Advancing in situ observations of physical and biological processes with underwater imaging systems

The ocean is a complex and dynamic environment with physical and biological processes that span across all scales. Though scientific studies in laboratory setting can provide insights into these complicated processes, it is difficult to fully replicate the natural environment in the lab. As a result, studies of processes in the natural environment, or in situ studies, can help bridge information from laboratory experiments to their actual implication in the nature. Recent technological advances have enabled the ocean to become more accessible for scientific research and exploration. Particularly, breakthroughs in imaging technology have enabled new imaging techniques to be accessible at smaller form factors and lower costs, such that they are suitable for oceanic deployments. Here I developed four underwater imaging systems and demonstrated their capability as tools for studying both physical and biological processes in the ocean. The first system is a particle imaging system that can be used to resolve average flow velocity by applying a modified particle image velocimetry algorithm. The formulated algorithm allows the system to be constructed with low-cost components that permits the whole system to be more affordable. The second system is an underwater microscope for zooplankton study that is based on open-sourced hardware and software. The system was used to investigate the emergence pattern and the spectral response of demersal zooplankton in the Kaneohe Bay, Hawaii. The third system is a stereoscopic imaging system that implements a tilted lens approach to increase the shared field of view between the two cameras. The method allows the stereoscopic system to perform in situ trait measurements of aquatic invertebrates. The system was deployed in Kendall-Frost saltmarsh, San Diego, to determine the relationship between the swimming speed and the body length of aquatic insects, Trichocorixa californica. Finally, the fourth system is an underwater microscope that has sufficient resolution and contrast perform label-free imaging of marine microorganisms. The instrument utilizes a laser-pulsed darkfield microscopy technique to image individual cells of marine microorganisms and to detect fluorescence signals from natural pigments. The system was used in an in situ observational study on biofilm formation on a man-made substrate