Freshwater systems are a key component of the global carbon cycle, transporting allochthonous (terrestrial) carbon to the sea. Such systems are not merely conduits between terrestrial and marine environments, but are themselves a dynamic reservoir, in which carbon can be incorporated into biota, sequestered in sediments, or effluxed to the atmosphere. Understanding the turnover of carbon in freshwater systems is a critical step, not only in completing our picture of global carbon biogeochemistry, but because of the effects of accelerating climatic changes. For example, terrestrial DOC, previously stored in soil stocks, is released with increased temperature, precipitation and frequency of flood events. Determining and quantifying the source, age and fate of freshwater carbon is therefore an important research goal. Such investigations demand the integration of multiple analytical techniques, of which radiocarbon (14C) is a particularly useful tool. Along with crucial chronological information, 14C allows ultra-sensitive discrimination of different end members. These include including allochthonous versus autochthonous (derived from primary production) carbon, plus the quantification of modern, old and fossil carbon in freshwater systems. Current applications include analysis of temporal and spatial variation in dissolved inorganic carbon, dissolved organic carbon, and particulate organic matter, as well as changes over time as a result of allochthonous inputs. Research advances are following from the recent development of novel analytical methods such as stepped combustion opening many new possibilities to examine freshwater carbon dynamics. Furthermore, advances in sensor technology have made automated high frequency sampling possible allowing production of more detailed time series. We invite papers which address the themes of this session, particularly those following the themes below:
-Determining the source and age of terrestrial carbon in a freshwater system
-Quantifying the terrestrial carbon loading into lakes, or CO2 flux to the atmosphere
-Assessing the residence/turnover time of carbon in freshwater systems
-Identifying the fate of terrestrial carbon in a freshwater system: buried in sediments, released downstream to the sea or expelled as a gas to the atmosphere?
-Measurement methods in sediments and water, including applications and development of novel sensor technologies.
- Tracing carbon pathways in freshwater food webs