Influence of Temperature and Light on Rates of Inorganic Nitrogen Transport by Algae in an Arctic Lake

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Whalen, S. C., Alexander, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1984
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Arctic Lake; Phytoplankton
• Online Access: http://dx.doi.org/10.1139/f84-160; http://www.nrcresearchpress.com/doi/pdf/10.1139/f84-160

Nitrogen-15 tracer techniques were used to assess the individual effects of temperature and light on maximum rates of dissolved inorganic nitrogen (DIN) transport by phytoplankton in an arctic lake. Transport rates of NO 3 − and NH 4 + as a function of temperature in the range 3–30 °C were adequately described by second- or third-order polynomial functions. The optimum temperature for DIN transport was greater than the ambient water temperature by as much as 13°; thus, transport at the ambient water temperature averaged only 55–60% of optimum. Mean temperature coefficients [Formula: see text] for NO 3 − and NH 4 + transport in the temperature range >0–15 °C were 2.3 ± 0.5 and 2.4 ± 0.3. The ratio of dark to light-saturated DIN transport (ρ D /ρ L ) was used as a measure of light dependence in maximum rates of DIN transport. Values of ρ D /ρ L [Formula: see text] for NO 3 − and NH 4 + were 0.15 ± 0.09 and 0.41 ± 0.11, indicating a stronger light dependence for NO 3 − than NH 4 + transport. In cases where dark NO 3 − transport was negligible, light was treated as a substrate and the Michaelis–Menten relationship fitted to the data. The half-saturation constant for light intensity in maximum NO 3 − transport ranged from 7 to 29 μE∙m −2 ∙s −1 , which was 6–31% of the photosynthetically active radiation at the lake surface.