The effects of hypolimnetic oxygenation in the shallow and eutrophic Lake Comabbio (Northern Italy) studied by the "enclosure" methodFunded under: JRC-ENVPROT 4C
Two cylindrical "enclosures" (diameter = 40 m; height = 5 m; volume = 7000 m3) were anchored in the shallow and eutrophic Lake Comabbio (Italy) to isolate two water columns with their sediments. Hypolimnetic oxygenation was applied to one enclosure, the other being kept as a control. The most important results were the following: a) neither destratification nor sediment resuspension were produced by oxygenation of the hypolimnion layer; b) the oxygenation rate greatly exceeded the oxygen consumption; c) during the oxygenation period the ammonia and phosphorus concentrations increased in the water column; d) phyto- and zooplankton were greatly influenced by oxygenation; e) during the anoxic period in the lake and in the control (but not in the treated enclosure) many dead fish were found. In conclusion, the oxygenation, abolishing the fish mass mortality, prevented the release into the water of a huge amount of organic substances. On the other hand, the addition of oxygen modified the ecosystem structure and functioning, accelerating the production and decomposition rates of the organic matter. Because these conclusions are related to the oxygenation method adopted and the ecosystem characteristics, they should be generalised with great caution.
Bibliographic Reference: Paper presented: The Whole Field of Limnology, München (DE), Aug. 12-19, 1989
Availability: Available from (1) as Paper EN 34999 ORA
Record Number: 198911230 / Last updated on: 1994-12-01
Original language: en
Available languages: en