Journal
ELEMENTA-SCIENCE OF THE ANTHROPOCENE
Volume 9, Issue 1, Pages -Publisher
UNIV CALIFORNIA PRESS
DOI: 10.1525/elementa.2020.00122
Keywords
Biological carbon pump; Ocean Station Papa; Sediment traps; Carbon flux; Particle size distribution; Swimmers
Funding
- NASA EXPORTS program [80NSSC17K0662]
- EXPORTS [80NSSC17K568, 80NSSC17K0555]
- CRBN
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Comprehensive field observations characterized the biological carbon pump and proposed a new method to correct sample contamination. The study found generally low fluxes of sinking organic carbon, with decreasing particle sizes and potential trap bias. There was a tight coupling between production and recycling in the ocean at Station P, indicating stable overall biological carbon pump efficiency.
Comprehensive field observations characterizing the biological carbon pump (BCP) provide the foundation needed to constrain mechanistic models of downward particulate organic carbon (POC) flux in the ocean. Sediment traps were deployed three times during the EXport Processes in the Ocean from RemoTe Sensing campaign at Ocean Station Papa in August-September 2018. We propose a new method to correct sediment trap sample contamination by zooplankton swimmers. We consider the advantages of polyacrylamide gel collectors to constrain swimmer influence and estimate the magnitude of possible trap biases. Measured sediment trap fluxes of thorium-234 are compared to water column measurements to assess trap performance and estimate the possible magnitude of fluxes by vertically migrating zooplankton that bypassed traps. We found generally low fluxes of sinking POC (1.38 +/- 0.77 mmol C m(-2 )d(-1) at 100 m, n = 9) that included high and variable contributions by rare, large particles. Sinking particle sizes generally decreased between 100 and 335 m. Measured 234 Th fluxes were smaller than water column 234 Th fluxes by a factor of approximately 3. Much of this difference was consistent with trap undersampling of both small (<32 mu m) and rare, large particles (>1 mm) and with zooplankton active migrant fluxes. The fraction of net primary production exported below the euphotic zone (0.1% light level; Ez-ratio = 0.10 +/- 0.06; ratio uncertainties are propagated from measurements with n = 7-9) was consistent with prior, late summer studies at Station P, as was the fraction of material exported to 100 m below the base of the euphotic zone (T-100, 0.55 +/- 0.35). While both the Ez-ratio and T-100 parameters varied weekly, their product, which we interpret as overall BCP efficiency, was remarkably stable (0.055 +/- 0.010), suggesting a tight coupling between production and recycling at Station P.
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