Osmotolerance is a driver of microbial carbon processes in the Elbe estuary

Estuaries, lower river areas that merge into oceans, play a large role in Earth's carbon cycle. Estuaries store carbon and manage greenhouse gases, exchanging carbon between land, water, and the air. As carbon travels down estuaries, it is processed by free-living and particle-associated microbes. We explore the relationship between environmental conditions and present and expressed genes. Based on gene profiles, methane concentrations in the water column may be related to the abundance of sinking particles, while suspended particles are linked to growth and energy acquisition. Therefore, the balance of suspended vs. sinking particles is important in highly turbid estuaries, like the Elbe estuary, where urban activities affect greenhouse gas emissions and salinity intrusions. Dredging often tips the balance toward sinking particles and therefore increased greenhouse gas emissions. Our study thereby informs future policy decisions and the impact these decisions will have on our future climate.