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

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 (P-m(B)) of 0.46 (+/-0.28) g C g(-1) chlorophyll a (Chl a) h(-1) and a mean alpha(beta) (light-Limitation parameter) of 1.23 (+/-0.56) g C g(-1) Chl a m(2) mol(-1). The saturation irradiance (E-k) ranged from 50 to 196 mu mol 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 alpha(beta) and P-m(B) 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.