algal bloom




Examples of Woronichinia

woronichinia (image 5)

400X total magnification; 10 μm scale bar.

woronichinia (image 1)

400X total magnification; 10 μm scale bar.

woronichinia (image 4)

A colony of cells, surrounded by solitary cells extruded from colonies as part of the colony reproduction cycle. 400X total magnification.


Spherical to irregularly oval colonies, often composed of subcolonies, enveloped by diffuse, colorless mucilage. Colonies contain a system of unbranched mucilaginous stalks, radiating outward from the colony center; cells are held at the ends of the stalks, sometimes enveloped by the stalks; stalks densely packed, usually as wide as the cells, and sometimes diffuse near the colony center. Cells radially arranged in a peripheral layer (see third and fourth images to the right); may be very densely arranged in older colonies. Cells usually slightly elongate, widely oval, or obovoid (egg-shaped, with the narrower end oriented towards the colony center), only rarely nearly spherical in shape; (2.5)-7 x 1-4(5) μm in size; with aerotopes in some species; pale blue-green, olive-green, or reddish (however, as with Microcystis, aerotopes can give cells an overall brownish color). Solitary cells may be spontaneously liberated from colonies, via expulsion, as part of the colony reproduction cycle (see last image to the right).


Species with aerotopes are capable of forming surface blooms in mesotrophic to eutrophic waterbodies; W. naegeliana contains aerotopes and is common in the plankton of lakes throughout temperate regions. Non-planktic species may be epipelic among benthic algae and plants; benthic or metaphytic in oligotrophic ponds, swamps, pools, or lakes.


  • Johansen, J. R., & Komárek, J. (2015). Coccoid Cyanobacteria. In J. D. Wehr, R. G. Sheath, & J. P. Kociolek (Eds.), Freshwater Algae of North America: Ecology and Classification (2nd ed., pp. 91-101). Waltham, MA: Elsevier.
  • Komárek, J. & Anagnostidis, K. (2008). Cyanoprokaryota-1. Teil/Part 1: Chroococcales. In H. Ettl, G. Gärtner, H. Heynig, & D. Mollenhauer (Eds.), Süßwasserflora von Mitteleuropa (Vol. 19/1, pp. 207-215). Heidelberg, Germany: Spektrum.