Comments on the phytoplankton and chemistry of three monomictic lakes in Westland National Park, New Zealand

Abstract

Phytoplankton in lakes of glacial origin was examined once in winter 1933 and occasionally between 1965 and 1975. The predominant algae in Lake Mapourika (114 m deep) were Dinobryon divergens, Staurastrum leptocladum, S. limneticum, Cyclotella spp., and Melosira ambigua. Lake Wombat (a kettlehole, 4.6 m deep) contained a sparse phytoplankton which included M. italica and M. italica subsp. subarctica. Algae characteristic of Lake Matheson (12 m deep) were flagellates (Synura, Cryptomonas, Vacuolaria), Closterium aciculare, Gymnozyga moniliformis, and Aphanizomenon flos-aquae. Differences between phytoplankton in 1933 and 1965–75 reflect the different seasons when samples were collected rather than changes in the trophic level of the water. If measured by their phytoplankton and physical and chemical features, Lakes Mapourika, Wombat, and Matheson were mesotrophic, oligotrophic, and dystrophic respectively.