Factors influencing lake recovery from eutrophication - The case of basin 1 of Lake Balaton

Lake Balaton is a large, shallow, and calcareous lake that was subject to a rapid eutrophication during the 1970s. Management measures taken from the mid 1980s decreased the phosphorus load to the lake from 0.5 to 0.3 g Pm-2 yr(-1). Using long-term load and water quality data, we analyse the respons e of the formerly hypertrophic Basin 1 of the lake by the means of simple e mpirical models. Several factors that are commonly neglected during studies of lake recovery modified the apparent settling velocity of total P and co nsequently, the biomass of the phytoplankton. These factors included the lo ads of calcium and suspended solids, the loading ratio of the dissolved to particulate phosphorus, and blooming of the dominant cyanobacterium, Cylind rospermopsis raciborskii. Due to the rapid immobilisation of the mobile pho sphorus in the surface sediments, moderate reduction (45-50%) in the extern al load resulted in a surprisingly fast and significant improvement of the water quality in the hypertrophic southwestern basins of the lake, (C) 2001 Elsevier Science Ltd. All rights reserved.