prokaryotes, cells without nuclei). Protists comprise a very large variety of eukaryotes with markedly different body forms and lifestyles.
• Habitat: Protists are ubiquitous in soils, from the Arctic to tropical regions, and tolerate a wide range of soil acidity, salinity and temperature. Soil protists inhabit the thin water film surrounding soil particles. This microhabitat connects them to roots, other microorganisms, and larger soil fauna, forming an invisible but highly dynamic soil food web. The composition of protist communities varies with habitat, making them useful environmental indicators. Soil protists show clear biogeographical clustering. Parasitic protists are most abundant in tropical forests. Phototrophic protists (microalgae) are more common in arid grasslands. Predatory consumers are frequent in temperate croplands and forests. Global patterns of protist community composition are strongly shaped by annual precipitation.
• Surprisingly, even cities can be hotspots for protist diversity! Recent studies show that urban greenspaces host higher protist diversity than nearby agricultural fields or forests, likely due to varied microhabitats and nutrient inputs (e.g. Shangguan et al., 2024; Sun et al., 2025).