Interannual variability of the zooplankton on the shelf of the northeastern Black Sea in the autumn period

The variability of the mesozooplankton stock in the shelf pelagic communities was studied in the late summer and autumn of 2006–2008. The plankton community’s structure and distribution were described for the shoreward transect (Gelendzhik city vicinity). The indirect and direct effect of the ctenophores Mnemiopsis leidyi and Beroe ovata on the mesozooplankton community was studied. The long-term changes in the meso- and macroplankton communities of the Black Sea were analyzed for the period of 2001–2008. The effects of the climatic factors, the water mass circulation, and the factors’ interplay on the mesozooplankton dynamics were assessed. Despite the wide range of the environmental conditions, the stock biomass of Mnemiopsis leidyi appeared to be quite stable within the studied period.     

Stable C and N isotopic composition of sinking particles and zooplankton over the southeastern Bering Sea shelf

Stable carbon and nitrogen isotopic composition of zooplankton, suspended particulate organic matter (SPOM), and sinking particles collected using sediment traps were measured for samples obtained from the southeastern Bering Sea middle and outer shelf during 1997–1999. The quantity of material collected by the middle shelf sediment trap was greater in both spring and late summer and fall than in early and mid-summer. The δ¹⁵N of SPOM, sinking material and zooplankton showed greater inter-annual variability at the middle shelf site (M2) than at the outer shelf site (M3). Zooplankton and sinking organic matter collected by M2 sediment traps became more depleted in ¹⁵N from 1997 through 1999, associated with a change from unusually warm to unusually cold conditions. Suspended and sinking organic matter and zooplankton collected from M3 decreased only slightly in δ¹⁵N from 1998 to 1999. SPOM, zooplankton, and sediment trap samples collected at M2 were usually enriched in δ¹⁵N and δ¹³C over those from M3. However, in 1999 sediment trap samples from the middle shelf were enriched in ¹³C over M3 material, but the δ¹⁵N of samples from the two sites was similar. The geographic pattern could be explained greater productivity over the middle shelf, associated with either isotopically heavy nitrogen being regenerated from sediments, or with utilization of a greater fraction of the available inorganic nitrogen pool during most years.     

Sedimentary environments of the east-central Bering Sea continental shelf

A factor analysis of 180 bottom sediment samples from the east-central Bering Sea continental shelf identifies five factors that account for 95% of the variation in the 17 whole ø size classes that were used as variables. Factor I represents coarse sediments that have been bypassed in areas of active water circulation. Factors II and III represent fine and very fine sands that have been hydraulically sorted, reworked, and mixed. Factor IV represents coarse to medium silt that has been segregated from areas of relatively high energy. Factor V represents both the production of sediments finer than medium silt and deposition within the lowest-energy environment in this area.Modern and palimpsest sediments are areally prevalent over this section of the shelf. Relict sediments occur in only a few small areas. The dispersal of sediments is affected by surface and tidal currents as well as wave action. Ice rafting is not an important geological agent. Data from the eastcentral Bering Sea shelf indicate that sediments on subarctic continental shelves are not necessarily characterized by an abundance of rocky sediments or gravel.     

Phytoplankton communities in the Bering Sea and adjacent seas

Vertical distribution of phytoplankton in early warming season in the eastern Bering Sea and adjacent sea areas was investigated. In the surface layer which was under the influence of newly melted sea ice in the shelf water region of the Bering Sea in May, remarkably dense populations ofThalassiosira hyalina andT. nordenskiöldii and relatively large populations ofFragilaria andNavicula occupied large part of phytoplankton community. In June, although theThalassiosira populations sunk into the bottom layer and withered, a certain part of theFragilaria-Navicula populations was still suspended in subsurface layer. Thus,Fragilaria-Navicula were the leading components of the June community in the shelf region.In the Bering Basin region, no dense phytoplankton populations were developed until a shallow thermocline was established. In June when the shallow thermocline developed near shelf edge,Thalassiosira decipiens burst out. As the shallow thermocline extended from near shelf to central part of the Basin region with surface warming, the areas of blooming also shifted from near shelf to the central part.Contribution No. 73 from the Research Institute of North Pacific Fisheries, Hokkaido University.     

Interannual and regional variability in distribution and ecology of juvenile pollock and their prey in frontal structures of the Bering Sea

The distribution, size, length-specific weight, growth, and feeding of age-0 walleye pollock (Theragra chalcogramma) were examined along with their prey distribution patterns in two contrasting transects over a 4-year period (1994–1997) in relation to biophysical properties of frontal regions around the Pribilof Islands, Bering Sea. There were significant interannual differences in catch of age-0 pollock, but transect and habitat differences (inshore vs. front vs. offshore) were not significant for either catch or size of pollock. There were significant variations in length-specific weight and growth of pollock, but the trends were inconsistent. Copepods dominated the zooplankton biomass in all habitats and years; there were no consistent differences in the densities of the dominant zooplankton taxa among the habitats. There were, however, strong habitat and transect differences in juvenile pollock diet, particularly for the larger and presumably rarer prey taxa (euphausiids, chaetognaths, fish). We did not find any evidence that occupying a particular habitat was beneficial to young pollock, although other factors (e.g. bioenergetic advantage and predation refuge) that we did not examine here could have been more variable and critical to pollock survival. In a physically dynamic system such as the Pribilof Islands, age-0 pollock may need to continuously search for optimal conditions of high prey availability and low predation pressure.     

Interannual variability of dimethylsulfide in the Yellow Sea

The 22-year(1998–2019) surface seawater dimethylsulfide(DMS) concentrations in the Yellow Sea(YS) were hindcasted based on satellite sea surface temperature(SST) and chlorophyll-a(Chl-a) data using a generalized additive mixed model(GAMM). A continuous monthly dataset of DMS concentration in the YS was obtained after using the data interpolation empirical orthogonal function(DINEOF) to reconstruct missing information in the dataset. Then, the interannual DMS variability in the YS was analyzed. T...     

On the recent warming of the southeastern Bering Sea shelf

During the last decade, the southeastern Bering Sea shelf has undergone a warming of 3 °C that is closely associated with a marked decrease of sea ice over the area. This shift in the physical environment of the shelf can be attributed to a combination of mechanisms, including the presence over the eastern Bering Sea shelf of a relatively mild air mass during the winter, especially from 2000 to 2005; a shorter ice season caused by a later fall transition and/or an earlier spring transition; increased flow through Unimak Pass during winter, which introduces warm Gulf of Alaska water onto the southeastern shelf; and the feedback mechanism whereby warmer ocean temperatures during the summer delay the southward advection of sea ice during winter. While the relative importance of these four mechanisms is difficult to quantify, it is evident that for sea ice to form, cold arctic winds must cool the water column. Sea ice is then formed in the polynyas during periods of cold north winds, and this ice is advected southward over the eastern shelf. The other three mechanisms can modify ice formation and melt, and hence its extent. In combination, these four mechanisms have served to temporally and spatially limit ice during the 5-year period (2001–2005). Warming of the eastern Bering Sea shelf could have profound influences on the ecosystem of the Bering Sea—from modification of the timing of the spring phytoplankton bloom to the northward advance of subarctic species and the northward retreat of arctic species.     

Interannual to decadal Gulf Stream variability in an eddy-resolving ocean model

Meridional shifts of the Gulf Stream (GS) jet on interannual to decadal timescales and the corresponding oceanic changes around the GS are investigated using a near global eddy-resolving ocean model hindcast from 1960 to 2003. The simulated variability in the shifts of the GS jet axis shows good agreement with observations, and lags atmospheric fluctuations characterized by the North Atlantic Oscillation by about 2 years. This lagged response of the GS jet to the atmospheric variations is attributed to the westward propagation of the undulation of the jet axis from 45°W to 75°W, which has a wavelength of about 4000 km and a displacement of 0.5°. The propagation direction and phase speed of about 2.8 cm s⁻¹ are consistent with the thin-jet theory. The shifts of the jet axis in the downstream region are likely induced by wind fluctuations through Ekman convergence over the central North Atlantic. Associated with the northward (southward) shift of the jet axis, sea surface temperature is warming (cooling) around and north of the jet, and the former warming has a deep and meridionally narrow subsurface structure, consistent with the northward shift of the jet. The meridional shifts of the jet accompany coherent meridional shifts of energetic eddy activity regions around the GS. Our numerical results suggest that the GS jet brings the atmospheric signals from the central to the western North Atlantic, and the resultant meridional shift of the jet induces the notable oceanic changes around the GS.     

白令海2008年冬夏季节陆架水的差异

本文利用中国海洋大学极地变化重点实验室提供的2008年3月与7月白令海陆架水资料,对白令海200 m内水域温盐及水团进行了分析和对比,对白令海陆架区冬季水团形成机制做了初步的探讨。白令海冬季陆架水的温盐结构垂向均匀;夏季层化明显,存在垂直温盐跃层;白令海由夏季表层水和冬季水两种水团组成;白令海冬季残留水团在陆架区水深20 m处即出现,最低温度较大洋深处冬季水温偏低。     

Water masses and decadal variability in the East Sea (Sea of Japan)

Water masses in the East Sea are newly defined based upon vertical structure and analysis of CTD data collected in 1993–1999 during Circulation Research of the East Asian Marginal Seas (CREAMS). A distinct salinity minimum layer was found at 1500 m for the first time in the East Sea, which divides the East Sea Central Water (ESCW) above the minimum layer and the East Sea Deep Water (ESDW) below the minimum layer. ESCW is characterized by a tight temperature–salinity relationship in the temperature range of 0.6–0.12 °C, occupying 400–1500 m. It is also high in dissolved oxygen, which has been increasing since 1969, unlike the decrease in the ESDW and East Sea Bottom Water (ESBW). In the eastern Japan Basin a new water with high salinity in the temperature range of 1–5 °C was found in the upper layer and named the High Salinity Intermediate Water (HSIW). The origin of the East Sea Intermediate Water (ESIW), whose characteristics were found near the Korea Strait in the southwestern part of the East Sea in 1981 [Kim, K., & Chung, J. Y. (1984) On the salinity-minimum and dissolved oxygen-maximum layer in the East Sea (Sea of Japan), In T. Ichiye (Ed.), Ocean Hydrodynamics of the Japan and East China Seas (pp. 55–65). Amsterdam: Elsevier Science Publishers], is traced by its low salinity and high dissolved oxygen in the western Japan Basin. CTD data collected in winters of 1995–1999 confirmed that the HSIW and ESIW are formed locally in the Eastern and Western Japan Basin. CREAMS CTD data reveal that overall structure and characteristics of water masses in the East Sea are as complicated as those of the open oceans, where minute variations of salinity in deep waters are carefully magnified to the limit of CTD resolution. Since the 1960s water mass characteristics in the East Sea have changed, as bottom water formation has stopped or slowed down and production of the ESCW has increased recently.     

Collaborative research on the pelagic ecosystem of the southeastern Bering Sea shelf

Two Bering Sea marine research programs collaborated during the final years of the 1990s to forge advances in understanding the southeastern Bering Sea pelagic ecosystem. Southeast Bering Sea Carrying Capacity, sponsored by NOAA Coastal Ocean Program, investigated processes on the middle and outer shelf and the continental slope. The Inner Front Program, sponsored by NSF, investigated processes of the inner domain and the front between the inner and middle domains. The purposes of these programs were to (1) increase understanding of the southeastern Bering Sea ecosystem, including the roles of juvenile walleye pollock, (2) investigate the hypothesis that elevated primary production at the inner front provides a summer-long energy source for the food web, and (3) develop and test annual indices of pre-recruit pollock abundance. The observations occurred during a period of unusually large variability in the marine climate, including a possible regime shift. Sea-ice cover ranged from near zero to one of the heaviest ice years in recent decades. Sea-surface temperatures reached record highs during summer 1997, whereas 1999 was noted for its low Bering Sea temperatures. Moreover, the first recorded observations of coccolithophore blooms on the shelf were realized in 1997, and these blooms now appear to be persistent. The programs’ results include an archive of physical and biological time series that emphasize large year-to-year regional variability, and an Oscillating Control Hypothesis that relates marine productivity to climate forcing. Further investigations are needed of the confluences of interannual and even intra-seasonal variability with low-frequency climate variability as potential producers of major, abrupt changes in the southeastern Bering Sea ecosystem.     

Stoichiometry among bioactive trace metals in seawater on the Bering Sea shelf

The distribution of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater was investigated on the Bering Sea shelf (56–64°N, 165–169°W) in September 2000. The unfiltered and filtered seawater samples were used for determination of total dissolvable (TD) and dissolved (D) metals (M), respectively. The TD-M concentrations were generally higher than in the Pacific Ocean. TD-Cd was highest in deep water of the outer shelf domain and dominated by dissolved species. The other TD-M were highest at stations close to the Yukon River delta and had higher fractions of labile particulate (LP) species that were obtained as the difference between TD-M and D-M. Dissolved Al, Ni, and Cu were characterized by input from the Yukon River. Dissolved Mn and Co showed maximums on the bottom of the coastal domain, suggesting influence of sedimentary Mn reduction. The correlations of D-Zn, D-Cd, and macronutrients indicated their distributions were largely controlled through uptake by microorganisms and remineralization from settling particles. All these three processes (river input, sedimentary reduction, and biogeochemical cycle) had an influence on the distribution of D-Fe. D-Pb was fairly uniformly distributed in the study area. The stoichiometry of D-M in the Bering Sea shelf showed enrichment of Co and Pb and depletion of Ni, Cu, Zn, and Cd compared with that in the North Pacific. The LP-M/LP-Al ratio revealed significant enrichment of the other eight metals relative to their crustal abundance, suggesting importance of formation of Fe–Mn oxides and adsorption of trace metals on the oxides.     

南黄海浮游动物主要种类数量分布年间比较

分析对比1959年、1982年、1998-2000年以及2007-2010年4个不同时期南黄海中部（34.25°~37.45°N,122.00°~124.00°E）浮游动物主要优势种中华哲水蚤（Calanus sinicus）、太平洋磷虾（Euphausia pacifica）和强壮箭虫（Sagitta crassa）数量时空变化及其与温度、盐度和太平洋年代际震荡指数（Pacific Decadal Oscillation,PDO）变动的关系。结果显示,温度可能对中华哲水蚤和太平洋磷虾数量分布影响较大;强壮箭虫则受盐度影响较大。PDO暖位相时期中华哲水蚤和太平洋磷虾数量显著低于冷位相时期,强壮箭虫则相反。中华哲水蚤和太平洋磷虾丰度与提前3个月PDO值呈显著正相关,强壮箭虫丰度仅与当月PDO值呈显著正相关。     

北黄海獐子岛海域浮游动物群落年际变化

本文比较了海洋普查期间（1959年1-12月）和2009-2010年獐子岛海域附近站位的浮游动物的种类组成、优势种、丰度、生物多样性,结果显示,北黄海区域浮游动物群落物种组成未发生较大的变化,在獐子岛海域以及整个北黄海,中华哲水蚤和强壮箭虫的优势种地位没有发生变化,细足法虫戎也一直出现且为冬春季的优势种;太平洋磷虾在2009-2010年獐子岛海域虽然全年均有出现,但是全年均不是优势种,而在1959年的獐子岛海域,作为优势种出现在4月和11月;1959年与2009年相较,腹针胸刺水蚤在春夏季优势种的地位被沃氏纺锤水蚤所取代。2009年浮游动物丰度（131.26 ind/m3）比1959年（78.90 ind/m3）高;浮游动物多样性指数（H'）均在夏秋季高于冬春季节,且年平均多样性指数也有所提高。     

Seasonal and Interannual Variability of Chlorophyll-a Concentration in the Bering Sea Found from Satellite Data

Izvestiya, Atmospheric and Oceanic Physics - This study characterizes the spatiotemporal variability of chlorophyll-a in the Bering Sea and adjacent Pacific Ocean based on 2003–2019 MODIS...     

Community structure and spatial distribution of macrobenthos in the shelf area of the Bering Sea

Field investigations of marine macrobenthos were conducted at ten sites in the Bering Sea in July 2010. Altogether 90 species of macrobenthos belonging to 59 families and 78 genera were identified. Among them, 41 polychaetes, 16 mollusks, 23 crustaceans, three echinoderms, two cnidarians, one nemertean, one priapulid, two sipunculids, and one echiuran were identified. The average density and biomass of total macrobenthos were 984 ind./m2 and 1 207.1 g/m2 of wet weight, respectively. The predominant species in the study area were Scoloplos armiger, Eudorella pacifica, Ophiura sarsii, Heteromastus filiformis, Ennucula tenuis, and Harpiniopsis vadiculus by abundance, while the predominant species in this area was Echinarachnius parma by biomass. Hierarchical cluster analysis(Bray–Curtis similarity measure) revealed that two important benthic assemblages in the study area were Community A and Community B. Community A was stable and Community B was unstable, as shown by the Abundance/Biomass Comparisons(ABC) approach. The macrobenthic community structure in the shelf of the Bering Sea was characterized by its high abundance and biomass, high productivity but great heterogeneity.     

Interannual variability of the Kuroshio intrusion in the South China Sea

The interannual variability of intrusions of the Kuroshio into the South China Sea (SCS) is investigated using satellite remote sensing data supported by in-situ measurements. The mesoscale circulation of the SCS is predominantly wind-forced by the northeast winter and southwest summer monsoons. Although the region has been studied extensively, considerable uncertainty remains about the annual and interannual mesoscale nature of the circulation. The frequency and characteristics of Kuroshio intrusions and their effect on circulation patterns in the northeast SCS are also not well understood. Satellite observations of Sea Surface Temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Very High Resolution Radiometer (AVHRR) and Sea Surface Height Anomalies (SSHA) from TOPEX/ Poseidon for the period 1997–2005 are used here to analyze the annual and interannual variability in Kuroshio intrusions and their effects on the region. Analysis of SST and SSHA shows the formation and characteristics of intrusions vary considerably each year. Typically, the intrusion occurs in the central region of Luzon Strait and results in an anticyclonic circulation in the northeastern SCS. However, in some years, the intrusion is located in the northern portion of Luzon Strait and a cyclonic intrusion results. Wind stress and wind stress curl derived from the National Aeronautics and Space Administration (NASA) QuikSCAT satellite scatterometer are used to evaluate the relationship between wind stress or wind stress curl and the presence of winter Kuroshio intrusions into the SCS.     

Interannual to decadal variability of the Kuroshio Current in the East China Sea from 1955 to 2010 as indicated by in-situ hydrographic data

The temporal and spatial variability of the Kuroshio Current was analyzed. Current data were estimated from hydrographic data collected from areas within the central East China Sea (PN section) from 1955 to 2010 and the Tokara Strait (TK section) from 1987 to 2010. To reduce the bias caused by cruise-dependent spatial resolution among the data, grid-consistent temperature and salinity fields were reconstructed by use of a regression relationship to account for anomalies between observed stations and grid points. The mass imbalance problem between the PN and TK sections, which appears stochastically when viewed by use of the dynamic method, was solved by use of the inverse method. The estimated Kuroshio volume transport (KVT) was found to be closely consistent with that of current observations and had an uncertainty of 2.4 Sv. The KVT seemed to have neither a regime shift in approximately 1976 nor a sharply increasing trend. The KVT was dominated by 2–5 year modulating interannual variability with an amplitude of 2.8 Sv, followed by weak 20-year decadal variability with an amplitude of 0.33 Sv. Empirical orthogonal function analysis of the currents suggested that the temporal and spatial variability of the Kuroshio Current in the PN section was dominated by a transport mode, manifested by the high variability of current on the seaward side of current core with expansion or shrinkage of the core. In contrast, the temporal and spatial variability of the Kuroshio Current in the TK section was dominated by a meandering mode, as indicated by the migration of the Kuroshio axis in the south gap of the Tokara Strait.     

Characteristics and variability of the inner front of the southeastern Bering Sea

The inner front of the southeastern Bering Sea shows marked spatial variability in frontal characteristics created by regional differences in forcing mechanisms. Differences in forcing mechanisms (sea ice advance/retreat and storm strength and timing) and early spring water properties result in strong interannual variability in biological, chemical, and physical features near the front. We have developed a simple model based on surface heat flux and water-column mixing to explain the existence of cold belts (Cont. Shelf Res. 19(14) (1999) 1833) associated with such fronts. Hydrography, fluorescence and nutrient observations show that pumping of nutrients into the euphotic zone occurs, and this can prolong primary production at the inner front. The effectiveness of this process depends on two factors: the existence of a reservoir of nutrients in the lower layer on the middle shelf and the occurrence of sufficient wind and tidal energy to mix the water column.