E. A. Romankevich

Chlorophyll, primary production, fluxes, and balance of organic carbon in the Laptev Sea

Materials on the cycle of organic carbon in Russian Arctic seas (including the Laptev Sea) were summarized in the monograph [1]. One of the most important characteristics of organic matter (OM) fluxes is primary production, which was assayed for the Laptev Sea based on relatively scarce field observations [2–4] and the data of satellite-borne CZCS color-scanner measurements containing, despite eight years of observations (from 1978 to 1986), information on chlorophyll only in the coastal zone and only in September (because of permanent cloudiness).

Primary production and fluxes of organic carbon to the seabed in the Eurasian arctic seas, 2003–2012

The primary production and fluxes of organic matter to the seabed and their variations were estimated in the Greenland, Barents, Kara, Laptev, East Siberian, and Chukchi seas in 2003–2012 on the basis of satellite and in situ data. When counting the open water area with the assumptions made for the assessment of the primary production in the sea areas hidden under clouds, an increase in primary production was recorded in all these seas, the total production (phytoplankton and ice algae) has grown from 250 × 106 to 400 × 106 t of C per year over the last ten years. The calculation of the OM flux to the seabed showed growth for certain seas from 4 to 12% per year.

Masses of carbon in the Earth’s hydrosphere

Recent data were summarized on the concentration and mass of inorganic and organic carbon in reservoirs of the Earth’s hydrosphere. We compared carbon masses and accumulation conditions in the surface hydrosphere and waters of the sedimentary shell and proportions between carbonate, dissolved, and suspended particulate organic carbon. It was shown that the total masses of carbon in the surface hydrosphere and in the waters of the sedimentary shell are approximately equal to 80 × 1018 g C at an organic to carbonate carbon ratio of 1 : 36 and 1 : 43, respectively. Three main forms of organic compounds in the ocean (living organisms, suspended particles, and dissolved species) occur in the proportion 1 : 13 : 250 and form the pyramid of masses 4 × 1015 g, 50 × 1015 g, and 1000 × 1015 g Corg. The descending sequence of the organic to carbonate carbon ratio in water, ocean (1 : 36) > glaciers (1 : 8) > lakes (1 : 2) > rivers (1 : 0.6) > wetlands (1 : 0.3), is in general consistent with an increase in the same direction in the mean concentrations of organic matter: 0.77 mg Corg/L in the ocean, 0.7 mg Corg/L in glaciers, 6–30 mg Corg/L in lakes, 15 mg Corg/L in rivers, and 75 mg Corg/L in wetlands. Both the mean concentrations and masses of dissolved organic matter in the pore waters of oceanic sediments and in the waters of the sedimentary shell are similar: 36–37 mg/L and 5 × 1018 and 5.6 × 1018 g, respectively. The mass of carbonate carbon in the pore waters of the ocean, (19–33) × 1018 g, is comparable with its mass in the water column, 38.1 × 1018 g.

Ionic composition of pore water in shallow shelf deposits of the Laptev Sea

The cationic and anionic compositions of pore water in shallow deposits of Buor-Khaya Bay is studied. Significant concentration heterogeneity of the vertical ionic profile in the studied drill columns is shown. It is established that the vertical ionic profile of shelf deposits of the Laptev Sea is basically formed under the influence of thawing of underwater permafrost, hydrodynamic conditions, the water mass, and heat flows and depends on the lithological and granulometric types of the deposits. The highest concentrations of ions are registered in plant detritus represented by ground grass vegetation. A relationship between the ionic composition of pore water and cryogenic state of the sequence and its variability is demonstrated using the method of major components.

Particle size composition of Holocene–Pleistocene deposits of the Laptev Sea (Buor-Khaya Bay)

New data on the particle size composition of the Laptev Sea shelf deposits were obtained on the basis of results of low-angle laser light-scattering of core samples from the columns studied. It was revealed that the sand fraction dominates. The results of comparative analysis of the particle size composition of deposits show that the Laptev Sea shelf zone was characterized by highly variable spatial–temporal conditions and settings of sedimentation in the Quaternary, a polygenic character of deposits, and a pulsating influence of fluvial and slope processes on the conditions of sedimentation. A tendency of coarsening in the vertical sequence that contributes to thawing of the permafrost was revealed in the Ivashkina lagoon.

Lignin as an indicator of the sedimentation conditions on the Arctic shelf

It is shown for the first time that the proportion of lignin in shelf deposits may range from 1/3 to the total concentration of organic carbon. The distribution of wood residues and lignin in the studied sedimentary formation is very uneven, which reflects the dynamic flux environment of sedimentation and OM supply. The calculated molecular indexes showed that most of the OM in deposits underwent insignificant diagenetic alterations.

Characteristic of quaternary sedimentation on a shelf of the Laptev Sea according to the molecular composition of n-alkanes

The molecular composition and distribution of the concentration of n-alkanes are considered for sediments of boreholes drilled in the shallow part of the Laptev Sea, in the area of Buor Khaya Gulf. The diverse molecular composition of n-alkanes is dominated by long-chain odd homologs, which indicate terrigenous organic matter (OM). Heterogeneous distribution and burial of OM are shown under conditions of pulsating contribution of river and thermoabrasive material and multiple changes in them up to hiatuses in sedimentation.

Organic and carbonate carbon in permafrost and thawed deposits from Buor-Khaya Bay (Laptev Sea)

The distribution of organic and carbonate carbon in core samples from holes drilled in the shallow part of the Laptev Sea, in the region of Buor-Khaya Bay and Bykovskii Peninsula is considered. Significant heterogeneity in the distribution of carbon in the three columns studied is shown. Significant spatial heterogeneities in the distribution and burial of organic material (OM) under the conditions of a pulsing entrance of river and thermosabrasive material with repeated changes, as well as the mostly terrigenous origin of OM, are demonstrated.

Alkanes in Quaternary deposits of the Laptev Sea

The distribution and genesis of n-alkanes in sediments from the 38-m sequence obtained during core boring in the Ivashkina lagoon were studied. Sediments were formed in the Holocene as a result of thermokarst and penetration of seawater. The sequence mostly includes permafrost rocks partially molten in the upper horizons and covered by Quaternary deposits, which are mostly the products of thermoabrasion.

Polycyclic aromatic hydrocarbons in Holocene–Pleistocene sediments of the Laptev Sea

The distribution and genesis of polycyclic aromatic hydrocarbons (PAHs) were studied in a 40-m core from a lagoon of the Laptev Sea that appeared during the Holocene resulting from the flooding of seawater into a freshwater lake in the area of the Buor-Khaya Gulf. The bulk of the core is constituted of permafrost rocks, thawed partially in their upper layers and covered with recent sediments (mainly by the products of intense thermoabrasion). The ratio of petrogenic and pyrogenic PAHs was evaluated.