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Visualizing subsurface burrowing by the polychaete Alitta virens with particle image velocimetry

Infauna, animals that live in marine sediments, alter physical, chemical, and biological properties of their habitats through burrowing and other activities. Though important, infaunal behavior is notoriously difficult to study. Sediments are resistant to imaging techniques because they scatter radiation and are dense and opaque, and measurements made across aquarium walls are subject to artifacts. In this study, particle image velocimetry (PIV) was used to indirectly observe the activity of the marine polychaete Alitta virens as it burrowed in sand and to measure its horizontal burrowing speed. The mean burrowing speed of 1.6 mm s‐1 for A. virens is the first published measurement of subsurface burrowing speed in sand. The extent of surficial sediment displacement was also measured. This study demonstrates the utility of PIV as a method for observing burrowing behavior and suggests potential applications in laboratory and field studies of burrowing behavior.