A low‐cost underwater particle tracking velocimetry system for measuring in situ particle flux and sedimentation rate in low‐turbulence environments

Abstract

We describe a low‐cost three‐dimensional underwater particle tracking velocimetry system to directly measure particle settling rate and flux in low‐turbulence aquatic environments. The system consists of two waterproof cameras that acquire stereoscopic videos of sinking particles at 48 frames s−1 over a tunable sampling volume of about 45 × 25 × 24 cm. A dedicated software package has been developed to allow evaluation of particle velocities, concentration and flux, but also of morphometric parameters such as particle area, sinking angle, shape irregularity, and density. Our method offers several advantages over traditional approaches, like sediment trap or expensive in situ camera systems: (1) it does not require beforehand particle collection and handling; (2) it is not subjected to sediment trap biases from turbulence, horizontal advection, or presence of swimmers, that may alter particulate load and flux; (3) the camera system enables faster data processing and flux computation at higher spatial resolution; (4) apart from the particle settling rates, the particle size distribution, and morphology is determined. We tested the camera system in Lake Stechlin (Germany) in low turbulence and mean flow, and analyzed the morphological properties and settling rates of particles to determine their sinking behavior. The particle flux assessed from conventional sediment trap measurements agreed well with that determined by our system. By this, the low‐cost approach demonstrated its reliability in low turbulence environments and a strong potential to provide new insights into particulate carbon transport in aquatic systems. Extension of the method to more turbulent and advective conditions is also discussed.

Summary of Experiments and Influencing Factors of Sediment Settling Velocity in Still Water

“…This approach yields improved statistical characteristics regarding particle size, settling velocity, and suspended particle density, thereby significantly reducing the uncertainty associated with settling velocity measurement. Nonetheless, PIV and PTV may encounter similar hydrodynamic deviations as sediment traps during particle collection, as the data are only acquired after the sediment column captures the particles [59]. Simoncelli [59] introduced a 3D-PTV method for determining the particle settling velocity.…”

“…Nonetheless, PIV and PTV may encounter similar hydrodynamic deviations as sediment traps during particle collection, as the data are only acquired after the sediment column captures the particles [59]. Simoncelli [59] introduced a 3D-PTV method for determining the particle settling velocity. In comparison to the PICS method, this alternative is more cost effective and simpler to purchase, assemble, and operate, offering enhanced automation.…”

Low-Cost, Deep-Sea Imaging and Analysis Tools for Deep-Sea Exploration: A Collaborative Design Study

“…Increasingly, emerging technologies for ocean exploration and research cost ~$10k-100k USD and are more portable, easier to operate, and offer a variety of capabilities, accuracy levels, and robustness (Sheehan et al, 2016;Dominguez-Carrió et al, 2021;Giddens et al, 2021). For the past few years, "do-ityourself " and open-sourced shallower tools (<300 m) have been developed using microcontrollers, single-board computers, and commercially available components to create camera and/or sensor systems within ~$100-$1000 USD (Simoncelli et al, 2019;Greene et al, 2020;Lertvilai, 2020;Mouy et al, 2020;Bilodeau et al, 2022;Butler and Pagniello, 2022). Two low-cost camera systems are designed for depths of 5,500-6,000 m (Phillips et al, 2019;Purser et al, 2020), and commercially available cameras such as GoPros can be after-market housed to ~3,000 m; none of these options, however, include sensors such as depth or temperature, which are critical for scientific understanding of the environment.…”

Simple tracking of occluded self-propelled organisms

“…Unfortunately, these methods are progressively becoming more complicated, considerably more expensive and time-intensive. We stress that streamlining measurement setup is indispensable, especially for potential field applications [23,24]. In this regard, portability including simplicity is another factor to be met.…”