Mesocosms: Enclosed Experimental Ecosystems in Ocean Science

Enclosed experimental ecosystems (“mesocosms” and “microcosms”) have become widely used research tools in aquatic sciences because they allow for a relatively high degree of experimental control and replication necessary for hypothesis testing while still capturing dynamics that emerge from ecosystem-level interactions between organisms and their physical and chemical environments. Mesocosms provide a bridge between observational field studies and process-oriented lab research. Over the last 40 years, mesocosms have become important tools in the marine environment to address critical research questions in the fields of chemical and physical oceanography, ecotoxicology, fisheries science, and basic and applied ecology. Today they are increasingly important as tools for assessing the ecological impacts of global change. To be effective as research tools, great care must be given to the design, operation and interpretation of investigations conducted in experimental ecosystems. Problems of scale necessitate consideration of two key questions for researchers who employ experimental ecosystems. First, how can experiments be designed to accurately capture essential chemical, physical and biological characteristics of the “real world” that is being modeled? Second, how can results from experiments conducted in these simplified systems be systematically and quantitatively extrapolated to improve our understanding of nature