Microphytes

Microphytes are small, photosynthetic organisms that inhabit aquatic environments. The term describes microscopic plants and algae, including microalgae and cyanobacteria, that are typically too small to see with the naked eye. They form a contrast with macrophytes, the larger aquatic plants such as reeds and water lilies, and with macroalgae found in some marine ecosystems. Microphytes occur in both freshwater and marine systems and can live as planktonic organisms in the water column or as microphytobenthos on or within the upper sediment layer.

The group is taxonomically diverse, encompassing diatoms, green algae, yellow-green algae, dinoflagellates, and cyanobacteria. Sizes generally range from a few micrometers up to around a millimeter, with numerous species optimized for life in bright, nutrient-rich waters or in nutrient-poor, well-mixed habitats. They may exist as solitary cells, colonies, or motile organisms, and some possess silica cell walls or other distinctive features.

Microphytes play a central ecological role as primary producers, converting light energy into organic matter that fuels aquatic food webs. They contribute substantially to oxygen production and carbon sequestration and are key drivers of nutrient cycling. In many systems, their abundance and composition reflect water quality, light availability, and nutrient status; they can form blooms that influence ecosystem dynamics and, in some contexts, water quality and public health.

Because of their responsiveness to environmental conditions, microphytes are widely studied in limnology and marine biology. Researchers monitor microphyte communities to assess eutrophication, climate-related shifts, and overall ecosystem health, using approaches ranging from microscopy to pigment and flow cytometry analyses.