Spatial heterogeneity of ecological variables is recognized as an important stabilizing factor for ecosystem function, but has proved to be a difficult concept to characterize in quantitative, operational terms. In the sea, however, chlorophyll concentration can be estimated by a continuous in vivo measurement, and used to describe the spatial structure of phytoplankton populations in terms of a variance spectrum in either wavenumber or frequency space....
Denman, Kenneth L., and Trevor Platt. 1976. "The variance spectrum of phytoplankton in a turbulent ocean." Journal of Marine Research 34, (4). https://elischolar.library.yale.edu/journal_of_marine_research/1378