Remarkably, the appealing, aesthetical cell shape of desmids very well fits the environment in which they use to occur. Desmids are hardly or not to be expected in polluted waters which, in summer time, grow turbid by mass development of other unicellular algal groups. Reason for that absence is (among other things) that, under nutrient-rich conditions, desmids cannot grow as fast as other algae, so lose in competition. In contrast to that, desmids have to be looked for in clear waters, preferably in those with a luxurious, submerged vegetation of aquatics. Most promising are also small pits and moss-covered shallows in fens and bogs. In general it seems to hold that the more delicate and diversified the structure of (semi)aquatic plant vegetation, the richer and more interesting the desmid flora connected to it. So, desmidiologists are recommended to visit (aquatic) sites of natural beauty!

 

Due to the dependence on clear, relatively nutrient-poor waters, in large parts of the world desmids belong to the seriously threatened groups of organisms. As most of the species only occur at highly specific combinations of habitat variables, they may be considered excellent indicator organisms. As a consequense of their high environmental demands, they are very useful in monitoring conservation value in (semi)aquatic habitats.