Didymosphenia geminata:  Induction of Exopolymer Synthesis in the Nuisance Diatom Didymosphenia geminata  Results in Significant Environmental Impact

(Collaborators: David Domozych & Sarah Spaulding)
SEM of Didymosphenia
Didymosphenia Covered Rock
      In recent years, streams in New Zealand, North America, Europe, and Asia have been disrupted by unprecedented blooms of the freshwater diatom Didymosphenia geminata. (Didymo).  Didymo blooms can cover up to 100% of surfaces with mats of thickness greater than 20 cm, greatly altering physical and biological conditions within streams. These mats are primarily composed of extracellular stalks exuded by D. geminata through an apical porefield. When cells divide within a mat, the stalk bifurcates, the end result of which is an overall branched structure with stalks intercalating and coalescing to form an aggregate “woven fabric” that trap algae, macroinvertebrates, detritus and other stream debris and which, at a macro scale, resemble raw sewage and are quite resistant to degradation. As a first step toward determining what has been “turned on” at the molecular level to result in such massive production of stalks in recent nuisance blooms worldwide, we are investigating details of stalk formation, structure and chemistry. Initial indications are that the sulfated xylogalactan dominated stalks of  D. geminata are very similar to those of the stalked diatoms Cymbella mexicana, Cymbella cistula, and Gomphonema olivaceum. Increased stalk production by these species could result in massive disturbance of freshwater flowing water ecosystems worldwide.


Funding Source:  BioSecurity New Zealand
                   Link:  http://www.biosecurity.govt.nz/didymo             
Collaborators: David Domozych, D.S. Biology Department
Skidmore College, Saratoga Springs, New York
Sarah Spaulding  US Geological Survey & EPA Region 8
Boulder, Colorado

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