Protists and their ecological role

Protists are mostly unicellular eukaryotic organisms spanning a wide range of sizes, forms, phylogenetic groups and ecological functions.

The most abundant protists in marine waters are planktonic microalgae: diatoms, dinoflagellates, haptophytes and chlorophytes. They are primary producers which together with cyanobacteria form the basis for life in the ocean.

Heterotrophic protists, which are consumers, decomposers or parasites may also be abundant and important components of marine protist communities.