Climate change is predicted to result in increased precipitation and enhanced input of terrestrially derived dissolved organic carbon (DOC) to aquatic ecosystems in northern Europe. In freshwater systems one of the largest fluxes of carbon is from the pool of organic matter (DOM) into microorganisms. However, despite a wide interest in assessing the regulating factors of dissolved organic matter bioavailability, it is still to a large extent unknown what mechanisms that control the ability of microorganisms to utilize DOM. The aim of this research project is to investigate which factors that are most important for organic matter degradation in inland waters - diversity of the bacterial community or diversity of the organic compounds. Specifically we will investigate if bacterial utilization of DOM is affected by the chemodiversity of DOM, taxonomic diversity or functional diversity of the bacterial community respectively. The project is based on a field study where lakes differing in DOM quality and composition are sampled.
The DOM at the different sampling points will be isolated and characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) which offers ultrahigh mass resolving power and previously has been used for constructing organic fingerprints of DOM in the aquatic environment. Bacterial community composition and diversity is determined using illumina sequencing of the 16S rRNA gene whereas the functional diversity or metabolic capability will be investigated using metagenomics targeting genes involved in carbon degradation. Simultaneous use of mass spectrometry and metagenomics will give insights to the utilization of DOC in the natural environment and significantly increase the understanding of utilization of DOC by microorganisms in aquatic environments, which represent an important task in understanding the global carbon cycle.