Assessment of the Precision and Accuracy of SAM (Standardized Aquatic Microcosm) and MFC (Mixed Flask Culture) Microcosms Exposed to Toxicants

摘要

The results of 30 mixed flask culture(MFC) and four standardized aquatic microcosm (SAM) microcosm experiments were used to describe the precision and accuracy of these two protocols. Coefficients of variation (CV) for chemical measurements (DO, pH) were generally less than 7% for ecosystem processes(primary productivity, respiration) less than 20%, and for structure (organism density) between 20 and 200%. Microcosm age had no effect on the CV; however, treatments causing a high magnitude of response resulted in significantly higher CV values. Coefficients of variation, statistical power, and minimum detectable differences for several treatment-replicate combinations are presented to aid in designing future MFC experiments. Accuracy was evaluated for the SAM and MFC microcosms by comparison to results reported for field studies of fluorene, atrazine, and chlorpyrifos. Comparisons were based primarily on the lowest effect level of short-term direct effects and the relative hazard ranking of these chemicals. The results of comparisons suggest that these microecosystems have properties common to natural systems, and their responses are more than an artifact of the microcosm. (Copyright (c) American Society of Testing and Materials 1989.)