The flow of terrigenous organic matter (tOM) through aquatic ecosystems is a significant and increasing component of the global C cycle. This flux is controlled by regional climate, soil type, vegetation and land use; the fraction of tOM that ultimately reaches the ocean depends upon additional biotic and abiotic processes along the land-sea continuum. The relative importance and future evolution of these processes remain poorly understood – “many of the key processes relevant to decomposition of tOM are missing in models… despite their vulnerability to warming and land use change” (Ciais et al., 2013). This issue is acute for the UK Earth System Model (ESM), whose land surface model (JULES) transfers water but not tOM to the ocean, and whose marine ecosystem model (MEDUSA) contains no dissolved organic carbon (DOC) cycling.
LOCATE will integrate knowledge and skills across NERC terrestrial, freshwater and marine research centres to transform the UK’s ability to measure, model and predict land-ocean tOM fluxes in a changing environment. It will allow next-generation biogeochemical models to explore how climate change and land management decisions will influence the global C cycle.
Conceptualising, parameterising and validating such models requires understanding of (1) the spatial and temporal variability of contemporary fluvial tOM fluxes and their macromolecular characteristics, (2) the processes that influence the fate of tOM, and (3) how these fluxes and controlling processes will change in the future. LOCATE will address this need through an ambitious observational, experimental, and modelling programme focussed at the freshwater-seawater interface in locations throughout Great Britain (GB). GB has significant gradients in soil C content and land use, ranging from internationally-significant peatlands (Fig. 1) to agricultural lowlands on mineral soils, and thus serves as a useful model system for temperate systems worldwide. It also has long-term river flow monitoring infrastructure and extensive archives which LOCATE will build on. In addition, the UK has extensive datasets, monitoring networks and aligned programmes focussed on other aspects of the C cycle which will allow the conclusions of this work to be viewed in the context of other C fluxes (e.g. anthropogenic CO2 emissions).