| Summary: | Riverine transport is the most important pathway for the input of nutrients into two large shallow nonstratified lakes Peipsi (3 555 km2, mean depth 7.1 m) and Võrtsjärv (270 km2, mean depth 2.8m) in Estonia . In the 1980s, the riverine discharge of nutrients increased drastically while in the early 1990s a sharp decrease occurred, first of all in TN loadings caused mainly by the collapse of the extensive type of agriculture. The ecosystem of L. Võrtsjärv is very sensitive to water level fluctuations which are following the pattern of North Atlantic Oscillation index (NAO) refelecting the changes of climate in northern hemisphere. In L. Võrtsjärv high phosphorus concentration and better light availability are the main concequences of low water level bringing about higher phytoplankton density and deteriorated water quality. In deeper L. Peipsi the direct influence of the water level is not so obvious and the effect of climate realizes through nutrient loading, temperature and wind. JRC.H.5 - Rural, water and ecosystem resources
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