The aim of the project
The aim of the project is detection of microbial food web structure in different marine environment, as well as its responses to environmental changes, primarily to increase in temperature and phosphorus supply. Responses of the microbial food web will be studied at multiple levels:1. Quantitative changes in the values of certain parameters (e.g., increase or decrease the number, biomass and/or production of certain groups of organisms). 2. Qualitative/structural changes include modifications in the composition, size structure or numerical relationships between individual taxonomic or trophic groups within microbial food web. 3. Functional changes include trophic relationships within the microbial food web, production, respiration rate and carbon flux through the micorbial food web, bacterial growth efficiency (BGE) and bacterial carbon demand (BCD), mechanisms of control of individual trophic groups (“bottom-up” vs. “top-down” control), changes in seasonal cycles and community stability (in the terms of temporal biomass stability, bacterial production stability and stability of community structure).
Topic 1 objectives: The structure of microbial food web
Determine the microbial community structure on spatial (different marine environments), trophic (trophic gradient) and temporal (intra- and inter-annual) scale; and possibly on temperature and salinity scale (cross-comparisons between natural systems under different temperature and salinity regimes). Some features of the microbial community structure will be particularly focused on:
1. Ratio between autotrophic and heterotrophic picoplankton biomass
2. Ratio between pico-prokaryotic and pico-eukaryotic autotrophs biomass
3. Ratio between Synechococcus and Prochlorococcus abundance and biomass
4. Ratio between HNA and LNA bacteria
5. Distribution and contribution of Aerobic Anoxygenic Phototrophs (AAP) in microbial community
6. Relationship between different groups within microbial community
Topic 2 objectives: Bacterial carbon flux
Determine the functional features of microbial food web:
1. Quantification of carbon flux through the microbial food web (on spatial, trophic and seasonal scale)
2. Quantification of grazing vs. viral-lysis in picoplankton mortality
3. Determine relative importance of top-down and bottom-up control
Topic 3 objectives: Impact of temperature increase and phosphate addition in experimental conditions
Quantification of the changes in microbial carbon flux, bacterial respiration (BR), bacterial growth efficiency (BGE) and bacterial carbon demand (BCD) in conditions of phosphate addition and/or temperature increase.
Expected results of the project:
1. Better understanding the structural and functional responses of microbial community to environmetal conditions through the comparison between natural systems under different nutrients, temperature and salinity regimes, and through the following the changes in these responses on spatial, trophic and temporal (seasonal and inter-annual) scales.
2. Determination of some features of the microbial community structure that could serve as potential indicators of the cahanges and disturbances in the marine ecosystems (for example, contribution of different trophic and/or functional groups in community, and ratios between them).
3. Better understanding the effect of global warming on carbon flux through the microbial food web which may have significant consequences on the overall production in marine ecosystems, and on the fate of biogenic carbon (respiration vs. incorporation into biomass).
On what issues we expect that this research will give contribution?
This Project can contribute in developing of specific microbial indicators of the changes and disturbances in the marine ecosystems. Many scientists believe that marine microbial science can provide the foundation for marine ecosystem forecasting, prediction and remediation. This is particularly crucial in light of the capacity of microbes to function as indicators (and drivers) of change in the ocean. In the big picture, a better understanding of the role of microorganisms in ocean ecosystems will allow for improved monitoring of the overall health of the ocean and a more nuanced grasp of the ocean’s role in regulating and responding to changes in global climate and other critical ecosystem processes. Further, understanding the processes in micoobial food web, in the light of global warming, can help in forecasting: (1) how global warming might affect the biological productivity of marine ecosystems and carbon transfer among trophic compartments (in terms of their efficiencies and final yields) critical for maintenance of fisheries stocks; and (2) what the fate of biogenic carbon and its sequestration in the ocean we can expect, which defines the role of the sea in global warming.