Marine particle dynamics : sinking velocities, size distributions, fluxes, and microbial degradation rates

• Main Author: McDonnell, Andrew M. P.
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology and Woods Hole Oceanographic Institution 2011
• Subjects: Sediment transport; Carbon cycle; Laurence M. Gould (Ship) Cruise LMG0901; Laurence M. Gould (Ship) Cruise LMG0902; Laurence M. Gould (Ship) Cruise LMG1001; Nathaniel B. Palmer (Ship) Cruise NBP1002; Antarctic; Antarctic Peninsula; Antarc*
• Online Access: https://hdl.handle.net/1912/4512

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2011 The sinking flux of particulate matter into the ocean interior is an oceanographic phenomenon that fuels much of the metabolic demand of the subsurface ocean and affects the distribution of carbon and other elements throughout the biosphere. In this thesis, I use a new suite of observations to study the dynamics of marine particulate matter at the contrasting sites of the subtropical Sargasso Sea near Bermuda and the waters above the continental shelf of the Western Antarctic Peninsula (WAP). An underwater digital camera system was employed to capture images of particles in the water column. The subsequent analysis of these images allowed for the determination of the particle concentration size distribution at high spatial, depth, and temporal resolutions. Drifting sediment traps were also deployed to assess both the bulk particle flux and determine the size distribution of the particle flux via image analysis of particles collected in polyacrylamide gel traps. The size distribution of the particle concentration and flux were then compared to calculate the average sinking velocity as a function of particle size. I found that the average sinking velocities of particles ranged from about 10-200 m d-1 and exhibited large variability with respect to location, depth, and date. Particles in the Sargasso Sea, which consisted primarily of small heterogeneous marine snow aggregates, sank more slowly than the rapidly sinking krill fecal pellets and diatom aggregates of the WAP. Moreover, the average sinking velocity did not follow a pattern of increasing velocities for the larger particles, a result contrary to what would be predicted from a simple formulation of Stokes’ Law. At each location, I derived a best-fit fractal correlation between the flux size distribution and the total carbon flux. The use of this relationship and ...