An enclosure for experimental manipulation of lentic littoral and benthic communities

We describe an experimental enclosure for use in lentic habitats which is relatively inexpensive, easily constructed, and conveniently stored between experiments. The basic design is quite versatile. Enclosures can be built in sizes ranging from 4 inches (10 an) to 17 inches (43 cm) in diameter (area of bottom—81 to 1464 square centimeters); the mesh size of the sides may be varied; and the tops may be open or closed by a clear plastic lid. Results of independent one-month-duration experiments suggest no “enclosure effects” on water temperature or dissolved oxygen concentrations. Comparison of benthos densities within enclosures and in open sites located nearby in the saw habitats indicate that most taxa exhibited similar changes in abundance under the two conditions; some exceptions are attributable to exclusion of certain predators from the enclosures; and a few cases suggest that certain insect taxa may have experienced reduced recruitment when enclosure tops were closed. We are currently performing a variety of competition experiments involving odonate larvae. Our experience suggests that this enclosure design might be appropriate for many kinds of in situ experiments in lentic littoral habitats.