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Particle size and settling speed determine the rate of particulate mass transfer from the ocean surface to the sea bed. Turbulent shear in the ocean can act on large, faster-settling flocculated particles to break them into slower-settling primary particles or sub-aggregates. However, it is difficult to understand the disruption behavior of aggregates and their response to varying shear forces due to the complex ocean environment. A study was conducted to simulate the disruption behavior of marine aggregates in the mixed layer of the ocean. The breakup process was investigated by aggregating and disrupting flocs of bentonite clay particles in a rotating and oscillating cylindrical tank 10 cm in diameter filled with salt water. This laboratory tank, which operated based on an extension of Stokes’ second problem inside a cylinder, created laminar oscillating flow superimposed on a constant rotation. This motion allowed the bentonite particles to aggregate near the center of the tank but also exposed large aggregates to high shear forces near the wall. A high-speed camera system was used, along with particle tracking measurements and image processing techniques, to capture the breakup of the large particle aggregates and locate their radial position. The breakup response of large aggregates and the sizes of their daughter particles after breakup were quantified using the facility. The disruption strength of the aggregated particles is presented and discussed relative to their exposure to varying amounts of laminar shear. 

The fate of particulate matter in the ocean is determined in large part by its size and settling rate. Disaggregation, caused by turbulence-induced shear, acts to fracture or erode large particles into slower-settling sub-aggregates and primary particles. The strength and breakup response of organic marine aggregates (i.e. marine snow particles consisting of phytoplankton) is poorly understood, limiting our ability to accurately predict marine particle transport effects on the global carbon cycle. A study was conducted to enable the investigation of disaggregation effects on these organic marine particle aggregates. Due to the fragile nature of the Phytoplankton cells and their resulting aggregates, test facilities that do not rely on external sampling or pumps are required. A novel rolling aggregation tank was developed that can both aggregate phytoplankton cells under varying hydrodynamic conditions and then expose them to calibrated shear forces using laminar oscillating flow. The theory behind the operation of this tank is presented along with the necessary operating conditions to create stable regions within the tank where particle settling effects are minimal but shear is still representative of values expected in the open ocean. Phytoplankton was cultured in the laboratory to create simulated marine snow particles in the open ocean for disaggregation experiments. The procedure to calculate and track the shear-history of each aggregate is described and how the data generated from this facility will be used to quantify disaggregation parameters relevant for population balance modeling is discussed.