The (Anti) Gravity Machine: Behavioral Imaging at Sub-cellular Resolution of Marine Plankton Undergoing Vertical-Migration*

Marine plankton exhibit a Diel Vertical Migration with vertical displacement scales from several tens to hundreds of meters. Even at the scale of small phytoplankton and zooplankton (100 μm to  a few mm) the interaction of this vertical swimming behavior with hydrodynamics affects large scale distribution of populations in the ocean and is thus an important component of understanding ocean ecology. However, concurrently observing organismal physiology and behavior is challenging due to the vast separation of scales involved. Resolving physiological processes involves sub-cellular (micron) resolution while tracking freely swimming organisms implies vertical displacements of several meters. We present a simple solution to this problem in the form of a “hydrodynamic treadmill” incorporated into a table-top tracking microscope. We use this method to study the behavior of freely swimming marine plankton, including the larvae of P. miniata (Bat Star), O. spiculata (Brittle  Star), S. purpuratus (Sea Urchin) and D. excentricus (Sand Dollar). Our studies reveal a rich space of dynamic behavioral states including continuous swimming, hovering and feeding. We further use our method to study problems such as the growth dynamics and ecology of falling marine snow.