GelCam: Visualizing sinking particle flux via a polyacrylamide gel-based sediment trap

Sinking particles play a key role in the biological carbon pump. While previous studies have analyzed particulate carbon flux over timescales of days to years, few have been able to resolve flux variability on shorter, hourly scales at multiple depths simultaneously. This study uses an array of upward-facing cameras, built from off-the-shelf components for under $500 each, to visualize particle fluxes at multiple depths during the EXPORTS campaign in 2018 in the North Pacific. This manuscript is the first comprehensive description of this tool, called GelCam, which captures a time-lapse image sequence at 20-min intervals of particles that settle into a polyacrylamide gel layer located at the base of a sediment trap tube. Methods are described for the design and post-processing pipeline, in addition to two proxy methods for estimating the total particulate organic carbon flux. The GelCam-derived fluxes modeled from individual particle images show strong agreement with the ground-truth data obtained from coincident trap measurements. This approach helps address the need for accessible, open-source tools to more broadly observe and quantify the role of episodic particle flux events across the global oceans.