The likelihood nr phosphorus release from lake bottom sediments inio bulk water as a result or changes in the physicochcmical conditions in the lake has been analyzed by the method or sequential extraction proposed by Tessier et al. The procedure developed for estimation of the threat to waler ecosystems posed by heavy metals accumulated in the bottom sediments, can be successfully applied in estimation of the release or other substances, including biogenie ones, as the subsequent states of extraction simulate the abioric conditions and processes that can naturally take place in the near-bottom water layer and in the bottom sediment.