Rain-fed streams dilute inorganic nutrients but subsidise organic-matter-associated nutrients in coastal waters of the northeast Pacific Ocean

Abstract. In coastal regions, rivers and streams may be important sources of nutrients limiting to primary production in marine waters; however, sampling is still rarely conducted across the land-to-ocean aquatic continuum, precluding conclusions from being drawn about connectivity between freshwater systems. Here we use a more-than-4-year dataset (2014–2018) (nitrogen, phosphorus, silica, iron) dissolved organic carbon spanning draining watersheds nearshore surface waters along Central Coast British Columbia, Canada, at heart North Pacific temperate rainforest region. Mean N:Si:P ratios were 5:20:1 (P:Fe = 1:67) 6:11:1, respectively, showing relative consistency land–ocean interface but deviation extended Redfield ratio. Inorganic nutrient concentrations (NO3-+NO2-, PO43-, Si(OH)4) fresh less than receiving environment, indicating that inputs this region little importance – or even diluted pool readily available inorganic waters. Conversely, increased organic-matter-associated nutrients, namely nitrogen iron. The organic-matter-rich landscapes yielded globally significant quantities (304–381 kg km?2 yr?1) iron (463–596 yr?1), thus acting as potentially both offshore These exports subsidise heterotrophic microbial communities capable directly consuming remineralising these compensating for dilution by inputs. We highlight need better understand limitation concerted research efforts study spatial temporal dynamism northeast coast.