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Carbon Flux Explorer optical assessment of C, N and P fluxes

  • Author(s): Bourne, HL
  • Bishop, JKB
  • Wood, TJ
  • Loew, TJ
  • Liu, Y
  • et al.

Published Web Location

http://dx.doi.org/10.5194/bg-16-1249-2019
No data is associated with this publication.
Abstract

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

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