Demonstration of the Ecological Effects of Streptomycin and Malathion on Synthetic Aquatic Microcosms

Abstract

Small synthetic microcosms have been developed in the authors' laboratory to provide replicate aquatic communities with interspecies competition within primary, secondary, and recycling trophic levels. The microcosms display nutrient depletion, algal competition and succession, and algal depletion through grazing and nutrient depletion. Streptomycin acted as a selective algal toxicant, reducing all indexes of primary production temporarily, and then modifying the algal dominance relationships over the 63-day experiment, although no active streptomycin could be detected by Day 28. Daphnia populations were reduced and ostracod populations markedly increased in the streptomycin-treated microcosms. These results were consistently shown in three successive microcosm experiments. In contrast, malathion caused a temporary reduction in the number of grazers and a concurrent algal bloom. Degradation of malathion was presumed from the recovery of the grazer populations, which was accompanied by the elimination of the algal bloom. The synthetic microcosms, being composed of distilled water, silica sand, reagent-grade chemicals, and organisms that are easily reared in the laboratory, show promise of providing a nonsite specific, reproducible ecosystem-level bioassay.

Life history characteristics of the freshwater ostracod Cyprinotus incongruens and their application to toxicity testing

“…Ostracods have also been included in several community-level microcosm experiments (Taub et al, 1981;Takamura and Yasuno,1986;Landis et al, 1992). Although densities of ostracods and algae were often depressed by pesticides, over the longer term their densities increased, presumably by indirect effects of depressing competitors and predators (Taub et al, 1981;Takamura and Yasuno, 1986).…”

“…Although densities of ostracods and algae were often depressed by pesticides, over the longer term their densities increased, presumably by indirect effects of depressing competitors and predators (Taub et al, 1981;Takamura and Yasuno, 1986). In a 2-month microcosm experiment investigating population and community responses to jet fuel pollution, Landis et al (1992) found that population increases of both Daphnia and ostracods were delayed by up to 10 days and peak population densities were depressed.…”

Unique Information Contributed by Multispecies Systems: Examples From the Standardized Aquatic Microcosm

“…The pesticide malathion temporarily eliminated Daphnia and reduced other grazers, resulting in a massive, but temporary, algal bloom (Taub et al 1983). By the time that the malathion had degraded, reintroduced Daphnia had a large food supply and rapidly developed large populations.…”

“…A thorough review of the literature documented that many blue‐greens had been shown to be sensitive to streptomycin, but it is unlikely that a risk assessment would have recognized blue‐greens as bacteria and therefore likely to be sensitive to an antibiotic. In communities in which nitrogen fixation by blue‐greens is important, their loss could significantly reduce available fixed nitrogen and also result in dramatic increases in ostracods, presumably by increasing their food supply (Taub et al 1983). Neither blue‐greens nor ostracods are included in the traditional toxicological tests, and increased populations are not among the attributes measured.…”

The application of bioassays in the resolution of environmental problems; past, present and future

“…Heath, 1979;Taub et al, 1983;Stay etal., 1985;Biesinger & Stokes, 1986;Larsen et al, 1986) periphyton growing on artificial substrates (e.g. Some of these have been laboratory studies involving mixed-flask cultures (e.g.…”