Observations on the intra- and interspecific single cell optical variability of marine phytoplankton

Phytoplankton occur as a wide variety of sizes, shapes, textures, and conformational inclusions. Optical reseachers, however, to date represent phytoplankton in models as uniform or varying by only a small amount. We give evidence here of changes in the distribution of light scatter for single cells of individual species. This observation is noted even within one species. Optical characteristics show ranges of intraspecific variability (as functions of physiological or nutritional state) comparable in magnitude to interspecific variability. Such variability may be attributed to changes in the cellular refractive-index distribution and the cell size and shape.