Assessing the Importance of Calcite to Optical Backscattering in the Ocean
1997
Balch, William M.
The long-term goals for my ONR project were to quantify the light scattering properties of suspended calcite particles in the sea; and to predict suspended calcite concentrations in space and time. Calcite is one of the most abundant minerals on earth, and much of it is biogenically formed by ubiquitous phytoplankton known as coccolithophores. These picoplankton produce micron-sized scales known as coccoliths which represent a major source of optical scattering in the sea. Understanding their variability will allow more complete optical closure in the sea. The objectives of my work during the first year were to : (1) measure the volume scattering function of solutions of detached coccoliths from various cultured coccolithophore species, (2) calculate optical backscattering for the individual detached coccoliths, (3) measure the calcium content of the same samples using graphite-furnace atomic absorption in order to calcite-specific backscattering coefficient and (4) collect calcite samples from ships of opportunity for sorting of natural calcite particles. The objectives of the second year's experiments were to measure the calcite-specific backscattering coefficient for pure biogenic calcite coccoliths from (1) pure cultures of various species of coccolithophores and (2) natural seawater samples containing a variety of coccoliths not available from cultures.
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