Searching for the stream's biogeochemical "heartbeat": Patterns of temporal variation in nutrient spiralling

Over the past three decades, the nutrient spiralling concept, which combines the processes of nutrient uptake and hydrologic transport, has provided an excellent framework to advance research on biogeochemical processing in streams. Even though streams are highly dynamic ecosystems, few studies have addressed temporal variation in stream nutrient spiralling. Methodological constraints do hardly allow to measure nutrient spiralling at extreme flow conditions, such as floods and droughts. However, information on temporal variation of nutrient spiralling contributes to an understanding of stream biogeochemistry during the most biologically active periods. Each stream is characterized by gradual and abrupt temporal changes in environmental factors that affect the biological compartments responsible for nutrient uptake. We expect nutrient spiralling to respond to these changes and, thus, to exhibit a characteristic biogeochemical “heartbeat” that will be constrained by the stream's environmental setting. In this presentation we provide evidence supporting this hypothesis by combining results from previous studies with those from a four-year-long ongoing study in Mediterranean streams. We use this dataset to explore the relationship between variability of nutrient spiralling and environmental drivers over different temporal scales, ranging from diurnal to inter-annual.