Dataset: Laboratory Skeletonema Grethae Disaggregation

Samples were incubated using f/2 medium and laboratory-made artificial seawater with a salinity of 30 ppt. Culturing was done with a light intensity of 30 micromol per square meter per second on a 12:12 hour light/dark cycle. All culturing was conducted at a room temperature of 20.9 deg-C.  Strains were maintained in their exponential growth phases by splitting at a regular rate prior to experimentation.

Skeletonema grethae experiments were conducted by filling oscillating roller tanks with ~1L of artificial seawater and strain with a cell concentration of ~450,000 cells/ml. Cells were aggregated into large aggregates through differential sedimentation by rolling them for 3 hrs at a rotation rate of 3 rpm prior to creating laminar shear. To create laminar shear and induce disaggregation, the flow motion inside the rotating/oscillating tank was a superposition of a solid body rotation and a harmonic oscillatory flow. We provided an analytical solution to this viscous oscillatory flow in the attached publication. Given proper boundary conditions, this roller tank created calibrated laminar shear that is similar in magnitude to that in the ocean.

With high-speed imaging techniques, we captured the fragmentation of laboratory-made diatom aggregates exposed to the calibrated oscillatory flow. We have also developed a unique image processing method that enabled continuous tracking of particle positions, sizes, and morphologies, as well as the determination of individual aggregate breakup events. The image processing consisted of background removal, particle identification, particle matching, and breakup detection. The analytical solution of fluid flow allowed us to couple the hydrodynamic conditions to the recorded time history. 

Taxonomic name, LifeSciences Identifier (LSID):
Skeletonema grethae, urn:lsid:marinespecies.org:taxname:376665

Instrument Summary: 

The experimental facility consisted of a transparent acrylic cylindrical tank supported by four identical casters. The tank had an inner diameter of 100 mm and a wall thickness of 5 mm, with a total length of 300 mm. The tank was long enough to have a two-dimensional flow along the central tank cross-section. We controlled the rotation of this tank using an electric servo-motor (Dynamixel MX-28T, Trossen Robotics), programmed with Python. A timing belt drive system that connected the motor to one end of the tank precisely synchronized the rotation with a gear ratio of one. The motor had a resolution of 0.012 rad/s in rotation speed and 0.088º in operating angle. The optical transparency of the tank permitted illumination through the cylinder wall and the imaging of suspended particles through one end of the tank. An LED light panel (StudioPRO S-1200D, Fovitec) shone through a slit aperture (10 mm wide) to illuminate suspended particles along the central tank cross-section. We mounted a high-speed camera (FASTCAM Mini AX200, Photron) with its viewing axis perpendicular to the resulting light sheet. It captured particle motion through a macro lens with a 105 mm focal length (Sigma 105mm f/2.8 EX DG).