Ecological studies on Lake Ototoa with special reference to the copepod Calamoecia lucasi

Abstract

New Zealand is a country richly endowed with lakes of all kinds , yet apart from some pioneering surveys (e.g. Cunningham et al 1953, Flint 1938 , Stout 1969, Jolly 1968) and a few more detailed recent studies (e.g. Fish 1970, Barker 1970, Chapman 1972) very little is known about their detailed limnology or of the biology of the plant and animal species inhabiting them. The South Island is characterised by having many large, deep glacial lakes, and a lesser number of smaller bodies of water, supporting populations of various species of the copepod genus Boeckella. In the North Island there are fewer larger lakes, and most of these are concentrated in the volcanic region near the centre of the Island. Elsewhere smaller bodies of water are more characteristic, and particularly in the far north and along the western coastline the most important and common of these are the sand-dune lakes. In contrast with the South Island, species of Boeckella are relatively less common and in most of the smaller lakes, as well as the majority of the larger central ones their place is taken by the small centropagid Calamoecia lucasi which is usually the dominant zooplankter whenever it occurs. However, only two studies have been made of its biology. Barker (1967) studied some aspects of its seasonal cycle in Lake Pupuke, a eutrophic lake near Auckland, and recently Chapman (1972) has made more extensive investigations of these aspects as well as of population dynamics in Lakes Rotorua and Rotoiti, two large mesotrophic lakes in the centre of the North Island. The study upon which this thesis is based is the first of the ecology of C. lucasi in an oligtrophic lake, and was mainly concerned with the copepod’s seasonal biology, population dynamics and production in one of the northern sand-dune lakes. As well as these aspects, the general limnology of the lake and the cycles of phytoplankton were considered in some detail, not only because of the importance of the environment in determining most limnological cycles, but also because of the lack of knowledge of the general limnology of this important class of New Zealand lake.