SGER: Biomixing - a controversial mechanism influencing dynamics of marine ecosystems?

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The investigators will study the phenomenon of "biomixing" - the process by which the movement of organisms cause the mixing of the water column - by bring together two novel approaches - a developing technology, Self-Contained Underwater Velocimetry Apparatus (SCUVA), and a developing study system (marine lakes). Typical instrumentation that study particle velocity and turbulence at small scales - digital particle image velocimetry (DPIV) - are typically limited by large size, physical connections to the surface, and inability to actively track moving animals. SCUVA is a less cumbersome, autonomous, portable DPIV equipment able to quantify the flow field surrounding individual animals in real-time. Using SCUVA, it is possible to measure aquatic animal-fluid interactions from 0.002 m to 0.25 m size and thus to integrate turbulence created by individual animals or swarms of medusae with mesoscale eddy mixing of the entire water-column measured synchronously with established Acoustic Doppler Current meter Profiler technology. Marine lakes are bodies of seawater entirely surrounded by land. They are easily accessible, small-to-medium sized ecosystems that can be studied comprehensively on a modest scale and budget. Lakes with tidal exchange limited to discrete submarine tunnels also contain billions of copepods and tens of millions of fist-to-plate sized jellyfish. Thus tidal mixing, biomixing (by micro- and macro-zooplankton), and wind-mixing can each be quantified, and marine lakes may provide simpler microcosms of more widespread, complex systems. The investigators will quantify the relative impact of physical and biological mixing by swarms of medusae using the General Ocean Turbulence Model (GOTM). Broader impacts: The project will contribute to increased diversity in the oceanography by continuing training of a female Palauan research assistant in marine science, and facilitating the research of two female graduate students. The simulation using GOTM will be employed by resource managers in Palau to explore possible impacts of changing climate, mediated directly by weather or indirectly by jellyfish population dynamics, on the "Jellyfish Lake" ecosystem which is an important biodiversity and economic resource in Palau. The GOTM model will be adaptable to explore diverse coastal situations, promoting thorough exploration of the potential of biomixing in the ocean.