Bertilsson, S., Hornak, K., McMahon, K.D., Simek, K., Pernthaler, J.

1. Exploring transient phytoplankton spring blooms across lakes to understand the significance and control of temporal patterns in freshwater bacteria Bertilsson, S., Hornak, K., McMahon, K.D., Simek, K., Pernthaler, J.

2. Lake Erken Oct 2008 International workshop of the dynamic properties of Aquatic Microbial Communities

3. External inputs -Hydrological inflow -Precipitation -Mixing / Internal re-distribution Growth & Competition -Electron donors -organic -inorganic -Electron acceptors -Solar radiation -Nutrients -phosphorus -nitrogen -trace elements • Mortality • Microzooplankton • grazing • -Protozoan grazing • -Viral lysis • Export • -Hydrological outflow • -Sedimentation • -Aerosolization Microbial Community/Population Gain Loss Cryptic ecological drivers -pH -phototoxicity -temperature -toxic compounds -particulate matter/surfaces Modified from Shade et al., 2009, The ISME Journal

4. By concerted high-frequency sampling and analysis of microbial variables, functional traits and driver variables in multiple well-studied freshwater lakes, we will address a number of central questions in aquatic microbial ecology and aquatic ecosystem response to environmental change.

6. TIMING: What triggers and terminates (clonal) spring blooms of microorganisms across different lakes? When does it happen (relative and absolute timing)? DRIVERS: What is the role of vertical spatial structure (and associated chemistry), solar radiation and predation pressure? Will the trajectory and pace of community change vary among the studied lakes and how does this relate to climatic region and lake size (buffering capacity). INTERACTIONS: Is there synchrony in spring microbial community succession and can contrasting growth strategies be identified among populations (stable/dynamic)? Are there links between individual bacterial populations and phytoplankton

7. An Array of Microbial Variables (using standardized methods) • Bacterial community composition using ARISA – McMahon • Bacterial community composition using barcoded 454 sequencing– Bertilsson • Bacterial community composition by FISH – Pernthaler • Viral counts – Simek • Quantitative assessment of specific group of bacteria: • -Beta-proteobacterial populations Simek-FISH, Reverse Line Blot-Jezbera • -Actinobacterial populations McMahon-QPCR, Pernthaler-FISH • -Alphaproteobacteria populations SAR11: Bertilsson-QPCR, Pernthaler-FISH • -Flavobacteria populations Pernthaler-FISH; Bertilsson-QPCR/T-RFLP • Bacterial numbers and biomass – All groups • Bacterial production (leucine incorporation)-All groups • Parameters that may vary among sites: • Zooplankton • Phytoplankton • Heterotrophic nanoflagellates • BrdU-FISH probing of replicating bacterial groups temperature (vertically resolved), PAR and precipitation, chlorophyll-a, DOC, absorbance/water color, nutrients (TP, TRP, NH4, NO3, Si) and oxygen

8. The lakes

9. Lake Zürich

10. Lake Erken Stratification Ice

11. Lake Mendota... (the image has nothing to do with the actual UW-CL sampling vessels...)

12. Water column seasonality in Erken (2008/2009) Chl a Chl a

13. AVERAGE LAKE SURFACE WATER BACTERIAL COMMUNITY COMPOSITION (390.000 rRNA sequences for 70 lakewater samples)

14. Abundance patterns of bacterial populations: -Epilinnetic water samples Grouped by phylogeny Grouped by abudnace pattern

15. Correlating bacterial populations to environmental variables r-value Actino Bacteroidetes Cyano Alpha Beta Gamma Verrucomicrobia