Lea Tuvikene

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The nutrient budget, phytoplankton primary productionand sedimentation rate were studied weekly in the large(270 km2) and shallow (mean depth 2.8 m)eutrophic Lake Võrtsjärv in 1995. The annualexternal loading was 7.7 g m™2 y™1 of totalnitrogen (TN) and 0.2 g m™2 y™1 of totalphosphorus (TP), including 7% of both inputs asdirect atmospheric precipitation. The(More)
Phytoplankton primary production measurements and sediment trapping in the large (270 km2) shallow (mean depth 2.8 m) Lake Võrtsjärv were performed during ice-free periods in 1995-1996. Sedimentation rate varied from 26 to 700 g DWm-2d-1 (DW=dry weight), with a mean value of 170 g DWm-2d-1. Under the influence of prevailing westerly and south-westerly(More)
In order to disentangle the causes of variations in water chemistry among European shallow lakes, we performed standardised sampling programs in 86 lakes along a latitudinal gradient from southern Spain to northern Sweden. Lakes with an area of 0.1 to 27 000 ha and mean depth of 0.4–5.6 m located in low to high altitudes were investigated within the EC(More)
Nutrient (P and N) enrichment experiments in small enclosures (20 l) were carried out to determine P and/or N limitation of bacterioplankton in Lake Võrtsjärv. The specific interest of the study was to test if it is possible to detect nutrient `physiological' or growth (rate) limitation of bacterioplankton and competition for nutrients (N and P) with(More)
The hydrochemical regime and the biota in two lakes of Vooremaa landscape protection area, Central Estonia, were studied in 2000–2001 within the frames of the EC project ECOFRAME aimed to work out water quality criteria for shallow lakes in Europe. Lake Prossa is a macrophyte-dominated lake with an area of 33 ha and a mean depth of 2.2 m. Most of the bottom(More)
Understanding of the true role of lakes in the global carbon cycle requires reliable estimates of dissolved organic carbon (DOC) and there is a strong need to develop remote sensing methods for mapping lake carbon content at larger regional and global scales. Part of DOC is optically inactive. Therefore, lake DOC content cannot be mapped directly. The(More)
Long-term data on phytoplankton species composition in large and shallow Lake Võrtsjärv indicated a sharp deterioration of the ecological status at the end of the 1970s. The more traditional water quality indicators, such as the concentrations of nutrients and chlorophyll a, phytoplankton biomass, and Secchi depth, failed to capture this tipping point or(More)
This study is the first attempt at the European scale to make an inventory of ecosystem services (ESS) of a large lake. We analysed a set of ESS indicators against the annual mean values of environmental parameters for 2006–2013. According to principal component analysis, the trophic state- and hydrology-related factors explained about 70% of the(More)
Periphyton communities play an important role in shallow lakes and are controlled by direct forces such as temperature, light, nutrients, and invertebrate grazing, but also indirectly by planktivorous fish predation. We performed a pan-European lake mesocosm experiment on periphyton colonization covering five countries along a north/south(More)
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