Turnover of DNA-P and phospholipid-P in lake sediments

Identifying and quantifying the forms of phosphorus ( P) in lake sediments is a prerequisite for understanding lake trophic status and possible exports of Pdownstream. Organic Pis one of the most important Pforms found in the sediment, where orthophosphate diesters, including DNA and phospholipids, represent a degradable Ppool that can support primary production and eutrophication. In this study, sediment cores from the eutrophicLake Erken and the oligotrophic Lake Annsjon, both in steady state regarding long-term Pinput revealed trends in the degradation of DNA- Pand PL-Pwith sediment depth. Comparisons were performed based on the differentiation of essentially permanent or recalcitrant Pand temporary, potentially mobile Pfor the respective fractions. The temporary Ppool was defined as the part of the total Ppool calculated for values higher than the level at which the measured Pconcentration converged to a constant value and the recalcitrant pool was defined as the difference between the total and the temporary. The temporary diester- Ppool comprised over 20 % of the total temporary Pin Lake Erken and around 4 % in Lake Annsjon. The decrease in Pconcentrations with depth was more rapid for DNA- Pcompared to PL-Pin both lakes, suggesting that DNA- Phas a more prominent role in internal loading. The study shows that Pmobilization potential can be different for different Pfractions, which is important when assessing their contribution to internal loading of Pwithin an aquatic system.