Effect of ice cover on the dynamics and energetics of surface and internal tides in the white sea: Model estimates

The effect of ice cover on the dynamics and energetics of surface and internal tides in the White Sea is investigated using the three-dimensional finite-element hudrothermodynamic model QUODDY-4. The sea ice is represented as a continuous and motionless ice cover that can move vertically but not horizontally. It is assumed that the resulting changes in the tidal regime are the maximum possible in reference to those occurring in real conditions when, in the cold season, a continuous and motionless ice cover is ubiquitous only in Kandalaksha, Dvina, and Onega bays, while drift ices prevail in all other areas of the White Sea. It is shown that the effect of sea ice does not lead to a qualitative restructuring of the tidal regime. However, its quantitative changes prove to be significant, which indicates that the ice-induced seasonal variation in tidal characteristics in the White Sea is important.     

Population size structure, spatial distribution, and life cycle of the hydromedusa Aglantha digitale (O.F. Müller, 1766) in the White Sea

Seasonal variations of the abundance, size structure, and vertical distribution of the population of the hydromedusa Aglantha digitale are studied using the materials collected during multiyear observations in the White Sea from 1961 to 2003. The wide distribution of the species in the Basin of the White Sea and in Kandalaksha, Dvina, and Onega bays is shown. Usually, the maximum bell height of the specimens did not exceed 12 mm, although a few individuals up to 22 mm high were found. The maximum abundance of A. digitale is observed during the reproductive period, which lasts from the second half of June to August. The reproduction starts when the water temperature near the surface reaches 9–11°C. By the onset of winter, specimens with a height of 4–5 mm representing a new generation dominate. By the beginning of the subsequent spring, their average size reaches 5–6 mm, and, by the end of June, specimens with bell heights of 8 mm become mature. During the spring and the summer, the A. digitale population concentrates in the upper 0-to 25-m water layer; during the autumn and winter, it concentrates below the 50-m depth. At the end of the autumn and in the winter, the population is spread over the water column and inhabits all the water layers. At the end of the winter, in April, the ascent of the population starts. An analysis of the seasonal dynamics of the population abundance and size structure indicates that A. digitale in the White Sea has a one-year life cycle.     

Dinoflagellate cysts in the surface sediments of the White Sea

Dinoflagellate cysts were studied in 42 samples from the surface sediments of the White Sea. The total concentration of dinocysts varies from single cysts to 25 000 cyst/g of dry sediments, which reflects the biological productivity in the White Sea waters and the regional particular features of the sedimentation processes. The highest concentrations are observed in silts; they are related to the regions of propagation of the highly productive Barents Sea waters in the White Sea. Generally, the spatial distribution of dinocysts species in the surface sediments corresponds to the distribution of the major types of water masses in the White Sea. The cysts of the relatively warm-water species (Operculodinium centrocarpum, Spiniferites sp.) of North Atlantic origin that dominate in the sediments indicate an intensive intrusion of the Barents Sea water masses to the White Sea along with hydrological dwelling conditions in the White Sea favorable for the development of these species during their vegetation period. The cold-water dinocyst assemblage (Islandinium minutum, Polykrikos sp.) is rather strictly confined to the inner parts of shallow-water bays, firstly, those adjacent to the Onega and Severnaya Dvina river mouths.     

Clay-mineral and grain-size distributions in surface sediments of the White Sea (Arctic Ocean): indicators of sediment sources and transport processes

In this study, the grain-size and clay-mineral compositions of 73 surface sediment samples collected in a variety of environmental settings in the White Sea are presented to characterize recent sedimentation processes, reconstruct transport pathways, and identify potential source areas of the terrigenous components. Areas >100 m deep are invariably characterized by silty clay, whereas areas <100 m deep exhibit more heterogeneous grain-size compositions plausibly explained by coastal erosion and (re-)distribution mechanisms, particularly tidal currents. The dominance of sand in the estuarine areas of the Onega and Dvina rivers as well as toward the Gorlo Strait connecting the White Sea with the Barents Sea is attributed to increased current speeds. Illite and smectite are the dominant clay minerals in recent sediments of the southwestern and eastern White Sea sectors, respectively. Their distribution patterns largely depend on the geology of the source areas, and mirror surface circulation patterns, especially in Dvina Bay. Smectite is a key clay mineral in White Sea surface sediments, as it reveals the dominating influence of the Northern Dvina’s runoff on sedimentation and water circulation throughout the basin. In comparison to other Eurasian shelf seas, the White Sea is characterized by a greater diversity of clay-mineral assemblages, which range from illite- to smectite-dominated sectors containing variable amounts of chlorite and kaolinite.     

Hydrocarbons in the snow-ice cover of different areas of the White Sea

The data on the content of hydrocarbons (HC) are presented and compared to the contents of organic carbon, lipids, and particulate matter in the snow-ice cover of the coastal areas of Dvina and Kandalaksha bays of the White Sea (2008–2012). The accumulation of HC in the snow-ice cover depends on the degree of atmosphere contamination, the conditions of the ice formation, and the intensity of the biogeochemical processes at the ice-water interface. Because of this, the aquatic area of Arkhangelsk is characterized by the highest HC concentrations in the snow and in the upper layer of ice. The peculiarities of the formation of the snow-ice cover in Rugozero bight of Kandalaksha Bay cause the concentrating of HC in different layers of ice. The decrease of the concentration of HC in the show-ice cover of the White Sea compared to earlier studies resulted from the recession of industrial activities during the recent years.     

Spatial distribution of phytoplankton in the White Sea in the late summer period with regard to the water structure and dynamics

The species composition and biomass of the phytoplankton, as well as the hydrophysical and hydrochemical characteristics of the water masses, were estimated for different areas of the White Sea at 24 stations for the period of August 26 to September 3, 2007. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The total biomass of phytoplankton (B _t ) varied from 87 to 1914 mg C/m². For most of the studied sites, B _t was low; dinoflagellates were the most abundant species. Diatoms dominated in the areas of elevated hydrodynamic activity, i.e., in the Gorlo (vertical mixing of the water layers), in intrusions of the Gorlo water masses into the basin of the White Sea, and in the peripheral areas of the Dvina outflow current. The B _t was also the highest in the listed areas.     

Diatoms and aquatic palynomorphs in surface sediments of the White Sea bays as indicators of sedimentation in marginal filters of rivers

Diatom algae, aquatic palynomorphs, and the grain-size of surface sediments from bays of the White Sea were investigated in a program dedicated to the study of marginal filters (MF) in the Severnaya Dvina, Onega, and Kem rivers. Three microalgal assemblages are established in surface sediments, which replace each other successively with distance from river mouths and are characterized by a gradual decrease in a share of freshwater species of diatoms and Chlorophyceae algae, significantly varying concentrations of marine diatoms and dinocysts due to changes in water salinity, grain-size composition of sediments, quantitative distribution of suspended particulate matter (SPM), and water productivity at different marginal filter stages.     

Dissipation of baroclinic tidal energy and diapycnal mixing in the White Sea

The modeling results obtained using the original version of the three-dimensional finite-element hydrostatic model QUODDY-4 testify that the spatial distributions of dissipation of baroclinic tidal energy and the related coefficient of diapycnal mixing in the deepwater stratified subdomain of the White Sea (the Basin and Kandalaksha and Dvina bays together) are highly similar to those found for low- and midlatitude oceans. It is in the open part of the sea that their values remain equal to the minimum possible values determined by the molecular kinematic viscosity; at its lateral boundaries (not all boundaries, but only individual segments (sites of mixing)), their values increase. In the shallow homogeneous subdomain of the White Sea, the dissipation of baroclinic tidal energy is considerably larger than in the deep stratified subdomain. Accordingly, the vertical eddy viscosity in the first subdomain is a few orders of magnitude higher than the coefficient of diapycnal mixing in the second subdomain. This is caused by an increased tidal velocity due to reduced depths.     

Vertical flux of phytoplankton and particulate matter in the White Sea according to the long-term exposure of sediment traps

The vertical fluxes of phytoplankton (VF_Phyto) and particulate organic carbon (VF_POC) in the White Sea were determined using seven long-term (292 to 296 days) sediment traps moored at five stations at 67–255 m depths. The annual VF_Phyto and VF_POC ranged from 0.55 to 24.64 g C/m² and from 3.7 to 93.9 g C/m², respectively. The highest VFPhyto was observed in the Basin region located close to the Gorlo along the Tersk coast. The algal biomass accounted for 15–43% of the VF_POC. Diatoms comprised the most important group, accounting for 83–100% in the sedimented biomass. Thalassiosira nordenskioeldii dominated in the VF_Phyto at all the stations except for the station in the basin close to Onega Bay, where Ditylum brightwellii was the most abundant.     

Spatial distribution of microelements in the seston of the White Sea

With a view to a more complete understanding of the role of phyto-and zooplankton in biogeochemical cycles, the spatial distributions of Fe, Mn, Co, Ni, Cr, Cu, Cd, Pb, Zn, As, Hg, and C_org in the White Sea seston (21 samples) collected in August 2004 during cruise 64 or R/V Professor Shtokman were studied. It was shown that the elements studied are accumulated in plankton with enrichment coefficients from 10² for Hg to 10⁵ for Fe, as compared to seawater. The spatial distribution of microelements is determined by the sources of their supply and correlates with the distribution of the primary production and biomass of zooplankton. The increased values of microelement contents (excluding As) are characteristic of Dvina Bay, whereas the highest As concentrations were found in Kandalaksha Bay.     

Spatial distribution of the phytoplankton in the White Sea during atypical domination of dinoflagellates (July 2009)

The species composition and biomass of phytoplankton, concentrations of chlorophyll a (Chl a) and nutrients, and accompanying hydrophysical conditions have been studied in the White Sea on July 6–11, 2009. The temperature of the surface water layer was lower than the multiyear average in July. Dinoflagellates dominated in the entire studied area; this was not the typical event for July. We suggest that domination of dinoflagellates was caused by low water temperature, when the nutrient regeneration rate was insufficient to support diatom growth. The abundance of microalgae and the structure of the phytoplankton community depended on the water structure. Variations in the phytoplankton community structure were caused not by substitution of specific species but rather by variability of the abundance of a single species, Heterocapsa triquetra. The highest phytoplankton biomass has been recorded in weakly stratified waters, where tidal mixing supplied the income of inorganic nutrients. The income of nutrients to the photic layer was limited in the stratified waters of Dvina Bay during the summer low-water period, so the phytoplankton abundance was low. We suggest that the lens of surface desalinated water presumably originated from the outlet of the Dvina River was registered in the central part of the White Sea.     

Spatial variability of the species composition,abundance, and productivity of the phytoplankton in the white sea in the late summer period

The species composition, cell concentration (N), and biomass (B) of the phytoplankton, as well as the chlorophyll a (Chl a) concentration, primary production (PP), and the concentrations of the dissolved inorganic micronutrients (phosphorus, silica, nitrogen as nitrite), were estimated for Kandalaksha Bay (KB), Dvina Bay (DB), and the basin (Bas) of the White Sea in August of 2004. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The Chl a concentration varies from 0.9 to 2.0 mg/m³ for most of the studied areas, reaching up to 7.5 mg/m³ in the Northern Dvina River estuary. The surface water layer of the DB was the most productive area, where the PP reached up to 270–375 mg C/(m³ day). The phytoplankton biomass varied from 11 to 205 mg C/m³ with the highest values observed in the Bas and DB. Three groups of stations were defined during the analysis of the phytoplankton’s species composition similarity. The dinoflagellates Dinophysis norvegica and Ceratium fusus were particular to the phytoplankton assemblages in the KB; the diatom Ditylum brightwellii was particular to the upper and central parts of the DB. These three phytoplankton species were less abundant in the Bas.     

Electromagnetic method for monitoring currents in the Gorlo of the White Sea

A technique for studying near-shore currents is assessed that is alternative to the traditional methods. The technique is based on the measurements of anomalous electromagnetic fields induced on land in the near-shore zone. The method of coastal electromagnetic monitoring was tested in the central part of the Zimnii Coast of the Gorlo of the White Sea. The results of numerical modeling of electric fields induced by tidal currents allowed us to obtain theoretical estimates of the expected signal and to choose the site of the measurements and the optimal parameters of the receiving lines applied. The experimental studies were performed on the Zimnii Coast of the Gorlo of the White Sea using two horizontal receiving lines, one of which was located on the coast and the other ran in the sea. These studies provided experimental estimates of the electric field of the tides in the Gorlo of the White Sea, which agreed with the theoretical evaluations. The results of the studies proved the efficiency of the method of coastal electromagnetic monitoring, which may be used in order to study tidal, offset-onset (surge), and quasi-stationary currents. An important advantage of the electromagnetic methods lies in the possibility to perform the studies throughout the year, including the winter period.     

Harpacticoida taxocen diversity in the silty-sandy littoral zone of Kandalaksha Bay of the White Sea

The fauna composition, ecological groups, and life forms of Harpacticoids of soft littoral grounds from 15 sites off the Karelian coast in Kandalaksha Bay of the White Sea were studied. Six types of harpacticoid taxocens with different sets of dominating species are described. On silty sands with clear signs of desalination, the Stenchelia palustris taxocen is common; medium-grained sands are characterized by the Heterolaophonte minuta, Paraleptastacus kliei — Huntemannia jadensis, and Amphiascoides nanus — Scottopsyllus minor taxocens; while on coarse sands, the Ameira parvula and Ameira scotti — Mesochra lilljeborgi taxocens have developed. The diversity of the taxocens is partly explained by the differences in the grain-size composition and salinity at different sites. In addition, groups of various taxocens dwelling on the same type of the sediments were found in different minor bights of the coastline.     

Peculiarities of the rare-earth element distribution in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River

The study of the rare-earth element (REE) systematics in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River showed that they were derived by the simple mixing of the detrital material from two geochemically contrasting provenances: the Kola-Karelian geoblock almost completely consisting of Archean rocks and the northwestern Mezen syneclise made up of the Upper Vendian, Paleozoic, and Mesozoic rocks. This is best manifested by the changes in ?_Nd(0). In terms of the Gd_N/Yb_N and Eu/Eu*, most of the studied samples are comparable with the Post-Archean craton complexes, some of which resemble the average composition of the Archean mudstone. Based on the ΣREE and La_N/Yb_N, the modern bottom sediments are subdivided into two groups: (1) those close to basalts and granites and (2) those approximating common sedimentary rocks. From the lower reaches of the Pinega River to the Tersky coast, the maximal average (La/Yb)_RPSC, (Gd/Yb)_RPSC, La_N/Yb_N, and Gd_N/Yb_N ratios were determined in the samples taken at the boundary of Dvina Bay with the Basin, i.e., in the sediments with the highest content of the pelitic component. In general, the geochemical composition of the modern bottom sediments of almost the entire White Sea area was defined by input of the eroded products of the mature continental crust with the Severnaya Dvina River, the main river of the region. Such a setting, when the formation of the sediments in a peri- or intracontinental marine basin is controlled by one large river system, presumably may be propagated to the sedimentation in the Laptev Sea, the eastern Kara Sea, the Bay of Bengal, and other basins.     

Analysis of the geomagnetic field of the White Sea: The Gorlo Strait

The objective of our research is the interpretation of the results of the geomagnetic survey of the geologic structure in the Gorlo Strait of the White Sea. We used the maps of the anomalous magnetic field (AMF) available and processed them with original interpretation software. As a result of this processing, we compiled a structural-tectonic chart of this region. We distinguished the boundaries of the major first-order tectonic structures such as the underwater extension of the Leshukon graben and a number of minor structures related to the Proterozoic and Paleozoic stages of the magmatic activity in the region. Modeling was performed for the most important objects, which allowed us to refine the geological structure of these objects and their genesis.     

Functional Activity of Phytoplankton and Optical Properties of Suspended Particulate Matter in Onega Bay of the White Sea

Oceanology - The phytoplankton activity was analyzed in June 2015 in Onega Bay of the White Sea. The chlorophyll a concentration, as well as cell abundance and cell biomass, were assessed in...     

Multidisciplinary studies in Onega Bay of the White Sea and the estuary of the Onega River during the summer period

The distribution of the temperature and salinity, current velocities, suspended particulate matter, bottom sediments, bottom morphology, and planktonic and benthic organisms during the summer period are studied in the estuary of the large Onega River and the coastal areas of Onega Bay (White Sea) influenced by interacting marine and riverine factors.     

Shelf Sediment Transformation Index

Oceanology - The paper examines the results of long-term monitoring studies of the physicochemical properties of Holocene silts in Kandalaksha Bay of the White Sea. Based on a comprehensive...     

White whale (<Emphasis Type="Italic">Delphinapterus leucas</Emphasis>) distribution in Onega Bay of the White Sea in the summer

Data on the white whale distribution in Onega Bay of the White Sea obtained during route and stationary observations in the summer of 2003–2006 are given. The presence of three regions of summer habitation of local “nonmigratory” white whale reproductive schools is confirmed. The minimum abundance of the “zhizhginskoe” (northeastern) school is 60 individuals, and the minimum abundance of the “myagostrovskoe” (western) is 50 individuals. The abundance of the best studied “southern” school is close to 120–130 individuals. One more region of white whale concentration (with an abundance of up to 40 individuals) (the eastern one; Cape Letniy Orlov-Cape Chesmenskiy) was found. The localization of single reproductive schools (RS) is due to a number of factors: the morphometry of the shores and bottom, the hydrological regime, and the character of the coastal tidal currents. The white whale distribution in the southern part of Onega Bay in the summer (June–July) is of discontinuous character with concentrations near cape Glubokiy and some other adjacent parts. The coefficient of the white whale attendance in the Cape Glubokiy area varied from 42.5 to 67.4% during the years of the studies (2003–2006). The character of the distribution, the direction of the relocations, and the animals’ behavior peculiarities indicate that the white whales of the southern part of Onega Bay of the White Sea form a rather stable school community of a few (5–6) locally distributed small family groups during the summer.