Physiological ecology of the bloom-forming alga Chrysochromulina breviturrita (Prymnesiophyceae) from lakes influenced by acid precipitation

Many soft-water lakes in northeastern North America subject to acid precipitation have been affected by lakewide odours. These odours are associated with blooms consisting of nearly unialgal populations of the greenish gold alga Chrysochromulina breviturrita Nich. (Prymnesiophyceae). The alga was isolated from Cinder Lake (Ontario) into axenic culture and maintained in a chemically defined medium which corresponds to the chemistry of lakes influenced by acid precipitation. The medium which was developed, Muskoka No. 42, is described in detail and compared with the average water chemistry of affected lakes. The pH tolerance range of C. breviturrita was determined to be 4.0–6.9, with an optimum of 5.5–6.9; the alga was unable to survive above neutrality. Additions of [Formula: see text] at 100 μM or greater completely inhibited growth. Nutritional studies suggested an inability to grow on any nitrogen source other than [Formula: see text]. The alga was also found to require the vitamins B12 and thiamine but not biotin. The present results represent the first published study in which a freshwater member of the Prymnesiophyceae has been maintained axenically in a defined medium.