Energetics of planktonic rotifers applied to populations in reservoirs

Abstract

In this thesis field data are given on the seasonal variation in standing crop of rotifers, the egg numbers and the eggs per female in two Thames Valley reservoirs, the Queen Mary and the Queen Elizabeth II. These sites are described and basic physicochemical and seston data given from other sources. The occurrence and seasonal distribution of six rotifer species is described in detail and the relationship between the total standing crop and some physico-chemical characteristics is discussed. The logistic equation is used to calculate the rates of change of some species and these are discussed in relation to temperature, seston, and bacteria. The population dynamics of Keratella quadrata are discussed and birth-rates and production of egg-bearing rotifers calculated using Edmondson's (1960, 1965) method. The production/biomass ratio is then calculated seasonally for egg-bearing rotifers and discussed in relation to current literature. The Q10 relationship is used to assess relative temperature dependence of rotifers in different environments. Respiration rates of several rotifer species given at reservoir temperature, and regressions of respiration/dry weight, respiration/temperature are given together with values, Finally respiration of the reservoir populations is calculated and related to production, indicting a constant relationship throughout the season. Annual assimilation and consumption only are given, assimilation being calculated from Production plus respiration, and a mean assimilation efficiency of 60% being assumed. This was made necessary by inconclusive feeding experiments which are nevertheless recorded in the text. An energy budget for adult Brachionus plicatilis is given as a demonstration of the validity of the methods used, and an indication of what might be achieved in the field situation in the future.