Evaluation of the influence of abiotic and biotic factors on primary production in the Kara Sea in autumn

Abstract

A regression analysis of the parameters of primary production versus environmental factors was performed on the basis of data of three complex expeditions performed in the Kara Sea in September to October 1993, 2007, and 2011. The analysis of the dependence of the depth-integrated primary production (PPint) on the value of surface chlorophyll a (Chl0) and assimilation activity (ANm) showed that only 12% of the variability of the integrated PPint was determined by the variability of Chl0, whereas the correlation between PPint and ANm was strong (R2 = 0.635). Thus, in autumn, PPint values in the Kara Sea depended primarily on the activity of phytoplankton assimilation. At the end of the vegetative season, high (close to or above 1 mg/m3) Chl0 values did not reflect phytoplankton production within the entire photosynthetic layer, where organic matter was synthesized at a low rate. In turn, PPint and ANm depended primarily on the intensity of insolation and was weakly related to the content of dissolved forms of nitrogen and phosphorus. In autumn, at the end of the vegetative season, insolation apparently is the main factor in the determination of the formation of primary production in the Kara Sea.