Primary production in Lakes Rotorua, Rerewhakaaitu, and Rotoiti, North Island, New Zealand, 1973-78

Primary production was measured by the carbon 14 method for 4.5 years in Lake Rotorua (1974-78) and for 1 year in Lakes Rerewhakaaitu and Rotoiti. The results from laboratory incubations of water samples were combined with chlorophyll a, extinction coefficient, and isolation data using a computer model developed by Fee. The average annual daily production rates of carbon were: Lake Rotorua, 2.3 grams per square metre per day (gsmd) (range 0.70-5.5 gsmd); Lake Rerewhakaaitu, 2.2 gsmd (range 0.66-4.00 gsmd); and Lake Rotoiti, 1.1 gsmd (range 0.32-2.46 gsmd). The seasonal patterns of production are different for each lake. Lake Rotorua has maxima in summer or early autumn, Lake Rerewhakaaitu in autumn, and Lake Rotoiti in winter. In Lake Rotorua there was considerable variation from year to year in the timing and intensity of the maxima. The year-to-year differences between quarterly and between the annual production totals are small considering the experimental errors involved in the study of large lakes