An In-Situ Particle Image Velocimetry System for Measuring Bubble-Induced Flows at a Seafloor Marine Seep

Natural marine seeps are important sources of hydrocarbons in the ocean. The vertical transport of hydrocarbons by rising bubbles is sensitive to source conditions, including bubble size distribution, ocean temperature, and the onset of gas hydrate formation. Bubble-induced flows near the source may also influence the rise velocity of bubbles and affect their transport and fate in the water column. However, in-situ measurements of flow conditions near marine seeps remain scarce, limiting our ability to assess the role of bubble-induced flows in vertical hydrocarbon transport. Here, we present an in-situ particle image velocimetry (PIV) system designed to measure seafloor flow fields at a marine seep site. The system integrates a consumer-grade laser module and an Ethernet-connected computer-vision camera, both controlled by a Raspberry Pi. All electronic components are enclosed in three pressure housings rated up to 1000 meters seawater. We evaluated the system's performance in measuring mean velocity fields and turbulence statistics under three conditions: a single-phase water jet, a bubble-chain-induced flow, and a bubble plume. The results indicate satisfactory performance. The system was deployed using a remotely operated vehicle (ROV) and successfully operated at a seep site in the Gulf of Mexico. The data reveal limited bubble-induced flow velocities, consistent with laboratory observations of weak bubble plumes.