This cluster of papers focuses on the biogeochemical cycling of nutrients, particularly nitrogen and phosphorus, in the interface of terrestrial and aquatic ecosystems. It explores topics such as nutrient hot spots and hot moments, control of nitrogen and phosphorus export from watersheds, hyporheic flow and transport processes, agricultural impacts on water quality, and strategies for mitigating eutrophication. The research also delves into the effectiveness of riparian buffers, stream restoration, and watershed management in addressing nutrient pollution.