Organic carbon in the Razdol’naya River Estuary (Amur Bay, Sea of Japan) during the period of ice cover

Abstract

The paper presents data on organic carbon concentrations in riverine suspended matter and surficial bottom sediments measured in the estuary of the Razdol’naya River during the period of ice cover (February 2010). In the suspended matter, humic substances and phytoplankton accounted for 30% and 14% of total organic carbon, respectively. The concentration of humic substances in riverine suspended matter was determined for the first time by spectrophotometry. The concentration of phytoplankton carbon was calculated from the chlorophyll-a content. Concentrations of organic carbon, humic substances, and chlorophyll-a were measured in the surface sediment layer. The proportions of these three components show no marked variability with an increase in salinity to 23‰. The degree of humification in bottom sediments was about 52%. Organic carbon concentrations were almost an order of magnitude lower and the proportion of bioavailable (nonhumified) carbon was two times lower in the bottom sediments than in the riverine suspended matter.