Open AccessSub-micron picoplankton shape, orientation, and internal structure combined to preferentially amplify the forward scatter
Author(s) -
Tim Smyth,
Glen A. Tarran,
Shubha Sathyendranath
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.413576
Subject(s) - optics , forward scatter , picoplankton , orientation (vector space) , prolate spheroid , prochlorococcus , physics , optical tweezers , population , materials science , scattering , biology , geometry , mathematics , ecology , cyanobacteria , genetics , phytoplankton , demography , classical mechanics , synechococcus , sociology , nutrient , bacteria
Compelling evidence is presented that sub-micron picoplankton shape, internal structure and orientation in combination leads to a disproportionate enhancement of differential forward scatter compared with differential side scatter when analyzed with a flow cytometer. Theoretical evidence is provided which results in an order of magnitude amplification in the forward scatter direction, with little or no change in the side scatter: this discounts the possibility of "doublets" caused by multiple particles simultaneously present in the laser beam. Observational evidence from progressively finer filtered seawater samples shows up to three orders of magnitude enhancement in the forward scatter direction and sizes of Prochlorococcus close to that reported in the literature (0.61 ± 0.17 µm). It therefore seems likely that flow cytometrically observed "bi-modal size distributions" of Prochlorococcus are instead the manifestation of intra-population differences in shape (spherical - prolate with preferential alignment) and internal structure (homogenous - heterogenous).