The catchment of the Dovinė river (right tributary of the Šešupė river, the Nemunas catchment) is situated in the Žuvintas Biosphere Reserve. However, anthropogenic pressure due to agriculture, fishery and urbanization is observed in this catchment. There are forests (33%), agricultural lands (34%), swamps (21%) and water bodies (8%) in the Žuvintas Biosphere Reserve. There are about 1000 plant species (30 of them protected) and 2500 animal species (2200 invertebrates, 220 birds, 15 amphibians and reptiles, 21 fishes, and 43 mammals) in this reserve. The recent transformation of the hydrochemical and hydrophysical conditions, as well as of the former habitats is caused by the huge amounts of biogenes observed in the water bodies of the biosphere reserve and in the other lakes of the Dovinė river catchment. The ecological situation in the river catchment is investigated considering the distribution of phosphorus in the riverine system. According to the observation results, the annual inflow of phosphorus reaches 15200 kg P y^–1 (78% of it is the anthropogenic phosphorus) in the Dovinė river catchment. There is about 7960 kg P y^–1 retained in the five largest lakes of the basin. The lowest content was found in Lake Dusia (80 mg m^–²) and the highest in Lake Simnas (980 mg m^–²).

Keywords: the catchment of the Dovinė river, Žuvintas Biosphere Reserve, phosphorus load, phosphorus retention, eutrofication