A study of physicochemical conditions, phytoplankton and microcrustacean zooplankton in Wallerawang Reservoir, New South Wales

Wallerawang Reservoir is shallow (mean depth 3.4 m), mesotrophic and lacks persistent summer thermal stratification. During the period from April 1986 to September 1987, the depth-averaged temperature range was 7.6-23.4°C, oxygen 4.8-10.2 mgL^-1, pH 6.7-7.7 and total phosphorus less than 0.01-0.09 mgL^-1.

Dominant phytoplankton genera found in this reservoir (Chroococcus, Asterionella, Attheya, Cyclotella, Stephanodiscus, Melosira and Dinobryon) are generally characteristic of those in other unstratified, mesotrophic lakes of the region; the summer propagation of Melosira is attributed to increased temperature, lack of persistent thermal stratification, and moderately high silica during the period.

The common microcrustacean zooplankton species identified (Bosmina meridionalis, Cenodaphnia sp., Daphnia carinata, Calamoecia lucasi, Boeckella minuta, and Boeckella triarticulata) are ubiquitous in south-eastern Australia.

The gut contents of the dominant microcrustacean zooplankton species reflect the reservoir phytoplankton composition; diatoms are generally better digested than the gelatinous blue-green algae ingested.