Cosms

Keeping with theme days, Thursdays will deal with stories with an ecological leaning. As part of my research I used outdoor, aquatic microcosms, which are “mini universes”, to assess the fate of BFRs and their effects the aquatic community. Microcosms are a link between controlled lab studies, and inherently variable field based studies. The common form of a microcosm is an experimental pond, which contains natural water, sediment, and a community of microorganisms, zooplankton, macroinvertebrates, aquatic plants, and sometimes even fish.

A microcosm at the University of Guelph

Microcosm studies benefit from increased realism that is often not considered in laboratory tests, and rather than assessing effects on a single species, they are capable of generating ecosystem level effects. Effects at the ecosystem level are very important because they incorporate such natural occurrences like species interactions, recovery, and various indirect effects. Indirect effects are when an effect is exerted through ecological mechanisms, which cannot be detected in typical laboratory tests, such as changes in predation rates, or increased primary production. These two examples highlight top-down and bottom-up effects. In order to understand these effects, it is important to have an understanding of the composition of the system and the interactions between the species and the food web. Generating this data often requires a high level of expertise (taxonomic identification) and can be quite time consuming. This is just one of the difficulties associated with microcosm studies, some other include the cost, the lack of standardization, and the high level of variance. The level of variance in microcosms often can make it difficult to detect significant differences between treatments. Despite the drawbacks, I really feel that the added level of realism is worth the extra variability seen in microcosms studies, and that the results from a microcosm study should be held with a greater weight.

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