NDLI: Light scattering by coccoliths detached from Emiliania huxleyi

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Balch, William M. Boynton, G. Chris Tarran, Glen A. Gordon, Howard R. Smyth, Timothy J.
Description	Author Affiliation: Gordon HR ( Department of Physics, University of Miami, Coral Gables, Florida 33124, USA. hgordon@miami.edu);
Abstract	We used in situ radiance/irradiance profiles to retrieve profiles of the spectral backscattering coefficient for all particles in an E. huxleyi coccolithophore bloom off the coast of Plymouth, UK. At high detached coccolith concentrations the spectra of backscattering all showed a minimum near $ ∼ 550 $ to $ 600 nm $ . Using flow cytometry estimates of the detached coccolith concentration, and assuming all of the backscattering (over and above the backscattering by the water itself) was due to detached coccoliths, we determined the upper limit of the backscattering cross section ( $ σ _{ b } $ ) of individual coccoliths to be $ 0.123 ± 0.039 μm ^{ 2 } / coccolith $ at $ 500 nm $ . Physical models of detached coccoliths were then developed and the discrete dipole approximation was used to compute their average backscattering cross section in random orientation. The result was $ 0.092 μm ^{ 2 } $ at $ 500 nm $ , with the computed $ σ _{ b } $ displaying a spectral shape similar to the measurements, but with less apparent increase in backscattering toward the red. When $ σ _{ b } $ is computed on a per mole of calcite, rather than a per coccolith basis, it agreed reasonably well with that determined for acid-labile backscattering at $ 632 nm $ averaged over several species of cultured calcifying algae. Intact coccolithophore cells were taken into account by arguing that coccoliths attached to coccolithophore cells (forming a “coccosphere”) backscatter in a manner similar to free coccoliths in random orientation. Estimating the number of coccoliths per coccosphere and using the observed number of coccolithophore cells resulted is an apparent backscattering cross section at $ 500 nm $ of $ 0.114 ± 0.013 μm ^{ 2 } / coccolith $ , in satisfactory agreement with the measured backscattering.
ISSN	1559128X
Volume Number	48
Journal	Applied Optics
Issue Number	31
e-ISSN	21553165
Language	English
Publisher	Optical Society of America
Publisher Date	2009-11-01
Publisher Place	United States
Access Restriction	Subscribed
Subject Keyword	Calcium Carbonate Analysis Chemistry Environmental Monitoring Methods Geologic Sediments Nephelometry And Turbidimetry Phaeophyta Isolation & Purification Metabolism Algorithms Computer Simulation Fossils Light Models, Biological Oceans And Seas Scattering, Radiation Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Optics
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Electrical and Electronic Engineering

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