Summer P for Petrozavodsk Bay in 1999–2010 varied significantly between years (38–233 mm per month) with a tendency to increase in the late 2000s (Figure 5). The Chl a concentration recorded in the water of Petrozavodsk Bay was high in the summers of 2005 (6.4 μg dm−3) and 2007 (7.2 μg dm−3), but click here was generally much lower in recent years compared with the beginning of the 2000s ( Figure 6). The dominant phytoplankton complex consisted of diatoms, a common taxon in every season throughout the period studied. Summer phytoplankton

abundances in Petrozavodsk Bay varied from 0.35 to 1.2 in 1991–1993 and from 0.15 to 1.2 × 106 indiv. dm−3 during 1999–2008, with a tendency to decrease in the latter period (Figure 7). A characteristic feature of the summer phytoplankton in the study area, which was observed every year in 1990–2010, was the growth selleckchem of Cyanobacteria and the presence of species from Chlorophyceae and Cryptophyceae. The zoobenthos of Petrozavodsk Bay consisted of glacial relict crustaceans (Monoporeia affinis and Palasea quadrispinosa), oligochaetes and chironomids with low species richness (14 taxa). Recent years have

seen an increasing trend in the zoobenthos biomass, however. The average current abundance and biomass reached 0.4– 5.4 × 103 indiv. m−2 and 1.1– 5.7 g m−2 respectively ( Figure 8). A high abundance and biomass were recorded in 2010 (up to 17 × 103 indiv. m−2 and 19 g m−2 respectively), the maximum value in the Olopatadine last 40 years. Spearman’s rank correlations yielded significant (p < 0.05) relationships between the climatic and biotic variables ( Table 1). Chl a correlated positively (R = 0.66; p = 0.03) with WT and negatively with ICE-FREE (R = − 0.53; p = 0.05). The phytoplankton abundance depended on the duration of the ice free period (R = − 0.89; p = 0.006); higher values were recorded in summers following longer periods of ice cover. The abundance of planktonic Cyanobacteria increased significantly (R = 0.89; p = 0.006) in years with a high NAO index. Negative correlations were obtained between

the global indices and the N and B of the zoobenthos (Table 1); the same tendency was observed for the several benthic groups (Oligochaeta). At the same time the B of zoobenthos correlated positively at a high level of significance with WT (R = 0.72; p = 0.01) and negatively with P (R = − 0.77; p = 0.005). Multiple regression analysis confirmed close relationships between NAO and regional climate variables (WT, P, ICE-FREE) at p < 0.01 ( Table 2) and also between AO and these climatic variables at p < 0.02 ( Table 3). Chl a was governed mainly by WT at p < 0.05 ( Table 4). Similar WT-dependent correlations were recorded for other zoobenthos variables ( Table 5). Also, zoobenthic B and N depended on ICE-FREE (p < 0.05). Evidence from the analysis of long-term data sets shows that many of the effects of changing climate are already occurring in different lakes.