184
computation, it results in a misestimate of the index, by an unknown factor. This
miscalculation is at least suspected when cell-by-cell (micro spectrophotometric or flow
cytometric) methods are used. With cell orientation not necessarily random, the shape effect
could be of importance. This deserves further study, along with other optical properties such
as the polarization state of the scattered light, able to provide additional information, which
would be valuable in discriminating between the influences of size and index upon the
scattering signals.
Optics of marine particles and bulk optical properties of oceanic waters are obviously related,
even if the links cannot presently be accurately described. A comparison has been attempted
between the cumulated contributions (in absorption, scattering and backscattering) of the
various components (those presently identified) and the optical properties of Case 1 waters,
as empirically derived from field data. Preliminary conclusions show that absorption and
scattering in the upper layers of the ocean are approximately accounted for by the
contributions of algae and heterotrophic organisms (of bacteria in particular, in the scattering
process), whereas the role of detritus would remain uncertain. When dealing with the
backscattering process, the situation is inverted; yhe rather well-identified particles (algal and
microbial cells) cannot explain the backscattering coefficient observed at sea. Therefore, the
somewhat mysterious, mostly detritic, tiny particles (0.1 - 1 /tm) are likely the main
contributors to the formation of this coefficient.
ACKNOWLEDGEMENTS
The author would like to thank Y.H. Ahn for his assistance in preparing many figures, and in making available
some unpublished results. B. Gentili is duly acknowledged for his efficient help in programing and A. Bricaud
for a critical review of a first version of the manuscript.
REFERENCES
Aas E (1981) The refractive index of phytoplankton. Inst Rep Ser, Univ Oslo, 46:61 p
Aas E (1984) Influence of shape and structure on light scattering by marine particles. Inst
Resp Ser Univ Oslo 53: 112 p
Ackelson SG, Spinrad RW (1988) Size and refractive index of individual marine particulates:
a flow cytometric approach Appl Opt 27: 1270-1277
Ahn YH, (1990) Proprietes optiques des particules biologiques et minerales presentes dans
l'ocean. These, Universite Pierre et Marie Curie, pp 208
Asano S, Sato M (1980) Light scattering by randomly oriented spheroidal particles. Appl Opt
19:962-974
computation, it results in a misestimate of the index, by an unknown factor. This
miscalculation is at least suspected when cell-by-cell (micro spectrophotometric or flow
cytometric) methods are used. With cell orientation not necessarily random, the shape effect
could be of importance. This deserves further study, along with other optical properties such
as the polarization state of the scattered light, able to provide additional information, which
would be valuable in discriminating between the influences of size and index upon the
scattering signals.
Optics of marine particles and bulk optical properties of oceanic waters are obviously related,
even if the links cannot presently be accurately described. A comparison has been attempted
between the cumulated contributions (in absorption, scattering and backscattering) of the
various components (those presently identified) and the optical properties of Case 1 waters,
as empirically derived from field data. Preliminary conclusions show that absorption and
scattering in the upper layers of the ocean are approximately accounted for by the
contributions of algae and heterotrophic organisms (of bacteria in particular, in the scattering
process), whereas the role of detritus would remain uncertain. When dealing with the
backscattering process, the situation is inverted; yhe rather well-identified particles (algal and
microbial cells) cannot explain the backscattering coefficient observed at sea. Therefore, the
somewhat mysterious, mostly detritic, tiny particles (0.1 - 1 /tm) are likely the main
contributors to the formation of this coefficient.
ACKNOWLEDGEMENTS
The author would like to thank Y.H. Ahn for his assistance in preparing many figures, and in making available
some unpublished results. B. Gentili is duly acknowledged for his efficient help in programing and A. Bricaud
for a critical review of a first version of the manuscript.
REFERENCES
Aas E (1981) The refractive index of phytoplankton. Inst Rep Ser, Univ Oslo, 46:61 p
Aas E (1984) Influence of shape and structure on light scattering by marine particles. Inst
Resp Ser Univ Oslo 53: 112 p
Ackelson SG, Spinrad RW (1988) Size and refractive index of individual marine particulates:
a flow cytometric approach Appl Opt 27: 1270-1277
Ahn YH, (1990) Proprietes optiques des particules biologiques et minerales presentes dans
l'ocean. These, Universite Pierre et Marie Curie, pp 208
Asano S, Sato M (1980) Light scattering by randomly oriented spheroidal particles. Appl Opt
19:962-974