Figure 1.
Experimental setup showing origin, distance, and features of the three lakes: Lake Stechlin (ST) and Lake Grosse Fuchskuhle Northeast (NE) and Southwest basins (SW). Pollen incubations were sampled four times within two weeks for molecular analyses (DGGE, qPCR, clone libraries), chemical side parameters (see main text), and microscopy.
Figure 2.
Examples of fungal morphologies.
Examples of fungal morphologies observed during the pollen degradation experiment, stained by Calcofluor White. Sporangia belonging to Chytridiomycota, filamentous fungi, yeast-like growth forms, and conidia of aquatic hyphomycetes are documented. (A) germinating zoospores. (B, C, D, H, O, Q) different kinds of observed fungal hyphae without clamps, partly melanized (H and O). (D) small, yeast-like growth forms. (E) potential resting spore (chytrid). (F) spore or sporangium. (C, G, I, J, L, M, P, Q) sporangia of different species of Chytridiomycota, where (J) resembles a typical Rhizophydium sporangium and (P) resembles Chytridiomycetes. (K) spore attached to filaments resembles a morphology similar to species of Glomeromycota or Zygomycetes. (N) typical tetraradiate conidia of an aquatic hyphomycete. (I, Q) mycoparasites of sporangia and fungal filaments. Bar = 100 µm.
Figure 3.
QPCR results showing fungal and bacterial succession on and surrounding pollen.
Absolute copy numbers of bacterial and fungal ribosomal genes of treatments (ST = Lake Stechlin and Grosse Fuchskuhle basins: NE = Northeast, SW = Southwest) determined by qPCR for the course of the experiment. Size fractionation made it possible to split the results into two subcategories: free-living and particle associated microorganism. Median with standard deviation is shown (n = 3).
Table 1.
Results of two-way ANOVA on ribosomal copy numbers of fungi and bacteria in particular lake types.
Table 2.
Results of two-way ANOVA on total molecular quantities of bacteria and fungi.
Figure 4.
Phylogenetic tree of environmental fungal sequences found during the experiment.
Maximum likelihood tree of all fungal and fungal-like ribosomal LSU sequences obtained by clone libraries and DGGE bands of all three treatments during the course of the pollen experiment (bold letters). Only resample values above 75 based on 1000 calculations for all full-length sequences are given. Partial sequences were added to the base tree by parsimony. Additional information for unique clusters of a certain treatment or phase of degradation is indicated. Fungal-like sequences were derived from the primer tests (see Material S1).
Figure 5.
Distribution of fungal taxa across treatments and size fractions.
Summary of recovered sequences. (A) Compiled data from Figure? 3 summarizes the distribution of fungal phyla and their occurrence during the experiment across treatments. (B) Summarizes the phylogenetic distribution of clones obtained for size-fraction analysis of Lake Stechlin treatment (ST) and the corresponding origin (FL or PA).
Figure 6.
Fungal and bacterial community ecology analysis based on molecular fingerprints.
NMDS plots based on distance matrices of bacterial (A) and fungal (B) DGGE patterns. Ellipses were based on standard deviations around the centroids of the corresponding categories (treatments/size fraction). Non-overlapping ellipses can be considered significantly separated groups (Oksanen et al., 2011). Significant environmental variables were plotted as arrowheads into the NMDS plots. (Stress values: Bacteria = 0.21, Fungi = 0.19).
Table 3.
Average ribosomal B∶F ratio of the experimental incubations.