Management of lake ecosystems in the changing environment - re-evaluation of the effects of artificial aeration

An old and very widely accepted paradigm in limnology is that internal phosphorus (P) loading is prevented or strongly diminished by aerobic conditions at the sediment-water interface. Based on laboratory experiments conducted during the 1930’s it has been assumed that oxygen concentration above lake sediment is the primary regulator of P release from the sediment, because at low oxygen concentrations iron (Fe) is reduced and loses its capability to bind P. This issue is of crucial importance for lake ecosystems, where P is one of the most important factors regulating ecosystem productivity and sediment has a huge pool of P compared to the overlying water. The oxygen-internal loading paradigm has had a very strong impact on the research and management of aquatic ecosystems.
It is possible, however, that due to the climate change, conditions in aquatic ecosystems (thermal stratification, wind effects) have changed so much that results from the 80-year-old experiments forming the cornerstone of the oxygen-internal loading paradigm are not valid anymore. Thus, lake managers should adapt their strategies to the changing climate. More attention should be also given to the possible negative effects of aeration (e.g.the change in the thermal properties of the water column). In this project, the effects of artificial aeration on the thermal stratification and stability of the water column, turbulence and oxygen concentration in the water-sediment interface, as well as redox potential and oxygen demand of the sediment are studied.The studies are conducted in Lake Vesijärvi, where a large aeration project has been started.