Chrysophyte cyst-inferred variability of warm season lake water chemistry and climate in northern Poland: training set and downcore reconstruction

Chrysophyte cyst assemblages from sediment trap and surface sediment samples of 50 lakes in northern Poland were related to environmental variables using multivariate numerical analyses (DCA, CCA). Water electric conductivity, total nitrogen, total phosphorous, turbidity, and cation and anion compositions (Ca2+, HCO3 (-)) accounted for significant and independent variations in the chrysophyte cyst assemblages. The first canonical axis was related to the gradient of Ca2+ while the second axis was correlated with total nitrogen. A quantitative transfer function was then developed to estimate Ca2+ (log(10) transformed) from modern chrysophyte cyst assemblages using weighted-averaging regression with classical deshrinking. The bootstrapped regression coefficient () was 0.68, with a root-mean square error of prediction of 0.143 (log(10) units). The calibration model was applied to a varved sedimentary sequence (AD 1898-2010) from Lake A >> abiAskie, Masurian Lakeland (NE Poland). Observational data from this lake show that the Ca2+ variability in the epilimnion depends on the efficiency of Ca2+ scavenging by CaCO3 precipitation in early summer, which in turn is a function of water column stratification, temperature and the wind regime from late spring to early fall. The spring-fall wind regime drives the water column mixing. In Lake A >> abiAskie, cyst-inferred warm-season lake water Ca2+ concentrations are significantly negatively correlated with calcite precipitation (CaCO3 concentrations in sediments; R = - 0.49, p(adj) < 0.001; AD 1898-2010; 3-year filtered), and cyst-inferred lake water Ca2+ concentrations are significantly correlated with zonal wind speed (m s(-1)) (R = 0.50; p(adj) < 0.001; AD 1898-2010; 3-year filtered). This study demonstrates that chrysophyte cyst assemblages in Polish lakes respond to hydrochemical factors driven by climate variability.