TOMATO Biodegradation experiment - 16S and ITS rRNA Illumina Sequencing

Inputs of terrestrial dissolved organic matter (tDOM) in aquatic systems have increased over the past decades. This is due to various factors, such as land use intensification, changes in climate, hydrology, and changes in tDOM solubility. The current climate change scenario predicts an increase in the frequency and intensity of extreme rainfall events, even in the Mediterranean region, where overall precipitation is predicted to decrease. These events, when they occur after a dry period may erode the soil from the surrounding catchment and result in the pulsed exports of tDOM that likely influence the food-web structure and functioning of freshwater and marine ecosystems. Since, together with photooxidation, tDOM remineralization by microbes is the main sink for tDOM in aquatic ecosystems, we need to elucidate the respective importance of bacteria and fungi in tDOM biodegradation in fresh- and marine waters, which presently remains unresolved.On the other hand, the increases in tDOM will likely lead to an increase in humic substances that would hamper light penetration in the water column. This process, called brownification, may affect phytoplankton biomass and productivity, indirectly inducing carbon limitation in heterotrophic microbial communities and therefore affecting organic matter cycling through the microbial loop. The interactions between terrestrial subsidies and the size structure of consumers may play a key role in aquatic productivity, food-web structure, and energy transfers. The link between microbial community composition and ecosystem functioning is widely accepted and it is known that aquatic prokaryotic communities with contrasted structures differ in their degradation of tDOM. Degradation of DOM is carried out by phylogenetically diverse communities, whose composition is affected by the quality and quantity of DOM. Inputs of tDOM in aquatic ecosystems can be considered as disturbances with possible consequences on the metabolism and composition of the microbial community. Different trajectories can be proposed for the bacterial community in response to this disturbance. The type of trajectory and the resilience of the ecosystems can be potentially greatly different between freshwater and marine water ecosystems, depending on the functional redundancy of the bacterial community.At the interface of biogeochemistry and ecology, TOMATO (Response of aquatic microbes to inputs of Terrestrial Organic MATter from different Origins) project brings together specialists of marine, freshwater, and terrestrial ecosystems. This project will use mesocosms experiments to address the following main objectives:(1) Compare the responses in freshwater and marine water ecosystems to the inputs of tDOM from two different origins (manure amendment and peatland).(2) Describe the modification in structure and functionalities of microbial communities using molecular approaches in parallel to the biodegradation of tDOM.(3)Determine the resilience of those communities after a disturbance.