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Concentration-discharge (C-Q) relationships of total suspended solids (TSS), total dissolved solids (TDS), particulate organic carbon (POC), and dissolved organic carbon (DOC) were investigated in the tributaries and main-stems of two mountainous river systems with distinct watershed characteristics (Eel and Umpqua rivers) in Northern California and central Oregon (USA). Power-law (C = a × Q b) fits to the data showed strong transport-limited behavior (b > 1) by TSS and POC, moderate transport limitation of DOC (b > 0.3) and chemostatic behavior (b < 0) by TDS in most streams. These contrasts led to significant compositional differences at varying discharge levels, with particle-bound constituents becoming increasingly important (relative abundances of 50% to >90%) at high-flow conditions. Organic carbon contents of TSS displayed marked decreases with discharge whereas they increased in TDS during high-flow conditions. Daily and cumulative material fluxes for different coastal streams were calculated using the C-Q relationships and showed that the delivery of transport-limited constituents, such as TSS and POC (and DOC to a lesser degree), was closely tied to high-discharge events and occurred primarily during the winter season. The coherence between winter fluxes and high wave-southerly wind conditions along the coast highlights how seasonal and inter-annual differences in fluvial discharge patterns affect the fate of land-derived materials delivered to coastal regions. 

Two oceanographic cruises were completed in September 2016 and August 2017 to investigate the distribution of particulate organic matter (POM) across the northeast Chukchi Shelf. Both periods were characterized by highly stratified conditions, with major contrasts in the distribution of regional water masses that impacted POM distributions. Overall, surface waters were characterized by low chlorophyll fluorescence (Chl Fl < 0.8 mg m⁻³) and particle beam attenuation (c_p < 0.3 m⁻¹) values, and low concentrations of particulate organic carbon (POC < 8 mmol m⁻³), chlorophyll and pheophytin (Chl + Pheo < 0.8 mg m⁻³), and suspended particulate matter (SPM ∼2 g m⁻³). Elevated Chl Fl and Chl + Pheo (∼2 mg m⁻³) values measured at mid‐depths below the pycnocline defined the subsurface chlorophyll maxima (SCM), which exhibited moderate POC (∼10 mmol m⁻³),c_p(∼0.4 m⁻¹) and SPM (∼3 g m⁻³). In contrast, deeper waters below the pycnocline were characterized by low Chl Fl and Chl + Pheo (∼0.7 mg m⁻³), highc_p(>1.5 m⁻¹) and SPM (>8 g m⁻³) and elevated POC (>10 mmol m⁻³). POM compositions from surface and SCM regions of the water column were consistent with contributions from active phytoplankton sources whereas samples from bottom waters were characterized by high Pheo/(Chl + Pheo) ratios (>0.4) indicative of altered phytoplankton detritus. Marked contrasts in POM were observed in both surface and middepth waters during both cruises. Increases in chlorophyll and POC consistent with enhanced productivity were measured in middepth waters during the September 2016 cruise following a period of downwelling‐favorable winds, and in surface waters during the August 2017 cruise following a period of upwelling‐favorable winds.