Pelagic enclosures - modification and use for experimental study of riverine plankton
Thorp, J. H.; Black, A. R.; Jack, J. D.; Casper, A. F.
To understand better the mechanisms regulating potamoplankton, we developed an experimental in situ technique using drifting pelagic enclosures and successfully tested these "potamocorrals" in the Ohio River (USA). The technique employed 16 cylindrical, nitex mesh bags (83 11m) surrounded by a PVC plastic frame and supponed by a floating platform. The 1.5 m diameter bags enclosed 3500 litres and were submerged 2 m in the water. Potamocorrals were maneuvered when necessary by power boats but allowed to drift downstream for most of the day. Chemical and physical parameters inside and outside the bags did not differ significantly, and the enclosures worked well for studying biological interactions between plankton and both fish and invenebrate planktivores, over multiple 5-day experimental periods.