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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.
Lake Erken Oct 2008
International workshop of the dynamic properties of Aquatic Microbial Communities
External inputs
-Hydrological inflow
-Precipitation
-Mixing / Internal
re-distribution
Growth & Competition
-Electron donors
-organic
-inorganic
-Electron acceptors
-Solar radiation
-Nutrients
-phosphorus
-nitrogen
-trace elements
Gain
Microbial
Community/Population
Cryptic ecological drivers
-pH
-phototoxicity
-temperature
-toxic compounds
-particulate matter/surfaces
Loss
Mortality
-Microzooplankton
grazing
-Protozoan grazing
-Viral lysis
Export
-Hydrological outflow
-Sedimentation
-Aerosolization
Modified from Shade et al., 2009, The ISME Journal
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.
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
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
The lakes
Lakes
buoy
troph
Mendota, WI, USA
y
eu
Zurich, Switzerland
n
meso
Rimov, Czech Republic
n
Erken, Sweden
y
size
defining characteristics
39 km2, medium 24 m
Freezes, 5 yrs HRT
89km2, deep
136 m
Urban, 1.2 y HRT
43 m
Usually freeze, 100 d HRT
meso/eu 2.1 km2, deep
meso
depth
24 km2, medium 21 m
Usually freeze, 7.4 yrs HRT
Lake Zürich
Lake Erken
Lake Erken chlorophyll (µg/l)
20
18
16
14
12
10
8
6
4
2
0
Ice
Stratification
Lake Mendota...
(the image has nothing to do with the actual UW-CL sampling vessels...)
Water column seasonality in Erken (2008/2009)
Chl a
Chl a
AVERAGE LAKE SURFACE WATER BACTERIAL COMMUNITY COMPOSITION
(390.000 rRNA sequences for 70 lakewater samples)
Bacteroidetes
Chlamydiae
Cyanobacteria
TM7
Acidobacteria
OP11
OD1
Fusobacteria
Nitrospira
no_match
Gemmatimonadetes
Actinobacteria
Proteobacteria
Planctomycetes
Spirochaetes
OP10
Chloroflexi
Firmicutes
unclassified_Bacteria.
WS3
Deinococcus-Thermus
Thermomicrobia
Verrucomicrobia
Abundance patterns of bacterial populations:
-Epilinnetic water samples
Grouped by phylogeny
Grouped by abudnace pattern
Correlating bacterial populations to environmental variables
r-value
Actino
Bacteroidetes
Cyano
Alpha
Beta
Gamma
Verrucomicrobia