Algae, laboratory tests

The second difference between the laboratory tests and exposure under realistic environmental conditions is that in the laboratory exposure concentrations are maintained, or the ecotoxicological endpoints are adjusted to account for any decline. Under natural conditions a combination of the pyrethroids tendency to partition rapidly and extensively to organic matter, coupled with their susceptibility to degradation in aquatic systems where algae and macrophytes are present [13,14], means their overall dissipation rate from the water phase is generally relatively rapid. Water column dissipation half-lives tend to be around 1 day (see Sect. 5). This behavior means that it is unlikely that aquatic organisms will be exposed to pyrethroids in the water phase for prolonged periods in natural water bodies. 

Table IV. Comparison of three estimates of bioconcentration factors for aquatic plants in laboratory tests. Values for duckweed were calculated from the rate constants shown in Table III, and from the regression equation of Lockhart et al. (14), using a value of 120 hours for exposure time. Values for green algae were calculated from the equation of Ellgehausen et al. (6).

In Phase II, important processes that affect the chemical composition, toxicity, and fate of leachates from highway C R materials and assemblages were evaluated in laboratory tests [1-4,215,216,222-224]. The tests provided information on the teachability of constituents in C R materials under a range of conditions thought to provide reasonable estimates of expected leachate chemical concentrations. The tests provided information on the removal, reduction, and retardation of leachate constituents by natural processes. Algae and daphnia toxicity tests assessed the toxicity of the samples at the leachate source or after modification by RRR processes, and chemical analyses enabled quantification of leachate chemical components at all stages of the laboratory tests. Each laboratory test resulted in the measurement of mass transfer rates of leachate chemical components under controlled conditions, the results of which were applied to specific mathematical models of the process. 

Both methods have been shown to be effective in illustrating the relationships between laboratory sublethal toxicity tests (using fish, invertebrates, and algae) and receiving environment measurements of fish and benthic invertebrates. The applications, strengths, and weaknesses of both the ZPE and LTF methods are discussed and compared. 

Bioassays appeared to fit the bill to perform this service to monitor chemical contamination. They have been around for a while. Until relatively recently, however, they remained in the realm of the laboratory. Only over the last two decades have they found a niche in testing for toxic chemicals in water and sediment, but not yet specifically as a tool for routine water quality monitoring. As Small-scale Freshwater Toxicity Investigations, Volumes 1 and 2 amply demonstrates, the science has now come of age. Assays based on bacteria, microscopic or multi-cellular algae, protozoa, invertebrates and vertebrates (freshwater fish cell cultures) are discussed in... 

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