Seawater stores as much carbon in the form of dissolved organic matter (DOM) as there is CO2 in the atmosphere. Over a period of just 50 years (from 1960 to 2010) global oceanic oxygen reserves have been reduced by 2% and the anoxic waters have quadrupled, mainly due to anthropogenic global warming and eutrophication. Ocean deoxygenation leads to an expansion of oxygen minimum zones (OMZs), which contain higher concentrations of DOM (carbon and sulfur) than the oxygenated ocean. While there is no consensus about the reasons behind DOM sequestration in OMZs, it is well established that microbes are directly responsible for the production, degradation and recycling of marine DOM.

 

Recent advances in analytical chemistry characterize the DOM at the molecular level in unprecedented detail, revealing new insights into its source and history by Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR-MS). Current progress in sequencing technology can predict specific functions contributing to the molecular activity of microbial communities in environmental samples by metatranscriptomics. The synergistic coupling of FT-ICR-MS and metatranscriptomics is therefore of great importance to connect DOM cycling with microbial activities in OMZs, in order to measure the response of this major carbon reservoir to ocean deoxygenation and climate change.

 

In this DFG Emmy Noether Research project we aim to identify the effects of ocean deoxygenation on DOM sequestration due to interactions with microbial communities and the marine carbon and sulfur cycles.