Development and Use of an Aquatic Micro‐Ecosystem as a Test System for Toxic Substances. Properties of an Aquatic Micro‐Ecosystem IV

Abstract

Experiments were performed using several modifications of a micro-ecosystem made up of three subsystems connected by a unidirectional flow of recirculating water. The three subsystems represent roughly the trophic levels of autot>rophs (algae), herbivores (Daphnia magna), and decomposers (sandfilter with bacteria). The particle concentration was determined weekly, using a Coulter Counter, and the Daphnia population was counted. A t regular intervals, the species composit.ion of the algae was determined. The changes in t.he algal concentration and Dapimici popuhtion are described, and the different modifications are discussed.I n several micro-ecosystems, the herbicide dichlobenil was introduced once or several tiniest and in one micro-ecosystem, the herbicide diuron was added. The response of the micro-ecosystems is discussed. For the periods without a toxic substance present, a normal operating range is suggested in relation to which the response of the systems to the introduced herbicide is discussed.Besides the separate analysis of the data, the algal concentrations and the Daphnia numbers were correlated to each other. This was done by regression analysis and a,ccording t o a dynamic system approach. I n both cases, the effect of herbicides was better discerned than in the separate analysis of the data. I n the dynamic systems approach, a normalized ecosystem strain was defined a s a parameter to measure effects of stress on the ecosystem level.

Effects of Cu+2 and pH on the fitness of Ceriodaphnia dubia (Richard 1894) (Crustacea, Cladocera) in microcosm experiments

“…The extreme complexity of aquatic ecosystems has led many researchers to undertake population and community level studies at microcosm and mesocosm spatial Correspondence to: A. M. Gagneten; e-mail: amgagnet@fhuc.unl. edu.ar. scales, in which it is possible to maintain experimental conditions under control, so as to determine causeeffect relationships among the organisms in the community (Biesinger and Christensen, 1972;Chi-Hsiang and Armitage, 1980;Kersting, 1984;Baudo, 1987;Soto, 1989;Gliwicz, 1990;Niederlehner et al, 1990;Cowgill and Milazo, 1991;Gliwicz and Lampert, 1993;Gonzalez and Frost, 1996;Luoma, 1996). Recently, studies have been carried out with the purpose of determining the effects of a diverse range of contaminants on the fitness of aquatic biota, as well as to determine the incidence of these effects on the distribution and abundance of organisms, and in the evolution of possible physiological adaptations (Forbes and Calow, 1996;Calow and Forbes, 1998).…”

Validation of microbial community structure and ecological functional parameters in an aquatic microcosm designed for testing genetically engineered microorganisms

“…The importance of physical scaling of water turnover, turbulence, and incident radiation are critical to the ability of microcosms to simulate a marine ecosystem, as shown by Perez et al [33]. The use of a three-compartment model, where phytoplankton and herbivore zooplankton are physically separated, increases the stability of the model and facilitates long-term studies, because unnatural fluctuations of the populations that are due to zooplankton overgrazing are prevented [17]. .…”