Spatiotemporal variability of organic matter in the waters of the Bering Sea

The changes in the concentrations of dissolved organic carbon and nitrogen (Corg and Norg) in the waters of the western part of the Bering Sea and Anadyr Bay over the last two decades are analyzed. It is shown that Corg and Norg concentrations varied within very wide ranges over all the years of observations. The maximum variability of Corg concentrations (85–481 μM) was observed in the summer months of the 1990s. The variability of these values remained quite wide (66–337 μM) in the autumn of 2012, with a decrease in limiting values and average concentration of Corg. The maximum concentrations were characteristic for the photic layer. The average Norg concentrations were 1.5–2 times less than those in autumn. These facts determined 3–4-fold increase in values for the C : N molar ratio in the dissolved organic matter in summer over autumn. Similar data were also obtained for Anadyr Bay. The revealed primary difference in the amount and elemental composition of dissolved organic matter were caused by seasonal rather than by interannual variations in the conditions of shelf and pelagic ecosystems of the surveyed region.