Phosphorus fractionation in lake sediments – Lakes Volvi and Koronia, N. Greece

Sediments from two lakes, the meso-to-eutrophic Volvi and the hypertrophic Koronia, located in N. Greece were examined on the basis of P-fractionation. In both lakes, the rank order of P-fractions was HCl–P>NaOH–P>BD–P>NH4Cl–P. The loosely sorbed phosphorus (NH4Cl–P) represented <1% of the sedimentary inorganic phosphorus, while the reductant phosphorus (BD–P) ranged 5–6%. The calcium bound phosphorus (HCl–P) showed considerable contribution (59–74%) to the sedimentary inorganic P-loads. The metal oxide bound phosphorus (NaOH–P) was higher in the hypertrophic (30–35%) than in the meso-to-eutrophic system (19–28%). Fine-sized sediments exhibited significantly higher concentrations of HCl–P in Volvi and NH4Cl–P in Koronia. Sampling month had significant effect in variance of most P-fractions and other sediment features in both lakes. Use was also made of multivariate statistics to identify the factors which influence the sedimentary phosphorus. NaOH–P was the most reactive fraction in Lake Volvi. Iron compounds and organic matter seem to play a significant role in regulating this labile P-budget. NH4Cl–P was the more reactive fraction in Lake Koronia which was influenced by sedimentation of P-absorbed on clay/silt fine particles.