Microherbivory

Microherbivory refers to feeding interactions in which very small herbivores consume microscopic photosynthetic organisms, such as algae and cyanobacteria, and associated biofilms. The term is commonly used in microbial and aquatic ecology to describe grazing at scales from single cells to a few millimeters, typically by organisms smaller than a few millimeters in size. Key grazers include protozoa (such as ciliates and heterotrophic flagellates), rotifers, nematodes, and other tiny invertebrates that feed on microalgae or biofilm communities.

This mode of grazing occurs in a variety of settings, particularly in aquatic environments—freshwater lakes, rivers, estuaries, and coastal waters—and in moist soils and on surfaces where biofilms form. Because microalgae and cyanobacteria form the base of many microbial food webs, microherbivory directly links primary production to higher trophic levels and affects community composition, bloom dynamics, and nutrient and carbon cycling.

Researchers study microherbivory using approaches such as dilution experiments to estimate grazing rates, microcosm manipulations, pigment-based and flow cytometry methods to quantify prey communities, and molecular or isotopic tracing to follow carbon flow from algae to grazers. Terminology varies among disciplines; some researchers reserve microherbivory for grazing on algae by protists and small metazoans, while others include all microscopic herbivory on microbial photosynthesizers.

Overall, microherbivory is a key component of microbial food webs, influencing ecosystem productivity, structure, and biogeochemical processes across aquatic and soil environments.