Carbon fixation by phytoplankton in high Arctic lakes: Implications of low temperature for photosynthesis

Abstract

Photosynthesis vs. irradiance relationships were determined for phytoplankton communities from seven lakes in the Canadian high Arctic, including ultraoligotrophic Char Lake, nutrient‐enriched Meretta Lake, and two meromictic lakes. The derived photosynthetic parameters were low for all samples, with a mean (±SD) light‐saturated photosynthetic rate (PmB) of 0.46 (±0.28) g C g−1 chlorophyll a (Chl a)h−1 and a mean αB(light‐limitation parameter) of 1.23 (±0.56) g C g−1 Chl a m2 mol−1. The saturation irradiance (EΚ) ranged from 50 to 196 μmol quanta m−2 s−1 and was positively correlated with mean irradiance for the water column. Quantum yields for photosynthesis in the Arctic lake phytoplankton were also low (mostly <10 mmol C mol−1 quanta). An intersystem comparison of αB and PmB values with literature data for algae from other cold environments showed that the photosynthetic parameters for phytoplankton in Arctic and Antarctic lakes are three‐ to sixfold lower than for marine algae, ice algae, and cultures over the same low‐temperature range. This may be the result of more severe nutrient stress in high latitude lakes relative to polar marine environments and to the persistence of nonactive pigments in cold freshwaters.