CARAMBA · Unravelling the microbial carbon pump in the ocean: Linkage between gene expression and RDOM generation by marine bacteria (CARAMBA)

Unravelling the microbial carbon pump in the ocean: Linkage between gene expression and RDOM generation by marine bacteria (CARAMBA)

The increase of carbon dioxide (CO2) in the atmosphere due to human activities has consequences for global change that have sparked substantial interest in the study of the planetary carbon cycle. The ocean is one of the largest carbon reservoirs on Earth and therefore plays a key role in the global carbon cycle. At present, the ocean absorbs 30% of anthropogenic CO2. The ocean contains an amount of carbon in the form of oceanic dissolved organic matter (DOM; 660 Gt) similar to that in atmospheric CO2 (829 Gt). A net oxidation of only 1% of the seawater DOM pool in one year would be enough to produce a CO2 flux larger than that coming annually from fossil fuel combustion. Even though the importance of oceanic DOM for the global carbon cycles is well recognized, major gaps in our understanding of the chemical composition and the cycling of individual compounds persist. Bacteria play a key role in DOM processing in the ocean. For example, one half of carbon fixed by phytoplankton through photosynthesis, the main source of DOM in the ocean, are processed by bacteria. They use this DOM for respiration, thus transforming it back into CO2, or for production of new bacterial biomass that then enters the trophic web (i.e. is consumed by ciliates and flagellates that will be then grazed by higher trophic levels). However, it was only recently discovered that marine bacteria also release DOM. Part of bacterially-derived DOM is largely resistant to further utilization and persists in the ocean’s interior through thousands of years. This mechanism of carbon sequestration in the ocean mediated by bacteria is what we know as the microbial carbon pump. However, how and why marine bacteria produce DOM and why this DOM is not further degraded in the ocean is still under investigation, and getting the answers are essential to predict climate change effects: If all this pool of recalcitrant DOM was respired and the carbon released to the atmosphere, it would double the atmospheric CO2 inventory. The main objective of the CARAMBA project was to better understand the ultimate reasons, for bacterial DOM production and its persistence in the ocean. The specific objectives were to elucidate whether bacterial taxonomical composition affected DOM production and tis quality, and whether environmental conditions would affect the bioavailability of this produced DOM.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз