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  1. Abstract. The magnitude and controls of particulate carbon exported from surface watersand its remineralization at depth are poorly constrained. The Carbon FluxExplorer (CFE), a Lagrangian float-deployed imaging sediment trap, has beendesigned to optically measure the hourly variations of particle flux tokilometer depths for months to seasons while relaying data in near-real timeto shore via satellite without attending ships. The main optical proxy forparticle load recorded by the CFE, volume attenuance (VA; units ofmATN cm2), while rigorously defined and highly precise, has not beenrobustly calibrated in terms of particulate organic carbon (POC), nitrogen(PN) and phosphorus (PP). In this study, a novel 3-D-printed particle samplerusing cutting edge additive manufacturing was developed and integrated withthe CFE. Two such modified floats (CFE-Cals) were deployed a total of15 times for 18–24 h periods to gain calibration imagery and samples atdepths near 150 m in four contrasting productivity environments during theJune 2017 California Current Ecosystem Long-Term Ecological Research (LTER)process study. Regression slopes for VA : POC and VA : PN (unitsmATN cm2: mmol; R2, n, p value in parentheses) were1.01×104 (0.86, 12, < 0.001) and 1.01×105(0.86, 15, < 0.001), respectively, and were not sensitive toparticle size classes or the contrasting environments encountered. PP was notwell correlated with VA, reflecting the high labilitymore »of P relative to C andN. The volume attenuance flux (VAF) to POC flux calibration is compared toprevious estimates.

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