The standardized aquatic microcosm (SAM) as developed by Taub is a 64-day multispecies assay designed to model a generic freshwater ecosystem. An extensive protocol is available that covers every aspect of the experiment. In addition, a series of computer programs is available at the University of Washington, Seattle, Washington, for data analysis.The SAM has recently undergone a round-robin test series, in which good repeatability was demonstrated among the four laboratories that took part. These factors have led to our use of the SAM as an ecosystem-level assay for assessment of the effects and fate of disparate materials in aquatic systems.

To date, three materials have been assayed in our laboratory. Copper sulfate was assayed at two series of concentrations to act as an in-house control and as part of the round-robin SAM testing. A brass dust and graphite dust have also been assayed using the SAM protocol. In setting test concentrations for the SAM, Daphnia magna 48-h and algal 96-h assays were performed using ASTM methodologies.

The SAM has proven to be a useful assay. Currently, the disadvantages are the amount of labor required in the preparation of the test media, culturing of the organisms, and data analysis; the breakage of test vessels was also a problem. The authors are planning to automate much of the data handling to reduce repeated manual manipulation and the concomitant errors. Breakage of the test vessels has been reduced considerably by modifications of the sterilization procedure. The advantages of the SAM are the ability of the system to handle a variety of test compounds and the ability to simultaneously look at both effects and fate. Results varied among the compounds tested from very strong acute toxic effects to classical signs of eutrophication. Interactions among the biota were observable. The fate of the toxicant was also altered by the complex community, in contrast to simpler abiotic fate studies.