A mesocosm is a purpose built micro-environment used to study the effects of a closed controlled ecosystem on an organism. I had setup some large mesocosms at the Buffalo River Science Center before I graduated from MSUM. They were built to house Anax junius members, a dragonfly species, to study the effects of a changing environment. However, before I could get the research started, I was graduating, but they were setup so someone else could continue where I left off.
This experience helped me prepare some mesocosms while studying the life history of the Mohave Tui Chub with a post-doctoral student. At the Desert Studies Center, Zzzyx, CA, we setup several large water troughs inside the lake (to keep those environments as close to their natural habitat as possible), and also several water troughs outside Lake Tuende.
These water troughs were filled with filtered water from Lake Tuende and then populated with the Mohave Tui Chub and in a select number of them the mosquito fish. Each was covered with a wire mesh to prevent predation.