Relationships between zooplankton abundance and trophic state in seven New Zealand lakes

Abstract

The zooplankton communities of seven Rotorua, New Zealand, lakes of different trophic status were studied in 1977-78. They were generally dominated by the calanoid copepod, Calamoecia lucasi. Bosmina meridionalis occurred in all the lakes and Ceriodaphnia duhia in most. Only small numbers of Macroc~~clops alhidus ever occurred. Rotifers were not studied in detail. Community composition was similar to that in other northern New Zealand lakes. No well defined patterns of seasonal change in abundance were found and the timing of changes, which were of low magnitude, was different in each lake. Clutch sizes in all species were small. Calamoecia population parameters were analysed using multivariate methods and shown to be related to lake trophic level. Population densities were higher in more productive lakes whereas breeding levels were inversely related to indices of trophic status and population abundance. It is suggested that the populations, as in other northern New Zealand lakes, are food-limited, probably as a consequence of a lack of marked climatic seasonality and the absence of major predation pressures. Groupings of the lakes based on the Calamoecia data are in general agreement with those derived from parallel studies of water chemistry, phytoplankton and macrobenthos.

New Zealand lakes research, 1967–91

“…(Chapman et aL 1975;Green 1976;Burns & Mitchell 1980;Forsyth & McCallum 1980;Chapman et al 1981;Stout 1984). In eutrophic Lake Okaro, rotifers and ciliates show patterns of diel vertical migration that change seasonally, probably in response to development and breakdown of an oxycline (Forsyth & James 1991).…”

Crustacean zooplankton communities in a New Zealand lake during four decades of trophic change

“…Calamoecia and the cladocerans breed throughout the year and ephippial Bosmina and Ceriodaphnia are very rarely found (Chapman 1973;Chapman etal. 1981;Chapman et al 1985). We suggest that because of their effects on nutrient and food resource availability and distribution, stochastic events such as storms and the frequency of heavy rainfalls are more important than the general climatic regime in determining the annual cycles in abundance of zooplankters in northern New Zealand lakes.…”

“…Before this B. meridionalis and C. dubia were The assemblage in Lake Rotorua is typical of those in many New Zealand lakes (Chapman & Green 1987). There is a single calanoid copepod, the small (adult body length c. 0.9 mm) Calamoecia lucasi, which is widely distributed in the North Island (Chapman & Green 1987) and prominent in the zooplankton of all lakes in the Rotorua area (Chapman et al 1985). The only cyclopoid is the primarily benthic Macrocyclops cf.…”

“…Abundance cycles also differed between Lakes Rotorua and adjacent Rotoiti in 1967-69 (Chapman 1973 (Chapman et al 1985). These lakes were sampled at monthly intervals so that some changes, especially of the shorter-lived cladocerans, would have been missed but they give a general picture of seasonal changes.…”

“…The major peaks in early summer found in three of the Lake Rotorua study years occurred in Lake Okaro only. Ceriodaphnia typically has only brief periods of abundance in New Zealand lakes and for much of the year may be recorded only rarely or in very low numbers (Chapman et al 1985;Chapman & Green 1987;Greenwood 1993 (RKK = Lake Rotokakahi, RTM = Lake Rotoma, TKT = Lake Tikitapu, NGP = Lake Ngapouri, OKO = Lake Okaro, OKK = Lake Okareka, OKT = Lake Okataina.) Data re-plotted from Chapman et al (1985).…”