Figure 1.
Temperature (A), and oxygen saturation (B) profiles during Phase I and Phase II of the bloom.
Black circles represent sampling points. Data are available at a higher spatial resolution only during Phase II of the bloom (small black circles).
Figure 2.
Micrographs of DAPI and FISH stained Aphanizomenon flos-aquae filaments and heterotrophic bacteria, respectively; collected from the epilimnion during Phase I (A) and Phase II (B).
Cyanobacteria in Phase I are found in tufts (A1), the filaments contain poly-P granules (A2) and are hardly colonized by heterotrophic bacteria (A3). In Phase II single filaments with ghost cells are visible (B1). These are often aggregated with poly-P granules spilled onto the aggregate (B2) and heavily colonized by heterotrophic bacteria (B3). Significant increase in colonization between Betaproteobacteria and Flavobacteria in Phase I (A4–5) and Phase II (B4–5) is visible. End of Phase II is characterized by an increase in nanoflagellates (B6).
Figure 3.
Bacterial protein production (BPP) of particle-attached (PA) and free-living (FL) bacteria in the epilimnion and hypolimnion (A) and bacterial abundance of total bacteria in the epilimnion (B) and hypolimnion (C) during the two phases of the bloom.
Figure 4.
Denaturing gradient gel electrophoresis dendrogram showing the relationship between particle-attached and free-living bacterial communities from epilimnion and hypolimnion of Lake Stechlin during Phase I and Phase II of the bloom.
The gels were analyzed using the Phoretix 1D version 11.4 (TotalLab) software and cluster analysis was done with PAST3 [25] using the Bray-Curtis similarity measure.
Figure 5.
Distribution of relative abundances of major phylogenetic groups (% of DAPI - right axis): Alphaproteobacteria, Betaproteobacteria, Bacteroidetes, Planctomycetes and Actinobacteria as assessed by CARD-FISH in the particle-attached and free-living fractions in both epilimnion and hypolimnion.
Phase I and II of the bloom are separated by the dashed line. The abundance of Aphanizomenon flos-aquae (gray field) is presented during both phases of the bloom (left axis).
Figure 6.
Sequence frequencies of major particle-attached (PA) and free-living (FL) bacterial families comprising to >5% of total sequences in at least one sample in the epilimnion and hypolimnion of Lake Stechlin during Phase I and Phase II of the under-ice bloom.