Diatom of the month – August 2016: Didymosphenia geminata
by Luca Marazzi* Many algae are able to form blooms, sometimes releasing dangerous toxins for aquatic organisms and people. Cyanobacteria are most infamous for producing blooms such as those ongoing in Florida's coastal waters , but other algae, including diatoms, can create such vast colonies too. The large ( 100,001-1,000,000 µm 3 ) asymmetrical biraphid Didymosphenia geminata , or colloquially ‘didymo’ is one of them; it attaches to stones in rivers by stalks (made of mucopolysaccharides, long chains of sugar molecules) that can be 1 m long! Didymo is invasive in Argentina, Chile, and New Zealand, where this video was released in 2008 to inform the fishing community that they should clean and dry all their gear to avoid spreading this species to other water bodies. Fig. 1. (top) Didymosphenia geminata ( scalebar = 10 µm ; p hoto by Mart Schmidt ); (bottom) n umerous cells and mucilage stalks from South Boulder Creek (November 2011) - c redit...