Some ecological and experimental properties of complex aquatic microcosms

To fully realize their potential as tools for ecological research, microcosms must be designed which optimize replicability, baseline stability, persistence, and functional similarity to natural ecosystems. Evidence is presented which demonstrates that complex aquatic microcosms, containing whole biotic communities taken directly from a pond, satisfy these criteria. These microcosms persist in a stable condition (internally constant) for many months. Replicability is comparable to most laboratory or greenhouse experiments, with coefficients of variation ranging from 10–30 percent for most parameters measured. An experiment comparing microcosms with an actual pond indicated that pond microcosms are good models of natural ecosystems. Microcosms are most useful for studying processes which are affected by functional interactions between organisms, such as nutrient cycling, energy flow, and contaminant transport.