A new method for the estimation of sinking particle fluxes from measurements of the particle size distribution, average sinking velocity, and carbon content

Andrew M. P. McDonnell, Ken O. Buesseler

Limnol. Oceanogr. Methods 10:329-346 (2012) | DOI: 10.4319/lom.2012.10.329

ABSTRACT: We describe a new method for estimating sinking particulate carbon fluxes at high spatial and temporal resolutions from measurements of the particle concentration size distribution taken with an in situ camera system, in this case an autonomous video plankton recorder (VPR). Paired measurements of polyacrylamide gel traps and the VPR result in depth- and size-resolved parameterizations of the average sinking velocity, which enable the estimation of the flux size distribution from the concentration size distribution. Comparisons between the gel traps and the bulk carbon flux allows for the parameterization of the particle carbon content as a function of size. Together, these parameterizations permit the estimation of carbon fluxes from high-resolution VPR surveys. This method enables greater spatial, vertical, and temporal resolution of flux measurements beyond what is possible with conventional sediment traps. We tested this method in the Sargasso Sea and found that it was capable of accurately reproducing the fluxes measured in sediment traps while offering substantial improvement in the accuracy of the estimated fluxes compared to previous global and regional parameterizations. Our results point to the importance of local calibrations of the average sinking velocity and particle carbon content when estimating carbon fluxes from measurement of the concentration size distribution. This method holds important oceanographic potential for elucidating regional or basin scale carbon flows and providing new mechanistic insights into the function of the biological pump.