New Zealand Journal of Marine and Freshwater Research abstracts

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Phytoplankton in six hydroelectric lakes on the Waikato River, New Zealand, 1970-72

C. H. D. Magadza

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

Abstract Phytoplankton were studied in six lakes (Aratiatia, Ohakuri, Atiamuri, Whakamaru, Waipapa, and Karapiro) on the Waikato River, New Zealand, 1970-72. The standing crop of phytoplankton showed a progressive increase as the Waikato River flowed northwards from Lake Taupo through eight dams to Lake Karapiro. Ths dominant algal species was Melosira distans (Ehrenb.) Ktitz, with M. granulata var. angustissima O. Mull, and Asterionella for-mosa Hass. as the subdqminants. The increase in standing crop of the phytoplankton was associated with increase in the nitrogen and phosphorus loading on the river. The role of M. distans, M. granulata var. angustissima, and Asterionella formosa as indicators of trophic status of lakes is discussed. Application of the Shannon-Weaver index of diversity showed that the index was very sensitive to changes in the relative abundance of M. distans and M. data var. angustissima, but was insensitive to changes in the relative abundance of the If the phytoplankton species. The analysis of trend showed a tendency for the algal ling crop to increase during the study period. This trend was most noticeable in those lakes with high nutrient inputs. A comparison of the chlorophyll standing crop value found in Lake Ohakuri to previously reported values confirmed this trend and showed that there had been a recent change in the algal species composition of the lake.

N.Z. Journal of Marine and Freshwater Research 12 (1) : 29-40.
Received 9 September 1975; revision received 10 June 1977.

PDF file of entire paper: medium quality (980K); (scanned from paper original: notes about this process)

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