Phytoplankton microstructure in fully developed oceanic turbulence

Abstract

Turbulence alters phytoplankton distributions. In doing so, it changes light and nutrient availability that ultimately influences community composition and carbon flux. The quantitative basis for this paradigm is the matching of the −5/3 slopes of fluorescence and velocity spectra over scales ranging from 1 to 100 m. In this contribution, for the first time, we simultaneously show the −5/3 spectral slopes for velocity and fluorescence at sub‐metre scales. The fluorescence spectral slopes deviate from the −5/3 slope with less steep slopes, suggesting the existence of a viscous‐convective subrange for fluorescence. However, it is difficult to identify the −1 slope as predicted by the Batchelor spectral theory. This portion of spectrum could be white as proposed by Franks (2005). High order structure functions indicate that the fluorescence is more intermittent than the velocity, but less intermittent than the conductivity signals.