Alga bloom, composed of Eudorina green alga colonies and Synura golden alga colonies. In early spring Synura, a brownish colony formed by variable numbers of cells held together at the posterior ends, often forms algal blooms, in this case together with Eudorina colonies, each globular colony formed by 16 or 32 biflagellate cells. Microscopic contrast technique : Differential interference contrast. Magnification 90x when printed 10 centimetres wide.