The changes in the the structure and functioning of the food web of the Enonselkä during 2010-2013

In the Enonselkä basin of Lake Vesijärvi, a large aearation project has been started to reduce internal nutrient loading. The aeration will probably reduce the flux of phosphorus from the bottom sediment to the water column, but it may also have strong effects on the functioning of the pelagic food web. Due to the aeration, the water temperature in the hypolimnion will rise, with consequences for the stabiltiy of temperature stratification and dominance relationships in the pelagic animal communities. For instance, fish species requiring low water temperatures (vendace, smelt) may decrease in abundance, which will again have effects on the prey populations of these fish species. Pelagic invertebrate predators (e.g. the cladoceran Leptodora kindtii) can increase in abundance, with consequences for herbivorous zooplankton and phytoplankton. In this study, the abundance and spatial variation of pelagic invertebrate predators in Enonselkä, and the effects of artificial aeration are studied. Together with data on fish communtities and herbivorous zooplankton, the results can be used to evaluate the effects of artificial aeration on the functioning of pelagic food webs. The project will be continued in 2011.