Physical Oceanography (Aug 2022)
Integrated Primary Production in the Deep-Sea Regions of the Black Sea in 1998–2015
Abstract
Purpose. The work is aimed at estimating monthly changes in the integrated primary production in the deep-sea zone of the Black Sea in 1998–2015 using mathematical modeling based on the satellite measurements. Methods and Results. Based on the SeaWiFS and MODIS satellite observations, the integral primary production was calculated using the model modified by the authors. The algorithm developed in the Marine Hydrophysical Institute, RAS based on the in situ measurements performed in 1997–2015, was used for reconstructing the chlorophyll a concentration by the satellite measurements in the spectrum visible range. The applied sea brightness coefficients for three wavelengths 490, 510 and 555 nm permitted to take into account the colored solute absorption; they are weakly sensitive to the errors of atmospheric correction and to the light backscattering by suspension. The integral primary production was calculated using the Behrenfeld and Falkowski adapted model that had included the phytoplankton physiological parameters derived from the in situ data for the Black Sea. The data on seasonal variability of the fortnight-averaged primary production values for the central part of the Black Sea in 1998–2015 are presented. Conclusions. Over 18 years, in the deep-sea zone (below 500 m), productivity in the water column averaged 157–158 gС · m-2·year-1. In course of an annual cycle, three periods of increase in the integral primary production, namely the winter-spring, summer and late autumn ones were observed. No productivity trends were noted over the time period under study. The decline of indicators was recorded after 2008. In the eastern and western deep-sea regions, the characters of the primary production changes were similar. The productivity values obtained for 1998–2015 are consistent with those of the previous studies. In the Black Sea, observed are the alternating periods of increase and decrease in the production indicators that is conditioned mainly by climatic effects.
