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New Zealand Journal of Marine and Freshwater Research abstracts

Algal populations and characteristics of oxygen exchange of effluent samples from a facultative oxidation pond

D. E. IRVING*
F. I. DROMGOOLE

Department of Botany University of Auckland Private Bag, Auckland New Zealand

Abstract Algal populations in a facultative oxidation pond were monitored over a 12 month period. The relationships between cell counts of individual species and characteristics of oxygen exchange, determined from changes in dissolved oxygen concentration in response to varying light flux density, were investigated by correlation analysis. These measurements were made in the laboratory at a constant temperature (15°C). Microalgae (Chlorella spp.) usually made up at least 80% of the total cell numbers, whereas Euglena acus, E. gracilis, and Ankistrodesmus falcatus var. acicularis separately made up less than 10% of the total counts. However, when cell volumes were considered, E. acus usually made the greatest contribution, and this species accounted for 86% (=r2) of the variation in total cell volume. The detectable pigment concentration in the water was closely related to the numbers of E. acus present (r=0.81, P < 0.001) but not to the numbers of microalgae (r = 0.00). Cell counts of E. acus were highly correlated with the light saturated rate of net oxygen production (Pn max) and to the rate under limiting light supply (9) because of the high detectable pigment contribution from this species. It was calculated that E. acus contributed, on average, about 44% of the total rate of net oxygen production, whereas the proportion attributed to the microalgae was 8%.

Keywords oxidation pond; oxygen exchange; pigment; microalgae; Chlorella spp.; Euglena acus; E. gracilis; Ankistrodesmus falcatus var. acicularis; sewage

New Zealand Journal of Marine and Freshwater Research, 1986, Vol. 20: 9-16 Received 18 May 1984; accepted 17 June 1985

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