A scanning particle image velocimetry system for spatial mapping of steady flow and <scp> O ₂ </scp> concentration fields around aquatic organisms

Abstract The impact of flow on aquatic organisms (and vice versa) is crucial for many aspects of their physiology and ecology, as this interaction shapes the hydrodynamic boundary layer and thereby the exchange of solutes between the organism and its surrounding environment. However, investigations of flow and boundary layers often involve complicated setups with sometimes inaccessible instrumentation. Here we present a simple, modular experimental platform that enables spatial mapping of steady, laminar flow and O 2 concentration fields over biological tissue surfaces in a 3D printed, laminar flow chamber. The system employs scanning particle image velocimetry using luminescent optical sensor particles for combined imaging of flow and O 2 concentration (SensPIV) via excitation with a pulsed light sheet, while recording the movement of particles with a colour camera at high frame rates. Spatial mapping of the steady flow is facilitated by translating the flow chamber for sequential 2D imaging, thus sweeping the light sheet in defined steps over the sample. We provide a detailed description of the experimental platform, hardware and software and demonstrate the utility of the system for 3D two‐component (3D2C) mapping of hydrodynamic boundary layers over macroalgal tissue, as well as for combined imaging of flow and O 2 over the tissue of a reef‐building coral in concert with optical coherence tomography. The platform enables flexible analyses of small‐scale heterogeneities in the flow and O 2 concentration fields surrounding biological structures such as plant and animal tissues and biofilms. The design and software are open‐source and can be modified to accommodate other biological samples and chemical imaging techniques.