Laboratory and ocean studies of phytoplankton response to fossil turbulence

Abstract

Abstract Two classes of phytoplankton; dinoflagellates, which can swim, and diatoms, which cannot, apparently respond to turbulence and its enhanced persistence time through stratified fossil turbulence, but in opposite ways. Threshold levels of viscous dissipation rates for growth inhibition e GI and minimum duration times T GI for dinoflagellates have been quantified by laboratory tests and compared with observed negative dinoflagellate population response to ocean surface waves. Positive diatom population response to waves has been observed and quantified by laboratory studies. Both populations have the same but weaker response to winds. A model based on the observations and Gibson's fossil turbulence theory [Gibson, C.H., 1980. Fossil temperature, salinity, and vorticity turbulence in the ocean. In: Nihoul, J. (Ed.), Elsevier, Amsterdam, pp. 221–257; Gibson, C.H., 1986. Internal waves, fossil turbulence, and composite ocean microstructure spectra. J. Fluid Mech. 168, 89–117.] suggests that phytoplankton species may have evolved by means of turbulence and fossil turbulence pattern recognition that optimize their survival based on swimming ability in evolving surface layer sea states where an impending change of surface sea state from strongly stratified to mixed is signaled by persistent patches of stratified fossil vorticity turbulence with large e that can only be produced by breaking surface waves on a strongly stratified surface layer.