Ain Järvalt

Learn More
The diel migration and spatial distribution of fish were explored using six sequential 4-h sample gillnettings in the pelagic and littoral zones of Lake Verevi (Estonia, 12.6 ha, max. depth 11 m, hard-water, deoxygenated hypolimnion) in August 2001 and July 2002. Considering abundance, two-thirds of the total fish moved to the littoral zone. The biomass of(More)
The present study describes generally the ecosystem of Lake Verevi while more detailed approaches are presented in the same issue. The main task of the article is to estimate long-term changes and find the best method for the restoration of good ecological status. Lake Verevi (surface 12.6 ha, mean depth 3.6 m, maximum depth 11 m, drainage area 1.1 km2,(More)
The influence of functional group specific production and respiration patterns on a lake's metabolic balance remains poorly investigated to date compared to whole-system estimates of metabolism. We employed a summed component ecosystem approach for assessing lake-wide and functional group-specific metabolism (gross primary production (GPP) and respiration(More)
Lake Ülemiste, the drinking water reservoir of Estonia’s capital city Tallinn, was biomanipulated by manual removal of cyprinids in 2004–2006 and its impact on water quality in the vegetation period was studied. A total biomass of 156 tonnes corresponding to 160 kg ha−1 of fish, predominantly cyprinids, were removed. A decline in the unit catches of fishing(More)
Efficient zooplankton grazing is a prerequisite for establishing a cascading food web control over phytoplankton in a lake. We studied if the top-down impact of fish could reach phytoplankton in a lake where the grazing pressure of small-sized zooplankton on filamentous phytoplankton is considered weak. We analysed >30 years of data on plankton, fish(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)
  • 1