Relationships between short-term and long-term responses of phytoplankton to eutrophication of the largest shallow lake in Central Europe (Balaton, Hungary)

摘要

As a result of the increased phosphorous load, the originally mesotrophic Lake Balaton Underwent rapid eutrophication that began in the 1960s – 1970s. Because most of the nutrient load is received by the western basin, a sharp trophic gradient developed in the lake: the western part is hypertrophic, while the eastern remains meso-eutrophic. The paper describes the phytoplankton changes in the last four years (1989-1992) both in the hypertrophic and meso-eutrophic parts of the lake. Floristic changes of the last 60 years, long term trends of quantitative changes change and short-term (daily) responses of phytoplankton to weather changes are discussed with special attention to Cylindrospermopsis raciborskii, a key species in the lake. The paper concludes that the management program that was started in 1983 to restore the lake and during which the external P load was reduced by about 40% has so far not resulted in significant improvement in water quality, for the P accumulated in the sediment in the period of high external load still supports the development of high late summer algal crops.