Space and Time Variations of Organic Matter in Caspian Sea Water

Abstract

The analysis of data on the space and time variations of the concentrations and element composition of organic matter dissolved in Caspian Sea water over 2010–2015 showed that the average concentrations of C_org and N_org did not changed over the last 5 years of sea level drop relative to the period of level rise, while the concentrations of P_org decreased more than three times, i.e., qualitative changes had taken place in the organic matter. According to the average data, the concentrations of C_org, N_org, and P_org in the southern waters were slightly higher than those in the Northern and Middle Caspian waters. In deep-water regions, the concentrations of С_org, N_org, and Р_org increase at the boundary of hydrogen sulfide appearance. The presence of hydrogen sulfide in deep waters of the Derbentskaya and Southern Caspian depressions, accompanied by an increase in OM, suggests that no radical increase in vertical seawater mixing took place in these regions during the eight-year regression. The distribution of carbohydrates demonstrates a considerable contribution of petroleum hydrocarbon OM to the total pool.