Light, nutrient requirements, and optimum N:P ratios in unicellular algae
1988
Rhee, G.Y. (Wadsworth Center for Laboratories and Research and School of Public Health Sciences, State University of New York at Albany, Albany (USA))
Nutrient requirement increased under subsaturating light conditions. There was a compensatory relationship between light and nutrient requirements within a certain limit. Therefore, increased amounts of nutrients could compensate for suboptimal light and vice versa. Nutrient requirements also varied under fluctuating light at high frequencies; the requirement for P decreases whereas that for N increases. The relative requirement for N and P, or the optimum N:P ratio, increased under subsaturating light, primarily as a result of an increased cell N requirement. The optimum N:P ratio also increased under high-frequency fluctuating light. This increase was due to decreased requirements for P and increased requirements for N. These light-induced variations in the optimum N:P ratio may modify the degree of nutrient limitation or kind of limiting nutrients vertically for phytoplankton in the euphotic zone. The combined effects of simultaneous limitation of light and nutrients were greater than the sum of individual effects. Thus, their interaction was not of threshold or either-or type. It was neither additive nor multiplicative
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