New Zealand Journal of Marine and Freshwater Research abstracts

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Seasonal changes in phytoplankton densities in four North Island lakes, 1973-74

VlVIENNE CASSIE

Botany Division, DSIR, Auckland, New Zealand

Abstract In a 1973-74 survey of preserved phytoplankton from Lakes Rotoiti, Rotoehu, Rotoma and Waikaremoana, 205 algal taxa (including 111 Chlorophyta, 56 Chrysophyta, 17 Cyanophyta, 16 Pyrrhophyta, and 5 Euglenophyta) were found. The greatest number of species was found in Lake Rotoehu, but monthly maxima based on cell counts were usually greater in Lake Rotoiti. A summer bloom of the toxic blue-green alga Aphanizomenon flos-aquae occurred in Lake Rotoehu. Each lake had its own pattern of dominance. Surface and subsurface samples showed marked differences in species composition and abundance. Diatoms were important winter and spring components, with desmids forming conspicuous subordinates. Cemtium hirundinella was prominent in subsurface layers of Lakes Rotoma and Waikaremoana. Compound indices (ratios of number of species of most other algae to that of desmids) point to Lake Rotoehu as extremely eutrophic, to Lake Rotoma as moderately eutrophic, and to Lakes Rotoiti and Waikaremoana as oligotrophic rather than meso- or eutrophic.

N.Z. Journal of Marine and Freshwater Research, 12 (2): 153-66.
Received 13 July 1977; revision received 21 February 1978.

PDF file of entire paper: medium quality (1956K); (scanned from paper original: notes about this process)

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