Korchemkina E.N., Mankovskaya E.V.
The paper shows the results of optical measurements carried out during the coccolithophore bloom and the primary bio-optical characteristics obtained. Blooming coccolithophores produce a significant amount of mineral suspension, increasing light scattering and reducing the transparency of water. An increase in the backward scattering leads to an increase in the upwelling radiance and the reflectance coefficient of the sea water. Field measurements were carried out on an oceanographic platform located 600 meters from the coastline in July 2012 and May 2017. The measured parameters included light beam attenuation coefficient, sea reflectance, and the Secchi disk depth, satellite data from MODIS scanners Leves 2 and 3 were also used. The measured beam attenuation coefficient was twice higher than in the absence of the bloom, the reflectance was three times higher. Measured values show similar temporal variability. The calculations of the primary bio-optical characteristics were carried out using semi-analytical algorithms. The coccolith concentration was estimated in various ways; the results and their temporal variability are in good agreement. The calculated backscattering is an order of magnitude higher compared to the absence of the bloom, while the GIOP model somewhat underestimates the calculated values. The combined use of satellite and contact data makes it possible to restore both total scattering and backscattering. The asymmetry coefficient of the scattering and the backscattering ratio show an increase in the fraction of small particles with a high refractive index.