Microcosm Studies (Outdoor Microcosms)
The objectives and general conduct of outdoor microcosm studies are similar to those described for indoor microcosms. Springborn Smithers has performed microcosm studies in test systems ranging in size from 1 m3 to 11 m3 (as well as much larger "mesocosm" studies in 0.1-ha ponds, which were done to satisfy previous US EPA requirements and are not recommended for general use). Fish (e.g., sticklebacks or fathead minnows) can be included in systems larger than about 5 m3, if necessary. As with indoor microcosms, the study design and the number and frequency of ecological measurements can vary widely depending on the questions that need to be addressed.
Since 1990, Springborn Smithers has conducted nearly twenty indoor and outdoor microcosm studies at our US and Swiss facilities. The microcosm facility in Switzerland consists of four polyethylene coated concrete basins, each 9 m by 9 m in area and 1.7 m deep, containing sediment, water, and biological communities from a large natural reserve area in the nearby Lake of Constance. To conduct a study in these systems, open-ended stainless steel cylinders are installed in the basins to isolate replicated experimental units of any desired volume from 1 to 10 m3. The microcosm facility is designed for maximum flexibility, because it allows studies to be conducted using custom microcosm sizes and a flexible number of replicates on a case-by-case basis. A very low biological variability between the isolated replicates is achieved. Full dose-response microcosm studies have been conducted with up to 17 enclosures per study. These studies have included observations to determine recovery. Extensive expertise in the spray-drift and run-off application modes has been gained. The corresponding application techniques have been developed and validated at the Swiss Research Center.
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