Drivers of stream-microbial cycling and greenhouse gas dynamics across a land-use gradient

Catchment land-use has multiple impacts on streams affecting water quality, organic matter quantity and microbial community structure and function, which are key drivers of biogeochemical cycling and greenhouse gas fluxes. While previous studies have examined effects of land-use on stream greenhouse gas emissions, few have considered these together with microbial community structure and function or the connectivity between streams, their sediments and nearby riparian zones. Here, we examined microbial communities, dissolved organic carbon quantity and quality, and nutrient concentrations as drivers of greenhouse gas fluxes in headwater streams. We investigated potential greenhouse gas fluxes from streambed sediments and adjacent riparian zone sediments, as well as in-situ, surface water greenhouse gas concentrations, in 16 headwater streams across a land use gradient (categorised by percent agriculture, residential, industrial, and human development) in Massachusetts, USA. We found that riparian and streambed sediments at paired locations had different responses to land-use and that different greenhouse gases had different responses to land-use diversity. This work underscores the importance of combining microbial and biogeochemical measurements, especially in highly connected and complex systems that experience human-driven impacts across scales, to further understanding of whole corridor greenhouse gas fluxes.