The Effect of Extracellular Polymeric Substances on Aggregate Deformation in Turbulent Shear*

Carbon sequestration in marine environments is greatly facilitated by the aggregation of organic material into marine snow particles. The cohesiveness of this material is primarily fueled by extracellular polymeric substances (EPS), which are sticky, gel-like biopolymers composed of polysaccharides and proteins secreted by microorganisms. This research clarifies the crucial function of EPS in marine snow dynamics by analyzing these aggregates' mechanical characteristics and stability. Here, we examine the deformation behavior of marine aggregates containing EPS as they are exposed to turbulent shear using sophisticated turbulent flow facilities. We exposed aggregates and biopolymer particles ranging in size from 1 mm to 1 cm to turbulent flow with dissipation rates of ε = 10^-8  W/kg and higher and tracked their motion, size, and shape with a high-speed camera. By measuring shear-induced deformation and particle settling velocities, we determined that turbulence exposure significantly impacts the transport properties of these organic particles. These research findings offer new knowledge about particle transport and carbon cycling in aquatic systems, critical to improving environmental monitoring, reducing pollution, and sequestering carbon.