Assessment of secondary production of Naididae (Oligochaeta): an example from a North German lake

Abstract

The annual production of the Naididae Chaetogaster diastrophus, Nais spp., and Stylaria lacustris inhabiting the aufwuchs on reed stems in eutrophic Lake Belau (northern Germany) was estimated. For this purpose, field biomass data taken at biweekly intervals were combined with data on growth potentials of Naididae. From biomass doubling times of laboratory cultures (own and literature) at different temperatures, relationships between temperature and instantaneous growth rate r were developed. Based on these functions, the temperature conditions in Lake Belau over 1993 were assessed to allow for the development of 66 generations of C. diastrophus, 42 of Nais spp. and 30 of S. lacustris, respectively. Corresponding annual turnover rates (P/B) are 108 for C. diastrophus, 96 for Nais spp., and 78 for S. lacustris, respectively. However, field data from Lake Belau provide evidence for a food limitation of naidid populations after their abundance peaks. Thus, Naididae can probably not realize their growth potentials over the whole season. Different scenarios of naidid production for various assumed food-limited growth rates are calculated. Under the assumption that no further production occurs once peak densities are reached, annual production on the reed stems in 1993 amounted to 287 μg dry mass cm⁻² a⁻¹. This value represents only 21% of the potential production of 1342 μg dry mass cm⁻² a⁻¹. The true production of aufwuchs-associated Naididae in Lake Belau lies between these values.