In the present study we report mercury data in the sediment cores obtained during a Germany-Russian and Russian-Germany cruises onboard the Vessels Sonne and Akademik M.A. Lavrentyev in Kuril area. This region cover an extensive area of the Northwest Pacific included the trench system and adjacent abyssal plain, ranging zone off the Kuril Islands. Kuril area is characterized by high water biological productivity, intensive volcanic activity, and hydrological features. Mercury concentrations in sediment cores were analyzed using a Zeeman atomic absorption spectrometer with high frequency modulation of light polarization and a pyrolysis attachment to determine its occurrence, distribution, and deposition flux. Mercury concentrations in the sediments ranged between 8‒170 ppb; its minimal concentrations (8‒15 ppb) were detected in sandy turbidites. For the pre-industrial period, Hg flux ranged between 33‒36 µg/m2 year. The maximum Hg flux (44 µg/m2 year) corresponded to the 1980, with decreases of up to 30 µg/m2 year in modern sediments (top-core sediment samples). The Hg outlet temperature in the bottom sediments corresponded to a physically sorbed form of Hg and depends on the Hg content of diatoms (siliceous residues). Hg concentrations were significantly positivly correlated with total organic carbon content but negativly correlated with Al, Fe, Zr, and Sr contents. Thus, two main factors affected Hg burial in bottom sediments; atmospheric deposition of Hg and biological productivity. The effect volcanic activity has not been clearly established in this study.
2020. V. 180. Art.no. 102235

The colorimetric method of analysis was first used to study the distribution of the color characteristics (spaces RGB and HSL) in sediment cores from the Kuril Basin of the Sea of Okhotsk and the nearby Kuril-Kamchatka Trench area of the Northwest Pacific. The statistic processing of these and in addition obtained geochemical and grain-size data made it possible to establish the controlling factors and significant relations. The most stable direct correlation is demonstrated by the characteristics of R–Mn–Mo (fine-grained oxidized sediments enriched in hydroxides of iron and manganese and related with them microelements) and H–L–SiO2 (coarse-fragmental part of sediments involving the grains of rock-forming minerals and sometimes a significant admixture of the diatom frustules). Usually, saturation S and phosphorus content gravitate to the first group of parameters, and the additive primary blue color B tends to the second group. Informative are some relations of the color characteristics, for example, the additive primary red color R and green color G (the boundary of the oxidized and reduced sediments). The admixture of the volcanogenic (pyroclastic) material can be reflected in the shift and disruption of the described relations. The results obtained show the regional conditions of sedimentation with the participation of the terrigenous, biogenic, and volcanogenic material and subsequent diagenetic redistribution of the matter. The revealed regularities together with other characteristics of the matter composition can be used for the detailed description of the sediment cores of the regions with the similar settings of sedimentation.
2019. V. 178. Art.no. 102197

Community and abundance patterns of meiofauna and Harpacticoida in the Kuril-Kamchatka Trench, that trench’s slope and adjacent abyssal plain which is located in the North-Western Pacific were investigated in relation to environmental variables. Overall, Nematoda was the dominant taxon of the meiofauna community (93%), followed by Copepoda (3%). Nineteen harpacticoid families and 1 subfamily were found, whereby the family Ameiridae was most abundant in the study area. Within eight selected (sub)families (Argestidae, Aegisthidae, Ancorabolidae, Canthocamptidae, Cletodidae, Cylindropsyllinae, Parameiropsidae, Zosimeidae) 27 genera were found, with Zosime and Mesocletodes being most abundant. Dispersion effects characterized the meiofauna community abundances, while the Harpacticoida communities in the hadal and abyssal were distinct. The main contributor to the dissimilarities observed were Nematoda, Ameiridae, Zosime and Mesocletodes. Food availability, sediment composition and water depth are environmental drivers structuring the investigated communities in the abyssal and hadal. For the trench slope, no correlations with the investigated environmental variables were found. Very likely variables other than the investigated ones act as environmental drivers for the trench slope (e.g. topography). Furthermore, a tendency of meiofauna to increase in total abundances was detected with increasing depth in the deeper stations starting at 6000 m. In contrast, total Harpacticoida abundances decrease with depth. Considering the abundance of Harpacticoida families and genera individually, the abundance of some taxa decreased in the trench slope but increased in the trench floor (Zosimeidae, Miraciidae, Argestidae, Parameiropsis, Zosime). Diversity indices based on Harpacticoida genus and family level were not distinguishable with the exception of equitability (J) at the genus level (abyssal vs hadal; trench slope vs hadal).
2019. V. 173. P. 192-207