Influence of heterotrophic bacteria and other sub-micrometer particles on light scattering in the ocean.
Files
Date
1992
Authors
Ulloa, Osvaldo.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Mie theory is applied to estimate scattering by polydispersions of marine particles, with particular emphasis on heterotrophic bacteria and sub-micrometer detrital particles.
The error incurred in deriving bacterial optical properties by use of the simpler approximations of van de Hulst is computed. Simple approximations are derived for the scattering coefficient due to bacteria with normal and gamma size distributions. The scattering properties of natural bacterial assemblages in three marine environments, Georges Bank, Northeast Channel, and Sargasso Sea, are assessed by applying Mie theory to field data on bacterial size and abundance. Results show that heterotrophic bacteria can contribute significantly to both the total scattering coefficient and the backscattering coefficient of sea water, but that their contribution to the backscattering coefficient is relatively lower. The relative contribution of bacteria to the scattering properties of sea water was found to be unrelated to the amount of phytoplankton pigments present in the water.
The backscattering ratio (ratio between the backscattering coefficient and the total scattering coefficient) for the total particle suspension with a Jung-type size distribution was found to be largely controlled by sub-micrometer particles, and its magnitude to vary strongly with the value of the exponent in the Junge-type distribution, which in turn describes the shape of the size distribution. The backscattering ratio, however, does not vary with wavelength, nor is it significantly affected by absorption. It is predicted that even if sub-micrometer detrital particles, and not phytoplankton, are responsible for most of the backscattering in the ocean, an inverse relationship between the backscattering ratio and phytoplankton pigment concentration would exist, due to the observed inverse relationship between phytoplankton pigments and the parameter that describes the shape of the size distribution.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
The error incurred in deriving bacterial optical properties by use of the simpler approximations of van de Hulst is computed. Simple approximations are derived for the scattering coefficient due to bacteria with normal and gamma size distributions. The scattering properties of natural bacterial assemblages in three marine environments, Georges Bank, Northeast Channel, and Sargasso Sea, are assessed by applying Mie theory to field data on bacterial size and abundance. Results show that heterotrophic bacteria can contribute significantly to both the total scattering coefficient and the backscattering coefficient of sea water, but that their contribution to the backscattering coefficient is relatively lower. The relative contribution of bacteria to the scattering properties of sea water was found to be unrelated to the amount of phytoplankton pigments present in the water.
The backscattering ratio (ratio between the backscattering coefficient and the total scattering coefficient) for the total particle suspension with a Jung-type size distribution was found to be largely controlled by sub-micrometer particles, and its magnitude to vary strongly with the value of the exponent in the Junge-type distribution, which in turn describes the shape of the size distribution. The backscattering ratio, however, does not vary with wavelength, nor is it significantly affected by absorption. It is predicted that even if sub-micrometer detrital particles, and not phytoplankton, are responsible for most of the backscattering in the ocean, an inverse relationship between the backscattering ratio and phytoplankton pigment concentration would exist, due to the observed inverse relationship between phytoplankton pigments and the parameter that describes the shape of the size distribution.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
Keywords
Biology, Oceanography.