Phytoplankton Abundance and Primary Production Rates in Two Arctic Ponds

Kalff, Jacob

Phytoplankton abundance and rates of primary production (C'14), were studied at bidaily or tridaily intervals during two summers in two small Alaskan tundra ponds. The phytoplankton, composed largely of unicellular flagellates, numbered between 0.79 and over 100 x 10'6 cells per liter. Rarely did the percentage of cells smaller than 11µ fall below 75% of the total; net phytoplankton were negligible at all times. Annual carbon fixation during 1963 and 1964 was 380 mg/m² (830 mg/m'3) and 820 mg/m² (2,000 mg/m'3) in pond III and 670 mg C/m² and 850 mg/m² in pond II. Daily production, on the basis of a 140-day growing season in 1963 and 1964, averaged 2.6 and 5.9 mg/m² respectively in pond III and 4.8 and 6.1 mg/m² in pond II. Annual production rates are the lowest on record for fresh waters. Phytoplankton abundance and carbon fixation were, during a portion of the study, significantly correlated. Evidence was obtained that many of the phytoplankton were facultative heterotrophs and capable of supplementing autotrophic growth with heterotrophic growth under low light conditions.

Phytoplankton Abundance and Primary Production Rates in Two Arctic Ponds

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