Ecological and nutritional studies on Dinobryon Ehrenb.: Seasonal periodicity and the phosphate toxicity problem

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Abstract
Although field studies show inverse correlations between concentrations of dissolved phosphate and abundances of Dinobryon, phosphorus is not toxic even at high concentrations. Species abundance in water of low phosphate concentration may be traced instead to effective mechanisms for phosphate uptake which allow the cells to thrive at low ambient levels of PO4‐P. Half‐saturation constants of less than 0.5 µM PO4‐P can be demonstrated both in laboratory cultures and in situ in lakes. Ambient concentrations of potassium ion can be toxic to a variety of species of Dinobryon and thus can limit both their geographical and seasonal occurrence. Ammonium serves as a better nitrogen source than does nitrate, an observation supported by both field and laboratory data. At least one species, Dinobryon sertularia, is physiologically limited to water temperatures below 20°C.