Marine phytoplankton experience competition, predation, infection and aggregation occurring across distances of micrometres to centimetres. However, the consequences of these interactions influence ...global processes, such as climate and fisheries productivity. There is a long-standing default assumption that these global processes cannot be traced to plankton distributions and interactions below a few metres because of the homogenising effect of turbulence Hutchinson, G.E., 1961. The paradox of the plankton. Am. Nat. 95, 137–146.; Siegel, D.A., 1998. Resource competition in a discrete environment: Why are plankton distributions paradoxical? Limnol. Oceanogr. 43, 1133–1146.. We show that, in active turbulence, phytoplankton patches, on the order of 10 cm, have repeatable asymmetry and regular spacing over distances of centimetres to tens of metres. The regularity and hierarchical nature of the patches in mixed ocean water means that phytoplankton are distributed in a dynamic, but definite seascape topography, where groups of patches coalesce between intermittent turbulent eddies. These patches may link large scale processes and microscale interactions, acting as fundamental components of marine ecosystems that influence grazing efficiency, taxonomic diversity, and the initiation of aggregation and subsequent carbon flux.
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.
