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New Zealand Journal of Marine and Freshwater Research abstractsTHE COMPARATIVE LIMNOLOGY OF SOME ZEALAND LAKES 1. PHYSICAL AND CHEMICALV. Hilary JollyWater Board, SydneyAbstract The morphometry, environmental conditions, and some physical and cherhical data are given for twenty-four New Zealand lakes: seven are in the southern jpart of the South Island, the others, excluding Lakes Waikaremoana and Waikajreiti, are in the "thermal region" of the central North Island. These lakes form two separate groups and include the largest and deepest lakes in both islands. The lakes in which stratification was established were found to belong td k i T lk R d Rth class known as warm monomictic. Two lakes, Rotorua and Rotoehu, found to b'e homothermous throughout the year. Open water surface temper- atures did not exceed 23"c in the North Island lakes or 19°c in the South Is and minimum temperatures recorded were 7°c in the northern lakes and the and, 5°c in the southern. In deep lakes the range of temperature was much less: Wakutipu had a range of 16-8.85°c. The disappearance level of a Secchi disc varied from 18 m (Lake Taupcl) to 0.8 m (Lake Rotongaio). The transparency of the water in the glacial and volcanic lakes was comparable to that of similar lakes in other parts of the world. It was found that total ions, measured by the ion-exchange resins reached;high concentrations in lakes fed by thermal waters: Rotomahana 14.32m.e./l. i By concentrationsinlakesfedbythermalwaters:Rotomahana14.32m.e./l.iBycontrast Tikitapu, a seepage lake, had the low concentration of. 0.28m.e./l,j and Wakatipu, a glacial fed lake, a concentration of O.58m.e./1. The pH range was 8.1-5.8, the lowest value being in Tikitapu, a volcanic lake. Slightly lowej- pH values were recorded in the bottom waters of lakes when stratified. Lakes were usually supersaturated with oxygen at the surface, and only a few small pkes showed a hypolimnial deficiency. Silica and phosphate were found in high concentrations in some thermal lakes but nitrogen in the forms measured, was ft>und to be low. !
N.Z. Jl mar. Freshwat. Res. 2: 214-59
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