Species Focus - Microalgae and Protozoa

Microscopic plants (microalgae) and animals (protozoa) form the focus this month. In a recent Cofnod workshop, participants were introduced to the highly diverse and beautiful microalgae and protozoans, as well as micrometazoa, that occupy our freshwaters but remain unknown organisms to most people. The microorganisms, most of which are smaller than 50 microns, form the basis of the food chain that eventually, through invertebrates and reptiles, leads to birds and mammals.

The microalgae are, in general, non-flowering aquatic plants that are autotrophic (generate their own carbohydrate supply using photosynthesis) and are classified on their chlorophyl type. Protozoans do not contain chlorophyl and must search for their food material (heterotrophic). The microalgae are classified into ten phyla based on their chlorophyl type, morphology and motility. Except for the “blue-green” algae (cyanobacteria are prokaryotes), microalgae contain a nucleus (eukaryotes). Although plants are generally considered to be immobile, most microalgae can move to areas of illumination using flagella or by extruding a mucous jet. Most microalgae have a rigid cellulose cell wall, except for the diatoms which have a box-like cell wall composed of silica. Three groups of protozoans are recognised based on their motility and include forms covered with cilia (ciliates), forms with one or two tails (flagellates) and those that creep using pseudopodia (amoeboids).

Their sensitivity to minor environmental changes makes them ideal monitors of local and regional changes. Some are sensitive to levels of dissolved organic material while others are intolerant of elevated phosphate and nitrate levels. Diatoms are currently used to monitor influxes of fertiliser runoff into rivers from fields, and cyanobacteria, as algal blooms, also provide warnings of dissolved nutrient and/or oxygen imbalance in lakes. A sampling and analytical programme is in progress with over 50 locations sampled in North Wales with the identified microalgae and protozoa entered into the Cofnod database to establish a base-level understanding of their present distribution. In a recent Cofnod-sponsored workshop, 12 participants were introduced to this fascinating microworld and will hopefully start contributing to the Cofnod ORS or the LERC Wales App.