As primary producers, algae and cyanobacteria are a key component in limnic ecosystems. Their activity cannot be separated from other components of the aquatic microbial community. Despite the fact that there are multiple metabolic and functional interactions between algae and bacteria, most of the current studies investigate these groups separately with little communication between the specialists focusing on either of these groups. To bridge this gap, we propose joint field experiments on a freshwater Římov Reservoir investigating the interactions of phytoplankton and bacterioplankton during the diurnal cycle and on a spatial gradient. In the Římov Reservoir, pronounced gradients in environmental conditions develop every year. In summer, the upper transition zone is characterized as eutrophic, with a high primary production and cyanobacterial blooms are common. On the contrary, at the dam, phytoplankton biomass is low and their production is usually nutrient limited. The water column is thermally stratified and thermocline often coincides with subsurface phytoplankton peaks and metalimnetic oxygen minima, that provides opportunities to explore microbial interactions of different microhabitats. The aim is to enhance the current understanding of carbon fluxes through the microbial food webs.
In a series of diurnal field measurements and lab-based, whole-community manipulation experiments, we want to address the following questions:
Are primary producers stimulated by particular bacterial groups?
Does bacterial respiration affect standard measurements of primary production?
Which bacterial groups utilize freshly produced DOC (autochtonous) and which utilize the old (allochtonous) carbon?
What are the growth rates of individual microbial groups and which groups are stimulated by light?
What is the efficiency of the carbon conversion between the different parts of the microbial loop?
What is the effect of light on the utilization of phytoplankton-derived organic matter by bacteria?
Do microbial interactions differ within the reservoir and what are the most influential factors?
Leading co-ordinator: Hans-Peter Grossart, Leibnitz Institute for Freshwater Research, Germany
Local co-ordinator - Michal Koblížek, Centre Algatech, Inst. of Microbiology, Třeboň
Local organizing team: Petr Znachor, Inst. of Hydrobiology České Budějovice
Kasia Piwosz, Centre Algatech, Inst. of Microbiology, Třeboň
Number of participants: 15 - 20
Field experiments: Řimov drinking water reservoir - field station of the Hydrobiology Institute in České Budějovice
Lab experiments: Centre Algatech, Institute of Microbiology in Třeboň and the Hydrobiology Institute in České Budějovice
Data management: Centre Algatech, Institute of Microbiology in Třeboň
Field measurements at Řimov
Diurnal sampling every 4-6 hours over 48 h. The water samples will be shipped to Třeboň/ČB or processed on site at the field station. At the start of the experiment, samples from different sites will be collected. All samples will be incubated at the dam.
In situ/on site measurements and incubation:
Collecting samples for:
Manipulation experiment in Centre Algatech in Třeboň?
Water will be collected on the first day from surface layer of the Řimov reservoir. It will be filtered through a 1 µm filter to remove grazers. Sampling every 12 hrs over 3-5 days. Incubation in a light/dark cycle and in the dark.
Measurements and incubation:
Collecting samples for:
Centre Algatech, Třeboň:
- 2x Zeiss Axiovision microscopes equipped with Hamamatsu EM-CCD camera
- Flow cytometer Apogee A50
- Cell sorter BD Influx, blue laser
- HPLC for pigment analyses
- Equipped radioactive lab
- Various fluorometers for field measurements
- YSI CTD probe
- Water sampler
- MIMS system for oxygen measurements???
- DNA/RNA extraction
- PCR, qPCR
- Hybridization oven (FISH techniques)
The IHB Field station is located at walking distance (200 m) from the dam of the Římov Reservoir and is fully equipped for routine measurement and basic plankton analyses. The infrastructure includes sheltered yard with a big garage, small laboratory, kitchen, sleeping room for 6 people, shower, toilet, and all equipment necessary for sampling and data collection, e.g. boats, engines, samplers, automated gauging station providing high resolution daily records of light, temperature, wind velocity and stratification
IHB laboratories in České Budějovice (20 minutes by car from the reservoir):
- 3x fluorescence microscopes: Olympus AX70, BX60, NIkon i90, all equipped with cameras and image analysis sytems (NIS Elemnts).
- 2x inverted microscope: Olympus IMT1 and Olympus IX70 (fluorescence)
- Equippment for work with radioactivity: fume hood, filtration manifold and other filtration devices