The main objective of the project is to study the production of dissolved organic matter by the marine biota, the formation of mucilages from this DOM and the degradation steps it undergoes.
The objectives will be accomplished through the following :
1. Field work during which samples will be taken in the mouths of the rivers and in the gulf of Trieste, to monitor the nutrients inputs, and to follow the biological production and its consequences in term of particulate carbon fluxes and dissolved organic matter production. These cruises will be organised at three different periods of the year (May, end of June, September) to catch the periods of primary production, appearance of mucilages and degradation of aggregates. Nutrients and chlorophyll monitoring in the mouths of the river will be performed with a higher frequency (about each month) to get a representation of the yearly variability. During the main cruises, will be measured species determination, pigments, POC, DOC, nutrients, bacterial biomass and activity. On limited samples will be performed a molecular determination of biomarkers and a separation of the colloidal fraction (analysed the same way). Sediment traps will be deployed by sequences during the programme.
Sediment cores will be taken to measure the accumulation of organic matter and study the degradation processes occurring after burial.
2. Laboratory experiments : Besides the field work, laboratory experiments will be performed. Cultures of selected planktonic species, known to have a high yield in DOM excretion, will be done, the nutrients supply being controlled in order to simulate high sudden inputs and mis-equilibrated inputs (Variable N/P ratio). During the experiments, POC, DOC, TDN (DON), pigments, molecules identification and growing rate will be monitored.
Another kind of experiments will be done. Dissolved organic matter from extracellular release and accumulated aggregates (mucilages) will be degraded by bacteria under controlled conditions. These experiments will be done together with identification and growing of natural populations. The purpose of these experiments is to check the ability of bacteria to adapt to this kind of material and perform its degradation. The enzymatic activity of bacteria and the possible transfer of plasmids will be measured.
Funding SchemeCSC - Cost-sharing contracts
06238 Villefranche Sur Mer
66651 Banyuls Sur Mer