Land cover and nutrient enrichment regulates low?molecular weight dissolved organic matter turnover in freshwater ecosystems

Dissolved organic matter (DOM) is a complex mixture of carbon-containing compounds. The low-molecular weight (LMW) fraction constitutes thousands different compounds and represents substantial proportion DOM in aquatic ecosystems. turnover rates this LMW can be extremely high. Due to the challenges measuring pool at molecular scale, comparatively little known fate lotic systems. This study addresses knowledge gap, investigating microbial processing across 45 sites representing range physicochemical gradients dominant land covers United Kingdom. Radioisotope tracers dissolved carbon (DOC) (glucose), nitrogen (DON) (amino acid mixture), phosphorus (DOP) (glucose-6-phosphate), soluble reactive (SRP, measured as orthophosphate) were used measure uptake river waters. amount biodegradation varied between components (DON ? DOC > DOP), with rate all three increasing along gradient N P enrichment sites. Conversely, SRP decreased same gradient. was ascribed preferential utilization DOP over SRP. Dominant cover had significant effect on use resource, due its control nutrient within catchments. We conclude that waters will lead further removal from water column, increased growth, decrease stream oxygen saturation, exacerbating effects eutrophication rivers.