STP988: Chemically Induced Community Responses in a Compartmentalized Microcosm Assessed by Multidimensional State Space Transitions

    de Zwart, D
    Research ecotoxicologist and ecologist, Laboratory for Ecotoxicology, Environmental Chemistry, and Drinking Water, National Institute of Public Health and Environmental Hygiene, Bilthoven,

    Langstraat, H
    Research ecotoxicologist and ecologist, Laboratory for Ecotoxicology, Environmental Chemistry, and Drinking Water, National Institute of Public Health and Environmental Hygiene, Bilthoven,

    Pages: 13    Published: Jan 1988


    Abstract

    A test has been developed to assess the chemically induced disturbance produced by interactions between functionally different groups of organisms. Algae, daphnids, polyps, and decomposer organisms—representing adjacent trophic levels—were housed in separate containers. Water containing algae and nutrients was circulated through the compartments. In some experiments, according to a realistic scheme based on empirically derived knowledge of the needs of the individual populations, an interactive relationship was maintained between standing stock parameters and the circulation rate and between predation on daphnids and feeding by polyps. Since, for each compartment, input and output fluxes were experimentally determined, the rates of processes could be calculated. One of the major drawbacks of the small volume (14 L) of the microcosm was the necessity for nondestructive or micro methods of analysis.

    In the experiments presented in this paper, only the standing stock parameters for the algae, daphnids, and polyps, and occasionally the pH, were measured with enough adequacy to construct a multivariate “normal operating range” (95% confidence interval) out of the rather long time series of preexpositional data. This “normal operating range” was used as a reference state for the changes after perturbation.

    Perturbation of the model ecosystem with a toxic chemical (in this case, 2,4-dichloroaniline) was followed by a gradual displacement outside the normal operating range. All four systems tested showed a temporary or permanent shift in the three-dimensional state space outside the normal operating confinement within ten days after the addition of 0.010 mg L−1 of the toxicant, whereas the lowest “no-observed-toxic-effect level,” determined by semichronic tests on the susceptibility, individually, of populations of green algae, daphnids, and polyps, was slightly higher. (For Daphnia magna, this level was 0.032 mg L−1.)

    Keywords:

    hazard evaluation, ecotoxicology, model ecosystem, species interactions, multivariate statistics


    Paper ID: STP26253S

    Committee/Subcommittee: D19.24

    DOI: 10.1520/STP26253S


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