Editor’s Note: This is the abstract of the winning student poster at TOS’s Inaugural Meeting.
We have designed and tested an innovative biophysical in situ measurement system to investigate the role of vertical motion in the photosynthetic response of phytoplankton within the upper mixing layer of the ocean. The two elements of the system are highly automated ensembles of sensors and control mechanisms integrated to obtain coincident measurements of photosynthesis and velocity/density. The scales of physical motion addressed locally range from one centimeter to one meter and ten hertz to ten days. To cover larger spatial scales such systems can be nested in arrays. Velocity is sensed electromagnetically with electrodes distributed to resolve a wave number/frequency spectral window thought to be important in defining plankton trajectories. The self-contained, in situ photosynthesis device acquires multiple rate estimates from a contained culture. Photosynthetic response is obtained on time scales from approximately five minutes to twenty-four hours by controlling the range of pH and dissolved oxygen within the culture. A principal objective of the measurement is to determine the coherence between physical forcing and phytoplankton response. Recent prototype field data are presented to demonstrate performance and compare output from this system with standard techniques of photosynthesis measurement.