Waters, R. L. Flinders University of SA, Raechel Waters
Seymour, J. L. Flinders University of SA, seym0007@flinders.edu.au
Pearson, L. Flinders University of SA, lyn.pearson@flinders.edu.au
Nelson, C. Marine Sciences, UCSC,
Bass, L. Marine Sciences, UCSC,
Mitchell, J. G. Flinders University of SA, jim.mitchell@flinders.edu.au

The existence of microscale plankton patchiness has been theoretically modeled for a number of years. Newly available sampling techniques, developed to sample at the scale of these aggregations, have provided direct evidence of biological structure in the microenvironment. Here we use a suite of pneumatically operated microsamplers, at a spatial scale of 4.5 mm, to reveal coherent bacteria and phytoplankton distributions in seawater. Bacterial gradients that changed by up to a factor of 17 over 2 cm were observed, although changes of 2 - 4 times in bacterial and phytoplankton abundances over the same spatial range were more common. In some sample sets, bacteria and phytoplankton numbers fluctuated synchronously, while in others distributions were independent. Field observations could not be explained by the presence of particles or chemical gradients emanating from them. Laboratory experiments showed that heterogeneity is positively correlated with the magnitude of turbulent mixing. We propose that the observed microstructure is created and maintained by the response of microorganisms to laminar shear.
Day: Tuesday, Feb. 2
Time: 12:15 - 12:30pm
Location: Hilton of Santa Fe
Code: SS02TU1215H