A litre-scale chaotic stirring tank for naturalistic plankton-flow interactions

Plankton-flow interactions drive food web dynamics, biogeochemical cycling, and climate feedback mechanisms in the global ocean. Our understanding of these interactions has been constrained however by our ability to experimentally replicate complex oceanic flows in tractable volumes. Here we provide an open-source design and extensive flow characterizations for a litre-scale chaotic flow facility: the miniature oscillating grid tank (MOG). To expand the range of chaotic and turbulent flow states realizable within the small-volume constraint, we investigated a range of forcing schemes, including alternative grid geometries and forcing stochasticity. We used particle image velocimetry (PIV) to quantify important flow statistics and found MOG capable of realizing a broad range of flow regimes, with energy dissipation rates from less than 10^-7 to greater than 10^-3 W/kg and Kolmogorov lengthscales from 2 to 0.15 mm. We produced convenient power laws for these parameters as a function of grid velocity, providing turn-key forcing recipes to meet the needs of investigators studying diverse plankton-flow interactions. In light of our findings, we discuss the changing views of what constitutes planktonically-relevant hydrodynamic landscapes, as well as the complexities of replicating naturalistic flows at the litre-scale.