Internal Phosphorus Loading in Eutrophic Lakes in Western Poland

Abstract

We hypothesized that the variability of P internal loading in lakes and reservoirs depends on the trophic state of analysed waterbodies, as well as spatial (different water depths) and temporal (season) aspect in particular waterbodies. Additionally, year-to-year changes of P loading in lakes restored with variable methods (sustainable restoration, P inactivation with iron compounds and magnesium chloride, nitrate treatment and effective microorganisms (EM) application) were expected. To verify these assumptions, we have analysed the process of internal P loading in 40 waterbodies situated in Western Poland, based on the ex situ experiments on intact sediment cores, collected from different water depths in various seasons. Additionally, basic sediment characteristics (TP and its fraction content, organic matter, SRP and TP in pore water and water above sediments) were studied. The most intensive P release from sediments into water column was noted in summer, especially at greater depths and in heavily eutrophicated lakes. Internal P loading in restored lakes usually decreased, apart from lakes in which EM were used.