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Sample records for bering sea sediments

  1. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The skies of the Bering Sea were relatively clear again in this SeaWiFS image showing a band of aquamarine colored water. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  2. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Much of the Bering Sea is clear in this SeaWiFS image. The large expanse of bright aquamarine water is clearly visible. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  3. Structure and sediment distribution in the western Bering Sea

    USGS Publications Warehouse

    Rabinowitz, P. D.; Cooper, A.

    1977-01-01

    Eleven seismic reflection profiles across Shirshov Ridge and the adjacent deep-water sedimentary basins (Komandorsky and Aleutian Basins) are presented to illustrate the sediment distribution in the western Bering Sea. A prominent seismic reflecting horizon, Reflector P (Middle-Late Miocene in age), is observed throughout both the Aleutian and Komandorsky Basins at an approximate subbottom depth of 1 km. This reflector is also present, in places, on the flanks and along the crest of Shirshov Ridge. The thickness of sediments beneath Reflector P is significantly different within the two abyssal basins. In the Aleutian Basin, the total subbottom depth to acoustic basement (basalt?) is about 4 km, while in the Komandorsky Basin the depth is about 2 km. Shirshov Ridge, a Cenozoic volcanic feature that separates the Aleutian and Komandorsky Basins, is an asymmetric bathymetric ridge characterized by thick sediments along its eastern flank and steep scarps on its western side. The southern portion of the ridge has more structural relief that includes several deep, sediment-filled basins along its summit. Velocity data from sonobuoy measurements indicate that acoustic basement in the Komandorsky Basin has an average compressional wave velocity of 5.90 km/sec. This value is considerably larger than the velocities measured for acoustic basement in the northwestern Aleutian Basin (about 5.00 km/sec) and in the central Aleutian Basin (5.40-5.57 km/sec). In the northwestern Aleutian Basin, the low-velocity acoustic basement may be volcaniclastic sediments or other indurated sediments that are overlying true basaltic basement. A refracting horizon with similar velocities (4.6-5.0 km/sec) as acoustic basement dips steeply beneath the Siberian continental margin, reaching a maximum subbottom depth of about 8 km. The thick welt of sediment at the base of the Siberian margin may be the result of sediment loading or tectonic depression prior to Late Cenozoic time. ?? 1977.

  4. A climate-related oxidizing event in deep-sea sediment from the Bering Sea

    USGS Publications Warehouse

    Gardner, J.V.; Dean, W.E.; Klise, D.H.; Baldauf, J.G.

    1982-01-01

    Many cores from the deep basins of the Bering Sea have a thin oxidized zone within otherwise reduced sediment. This oxidized zone began to form about 6000 yr ago and represents an interval of about 3200 yr. Mineralogically, the oxidized and reduced sediments are similar, but chemically they differ. Concentrations of Fe and C are lower, and concentrations of Mn, Ba, Co, Mo, and Ni are higher in the oxidized than in the reduced sediment. Mn is enriched about 10-fold in the oxidized zone relative to its concentration in the reduced sediment, Mo about threefold, and Ba, Co, and Ni about twofold. These data suggest that the oxidized zone developed diagenetically as the result of the balance between the flux of organic matter and the available dissolved oxygen in bottom and interstitial waters. We propose that the Bering Sea was substantially ice covered when global glacial conditions prevailed. during the transition to global interglacial conditions, seasonal meltwater from thawing sea ice formed a lens of fresh water that decreased organic productivity. During the winter seasons, however, sea ice reformed and caused downwelling of dense, oxygen-rich waters to recharge bottom waters. The combination of lower organic productivity and more oxygen-rich bottom water allowed oxidized sediment to accumulate. Once full interglacial conditions were established, the volume of sea ice produced was insufficient to affect either productivity or the supply of dissolved oxygen and so bottom conditions again became reducing. Similar events probably occurred during the onset of global glacial conditions, and similar oxidized layers probably formed at these times. Such oxidized zones are highly unstable, however, in a reducing environment and, once buried beyond the influence of bacterial and infaunal activities, are depleted of their available oxygen and converted to reduced sediment. ?? 1982.

  5. Mercury distribution in ancient and modern sediments of northeastern Bering Sea

    USGS Publications Warehouse

    Nelson, C. Hans; Pierce, D.E.; Leong, K.W.; Wang, F.F.

    1972-01-01

    A reconnaissance of surface and subsurface sediments to a maximum depth of 244 feet below the sea floor shows that natural mercury anomalies from 0.2 to 1.3 ppm have been present in northeastern Bering Sea since early Pliocene. The anomalies and mean values are highest in modern beach (maximum 1.3 and mean 0.22 ppm Hg) and nearshore subsurface gravels (maximum 0.6 and mean .06 ppm Hg) along the highly mineralized Seward Peninsula and in organic rich silt (maximum 0.16 and mean 0.10 ppm Hg) throughout the region; the mean values are lowest in offshore sands (0.03 ppm Hg) . Although gold mining may be partially responsible for high mercury levels in the beaches near Nome, Alaska, equally high or greater concentrations of mercury occur in ancient glacial sediments immediately offshore (0.6 ppm) and in modern unpolluted beach sediments at Bluff (0.45 - 1.3 ppm); this indicates that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The background content of mercury (0.03) throughout the central area of northeastern Bering Sea is similar to that elsewhere in the world. The low mean values (0.04 ppm) even immediately offshore from mercury-rich beaches, suggests that in the surface sediments of northeastern Bering Sea, the highest concentrations are limited to the beaches near mercury sources; occasionally, however, low mercury anomalies occur offshore in glacial drift derived from mercury source regions of Chukotka and Seward Peninsula and reworked by Pleistocene shoreline processes. The minimal values offshore may be attributable to beach entrapment of heavy minerals containing mercury and/or dilution effects of modern sedimentation.

  6. Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments from the Bering Sea and western Arctic Ocean.

    PubMed

    Zhao, Mengwei; Wang, Weiguo; Liu, Yanguang; Dong, Linsen; Jiao, Liping; Hu, Limin; Fan, Dejiang

    2016-03-15

    To analyze the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) and evaluate their potential ecological risks, the concentrations of 16 PAHs were measured in 43 surface sediment samples from the Bering Sea and western Arctic Ocean. Total PAH (tPAH) concentrations ranged from 36.95 to 150.21 ng/g (dry weight). In descending order, the surface sediment tPAH concentrations were as follows: Canada Basin>northern Chukchi Sea>Chukchi Basin>southern Chukchi Sea>Aleutian Basin>Makarov Basin>Bering Sea shelf. The Bering Sea and western Arctic Ocean mainly received PAHs of pyrogenic origin due to pollution caused by the incomplete combustion of fossil fuels. The concentrations of PAHs in the sediments of the study areas did not exceed effects range low (ERL) values.

  7. Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea

    USGS Publications Warehouse

    Gardner, J.V.; Dean, W.E.; Vallier, T.L.

    1980-01-01

    Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian

  8. SEISMIC AND GEOCHEMICAL EVIDENCE FOR SHALLOW GAS IN SEDIMENT ON NAVARIN CONTINENTAL MARGIN, BERING SEA.

    USGS Publications Warehouse

    Carlson, Paul R.; Golan-Bac, Margaret; Karl, Herman A.; Kvenvolden, Keith A.

    1985-01-01

    Marine sesmic studies coupled with geochemical investigations demonstrate tha hydrocarbon gases are ubiquitous in the near-surface sediment of the Navarin continental margin in the northern Bering Sea. Three types of acoustic anomalies appear to be related to the presence of gas in the sediment. These anomalies are most prevalent in the northern half of the Navarin basin. Acoustic anomalies attributed to gas hydrates and to diagenetic boundaries are present on seismic records of the lower slope between Navarinsky and Zhemchug Canyons. Hydrocarbon gases, methane through butanes, are common in the surface sediment of the Navarin continental margin. The source of methane is mainly biogenic, but the hydrocarbon gas compositions in 17 of 141 cores suggest the presence of thermogenic gas. No direct correlation could be found between acoustic anomalies and gas concentrations in the sediment. Refs.

  9. Geotechnical characteristics of bottom sediments in the northeastern Bering Sea.

    USGS Publications Warehouse

    Olsen, H.W.; Clukey, E.C.; Nelson, C.H.

    1982-01-01

    Sediment of Holocene age derived from the Yukon River, consisting dominantly of silty fine sand and sandy silt, covers the bottom of central and western Norton Sound, which is a high energy environment involving extensive ice loading, high waves, and strong bottom currents. The sediment characteristics indicate that it is susceptible to liquefaction during major storms. Substantially finer grained, weak and highly compressible sediment of Holocene age covers eastern Norton Sound and the Port Clarence embayment, which are low energy environments. Pleistocene peaty deposits underlie the Holocene and late Pleistocene deposits in both Norton Sound and Chirikov Basin and are somewhat overconsolidated. The presence of gas indicates high in situ pore pressure and hence low material strength.-from Authors

  10. Distribution and enantiomeric profiles of organochlorine pesticides in surface sediments from the Bering Sea, Chukchi Sea and adjacent Arctic areas.

    PubMed

    Jin, Meiqing; Fu, Jie; Xue, Bin; Zhou, Shanshan; Zhang, Lina; Li, An

    2017-03-01

    The spatial distribution, compositional profiles, and enantiomer fractions (EFs) of organochlorine pesticides (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes (CHLs), in the surface sediments in the Bering Sea, Chukchi Sea and adjacent areas were investigated. The total concentrations of DDTs, HCHs and CHLs varied from 0.64 to 3.17 ng/g dw, 0.19-0.65 ng/g dw, and 0.03-0.16 ng/g dw, respectively. No significant difference was observed between the Bering Sea and Chukchi Sea for most pollutants except for trans-CHL, ΣCHLs (sum of trans- and cis-chlordane) and p,p'-DDD. Concentration ratios (e.g., α-HCH/γ-HCH, o,p'-DDT/p,p'-DDT) indicated that the contamination in the studied areas may result from inputs from multiple sources (e.g., historical usage of technical HCHs as well as new input of dicofol). Chiral analysis showed great variation in the enantioselective degradation of OCPs, resulting in excess of (+)-enantiomer for α-HCH in thirty of the 32 detectable samples, preferential depletion of (-)-enantiomer for o,p'-DDT in nineteen of the 35 detectable samples, and nonracemic in most samples for trans- and cis-chlordane. The ecological risks of the individual OCPs as well as the mixture were assessed based on the calculation of toxic units (TUs), and the results showed the predominance of DDT and γ-HCH in the mixture toxicity of the sediment. Overall, the TUs of OCPs in sediments from both the Bering and Chukchi Seas are less than one, indicating low ecological risk potential.

  11. Mercury distribution in ancient and modern sediment of northeastern Bering Sea

    USGS Publications Warehouse

    Nelson, C.H.; Pierce, D.E.; Leong, K.W.; Wang, F.F.H.

    1975-01-01

    Reconnaissance sampling of surface and subsurface sediment to a maximum depth of 80 m below the sea floor shows that typical values of 0.03 p.p.m. and anomalies of 0.2-1.3 p.p.m. mercury have been present in northeastern Bering Sea since Early Pliocene time. Values are highest in modern beach (maximum 1.3 and mean 0.22 p.p.m. Hg) and nearshore subsurface gravels (maximum 0.6 and mean 0.06 p.p.m. Hg) along the highly mineralized Seward Peninsula and in clayey silt rich in organic matter (maximum 0.16 and mean 0.10 p.p.m. Hg) throughout the region. Although gold mining may be partly responsible for high mercury levels in the modern beach near Nome, Alaska (maximum 0.45 p.p.m.), equally high or greater concentrations of mercury occur in buried Pleistocene sediments immediately offshore (maximum 0.6 p.p.m.) and in modern unpolluted beach sediments at Bluff (maximum 1.3 p.p.m.); this suggests that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The mercury content of offshore surface sediment, even adjacent to mercury-rich beaches, corresponds to that of unpolluted marine and fresh-water sediment elsewhere. The normal values that prevail offshore may be attributable to entrapment of mercury-bearing heavy minerals on beaches near sources and/or dilution effects of offshore sedimentation. The few minor anomalies offshore occur in glacial drift derived from mercury source regions of Chukotka (Siberia) and Seward Peninsula; Pleistocene shoreline processes have reworked the drift to concentrate the heavy metals. The distribution pattern of mercury indicates that particulate mercury-bearing minerals have not been widely dispersed from onland deposits in quantities sufficient to increase mercury levels above normal in offshore sediments of Bering Sea; however, it shows that natural sedimentary processes can concentrate this mercury in beaches of the coastal zone where there already is concern because of

  12. Surface current patterns suggested by suspended sediment distribution over the outer continental margin, Bering Sea

    USGS Publications Warehouse

    Karl, Herman A.; Carlson, P.R.

    1987-01-01

    Samples of total suspended matter (TSM) were collected at the surface over the northern outer continental margin of the Bering Sea during the summers of 1980 and 1981. Volume concentrations of surface TSM averaged 0.6 and 1.1 mg l-1 for 1980 and 1981, respectively. Organic matter, largely plankton, made up about 65% of the near-surface TSM for both years. Distributions of TSM suggested that shelf circulation patterns were characterized either by meso- and large- scale eddies or by cross-shelf components of flow superimposed on a general northwesterly net drift. These patterns may be caused by large submarine canyons which dominate the physiography of this part of the Bering Sea continental margin. ?? 1987.

  13. Distribution of polybrominated diphenyl ethers and decabromodiphenylethane in surface sediments from the Bering Sea, Chukchi Sea, and Canada Basin

    NASA Astrophysics Data System (ADS)

    Cai, M. G.; Hong, Q. Q.; Wang, Y.; Luo, X. J.; Chen, S. J.; Cai, M. H.; Qiu, C. R.; Huang, S. Y.; Mai, B. X.

    2012-12-01

    24 surface sediment samples were collected from the Bering Sea, Chukchi Sea, and Canada Basin during the 3rd Chinese National Arctic Research Expedition in July-September 2008. To obtain information on the levels, spatial distribution, possible sources, and influences of total carbon and black carbon, we analyzed the samples for polybrominated diphenyl ethers (PBDEs) and decabromodiphenylethane (DBDPE). Concentrations of ∑PBDEs (hereafter, ∑PBDEs refers to the sum of all detected PBDE congeners without BDE-209), BDE-209, and DBDPE were in the ranges 3.58-148.95 pg/g d.w. (dry weight), n.d. -804.91 pg/g d.w. and n.d. -452.57 pg/g d.w., respectively. The congener patterns of PBDEs suggested that BDE-209 was the major congener in these areas, followed by BDE-99 and -47, which was consistent with the predominance of technical deca-BDE mixtures in the dominant technical PBDE mixtures. The significant relationships of BDE-209, -47, and -99 and total PBDEs with total organic carbon and black carbon, as well as the skewed distribution of ∑PBDEs and BDE-209, indicated that atmospheric deposition and local discharge might be potential sources in this area, and the distribution pattern may be the combined effect of multiple factors.

  14. Distribution of detrital minerals and sediment color in western Arctic Ocean and northern Bering Sea sediments: Changes in the provenance of western Arctic Ocean sediments since the last glacial period

    NASA Astrophysics Data System (ADS)

    Kobayashi, Daisuke; Yamamoto, Masanobu; Irino, Tomohisa; Nam, Seung-Il; Park, Yu-Hyeon; Harada, Naomi; Nagashima, Kana; Chikita, Kazuhisa; Saitoh, Sei-Ichi

    2016-12-01

    This paper describes the distribution of detrital minerals and sediment color in the surface sediments of the western Arctic Ocean and the northern Bering Sea and investigates the relationship between mineral composition and sediment provenance. This relationship was used to determine the provenance of western Arctic Ocean sediments deposited during the last glacial period. Sediment color is governed by water depth, diagenesis, and mineral composition. An a*-b* diagram was used to trace color change during diagenesis in the Arctic Ocean sediments. The mineral composition of surface sediments is governed by grain size and provenance. The feldspar/quartz ratio of the sediments studied was higher on the Siberian side than on the North American side of the western Arctic Ocean. The (chlorite + kaolinite)/illite and chlorite/illite ratios were high in the Bering Sea but decrease northwards in the Chukchi Sea. Thus, these ratios are useful for provenance studies in the Chukchi Sea area as indices of the Beaufort Gyre circulation and the Bering Strait inflow. The sediments deposited during the last glacial period have a lower feldspar/quartz ratio and a higher dolomite intensity than Holocene sediments on the Chukchi Plateau, suggesting a greater contribution of North American grains during the last glacial period.

  15. Alaska and Bering Sea Bloom

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Alaska was relatively clear as was part of the Bering Sea where the aquamarine bloom is still visible in this SeaWiFS image. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  16. New Method for the Quantitative Analysis of Smear Slides in Pelagic and Hemi-Pelagic Sediments of the Bering Sea

    NASA Astrophysics Data System (ADS)

    Drake, M. K.; Aiello, I. W.; Ravelo, A. C.

    2014-12-01

    Petrographic microscopy of smear slides is the standard method to initially investigate marine sediments in core sediment studies (e.g. IODP expeditions). The technique is not commonly used in more complex analysis due to concerns over the subjectivity of the method and variability in operator training and experience. Two initiatives sponsored by Ocean Leadership, a sedimentology training workshop and a digital reference of smear slide components (Marsaglia et al., 2013) have been implemented to address the need for advanced training. While the influence of subjectivity on the quality of data has yet to be rigorously tested, the lack of standardization in the current method of smear slide analysis (SSA) remains a concern. The relative abundance of the three main components, (total diatoms, silt-to-sand sized siliciclastics, and clay minerals) of high and low density Bering Sea hemi-pelagic sediments from the ocean margin (Site U144; Site U1339) and pelagic sediments from the open-ocean (Site U1340) were analyzed. Our analyses show visual estimation is a reproducible method to quantify the relative abundance of the main sediment components. Furthermore, we present a modified method for SSA, with procedural changes objectively guided by statistical analyses, including constraints to increase randomness and precision in both the preparation and analysis of the smear slide. For example, repeated measure ANOVAs found a smear slide could be accurately quantified by counting three fields of view. Similarly, the use of replicate smear slides to quantify a sample was analyzed. Finally, the data produced from this modified SSA shows a strong correlation to continuously logged physical parameters of sediment such as gamma ray attenuation (Site U1339 r2= 0.41; Site U1340 r2= 0.36). Therefore, the modified SSA combined with other independent methods (e.g. laser particle size analysis, scanning electron microscopy, and physical properties) can be a very effective tool for the

  17. Plio-Pleistocene Bering Sea - North Pacific Ocean Circulation Dynamics Inferred from Sediment Source Changes at the Meiji Drift, Northwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Vanlaningham, S.; Haley, B.; Hillier, S.; Alizai, A. H.

    2010-12-01

    The Pliocene is an interesting time in Earth’s history because it was warmer than today and could serve as an analog for how Earth might behave in response to future warming. It also precedes the onset of Northern Hemisphere glaciation that started ~3 million years ago. Yet it remains an open question whether closing of the Isthmus of Panama and opening of the Bering Strait impacted ocean circulation and climate 4-5 Ma. A large drift deposit in the northwest Pacific known as the Meiji Drift may hold clues about the possible impact of the Bering gateway on Pliocene climate dynamics in the Northern Hemisphere. It was previously demonstrated that the Meiji Drift is sensitive to changes at the Bering Strait, at least over the last 150 ka. This work investigates Plio-Pleistocene changes at the Meiji Drift using mineralogical and bulk sediment Nd isotopic techniques applied to the terrigenous fraction. Quantitative mineralogy of Meiji Drift sediment shows significant changes in quartz, plagioclase, K-feldspar, and amphibole at 5 Ma as well as around 1.5-2 Ma. Nd isotopic data show a transition from epsilon Nd values of +8 at 5 Ma to +1 by 3 Ma. These data suggest that circum-Pacific arc rocks were the dominant source of terrigenous sediment to the Meiji Drift around 5 Ma. From 5 to 3 Ma the sediment became progressively mixed with more continental-like source rocks. It is likely that increased flow from the Bering Sea (dominated by detritus from the Yukon River) to the North Pacific occurred ~5 Ma. This coincides with when the Bering Strait likely first opened with southward flow. But after the onset of Northern Hemisphere glaciation the sediment sources to the Meiji Drift likely began to oscillate at higher frequency with the opening and closing of the Bering gateway on glacial-interglacial timescales. Higher resolution work on the detrital fraction of the Meiji Drift will better constrain the timing, magnitude, and direction of ocean circulation changes in the Bering

  18. The benthic fauna of the Northern Bering Sea

    USGS Publications Warehouse

    Rowland, Robert W.

    1973-01-01

    the Macoma balthica community which inhabits the brackish coastal lagoons. These associations were compared with the classic boreal benthic communities of Peterson & Thorson. Although the Bering Sea fauna is compositionally similar to the Scandinavian, the species associations differ markedly. These differences are believed to be due to substrate differences. The Bering Sea sediments are more poorly sorted and patchily distributed than those of Scandinavian waters.

  19. Coupled nitrification-denitrification in sediment of the eastern Bering Sea shelf leads to 15N enrichment of fixed N in shelf waters

    NASA Astrophysics Data System (ADS)

    Granger, J.; Prokopenko, M. G.; Sigman, D. M.; Mordy, C. W.; Morse, Z. M.; Morales, L. V.; Sambrotto, R. N.; Plessen, B.

    2011-11-01

    We studied the nitrogen biogeochemistry of the ice-covered eastern Bering Sea shelf using the isotope ratios (15N/14N and 18O/16O) of NO3- and other N species. The 15N/14N of late winter NO3- on the shelf decreases inshore and is inversely correlated with bottom water [NH4+], consistent with an input of low-15N/14N NO3- from partial nitrification of NH4+ remineralized from the sediments. An inshore 15N/14N increase in total dissolved N (TDN) suggests that (1) the sediment-derived NH4+ is elevated in 15N due to the same partial nitrification that yields the low-15N/14N NO3-, and (2) 15N-deplete NO3- from partial nitrification within the sediments is denitrified to N2. The proportion of newly nitrified NO3- on the shelf, evidenced by an inshore decrease in NO3- 18O/16O, is correlated with the N deficit, further implicating nitrification coupled to denitrification; however, a simple N isotope budget indicates a comparable rate of denitrification supported by diffusion of NO3- into the sediments. The isotopic impact of benthic N loss is further demonstrated by a correlation between the 15N/14N of shelf surface sediment and the N deficit of the overlying water column, both of which increase inshore and northward, as well as by Arctic NO3- isotope data indicating that the fixed N transported through Bering Strait has a 15N/14N higher than is found in the open Bering Sea. The significant net isotope effect of benthic N loss on the Bering shelf, 6-8 ‰, is at odds with previous assumptions regarding the global ocean's N isotope budget.

  20. Mineralogical, geochemical and isotopic characterization of authigenic carbonates from the methane-bearing sediments of the Bering Sea continental margin (IODP Expedition 323, Sites U1343-U1345)

    NASA Astrophysics Data System (ADS)

    Pierre, C.; Blanc-Valleron, M.-M.; Caquineau, S.; März, C.; Ravelo, A. C.; Takahashi, K.; Alvarez Zarikian, C.

    2016-03-01

    During Expedition 323 of the Integrated Ocean Drilling Program to the Bering Sea (July 5-September 4, 2009), three sites were drilled along the Bering Sea northeastern continental margin [U1343 down to 745 meters below sea floor (mbsf), U1344 (745 mbsf), U1345 (150 mbsf)]. Diagenetic carbonates are present at all sites within the clayey, diatom-rich oozes of the Bering Sea, where pore waters are also characterized by extremely high methane concentrations. We here present mineralogical, elemental and isotopic data obtained from the authigenic carbonate-rich intercalations within the clay-rich Pleistocene sediments deposited along the Bering Sea continental margin. The mineralogy of the authigenic carbonates is generally represented by composite mixtures of very small crystals of magnesian calcite, dolomite, and iron-rich carbonates, with the latter phases occurring below 260 mbsf at Site U1343, below 200 mbsf at Site U1344, and below 130 mbsf at Site U1345. Element geochemistry shows that Ca, Mg, Fe, Ba, Mn, Sr and U are enriched in the carbonate-rich intercalations relative to the background sediments due to their incorporation into the carbonates and into other authigenic phases (e.g., barite and pyrite). The oxygen and carbon isotopic compositions of the authigenic carbonate minerals show that they were sequentially precipitated from pore waters at different temperatures (i.e., different burial depths) and with different isotopic compositions of dissolved inorganic carbon (DIC). The authigenic Mg-calcite precipitated early during diagenesis and shallow burial from a 13C-depleted DIC pool, whereas dolomite and Fe-rich carbonates formed during later diagenesis and deeper burial from a 13C-enriched DIC pool. These authigenic carbonate occurrences are interpreted as resulting from microbial sulfate reduction combined with anaerobic oxidation of methane, and methanogenesis that was intimately linked to the alteration of silicates, especially iron-rich clay minerals.

  1. Seismic Velocity and Thickness of Sediments Beneath the Aleutian Basin, Bering Sea

    NASA Astrophysics Data System (ADS)

    Scheirer, D. S.; Barth, G. A.; Sliter, R. W.; Hart, P. E.; Childs, J. R.

    2014-12-01

    The thickness and seismic velocity structure of sediments of the Aleutian Basin were mapped during a 2011 multichannel seismic (MCS) cruise of the R/V Langseth. Combined with legacy MCS, sonobuoy, and scientific drilling data, the Langseth observations allowed us to study the history of sedimentation in this area. Semblance velocity analyses from common-depth-point gathers of the 8-km-long streamer data were conducted at-sea every 6.25 km. Post-cruise, these semblance analyses were refined and supplemented with new analyses where significant basement topography is present. The flat-lying nature of both the seafloor and the within-sediment reflectors allowed determination of interval velocity and thickness values with high precision using the Dix equation. Two prominent bottom-simulating reflections (BSRs) are common within the sediment column: a shallower one inferred to represent the base of gas hydrate stability, and a deeper one inferred to represent the diagenetic transformation from opal-A to opal-CT. This latter transition was reached by the one deep hole (Site 190, DSDP Leg19) drilled into the Aleutian Basin, where the lithologic contrast prevented further penetration. The gas hydrate BSR is associated with subvertical velocity-amplitude anomalies, and the opal A/CT transition is associated with a large decrease in reflector amplitudes beneath it, indicating the decrease in acoustic impedance contrasts associated with diagenetic dewatering. Seismic interval velocities range from 1600 m/sec at the top of the sediment column to 2800-3500 m/sec at its base. The largest step in interval velocity occurs at the opal A/CT transition. Interval velocities are laterally continuous over many tens of kilometers, and this continuity allows the generation of seismic travel-time vs. sediment thickness relationships across the basin. A second-degree polynomial relationship between time and thickness, developed by regression of all of the semblance velocity analyses from the

  2. Geotectonics of the Bering Sea area, Alaska

    SciTech Connect

    Desautels, D.A.

    1985-04-01

    Plate tectonic interactions in the Bering Sea area have played a major role in its structural and geological history since Paleozoic time. The geotectonic style of different areas is similar due to the widespread influence of plate motions. Three major structural and depositional belts have been identified linking the Siberian area to Alaska across the Bering Sea. The northern belt, the Verkhoyansk-Chukotsk-Seward-Brooks, consists of early Mesozoic miogeosynclinal sediments. The middle belt, the Okhotsk-Chukotsk-Yukon-Kovyukuk, consists of a Mesozoic magmatic arc and numerous accreted allochthonous terranes. These features were formed as a result of convergence/subduction of a southern oceanic plate. The southern belt, the Koryak-Anadyr-Peninsular, consists of terranes accreted during Cretaceous time and forms the southern limit of Mesozoic subduction. During Late Cretaceous to early Tertiary time, rifting in the Atlantic caused these belts to be oroclinally bent southward and resulted in a shift of the Mesozoic subduction zone to a more southerly location. During formation of the oroclinal fold, subduction along the Bering Shelf margin changed from direct to oblique subduction, then to transform motion. Major movement along this margin ceased as the current Aleutian Island arc system began to form. Late Cretaceous to early Tertiary structures with the Koryak-Anadyr-Peninsular area are potentially important for petroleum exploration because they could have formed concurrently with source and reservoir facies.

  3. Geochemistry of sedimentary organic carbon in the shelf sediments from the Bering Sea: multiple proxy and implication for the sea ice change for the past century

    NASA Astrophysics Data System (ADS)

    Hu, Limin; Shi, Xuefa; Liu, Yanguang

    2016-04-01

    Based on the two multi-core sediment samples (BL16 and BL10) taken from the Fifth Chinese National Arctic Expedition cruise, the geochemical characteristics and sequestration of sedimentary total organic carbon (TOC) over the past century in the western Bering Sea were discussed, and the results showed that there existed a stable depositional regime in the study area according to the vertical distribution of the 210Pb profiles and its relationship with the core depth, thus, the past seventy years sedimentary record could be established in the two short sediment cores, respectively. As in the core BL16, there existed a good correlation between the TOC and total nitrogen (TN) as well as the grain size profiles, suggesting a consistent provenance for the sedimentary organic components and a dominant control of sediment grain size towards the OM burial; on the other hand, the core BL10 from the upper slope was more composed of relatively coarser sediments with a poor relation between the TOC and TN, which may caused by the complex depositional regime, various OM input and microorganism origin. A clear shift among the TOC and CaCO3 abundance in the upper sections (about twenty years ago) were observed in both two cores, which could be impacted by the recent regional warming in the arctic area and ocean acidification. The sedimentary TOC sequestration in the two cores were estimated as 3400 mmol C m-2/a and 1500 mmol C m-2/a, respectively, then after the examination of the preservation of sedimentary TOC and with a regional comparison for the TOC sink fluxes, the relatively higher sequestration of TOC in the study area could be constrained by the higher marine productivity, quick POC export from the upper water column, effective metabolic processing and higher sedimentation rates within the seabed.

  4. Release of Methane from Bering Sea Sediments During the Last Glacial Period

    SciTech Connect

    Mea Cook; Lloyd Keigwin

    2007-11-30

    Several lines of evidence suggest that during times of elevated methane flux the sulfate-methane transition zone (SMTZ) was positioned near the sediment-water interface. We studied two cores (from 700 m and 1457 m water depth) from the Umnak Plateau region. Anomalously low d13C and high d18O in benthic and planktonic foraminifera in these cores are the consequence of diagenetic overgrowths of authigenic carbonates. There are multiple layers of authigenic-carbonate-rich sediment in these cores, and the stable isotope compositions of the carbonates are consistent with those formed during anaerobic oxidation of methane (AOM). The carbonate-rich layers are associated with biomarkers produced by methane-oxidizing archaea, archaeol and glyceryl dibiphytanyl glyceryl tetraether (GDGT). The d13C of the archaeol and certain GDGTs are isotopically depleted. These carbonate- and AOM-biomarker-rich layers were emplaced in the SMTZ during episodes when there was a high flux of methane or methane-rich fluids upward in the sediment column. The sediment methane in the Umnak Plateau region appears to have been very dynamic during the glacial period, and interacted with the ocean-atmosphere system at millennial time scales. The upper-most carbonate-rich layers are in radiocarbon-dated sediment deposited during interstitials 2 and 3, 28-20 ka, and may be associated with the climate warming during this time.

  5. Geotectonic evolution of Bering Sea area, Alaska

    SciTech Connect

    Desautels, D.A.

    1985-02-01

    The geologic, structural, and tectonic history of the Bering Sea area since Paleozoic time is best viewed in terms of major plate-tectonic interactions. The geotectonic style of disparate areas is apparently related to the nature of plate motion at the time of tectonic imprint. Three major structural belts that have existed since the Mesozoic can be traced from the Siberian sector across the Bering Sea and into Alaska. The northern belt, the Verkhoyansk-Chukotsk-Seward-Brooks, consists of miogeosynclincal sediments that were deposited beginning in earliest Mesozoic time. The middle belt, the Okhotsk-Chukotsk-Yukon-Koyukuk, consists of a Mesozoic magmatic arc and numerous allochthonous terranes, formed due to the convergence-subduction of a southern oceanic plate. The southern belt, the Koryak-Anadyr-Peninsular, consists of terranes accreted during Cretaceous time and forms the southern limit of Mesozoic subduction. During Late Cretaceous to early Tertiary time, these belts were oroclinically bent southward by an east-west compressional event, causing the subduction zone to shift to a more southerly location, thus forming the current Aleutian Island arc system, behind which the fragments of 2 Cretaceous oceanic plates were trapped. These oceanic plate fragments may consist of an Early Cretaceous plate and a portion of the Kula plate(.), which carried a northward-migrating arc system. The hypothesized Early Cretaceous plate may have had a counterpart separated by a spreading ridge, both of which have been subducted beneath the Beringian margin.

  6. Pollen evidence for late pleistocene bering land bridge environments from Norton Sound, Northeastern Bering Sea, Alaska

    USGS Publications Warehouse

    Ager, T.A.; Phillips, R.L.

    2008-01-01

    After more than half a century of paleoenvironmental investigations, disagreements persist as to the nature of vegetation type and climate of the Bering land bridge (BLB) during the late Wisconsin (Sartan) glacial interval. Few data exist from sites on the former land bridge, now submerged under the Bering and Chukchi Seas. Two hypotheses have emerged during the past decade. The first, based on pollen data from Bering Sea islands and adjacent mainlands of western Alaska and Northeast Siberia, represents the likely predominant vegetation on the Bering land bridge during full-glacial conditions: graminoid-herb-willow tundra vegetation associated with cold, dry winters and cool, dry summer climate. The second hypothesis suggests that dwarf birch-shrub-herb tundra formed a broad belt across the BLB, and that mesic vegetation was associated with cold, snowier winters and moist, cool summers. As a step towards resolving this controversy, a sediment core from Norton Sound, northeastern Bering Sea was radiocarbon dated and analyzed for pollen content. Two pollen zones were identified. The older, bracketed by radiocarbon ages of 29,500 and 11,515 14C yr BP, contains pollen assemblages composed of grass, sedge, wormwood, willow, and a variety of herb (forb) taxa. These assemblages are interpreted to represent graminoid-herb-willow tundra vegetation that developed under an arid, cool climate regime. The younger pollen zone sediments were deposited about 11,515 14C yr BP, when rising sea level had begun to flood the BLB. This younger pollen zone contains pollen of birch, willow, heaths, aquatic plants, and spores of sphagnum moss. This is interpreted to represent a Lateglacial dwarf birch-heath-willow-herb tundra vegetation, likely associated with a wetter climate with deeper winter snows, and moist, cool summers. This record supports the first hypothesis, that graminoid-herb-willow tundra vegetation extended into the lowlands of the BLB during full glacial conditions of the

  7. Color Difference in Bering Sea Phytoplankton Blooms

    NASA Technical Reports Server (NTRS)

    2002-01-01

    There is considerable color variation in the phytoplankton blooms in the Bering Sea -- from the aquamarine west of Nunivak Island to the almost reddish patch west of St. Matthew Island to the green eddy astride the International dateline at 60 North latitude and 178 East longitude. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  8. Introduction to Pliocene-Pleistocene paleoceanography of the Bering Sea

    NASA Astrophysics Data System (ADS)

    Takahashi, Kozo; Ravelo, A. Christina; Okazaki, Yusuke

    2016-03-01

    High resolution paleoceanography of the Pliocene-Pleistocene is important in understanding climate forcing mechanisms and associated environmental changes during this major transition from global warmth to the Ice Ages. This is particularly true in high latitude marginal seas such as the Bering Sea. The Bering Sea has been very sensitive to changes in global climate during interglacial and glacial, or Milankovitch, time scales. This is due to significant changes in water circulation, land-ocean interaction, and sea-ice formation. With the aim to reveal the climate and oceanographic history of the Bering Sea over the past 5 My, IODP Expedition 323 cored a total of 5741 m of sediment (97.4% recovery) at seven sites in 2009 on D/V JOIDES Resolution covering three regions: the Umnak Plateau, the Bowers Ridge, and the Bering Slope. The water depths of the drill sites range from 818 m to 3174 m, allowing for the characterization of past vertical water mass distribution including changes in the oxygen minimum zone. The four deepest holes range from 600 m to 745 m below the seafloor, and resulted in the recovery of long sediment sequences ranging from 1.9 My to 5 My in age. Following the expedition, two sampling parties at Kochi Core Center (for acquisition of ca. 58,000 subsamples) and two scientific meetings were conducted in order to proceed with the analyses of sediment core samples and discussions. Here, pertinent results, primarily from IODP Expedition 323, are consolidated as a single special volume of Deep-Sea Research Part II Topical Studies in Oceanography.

  9. Modern modes of provenance and dispersal of terrigenous sediments in the North Pacific and Bering Sea: implications and perspectives for palaeoenvironmental reconstructions

    NASA Astrophysics Data System (ADS)

    Wang, Rong; Biskaborn, Boris K.; Ramisch, Arne; Ren, Jian; Zhang, Yongzhan; Gersonde, Rainer; Diekmann, Bernhard

    2016-08-01

    During expedition 202 aboard the RV Sonne in 2009, 39 seafloor surface sediment sites were sampled over a wide sector of the North Pacific and adjoining Bering Sea. The data served to infer land-ocean linkages of terrigenous sediment supply in terms of major sources and modes of sediment transport within an over-regional context. This is based on an integrated approach dealing with grain-size analysis, bulk mineralogy and clay mineralogy in combination with statistical data evaluation (end-member modelling of grain-size data, fuzzy cluster analysis of mineralogical data). The findings on clay mineralogy served to update those of earlier work extracted from the literature. Today, two processes of terrigenous sediment supply prevail in the study area: far-distance aeolian sediment supply to the pelagic North Pacific, and hemipelagic sediment dispersal from nearby land sources via ocean currents along the continental margins and island arcs. Aeolian particles show the finest grain sizes (clay and fine silt), whereas hemipelagic sediments have high abundances of coarse silt. Exposed sites on seamounts and the continental slope are partly swept by strong currents, leading to residual enrichment of fine sand. Four sediment sources can be distinguished on the basis of distinct index minerals revealed by statistical data analysis: dust plumes from central Asia (quartz, illite), altered materials from the volcanic regions of Kamchatka and the Aleutian Arc (smectite), detritus from the Alaskan Cordillera (chlorite, hornblende), and fluvial detritus from far-eastern Siberia and the Alaska mainland (quartz, feldspar, illite). These findings confirm those of former studies but considerably expand the geographic range of this suite of proxies as far south as 39°N in the open North Pacific. The present integrated methodological approach proved useful in identifying the major modern processes of terrigenous sediment supply to the study region. This aspect deserves attention in

  10. Sediment classification using neural networks: An example from the site-U1344A of IODP Expedition 323 in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Ojha, Maheswar; Maiti, Saumen

    2016-03-01

    A novel approach based on the concept of Bayesian neural network (BNN) has been implemented for classifying sediment boundaries using downhole log data obtained during Integrated Ocean Drilling Program (IODP) Expedition 323 in the Bering Sea slope region. The Bayesian framework in conjunction with Markov Chain Monte Carlo (MCMC)/hybrid Monte Carlo (HMC) learning paradigm has been applied to constrain the lithology boundaries using density, density porosity, gamma ray, sonic P-wave velocity and electrical resistivity at the Hole U1344A. We have demonstrated the effectiveness of our supervised classification methodology by comparing our findings with a conventional neural network and a Bayesian neural network optimized by scaled conjugate gradient method (SCG), and tested the robustness of the algorithm in the presence of red noise in the data. The Bayesian results based on the HMC algorithm (BNN.HMC) resolve detailed finer structures at certain depths in addition to main lithology such as silty clay, diatom clayey silt and sandy silt. Our method also recovers the lithology information from a depth ranging between 615 and 655 m Wireline log Matched depth below Sea Floor of no core recovery zone. Our analyses demonstrate that the BNN based approach renders robust means for the classification of complex lithology successions at the Hole U1344A, which could be very useful for other studies and understanding the oceanic crustal inhomogeneity and structural discontinuities.

  11. New Coccolithophore Bloom in Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    For the fourth year in a row it appears as if there is a bloom of coccolithophores-marine single-celled plants with calcite scales-in the Bering Sea off the coast of Alaska. Similar blooms were rare before 1997, but they have appeared every year since then. Scientists believe the coccolithophore blooms are the result of changing wind patterns in the region. Weaker than normal winds fail to mix the water of the Bering Sea, resulting in the growth of coccolithophores instead of other types of phytoplankton. Seabird populations have also been changing as a result of this climate change. The Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, saw the coccolith-brightened waters of the Bering Sea in 1997, 1998, and 1999. The waters have looked fairly bright again this winter and spring, as seen in this SeaWiFS image acquired April 29, 2000. But scientists are unsure whether this year's phenomenon is caused by living coccolithophorids, re-suspended coccoliths, or something else. Like all phytoplankton, coccolithophores contain chlorophyll and have the tendency to multiply rapidly near the surface. Yet, in large numbers, coccolithophores periodically shed their tiny scales, called 'coccoliths,' by the bucketful into the surrounding waters. The calcium-rich coccoliths turn the normally dark water a bright, milky aquamarine, making coccolithophore blooms easy to spot in satellite imagery. The edge of the whitish cloud in the water seen in this image is roughly 50 kilometers off the West Coast of Alaska. For more information see: SeaWiFS home page Changing Currents Color the Bering Sea a New Shade of Blue Image courtesy SeaWiFS project

  12. Marine Isotope Stage (MIS) 5 on the Umnak Plateau, Bering Sea (IODP Site U1339): Using diatom taxonomy, grain size and nitrogen isotopic composition of marine sediments as proxies for primary productivity and sea ice extent

    NASA Astrophysics Data System (ADS)

    Vaughn, D.; Caissie, B.

    2014-12-01

    The current rapid reduction of sea ice in the Arctic has motivated numerous studies to look at how sea ice declines during times of climate warming and its impact on marine ecosystems. Marine Isotope Stage (MIS) 5 is the last interglacial prior to the Holocene and has been characterized as having higher summer air temperatures and higher sea level compared to today. However, there is a scarcity of data for sea ice extent during MIS 5. This presents an opportunity to reconstruct sea ice during a previous warming that may be used as an analogue for future change. We aim to provide insight into how sea ice changed throughout MIS 5 and how this change impacted primary productivity at the Umnak Plateau in the southeastern Bering Sea. This region is not currently covered by sea ice at all; however, low-resolution work reveals that sea ice did reach the study area during glacial intervals. This study uses high-resolution (500 year) bulk geochemistry, diatom taxonomy, and grain size analysis of marine sediments from the Umnak Plateau as proxies for primary production and sea ice conditions during MIS 5. Nitrogen isotopic measurements of marine sediments are a valuable recorder of nitrate utilization by primary producers. Diatom taxonomy gives corresponding ecological affinities, which are relatable to sea ice coverage, productivity, and sea surface temperatures. Grain size analyses from previous studies have shown clay- and silt-sized biogenic content with well-preserved diatom valves to be associated with interglacials and larger silt to sand-size siliclastic particles with fragmented diatom valves to be associated with glacials. In this study, the silt fraction appears to be constant while the clay fraction follows the oxygen isotope record from Lisiecki and Raymo, 2005, increasing during glacial intervals and stadials. This apparent contradiction with earlier work warrants further investigation.

  13. Nitrification-coupled denitrification in sediment of the eastern Bering Sea shelf leads to 15N-enrichment of fixed N in shelf waters

    NASA Astrophysics Data System (ADS)

    Granger, J.; Prokopenko, M. G.; Mordy, C. W.; Sigman, D. M.

    2010-12-01

    We present a survey of the N and O isotope ratios of NO3- (15N/14N and 18O/16O) on the eastern Bering Sea shelf. We participated in two consecutive field campaigns in April 2007 and April 2008, for which we evaluate the N isotope budget of the ice-covered shelf prior to the onset of significant phytoplankton spring growth. The 15N/14N of NO3- was progressively 15N-deplete inshore and northward, and inversely correlated with incident [NH4+], whereas the 15N/14N of [NH4+] was 15N-enriched relative to incident NO3-. This is best explained by N isotope discrimination during partial nitrification of the NH4+ released from sediment, which indicates that remineralization of organic material in sediment contributes appreciably to replenishment of water column NO3- throughout the winter months. These observations further invoke a mechanism of fixed N loss from sediment where 15N-deplete NO3- generated from nitrification in oxygenated surface sediment fuels underlying denitrification, leading to the net loss of 15N-deplete N as N2. A parallel efflux of 15N-enriched NH4+ from sediment should lead to a net 15N-enrichment of fixed N in the water column. This mechanism is corroborated by measurements of the 15N/14N of surface sediment on the shelf, which were progressively 15N-enriched with hydrographic distance from shelf edge, in proportion to the extent of N loss to sedimentary denitrification recorded in the overlying water column. Moreover, the fraction of newly nitrified nitrate on the shelf, evidenced by a decrease in the 18O/16O, correlated strongly with the extent of fixed N loss to sedimentary denitrification, further implicating nitrification-coupled denitrification as the predominant mechanism of fixed N loss on the shelf. The isotope effect of nitrification-couple denitrification on the shelf, derived from the 15N/14N of surface sediment relative the water column N loss, is surprisingly elevated, ranging between 6.2‰ and 8.1‰. The sizeable amplitude of the

  14. 76 FR 68658 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-07

    ... Zone Off Alaska; Pacific Ocean Perch in the Bering Sea Subarea of the Bering Sea and Aleutian Islands... is opening directed fishing for Pacific ocean perch in the Bering Sea subarea of the Bering Sea and... Pacific ocean perch specified for the Bering Sea subarea of the Bering Sea and Aleutian Islands...

  15. Paleoceanographic conditions in the western Bering Sea as a response to global sea level changes and remote climatic signals during the last 180 kyr

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Gulev, S. K.

    2016-06-01

    We present results from the sediment core SO201-2-85KL retrieved from the western Bering Sea that recovered the past 180 000 years. For the first time, the intense dissolution of calcareous microfossils has been established when the Bering Strait was open during the glacioeustatic sea level rise. Possible mechanisms of climatic teleconnections between remote regions are considered.

  16. Influence of the Yukon River on the Bering Sea

    NASA Technical Reports Server (NTRS)

    Dean, Kenneson G.; Mcroy, C. Peter

    1988-01-01

    Physical and biological oceanography of the northern Bering Sea including the influence of the Yukon River were studied. Satellite data acquired by the Advanced Very High Resolution Radiometer (AVHRR), the LANDSAT Multispectral Scanner (MSS) and the Thematic Mapper (TM) sensor were used to detect sea surface temperatures and suspended sediments. Shipboard measurements of temperature, salinity and nutrients were acquired through the Inner Shelf Transfer and Recycling (ISHTAR) project and were compared to digitally enhanced and historical satellite images. The satellite data reveal north-flowing, warm water along the Alaskan coast that is highly turbid with complex patterns of surface circulation near the Yukon River delta. To the west near the Soviet Union, cold water, derived from an upwelling, mixes with shelf water and also flows north. The cold and warm water coincide with the Anadyr, Bering Shelf and Alaskan coastal water masses. Generally, warm Alaskan coastal water forms near the coast and extends offshore as the summer progresses. Turbid water discharged by the Yukon River progresses in the same fashion but extends northward across the entrance to Norton Sound, attaining its maximum surface extent in October. The Anadyr water flows northward and around St. Lawrence Island, but its extent is highly variable and depends upon mesoscale pressure fields in the Arctic Ocean and the Bering Sea.

  17. Repeated occurrences of methanogenic zones, diagenetic dolomite formation and linked silicate alteration in southern Bering Sea sediments (Bowers Ridge, IODP Exp. 323 Site U1341)

    NASA Astrophysics Data System (ADS)

    Wehrmann, L. M.; Ockert, C.; Mix, A. C.; Gussone, N.; Teichert, B. M. A.; Meister, P.

    2016-03-01

    Diagenetic precipitates, such as dolomite, and the chemistry of residual deeply buried porewater often represent the only traces of past biogeochemical activity in marine sediments. A 600 m thick sedimentary section, recently drilled at Integrated Ocean Drilling Program (IODP) Site U1341 on Bowers Ridge (southern Bering Sea), provides insight into such a 4.3 Ma old paleo-diagenetic archive. Hard-lithified calcite-dolomite layers, and laminae of disseminated carbonate, were recovered in diatom-rich sediments over a depth range of 400 m. Carbon isotope values of the diagenetic carbonates between -16.6 and -14.4‰ (VPDB) and strontium isotope ratios of dolomites close to past seawater values suggest carbonate precipitation induced by the production of dissolved inorganic carbon (DIC) during elevated rates of organic carbon mineralization, primarily via sulfate reduction, at shallow sediment depth below the paleo-seafloor. Diagenetic carbonates at 280-440 m below seafloor were likely also produced by the intermittent onset of sulfate reduction coupled to the anaerobic oxidation of methane (AOM) at sulfate-methane transition zones (SMTZ). These microbially mediated processes do not occur in the sediment at this site at present but were likely connected to the presence of a methanogenic zone at 2.58-2.51 Ma. A minimum in sulfate concentrations in modern porewaters and low sedimentary Ba/Al ratios resulting from former sulfate depletion are reminiscent of the presence of this large methanogenic zone. The minimum in sulfate concentrations is reflected in a minimum in magnesium concentrations, less radiogenic strontium and isotopically light calcium in the porewater. It is proposed that magnesium was removed from the porewater during carbonate precipitation and volcanic ash alteration which occurred in the former methanogenic zone and also released strontium with a less radiogenic isotope ratio and isotopically light calcium into the porewater. The isotopic composition of

  18. Pleistocene Deep Sea ostracods from the Bering Sea (IODP expedition 323)

    NASA Astrophysics Data System (ADS)

    Alvarez Zarikian, Carlos A.

    2016-03-01

    The study presents the first Pleistocene (0-1.9 Ma) record of Deep Sea ostracods from the Bering Sea, derived primarily from Integrated Ocean Drilling Program Expedition 323, Site U1344 (59°3.0‧N, 179°12.2‧W, 3171 m of water depth). Deep Sea ostracod abundances in the Bering Sea sediments are some of the lowest that have been recorded in bathyal and abyssal marine environments (<1 specimen per sediment gram). In comparison, benthic foraminifera are several orders of magnitude more abundant in the same samples. The humble ostracod assemblage at Site U1344 is predominantly composed of deep water species Krithe sawanensis, Fallacihowella sp. A, Cytheropteron spp., Eucytherura sp., Argilloecia toyamaensis, and Bradleya mesembrina. Less abundant taxa include Munseyella melzeri, Munseyella ristveti, Cluthia sp., Robertsonites hanaii, and Microcythere mediostriata. Some of these taxa (e.g. Fallacihowella sp. A, Bradleya mesembrina, Microcythere mediostriata) are reported for the first time in the North Pacific. The predominance of the genera Krithe, Fallacihowella, Cytheropteron and Argilloecia indicates cold, ventilated bottom waters. The deep Bering Sea ostracod assemblage shares many common and closely related species with continental slope faunas from the Gulf of Alaska, the Okhotsk Sea, the Arctic Ocean, and even the subpolar North Atlantic. A few continental shelf ostracods, such as species of Munseyella and Robertsonites, are present at Sites U1344 and U1343, in the northern slope of the Aleutian Basin. The presence of shallow water ostracods at the Bering Sea slope sites is possibly explained by sea ice rafting. Exceptionally low ostracod abundance in the U1344 record did not permit evaluating links between ostracod faunas and paleoceanographic conditions; however, an increase in ostracod occurrences throughout the middle Pleistocene at Site U1344 appears to correlate with general sea ice expansion in the Bering Sea. High primary surface productivity, high

  19. How Does Climate Change Affect the Bering Sea Ecosystem?

    NASA Astrophysics Data System (ADS)

    Sigler, Michael F.; Harvey, H. Rodger; Ashjian, Carin J.; Lomas, Michael W.; Napp, Jeffrey M.; Stabeno, Phyllis J.; Van Pelt, Thomas I.

    2010-11-01

    The Bering Sea is one of the most productive marine ecosystems in the world, sustaining nearly half of U.S. annual commercial fish catches and providing food and cultural value to thousands of coastal and island residents. Fish and crab are abundant in the Bering Sea; whales, seals, and seabirds migrate there every year. In winter, the topography, latitude, atmosphere, and ocean circulation combine to produce a sea ice advance in the Bering Sea unmatched elsewhere in the Northern Hemisphere, and in spring the retreating ice; longer daylight hours; and nutrient-rich, deep-ocean waters forced up onto the broad continental shelf result in intense marine productivity (Figure 1). This seasonal ice cover is a major driver of Bering Sea ecology, making this ecosystem particularly sensitive to changes in climate. Predicted changes in ice cover in the coming decades have intensified concern about the future of this economically and culturally important region. In response, the North Pacific Research Board (NPRB) and the U.S. National Science Foundation (NSF) entered into a partnership in 2007 to support the Bering Sea Project, a comprehensive $52 million investigation to understand how climate change is affecting the Bering Sea ecosystem, ranging from lower trophic levels (e.g., plankton) to fish, seabirds, marine mammals, and, ultimately, humans. The project integrates two research programs, the NSF Bering Ecosystem Study (BEST) and the NPRB Bering Sea Integrated Ecosystem Research Program (BSIERP), with substantial in-kind contributions from the U.S. National Oceanic and Atmospheric Administration (NOAA) and the U.S. Fish and Wildlife Service.

  20. 50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    .... Those waters inside the Russian 200 mile limit as described in the current editions of NOAA chart INT 813 Bering Sea (Southern Part) and NOAA chart INT 814 Bering Sea (Northern Part). 400 Chukchi Sea... edition of NOAA chart INT 814 Bering Sea (Northern Part). 508 South of 58°00′ N between the...

  1. 50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    .... Those waters inside the Russian 200 mile limit as described in the current editions of NOAA chart INT 813 Bering Sea (Southern Part) and NOAA chart INT 814 Bering Sea (Northern Part). 400 Chukchi Sea... edition of NOAA chart INT 814 Bering Sea (Northern Part). 508 South of 58°00′ N between the...

  2. 50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    .... Those waters inside the Russian 200 mile limit as described in the current editions of NOAA chart INT 813 Bering Sea (Southern Part) and NOAA chart INT 814 Bering Sea (Northern Part). 400 Chukchi Sea... edition of NOAA chart INT 814 Bering Sea (Northern Part). 508 South of 58°00′ N between the...

  3. 50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    .... Those waters inside the Russian 200 mile limit as described in the current editions of NOAA chart INT 813 Bering Sea (Southern Part) and NOAA chart INT 814 Bering Sea (Northern Part). 400 Chukchi Sea... edition of NOAA chart INT 814 Bering Sea (Northern Part). 508 South of 58°00′ N between the...

  4. 50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    .... Those waters inside the Russian 200 mile limit as described in the current editions of NOAA chart INT 813 Bering Sea (Southern Part) and NOAA chart INT 814 Bering Sea (Northern Part). 400 Chukchi Sea... edition of NOAA chart INT 814 Bering Sea (Northern Part). 508 South of 58°00′ N between the...

  5. Influence of the Yukon River on the Bering Sea

    NASA Technical Reports Server (NTRS)

    Dean, K.; Mcroy, C. P.

    1986-01-01

    The purpose is to use satellite data to study relationships between discharge of the Yukon River to currents and biologic productivity in the northern Bering Sea. Amended specific objectives are: to develop thermal, sediment and chlorophyll surface maps using thematic mapping (TM) data of the discharge of the Yukon River and the Alaska Coastal Current during the ice free season; to develop a historical model of the distribution of the Yukon River discharge and the Alaska Coastal Current using LANDSAT multispectral scanner (MMS) and NOAA satellite imagery; and to use high resolution TM data to define the surface dynamics of the front between the Alaska Coastal Current and the Bering Shelf/Anadyr Current. LANDSAT MSS and TM, and Advanced Very High Resolution Radiometer (AVHRR) data were recorded during the 1985 ice-free period. The satellite data coincided with shipboard measurements acquired by Inner Self Transfer and Recycling scientists. Circumstances were such, that on July 5 and July 22, all three sensors recorded data that has been registered to a common map projection and map base, then contrast stretched, color composited, and density sliced.

  6. GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain

    SciTech Connect

    Carlson, P.R.; Cooper, A.K.; Gardner, J.V.; Karl, H.A.; Marlow, M.S.; Stevenson, A.J.; Huggett, Q.; Kenyon, N.; Parson, L.

    1987-05-01

    During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slides and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.

  7. 76 FR 3089 - Proposed Information Collection; Comment Request; Alaska Region Bering Sea & Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-19

    ... Region Bering Sea & Aleutian Islands Crab Permits AGENCY: National Oceanic and Atmospheric Administration... of a currently approved collection. The Crab Rationalization Program allocates Bering Sea and Aleutian Islands (BSAI) crab resources among harvesters, processors, and coastal communities through...

  8. 76 FR 3090 - Proposed Information Collection; Comment Request; Alaska Region; Bering Sea and Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-19

    ... Region; Bering Sea and Aleutian Islands Crab Arbitration AGENCY: National Oceanic and Atmospheric... extension of a currently approved collection. The Crab Rationalization Program allocates Bering Sea and Aleutian Islands (BSAI) crab resources among harvesters, processors, and coastal communities through...

  9. Late summer zoogeography of the northern Bering and Chukchi seas

    NASA Astrophysics Data System (ADS)

    Sigler, Michael F.; Mueter, Franz J.; Bluhm, Bodil A.; Busby, Morgan S.; Cokelet, Edward D.; Danielson, Seth L.; Robertis, Alex De; Eisner, Lisa B.; Farley, Edward V.; Iken, Katrin; Kuletz, Kathy J.; Lauth, Robert R.; Logerwell, Elizabeth A.; Pinchuk, Alexei I.

    2017-01-01

    Ocean currents, water masses, and seasonal sea ice formation contribute to determining relationships among the biota of the Bering and Chukchi seas. The Bering Sea communicates with the Chukchi Sea via northward advection of water, nutrients, organic matter, and plankton through Bering Strait. We used data from concurrent surveys of zooplankton, pelagic fishes and jellyfish, epibenthic fishes and invertebrates, and seabirds to identify faunal distribution patterns and environmental factors that are related to these faunal distributions within the US portions of the Chukchi Sea shelf and Bering Sea shelf north of Nunivak Island. Regional differences in late summer (August-September) distributions of biota largely reflected the underlying hydrography. Depth, temperature, salinity, stratification, and chlorophyll a, but less so sediment-related or nutrient-related factors, were related to the distributions of the assemblages (zooplankton: depth, salinity, stratification; pelagic fishes and jellyfish: depth, stratification, chlorophyll a; epibenthic fishes and invertebrates: depth, temperature, salinity; seabirds: temperature, salinity, stratification). These six environmental factors that most influenced distributions of zooplankton, pelagic fishes/jellyfish, epibenthic fishes and invertebrate, and seabird assemblages likely can be simplified to three factors reflecting bottom depth, water mass, and their stratification and productivity (which are tightly linked in the study region). The assemblages were principally structured from nearshore to offshore and from south to north. The nearshore to offshore contrast usually was stronger in the south, where the enormous discharge of the Yukon River is more apparent and extends farther offshore, influencing zooplankton, pelagic fish/jellyfish, and seabird assemblages. Some assemblages overlapped spatially (e.g., seabird and zooplankton), indicating shared influential environmental factors or trophic linkages among

  10. Aerial Surveys of Endangered Whales in the Beaufort Sea, Chukchi Sea, and Northern Bering Sea.

    DTIC Science & Technology

    1981-06-01

    of Kivalina. The entire area from this point to the village of Wales was icebound. Figure 3 shows the typical ice conditions of the Bering Sea...area extending across the Bering Straits from Cape Prince of Wales to the north end of Little Diomede Island. Large concentrations of pan ice with a 7...ice conditions across the main area of sightings between Wales and Little Diomede Island throughout the survey effort. 8 !. I. I Beaufort Sea I.Brrow

  11. Anthropometric variation among Bering Sea natives.

    PubMed

    Justice, Anne; Rubicz, Rohina; Chittoor, Geetha; Jantz, Richard L; Crawford, M H

    2010-12-01

    Recent research indicates that anthropometrics can be used to study microevolutionary forces acting on humans. We examine the use of morphological traits in reconstructing the population history of Aleuts and Eskimos of the Bering Sea. From 1979 to 1981, W. S. Laughlin measured a sample of St. Lawrence Island Eskimos and Pribilof Island Aleuts. These samples included adult participants from St. George and St. Paul in the Pribilof Islands and from Gambell and Savoonga on St. Lawrence Island. The Relethford-Blangero method was used to examine the phylogenetic relationship between Aleuts and Eskimos. Anthropometric measurements for Native North Americans (measured by Boas and a team of trained anthropometrists in 1890-1904) and Native Mesoamericans (compiled from the literature for 1898-1952) were used for comparison. A principal components analysis of means for measurements and a neighbor-joining tree were constructed using Euclidean distances. All these tests revealed the same strong relationship among the focus populations. The R matrix from the Relethford-Blangero method clusters Aleuts and Eskimos separately and accounts for 97.3% of the variation in the data. Phenotypic variation within the population is minimal and therefore minimum F(ST) values are low. Genetic distances were compared to a Euclidean distance matrix of anthropometric measurements using a Mantel test and gave a high but not significant correlation. Our results provide evidence of a close phylogenetic relationship between Aleut and Eskimo populations in the Bering Sea. However, it is apparent that history has affected the relationship among the populations. Despite previous findings of higher European admixture in Gambell (based on blood group markers) than in Savoonga, Savoonga has greater within-group variation in anthropometric measurements. Anthropometrics reveal a close relationship between Gambell and St. Paul as a result of European admixture. The St. George population was the most

  12. The Northern Bering Sea: An Arctic Ecosystem in Change

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.

    2004-12-01

    Arctic systems can be rich and diverse habitats for marine life in spite of the extreme cold environment. Benthic faunal populations and associated biogeochemical cycling processes are influenced by sea-ice extent, seawater hydrography (nutrients, salinity, temperature, currents), and water column production. Benthic organisms on the Arctic shelves and margins are long-term integrators of overlying water column processes. Because these organisms have adapted to living at cold extremes, it is reasonable to expect that these communities will be among the most susceptible to climate warming. Recent observations show that Arctic sea ice in the North American Arctic is melting and retreating northward earlier in the season and the timing of these events can have dramatic impacts on the biological system. Changes in overlying primary production, pelagic-benthic coupling, and benthic production and community structure can have cascading effects to higher trophic levels, particularly benthic feeders such as walruses, gray whales, and diving seaducks. Recent indicators of contemporary Arctic change in the northern Bering Sea include seawater warming and reduction in ice extent that coincide with our time-series studies of benthic clam population declines in the shallow northern Bering shelf in the 1990's. In addition, declines in benthic amphipod populations have also likely influenced the movement of feeding gray whales to areas north of Bering Strait during this same time period. Finally a potential consequence of seawater warming and reduced ice extent in the northern Bering Sea could be the northward movement of bottom feeding fish currently in the southern Bering Sea that prey on benthic fauna. This would increase the feeding pressure on the benthic prey base and enhance competition for this food source for benthic-feeding marine mammals and seabirds. This presentation will outline recent biological changes observed in the northern Bering Sea ecosystem as documented in

  13. Bering Sea shifts toward an earlier spring transition

    NASA Astrophysics Data System (ADS)

    Stabeno, Phyllis J.; Overland, James E.

    Major changes have occurred in the northern high latitudes in the last two decades. These changes range from decreases in marine mammal populations to stratospheric cooling and permafrost warmings. Over Alaska and northwestern Canada, there is an earlier transition from winter to spring. Alaskan natives who live along the coast of the northern Bering Sea have noted warmer spring temperatures, thinner sea ice, and earlier melting of snow and ice. While winters over the northern Bering Sea are cold and dark, the long hours of daylight during spring and summer, coupled with high concentrations of nutrients, make this region among the most productive in the world. Change in timing of the transition between winter and spring is affecting the ecosystem, which in turn will impact the fishermen and natives who use the Bering Sea's living resources.

  14. Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean

    PubMed Central

    Horikawa, Keiji; Martin, Ellen E.; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

    2015-01-01

    Warming of high northern latitudes in the Pliocene (5.33–2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling. PMID:26119338

  15. Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean.

    PubMed

    Horikawa, Keiji; Martin, Ellen E; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

    2015-06-29

    Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling.

  16. 77 FR 65838 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-31

    ... Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea Subarea of the Bering Sea and Aleutian... directed fishing for Pacific ocean perch in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This action is necessary to fully use the 2012 total allowable catch of Pacific ocean...

  17. 75 FR 68726 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-09

    ... Zone Off Alaska; Pacific Ocean Perch in the Bering Sea Subarea of the Bering Sea and Aleutian Islands... directed fishing for Pacific ocean perch in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This action is necessary to fully use the 2010 total allowable catch of Pacific ocean...

  18. Influences of sea ice on eastern Bering Sea phytoplankton

    NASA Astrophysics Data System (ADS)

    Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui

    2015-03-01

    The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions: open water, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

  19. East Siberia and Bering Sea, Russia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On June 5, 2001 MODIS captured this true-color image of Eastern Siberia and the Bering Strait. To the right of the image is the western tip of Alaska's St. Lawrence Island. Credit: Jacques Descloitres, MODIS Land Rapid Response Team

  20. Assessment of gray whale feeding grounds and sea floor interaction in the northeastern Bering Sea

    USGS Publications Warehouse

    Nelson, C.H.; Johnson, K.R.; Barber, John H.

    1983-01-01

    A dense ampeliscid amphipod community in Chirikov Basin and around St. Lawrence Island in the northeastern Bering Sea has been outlined by summarizing biological studies, analyzing bioturbation in sediment samples, and examining sea floor photos and videotapes. The amphipod population is associated with a homogeneous, relict fine-grained sand body 0.10-1.5 m thick that is deposited during the marine transgression over the Bering land bridge 8,000-10,000 yr B.P. Modern current and water mass movements and perhaps whale feeding activity prevent modern deposition in this area. The distribution of the transgressive sand sheet, associated amphipod community and feeding gray whales mapped by aerial survey correlate closely with three types of sea-floor pits observed on high (500 kHz) and low (105 kHz) resolution side-scan sonar; they are attributed to gray whale feeding traces and their subsequent current scour modification. The fresh and modified feeding pits are present in 22,000 km2 of the basin and they cover a total of 2 to 18% of the sea floor in different areas of the feeding region. The smallest size class of pits approximates whale mouth gape size and is assumed to represent fresh whale feeding pits. Fresh feeding disturbance of the sea floor is estimated to average about 5.7% for a full feeding season. Combined with information that 34% of the measured benthic biomass is amphipod prey species, and calculating the number of gray whale feeding days in the Alaskan waters plus amount consumed per day, it can be estimated that Chirikov Basin, 2% of the feeding area, supplies a minimum of 5.3 to 7.1% of the gray whale's food resource in the Bering Sea and Arctic Ocean. If a maximum of 50% of the fresh feeding features are assumed to be missed because they parallel side-scan beam paths, then a maximum whale food resource of 14.2% is possible in northeastern Bering Sea. Because of side-scan techniques and possible higher amphipod biomass estimates, a reasonable minimum

  1. 75 FR 37371 - Fisheries of the Exclusive Economic Zone Off Alaska; Fisheries of the Bering Sea Subarea

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-29

    ... nonpelagic trawl gear to directed fish for flatfish in the Bering Sea subarea and would change the boundaries... boundaries of the Northern Bering Sea Research Area (NBSRA) to establish the Modified Gear Trawl Zone (MGTZ... match the southern ] boundary of Statistical Area 400 at the Bering Strait. Area 514 of the Bering...

  2. Distribution and abundance of decapod crustacean larvae in the southeastern Bering Sea with emphasis on commercial species. Final report

    SciTech Connect

    Armstrong, D.A.; Incze, L.S.; Wencker, D.L.; Armstrong, J.L.

    1981-01-01

    Contents include: Distribution and abundance of king crab larvae, Paralithodes camtschatica and P. platypus in the southeast Bering Sea; Distribution and abundance of the larvae of tanner crabs in the southeastern Bering Sea; Distribution and abundance of other brachyuran larvae in the southeastern Bering Sea with emphasis on Erimacrus isenbeckii; Distribution and abundance of shrimp larvae in the southeastern Bering Sea with emphasis on pandalid species; Distribution and abundance of hermit crabs (Paguridae) in the southeasternBering Sea; Possible oil impacts on decapod larbae in the southeastern Bering Sea with emphesis on the St. George Basin.

  3. Shallow geology of north Aleutian shelf area, Bering Sea, Alaska

    SciTech Connect

    Hoose, P.J.; Ashenfelter, K.H.

    1983-03-01

    In 1981, the geological hazards analysis group of the US Geological Survey's Conservation Division collected 4009 line-km (2491 line-mi) of high-resolution seismic reflection data in the south-central Bering Sea. The US Department of the Interior has tentatively selected this area for inclusion in Outer Continental Shelf Oil and Gas Lease Sale 92 scheduled to be held in 1985. This study was part of the surface and shallow subsurface geological investigation of the sale area. A bathymetric map constructed from these data reveals a prominent, 20-m (33 ft) high, gentle scarp which trends obliquely across the survey area. Several linear moraine deposits, and several sag depressions related to the presence of near-surface faults were also found in the area. A Holocene isopach map reveals that sediment distribution is current-controlled. Contemporary current-related features consist of ripple marks, sediment waves, and scour zones. These features generally occur within 60 km (37 mi) of the shore and in water depths of less than 70 m (230 ft). Although current flow generally parallels the shore, side-scan sonographs indicate that the current direction which produced these features is strongly influenced by small and intermediate scale bathymetric features. Faults are present in the southwestern portion of the survey area where they occur in a 30 km (19 mi) wide, east-west trending zone. Within it, faults trend approximately east-west and sense of movement is exclusively normal. There are also several examples of growth faults. Acoustic anomalies, which may represent gas, are present throughout much of the survey area and occur at two different relatively shallow depths.

  4. Environmental Magnetic Signature Of Late Quaternary Climate and Paleoceanography in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Platzman, E. S.; Lund, S.; Kirby, M. E.

    2014-12-01

    High latitude drilling during IODP expedition 323 in the Bering Sea provides a unique opportunity to study in detail the evolution of Quaternary paleoceanography, climate and glacial history of the Bering Sea gateway to the Arctic Ocean. Our study focuses on a 400 ky interval of Quaternary marine sediments cored along the Bering Slope. Samples for magnetic analysis were obtained from sites U1339, U1343, U1344, U1345, at depths of 1008-3484 m. Sediments in these cores are a mixture of siliclastic material, derived primarily from terrigeneous sources, and biogenic material. Detailed measurements of the variation in bulk magnetic properties including natural remanent magnetization (NRM), susceptibility, ARM, and IRM, have been used to monitor changes in concentration, composition and grainsize of the magnetic components. In addition, sediment grain size analysis was preformed on biogenic free aliquots at selected intervals. Our results indicate that the dramatic bimodal magnetic intensity signal that alternates between a strong and weak NRM and magnetic susceptibility is associated with relatively course and fine grain sizes repectively. This is the opposite to the pattern estimated by our initial IODP Ex. 323 reports. Current models propose that, as has been observed in the North Atlantic, high intensities are likely to be related to high contributions of terrigenous and glaciomarine sediments deposited during glacial periods and low intensities are likely to occur during interglacials when continental sediments become trapped on the on the shelf. Contrary to this hypothesis, however, we find compelling evidence for a substantial increase in terrigenous input during the interglacial periods and what appears to be a predominantly pelagic signal during the glacial periods. Comparison of our data with other proxy data including oxygen isotopes, NGR, GRA allows us to investigate the possible causal links between these changes and the environmental history of the North

  5. Bering Sea surface water conditions during Marine Isotope Stages 12 to 10 at Navarin Canyon (IODP Site U1345)

    NASA Astrophysics Data System (ADS)

    Caissie, Beth E.; Brigham-Grette, Julie; Cook, Mea S.; Colmenero-Hidalgo, Elena

    2016-09-01

    Records of past warm periods are essential for understanding interglacial climate system dynamics. Marine Isotope Stage 11 occurred from 425 to 394 ka, when global ice volume was the lowest, sea level was the highest, and terrestrial temperatures were the warmest of the last 500 kyr. Because of its extreme character, this interval has been considered an analog for the next century of climate change. The Bering Sea is ideally situated to record how opening or closing of the Pacific-Arctic Ocean gateway (Bering Strait) impacted primary productivity, sea ice, and sediment transport in the past; however, little is known about this region prior to 125 ka. IODP Expedition 323 to the Bering Sea offered the unparalleled opportunity to look in detail at time periods older than had been previously retrieved using gravity and piston cores. Here we present a multi-proxy record for Marine Isotope Stages 12 to 10 from Site U1345, located near the continental shelf-slope break. MIS 11 is bracketed by highly productive laminated intervals that may have been triggered by flooding of the Beringian shelf. Although sea ice is reduced during the early MIS 11 laminations, it remains present at the site throughout both glacials and MIS 11. High summer insolation is associated with higher productivity but colder sea surface temperatures, which implies that productivity was likely driven by increased upwelling. Multiple examples of Pacific-Atlantic teleconnections are presented including laminations deposited at the end of MIS 11 in synchrony with millennial-scale expansions in sea ice in the Bering Sea and stadial events seen in the North Atlantic. When global eustatic sea level was at its peak, a series of anomalous conditions are seen at U1345. We examine whether this is evidence for a reversal of Bering Strait throughflow, an advance of Beringian tidewater glaciers, or a turbidite.

  6. Bering Sea summary report: Outer Continental Shelf oil and gas activities in the Bering Sea and their onshore impacts

    SciTech Connect

    Deis, J.; Pierson, R.; Kurz, F.

    1983-09-01

    Two federal offshore oil-and-gas lease sales have been held in the Bering Sea Subregion. Lease Sale 57, Norton Basin, was held on March 15, 1983. Lease Sale 70, St. George Basin, was held on April 12, 1983. The sale offered 479 tracts, of which 97 received bids. The Department of the Interior has indicated that it will accept 96 of the 97 high bids; however, to date, leases have not been awarded. The Department of the Interior was enjoined from issuing leases by the US District Court of Alaska because of possible impacts from postlease preliminary seismic activities on gray and right whales. In accordance with the Court's ruling, leases cannot be issued until the completion of a supplemental environmental impact statement, which is anticipated to occur in November 1983. Six lease offerings in the Bering Sea Subregion are scheduled through 1987. Six deep stratigraphic test wells are the only wells drilled to date in the Bering Sea Subregion. To date, oil companies have not submitted exploration plans for the Norton Basin Planning Area. Exploration in Norton Basin could begin in the summer of 1984, at the earliest. Exploration plans cannot be submitted for the St. George Basin Planning Area until the leases are awarded. At this time, various onshore areas are being considered as possible support bases for offshore oil-and-gas exploration. At this stage, before exploratory drilling has occurred and in the absence of a commercial discovery, plans for transporting petroleum from the Bering Sea to markets in the United States are unclear. The current estimates of risked resources for lands leased in Lease Sale 57, Norton Basin, are 33 million barrels of oil and 110 billion cubic feet of gas. Lease Sale 70, St. George Basin, estimates of risked resources for leased lands are 27 million barrels of oil and 310 billion cubic feet of gas. 55 references, 10 figures, 3 tables.

  7. Large sand waves in Navarinsky Canyon head, Bering Sea

    USGS Publications Warehouse

    Karl, Herman A.; Carlson, P.R.

    1982-01-01

    Sand waves are present in the heads of large submarine canyons in the northwestern Bering Sea. They vary in height between 2 to 15 m and have wavelengths of 600 m. They are not only expressed on the seafloor, but are also well defined in the subsurface and resemble enormous climbing bed forms. We conjecture that the sand waves originated during lower stands of sea level in the Pleistocene. Although we cannot explain the mechanics of formation of the sand waves, internal-wave generated currents are among four types of current that could account for these large structures. ?? 1982 A. M. Dowden, Inc.

  8. Influence of the St. Lawrence island Polynya upon the Bering Sea benthos

    SciTech Connect

    Grebmeier, J.M.; Cooper, L.W. |

    1995-03-15

    The influence of a polynya, a persistent ice-free region, on water column production and subsequent transport to the shallow continental shelf benthos of the Bering Sea was evaluated by studying spatial patterns of organic material deposition, benthic biomass, community sediment metabolism, benthic population structure, and other potential indicators of enhanced organic carbon transport to benthic communities underlying the St. Lawrence Island Polynya. Despite suggestions that polynyas may be important localized centers of primary productions in polar waters, the authors found that the St. Lawrence Island Polynya does not obviously enhance the biomass of benthic communities directly below the polynya. However, southward flowing, baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of Bering Sea benthic communities south of St. Lawrence Island. These currents appear to affect mean sediment oxygen consumption, surface organic carbon/nitrogen ratios, total organic content, and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island. A particle-reactive, short-lived, natural radioisotope, {sup 7}Be, used as an indicator of rapid (days to weeks) deposition of particulate material from the water column, was detected only in surface sediments to the southwest of the island, indicating enhancement of particle deposition to the southwest of the island. Finally, the {sup 18}O content of tunicate cellulose was highest in the polynya region, consistent with increased filter feeding in the late winter when the polynya is present. The Anadyr Current, consisting of nutrient-rich, deeper Bering Sea water that is upwelled onto the shelf in the Gulf of Anadyr, flows west to east in the region south of St. Lawrence Island throughout the year and is the major forcing function for high production in the region. 76 refs., 13 figs., 5 tabs.

  9. Influence of the St. Lawrence Island Polynya upon the Bering Sea benthos

    NASA Astrophysics Data System (ADS)

    Grebmeier, Jacqueline M.; Cooper, Lee W.

    1995-03-01

    The influence of a polynya, a persistent ice-free region, on water column production and subsequent transport to the shallow continental shelf benthos of the Bering Sea was evaluated by studying spatial patterns of organic material deposition, benthic biomass, community sediment metabolism, benthic population structure, and other potential indicators of enhanced organic carbon transport to benthic communities underlying the St. Lawrence Island Polynya. Despite suggestions that polynyas may be important localized centers of primary production in polar waters, we found that the St. Lawrence Island Polynya does not obviously enhance the biomass of benthic communities directly below the polynya. However, southward flowing, baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of Bering Sea benthic communities south of St. Lawrence Island. These currents appear to affect mean sediment oxygen consumption, surface organic carbon/nitrogen ratios, total organic content, and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island. A particle-reactive, short-lived, natural radioisotope, 7Be, used as an indicator of rapid (days to weeks) deposition of particulate material from the water column, was detected only in surface sediments to the southwest of the island, indicating enhancement of particle deposition to the southwest of the island. Finally, the 18O content of tunicate cellulose was highest in the polynya region, consistent with increased filter feeding in the late winter when the polynya is present, and presumably promoting primary production in the open water. The Anadyr Current, consisting of nutrient-rich, deeper Bering Sea water that is upwelled onto the shelf in the Gulf of Anadyr, flows west to east in the region south of St. Lawrence Island throughout the year and is the major forcing function for high production in the region. The

  10. 76 FR 71913 - Fisheries of the Exclusive Economic Zone Off Alaska; “Other Flatfish” in the Bering Sea Subarea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-21

    ... Economic Zone Off Alaska; ``Other Flatfish'' in the Bering Sea Subarea of the Bering Sea and Aleutian... for ``other flatfish'' in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to prevent exceeding the 2011 allocation of ``other flatfish'' in the BSAI. DATES: Effective...

  11. 50 CFR 600.1105 - Longline catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish fishery program. 600.1105 Section... Capacity Reduction Regulations § 600.1105 Longline catcher processor subsector of the Bering Sea and... catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish...

  12. 50 CFR 600.1105 - Longline catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish fishery program. 600.1105 Section... Capacity Reduction Regulations § 600.1105 Longline catcher processor subsector of the Bering Sea and... catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish...

  13. 50 CFR 600.1105 - Longline catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish fishery program. 600.1105 Section... Capacity Reduction Regulations § 600.1105 Longline catcher processor subsector of the Bering Sea and... catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish...

  14. 50 CFR 600.1105 - Longline catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish fishery program. 600.1105 Section... Capacity Reduction Regulations § 600.1105 Longline catcher processor subsector of the Bering Sea and... catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish...

  15. 78 FR 54591 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-05

    ... Economic Zone Off Alaska; Greenland Turbot in the Bering Sea and Aleutian Islands Management Area AGENCY... Greenland turbot in the Bering Sea subarea of the Bering Sea and Aleutian Islands Management Area (BSAI). This action is necessary to fully use the 2013 initial total allowable catch (ITAC) of Greenland...

  16. 75 FR 4491 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-28

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY... mackerel in the Eastern Aleutian District and the Bering Sea subarea of the Bering Sea and Aleutian Islands... necessary to fully use the 2010 A season total allowable catch (TAC) of Atka mackerel in these...

  17. 75 FR 3873 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-25

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY... mackerel in the Eastern Aleutian District and the Bering Sea subarea of the Bering Sea and Aleutian Islands... necessary to prevent exceeding the 2010 A season total allowable catch (TAC) of Atka mackerel in these...

  18. Side-scan sonar assessment of gray whale feeding in the Bering Sea

    USGS Publications Warehouse

    Johnson, K.R.; Nelson, C.H.

    1984-01-01

    Side-scan sonar was used to map and measure feeding pits of the California gray whale over 22,000 square kilometers of the northeastern Bering Sea floor. The distribution of pits, feeding whales, ampeliscid amphipods (whale prey), and a fine-sand substrate bearing the amphipods were all closely correlated. The central Chirikov Basin and nearshore areas of Saint Lawrence Island supply at least 6.5 percent of the total gray whale food resource in summer. While feeding, the whales resuspend at least 1.2 x 108 cubic meters of sediment annually; this significantly affects the geology and biology of the region.

  19. 50 CFR Figure 16 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Bering Sea Habitat Conservation Area 16 Figure 16 to part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Fig. 16 Figure 16 to part 679—Bering Sea Habitat Conservation Area ER25JY08.010...

  20. 50 CFR Table 42 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Bering Sea Habitat Conservation Area 42 Table 42 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 42 Table 42 to Part 679—Bering Sea Habitat Conservation Area Longitude...

  1. 50 CFR Figure 16 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Bering Sea Habitat Conservation Area 16 Figure 16 to part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Fig. 16 Figure 16 to part 679—Bering Sea Habitat Conservation Area ER25JY08.010...

  2. 50 CFR Table 42 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Bering Sea Habitat Conservation Area 42 Table 42 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 42 Table 42 to Part 679—Bering Sea Habitat Conservation Area Longitude...

  3. 50 CFR Figure 16 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Bering Sea Habitat Conservation Area 16 Figure 16 to part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Fig. 16 Figure 16 to part 679—Bering Sea Habitat Conservation Area ER25JY08.010...

  4. 50 CFR Figure 16 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Bering Sea Habitat Conservation Area 16 Figure 16 to part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Fig. 16 Figure 16 to part 679—Bering Sea Habitat Conservation Area ER25JY08.010...

  5. 50 CFR Table 42 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Bering Sea Habitat Conservation Area 42 Table 42 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 42 Table 42 to Part 679—Bering Sea Habitat Conservation Area Longitude...

  6. 50 CFR Figure 16 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Bering Sea Habitat Conservation Area 16 Figure 16 to part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Fig. 16 Figure 16 to part 679—Bering Sea Habitat Conservation Area ER25JY08.010...

  7. 50 CFR Table 42 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Bering Sea Habitat Conservation Area 42 Table 42 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 42 Table 42 to Part 679—Bering Sea Habitat Conservation Area Longitude...

  8. 50 CFR Table 42 to Part 679 - Bering Sea Habitat Conservation Area

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Bering Sea Habitat Conservation Area 42 Table 42 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... ALASKA Pt. 679, Table 42 Table 42 to Part 679—Bering Sea Habitat Conservation Area Longitude...

  9. Eastern Bering Sea shelf: oceanography and resources. Volumes 1 and 2

    SciTech Connect

    Hood, D.W.; Calder, J.A.

    1981-01-01

    This collection presents in a single document what is now known about the natural science of the eastern Bering Sea shelf. It also provides a credible scientific document from which estimates of the effects of oil and gas development in the continental shelf region of the eastern Bering Sea can be made. Chapters have been entered individually into the data base.

  10. 50 CFR Table 43 to Part 679 - Northern Bering Sea Research Area

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Northern Bering Sea Research Area 43... ALASKA Pt. 679, Table 43 Table 43 to Part 679—Northern Bering Sea Research Area Longitude Latitude 168 7... projected coordinate system is North American Datum 1983, Albers. * This boundary extends in a...

  11. 50 CFR Table 43 to Part 679 - Northern Bering Sea Research Area

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Northern Bering Sea Research Area 43... ALASKA Pt. 679, Table 43 Table 43 to Part 679—Northern Bering Sea Research Area Longitude Latitude 168 7... projected coordinate system is North American Datum 1983, Albers. * This boundary extends in a...

  12. 50 CFR Table 43 to Part 679 - Northern Bering Sea Research Area

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Northern Bering Sea Research Area 43... ALASKA Pt. 679, Table 43 Table 43 to Part 679—Northern Bering Sea Research Area Longitude Latitude 168 7... projected coordinate system is North American Datum 1983, Albers. * This boundary extends in a...

  13. 50 CFR Table 43 to Part 679 - Northern Bering Sea Research Area

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Northern Bering Sea Research Area 43... ALASKA Pt. 679, Table 43 Table 43 to Part 679—Northern Bering Sea Research Area Longitude Latitude 168 7... projected coordinate system is North American Datum 1983, Albers. * This boundary extends in a...

  14. Diatom evidence on Wisconsin and Holocene events in the Bering Sea

    USGS Publications Warehouse

    Sancetta, C.; Robinson, S.W.

    1983-01-01

    Previous work on surface (modern) sediments has defined diatom species which appear to be good indicators of various oceanographic/ecologic conditions in the North Pacific Ocean and marginal seas. Three long cores from the eastern and northern sides of the Aleutian Basin show changes in species assemblage which can be interpreted in terms of changes in the ocean environment during the last glaciation (Wisconsin) and the Holocene. The early and late Wisconsin maxima were times of prolonged annual sea-ice cover and a short cool period of phytoplankton productivity during the ice-free season. The middle Wisconsin interstade, at least in the southern Bering Sea, had greater seasonal contrast than today, with some winter sea-ice cover, an intensified temperature minimum, and high spring productivity. Variations in clastic and reworked fossil material imply varying degrees of transport to the basin by Alaskan rivers. The results of Jouse?? from the central Bering Sea generally correspond with those presented here, although there are problems with direct comparison. ?? 1983.

  15. Mesopelagic nekton and associated physics of the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Sinclair, E. H.; Stabeno, P. J.

    2002-12-01

    The mesopelagic community of fishes and squids are fundamental in the diet of apex predators, but in most cases their life histories and habitat requirements are poorly understood. In May 1999, a pilot study was conducted to identify mesopelagic nekton, describe dominant physical characteristics of their habitat, and compare their relative abundances over several study sites in the southeastern Bering Sea. Biological samples were collected at 250, 500, and 1000 m depths with an open pelagic rope trawl lined with 1.2-cm mesh in the codend. Net type, mesh size, and trawling techniques were designed to parallel those of extensive Russian research surveys in the western Bering Sea, permitting direct comparisons between study results. Forty-three species of fish and 15 species of cephalopods were identified, including a new species of gonatid squid and a range extension for Paraliparis paucidens, a snailfish never before observed in Alaskan waters. Faunal biomass was high with over 25,000 (1400 kg) fish and squid collected in only 13 trawls. Concentrations of fish in this area surpass published records from the western Bering Sea and North Pacific Ocean by an order of magnitude, driven primarily by Leuroglossus schmidti, a deep-sea smelt. Generally, specimens were of high quality, and new size records were established for several species of fish and squid. The physical environment as determined from altimetry, satellite-tracked drifters, and water properties (temperature and salinity) was typical of the last decade for this area. Spatial patterns in species distribution were observed, but further research is needed to determine whether these are a factor of mesoscale variability or of habitat characteristics.

  16. Improved method for correlating late Pleistocene/Holocene records from the Bering Sea: application of a biosiliceous/geochemical stratigraphy

    NASA Astrophysics Data System (ADS)

    Morley, Joseph J.; Robinson, Stephen W.

    1986-09-01

    The combination of high-resolution siliceous biostratigraphy and radiocarbon dating provides a mechanism for detailed assessment of the depositional history in late Pleistocene sediments from the Bering Sea where average accumulation rates are uncharacteristically high compared to rates calculated for most other ocean basins. Vital to the development of this stratigraphy was the recognition that the abundance pattern of the radiolarian species Cycladophora davisiana in Bering Sea cores is quite similar to this species' previously correlated abundance curve in a late Pleistocene/Holocene record from the northwest Pacific. Comparison of this high-resolution stratigraphy with other recently developed floral and lithologic stratigraphies for late Pleistocene Bering Sea sediments shows that the various stratigraphies do not always yield identical results when applied to a particular sediment sequence. With this new stratigraphy based upon a combination of siliceous microfaunal abundance patterns and radiocarbon dating, one can identify reworking, discontinuities and other interruptions in the depositional sequence more precisely than with previously devised stratigraphies, thereby improving the correlation techniques for comparison of late Pleistocene/Holocene records from this marginal sea.

  17. Environmental predictors of ice seal presence in the Bering Sea.

    PubMed

    Miksis-Olds, Jennifer L; Madden, Laura E

    2014-01-01

    Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20-30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season.

  18. Environmental Predictors of Ice Seal Presence in the Bering Sea

    PubMed Central

    Miksis-Olds, Jennifer L.

    2014-01-01

    Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20–30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season. PMID:25229453

  19. Microzooplankton grazing in the Eastern Bering Sea in summer

    NASA Astrophysics Data System (ADS)

    Stoecker, Diane K.; Weigel, Alison; Goes, Joaquim I.

    2014-11-01

    Dilution experiments to estimate microzooplankton grazing on phytoplankton were conducted during the summers of 2008, 2009, and 2010 in the Eastern Bering Sea as part of the BEST-BSIERP integrated ecosystem project. All three summers followed cold springs in the Bering Sea. Average microzooplankton grazing coefficients were relatively similar among regions, ranging from 0.16 to 0.34 d-1 in simulated in situ incubations with mixed-layer water collected from the depth of the 55% Io isolume. In Off Shelf and Outer Shelf domains, microzooplankton consumed 67-78% of phytoplankton daily growth but in the Middle and Inner Shelf domains, microzooplankton grazing exceeded phytoplankton daily growth. Regional estimates of microzooplankton ingestion of phytoplankton carbon ranged from 4.4 to 11.0 μg C d-1, with highest ingestion in the Off Shelf, Outer Shelf, and Alaska Peninsula regions and, lower ingestion in the Middle Shelf and Inner Shelf regions. On the northern Middle Shelf, a deep chlorophyll maximum (DCM) occurred at most stations. Grazing coefficients in the DCM were similar in magnitude to coefficients in the corresponding mixed layer. However, because of the higher phytoplankton biomass in the DCM, estimated microzooplankton ingestion and secondary production per liter were higher in the DCM than in the mixed layer. Measurements of photosynthetic quantum yields (Fv/Fm) in whole seawater and diluted treatments indicated that with some plankton assemblages, dilution had a negative effect on phytoplankton physiology and could have compromised their growth rates. This could have also resulted in an underestimation of microzooplankton grazing. Nevertheless, it is clear that microzooplankton grazing consumed most of the phytoplankton production in summer, and that microzooplankton were an important link in food webs supporting larger zooplankton and in carbon flow in the Eastern Bering Sea.

  20. Mesozoic and Cenozoic structural trends under southern Bering Sea Shelf

    SciTech Connect

    Marlow, M.S.; Cooper, A.K.

    1980-12-01

    Mesozoic rocks exposed near the tip of the Alaska Peninsula form an antiformal structure that flanks the southern side of Bristol Bay basin and that can be traced with geophysical data about 700 km offshore to the vicinity of the Pribilof Islands. Upper Jurassic sandstone and Upper Cretaceous mudstone dredged from the top and flanks of this structure near the islands confirm that Mesozoic rocks extend from the Alaska Peninsula to the Bering sea margin. The southern part of the Bering Sea Shelf is underlain by several large structural basins. These filled basins encompass an offshore area of about 31,000 sq km. Reflection profiles show that the surface of the offshore antiformal structures is an angular unconformity overlain by Cenozoic beds. The downdip trace of the unconformity in Bristol Bay basin is underlain by reflectors paralleling the contact, a relation suggesting that the basin and perhaps other shelf basins may be underlain by ancient Mesozoic depocenters. The bulk of the thick sections in these basins is, however, thought to be mainly Cenozoic in age. Strata in the basins are cut by high-angle growth faults. The faults commonly offset the seafloor, which implies that basin subsidence and filling continue to the present. Shallow-water diatomaceous mudstone of Eocene and Oligocene age dredged from the continental slope near the Pribilof Islands indicates that collapse of the margin and outer shelf basins began by at least early Tertiary time. In Mesozoic time, the Bering margin between Siberia and the Alaska Peninsula (Beringian margin) may have been a zone of either oblique underthrusting or transform motion between the North American and Pacific lithosphere (Kula plate.). This motion may have rifted the edge of the North American plate, resulting in the formation of a series of elongate basins and ridges paralleling the plate edge.

  1. Shallow-water habitat use by Bering Sea flatfishes along the central Alaska Peninsula

    NASA Astrophysics Data System (ADS)

    Hurst, Thomas P.

    2016-05-01

    Flatfishes support a number of important fisheries in Alaskan waters and represent major pathways of energy flow through the ecosystem. Despite their economic and ecological importance, little is known about the use of habitat by juvenile flatfishes in the eastern Bering Sea. This study describes the habitat characteristics of juvenile flatfishes in coastal waters along the Alaska Peninsula and within the Port Moller-Herendeen Bay system, the largest marine embayment in the southern Bering Sea. The two most abundant species, northern rock sole and yellowfin sole, differed slightly in habitat use with the latter occupying slightly muddier substrates. Both were more common along the open coastline than they were within the bay, whereas juvenile Alaska plaice were more abundant within the bay than along the coast and used shallow waters with muddy, high organic content sediments. Juvenile Pacific halibut showed the greatest shift in distribution between age classes: age-0 fish were found in deeper waters (~ 30 m) along the coast, whereas older juveniles were found in the warmer, shallow waters within the bay, possibly due to increased thermal opportunities for growth in this temperature-sensitive species. Three other species, starry flounder, flathead sole, and arrowtooth flounder, were also present, but at much lower densities. In addition, the habitat use patterns of spring-spawning flatfishes (northern rock sole, Pacific halibut, and Alaska plaice) in this region appear to be strongly influenced by oceanographic processes that influence delivery of larvae to coastal habitats. Overall, use of the coastal embayment habitats appears to be less important to juvenile flatfishes in the Bering Sea than in the Gulf of Alaska.

  2. Fisheries imaging radar surveillance test /FIRST/ - Bering Sea test

    NASA Technical Reports Server (NTRS)

    Woods, E. G.; Ivey, J. H.

    1977-01-01

    A joint NOAA, U.S. Coast Guard and NASA program is being conducted to determine if a synthetic aperture radar (SAR) system, such as planned for NASA's SEASAT, can be useful in monitoring fishing vessels within the newly established 200-mile fishing limit. As part of this program, data gathering field operations were conducted over concentrations of foreign fishing vessels in the Bering Sea off Alaska in April 1976. The Jet Propulsion Laboratory developed synthetic aperture L-band radar which was flown aboard the NASA Convair 990 aircraft, with a Coast Guard cutter and C-130 aircraft simultaneously gathering data to provide both radar imagery and sea truth information on the vessels being imaged. Results indicate that synthetic aperture radar systems have potential for all weather detection, enumeration and classification of fishing vessels.

  3. Biophysical ocean observation in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Stafford, Kathleen M.; Moore, Sue E.; Stabeno, Phyllis J.; Holliday, D. V.; Napp, Jeffrey M.; Mellinger, David K.

    2010-01-01

    Integrated ocean observation, from physical and atmospheric forcing mechanisms to the distribution and abundance of top-level predators, is critical to the investigation of marine ecosystems and the impact of climate change on them. We integrated data from a biophysical mooring in the southeast Bering Sea to create a one-year snapshot of ocean dynamics in this remote large marine ecosystem. Distinct patterns in production (chlorophyll), zooplankton biovolume (copepods and euphausiids) and the occurrence of zooplankton predators (fin and right whales) were defined and related to discrete features in the annual physical cycle. Peaks in prey and predator cycles were linked to spikes in fluorescence that occurred at the onset of water column stratification in late spring 2006 and the appearance of sea ice in late winter 2007. These data illustrate the capability and potential of integrated ocean observing systems (IOOS) to describe seasonal variability and linkages in a remote marine ecosystem.

  4. Depositional and erosional features of the inner shelf, northeastern Bering Sea.

    USGS Publications Warehouse

    Hunter, R.E.; Thor, D.R.; Swisher, M.L.

    1981-01-01

    Sonographs and bathymetric profiles from water depths less than 15m in the Nome-Solomon, Port Clarence, and Yukon Delta areas of the Alaskan Bering Sea coast show features generated by waves, currents, and drifting ice. The surficial sediments in the Nome-Solomon and Port Clarence areas range in grain size from sand to boulder gravel and have many surface features visible on sonographs, whereas the sediments off the Yukon Delta are fine sands and silts that have few such features. Materials in the Nome-Solomon and Port Clarence areas have been seggregated by grain size into ribbons and irregular, elongate, and lobate patches. Coarse sand and fine gravel patches and ribbons are characterized by symmetrical ripples generated by storm waves. Ice-gouged furrows occur in all the nearshore areas studied.-from Authors

  5. Skate Bathyraja spp. egg predation in the eastern Bering Sea.

    PubMed

    Hoff, G R

    2009-01-01

    Predation on skate eggs by snails was examined for three skate species at seven nursery sites in three regions (north, middle and south) of the eastern Bering Sea. Mean predation levels were 6.46% for the Alaska skate Bathyraja parmifera, 2.65% for the Aleutian skate Bathyraja aleutica and 22.25% for the Bering skate Bathyraja interrupta. Predation levels were significantly higher at the middle and north sites than the south sites for all species combined. Predation levels decreased with increasing egg-case densities at all nursery sites, and the highest predation levels occurred where egg-case densities were very low. Predated egg-case density increased with increasing snail densities across all nursery sites examined. The Oregon triton Fusitriton oregonensis was the most abundant snail species at all nursery sites and displayed ability to drill holes in the egg case of B. parmifera. Holes left by predatory snails in egg cases of B. parmifera were significantly larger, and of different shape at the middle site compared to the south site. Holes in B. parmifera were also significantly larger than those in egg cases of B. interrupta across all sites examined. Egg cases of B. aleutica possess surface spines that cover the egg case and may inhibit predation by snails at a greater rate than that of the B. parmifera and B. interrupta, which have a smoother egg-case surface.

  6. Sea Surface Conditions during Marine Isotope Stages 12 to 10 at Navarin Canyon in the Bering Sea (IODP Site U1345)

    NASA Astrophysics Data System (ADS)

    Caissie, B.; Brigham-Grette, J.; Colmenero-Hidalgo, E.; Cook, M. S.; Mix, A. C.

    2012-12-01

    Records of terrestrial-marine coupling during past warming intervals are essential for understanding climate system dynamics. The Bering Sea is ideally situated to record how opening or closing the Pacific-Arctic ocean gateway (Bering Strait) impacts primary productivity, sea ice, and sediment transport and how these changes in the marine realm correspond with changes on the Bering land bridge. Very little is known about this region prior to 125 ka. IODP Expedition 323 to the Bering Sea offered an unparalleled chance to look in detail at time periods deeper than had previously been retrieved using gravity and piston cores. Here we look at the sea surface conditions at Site U1345, located near the shelf-slope break in the Bering Sea. We present an orbitally-tuned age model based on the oxygen isotopic composition of benthic foraminifera. We then focus in detail on the climate transitions during Marine Isotope Stages (MIS) 12 to 10 (435-365 ka). The site is near the marginal ice zone today and similarly experienced seasonal sea ice throughout both the glacial and interglacial stages, recorded as relatively high percentages of sea-ice related diatoms throughout the study interval. Diatom assemblage turnovers occur at 425 ka, 410 ka, 400 ka, and 377 ka, and reflect changes in upwelling, sea ice, glacial ice, and potentially even current direction. The diatom assemblage record, supported by calcareous nannofossil abundances, shows that MIS 11 is bracketed by highly productive laminated intervals. These laminated intervals are coeval with flooding of the Beringian shelf at 425 and 377 ka. Upwelling was robust during the termination laminations and MIS 10 laminations, and moderate during late MIS 11. Productivity increases in the Bering Sea occur coeval with high productivity pulses in the North Atlantic and may be related to sea level rise and flooding of Bering Strait. Beginning at approximately 410 ka, both insolation and obliquity began to decline and some mountainous

  7. Changes in the distribution and abundance of albatrosses in the eastern Bering Sea: 1975-2010

    NASA Astrophysics Data System (ADS)

    Kuletz, Kathy J.; Renner, Martin; Labunski, Elizabeth A.; Hunt, George L.

    2014-11-01

    A number of marine species are showing poleward shifts in their distributions in response to climate warming. Three albatross species frequent the Bering Sea, the Laysan (Phoebastria immutabilis), the black-footed (Phoebastria nigripes), and the endangered short-tailed albatross (Phoebastria albatrus). To determine if albatrosses changed their distribution or abundance in the eastern Bering Sea between 1975 and 2010, we examined at-sea survey data using the North Pacific Pelagic Seabird Database. Within our study area, all three species of albatross occurred most frequently in the waters of the Aleutian Islands. In the eastern Bering Sea, all three species were most abundant near the shelf break, and in particular in the vicinity of the major submarine canyons in the shelf slope. Starting in the 1990s, population densities increased for all three albatross species, with a marked increase in the 2000s. In the 2000s, there was also an increase in the frequency at which albatrosses were recorded in the central and northern Bering Sea. Both black-footed and short-tailed albatrosses shifted the centers of their Bering Sea distributions northward. The Laysan albatross center of distribution shifted southward due to increased numbers along the southern shelf break, but densities also increased northward. We suggest that the observed changes in distribution and abundance of the three albatross species in the eastern Bering Sea may have been responses to an increase in the availability of squid, their primary prey, there. Additionally, the expansion of the distribution of the short-tailed albatross in the eastern Bering Sea may represent the reclamation of its previous range, now that the population is beginning to recover from near extinction caused by over harvesting. We suggest that predicted increases in ocean temperatures and northward movement of prey could result in albatrosses and other marine apex predators foraging farther north along the Bering Sea shelf and

  8. IODP Exp 323 Site U1342 from the Bering Sea may indicate past changes in ocean ventilation and climate

    NASA Astrophysics Data System (ADS)

    Knudson, K. P.; Ravelo, C.

    2011-12-01

    The Bering Sea represents a gateway between the North Pacific Ocean and the Arctic Ocean and may provide insights into past changes in circulation between the oceans. Changes in ocean circulation within the Bering Sea may be related to global climate cycles on orbital to sub-orbital timescales, but the role and nature of Bering Sea climate changes has never been studied in detail before long, continuous cores were drilled as part of the Integrated Ocean Drilling Program (IODP) Expedition 323. IODP Site U1342 is ideally situated to reconstruct changes in climate and ocean circulation. As the shallowest of the Exp 323 sites, it is located within the present-day oxygen minimum zone (OMZ), which may display changes in intensity and depth in response to variations in intermediate water ventilation and surface productivity. Alternations within the core between massive bioturbated sediments, dominated by fine-grained siliciclastic and diatom oozes that are sometimes laminated, attests to large changes in climate and OMZ conditions recorded at this site. We present new δ13C and δ18O records at IODP Site U1342 from benthic foraminifera species Uvigerina perigrina. Our results show variations in δ18O indicating the presence of all late Pleistocene marine isotope stages. Comparison of our δ18O record with the lithologic changes indicates that the low-density, diatom-rich (sometimes laminated) intervals at this site occur at higher frequencies than the 100K glacial cycles. These intervals are found predominantly in sediments deposited during interglacial times, although not during the warmest part of the interglacials. Additionally, our results show that δ13C values are generally lower in glacial intervals. Overall, future work at IODP Site U1342 will determine the history of past changes in ocean ventilation within the Bering Sea.

  9. Hydrography and biological resources in the western Bering Sea

    NASA Astrophysics Data System (ADS)

    Khen, G. V.; Basyuk, E. O.; Vanin, N. S.; Matveev, V. I.

    2013-10-01

    The variability of temperature, salinity, dissolved oxygen and nutrients (phosphate and silicate) in the west Bering Sea in the Russian Exclusive Economic Zone (REZ) since 1950 and the influence of these factors on the distribution and dynamics of hydrobionts were studied. Since 1950, the sea surface temperature has been gradually increasing, although non-significant cooling occurred in the last decade. In contrast, in the 50-200 m depth range, the temperature has been cooling. During the last 60 years, the salinity decreased by 0.30, 0.06-0.10 and 0.04 at the sea surface, at the 100-200 m layer and at the depth of 500 m, respectively, resulting in a strengthening of the vertical stability and weakening of the vertical water exchange. As a consequence, the oxygen concentrations at depths down to 1000 m decreased during this period. Phosphate and silicate concentrations increased during the last 40 years. The water exchange with the North Pacific (based on the discharge through the Kamchatka Strait) from the mid-1960s to the early 1990s was 2-3-fold higher than in the 1950s or from the mid-1990s to 2010. During the periods of weakened water exchange, the herring population sharply increased, while during periods of strengthened water exchange, pollock biomass increased. The increase of codfishes, flounders and sculpin biomass at the sea shelf during the second half of the 20th century coincided with sea surface warming. Since 2007, the westward water transport from the Aleutian Basin was almost half that during 2002-06, while the northward stream from Near Strait noticeably increased. The populations of immature chum, sockeye and chinook in the REZ declined because of their weakened input from the US zone, and these species were distributed mainly in the northern and eastern Russian waters. Taking into account the cooling since the middle of the last decade, the change in the intensity and direction of the Aleutian Low and Siberian High trends, and the westward

  10. An Interdecadal Increase in the Spring Bering Sea Ice Cover in 2007

    NASA Astrophysics Data System (ADS)

    Wu, Renguang; Chen, Zhang

    2016-03-01

    The sea ice coverage of the Northern Hemisphere as a whole has been declining since 1979. On contrary, the March-April sea ice concentration in the Bering Sea experienced a prominent increase in year 2007. The present study documents the changes in surface air temperature, surface heat fluxes, sea surface temperature, and atmospheric circulation accompanying the above interdecadal change in the Bering Sea ice concentration. It is shown that an obvious decrease in surface air temperature, sea surface temperature, and surface net shortwave radiation occurred in concurrent with the sea ice increase. The surface air temperature decrease is associated with a large-scale circulation change, featuring a decrease in sea level pressure extending from the Pacific coast of Alaska to northwestern Europe and an increase in sea level pressure over the high-latitude Asia and the high-latitude North Atlantic Ocean. The enhancement of northwesterly winds over the Bering Sea led to a large decrease in surface air temperature there. The associated increase in upward turbulent heat flux cooled the sea surface temperature in the waters south of the ice covered region, favoring the southward expansion of ice extent. This, together with a positive ice-albedo feedback, amplified the sea ice anomalies after they were initiated, leading to the interdecadal increase in sea ice in the Bering Sea.

  11. A reassessment of primary production and environmental change in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Brown, Zachary W.; van Dijken, Gert L.; Arrigo, Kevin R.

    2011-08-01

    Regarded as one of the world's most productive marine environments, the Bering Sea is widely thought to be rapidly warming and losing sea ice. Such changes would be expected to have dramatic impacts on primary producers, with cascading effects on upper trophic levels, including this region's vast commercial fisheries resources. Here, we use satellite-derived sea ice concentration, sea surface temperature, and ocean color data as input to a primary productivity algorithm to take stock of environmental change and primary production in the Bering Sea. Results show that, rather than declining, mean annual sea ice extent in the Bering Sea has exhibited no significant change over the satellite sea ice record (1979-2009). Furthermore, significant warming during the satellite sea surface temperature record (1982-2009) is mainly limited to the summer months, when all regions of the Bering Sea warmed. This warming suggests increasing stratification during the phytoplankton growth season. Despite certain hot spots of primary production and a strong pulse in the spring, the rate of annual area-normalized primary production in the Bering Sea (124 g C m-2 yr-1) is below the global mean (140 g C m-2 yr-1). Between 1998 and 2007, basin-wide annual primary production ranged from 233 to 331 Tg C yr-1 under the influence of highly variable sea ice and temperature conditions. By comparing warm, low-ice years (2001-2005) with cold, high-ice years (1998-2000 and 2006-2007), we speculate that Bering Sea primary productivity is likely to rise under conditions of future warming and sea ice loss.

  12. 76 FR 40628 - Groundfish Fisheries of the EEZ Off Alaska; Pacific Halibut Fisheries; CDQ Program; Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-11

    ... Coonstripe 864 Humpy 963 Northern (pink) 961 Sidestripe 962 Spot 965 Snails 890 Urchin, green sea 893 Urchin... EEZ Off Alaska; Pacific Halibut Fisheries; CDQ Program; Bering Sea and Aleutian Islands King and... Bering Sea and Aleutian Islands Management Area (BSAI FMP). With Federal oversight, the State of...

  13. Seasonal distribution of short-tailed shearwaters and their prey in the Bering and Chukchi seas

    NASA Astrophysics Data System (ADS)

    Nishizawa, Bungo; Matsuno, Kohei; Labunski, Elizabeth A.; Kuletz, Kathy J.; Yamaguchi, Atsushi; Watanuki, Yutaka

    2017-01-01

    The short-tailed shearwater (Ardenna tenuirostris) is one of the abundant marine top predators in the Pacific; this seabird spends its non-breeding period in the northern North Pacific during May-October and many visit the southern Chukchi Sea in August-September. We examined potential factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill, was sampled by net tows in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters were mainly distributed in the southeastern Bering Sea/Aleutian Islands (60 ± 473 birds km-2) in July 2013, and in the Bering Strait/southern Chukchi Sea (19 ± 91 birds km-2) in September 2012. In the Bering Strait/southern Chukchi Sea, krill size was greater in September 2012 (9.6 ± 5.0 mm in total length) than in July 2013 (1.9 ± 1.2 mm). Within the Bering Strait/southern Chukchi Sea in September 2012, short-tailed shearwaters occurred more frequently in cells (50 × 50 km) where large-sized krill were more abundant. These findings, and information previously collected in other studies, suggest that the seasonal northward movement of short-tailed shearwaters might be associated with the seasonal increase in krill size in the Bering Strait/southern Chukchi Sea. We could not, however, rule out the possibility that large interannual variation in krill abundance might influence the seasonal distribution of shearwaters. This study highlights the importance of krill, which is advected from the Pacific, as an important prey of top predators in the Arctic marine ecosystem.

  14. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, Victor C.; McNamara, Daniel E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75–90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means.

  15. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, V.C.; McNamara, D.E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75-90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means. Copyright 2011 by the American Geophysical Union.

  16. Deglacial Timing and Dynamics of Paleoclimate Variations in the Bering Sea and Subarctic Pacific

    NASA Astrophysics Data System (ADS)

    Lembke-Jene, Lester; Kuehn, Hartmut; Gersonde, Rainer; Esper, Oliver; Arz, Helge; Lohmann, Gerrit; Tiedemann, Ralf

    2016-04-01

    One characteristic of the last glacial termination is the widespread decrease of mid-depth oxygen concentrations in the world ocean in intermediate water depth (i.e. above c. 2000 m). The resulting expansion of oxygen minimum zones is connected with the deposition of high-resolution, laminated sediments throughout the subarctic North Pacific, providing the potential to study marine archives with a high temporal resolution, combined with the possibility to establish relatively precise chronostratigraphic frameworks. From a comprehensive collection of sediment cores retrieved during R/V Sonne cruise SO202 INOPEX, we investigated sites in the Bering Sea that featured laminated deglacial facies. Sedimentary layer countings of laminated sections, AMS 14C measurements of foraminifera and correlation to the NGRIP Greenland oxygen isotope ice core record, aided by high-resolution micro-XRF data, X-ray images and supplementary geochemical data gave detailed information about the processes that led to laminae formation and provided the basis for establishing paleoceanographic reconstructions with exceptional temporal resolution, possibly on sub-decadal timescales. We selected one partly laminated, mid-depth key site from 1100 m water depth on the northeastern Bering Shelf slope to further investigate the timing, and surface - intermediate water development during the Termination I. A correlation between the NGRIP oxygen isotope reference record and our layer countings revealed that the laminations represent annual layered sediments (varves) and the presence of these laminations is tightly coupled to submillennial, short-term warm phases, especially during the Bølling-Allerød. The latter point strongly argues for a close atmospheric teleconnection between the North Atlantic and the North Pacific. As a result of our correlation approach we created an age model that is partly independent from radiocarbon dates in the varved time intervals. We used our resulting

  17. Sub-Regional Sea Ice Preferences of Pacific Walrus in the Bering Sea Using SAR Data

    NASA Astrophysics Data System (ADS)

    Sacco, A.; Mahoney, A. R.; Eicken, H.; Johnson, M. A.; Ray, C.

    2014-12-01

    The Pacific walrus (O. r. divergens) uses winter sea ice in the Bering Sea for numerous parts of its natural history including courtship, foraging, and migration. Recent and predicted loss of sea ice has caused the Pacific walrus to be considered for an elevated status under the Endangered Species Act. Study of the ice conditions during this period is required to investigate changes in the Bering Sea ice pack and its effects on walrus sustainability. Using Radarsat-1 data and second-order texture statistics, a classification system was devised to separate sea ice into three distinguishable classes based on walrus needs of open water availability in the pack ice: discontinuous pack ice, continuous pack ice, and open water. Classifications are performed on sub-regional image areas to facilitate classification of heterogeneous seascapes which are thought to be distinguishable by walrus. Spatial, as well as temporal, changes in the seascape cover, based on the classification, are achieved. These results are then combined with ship-based observations of walrus to quantify walrus habitat preference. The three-class algorithm has a success rate of 94% for the discontinuous ice and continuous pack ice. Radarsat-1 images from 2004 - 2008 were analyzed for changes in seasonal and annual discontinuous ice extent. After classification, the spatial extent of discontinuous ice was found to vary throughout 2004 - 2008 in the Bering Sea shelf. Walrus are also shown to prefer discontinuous pack far from the southernmost ice edge. Maps of walrus habitat preference and persistent areas of sea ice seascapes are created and then can be used for the walrus' status consideration under the Endangered Species Act in addition to general species management issues.

  18. Late Quaternary paleoceanography of the Pervenets Canyon area of the Bering Sea: evidence from the diatom flora

    USGS Publications Warehouse

    Starratt, S.W.

    1993-01-01

    Sediments from three gravity cores from an east-west shelf-to-slope transect along the axis of Pervenets Canyon in the northern Navarin basin, Bering Sea were analyzed for diatoms. The diatom floras present in the cores were divided into four assemblages. The Bering Basin (deep water open ocean) and Sea Ice (ice cover at least six months per year) Assemblages were dominant in each core. The taxa that comprise the Bering Shelf Assemblage (continental shelf) indicate that downslope transport plays only a minor part in the development of the thanatocenoses. The presence (up to 10% of the total valve count) of the Productivity Assemblage, which consists mainly of poorly silicified, easily dissolved taxa, indicates that nutrient flux is relatively high in the region. Several taxa can be used as proxy indicators for specific water masses. The relative downcore abundance of these taxa was used to approximate the Pleistocene-Holocene boundary (recognized in Core 80-65 at a depth of about 75 cm). -from Author

  19. 50 CFR Figure 20 to Part 679 - Steller sea lion conservation area (SCA) of the Bering Sea

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Steller sea lion conservation area (SCA) of the Bering Sea 20 Figure 20 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 20 Figure 20 to Part 679—Steller sea lion conservation...

  20. 50 CFR Figure 20 to Part 679 - Steller sea lion conservation area (SCA) of the Bering Sea

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Steller sea lion conservation area (SCA) of the Bering Sea 20 Figure 20 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 20 Figure 20 to Part 679—Steller sea lion conservation...

  1. 50 CFR Figure 20 to Part 679 - Steller sea lion conservation area (SCA) of the Bering Sea

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Steller sea lion conservation area (SCA) of the Bering Sea 20 Figure 20 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 20 Figure 20 to Part 679—Steller sea lion conservation...

  2. 50 CFR Figure 20 to Part 679 - Steller sea lion conservation area (SCA) of the Bering Sea

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Steller sea lion conservation area (SCA) of the Bering Sea 20 Figure 20 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 20 Figure 20 to Part 679—Steller sea lion conservation...

  3. 50 CFR Figure 20 to Part 679 - Steller sea lion conservation area (SCA) of the Bering Sea

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Steller sea lion conservation area (SCA) of the Bering Sea 20 Figure 20 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 20 Figure 20 to Part 679—Steller sea lion conservation...

  4. Divergent movements of walrus and sea ice in the Nothern Bering Sea

    USGS Publications Warehouse

    Jay, Chadwick V.; Udevitz, Mark S.; Kwok, Ron; Fischbach, Anthony S.; Douglas, David C.

    2010-01-01

    The Pacific walrus Odobenus rosmarus divergens is a large Arctic pinniped of the Chukchi and Bering Seas. Reductions of sea ice projected to occur in the Arctic by mid-century raise concerns for conservation of the Pacific walrus. To understand the significance of sea ice loss to the viability of walruses, it would be useful to better understand the spatial associations between the movements of sea ice and walruses. We investigated whether local-scale (~1 to 100 km) walrus movements correspond to movements of sea ice in the Bering Sea in early spring, using locations from radio-tracked walruses and measures of ice floe movements from processed synthetic aperture radar satellite imagery. We used generalized linear mixed-effects models to analyze the angle between walrus and ice floe movement vectors and the distance between the final geographic position of walruses and their associated ice floes (displacement), as functions of observation duration, proportion of time the walrus was in water, and geographic region. Analyses were based on 121 walrus-ice vector pairs and observations lasting 12 to 36 h. Angles and displacements increased with observation duration, proportion of time the walrus spent in the water, and varied among regions (regional mean angles ranged from 40° to 81° and mean displacements ranged from 15 to 35 km). Our results indicated a lack of correspondence between walruses and their initially associated ice floes, suggesting that local areas of walrus activities were independent of the movement of ice floes.

  5. Sources and distribution of sedimentary organic matter along the northern Bering and Chukchi Seas.

    PubMed

    Xu, Fanglu; Jin, Haiyan; Ji, Zhongqiang; Chen, Jianfang; Loh, Pei Sun

    2017-02-01

    In this study, lignin-derived phenols were used to determine the sources and distribution of sedimentary organic matter along the northern Bering Sea and Chukchi Sea of the Arctic Ocean. The lignin parameter syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ratios are used to indicate vegetation sources; and the ratios of vanillic acid/vanillin, (Ad/Al)v and syringic acid/syringaldehyde, (Ad/Al)s are used as indicators of lignin diagenesis. Results showed the predominance of woody gymnosperm signal at the easternmost location in the northern Bering Sea, a mixture of refractory non-woody angiosperm and fresher gymnosperm tissues in the Chukchi Sea, and signal of fresher woody gymnosperm tissues in the northernmost locations in the Chukchi Sea. The lignin materials showed gradual increase in decomposition stage during transport along the northern Bering Sea. Hydrodynamic sorting process, which is the retention of coarser materials nearshore and transportation of finer particles farther offshore, most probably occurred along the east coast of the northern Bering Sea. In Chukchi Sea, the non-woody angiosperm tissues could have originated from the Canadian Arctic and gymnosperm tissues could be from the Russian Arctic side. The fresher materials in the northernmost Chukchi Sea could have been transported here via the ice-rafting process. Detection of fresh lignin materials and the occurrence of lignin decomposition mean that this region could be sensitive to the impact of climate change.

  6. Geologic evolution of the Bering Sea Komandorksy deep basin

    SciTech Connect

    Bogdanov, N.A.

    1986-07-01

    The deep-water Komandorsky basin is located in the southwestern part of the Bering Sea. On the east, it is separated from the Aleutian basin by the submerged Shirshov Ridge; on the west, it is bordered by structures of the north Kamchatka accretionary prism. The Komandorsky basin is characterized by strongly dissected relief of it acoustic basement, which is overlain by a 1.5 to 2.0-km thick sedimentary cover. The western part of the basin is occupied by a rift zone, which is characterized by modern seismicity and high heat flow. It is considered to be the axial zone of Miocene-Pleistocene spreading. On the north terrace of the Komandorsky island arc, traced active volcanos provide evidence that subduction is occurring under the arc from the north. The spreading rift zone is reflected on the continent in Miocene-Pleistocene volcanic rocks, characterized by typical oceanic tholeiitic composition. The Komandorsky basin formed as a result of spreading during the Maestrichtian. Spreading within the basin occurred during the early and middle Oligocene and the late Miocene. East and west of the spreading axis, accretionary prisms formed. The latter are observed along the western flank of the Shirshov Ridge and on the eastern sides of the Kamchatka Peninsula and Koraginsky Island.

  7. Additions to the avifauna of St Matthew Island, Bering Sea

    USGS Publications Warehouse

    Johnson, James A.; Matsuoka, Steven M.; Ruthrauff, Daniel R.; Litzow, Michael A.; Dementyev, Maksim N.

    2004-01-01

    St. Matthew Island (60°24' N, 172°42' W) is located in the north-central Bering Sea and is renowned for its distinctive Beringian flora and fauna. Because of its central position between the coasts of Russia and Alaska, St. Matthew Island and its nearby satellites, Hall and Pinnacle islands, support a mixture of Palearctic and Nearctic avifaunas. Of special interest to North American ornithologists are the numerous Eurasian bird species that visit the islands each spring and fall. Winker et al. (2002) published the first comprehensive summary of bird records for the 125 species detected on St. Matthew Island from 1899 to 1997. Because of its remote location, however, St. Matthew Island is seldom visited, and the island's avifauna remains poorly described.As part of an island-wide systematic survey for Rock Sandpipers (Calidris ptilocnemis) and McKay's Buntings (Plectrophenax hyperboreus), our crew of five ornithologists was present on St. Matthew Island from 25 May to 9 July 2003. In this paper we provide information for 11 bird species seen for the first time on St. Matthew Island. Phylogenetic sequence and nomenclature follow the American Ornithologists' Union (1998, 2000) and Banks et al. (2002, 2003, 2004). An annotated species list with details of observation is on file at the University of Alaska Museum, Fairbank.

  8. 75 FR 51185 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Rock Sole in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-19

    ... Economic Zone Off Alaska; Reallocation of Rock Sole in the Bering Sea and Aleutian Islands Management Area... of the 2010 rock sole total allowable catch (TAC) specified for the Bering Sea and Aleutian Islands... management area (BSAI). This action is necessary to allow the 2010 total allowable catch of rock sole to...

  9. 75 FR 792 - Fisheries of the Economic Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian Islands AGENCY: National Marine...: Temporary rule; modification of a closure. SUMMARY: NMFS is opening directed fishing for Pacific cod by catcher Pacific cod by catcher/processors using hook-and-line gear in the Bering Sea and Aleutian...

  10. 76 FR 49417 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-10

    ...NMFS proposes regulations that would implement Amendment 93 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). This proposed rule would amend the Bering Sea and Aleutian Islands Amendment 80 Program to modify the criteria for forming and participating in a harvesting cooperative. This action is necessary to encourage greater......

  11. 76 FR 45219 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-28

    ...Amendment 93 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP) would amend the Bering Sea and Aleutian Islands Amendment 80 Program to modify the criteria for forming and participating in a harvesting cooperative. This action is necessary to encourage greater participation in harvesting cooperatives, which enable members to more......

  12. 76 FR 68354 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-04

    ...NMFS issues regulations implementing Amendment 93 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). These regulations amend the Bering Sea and Aleutian Islands Amendment 80 Program to modify the criteria for forming and participating in a harvesting cooperative. This action is necessary to encourage greater participation in harvesting......

  13. 76 FR 44297 - Fisheries of the Exclusive Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-25

    ... Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands King and Tanner Crab Fishery Resources... Fishery Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP) and the CR Program to... the amendment is available for public review and comment. The king and Tanner crab fisheries in...

  14. 76 FR 47493 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands King and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-05

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands King and Tanner Crabs AGENCY: National Marine... economic zone of the Bering Sea and Aleutian Islands are managed under the FMP. The FMP was prepared by the... ecological conditions warrant doing so. Amendment 39 modifies the existing snow crab rebuilding plan...

  15. 78 FR 59908 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-30

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Amendment 99 AGENCY: National... the Bering Sea and Aleutian Islands Management Area (BSAI FMP) to NMFS for review. If approved... review and comment. NMFS manages the U.S. groundfish fisheries of the Exclusive Economic Zone (EEZ)...

  16. 77 FR 44172 - Fisheries of the Exclusive Economic Zone Off Alaska; Squid in the Bering Sea and Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-27

    ... Economic Zone Off Alaska; Squid in the Bering Sea and Aleutian Islands Management Area AGENCY: National... non-specified reserve to the initial total allowable catch of squid in the Bering Sea and Aleutian... 679. The 2012 initial total allowable catch (ITAC) of squid in the BSAI was established as 361...

  17. 76 FR 59924 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-28

    ... Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands Management Area AGENCY: National...: Temporary rule; closure. SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian... sharks in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska local time (A.l.t.), September...

  18. 78 FR 57097 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-17

    ... Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands Management Area AGENCY: National...: Temporary rule; closure. SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian... sharks in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska local time (A.l.t.), September...

  19. 50 CFR 600.1106 - Longline catcher processor subsector Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish species fee payment and collection system... AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS Specific... Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish species fee payment and collection...

  20. 50 CFR 600.1105 - Longline catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Longline catcher processor subsector of... Capacity Reduction Regulations § 600.1105 Longline catcher processor subsector of the Bering Sea and... catcher processor subsector of the Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish...

  1. 76 FR 43658 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-21

    ... Alaska; Bering Sea and Aleutian Islands Crab Rationalization Cost Recovery Program AGENCY: National... under the Bering Sea and Aleutian Islands Crab Rationalization Program. This action is intended to provide holders of crab allocations with the fee percentage for the 2011/2012 crab fishing year so...

  2. 76 FR 81876 - Fisheries of the Exclusive Economic Zone Off Alaska; Inseason Adjustment to the 2012 Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-29

    ... 2012 total allowable catch (TAC) amount for the Bering Sea pollock fishery. This action is necessary because NMFS has determined this TAC is incorrectly ] specified. This action will ensure the Bering Sea pollock TAC is the appropriate amount based on the best available scientific information for pollock...

  3. 76 FR 466 - Fisheries of the Exclusive Economic Zone Off Alaska; Inseason Adjustment to the 2011 Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-05

    ... 2011 total allowable catch (TAC) amount for the Bering Sea pollock fishery. This action is necessary because NMFS has determined this TAC is incorrectly specified. This action will ensure the Bering Sea pollock TAC is the appropriate amount based on the best available scientific information for pollock...

  4. 50 CFR Figure 10 to Part 679 - Pribilof Islands Area Habitat Conservation Zone in the Bering Sea

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Pribilof Islands Area Habitat Conservation Zone in the Bering Sea 10 Figure 10 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Habitat Conservation Zone in the Bering Sea ER15NO99.008...

  5. 50 CFR Figure 10 to Part 679 - Pribilof Islands Area Habitat Conservation Zone in the Bering Sea

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Pribilof Islands Area Habitat Conservation Zone in the Bering Sea 10 Figure 10 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Habitat Conservation Zone in the Bering Sea ER15NO99.008...

  6. 50 CFR Figure 17 to Part 679 - Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA)

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA) 17 Figure 17 to part 679 Wildlife and Fisheries... 679—Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area...

  7. 50 CFR Figure 17 to Part 679 - Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA)

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA) 17 Figure 17 to part 679 Wildlife and Fisheries... 679—Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area...

  8. 50 CFR Figure 17 to Part 679 - Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA)

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA) 17 Figure 17 to part 679 Wildlife and Fisheries... 679—Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area...

  9. 50 CFR Figure 10 to Part 679 - Pribilof Islands Area Habitat Conservation Zone in the Bering Sea

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Pribilof Islands Area Habitat Conservation Zone in the Bering Sea 10 Figure 10 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Habitat Conservation Zone in the Bering Sea ER15NO99.008...

  10. 50 CFR Figure 10 to Part 679 - Pribilof Islands Area Habitat Conservation Zone in the Bering Sea

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Pribilof Islands Area Habitat Conservation Zone in the Bering Sea 10 Figure 10 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Habitat Conservation Zone in the Bering Sea ER15NO99.008...

  11. 50 CFR Figure 17 to Part 679 - Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA)

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area (HCA) 17 Figure 17 to part 679 Wildlife and Fisheries... 679—Northern Bering Sea Research Area and Saint Lawrence Island Habitat Conservation Area...

  12. 50 CFR Figure 10 to Part 679 - Pribilof Islands Area Habitat Conservation Zone in the Bering Sea

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Pribilof Islands Area Habitat Conservation Zone in the Bering Sea 10 Figure 10 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Habitat Conservation Zone in the Bering Sea ER15NO99.008...

  13. 76 FR 33171 - Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-08

    ... Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY... Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to prevent exceeding the 2011 Alaska plaice total allowable catch (TAC) specified for the BSAI. DATES: Effective 1200...

  14. 75 FR 55288 - Fisheries of the Exclusive Economic Zone Off Alaska; Northern Rockfish in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-10

    ... Economic Zone Off Alaska; Northern Rockfish in the Bering Sea and Aleutian Islands Management Area AGENCY... rockfish in the Bering Sea and Aleutian Islands Management Area (BSAI). This action is necessary to fully use the 2010 total allowable catch (TAC) of northern rockfish in the BSAI. DATES: Effective 1200...

  15. 76 FR 33172 - Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-08

    ... Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY... of the non-specified reserve to the initial total allowable catch of Alaska plaice in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to allow the fisheries...

  16. 76 FR 76902 - Fisheries of the Exclusive Economic Zone Off Alaska; Sculpins in the Bering Sea Subarea of the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-09

    ... Management Area AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric...: NMFS apportions amounts of the non-specified reserve to the initial total allowable catch of sculpins in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This action...

  17. 78 FR 24361 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Bering Sea Subarea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-25

    ... Management Area AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric... for Greenland turbot in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to prevent exceeding the 2013 Greenland turbot initial total...

  18. 78 FR 42891 - Fisheries of the Exclusive Economic Zone Off Alaska; Rougheye Rockfish in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-18

    ... management area (BSAI). This action is necessary because the 2013 total allowable catch of rougheye rockfish... Economic Zone Off Alaska; Rougheye Rockfish in the Bering Sea and Aleutian Islands Management Area AGENCY... economic zone according to the Fishery Management Plan for Groundfish of the Bering Sea and...

  19. 76 FR 55276 - Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian Islands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-07

    ... Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian Islands AGENCY: National Marine Fisheries...; closure. SUMMARY: NMFS is prohibiting retention of octopus in the Bering Sea and Aleutian Islands (BSAI). This action is necessary because the 2011 total allowable catch of octopus in the BSAI has been...

  20. 78 FR 42023 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-15

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY... mackerel in the Central Aleutian district (CAI) of the Bering Sea and Aleutian Islands Management Area... fully use the 2013 total allowable catch (TAC) of Atka mackerel in the CAI by vessels participating...

  1. Changes in C37 alkenones flux on the eastern continental shelf of the Bering Sea: the record of Emiliania huxleyi bloom over the past 100 years

    NASA Astrophysics Data System (ADS)

    Harada, N.; Sato, M.; Okazaki, Y.; Oguri, K.; Tadai, O.; Saito, S.; Konno, S.; Jordan, R. W.; Katsuki, K.; Shin, K.; Narita, H.

    2008-12-01

    Flourishes of coccolithophores can be detected by ocean color imagery with data from the satellite-borne Sea-viewing Wide Field-of-view sensor SeaWiFs that was launched in 1997. Thus, temporally and spatially large-scale blooms of Emiliania huxleyi (E. huxleyi) have been distinguished annually in the eastern continental shelf of the Bering Sea since 1997. In 1997, a combination of atmospheric mechanisms produced summer weather anomalies such as calm winds, clear skies, and warm air temperature over the Bering Sea and the weather anomalies caused depletion of the subpycnocline nutrient reservoir (Napp and Hunt, 2001). After depletion of nitrate and silicate, a sustained (more than 4-month-long) bloom of E. huxleyi was observed (Stockwell et al., 2001). Because of the speed and magnitude with which parts of the Bering Sea ecosystem responded to changes in atmospheric factors (Napp and Hunt, 2001) and because a bloom of the coccolithophorid, Coccolithus pelagicus has also been detected in the northeastern Atlantic Ocean off Iceland every year since 1997 (Ostermann, 2001), the appearance of an E. huxleyi bloom in the Bering Sea could be related to atmospherically forced decadal oscillations or global factors. We have investigated spatial expansion and temporal development of E. huxleyi bloom on the continental shelf in the Bering Sea by using a biomarker of E. huxleyi, C37 alkenones flux recorded in the sediments during the past 100 years. As a result, the E. huxleyi bloom had been prominent since 1970"fs at latest during the last 100 years. In this presentation, we will discuss the relationship between E. huxleyi bloom and activity of Aleutian low, and also changes in diatom assemblages. References Napp and Hunt, 2001, Fish Oceanogr., 10, 61-68. Ostermann, 2001, WHOI annual report, pp.17-18. Stockwell et al., 2001, Fish Oceanogr., 10, 99-116.

  2. Millennial environmental variability on Shirshov Ridge, Bering Sea, during the penultimate and last glacial cycles

    NASA Astrophysics Data System (ADS)

    Ivanova, E.; Ovsepyan, E.; Murdmaa, I.; Max, L.; Riethdorf, J.; Nuernberg, D.; Tiedemann, R.; Alekseeva, T.

    2011-12-01

    Changes in paleoceanographic conditions on Shirshov Ridge, Western Bering Sea, are inferred over the last two glacial cycles from the high-resolution study of planktic and benthic foraminiferal assemblages and IRD from the upper and lower parts of an 18m-long piston core SO201-2-85KL (57°30.30'N, 170°24.79'E, water depth 968 m). Here we present evidence of pronounced glacial-interglacial and millennial-scale variations in surface biological productivity, bottom-water ventilation and ice rafting. Along with strong dominance of siliceous microfossils during MIS 1 and MIS 5.5, the interglacial sediments contain diverse benthic foraminiferal assemblages whereas planktic foraminifers are scarce due to selective dissolution. In contrast, the glacials are characterized by strong terrigenous input, including the IRD transported by sea ice and icebergs, and by moderate productivity with the seasonal pulses indicated by the high content of benthic opportunistic species Alabaminella weddellensis. Factor analyses of the benthic fauna clearly show a remarkable difference between glacial assemblages and interglacial fauna which is strongly dominated by Bolivina seminuda and Bulimina tenuata. These species are known to favor rather stable high-productivity conditions with enhanced supply of organic matter to the sediments and decreased oxygen content. Reduced ventilation during the interglacials is also evidenced by high values of the dysoxic benthic group whereas the oxic group is the most abundant during the last glacial. Low-diversity planktic foraminiferal assemblages dominated by the polar species Neogloboquadrina pachyderma sin. indicating a generally cold surface-water layer characterize both glacial-interglacial cycles. However, the intervals with high relative abundance of Globigerina bulloides point to an increase in surface bioproductivity on a millennial scale. In particular, these increases occur at the glacial terminations and are compatible with spikes in

  3. Bowers Swell: Evidence for a zone of compressive deformation concentric with Bowers Ridge, Bering Sea

    USGS Publications Warehouse

    Marlow, M. S.; Cooper, A. K.; Dadisman, S.V.; Geist, E.L.; Carlson, P.R.

    1990-01-01

    Bowers Swell is a newly discovered bathymetric feature which is up to 90 m high, between 12 and 20 km wide, and which extends arcuately about 400 km along the northern and eastern sides of Bowers Ridge. The swell was first revealed on GLORIA sonographs and subsequently mapped on seismic reflection and 3.5 kHz bathymetric profiles. These geophysical data show that the swell caps an arcuate anticlinal ridge, which is composed of deformed strata in an ancient trench on the northern and eastern sides of Bowers Ridge. The trench fill beneath the swell is actively deforming, as shown by faulting of the sea floor and by thinning of the strata across the crest of the swell. Thinning and faulting of the trench strata preclude an origin for the swell by simple sediment draping over an older basement high. We considered several models for the origin of Bowers Swell, including folding and uplift of the underlying trench sediment during the interaction between the Pacific plate beneath the Aleutian Ridge and a remnant oceanic slab beneath Bowers Ridge. However, such plate motions should generate extensive seismicity beneath Bowers Ridge, which is aseismic, and refraction data do not show any remnant slab beneath Bowers Ridge. Another origin considered for Bowers Swell invokes sediment deformation resulting from differential loading and diapirism in the trench fill. However, diapirism is not evident on seismic reflection profiles across the swell. We favour a model in which sediment deformation and swell formation resulted from a few tens of kilometers of low seismicity motion by intraplate crustal blocks beneath the Aleutian Basin. This motion may result from the translation of blocks in western Alaska to the south-west, forcing the movement of the Bering Sea margin west of Alaska into the abyssal Aleutian Basin. ?? 1990.

  4. Condition of groundfish resources of the eastern Bering Sea and Aleutian Islands region in 1982

    SciTech Connect

    Bakkala, R.G.; Low, L.; Ito, D.H.; Narita, R.E.; Ronholt, L.L.

    1983-03-01

    This report contains an assessment of the condition of groundfish and squid in the eastern Bering Sea and Aleutian Islands region through 1982. The assessments are based on species-by-species analyses of the data collected from the commercial fishery and research vessel surveys. Most of the resources in the Bering Sea-Aleutians management region are in good condition, including walleye pollock, Pacific cod, the flatfishes, and Atka mackerel. Pacific cod and yellowfin sole are in excellent condition and at historic high levels of abundance.

  5. Is the Climate of Bering Sea Warming and Affecting the Ecosystem?

    NASA Astrophysics Data System (ADS)

    Overland, James E.; Stabeno, Phyllis J.

    2004-08-01

    Observations from the Bering Sea are good indicators of decadal shifts in climate, as the Bering is a transition region between the cold, dry Arctic air mass to the north, and the moist, relatively warm maritime air mass to the south. The Bering Sea is also a transition region between Arctic and sub-Arctic ecosystems; this boundary can be loosely identified with the extent of winter sea-ice cover. Like a similar transition zone in the eastern North Atlantic, the Bering Sea is experiencing a northward biogeographical shift in response to changing temperature and atmospheric forcing. If this shift continues over the next decade, it will have major impacts on commercial and subsistence harvests as Arctic species are displaced by sub-Arctic species. The stakes are enormous, as this rich and diverse ecosystem currently provides 47% of the U.S. fishery production by weight, and is home to 80% of the U.S. sea bird population, 95% of northern fur seals, and major populations of Steller sea lions, walrus, and whales.

  6. Bering Sea records of climate and North Pacific Intermediate Water ventilation

    NASA Astrophysics Data System (ADS)

    Knudson, K. P.; Ravelo, A. C.

    2012-12-01

    Although much progress has been made in understanding the links between high-latitude paleoclimate and circulation in the North Atlantic, the relationship is poorly understood in the North Pacific. Some work has speculated that North Pacific climate on glacial-interglacial (G/IG) cycles is related to fluctuations in the prominence of North Pacific Intermediate Water (NPIW), based on evidence from data from short cores that shows increased ventilation during the Last Glacial Maximum. However, changes in North Pacific ventilation have not been evaluated on timescales long enough to validate this theory linking climate and NPIW production. New Bering Sea cores from Integrated Ocean Drilling Program Expedition 323 Site U1342, located within the present-day oxygen minimum zone (OMZ), contain alternating laminated and massive bioturbated sediments that may indicate changes in intensity and depth in the OMZ in response to variations in intermediate water ventilation and surface productivity. Here we show preliminary results from Site U1342 that evaluate changes in climate and Bering Sea ocean circulation over multiple glacial-interglacial cycles. δ13C and δ18O records from benthic foraminifera Uvigerina perigrina and δ15N of bulk sediment are compared to occurrences of laminated intervals over the past 800 kyr. During interglacials, much lighter benthic δ13C values at U1342 relative to deep Pacific site 849 indicate an older water mass at U1342, whereas similar benthic δ13C values at sites 849 and U1342 during glacials provide evidence for increased ventilation. Although laminated intervals, which are indicative of the most extreme reductions in oxygenation, occur more frequently during interglacial times, they are not strongly correlated to benthic δ13C and δ18O fluctuations. δ15N of bulk sediment, which may indicate changes in either denitrification and/or nutrient utilization, display little relationship to the G/IG intervals and display positive peaks in some

  7. Linkages between sea-ice coverage, pelagic-benthic coupling, and the distribution of spectacled eiders: observations in March 2008, 2009 and 2010, northern Bering Sea

    USGS Publications Warehouse

    Cooper, L.W.; Sexson, M.G.; Grebmeier, J.M.; Gradinger, R.; Mordy, C.W.; Lovvorn, J.R.

    2013-01-01

    Icebreaker-based sampling in the northern Bering Sea south of St. Lawrence Island in March of 2008, 2009, and 2010 has provided new data on overall ecosystem function early in the annual productive cycle. While water-column chlorophyll concentrations (−2 integrated over the whole water column) are two orders of magnitude lower than observed during the spring bloom in May, sea-ice algal inventories of chlorophyll are high (up to 1 g m−3 in the bottom 2-cm of sea-ice). Vertical fluxes of chlorophyll as measured in sediment traps were between 0.3 to 3.7 mg m−2 d−1 and were consistent with the recent deposition (days to weeks time scale) of chlorophyll to the surface sediments (0–25 mg m−2 present at 0–1 cm). Sediment oxygen respiration rates were lower than previous measurements that followed the spring bloom, but were highest in areas of known high benthic biomass. Early spring release of sedimentary ammonium occurs, particularly southeast of St. Lawrence Island, leading to bottom-water ammonium concentrations of >5 µM. These data, together with other physical, biological, and nutrient data are presented here in conjunction with observed sea-ice dynamics and the distribution of an apex predator, the Spectacled Eider (Somateria fischeri). Sea-ice dynamics in addition to benthic food availability, as determined by sedimentation processes, play a role in the distribution of spectacled eiders, which cannot always access the greatest biomass of their preferred bivalve prey. Overall, the data and observations indicate that the northern Bering Sea is biologically active in late winter, but with strong atmospheric and hydrographic controls. These controls pre-determine nutrient and chlorophyll distributions, water-column mixing, as well as pelagic-benthic coupling.

  8. Biogeochemical cycling in the Bering Sea over the onset of major Northern Hemisphere Glaciation

    NASA Astrophysics Data System (ADS)

    Swann, George E. A.; Snelling, Andrea M.; Pike, Jennifer

    2016-09-01

    The Bering Sea is one of the most biologically productive regions in the marine system and plays a key role in regulating the flow of waters to the Arctic Ocean and into the subarctic North Pacific Ocean. Cores from Integrated Ocean Drilling Program (IODP) Expedition 323 to the Bering Sea provide the first opportunity to obtain reconstructions from the region that extend back to the Pliocene. Previous research at Bowers Ridge, south Bering Sea, has revealed stable levels of siliceous productivity over the onset of major Northern Hemisphere Glaciation (NHG) (circa 2.85-2.73 Ma). However, diatom silica isotope records of oxygen (δ18Odiatom) and silicon (δ30Sidiatom) presented here demonstrate that this interval was associated with a progressive increase in the supply of silicic acid to the region, superimposed on shift to a more dynamic environment characterized by colder temperatures and increased sea ice. This concluded at 2.58 Ma with a sharp increase in diatom productivity, further increases in photic zone nutrient availability and a permanent shift to colder sea surface conditions. These transitions are suggested to reflect a gradually more intense nutrient leakage from the subarctic northwest Pacific Ocean, with increases in productivity further aided by increased sea ice- and wind-driven mixing in the Bering Sea. In suggesting a linkage in biogeochemical cycling between the south Bering Sea and subarctic Northwest Pacific Ocean, mainly via the Kamchatka Strait, this work highlights the need to consider the interconnectivity of these two systems when future reconstructions are carried out in the region.

  9. Distribution of dissolved organic matter in the eastern Bering Sea, Chukchi Sea (Barrow Canyon) and Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Shin, Kyung-Hoon; Tanaka, Noriyuki

    2004-12-01

    The distribution of dissolved organic carbon (DOC) in the western Arctic Ocean is greatly influenced by conservative riverine DOC flux into the northern Bering Sea, Bering Strait and Beaufort Sea, as indicated by an inverse correlation with salinity. Based on the relations between DOC, salinity and seawater temperature, several water masses could be identified. These included riverine water, ice-melt water, surface mixed water, cold and saline shelf water, and Atlantic Ocean water. High concentrations of chlorophyll a and DOC were found in some parcels of dense shelf water in Barrow Canyon. In addition, labile DOC compounds, such as polyunsaturated fatty acids (PUFA), were found in the dense shelf water, suggesting the dense shelf water contains a product (marine organic matter) of the biological CO2 pump.

  10. A Pliocene to recent history of the Bering Sea at Site U1340A, IODP Expedition 323

    NASA Astrophysics Data System (ADS)

    Stroynowski, Zuzia; Ravelo, Anna Christina; Andreasen, Dyke

    2015-12-01

    Fossil diatoms are the principal component of Bering Sea sediments and reflect the paleoceanographic history of the region. Diatom accumulation rates and relative abundances at International Ocean Discovery Program (IODP) Site U1340A are presented. Overall, the total diatom productivity record from 4.9 Ma to the present day reveals a fourfold reduction at circa 4.2 Ma from ~45 × 107 down to 11 × 107 valves/g (wet sediment), signifying a major shift in the upwelling and/or nutrient regime, coinciding with the end of the late Miocene-early Pliocene bloom identified in the eastern equatorial Pacific and California margin. Further abrupt shifts in the diatom assemblage occur at (1) 2.78-2.55 Ma, (2) 2.0-1.8 Ma, and (3) 1.0-0.88 Ma. (1) At 2.78-2.55 Ma, the appearance of sea ice-related species marks the regional cooling associated with the expansion of Northern Hemisphere ice sheets, subsequent development of stratified, nutrient-depleted waters, and increased influence of Western Basin Water masses (most likely due to the suppressed inflow of the Alaskan Stream). (2) Rapid cooling between 2.0 and 1.8 Ma indicates increased sea ice duration and/or frequency. This, coupled with low sea level stands caused prolonged closure of the Aleutian Passes, coupled with further increased Western Basin Water inflow. (3) The shift to 100 ka glacial/interglacial cycles at the middle-Pleistocene transition (1.0-0.88 Ma) marked an increase in upwelling-related species, indicating enhanced surface water mixing. These records confirm that the development and changing dynamics of sea ice in the Bering Sea played a major role in sub-Arctic Ocean circulation and is an integral component of global climate change.

  11. Late Quaternary Provenance and Flow Regime Reconstruction through Sedimentologic and Geochemical Evidence from the Bering/Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Pelto, B. M.; Brigham-Grette, J.; Kocis, J. J.; Petsch, S.

    2013-12-01

    The last 20 kyr have been marked by great changes in the Arctic, as the Laurentide Ice Sheet melted and led to the submergence of the Bering Land Bridge and the re-opening of the Bering Strait (BS). The BS is a narrow connection (about 85 km wide) between the Arctic and Pacific Oceans averaging less than 50 m in depth, with present-day flow of seawater northward through the BS, from the Pacific to the Arctic. This flow is of vital importance to global ocean circulation through its role in formation and stability of North Atlantic Deep Water (NADW). An open BS is believed to speed dispersal of North Atlantic freshwater anomalies, both by keeping thermohaline circulation strong, and through reversals of flow through the BS when the North Atlantic is hosed with freshwater. When the BS is closed, these anomalies cannot efficiently dissipate and thermohaline circulation is weakened, which is considered a factor in climate perturbations outside of orbital forcing. Given the period of flux and transition in the Arctic following the Last Glacial Maximum (LGM), the paleoceanographic history of the Bering and Chukchi Seas post-LGM, is important to an understanding of Arctic Ocean circulation, and consequent climate impacts. Today the Arctic is in a period of rapid change, multi-year sea ice is disappearing, and the continuation of climatic stability of the Holocene appears to be at an end. Comprehension of the functioning of the Arctic as a dynamic system is essential to predict future response of the system to change, such as seawater salinity-density changes, lowered sea and land albedo, and rising temperatures. Changes in BS throughflow intensity and direction during deglaciation and submergence of the Bering Land Bridge are proposed and supported in modeling simulations, and are thought to occur during millennial-scale climate changes. We have conducted a coupled sedimentological and geochemical investigation of a suite of marine sediment cores from the Bering and

  12. From the Pacific to the Arctic: Paleoclimatic History of the Gulf of Alaska and the Bering Sea (Invited)

    NASA Astrophysics Data System (ADS)

    Mix, A. C.; Davies, M. H.; Praetorius, S.; Cook, M. S.; Prahl, F. G.; Schmittner, A.; Asahi, H.; Belanger, C. L.; Stoner, J. S.; St-Onge, G.; Jaeger, J. M.; Gulick, S. P.

    2013-12-01

    The Pacific Gateway to the Arctic, ranging from the high North Pacific through the Bering Sea and Bering Strait, remains among the poorest known components of the global climate system; its paleoclimate record is undersampled, misunderstood, and filled with controversy. We know relatively little about the history of Cordilleran ice beyond the last deglaciation; there are vigorous disagreements about the sign, let alone the magnitude, of sea-surface temperate changes and sea-ice cover. The causes of subsurface ocean change and linkages to surface climate are debated, and various models disagree on many aspects. This region is a sensitive part of the climate system, potentially poised near a threshold and with the power to influence North American and global heat and moisture transports through its influence on westerly winds and planetary waves. Little deep or intermediate water forms here today due to excess freshwater input relative to evaporation, but this may have changed in the past, with major consequences for oceanic heat transports, chemical budgets, and the global carbon cycle. Here we compare the records from the Gulf of Alaska and the Bering Sea from the sea surface to the abyss. The Gulf of Alaska, recently drilled by IODP Expedition 341, is dominated by massive input of terrigenous sediments, freshwater flows off the continent that fuels a vigorous coastal current, and boundary downwelling adjacent to the iron-limited subpolar gyre. This region offers a high-resolution view of dynamic advances and retreats of the seaward outlets of Cordilleran Ice Sheet; isostatic responses of the shelf to ice loading reduces the local influence of global sealevel sealevel. In contrast, the Bering Sea, drilled in 2009 by IODP Expedition 323, is a relatively isolated basin, highly biogenic in character, and displays a response to global sealevel change relative to its mostly unglaciated shelf and intermittent subaerial exposure of Beringia, with more frequent intervals

  13. Genetic stock identification of immature chum salmon ( Oncorhynchus keta) in the western Bering Sea, 2004

    NASA Astrophysics Data System (ADS)

    Kang, Minho; Kim, Suam; Low, Loh-Lee

    2016-03-01

    Genetic stock identification studies have been widely applied to Pacific salmon species to estimate stock composition of complex mixed-stock fisheries. In a September-October 2004 survey, 739 chum salmon ( Oncorhynchus keta) specimens were collected from 23 stations in the western Bering Sea. We determined the genetic stock composition of immature chum salmon based on the previous mitochondria DNA baseline. Each regional estimate was computed based on the conditional maximum likelihood method using 1,000 bootstrap resampling and then pooled to the major regional groups: Korea - Japan - Primorie (KJP) / Russia (RU) / Northwest Alaska (NWA) / Alaska Peninsula - Southcentral Alaska - Southeast Alaska - British Columbia - Washington (ONA). The stock composition of immature chum salmon in the western Bering Sea was a mix of 0.424 KJP, 0.421 RU, 0.116 NWA, and 0.039 ONA stocks. During the study period, the contribution of Asian chum salmon stocks gradually changed from RU to KJP stock. In addition, North American populations from NWA and ONA were small but present near the vicinity of the Russian coast and the Commander Islands, suggesting that the study areas in the western Bering Sea were an important migration route for Pacific chum salmon originating both from Asia and North America during the months of September and October. These results make it possible to better understand the chum salmon stock composition of the mixed-stock fisheries in the western Bering Sea and the stock-specific distribution pattern of chum salmon on the high-seas.

  14. Arctic sea ice decline: Projected changes in timing and extent of sea ice in the Bering and Chukchi Seas

    USGS Publications Warehouse

    Douglas, D.C.

    2010-01-01

    The Arctic region is warming faster than most regions of the world due in part to increasing greenhouse gases and positive feedbacks associated with the loss of snow and ice cover. One consequence has been a rapid decline in Arctic sea ice over the past 3 decades?a decline that is projected to continue by state-of-the-art models. Many stakeholders are therefore interested in how global warming may change the timing and extent of sea ice Arctic-wide, and for specific regions. To inform the public and decision makers of anticipated environmental changes, scientists are striving to better understand how sea ice influences ecosystem structure, local weather, and global climate. Here, projected changes in the Bering and Chukchi Seas are examined because sea ice influences the presence of, or accessibility to, a variety of local resources of commercial and cultural value. In this study, 21st century sea ice conditions in the Bering and Chukchi Seas are based on projections by 18 general circulation models (GCMs) prepared for the fourth reporting period by the Intergovernmental Panel on Climate Change (IPCC) in 2007. Sea ice projections are analyzed for each of two IPCC greenhouse gas forcing scenarios: the A1B `business as usual? scenario and the A2 scenario that is somewhat more aggressive in its CO2 emissions during the second half of the century. A large spread of uncertainty among projections by all 18 models was constrained by creating model subsets that excluded GCMs that poorly simulated the 1979-2008 satellite record of ice extent and seasonality. At the end of the 21st century (2090-2099), median sea ice projections among all combinations of model ensemble and forcing scenario were qualitatively similar. June is projected to experience the least amount of sea ice loss among all months. For the Chukchi Sea, projections show extensive ice melt during July and ice-free conditions during August, September, and October by the end of the century, with high agreement

  15. Divergent patterns of recent sea ice cover across the Bering, Chukchi, and Beaufort seas of the Pacific Arctic Region

    NASA Astrophysics Data System (ADS)

    Frey, Karen E.; Moore, G. W. K.; Cooper, Lee W.; Grebmeier, Jacqueline M.

    2015-08-01

    Over the past three decades of the observed satellite record, there have been significant changes in sea ice cover across the Bering, Chukchi, and Beaufort seas of the Pacific Arctic Region (PAR). Satellite data reveal that patterns in sea ice cover have been spatially heterogeneous, with significant declines in the Chukchi and Beaufort seas, yet more complex multi-year variability in the Bering Sea south of St. Lawrence Island. These patterns in the Chukchi and Beaufort seas have intensified since 2000, indicating a regime shift in sea ice cover across the northern portion of the PAR. In particular, satellite data over 1979-2012 reveal localized decreases in sea ice presence of up to -1.64 days/year (Canada Basin) and -1.24 days/year (Beaufort Sea), which accelerated to up to -6.57 days/year (Canada Basin) and -12.84 days/year (Beaufort Sea) over the 2000-2012 time period. In contrast, sea ice in the Bering Sea shows more complex multi-year variability with localized increases in sea ice presence of up to +8.41 days/year since 2000. The observed increases in sea ice cover since 2000 in the southern Bering Sea shelf region are observed in wintertime, whereas sea ice losses in the Canada Basin and Beaufort Sea have occurred during summer. We further compare sea ice variability across the region with the National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) wind and air temperature fields to determine the extent to which this recent variability is driven by thermal vs. wind-driven processes. Results suggest that for these localized areas that are experiencing the most rapid shifts in sea ice cover, those in the Beaufort Sea are primarily wind driven, those offshore in the Canada Basin are primarily thermally driven, and those in the Bering Sea are influenced by elements of both. Sea ice variability (and its drivers) across the PAR provides critical insight into the forcing effects of recent shifts in climate and its likely

  16. 75 FR 21600 - Groundfish Fisheries of the Bering Sea and Aleutian Islands Area and the Gulf of Alaska; King and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration RIN 0648-XW07 Groundfish Fisheries of the Bering Sea and Aleutian Islands Area and the Gulf of Alaska; King and Tanner Crab Fisheries in the Bering...

  17. 75 FR 59687 - Proposed Information Collection; Comment Request; Alaska Region Bering Sea & Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-28

    ... Region Bering Sea & Aleutian Islands (BSAI) Crab Economic Data Reports AGENCY: National Oceanic and... communities and monitors the ``economic stability for harvesters, processors, and coastal communities.'' The Magnuson-Stevens Act provides specific guidance on the CR Program's mandatory economic data...

  18. 50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ....1001, (B) Section 600.1002, (C) Section 600.1003, (D) Section 600.1004, (E) Section 600.1005, (F... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Bering Sea and Aleutian Islands (BSAI... and section 205 of Pub. L. 107-117, enacted for BSAI crab species. (b) Terms. Unless otherwise...

  19. 75 FR 5945 - Proposed Information Collection; Comment Request; Alaska Cooperatives in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-05

    ... Fisheries Act (AFA) was signed into law in October of 1998. The AFA established an allocation program for the pollock fishery of the Bering Sea and Aleutian Islands Management Area (BSAI). The AFA established... at 50 CFR part 679, subpart F. The original purposes of the AFA were to tighten United...

  20. Results of the fourth joint U.S.-Russian Bering and Chukchi Seas expedition (BERPAC)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is important to monitor the status of arctic oceans especially in terms of the impact human activities are making on these sensitive ecosystems. This is a compilation of research findings from a joint US/Russian expedition to the Bering and Chukchi seas that focuses on the significance of long-t...

  1. An inverse modeling study of circulation in the Eastern Bering Sea during 2007-2010

    NASA Astrophysics Data System (ADS)

    Panteleev, Gleb; Yaremchuk, Max; Francis, Oceana; Stabeno, Phyllis J.; Weingartner, T.; Zhang, J.

    2016-06-01

    A two-way nested 4d-variational data assimilation system is implemented in the Eastern Bering Sea (EBS) to investigate changes in circulation and thermodynamic state for a 3.8 year period. Assimilated observations include data from 19 moorings deployed on the shelf and in the Bering Strait, 1705 hydrographic stations occupied during eight surveys, and remotely sensed sea surface temperature and sea surface height (SSH) data. Validation of the presented 4dVar reanalysis against the output of two sequential data-assimilative systems (the Bering Ecosystem Study ice-ocean Modeling and Assimilation System (BESTMAS) and the Arctic Cap Nowcast-Forecast System (ACNFS)) has shown that the product is more consistent with the observed transports in the Bering Strait and in the EBS interior both in terms of their magnitude and time variability. Analysis of the data-optimized solution quantifies a sequence of wind-forced events that resulted in the anomalous heat and freshwater transports through the Bering Strait, including a 28 day long flow reversal that occurred in November 2009 and carried Siberian Coastal Current water down to the Gulf of Anadyr. Lagrangian study of the Arctic-bound Pacific waters indicates the extreme importance of the cross-shelf exchange along the path of the Bering Slope Current and quantifies the spectrum of residence times for the waters entering EBS through Unimak Pass and through Aleutian passages. Residence times in the EBS cold pool are diagnosed to be 2-3 times longer than those in the surrounding waters.

  2. Radiocesium in the western subarctic area of the North Pacific Ocean, Bering Sea, and Arctic Ocean in 2013 and 2014.

    PubMed

    Kumamoto, Yuichiro; Aoyama, Michio; Hamajima, Yasunori; Nishino, Shigeto; Murata, Akihiko; Kikuchi, Takashi

    2017-02-27

    We measured radiocesium ((134)Cs and (137)Cs) in seawater from the western subarctic area of the North Pacific Ocean, Bering Sea, and Arctic Ocean in 2013 and 2014. Fukushima-derived (134)Cs in surface seawater was observed in the western subarctic area and Bering Sea but not in the Arctic Ocean. Vertical profile of (134)Cs in the Canada Basin of the Arctic Ocean implies that Fukushima-derived (134)Cs intruded into the basin from the Bering Sea through subsurface (150m depth) in 2014.

  3. 77 FR 62482 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-15

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Groundfish Retention Standard... (BSAI) management area by removing certain regulatory requirements mandating minimum levels of... Fishery Conservation and Management Act, the fishery management plan, and other applicable law....

  4. The Bering Sea: Communication with the Western Subarctic Gyre, Mesoscale Activity, Shelf-Basin Exchange, and the Flow Through Bering Strait

    DTIC Science & Technology

    2011-03-01

    results including: Jaromir Jakacki, Steve Okkonen, Robert Osinski, Waldemar Walczowski , Andrew Roberts, Jacqueline Grebmeier, Lee Cooper, Yvegeny... Walczowski W. (2005) Ocean circulation and exchanges through the northern Bering Sea–1979–2001 model results. Deep-Sea Research II 52:3509–3540. doi

  5. Plio-Pleistocene biostratigraphy and surface water masses in the Bering Sea: planktonic foraminiferal evidence from IODP Site U1340 and Site U1343

    NASA Astrophysics Data System (ADS)

    Husum, Katrine

    2015-04-01

    The Pliocene - Pleistocene evolution of surface water masses in the Bering Sea is not well understood, and the aim of this study is to establish a Plio-Pleistocene planktonic foraminiferal biostratigraphy for the Bering Sea and investigate changes of the surface water circulation. The Bering Sea is a marginal sea of the North Pacific connected to the Arctic Ocean through the Bering Strait providing the only connection and exchange of waters between the Pacific and Atlantic Oceans in the Northern Hemisphere. IODP Site U1340 and Site U1343 in the Bering Sea have been investigated with regard to planktonic foraminifers and fragmentation. The base of Site U1340 dates back to the Early Pliocene and the base of Site U1343 to the Early Pleistocene. Site U1340 is situated at Bowers Ridge, southern Bering Sea, under the axis of the Alaskan Stream transporting warm water into the Bering Sea. Site U1343, is situated near to the gateway to the Arctic Ocean in the northern Bering Sea. At both sites there are none or very few planktonic foraminifers during the Pliocene and early Pleistocene. After 1.3-1.4 Ma the planktonic foraminifers are continuously present for most of the samples examined. Three stratigraphic events have been identified in this study: 1) the first occurrence (FO) of Neogloboquadrina inglei is observed at 1.4 - 1.5 Ma, 2) the change in the coiling ratio of Neogloboquadrina pachyderma from right to left at 1.2 Ma, and 3) the last occurrence (LO) of N. inglei at 0.7 Ma. The oldest event may be affected by poor preservation of foraminifers in older sediments. However, the ages of the latter two events seem to agree with the dating of the same events at the Californian margin observed by Kucera and Kennett (2000) implying that these events are robust regional events for the entire northern Pacific. Multivariate analyses of the quantitative planktonic foraminifer data show three main faunal assemblages. The oldest assemblage from 1.3 - 1.4 Ma to 1.2 Ma is

  6. Radiocarbon evidence of mid-Holocene mammoths stranded on an Alaskan Bering Sea island.

    PubMed

    Guthrie, R Dale

    2004-06-17

    Island colonization and subsequent dwarfing of Pleistocene proboscideans is one of the more dramatic evolutionary and ecological occurrences, especially in situations where island populations survived end-Pleistocene extinctions whereas those on the nearby mainland did not. For example, Holocene mammoths have been dated from Wrangel Island in northern Russia. In most of these cases, few details are available about the dynamics of how island colonization and extinction occurred. As part of a large radiocarbon dating project of Alaskan mammoth fossils, I addressed this question by including mammoth specimens from Bering Sea islands known to have formed during the end-Pleistocene sea transgression. One date of 7,908 +/- 100 yr bp (radiocarbon years before present) established the presence of Holocene mammoths on St Paul Island, a first Holocene island record for the Americas. Four lines of evidence--265 accelerator mass spectrometer (AMS) radiocarbon dates from Alaskan mainland mammoths, 13 new dates from Alaskan island mammoths, recent reconstructions of bathymetric plots and sea transgression rates from the Bering Sea--made it possible to reconstruct how mammoths became stranded in the Pribilofs and why this apparently did not happen on other Alaskan Bering Sea islands.

  7. Pacific walrus (Odobenus rosmarus divergens) resource selection in the Northern Bering Sea.

    PubMed

    Jay, Chadwick V; Grebmeier, Jacqueline M; Fischbach, Anthony S; McDonald, Trent L; Cooper, Lee W; Hornsby, Fawn

    2014-01-01

    The Pacific walrus is a large benthivore with an annual range extending across the continental shelves of the Bering and Chukchi Seas. We used a discrete choice model to estimate site selection by adult radio-tagged walruses relative to the availability of the caloric biomass of benthic infauna and sea ice concentration in a prominent walrus wintering area in the northern Bering Sea (St. Lawrence Island polynya) in 2006, 2008, and 2009. At least 60% of the total caloric biomass of dominant macroinfauna in the study area was composed of members of the bivalve families Nuculidae, Tellinidae, and Nuculanidae. Model estimates indicated walrus site selection was related most strongly to tellinid bivalve caloric biomass distribution and that walruses selected lower ice concentrations from the mostly high ice concentrations that were available to them (quartiles: 76%, 93%, and 99%). Areas with high average predicted walrus site selection generally coincided with areas of high organic carbon input identified in other studies. Projected decreases in sea ice in the St. Lawrence Island polynya and the potential for a concomitant decline of bivalves in the region could result in a northward shift in the wintering grounds of walruses in the northern Bering Sea.

  8. Pacific Walrus (Odobenus rosmarus divergens) Resource Selection in the Northern Bering Sea

    PubMed Central

    Jay, Chadwick V.; Grebmeier, Jacqueline M.; Fischbach, Anthony S.; McDonald, Trent L.; Cooper, Lee W.; Hornsby, Fawn

    2014-01-01

    The Pacific walrus is a large benthivore with an annual range extending across the continental shelves of the Bering and Chukchi Seas. We used a discrete choice model to estimate site selection by adult radio-tagged walruses relative to the availability of the caloric biomass of benthic infauna and sea ice concentration in a prominent walrus wintering area in the northern Bering Sea (St. Lawrence Island polynya) in 2006, 2008, and 2009. At least 60% of the total caloric biomass of dominant macroinfauna in the study area was composed of members of the bivalve families Nuculidae, Tellinidae, and Nuculanidae. Model estimates indicated walrus site selection was related most strongly to tellinid bivalve caloric biomass distribution and that walruses selected lower ice concentrations from the mostly high ice concentrations that were available to them (quartiles: 76%, 93%, and 99%). Areas with high average predicted walrus site selection generally coincided with areas of high organic carbon input identified in other studies. Projected decreases in sea ice in the St. Lawrence Island polynya and the potential for a concomitant decline of bivalves in the region could result in a northward shift in the wintering grounds of walruses in the northern Bering Sea. PMID:24717979

  9. Pacific walrus (Odobenus rosmarus divergens) resource selection in the northern Bering Sea

    USGS Publications Warehouse

    Jay, Chadwick V.; Grebmeier, Jacqueline M.; Fischbach, Anthony S.; McDonald, Trent L.; Cooper, Lee W.; Hornsby, Fawn

    2014-01-01

    The Pacific walrus is a large benthivore with an annual range extending across the continental shelves of the Bering and Chukchi Seas. We used a discrete choice model to estimate site selection by adult radio-tagged walruses relative to the availability of the caloric biomass of benthic infauna and sea ice concentration in a prominent walrus wintering area in the northern Bering Sea (St. Lawrence Island polynya) in 2006, 2008, and 2009. At least 60% of the total caloric biomass of dominant macroinfauna in the study area was composed of members of the bivalve families Nuculidae, Tellinidae, and Nuculanidae. Model estimates indicated walrus site selection was related most strongly to tellinid bivalve caloric biomass distribution and that walruses selected lower ice concentrations from the mostly high ice concentrations that were available to them (quartiles: 76%, 93%, and 99%). Areas with high average predicted walrus site selection generally coincided with areas of high organic carbon input identified in other studies. Projected decreases in sea ice in the St. Lawrence Island polynya and the potential for a concomitant decline of bivalves in the region could result in a northward shift in the wintering grounds of walruses in the northern Bering Sea.

  10. The application of ERTS imagery to monitoring Arctic sea ice. [mapping ice in Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

    NASA Technical Reports Server (NTRS)

    Barnes, J. C. (Principal Investigator); Bowley, C. J.

    1974-01-01

    The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

  11. A shape and compositional analysis of ice-rafted debris in cores from IODP Expedition 323 in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Dadd, Kelsie; Foley, Kristen

    2016-03-01

    Sediment cores recovered during IODP Expedition 323 in the Bering Sea, northern Pacific, contained numerous ice-rafted debris (IRD) clasts up to 85 mm in length. The physical properties (including roundness and sphericity) of 136 clasts from the working half of the cores, a subsample of the total clast number, were analysed and their composition determined using standard petrographic techniques. After removal of pumice and possible fall-in derived material from the clast population, a total of 86 clasts from the original collection were considered to be IRD. While roundness and sphericity vary greatly in the clast population, the IRD are predominately discoid in shape with oblate/prolate indices typically between -5 and 5. There are four time periods over the approximately 4.5 Ma sample interval, 0.36-0.67 Ma, 0.82-1.06 Ma 1.54-1.77 Ma and >3.28 Ma, where there are no IRD in the sample set for sites of the Bering slope, suggesting that these times may have been ice-free. Most clasts show some rounding and are likely to have spent time on beaches with wave action. Wave action on beaches suggests periods of no ice or only seasonal sea-ice. The low roundness values of other clasts, however, suggest they underwent little working and, therefore, the presence of glaciers or more permanent sea-ice at times in those locations. The abundance of rounded and unfaceted clasts as IRD suggests a lack of large ice sheets in the area during cool periods. Clast composition of the IRD is divided into four broad groups, basalt and andesite, granite and metamorphic, sedimentary, and felsic volcanic. The granite and metamorphic and more mature sedimentary lithologies are most likely derived from the Alaskan continental margin, while the extrusive igneous clasts could be derived from a variety of volcanic sources surrounding the Bering Sea, both emergent now or emergent at times of lower sea level. There is only a poor correlation with IRD abundance and marine isotope stages (MIS) for

  12. The Bering Sea Project Archive: a Prototype for Improved Discovery and Access

    NASA Astrophysics Data System (ADS)

    Stott, D.; Mayernik, M. S.; Daniels, M. D.; Moore, J. A.; Williams, S. F.; Allison, J.

    2015-12-01

    The Bering Sea Project was a research program from 2007 through 2012 that sought to understand the impacts of climate change and dynamic sea ice cover on the eastern Bering Sea ecosystem. More than 100 scientists engaged in field data collection, original research, and ecosystem modeling to link climate, physical oceanography, plankton, fishes, seabirds, marine mammals, humans, traditional knowledge and economic outcomes. Over the six-year period of the program hundreds of multidisciplinary datasets coming from a variety of instrumentation and measurement platforms within thirty-one categories of research were processed and curated by the National Center for Atmospheric Research (NCAR) Earth Observing Laboratory (EOL). For the investigator proposing a field project, the researcher performing synthesis, or the modeler seeking data for verification, the easy discovery and access to the most relevant data is of prime importance. The heterogeneous products of oceanographic field programs such as the Bering Sea Project challenge the ability of researchers to identify which data sets, people, or tools might be relevant to their research, and to understand how certain data, instruments, or methods were used to produce particular results.EOL, as a partner in the NSF funded EarthCollab project, is using linked open data to permit the direct interlinking of information and data across platforms and projects. We are leveraging an existing open-source semantic web application, VIVO, to address connectivity gaps across distributed networks of researchers and resources and identify relevant content, independent of location. We will present our approach in connecting ontologies and integrating them within the VIVO system, using the Bering Sea Project datasets as a case study, and will provide insight into how the geosciences can leverage linked data to produce more coherent methods of information and data discovery across large multi-disciplinary projects.

  13. Climate-mediated changes in zooplankton community structure for the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Eisner, Lisa B.; Napp, Jeffrey M.; Mier, Kathryn L.; Pinchuk, Alexei I.; Andrews, Alexander G.

    2014-11-01

    Zooplankton are critical to energy transfer between higher and lower trophic levels in the eastern Bering Sea ecosystem. Previous studies from the southeastern Bering Sea shelf documented substantial differences in zooplankton taxa in the Middle and Inner Shelf Domains between warm and cold years. Our investigation expands this analysis into the northern Bering Sea and the south Outer Domain, looking at zooplankton community structure during a period of climate-mediated, large-scale change. Elevated air temperatures in the early 2000s resulted in regional warming and low sea-ice extent in the southern shelf whereas the late 2000s were characterized by cold winters, extensive spring sea ice, and a well-developed pool of cold water over the entire Middle Domain. The abundance of large zooplankton taxa such as Calanus spp. (C. marshallae and C. glacialis), and Parasagitta elegans, increased from warm to cold periods, while the abundance of gelatinous zooplankton (Cnidaria) and small taxa decreased. Biomass followed the same trends as abundance, except that the biomass of small taxa in the southeastern Bering Sea remained constant due to changes in abundance of small copepod taxa (increases in Acartia spp. and Pseudocalanus spp. and decreases in Oithona spp.). Statistically significant changes in zooplankton community structure and individual species were greatest in the Middle Domain, but were evident in all shelf domains, and in both the northern and southern portions of the eastern shelf. Changes in community structure did not occur abruptly during the transition from warm to cold, but seemed to begin gradually and build as the influence of the sea ice and cold water temperatures persisted. The change occurred one year earlier in the northern than the southern Middle Shelf. These and previous observations demonstrate that lower trophic levels within the eastern Bering Sea respond to climate-mediated changes on a variety of time scales, including those shorter than

  14. Atmospheric organochlorine pollutants and air-sea exchange of hexachlorocyclohexane in the Bering and Chukchi Seas

    USGS Publications Warehouse

    Hinckley, D.A.; Bidleman, T.F.; Rice, C.P.

    1991-01-01

    Organochlorine pesticides have been found in Arctic fish, marine mammals, birds, and plankton for some time. The lack of local sources and remoteness of the region imply long-range transport and deposition of contaminants into the Arctic from sources to the south. While on the third Soviet-American Joint Ecological Expedition to the Bering and Chukchi Seas (August 1988), high-volume air samples were taken and analyzed for organochlorine pesticides. Hexachlorocyclohexane (HCH), hexachlorobenzene, polychlorinated camphenes, and chlordane (listed in order of abundance, highest to lowest) were quantified. The air-sea gas exchange of HCH was estimated at 18 stations during the cruise. Average alpha-HCH concentrations in concurrent atmosphere and surface water samples were 250 pg m-3 and 2.4 ng L-1, respectively, and average gamma-HCH concentrations were 68 pg m-3 in the atmosphere and 0.6 ng L-1 in surface water. Calculations based on experimentally derived Henry's law constants showed that the surface water was undersaturated with respect to the atmosphere at most stations (alpha-HCH, average 79% saturation; gamma-HCH, average 28% saturation). The flux for alpha-HCH ranged from -47 ng m-2 day-1 (sea to air) to 122 ng m-2 d-1 (air to sea) and averaged 25 ng m-2 d-1 air to sea. All fluxes of gamma-HCH were from air to sea, ranged from 17 to 54 ng m-2 d-1, and averaged 31 ng m-2 d-1.

  15. Atmospheric organochlorine pollutants and air-sea exchange of hexachlorocyclohexane in the Bering and Chukchi Seas

    SciTech Connect

    Hinckley, D.A.; Bidleman, T.F. ); Rice, C.P. )

    1991-04-15

    Organochlorine pesticides have been found in Arctic fish, marine mammals, birds, and plankton for some time. The lack of local sources and remoteness of the region imply long-range transport and deposition of contaminants into the Arctic from sources to the south. While on the third Soviet-American Joint Ecological Expedition to the Bering and Chukchi Seas (August 1988), high-volume air samples were taken and analyzed for organochlorine pesticides. Hexachlorocyclohexane (HCH), hexachlorobenzene, polychlorinated camphenes, and chlordane (listed in order of abundance, highest to lowest) were quantified. The air-sea gas exchange of HCH was estimated at 18 stations during the cruise. Average {alpha}-HCH concentrations in concurrent atmosphere and surface water samples were 250 pg/m{sup 3} and 2.4 ng/l, respectively, and average {gamma}-HCH concentrations were 68 pg/m{sup 3} in the atmosphere and 0.6 ng/l in surface water. Calculations based on experimentally derived Henry's law constants showed that the surface water was undersaturated with respect to the atmosphere at most stations ({alpha}-HCH, average 79% saturation; {gamma}-HCH, average 28% saturation). The flux for {alpha}-HCH ranged from {minus}47 ng/m{sup 2} day (sea to air) to 122 ng/m{sup 2} day (air to sea) and averaged 25 ng/m{sup 2} day air to sea. All fluxes of {gamma}-HCH were from air to sea, ranged from 17 to 54 ng/m{sup 2} day, and averaged 31 ng/m{sup 2} day.

  16. Simulation of phytoplankton distribution and variation in the Bering-Chukchi Sea using a 3-D physical-biological model

    NASA Astrophysics Data System (ADS)

    Hu, Haoguo; Wang, Jia; Liu, Hui; Goes, Joaquim

    2016-06-01

    A three-dimensional physical-biological model has been used to simulate seasonal phytoplankton variations in the Bering and Chukchi Seas with a focus on understanding the physical and biogeochemical mechanisms involved in the formation of the Bering Sea Green Belt (GB) and the Subsurface Chlorophyll Maxima (SCM). Model results suggest that the horizontal distribution of the GB is controlled by a combination of light, temperature, and nutrients. Model results indicated that the SCM, frequently seen below the thermocline, exists because of a rich supply of nutrients and sufficient light. The seasonal onset of phytoplankton blooms is controlled by different factors at different locations in the Bering-Chukchi Sea. In the off-shelf central region of the Bering Sea, phytoplankton blooms are regulated by available light. On the Bering Sea shelf, sea ice through its influence on light and temperature plays a key role in the formation of blooms, whereas in the Chukchi Sea, bloom formation is largely controlled by ambient seawater temperatures. A numerical experiment conducted as part of this study revealed that plankton sinking is important for simulating the vertical distribution of phytoplankton and the seasonal formation of the SCM. An additional numerical experiment revealed that sea ice algae account for 14.3-36.9% of total phytoplankton production during the melting season, and it cannot be ignored when evaluating primary productivity in the Arctic Ocean.

  17. Foods of Spectacled Eiders Somateria fischeri in the Bering Sea, Alaska

    USGS Publications Warehouse

    Petersen, M.R.; Piatt, J.F.; Trust, K.A.

    1998-01-01

    The winter diet of Spectacled Eiders living in marine habitats is known only from two individuals described by Cottam (1939). Here we examine marine diets from 36 stomachs collected near St. Lawrence Island, Bering Sea, Alaska, during May-June in 1987 and 1992. All Spectacled Eiders ate Mollusca, including Gastropoda (snails; frequency of occurrence 20.0%; sole taxon 0.0%) and Bivalvia (bivalves; 80.0%; 48.0%), and Crustacea (barnacles, amphipods and crabs; 30.6%; 0.0%). One bird ate a cod. The predominant species group eaten was Macoma Clams (72.0%; 36.0%). Prey species of Spectacled Eiders occur predominantly in waters 25-60 m deep in the Bering Sea. To obtain these prey, especially the bivalves, on the winter area Spectacled Eiders must forage in waters exceeding 40 m. We speculate that Spectacled Eiders regularly forage at depths of 45-70 m throughout winter.

  18. Ecosystem response to a temporary sea ice retreat in the Bering Sea: Winter 2009

    NASA Astrophysics Data System (ADS)

    Miksis-Olds, Jennifer L.; Stabeno, Phyllis J.; Napp, Jeffery M.; Pinchuk, Alexei I.; Nystuen, Jeffrey A.; Warren, Joseph D.; Denes, Samuel L.

    2013-04-01

    Adding acoustic systems onto ocean moorings and observatories provides additional data to more fully document ecosystem responses to environmental perturbations. A passive acoustic recorder and three-frequency echosounder system were integrated into a biophysical mooring on the central eastern Bering Sea continental shelf. An unexpected, transient, mid-winter retreat of the seasonal sea ice was observed over the mooring for a 2-week period in March 2009. Interpretation of the passive acoustic data provided information about sea ice conditions and included the detection and identification of vocalizing marine mammals, while the acoustic backscatter provided information on relative zooplankton and fish abundance before, during, and after the retreat. Hydrographic data confirmed the acoustic signal was associated with changing surface ice conditions, and the combined information from the biophysical mooring sensors revealed changes in winter trophic level dynamics during the retreat, which would have otherwise been undetected by traditional ship-based observations. Changes in the acoustic environment, zooplankton dynamics, and acoustic detection of marine mammals were observed amidst a physically stable and uniform water column with no indication of a phytoplankton bloom. These data demonstrate the value of acoustic technologies to monitor changing ecosystems dynamics in remote and hazardous locations.

  19. Production and dispersion of dissolved methane in southeastern Bering Sea. Final report

    SciTech Connect

    Cline, J.D.; Kelly-Hansen, K.; Katz, C.N.

    1982-01-01

    The purpose of the study was to use dissolved methane as a tracer of mean circulation and to define vertical and horizontal mixing scales in local regions of the southeastern Bering Sea. The subregions selected for study included St. George Basin, a fault basin located on the outer shelf of Bristol Bay, and the North Aleutian Shelf. Both regions were identified as potential off-shore leasing sites for gas and oil production.

  20. Diets of short-tailed shearwaters in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Hunt, George L.; Baduini, Cheryl; Jahncke, Jaime

    2002-12-01

    In the late 1990s, the southeastern Bering Sea exhibited a number of anomalous conditions, including a major die-off of short-tailed shearwaters ( Puffinus tenuirostris), a trans-equatorial migrant that constitutes a major portion of the marine bird biomass in the southeastern Bering Sea. As part of a larger study of the ecological role of the inner or structural front over the southeastern Bering Sea shelf, in 1997-1999, we collected short-tailed shearwaters to determine diet composition. In spring 1997, we found that short-tailed shearwaters were consuming predominately the euphausiid Thysanoessa raschii, a diet expected on the basis of past studies. However, in subsequent years, short-tailed shearwater diets in spring contained increasingly larger proportions of fish, in particular, sandlance ( Ammodytes hexapterus), as well as other species of euphausiids ( T. inermis in 1999). In summer and fall collections, short-tailed shearwater diets were more varied than in spring, and included both fish (age-0 gadids, 21-35% by weight) and a wider variety of euphausiid species (T. inermis and T. spinifera). In summer and fall, crab zoea (August 1998) and copepods (August 1999) were eaten by shearwaters collected while feeding within the inner front. Diets in 1997-1999 were broader than those found in previous studies of short-tailed shearwaters over the inner shelf and Bristol Bay, which had documented diets composed almost solely of T. raschii. Our data are consistent with the hypothesis that euphausiids were less available to short-tailed shearwaters foraging over the middle and coastal domains of the southeastern Bering Sea in 1997-1999 than has previously been true. Our results are also consistent with hypothesis that the inner front can affect the availability of prey to shearwaters.

  1. Geological and operational summary, North Aleutian Shelf Coast No. 1 well, Bering Sea, Alaska. Final report

    SciTech Connect

    Turner, R.F.

    1988-11-01

    Discusses the first continental offshore stratigraphic test well drilled in the North Aleutian Basin Planning Area, Bering Sea, Alaska. The well was drilled to determine the hydrocarbon potential of the area. The report covers drilling operations; lithology and core data; velocity analysis; geologic setting and tectonic framework; seismic stratigraphy; well-log interpretation and lithostratigraphy; paleontology and biostratigraphy; geothermal gradient; organic geochemistry; abnormal formation pressure; geologic hazards and shallow geology; and environmental considerations.

  2. Possible deep-water gas hydrate accumulations in the Bering Sea

    USGS Publications Warehouse

    Barth, Ginger A.; Scholl, David W.; Childs, Jonathan R.

    2006-01-01

    Seismic reflection images from the deep-water Aleutian and Bowers Basins of the Bering Sea contain many hundreds of acoustic Velocity-AMPlitude (VAMP) anomalies, each of which may represent a large accumulation of natural gas hydrate. Against a backdrop of essentially horizontal sedimentary reflections, the VAMP anomalies stand out as both high-amplitude bright spots and zones of vertically aligned horizon distortions. The VAMPs are interpreted as natural gas chimneys overlain by concentrated hydrate caps.

  3. Identification of multiple nursery habitats of skates in the eastern Bering Sea.

    PubMed

    Hoff, G R

    2016-05-01

    The use of more than a single nursery habitat type is examined for oviparous elasmobranchs using data summarized from studies conducted on the Alaska skate Bathyraja parmifera and the Aleutian skate Bathyraja aleutica in the eastern Bering Sea. The eastern Bering Sea skate species use two discrete areas as nurseries, one for egg deposition and a second for newly emergent juveniles. Egg deposition sites were located along the outer shelf and upper slope near canyons in the eastern Bering Sea. Newly emergent juveniles were found along the outer and middle shelf for B. parmifera and deep-slope for B. aleutica, suggesting that habitat used by newly emergent juvenile skates is distinct from habitat used for egg deposition and embryo development. In reviewing many studies on oviparous elasmobranchs, similar patterns emerge of habitat use during their early life history. To distinguish these distinct habitats, appropriate terminology is proposed. Egg case nursery is suggested for areas of egg deposition and juvenile nursery is suggested for areas where juveniles aggregate after emergence. Criteria to describe each habitat type are outlined.

  4. Penultimate and last glacial cycles in the western Bering Sea: evidence from micropaleontological and sedimentary records

    NASA Astrophysics Data System (ADS)

    Ovsepyan, Ekaterina; Ivanova, Elena; Murdmaa, Ivar

    2014-05-01

    The short- and long-term variability of sea-surface bioproductivity, intermediate-water oxygenation, sea ice conditions and bottom current velocities are inferred from the high-resolution multi-proxy study based on benthic (BF) and planktonic (PF) foraminiferal assemblages and sedimentary record of the 18m-long Core SO201-2-85KL (western Bering Sea). Early MIS 6 is characterized by a very low seasonal bioproductivity, moderate bottom-water oxygenation, and expanded seasonal sea ice conditions, as documented by the abundant phytodetritus species Alabaminella weddelensis, Islandiella norcrossi and Epistominella arctica, suboxic group of BF, and high accumulation rates of gravel grains, respectively. Middle MIS 6 is represented by intercalation of green diatomaceous ooze and grey clayey silt layers with sharp peaks of BF abundance in green interbeds. These spikes might result either from short-term events of enhanced sea surface bioproductivity or from lateral BF transport by intensified bottom currents, as it is demonstrated by high-amplitude variations of the clay/silt ratio. Rather high seasonal productivity and northward migration of the sea ice margin are reconstructed for the late MIS 6 that is also characterized by a slight increase in the Northern Hemisphere summer insolation. Strong dissolution of calcareous microfossils is revealed for MIS 5.5-5.1 when the Bering Strait was open. Dissolution might be caused by an excess of carbon dioxide in the bottom-water due to an abundant organic matter decay and/or to an influence of the old CO2-rich deep water. MIS 4 - early Termination I is characterized by a dominance of glacial benthic foraminiferal assemblages that implies low bioproductivity conditions. A prevalence of suboxic BF group suggests moderate bottom-water oxygenation. Sea ice rafting occurred in the western Bering Sea during MIS 4 - early Termination I but the drifted ice was not so dense as during MIS 6. The well-known productivity spikes at B

  5. Determination of multiple toxins in whelk and clam samples collected from the Chukchi and Bering seas.

    PubMed

    Li, Aifeng; Chen, Huidan; Qiu, Jiangbing; Lin, Heshan; Gu, Haifeng

    2016-01-01

    Buccinidae whelk Neptunea varicifera (Dall), Cardiidae clam Serripes laperousii (Deshayes), and two unknown species of whelk and clam were collected from the Arctic Chukchi Sea and sub-Arctic Bering Sea in July 2014. In this study, the mollusk samples were analyzed by different liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) methods for multiple shellfish toxins, including okadaic acid (OA), pectenotoxin (PTX), yessotoxin (YTX), azaspiracid (AZA), cyclic imines (CI), and saxitoxin (STX) groups. PTX2 (≈2.0 μg kg(-1) whole tissues) was detected exclusively in the clam S. laperousii collected from the Chukchi Sea. OA and dinophysistoxin-1 (DTX1) were restricted to mollusk samples collected from the Bering Sea, and OA was the dominant component of the whelk N. varicifera (63 μg kg(-1) digestive gland) and an unknown species of whelk (6.8 μg kg(-1) digestive gland). Spirolide-1 (SPX1) was confirmed in most samples except for the whelk N. varicifera collected from the Bering Sea. The highest content of SPX1 (≈18.5 μg kg(-1) digestive gland) occurred in the whelk N. varicifera collected from the Chukchi Sea, along with the suspected presence of SPX-C, SPX-D and didesMe-SPX-C. YTX, as well as its derivatives 45-OH-YTX and 45,46,47-Trinor-YTX, were found in all samples, with the highest YTX content (66 μg kg(-1) digestive gland) present in the whelk N. varicifera collected from the Chukchi Sea. Interestingly, STX and dcSTX were measured only in the whelk N. varicifera and unknown species of clam collected from the Chukchi Sea. No AZA-group toxins, gymnodimine (GYM), or pinnatoxin G were found in any samples analyzed. Results demonstrated that the mollusk samples were contaminated by multiple shellfish toxins in the Chukchi and Bering seas. This study highlights the need to monitor potentially toxic microalgae in the Arctic and sub-Arctic regions, as well as species of mollusk that may be included in future commercial or

  6. Deglacial-Holocene variability of sea ice and surface water temperature in the Bering Sea: Reconstruction based on "IP25" and alkenone data

    NASA Astrophysics Data System (ADS)

    Meheust, M.; Stein, R.; Fahl, K.

    2012-04-01

    Overall goal of our study of sediment material collected during RV Sonne Cruise 202 (INOPEX) in 2009 (Gersonde et al., Curise Report 2009), is the reconstruction of the short-term variability of sea-ice, sea-surface temperature (SST), primary productivity and terrigenous input in the subpolar North Pacific/Bering Sea and their relationship to global climate change, using organic-geochemical proxies (i.e. organic-geochemical bulk parameters and biomarkers such as: TOC, hydrogen indices; long-chain n-alkanes, sterols, alkenones; Uk37 and TEX86-Index; BIT-Index; HBIs, IP25, PIP25). In a first phase, these organic-geochemical proxies have been determined in surface sediments. The results show that the biomarker proxies reflect modern sea-ice and SST distributions as well as areas of increased primary productivity and increased input of terrigenous (organic) matter quite well. In a second phase of the project, the biomarkers have been determined in three selected sediment cores: Core SO 202-18-6 (Umnak Plateau/Bering Sea; 60.127°N, 179.444°W; water depth 1105 m; core length 7.21 m; age interval 0 to 14 kyr.BP). Core SO 202-07-6 (Detroit Seamount/western subpolar North Pacific; 51.272°N, 167.700°W; water depth 2340 m WD; core length 4.69 m; age interval MIS 1 to 3). Core SO 202-27-6 (Patton Seamount/eastern subpolar North Pacific; 54.296°N, 149.600°W; water depth 2919 m; core length 2.91 m: age interval MIS 1 to 3). Here, we concentrate especially on the variability of sea-ice cover and SST, using the newly developed sea-ice proxy "IP25" (Belt et al., 2007) and alkenone data, respectively, determined in the AMS14C-dated Core SO 202-18-6. Based on these biomarker records, sea-ice cover and SST changed significantly in the northern Bering Sea during Deglacial-Holocene times. The Younger Dryas interval is characterized by extended sea-ice cover, coinciding with a drop in SST to 2-4°C. With the end of the Younger Dryas, between 460 and 420 cmbsf, sea-ice cover

  7. Coupled wind-forced controls of the Bering-Chukchi shelf circulation and the Bering Strait throughflow: Ekman transport, continental shelf waves, and variations of the Pacific-Arctic sea surface height gradient

    NASA Astrophysics Data System (ADS)

    Danielson, Seth L.; Weingartner, Thomas J.; Hedstrom, Katherine S.; Aagaard, Knut; Woodgate, Rebecca; Curchitser, Enrique; Stabeno, Phyllis J.

    2014-06-01

    We develop a conceptual model of the closely co-dependent Bering shelf, Bering Strait, and Chukchi shelf circulation fields by evaluating the effects of wind stress over the North Pacific and western Arctic using atmospheric reanalyses, current meter observations, satellite-based sea surface height (SSH) measurements, hydrographic profiles, and numerical model integrations. This conceptual model suggests Bering Strait transport anomalies are primarily set by the longitudinal location of the Aleutian Low, which drives oppositely signed anomalies at synoptic and annual time scales. Synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves, whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along-strait (meridional) pressure gradient. In particular, we show that storms centered over the Bering Sea excite continental shelf waves on the eastern Bering shelf that carry northward velocity anomalies northward through Bering Strait and along the Chukchi coast. The integrated effect of these storms tends to decrease the northward Bering Strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the Aleutian Basin and the Western Subarctic Gyre. Ekman suction then increases the water column density through isopycnal uplift, thereby decreasing the dynamic height, sea surface height, and along-strait pressure gradient. Storms displaced eastward over the Gulf of Alaska generate an opposite set of Bering shelf and Aleutian Basin responses. While Ekman pumping controls Canada Basin dynamic heights (Proshutinsky et al., 2002), we do not find evidence for a strong relation between Beaufort Gyre sea surface height variations and the annually averaged Bering Strait throughflow. Over the western Chukchi and East Siberian seas easterly winds promote coastal divergence, which also increases the along-strait pressure head, as

  8. Organic storage of CO 2 on the continental slope off the mid-Atlantic bight, the southeastern Bering Sea, and the Peru coast

    NASA Astrophysics Data System (ADS)

    Walsh, John J.; Premuzic, Eugene T.; Gaffney, Jeffrey S.; Rowe, Gilbert T.; Harbottle, Garman; Stoenner, Raymond W.; Balsam, William L.; Betzer, Peter R.; Macko, Steven A.

    1985-07-01

    A comparison is made of organic content, sedimentation rates derived from 14C and 210Pb analyses, 13C and 15N isotope ratios, amorphous silica, particle size, and calcium carbonate within sediments from slopes off the mid-Atlantic bight, the southeastern Bering Sea, and the Peru coast. These sediments are mainly marine, diatom-rich, and about one-third of the organic carbon is recent, reflecting a possible transient of shelf export in response to man's increased activities since the industrial revolution. Using a combination of sedimentation and mixing rates of carbon, the C:N ratio of sediments within the upper 50 cm, and the amount of nitrogen thought to be released from the coastal zone, independent estimates suggest a carbon loading to world slopes of ˜0.3 to 0.5 × 10 9 tons C y -1. The Bering slope exhibits no anthropogenic transients, however, while increased carbon loading may have occurred off Peru in response to overfishing and off the mid-Atlantic bight in response to eutrophication. The generality of our results depends on which of the three systems is most representative of world slopes.

  9. Growth and condition of juvenile chum and pink salmon in the northeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Wechter, Melissa E.; Beckman, Brian R.; Andrews, Alexander G., III; Beaudreau, Anne H.; McPhee, Megan V.

    2017-01-01

    As the Arctic continues to warm, abundances of juvenile Pacific salmon (Oncorhynchus spp.) in the northern Bering Sea are expected to increase. However, information regarding the growth and condition of juvenile salmon in these waters is limited. The first objective of this study was to describe relationships between size, growth, and condition of juvenile chum (O. keta) and pink (O. gorbuscha) salmon and environmental conditions using data collected in the northeastern Bering Sea (NEBS) from 2003-2007 and 2009-2012. Salmon collected at stations with greater bottom depths and cooler sea-surface temperature (SST) were longer, reflecting their movement further offshore out of the warmer Alaska Coastal Water mass, as the season progressed. Energy density, after accounting for fish length, followed similar relationships with SST and bottom depth while greater condition (weight-length residuals) was associated with warm SST and shallower stations. We used insulin-like growth factor-1 (IGF-1) concentrations as an indicator of relative growth rate for fishes sampled in 2009-2012 and that found fish exhibited higher IGF-1 concentrations in 2010-2012 than in 2009, although these differences were not clearly attributable to environmental conditions. Our second objective was to compare size and condition of juvenile chum and pink salmon in the NEBS between warm and cool spring thermal regimes of the southeastern Bering Sea (SEBS). This comparison was based on a hypothesis informed by the strong role of sea-ice retreat in the spring for production dynamics in the SEBS and prevailing northward currents, suggesting that feeding conditions in the NEBS may be influenced by production in the SEBS. We found greater length (both species) and condition (pink salmon) in years with warm thermal regimes; however, both of these responses changed more rapidly with day of year in years with cool springs. Finally, we compared indicators of energy allocation between even and odd brood

  10. Tephrostratigraphic investigations of the Late Pleistocene-Holocene deposits in the northwestern Pacific Ocean and adjacent seas (Okhotsk and Bering)

    NASA Astrophysics Data System (ADS)

    Derkachev, A.; Nikolaeva, N.; Portnyagin, M.; Ponomareva, V.; Gorbarenko, S.; Malakhov, M.; Nuernberg, D.; van den Bogaard, C.; Sakamoto, T.; Lv, H.

    2012-12-01

    Ash layers (tephra) in both continental and marine deposits bear information about history and nature of volcanic eruptions which could influence climate, processes of sedimentation, and even cause ecological disasters. Tephra layers of Quaternary age have been identified in various marine and continental deposits within the northwestern part of transition zone from the Asian continent to the Pacific Ocean. Tephras from the areas adjacent to the Japanese Islands are better studied while those from the areas farther north including Okhotsk and Bering Seas have received less attention until recently. More than 40 sediment cores were obtained during numerous expeditions performed by Russian, German, Japanese and Chinese scientists during the last fifteen years. We have identified and sampled a total of 74 tephra layers and lenses from these cores including 22 layers in the Okhotsk Sea, 14 layers in the Bering Sea, and 38 layers - in the northwestern Pacific (Kronotsky Bay and Meiji Seamount). Ages of tephra layers have been estimated based on age-depth models for the cores developed in the result of litho- and biostratigraphic studies, paleomagnetic and oxygen-isotope research, and 14C dating. Tephra from all these layers have been characterized based on morphology of glass shards, optical properties (refractive indices), and chemical composition of glass (major and trace elements) and minerals (major elements). About 3500 precise and consistent electron probe and ~200 LA-ICP-MS analyses of volcanic glasses and 1200 electron probe analyses of minerals comprise the core of our new data base. Processing of these data has allowed us to correlate a number of tephra layers between the cores in each of the studied regions. Several tephra layers have been correlated between the Bering Sea and Pacific cores. These results permit direct comparisons of the paleoceanological records over the vast area in the northwestern Pacific domain. Studied tephra layers form the basis of

  11. 50 CFR Figure 17 to Part 679 - Northern Bering Sea Research Area and St. Lawrence Island Habitat Conservation Area

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Northern Bering Sea Research Area and St. Lawrence Island Habitat Conservation Area 17 Figure 17 to part 679 Wildlife and Fisheries FISHERY... Sea Research Area and St. Lawrence Island Habitat Conservation Area ER25JY08.011...

  12. 77 FR 22750 - Fisheries of the Exclusive Economic Zone Off Alaska; Groundfish Fisheries in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-17

    ...: Notice; intent to prepare an environmental impact statement, request for comments. SUMMARY: NMFS, in... environmental impact statement (EIS) on Steller sea lion protection measures for the Bering Sea and Aleutian Islands management area (BSAI) groundfish fisheries, in accordance with the National Environmental...

  13. A macrodescriptor perspective of ecological attributes for the Bering and Barents Seas

    NASA Astrophysics Data System (ADS)

    Megrey, Bernard A.; Aydin, Kerim Y.

    2009-10-01

    The eastern Bering Sea (EBS) and Barents Sea (BS) are both high-latitude, subarctic ecosystems that share many similar biophysical and trophic characteristics, and support valuable commercial fisheries. In this paper we compare system-level characteristics that make the Bering and Barents Sea ecosystems unique. We use Ecopath models and systems ecology macrodescriptor metrics applied to the two marine ecosystems to identify key areas of differences and similarities. Metrics calculated include number of species, number of interactions or trophic links, connectivity of the system, number of interactions per species, a measure of directed connectance, and an assessment of overall web interaction strength. In addition, number of basal species, number of top predators, total number of intermediate species, number of cannibals, number of cycles, number of omnivores, number of predators for a prey item, number of prey items for a predator, predator to prey ratio, and other indices were enumerated. Calculated food-web metrics for the eastern Bering and Barents Seas are compared between systems as well as with other similar metrics from published sources. We attempt to relate these observations to the questions of the uniqueness of marine food webs, implications for system stability, how climate impacts the physical environment, how the physical environment affects the structure of fish communities in each sea, and how changes in the physical environment affect the production of fish and the ability of the Bering and Barents Seas to support stable fisheries and productive ecosystems. Results show that the average number of trophic steps from primary producers to predators is shorter in the EBS. In the EBS, trophic pathways are shorter and more linear, there are more benthic species (flatfish and crabs) and there are both pelagic and benthic food webs. The BS is mainly a pelagic ecosystem. More production flows to the detritus pool in the BS most likely due to its deeper

  14. A year in the acoustic world of bowhead whales in the Bering, Chukchi and Beaufort seas

    NASA Astrophysics Data System (ADS)

    Clark, Christopher W.; Berchok, Catherine L.; Blackwell, Susanna B.; Hannay, David E.; Jones, Josh; Ponirakis, Dimitri; Stafford, Kathleen M.

    2015-08-01

    Bowhead whales, Balaena mysticetus, in the Bering-Chukchi-Beaufort (BCB) population, experience a variable acoustic environment among the regions they inhabit throughout the year. A total of 41,698 h of acoustic data were recorded from 1 August 2009 through 4 October 2010 at 20 sites spread along a 2300 km transect from the Bering Sea to the southeast Beaufort Sea. These data represent the combined output from six research teams using four recorder types. Recorders sampled areas in which bowheads occur and in which there are natural and anthropogenic sources producing varying amounts of underwater noise. We describe and quantify the occurrence of bowheads throughout their range in the Bering, Chukchi, and Beaufort seas over a 14-month period by aggregating our acoustic detections of bowhead whale sounds. We also describe the spatial-temporal variability in the bowhead acoustic environment using sound level measurements within a frequency band in which their sounds occur, by dividing a year into three, 4-month seasons (Summer-Fall 2009, August-November 2009: Winter 2009-2010, December 2009-March 2010: and Spring-Summer 2010, April-July 2010) and their home range into five zones. Statistical analyses revealed no significant relationship between acoustic occurrence, distance offshore, and water depth during Summer-Fall 2009, but there was a significant relationship during Spring-Summer 2010. A continuous period with elevated broadband sound levels lasting ca. 38 days occurred in the Bering Sea during the Winter 2009-2010 season as a result of singing bowheads, while a second period of elevated levels lasting at least 30 days occurred during the early spring-summer season as a result of singing bearded seals. The lowest noise levels occurred in the Chukchi Sea from the latter part of November into May. In late summer 2009 very faint sounds from a seismic airgun survey approximately 700 km away in the eastern Beaufort Sea were detected on Chukchi recorders. Throughout

  15. Retrospective analysis of Bering Sea bottom trawl surveys: regime shift and ecosystem reorganization

    NASA Astrophysics Data System (ADS)

    Conners, M. E.; Hollowed, A. B.; Brown, E.

    2002-10-01

    This paper compiles data from bottom trawl surveys using variations on a 400-mesh eastern trawl gear into a 38-year time series (1963-2000), using a robust index of median catch per unit effort (CPUE) as an indicator of regional abundance. Time series are presented for three index sites in the southeastern Bering Sea: the inner shelf in Bristol Bay, the middle shelf north of Unimak Island, and the outer shelf near the Pribilof Islands. All three sites show strong evidence of a shift in benthic biomass and community structure in the early to mid-1980s. During this period, all three sites showed substantial increases in the abundances of walleye pollock, Pacific cod, rock sole, flathead sole, cartilaginous fishes (skates) and non-crab benthic invertebrates. Species composition, especially of flatfish, differs at the three sites, but the trend for groundfish abundance to increase was consistent at all three sites. The similarity in trends both across the region and across both commercial and unexploited groups suggests to us that a complete reorganization of benthic and demersal food webs may have taken place. The timing of change in trawl catch weight is consistent with effects of the strong regime shift observed in climate indices in 1976-1977. There is little evidence of similar biological responses to subsequent, less pronounced changes in climate. Our data are also consistent with recently documented shifts in ecosystem dynamics resulting from changes in ice cover and thermal structure in the eastern Bering Sea. Our analysis indicates that there was a much higher biomass of groundfish at all three sites during 1980-2000 than in 1960-1980. This result provides evidence against the hypothesis that the overall productivity of the eastern Bering Sea has decreased. The precipitous decline of the endangered Steller sea lion in this region from 1975-1985 was concurrent with an overall increase in abundance of groundfish prey.

  16. Timing of ice retreat alters seabird abundances and distributions in the southeast Bering Sea.

    PubMed

    Renner, Martin; Salo, Sigrid; Eisner, Lisa B; Ressler, Patrick H; Ladd, Carol; Kuletz, Kathy J; Santora, Jarrod A; Piatt, John F; Drew, Gary S; Hunt, George L

    2016-09-01

    Timing of spring sea-ice retreat shapes the southeast Bering Sea food web. We compared summer seabird densities and average bathymetry depth distributions between years with early (typically warm) and late (typically cold) ice retreat. Averaged over all seabird species, densities in early-ice-retreat-years were 10.1% (95% CI: 1.1-47.9%) of that in late-ice-retreat-years. In early-ice-retreat-years, surface-foraging species had increased numbers over the middle shelf (50-150 m) and reduced numbers over the shelf slope (200-500 m). Pursuit-diving seabirds showed a less clear trend. Euphausiids and the copepod Calanus marshallae/glacialis were 2.4 and 18.1 times less abundant in early-ice-retreat-years, respectively, whereas age-0 walleye pollock Gadus chalcogrammus near-surface densities were 51× higher in early-ice-retreat-years. Our results suggest a mechanistic understanding of how present and future changes in sea-ice-retreat timing may affect top predators like seabirds in the southeastern Bering Sea.

  17. Satellite color observations of spring blooming in Bering Sea shelf waters during the ice edge retreat in 1980

    NASA Technical Reports Server (NTRS)

    Maynard, Nancy G.; Clark, Dennis K.

    1987-01-01

    The temporal and spatial development of the ice-edge bloom and the spring open-water bloom on the eastern Bering Sea shelf was studied using CZCS images of the eastern Bering Sea between April 27 and July 22, 1980. Images of the Norton Sound area taken during the period of ice breakup show that the influence of ice melt on phytoplankton growth is particularly significant where the ice is actively melting. Significant levels (5-30 mg/cu m) of chlorophyll could be seen trailing the ice pack as it melted and moved northward and westward in late April and early May. In the ice-free eastern Bering Sea midsummer image, a northwesterly oriented band of high pigment concentration was seen in the area of the outer domain, suggesting periodic offshore movements of shelf waters.

  18. Distribution of Arctic and Pacific copepods and their habitat in the northern Bering and Chukchi seas

    NASA Astrophysics Data System (ADS)

    Sasaki, Hiroko; Matsuno, Kohei; Fujiwara, Amane; Onuka, Misaki; Yamaguchi, Atsushi; Ueno, Hiromichi; Watanuki, Yutaka; Kikuchi, Takashi

    2016-08-01

    The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic-benthic-type ecosystem to a pelagic-pelagic type.

  19. Cold Regime Interannual Variability of Primary and Secondary Producer Community Composition in the Southeastern Bering Sea

    PubMed Central

    Stauffer, Beth A.; Miksis-Olds, Jennifer; Goes, Joaquim I.

    2015-01-01

    Variability of hydrographic conditions and primary and secondary productivity between cold and warm climatic regimes in the Bering Sea has been the subject of much study in recent years, while interannual variability within a single regime and across multiple trophic levels has been less well-documented. Measurements from an instrumented mooring on the southeastern shelf of the Bering Sea were analyzed for the spring-to-summer transitions within the cold regime years of 2009–2012 to investigate the interannual variability of hydrographic conditions, primary producer biomass, and acoustically-derived secondary producer and consumer abundance and community structure. Hydrographic conditions in 2012 were significantly different than in 2009, 2010, and 2011, driven largely by increased ice extent and thickness, later ice retreat, and earlier stratification of the water column. Primary producer biomass was more tightly coupled to hydrographic conditions in 2012 than in 2009 or 2011, and shallow and mid-column phytoplankton blooms tended to occur independent of one another. There was a high degree of variability in the relationships between different classes of secondary producers and hydrographic conditions, evidence of significant intra-consumer interactions, and trade-offs between different consumer size classes in each year. Phytoplankton blooms stimulated different populations of secondary producers in each year, and summer consumer populations appeared to determine dominant populations in the subsequent spring. Overall, primary producers and secondary producers were more tightly coupled to each other and to hydrographic conditions in the coldest year compared to the warmer years. The highly variable nature of the interactions between the atmospherically-driven hydrographic environment, primary and secondary producers, and within food webs underscores the need to revisit how climatic regimes within the Bering Sea are defined and predicted to function given

  20. Polychaete assemblage as surrogate for prey availability in assessing southeastern Bering Sea flatfish habitat

    NASA Astrophysics Data System (ADS)

    Yeung, Cynthia; Yang, Mei-Sun; Jewett, Stephen C.; Naidu, A. S.

    2013-02-01

    The flatfish yellowfin sole (Limanda aspera), northern rock sole (Lepidopsetta polyxystra), and Alaska plaice (Pleuronectes quadrituberculatus) in the southeastern Bering Sea prey mainly on infauna. Spatial correspondence between their stomach contents and infauna assemblages across habitat types was examined to identify indices of prey availability for flatfish habitat characterization and quality assessment. Benthic samples and flatfish stomachs were collected in 2009 near the Alaska Peninsula in the southeastern Bering Sea. Polychaetes and bivalves were the most dominant infauna groups, each comprising 35-60% by weight in each infauna sample. These two were also the only prey groups that frequently averaged > 50% of stomach content by weight. Bivalves dominated the infauna biomass on the relatively sandy inner shelf (0-50 m depth). The muddier middle shelf (50-100 m) had the highest infauna biomass, which was dominated by polychaetes. Diet compositions of the flatfish varied spatially in correspondence with the infauna assemblage. Polychaetes were prevalent in all flatfish diets on the middle shelf, even yellowfin sole whose typical primary prey are amphipods and bivalves. Polychaete-rich habitats are potentially prime for flatfish as polychaetes are readily utilized where available and generally have high nutritional value. Flatfish did not select for specific polychaete taxa, so an index of habitat quality could be based on the biomass of aggregate polychaetes or on dominant polychaete families of the region. Under normal environmental conditions, the three flatfish have slightly-offset spatial distributions, enabling each to utilize different infauna assemblages across the shelf. However, during cold phases in the Bering Sea ecosystem, as when this study was conducted, a cold pool of < 2 °C bottom water from the spring ice melt extends over the middle shelf in summer. This physiological barrier displaces all three flatfish to the inner shelf, intensifying

  1. Dispersal and behavior of pacific halibut hippoglossus stenolepis in the bering sea and Aleutian islands region

    USGS Publications Warehouse

    Seitz, A.C.; Loher, T.; Norcross, Brenda L.; Nielsen, J.L.

    2011-01-01

    Currently, it is assumed that eastern Pacific halibut Hippoglossus stenolepis belong to a single, fully mixed population extending from California through the Bering Sea, in which adult halibut disperse randomly throughout their range during their lifetime. However, we hypothesize that hali but dispersal is more complex than currently assumed and is not spatially random. To test this hypo thesis, we studied the seasonal dispersal and behavior of Pacific halibut in the Bering Sea and Aleutian Islands (BSAI). Pop-up Archival Transmitting tags attached to halibut (82 to 154 cm fork length) during the summer provided no evidence that individuals moved out of the Bering Sea and Aleutian Islands region into the Gulf of Alaska during the mid-winter spawning season, supporting the concept that this region contains a separate spawning group of adult halibut. There was evidence for geographically localized groups of halibut along the Aleutian Island chain, as all of the individuals tagged there displayed residency, with their movements possibly impeded by tidal currents in the passes between islands. Mid-winter aggregation areas of halibut are assumed to be spawning grounds, of which 2 were previously unidentified and extend the species' presumed spawning range ~1000 km west and ~600 km north of the nearest documented spawning area. If there are indeed independent spawning groups of Pacific halibut in the BSAI, their dynamics may vary sufficiently from those of the Gulf of Alaska, so that specifically accounting for their relative segregation and unique dynamics within the larger population model will be necessary for correctly predicting how these components may respond to fishing pressure and changing environmental conditions.?? Inter-Research 2011.

  2. Latitudinal trends and temporal shifts in the catch composition of bottom trawls conducted on the eastern Bering Sea shelf

    NASA Astrophysics Data System (ADS)

    Stevenson, Duane E.; Lauth, Robert R.

    2012-06-01

    Latitudinal species diversity gradients are well known in both terrestrial and aquatic ecosystems throughout the world. However, trends in relative abundance and other shifts in community structure with latitude, which can be more sensitive to environmental shifts such as climate change, have received less attention. Here we investigate latitudinal trends in the seafloor community of the eastern Bering Sea using catches of fishes and epibenthic invertebrates in bottom trawl surveys conducted from 1982 to 2010. Our results indicate that the overall biomass of the epibenthic community declines with increasing latitude in the eastern Bering Sea. This latitudinal trend is primarily driven by declining fish catches in the northern Bering Sea, which in turn reflects changes in the structure of the fish community. The fish fauna in northern latitudes is increasingly dominated by gadids, though the species composition of the gadid fauna also changes with latitude, with smaller species becoming more common in the north. The biomass of the invertebrate megafauna remains relatively consistent throughout the eastern Bering Sea, but invertebrates make up a larger proportion of the catch in bottom trawls conducted at higher latitudes. The epibenthic invertebrate megafauna in the eastern Bering Sea is composed primarily of sea stars (Asteriidae) and oregoniid crabs (Chionoecetes and Hyas), though no clear latitudinal trends in the invertebrate community are evident. Limited trawl data from the eastern Chukchi Sea indicate that the fish community farther north is even more heavily dominated by gadids, and the epibenthic invertebrate community is dominated by asteriid sea stars. Temperature data from bottom trawl surveys in the southeastern Bering Sea over the past decade indicate that there was a distinct temperature shift around 2005, and the relatively warm years of 2001-2005 were followed by five relatively cold years. This shift in the summer temperature regime of the Bering

  3. Middle pleistocene mollusks from St. Lawrence Island and their significance for the paleo-oceanography of the Bering Sea

    USGS Publications Warehouse

    Hopkins, D.M.; Rowland, R.W.; Patton, W.W.

    1972-01-01

    Drift, evidently of Illinoian age, was deposited on St. Lawrence Island at the margin of an ice cap that covered the highlands of the Chukotka Peninsula of Siberia and spread far eastward on the continental shelf of northern Bering Sea. Underlying the drift on the northwestward part of the island are mollusk-bearing beds deposited during the Kotzebuan Transgression. A comparison of mollusk faunas from St. Lawrence Island, Chukotka Peninsula, and Kotzebue Sound suggests that the present northward flow through Bering and Anadyr Straits was reversed during the Kotzebuan Transgression. Cold arctic water penetrated southward and southwestward bringing an arctic fauna to the Gulf of Anadyr. Warmer Pacific water probably entered eastern Bering Sea, passed eastward and northeastward around eastern and northern St. Lawrence Island, and then became entrained in the southward currents that passed through Anadyr Strait. ?? 1972.

  4. Genetic stock identification of chum salmon in the Bering Sea and North Pacific Ocean using mitochondrial DNA microarray.

    PubMed

    Moriya, Shogo; Sato, Shunpei; Azumaya, Tomonori; Suzuki, Osamu; Urawa, Shigehiko; Urano, Akihisa; Abe, Syuiti

    2007-01-01

    A newly developed DNA microarray was applied to identify mitochondrial (mt) DNA haplotypes of more than 2200 chum salmon in the Bering Sea and North Pacific Ocean in September 2002 and also 2003, when the majority of maturing fish were migrating toward their natal river. The distribution of haplotypes occurring in Asian and North American fish in the surveyed area was similar in the 2 years. A conditional maximum likelihood method for estimation of stock compositions indicated that the Japanese stocks were distributed mainly in the north central Bering Sea, whereas the Russian stocks were mainly in the western Bering Sea. The North American stocks were abundant in the North Pacific Ocean around the Aleutian Islands. These results indicate that the Asian and North American stocks of chum salmon are nonrandomly distributed in the Bering Sea and the North Pacific Ocean, and further the oligonuleotide DNA microarray developed by us has a high potential for identification of stocks among mixed ocean aggregates of high-seas chum salmon.

  5. Flatfish recruitment response to decadal climatic variability and ocean conditions in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Wilderbuer, T. K.; Hollowed, A. B.; Ingraham, W. J.; Spencer, P. D.; Conners, M. E.; Bond, N. A.; Walters, G. E.

    2002-10-01

    This paper provides a retrospective analysis of the relationship of physical oceanography and biology and recruitment of three Eastern Bering Sea flatfish stocks: flathead sole ( Hippoglossoides elassodon), northern rock sole ( Lepidopsetta polyxystra), and arrowtooth flounder ( Atheresthes stomias) for the period 1978-1996. Temporal trends in flatfish production in the Eastern Bering Sea are consistent with the hypothesis that decadal scale climate variability influences marine survival during the early life history period. Density-dependence (spawning stock size) is statistically significant in a Ricker model of flatfish recruitment, which includes environmental terms. Wind-driven advection of flatfish larvae to favorable nursery grounds was also found to coincide with years of above-average recruitment through the use of an ocean surface current simulation model (OSCURS). Ocean forcing of Bristol Bay surface waters during springtime was mostly shoreward (eastward) during the 1980s and seaward (westerly) during the 1990s, corresponding with periods of good and poor recruitment. Distance from shore and water depth at the endpoint of 90-day drift periods (estimated time of settlement) were also found to correspond with flatfish productivity.

  6. Hindcast storm events in the Bering Sea for the St. Lawrence Island and Unalakleet Regions, Alaska

    USGS Publications Warehouse

    Erikson, Li H.; McCall, Robert T.; van Rooijen, Arnold; Norris, Benjamin

    2015-01-01

    This study provides viable estimates of historical storm-induced water levels in the coastal communities of Gambell and Savoonga situated on St. Lawrence Island in the Bering Sea, as well as Unalakleet located at the head of Norton Sound on the western coast of Alaska. Gambell, Savoonga, and Unalakleet are small Native Villages that are regularly impacted by coastal storms but where little quantitative information about these storms exists. The closest continuous water-level gauge is at Nome, located more than 200 kilometers from both St. Lawrence Island and Unalakleet. In this study, storms are identified and quantified using historical atmospheric and sea-ice data and then used as boundary conditions for a suite of numerical models. The work includes storm-surge (temporary rise in water levels due to persistent strong winds and low atmospheric pressures) modeling in the Bering Strait region, as well as modeling of wave runup along specified sections of the coast in Gambell and Unalakleet. Modeled historical water levels are used to develop return periods of storm surge and storm surge plus wave runup at key locations in each community. It is anticipated that the results will fill some of the data void regarding coastal flood data in western Alaska and be used for production of coastal vulnerability maps and community planning efforts.

  7. 75 FR 52478 - Fisheries of the Economic Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian Islands AGENCY: National Marine...: Temporary rule; modification of a closure. SUMMARY: NMFS is opening directed fishing for Pacific cod by... 2010 total allowable catch (TAC) of Pacific cod specified for catcher vessels less than 60 feet...

  8. 76 FR 24404 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-02

    ... Economic Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian Islands Management Area AGENCY... cod by catcher vessels less than 60 feet (18.3 meters) length overall (LOA) using hook-and-line or pot... use the 2011 total allowable catch of Pacific cod allocated to catcher vessels less than 60 feet...

  9. 75 FR 19561 - Fisheries of the Economic Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-15

    ... Off Alaska; Pacific Cod in the Bering Sea and Aleutian Islands AGENCY: National Marine Fisheries...; modification of a closure. SUMMARY: NMFS is opening directed fishing for Pacific cod by catcher vessels less... catch (TAC) of Pacific cod specified for the BSAI. DATES: Effective 1200 hrs, Alaska local time...

  10. 76 FR 467 - Fisheries of the Exclusive Economic Zone Off Alaska; Inseason Adjustment to the 2011 Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-05

    ... Economic Zone Off Alaska; Inseason Adjustment to the 2011 Bering Sea and Aleutian Islands Pacific Cod Total... (BSAI) Pacific cod fishery. This action is necessary because NMFS has ] determined this TAC is incorrectly specified. This action will ensure the BSAI Pacific cod TAC is the appropriate amount, based...

  11. 77 FR 59852 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-01

    ...NMFS publishes regulations to implement Amendment 97 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). Amendment 97 allows the owner of a trawl catcher/processor vessel authorized to participate in the Amendment 80 catch share program to replace that vessel with a vessel that meets certain requirements. This action establishes the......

  12. 75 FR 50716 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-17

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program; Emergency Rule... a processor with West designated IPQ in the West region of the Aleutian Islands. An emergency exists because, due to a recent unforeseen event, no crab processing facility is open in the West region....

  13. 76 FR 5556 - Fisheries of the Exclusive Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-01

    ... Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands King and Tanner Crab Fishery Resources...-designated golden king crab IFQ to be delivered to a processor in the West region of the Aleutian Islands... king crab fishery, while providing for the sustained participation of municipalities in the...

  14. 75 FR 7205 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-18

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program; Emergency Rule... with West designated IPQ in the West region of the Aleutian Islands. An emergency exists, because... West region, but due to a recent unforeseen event, no processing facility is open in the West...

  15. 78 FR 13813 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ... Economic Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and 2014 Harvest Specifications for... criteria set out at Sec. 679.21(e)(1)(i), the 2013 and 2014 PSC limit of red king crab in Zone 1 for trawl...)(ii), the calculated 2013 and 2014 C. bairdi crab PSC limit for trawl gear is 980,000 animals in...

  16. 76 FR 35772 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-20

    ... Fisheries Act (AFA) vessels with historical participation in the Bering Sea snow crab fishery because these vessels are subject to GOA harvesting and processing restrictions under the AFA and the implementing regulations for the AFA (Sec. 679.64(b)). Vessels subject to the sideboards are referred to as ``non-AFA...

  17. 77 FR 40341 - Fisheries of the Exclusive Economic Zone Off Alaska; Notice of Public Workshop for Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-09

    ...) Crab Economic Data Reports (EDR) currently required from catcher vessels, catcher/processors, shoreside processors, and stationary floating crab processors participating in the BSAI Crab Rationalization Program... Alaska; Notice of Public Workshop for Bering Sea and Aleutian Islands Crab Economic Data Reports...

  18. 75 FR 69361 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-12

    ... available data and finds that the ITAC for Pacific ocean perch in the Bering Sea subarea needs to be... fisheries data in a timely fashion and would delay the apportionment of the non-specified reserves of... plan for the fishing season, and to avoid potential disruption to the fishing fleet and...

  19. 77 FR 46641 - Fisheries of the Exclusive Economic Zone Off Alaska; “Other Flatfish” in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-06

    ... Economic Zone Off Alaska; ``Other Flatfish'' in the Bering Sea and Aleutian Islands Management Area and... amounts of the non-specified reserve to the initial total allowable catch (ITAC) of ``other flatfish'' in.... The 2012 ITAC of ``other flatfish'' in the BSAI was established as 2,720 metric tons (mt), and...

  20. 76 FR 81873 - Fisheries of the Exclusive Economic Zone Off Alaska; Inseason Adjustment to the 2012 Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-29

    .... SUMMARY: NMFS is adjusting the 2012 total allowable catch (TAC) amount for the Bering Sea and Aleutian... this TAC is incorrectly specified. This action will ensure the BSAI Atka mackerel TAC is the... appear at subpart H of 50 CFR part 600 and 50 CFR part 679. The 2012 Atka mackerel TAC in the BSAI...

  1. 76 FR 1539 - Fisheries of the Exclusive Economic Zone Off Alaska; Inseason Adjustment to the 2011 Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-11

    .... SUMMARY: NMFS is adjusting the 2011 total allowable catch (TAC) amount for the Bering Sea and Aleutian... this TAC is incorrectly specified. This action will ensure the BSAI Atka mackerel TAC is the... appear at subpart H of 50 CFR part 600 and 50 CFR part 679. The 2011 Atka mackerel TAC in the BSAI...

  2. 78 FR 42718 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-17

    ... Economic Zone Off Alaska; Pacific Ocean Perch in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Pacific ocean perch in... exceeding the 2013 total allowable catch (TAC) of Pacific ocean perch in this area allocated to...

  3. 76 FR 66655 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod and Octopus in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-27

    ... Economic Zone Off Alaska; Pacific Cod and Octopus in the Bering Sea and Aleutian Islands Management Area... necessary to limit incidental catch of octopus by vessels using pot gear to fish for Pacific cod the BSAI... Act requires that conservation and management measures prevent overfishing. The 2011...

  4. 78 FR 28523 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-15

    ... the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program...://www.regulations.gov or from the Alaska Region Web site at http://alaskafisheries.noaa.gov . The... the NMFS Alaska Region Web site at http://alaskafisheries.noaa.gov . Written comments regarding...

  5. 77 FR 39441 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-03

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... total allowable catch (TAC) of Atka mackerel in this area allocated to vessels participating in the...

  6. 78 FR 35771 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-14

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... total allowable catch (TAC) of Atka mackerel in this area allocated to vessels participating in the...

  7. 75 FR 14498 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-26

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... A season allocation of Atka mackerel in this area allocated to vessels participating in...

  8. 76 FR 10780 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-28

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... necessary to prevent exceeding the A season allowance of the 2011 Atka mackerel total allowable catch...

  9. 75 FR 53606 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...: Temporary rule; closures and openings. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in... necessary to prevent exceeding the 2010 total allowable catch (TAC) of Atka mackerel in these areas...

  10. 78 FR 25878 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-03

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... season allowance of the 2013 Atka mackerel total allowable catch (TAC) in the CAI allocated to...

  11. 75 FR 6129 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-08

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. ] SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... to prevent exceeding the 2010 A season allocation of Atka mackerel in these areas allocated...

  12. 76 FR 65975 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-25

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... necessary to prevent exceeding the 2011 total allowable catch (TAC) of Atka mackerel in these...

  13. 77 FR 26212 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-03

    ... Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY.... ACTION: Temporary rule; closure. SUMMARY: NMFS is prohibiting directed fishing for Atka mackerel in the... season allowance of the 2012 Atka mackerel total allowable catch (TAC) in the CAI allocated to...

  14. 76 FR 68358 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-04

    ... Program, the western Aleutian Islands red king crab and Pribilof Islands red and blue king crab fisheries have failed to open, and the Saint Matthew Island blue king crab fishery has only been open during the... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY:...

  15. 76 FR 49423 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-10

    ... the CR Program, the western Aleutian Islands red king crab and Pribilof Islands red and blue king crab fisheries have failed to open, and the Saint Matthew Island blue king crab fishery has only been open during... Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY:...

  16. 78 FR 65602 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-01

    ... National Oceanic and Atmospheric Administration 50 CFR Part 679 RIN 0648-BD03 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Amendment 102 AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce....

  17. 78 FR 49200 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Pollock in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-13

    ... National Oceanic and Atmospheric Administration 50 CFR Part 679 RIN 0648-XC803 Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Pollock in the Bering Sea and Aleutian Islands AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce....

  18. Late quaternary oceanographic conditions in the Western Bering Sea

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Max, L.; Riethdorf, J.-R.; Nürnberg, D.; Tiedemann, R.

    2013-03-01

    The benthic and planktonic foraminiferal assemblages and the distribution of coarse grain-size factions were studied in the upper 4.5 m of the Core SO201-2-85KL (57°30.30' N, 170°24.79' E, water depth 968 m) retrieved from the Shirshov Ridge. This part of the core covers 7.5 to 50 kyr BP. The glacial period is established to be characterized by low surface water productivity, the wide distribution of sea ice and/or icebergs in this area, and a high oxygen concentration in the bottom layer. Enhanced productivity is inferred from the maximum abundance of planktonic foraminifers at the very beginning of the deglaciation. The late Bølling-Allerød interstadial and the early Holocene were marked by the further two-phase increase in the surface productivity and the weakened ventilation of the bottom water.

  19. Decadal Bering Sea seascape change: consequences for Pacific walruses and indigenous hunters.

    PubMed

    Ray, G Carleton; Hufford, Gary L; Overland, James E; Krupnik, Igor; McCormick-Ray, Jerry; Frey, Karen; Labunski, Elizabeth

    2016-01-01

    The most significant factors currently affecting the Pacific walrus (Odobenus rosmarus divergens) population are climate change and consequent changes in sea-ice morphology and dynamics. This paper integrates recent physical sea-ice change in the Bering Sea with biological and ecological conditions of walruses in their winter-spring reproductive habitat. Historically, walrus in winter-spring depended on a critical mass of sea-ice habitat to optimize social networking, reproductive fitness, feeding behavior, migration, and energetic efficiency. During 2003-2013, our cross-disciplinary, multiscale analysis from shipboard observations, satellite imagery, and ice-floe tracking, reinforced by information from indigenous subsistence hunters, documented change of sea-ice structure from a plastic continuum to a "mixing bowl" of ice floes moving more independently. This fragmentation of winter habitat preconditions the walrus population toward dispersal mortality and will also negatively affect the availability of resources for indigenous communities. We urge an expanded research and management agenda that integrates walrus natural history and habitat more completely with changing sea-ice morphology and dynamics at multiple scales, while also meeting the needs of local communities.

  20. Recent Bering Sea warm and cold events in a 95-year context

    NASA Astrophysics Data System (ADS)

    Overland, James E.; Wang, Muyin; Wood, Kevin R.; Percival, Donald B.; Bond, Nicholas A.

    2012-06-01

    The meteorology and oceanography of the southeastern Bering Sea shelf was recently dominated by a multi-year warm event (2000-2005) followed by a multi-year cold event (2007-2010). We put these recent events into the context of the 95-year air temperature record from St. Paul Island and with concurrent spatial meteorological fields. For March 2000-2005 the mean air temperature anomaly at St. Paul was 2.1 °C above the long-term mean, and for March 2007-2010 the mean temperature anomaly at St. Paul was 4.7 °C below the long-term mean. The only multi-year temperature deviations comparable to the first decade of the 2000s are a cold event from 1971 to 1976 followed by a warm event from 1978 to 1983. There was also a short warm event 1935-1937. The temperature transition between warm and cold events in the 1970s and 2000s took two years. While there are theoretical arguments for some physical memory processes in the North Pacific climate system, we cannot rule out that the recent warm and cold events are of a random nature: they are rare in the St. Paul temperature record, they are dominated by North Pacific-wide sea level pressure events rather than local Bering Sea processes, and they are consistent with a red noise model of climate variability. The 1970s transition appears to have an ENSO (El Niño-Southern Oscillation) influence, while the recent events are likely connected to Arctic-wide warming. Evidence provided by the 95-year St. Paul meteorological record reinforces the idea that a red-noise model of climate variability is appropriate for the North Pacific and southeastern Bering Sea. We stress the importance of relatively rare sub-decadal events and shifts, rather than multi-decadal variability associated with the Pacific Decadal Oscillation (PDO). Thus, in the future we can expect large positive and negative excursions in the region that can last for multiple years, but there is as yet little predictability for their timing and duration.

  1. Sea-ice habitat preference of the Pacific walrus (Odobenus rosmarus divergens) in the Bering Sea: A multiscaled approach

    NASA Astrophysics Data System (ADS)

    Sacco, Alexander Edward

    The goal of this thesis is to define specific parameters of mesoscale sea-ice seascapes for which walruses show preference during important periods of their natural history. This research thesis incorporates sea-ice geophysics, marine-mammal ecology, remote sensing, computer vision techniques, and traditional ecological knowledge of indigenous subsistence hunters in order to quantitatively study walrus preference of sea ice during the spring migration in the Bering Sea. Using an approach that applies seascape ecology, or landscape ecology to the marine environment, our goal is to define specific parameters of ice patch descriptors, or mesoscale seascapes in order to evaluate and describe potential walrus preference for such ice and the ecological services it provides during an important period of their life-cycle. The importance of specific sea-ice properties to walrus occupation motivates an investigation into how walruses use sea ice at multiple spatial scales when previous research suggests that walruses do not show preference for particular floes. Analysis of aerial imagery, using image processing techniques and digital geomorphometric measurements (floe size, shape, and arrangement), demonstrated that while a particular floe may not be preferred, at larger scales a collection of floes, specifically an ice patch (< 4 km2), was preferred. This shows that walruses occupy ice patches with distinct ice features such as floe convexity, spatial density, and young ice and open water concentration. Ice patches that are occupied by adult and juvenile walruses show a small number of characteristics that vary from those ice patches that were visually unoccupied. Using synthetic aperture radar imagery, we analyzed co-located walrus observations and statistical texture analysis of radar imagery to quantify seascape preferences of walruses during the spring migration. At a coarse resolution of 100 -- 9,000 km2, seascape analysis shows that, for the years 2006 -- 2008

  2. Exposure of basement rock on the continental slope of the bering sea

    USGS Publications Warehouse

    Scholl, D. W.; Buffington, E.C.; Hopkins, D.M.

    1966-01-01

    Profiles of repetitive seismic reflections reveal that the Bering continental slope, outer shelf, and rise overlay an acoustically reflective "basement" which extends at least 750 kilometers parallel to the trend of the slope. This acoustic basement is usually covered by several hundred meters of stratified sediments at the top and bottom of the slope; however, it is exposed in submarine canyons and flanking spurs along the main part of the slope for a distance of at least 550 kilometers northwest of the Pribilof Islands. The lithologic composition and the age of the rocks of the acoustic basement are not known. However, its probable seismic velocity of 3.1 to 3.7 kilometers per second suggests that it is composed of volcanic rocks or lithified sedimentary rocks or both. The regional geology suggests that the acoustic basement is the upper surface of folded late Mesozoic rocks which were locally intruded by granite and serpentine. The structure of the Bering slope, as deduced from the acoustic profiles, suggests that the surface of the basement has been monoclinically flexed and faulted between the shelf edge and the deep Aleutian Basin.

  3. BESMEX: Bering Sea marine mammal experiment. [with the primary target species being the walrus and bowhead whale

    NASA Technical Reports Server (NTRS)

    Ray, G. C.; Wartzok, D.

    1974-01-01

    Predictive ecological models are being studied for the management and conservation of the walrus, and the bowhead whale in the Bering Sea. The influence of sea ice on the distribution, and carrying capacity of the area for these two mammals is to be investigated with the primary target species being the walrus. Remote sensing and radio tracking is considered a requirement for assessing the walrus ecosystem.

  4. Discovery of two new large submarine canyons in the Bering Sea

    USGS Publications Warehouse

    Carlson, P.R.; Karl, Herman A.

    1984-01-01

    The Beringian continental margin is incised by some of the world's largest submarine canyons. Two newly discovered canyons, St. Matthew and Middle, are hereby added to the roster of Bering Sea canyons. Although these canyons are smaller and not cut back into the Bering shelf like the five very large canyons, they are nonetheless comparable in size to most of the canyons that have been cut into the U.S. eastern continental margin and much larger than the well-known southern California canyons. Both igneous and sedimentary rocks of Eocene to Pliocene age have been dredged from the walls of St. Matthew and Middle Canyons as well as from the walls of several of the other Beringian margin canyons, thus suggesting a late Tertiary to Quaternary genesis of the canyons. We speculate that the ancestral Yukon and possibly Anadyr Rivers were instrumental in initiating the canyon-cutting processes, but that, due to restrictions imposed by island and subsea bedrock barriers, cutting of the two newly discovered canyons may have begun later and been slower than for the other five canyons. ?? 1984.

  5. The role of ocean acidification in systemic carbonate mineral suppression in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Mathis, Jeremy T.; Cross, Jessica N.; Bates, Nicholas R.

    2011-10-01

    Ocean acidification driven by absorption of anthropogenic carbon dioxide (CO2) from the atmosphere is now recognized as a systemic, global process that could threaten diverse marine ecosystems and a number of commercially important species. The change in calcium carbonate (CaCO3) mineral saturation states (Ω) brought on by the reduction of seawater pH is most pronounced in high latitude regions where unique biogeochemical processes create an environment more susceptible to the suppression of Ω values for aragonite and calcite, which are critical to shell building organisms. New observations from the eastern Bering Sea shelf show that remineralization of organic matter exported from surface waters rapidly increases bottom water CO2 concentrations over the shelf in summer and fall, suppressing Ω values. The removal of CO2 from surface waters by high rates of phytoplankton primary production increases Ω values between spring and summer, but these increases are partly counteracted by mixing with sea ice melt water and terrestrial river runoff that have low Ω values. While these environmental processes play an important role in creating seasonally low saturation states, ocean uptake of anthropogenic CO2 has shifted Ω values for aragonite to below the saturation horizon in broad regions across the shelf for at least several months each year. Furthermore, we also report that calcite became undersaturated in September of 2009 in the bottom waters over the shelf. The reduction in CaCO3 mineral saturation states could have profound implications for several keystone calcifying species in the Bering Sea, particularly the commercially important crab fisheries.

  6. Interannual variability in stock abundance and body size of Pacific salmon in the central Bering Sea

    NASA Astrophysics Data System (ADS)

    Ishida, Y.; Azumaya, T.; Fukuwaka, M.; Davis, N.

    2002-10-01

    Variability in catch-per-unit-effort (CPUE) and mean body size was examined for pink, chum and sockeye salmon collected with research gillnets in the central Bering Sea in July from 1972 to 2000. The CPUEs for all three species showed significant increasing trends, but with large interannual variability. The CPUE of pink salmon was higher in odd years than in even years, and abruptly increased in the odd years post-1989. Chum salmon also showed odd/even year fluctuations, which were out-of-phase with those of pink salmon. Sockeye salmon showed no biennial such fluctuations. The CPUEs of chum and sockeye salmon were higher during 1979-1984 and 1992-1998, but lower during 1985-1991, especially for younger age group such as ocean age 2 and 3. Data for sea surface temperature (SST) and abundances of chum and sockeye salmon during four periods (1972-1976, 1977-1984, 1985-1990, and 1991-2000) indicated a portion of chum and sockeye salmon were distributed in the northern Gulf of Alaska in 1985-1990, when SST in the Gulf of Alaska was low. However, the fish were more abundant in the Bering Sea in 1977-1984 and 1991-2000 when SST was relatively high in the Gulf of Alaska. Body size of pink salmon showed a significant decreasing trend. Chum and sockeye salmon also showed significant decreasing trends in body size at ocean age 3 and older ages, but not at ocean age 2. Significant negative relationships between CPUE and body size were found within species. No significant correlations were found between an Aleutian low pressure index (ALPI) with CPUE and body size, but the increases in CPUE around the late 1970s and early 1990s may be partly be the result of shifts in the distributions of chum and sockeye salmon caused by SST changes related to the regime shift in 1977 and 1989 identified by the ALPI.

  7. Body size affects individual winter foraging strategies of thick-billed murres in the Bering Sea.

    PubMed

    Orben, Rachael A; Paredes, Rosana; Roby, Daniel D; Irons, David B; Shaffer, Scott A

    2015-11-01

    Foraging and migration often require different energetic and movement strategies. Though not readily apparent, constraints during one phase might influence the foraging strategies observed in another. For marine birds that fly and dive, body size constraints likely present a trade-off between foraging ability and migration as smaller bodies reduce flight costs, whereas larger bodies are advantageous for diving deeper. This study examines individual wintering strategies of deep diving thick-billed murres (Uria lomvia) breeding at three colonies in the south-eastern Bering Sea: St Paul, St George and Bogoslof. These colonies, arranged north to south, are located such that breeding birds forage in a gradient from shelf to deep-water habitats. We used geolocation time-depth recorders and stable isotopes from feathers to determine differences in foraging behaviour and diet of murres during three non-breeding periods, 2008-2011. Body size was quantified by a principal component analysis (wing, culmen, head+bill and tarsus length). A hierarchical cluster analysis identified winter foraging strategies based on individual movement, diving behaviour and diet (inferred from stable isotopes). Structural body size differed by breeding island. Larger birds from St Paul had higher wing loading than smaller birds from St George. Larger birds, mainly from St Paul, dove to deeper depths, spent more time in the Bering Sea, and likely consumed higher trophic-level prey in late winter. Three winter foraging strategies were identified. The main strategy, employed by small birds from all three breeding colonies in the first 2 years, was characterized by high residency areas in the North Pacific south of the Aleutians and nocturnal diving. In contrast, 31% of birds from St Paul remained in the Bering Sea and foraged mainly during the day, apparently feeding on higher trophic-level prey. Throat feather stable isotopes indicated that individuals exhibited flexibility in the use of this

  8. Carbon sources and trophic relationships of ice seals during recent environmental shifts in the Bering Sea.

    PubMed

    Wang, Shiway W; Springer, Alan M; Budge, Suzanne M; Horstmann, Lara; Quakenbush, Lori T; Wooller, Matthew J

    2016-04-01

    Dramatic multiyear fluctuations in water temperature and seasonal sea ice extent and duration across the Bering-Chukchi continental shelf have occurred in this century, raising a pressing ecological question: Do such environmental changes alter marine production processes linking primary producers to upper trophic-level predators? We examined this question by comparing the blubber fatty acid (FA) composition and stable carbon isotope ratios of individual FA (δ¹³CFA) of adult ringed seals (Pusa hispida), bearded seals (Erignathus barbatus), spotted seals (Phoca largha), and ribbon seals (Histriophoca fasciata), collectively known as "ice seals," sampled during an anomalously warm, low sea ice period in 2002-2005 in the Bering Sea and a subsequent cold, high sea ice period in 2007-2010. δ¹³C(FA) values, used to estimate the contribution to seals of carbon derived from sea ice algae (sympagic production) relative to that derived from water column phytoplankton (pelagic production), indicated that during the cold period, sympagic production accounted for 62-80% of the FA in the blubber of bearded seals, 51-62% in spotted seals, and 21-60% in ringed seals. Moreover, the δ¹³CFA values of bearded seals indicated a greater incorporation of sympagic FAs during the cold period than the warm period. This result provides the first empirical evidence of an ecosystem-scale effect of a putative change in sympagic production in the Western Arctic. The FA composition of ice seals showed clear evidence of resource partitioning among ringed, bearded, and spotted seals, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. Despite interannual variability, the FA composition of ringed and bearded seals showed little evidence of differences in diet between the warm and cold periods. The findings that sympagic production contributes significantly to food webs supporting ice seals, and that the contribution apparently is less in

  9. Growth dynamics of saffron cod (Eleginus gracilis) and Arctic cod (Boreogadus saida) in the Northern Bering and Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Helser, Thomas E.; Colman, Jamie R.; Anderl, Delsa M.; Kastelle, Craig R.

    2017-01-01

    Saffron cod (Eleginus gracilis) and Arctic cod (Boreogadus saida) are two circumpolar gadids that serve as critically important species responsible for energy transfer in Arctic food webs of the northern Bering and Chukchi Seas. To understand the potential effects of sea ice loss and warming temperatures on these species' basic life history, information such as growth is needed. Yet to date, limited effort has been dedicated to the study of their growth dynamics. Based on a large sample of otoliths collected in the first comprehensive ecosystem integrated survey in the northern Bering and Chukchi Seas, procedures were developed to reliably estimate age from otolith growth zones and were used to study the growth dynamics of saffron and Arctic cod. Annual growth zone assignment was validated using oxygen isotope signatures in otoliths and otolith morphology analyzed and compared between species. Saffron cod attained larger asymptotic sizes (L∞=363 mm) and achieved their maximum size at a faster rate (K=0.378) than Arctic cod (L∞=209 mm; K=0.312). For both species, regional differences in growth were found (p<0.01). Saffron cod grew to a significantly larger size at age in the northern Bering Sea when compared to the Chukchi Sea, particularly at younger ages. Arctic cod grew to smaller asymptotic size but at faster rates in the more northerly central (L∞=197 mm;K=0.324) and southern Chukchi Sea (L∞=221 mm;K=0.297) when compared to the northern Bering Sea (L∞=266 mm;K=0.171), suggesting a possible cline in growth rates with more northerly latitudes. Comparison of growth to two periods separated by 30 years indicate that both species exhibited a decline in maximum size accompanied by higher instantaneous growth rates in more recent years.

  10. Glacial-to-Holocene evolution of sea surface temperature and surface circulation in the subarctic northwest Pacific and the Western Bering Sea

    NASA Astrophysics Data System (ADS)

    Meyer, Vera D.; Max, Lars; Hefter, Jens; Tiedemann, Ralf; Mollenhauer, Gesine

    2016-07-01

    It has been proposed that North Pacific sea surface temperature (SST) evolution was intimately linked to North Atlantic climate oscillations during the last glacial-interglacial transition. However, during the early deglaciation and the Last Glacial Maximum, the SST development in the subarctic northwest Pacific and the Bering Sea is poorly constrained as most existing deglacial SST records are based on alkenone paleothermometry, which is limited prior to 15 ka B.P. in the subarctic North Pacific realm. By applying the TEXL86 temperature proxy we obtain glacial-Holocene-SST records for the marginal northwest Pacific and the Western Bering Sea. Our TEXL86-based records and existing alkenone data suggest that during the past 15.5 ka, SSTs in the northwest Pacific and the Western Bering Sea closely followed millennial-scale climate fluctuations known from Greenland ice cores, indicating rapid atmospheric teleconnections with abrupt climate changes in the North Atlantic. Our SST reconstructions indicate that in the Western Bering Sea SSTs drop significantly during Heinrich Stadial 1 (HS1), similar to the known North Atlantic climate history. In contrast, progressively rising SST in the northwest Pacific is different to the North Atlantic climate development during HS1. Similarities between the northwest Pacific SST and climate records from the Gulf of Alaska point to a stronger influence of Alaskan Stream waters connecting the eastern and western basin of the North Pacific during this time. During the Holocene, dissimilar climate trends point to reduced influence of the Alaskan Stream in the northwest Pacific.

  11. Geology of Norton Basin and continental shelf beneath northwestern Bering Sea, Alaska

    SciTech Connect

    Fisher, M.A.; Patton, W.W. Jr.; Holmes, M.L.

    1982-03-01

    The rocks that floor the Norton basin and the northwestern Bering Sea are most likely of Precambrian and Paleozoic age, like those rocks that crop out around the basin. A maximum of 6.5 km of mainly Cenozoic strata lie over basement in the basin. On the basis of the geometry of reflections in seismic data, it is believed alluvial fans to be present deep in the basin and to border major basement fault blocks. These fans are the lowest units of the basin fill in many areas and consist of uppermost Cretaceous or lower Paleogene, possibly coal- and volcanic-rich rocks. Mainly clastic nonmarine sedimentary rocks overlie the fan deposits. The Neogene and Quaternary basin rocks apparently were deposited in a marine environment.

  12. Littoral foraging by red phalaropes during spring in the northern Bering Sea

    USGS Publications Warehouse

    Haney, J. Chris; Stone, Amy E.

    1988-01-01

    Phalaropes demonstrate considerable plasticity in their choice of foraging habitats. The Red Phalarope (Phalaropus fulicaria) alternates use of pelagic environments in winter and migration (Taning 1933, Stanford 1953, Briggs et al 1984) with wet tundra habitats during the breeding season (Kistchinski 1975, Mayfield 1979, Ridley 1980). Foods available and taken in littoral zones of the Arctic Ocean in fall have been identified (Conners and Risebrough 1978, Johnson and Richardson 1980), but otherwise little attention has been devoted to the transition between the marine and terrestrial periods of the Red Phalarope’s life history. We report phalarope use of littoral areas during spring in the northern Bering Sea and Kongkok Bay, St. Lawrence Island, Alaska. In addition, we describe phalarope foraging tactics and foods available in the sur zone, emphasizing this form of littoral foraging as an opportunistic and facultative feeding strategy.

  13. Modeling haul-out behavior of walruses in Bering Sea ice

    USGS Publications Warehouse

    Udevitz, M.S.; Jay, C.V.; Fischbach, A.S.; Garlich-Miller, J. L.

    2009-01-01

    Understanding haul-out behavior of ice-associated pinnipeds is essential for designing and interpreting popula-tion surveys and for assessing effects of potential changes in their ice environments. We used satellite-linked transmitters to obtain sequential information about location and haul-out state for Pacific walruses, Odobenus rosmarus divergens (Il-liger, 1815), in the Bering Sea during April of 2004, 2005, and 2006. We used these data in a generalized mixed model of haul-out bout durations and a hierarchical Bayesian model of haul-out probabilities to assess factors related to walrus haul-out behavior, and provide the first predictive model of walrus haul-out behavior in sea ice habitat. Average haul-out bout duration was 9 h, but durations of haul-out bouts tended to increase with durations of preceding in-water bouts. On aver-age, tagged walruses spent only about 17% of their time hauled out on sea ice. Probability of being hauled out decreased with wind speed, increased with temperature, and followed a diurnal cycle with the highest values in the evening. Our haul-out probability model can be used to estimate the proportion of the population that is unavailable for detection in spring surveys of Pacific walruses on sea ice.

  14. Planktonic foraminiferal biostratigraphy and assemblages in the Bering Sea during the Pliocene and Pleistocene: IODP sites U1340 and U1343

    NASA Astrophysics Data System (ADS)

    Husum, Katrine

    2016-03-01

    IODP Site U1340 and Site U1343 in the Bering Sea have been investigated with regard to planktonic foraminifers and fragmentation. The base of Site U1340 dates back to the Early Pliocene and the base of Site U1343 to the Early Pleistocene. Site U1340 is situated at Bowers Ridge, the southern Bering Sea. Site U1343 is situated near the gateway to the Arctic Ocean in the northern Bering Sea. At both sites there are none or very few planktonic foraminifers during the Pliocene and early Pleistocene. After 1.3-1.4 Ma the planktonic foraminifers are continuously present for most of the samples examined. Three stratigraphic events have been identified in this study. The first occurrence (FO) of Neogloboquadrina inglei is observed at 1.4-1.5 Ma, although this event may be affected by poor preservation of foraminifers in older sediments. The observed age of the change in the coiling ratio of Neogloboquadrina pachyderma from right to left at 1.2 Ma agrees with the dating of the same event at the Californian margin. The age of the last occurrence (LO) of N. inglei also seems to match the same event from the Californian margin at 0.7 Ma. This implies that these events are robust regional events for the entire northern Pacific. Multivariate analyses of the quantitative planktonic foraminifer data show three main faunal assemblages. The oldest assemblage from 1.3-1.4 Ma to 1.2 Ma is dominated by N pachyderma s.l. (dex) together with Globigerina bulloides. Other species in this fauna are N. inglei, N. pachyderma s.l. (sin), Globigerina umbilicata and Turborotalita quinqueloba. After 1.2 Ma the faunal assemblage is dominated by N. pachyderma s.l. (sin), but the remaining species are the same as before. At 0.7 Ma N. inglei disappears, whilst the remaining fauna assemblage stays the same, with N. pachyderma s.l. (sin) still dominating, reflecting subpolar-polar conditions. Prior to 1.4-1.3 Ma there are very few or no planktonic foraminifers. Low shell fragmentation and lower TOC

  15. Climate program "stone soup": Assessing climate change vulnerabilities in the Aleutian and Bering Sea Islands of Alaska

    NASA Astrophysics Data System (ADS)

    Littell, J. S.; Poe, A.; van Pelt, T.

    2015-12-01

    Climate change is already affecting the Bering Sea and Aleutian Island region of Alaska. Past and present marine research across a broad spectrum of disciplines is shedding light on what sectors of the ecosystem and the human dimension will be most impacted. In a grassroots approach to extend existing research efforts, leveraging recently completed downscaled climate projections for the Bering Sea and Aleutian Islands region, we convened a team of 30 researchers-- with expertise ranging from anthropology to zooplankton to marine mammals-- to assess climate projections in the context of their expertise. This Aleutian-Bering Climate Vulnerability Assessment (ABCVA) began with researchers working in five teams to evaluate the vulnerabilities of key species and ecosystem services relative to projected changes in climate. Each team identified initial vulnerabilities for their focal species or services, and made recommendations for further research and information needs that would help managers and communities better understand the implications of the changing climate in this region. Those draft recommendations were shared during two focused, public sessions held within two hub communities for the Bering and Aleutian region: Unalaska and St. Paul. Qualitative insights about local concerns and observations relative to climate change were collected during these sessions, to be compared to the recommendations being made by the ABCVA team of researchers. Finally, we used a Structured Decision Making process to prioritize the recommendations of participating scientists, and integrate the insights shared during our community sessions. This work brought together residents, stakeholders, scientists, and natural resource managers to collaboratively identify priorities for addressing current and expected future impacts of climate change. Recommendations from this project will be incorporated into future research efforts of the Aleutian and Bering Sea Islands Landscape Conservation

  16. Corrigendum to ''Climate-mediated changes in zooplankton community structure for the eastern Bering Sea'' [Deep-Sea Res. II 109 (2014) 157-171

    NASA Astrophysics Data System (ADS)

    Eisner, L. B.; Napp, J. M.; Mier, K. L.; Pinchuk, A. I.; Andrews, A. G.

    2016-10-01

    The authors regret that the panels are mislabelled in the caption for Fig. 7. The caption should read, "Untransformed mean zooplankton abundances in the eastern Bering Sea for large taxa in the (A) north (~60-63°N) and (B) south (<~60°N) and for small taxa in the (C) north and (D) south. Bar indicates warm and cold regimes".

  17. Reconstruction of the variability of surface water characteristics and terrigenous input in the North Pacific and Bering Sea: A biomarker approach

    NASA Astrophysics Data System (ADS)

    Meheust, M.; Fahl, K.; Stein, R. H.

    2011-12-01

    Overall goal of the present study of sediment material collected during RV Sonne Cruise 202 (INOPEX) in 2009, is the reconstruction of the variability of and linkages between surface-water characteristic and terrigenous input in the (sub-) polar North Pacific/Bering Sea and their relationship to global climate change, using organic-geochemical proxies (i.e. organic-geochemical bulk parameters and specific biomarkers (TOC, hydrogen indices; long-chain n-alkanes, sterols, alkenones; Uk37 and TEX86-Index; BIT-Index; HBIs, IP25). In Bering Sea surface sediment, both higher total organic carbon (TOC) values and maximum hydrogen index values are observed, suggesting deposition of significant amount of marine organic carbon. The deposition/preservation of marine organic matter in the surface sediments is caused by increased primary production, as reflected in increased chlorophyll a concentrations measured in the surface water. The distribution patterns of the phytoplankton biomarkers dinosterol and brassicasterol support these data as well. The alkenone-based sea-surface temperature (SST) varies between 6°C in the northern part of Bering Sea and 18°C in the North Pacific, close to the Japanese coast, and correlates quite well with the measured SST (extracted from the World Ocean Atlas 2001). From our data, we suggest that the based-alkenone SST mainly reflects summer SST. The alkenone-based SSTs have been compared to temperature estimates obtained with the so-called "TEX 86" Index. Both data sets show quite different temperature distribution patterns, i.e., TEX86 temperatures do not show any correlation with measured SSTs. These differences cannot be explained so far. In order to reconstruct the sea-ice cover, the newly developed so-called "IP25 Index" was used in surface sediment. The absence of IP25 in all studied surface sediments suggests dominantly open-water conditions in the study throughout the year today. The same bulk organic-geochemical and biomarker proxies

  18. On using numerical sea-ice prediction and indigenous observations to improve operational sea-ice forecasts during spring in the bering sea

    NASA Astrophysics Data System (ADS)

    Deemer, Gregory Joseph

    Impacts of a rapidly changing climate are amplified in the Arctic. The most notorious change has come in the form of record-breaking summertime sea-ice retreat. Larger areas of open water and a prolonged ice-free season create opportunity for some industries, but bring new challenges to indigenous populations that rely on sea-ice cover for subsistence. Observed and projected increases in maritime activities require accurate sea-ice forecasts on the weather timescale, which are currently lacking. Motivated by this need, this study explores how new modeling developments and local-scale observations can contribute to improving sea-ice forecasts. The Arctic Cap Nowcast/Forecast System, a research sea-ice forecast model developed by the U.S. Navy, is evaluated for forecast skill. Forecasts of ice concentration, thickness, and drift speed produced by the model from April through June 2011 in the Bering Sea were investigated to determine how the model performs relative to persistence and climatology. Results show that model forecasts can outperform forecasts based on climatology or persistence. However, predictive skill is less consistent during powerful, synoptic-scale events and near the Bering Slope. Forecast case studies in Western Alaska were presented. Community-based observations from recognized indigenous sea-ice experts have been analyzed to gauge the prospect of using local observations in the operational sea-ice monitoring and prediction process. Local observations were discussed in the context of cross-validating model guidance, data sources used in operational ice monitoring, and public sea-ice information products issued by the U.S. National Weather Service. Instrumentation for observing sea-ice and weather at the local scale was supplied to key observers. The instrumentation shows utility in the field and may help translate the context of indigenous observations and provide ground-truth data for use by forecasters.

  19. Feeding ecology of age-0 walleye pollock (Gadus chalcogrammus) and Pacific cod (Gadus macrocephalus) in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Strasburger, Wesley W.; Hillgruber, Nicola; Pinchuk, Alexei I.; Mueter, Franz J.

    2014-11-01

    Walleye pollock (Gadus chalcogrammus) and Pacific cod (Gadus macrocephalus) are of particular economic and ecological importance in the southeastern Bering Sea. The spatial and temporal overlap of early life stages of both species may explain their strongly correlated recruitment trends. Pelagic larvae and juveniles were collected during four research cruises in May, July and September of 2008, an exceptionally cold year, and their stomach contents were examined. Feeding success and diet composition of walleye pollock and Pacific cod were consistently different in spring, summer, and fall. Pacific cod larvae and juveniles always consumed larger and progressively fewer prey items per stomach than walleye pollock; this difference was particularly pronounced in the fall. Our data suggest that co-occurring early life stages of walleye pollock and Pacific cod were dividing prey resources rather than competing for them, at least during the exceptionally cold conditions in 2008 in the southeastern Bering Sea.

  20. Spring and fall phytoplankton blooms in a productive subarctic ecosystem, the eastern Bering Sea, during 1995-2011

    NASA Astrophysics Data System (ADS)

    Sigler, Michael F.; Stabeno, Phyllis J.; Eisner, Lisa B.; Napp, Jeffrey M.; Mueter, Franz J.

    2014-11-01

    The timing and magnitude of phytoplankton blooms in subarctic ecosystems often strongly influence the amount of energy that is transferred through subsequent trophic pathways. In the eastern Bering Sea, spring bloom timing has been linked to ice retreat timing and production of zooplankton and fish. A large part of the eastern Bering Sea shelf (~500 km wide) is ice-covered during winter and spring. Four oceanographic moorings have been deployed along the 70-m depth contour of the eastern Bering Sea shelf with the southern location occupied annually since 1995, the two northern locations since 2004 and the remaining location since 2001. Chlorophyll a fluorescence data from the four moorings provide 37 realizations of a spring bloom and 33 realizations of a fall bloom. We found that in the eastern Bering Sea: if ice was present after mid-March, spring bloom timing was related to ice retreat timing (p<0.001, df=1, 24); if ice was absent or retreated before mid-March, a spring bloom usually occurred in May or early June (average day 148, SE=3.5, n=11). A fall bloom also commonly occurred, usually in late September (average day 274, SE=4.2, n=33), and its timing was not significantly related to the timing of storms (p=0.88, df=1, 27) or fall water column overturn (p=0.49, df=1, 27). The magnitudes of the spring and fall blooms were correlated (p=0.011, df=28). The interval between the spring and fall blooms varied between four to six months depending on year and location. We present a hypothesis to explain how the large crustacean zooplankton taxa Calanus spp. likely respond to variation in the interval between blooms (spring to fall and fall to spring).

  1. Assigning king eiders to wintering regions in the Bering Sea using stable isotopes of feathers and claws

    USGS Publications Warehouse

    Oppel, S.; Powell, A.N.

    2008-01-01

    Identification of wintering regions for birds sampled during the breeding season is crucial to understanding how events outside the breeding season may affect populations. We assigned king eiders captured on breeding grounds in northern Alaska to 3 broad geographic wintering regions in the Bering Sea using stable carbon and nitrogen isotopes obtained from head feathers. Using a discriminant function analysis of feathers obtained from birds tracked with satellite transmitters, we estimated that 88 % of feathers were assigned to the region in which they were grown. We then assigned 84 birds of unknown origin to wintering regions based on their head feather isotope ratios, and tested the utility of claws for geographic assignment. Based on the feather results, we estimated that similar proportions of birds in our study area use each of the 3 wintering regions in the Bering Sea. These results are in close agreement with estimates from satellite telemetry and show the usefulness of stable isotope signatures of feathers in assigning marine birds to geographic regions. The use of claws is currently limited by incomplete understanding of claw growth rates. Data presented here will allow managers of eiders, other marine birds, and marine mammals to assign animals to regions in the Bering Sea based on stable isotope signatures of body tissues. ?? Inter-Research 2008.

  2. Foraging segregation of two congeneric diving seabird species breeding on St. George Island, Bering Sea

    NASA Astrophysics Data System (ADS)

    Kokubun, Nobuo; Yamamoto, Takashi; Sato, Nobuhiko; Watanuki, Yutaka; Will, Alexis; Kitaysky, Alexander S.; Takahashi, Akinori

    2016-04-01

    Subarctic environmental changes are expected to affect the foraging ecology of marine top predators, but the response to such changes may vary among species if they use food resources differently. We examined the characteristics of foraging behavior of two sympatric congeneric diving seabird: common (Uria aalge: hereafter COMUs) and thick-billed (U. lomvia: hereafter TBMUs) murres breeding on St. George Island, located in the seasonal sea-ice region of the Bering Sea. We investigated their foraging trip and flight durations, diel patterns of dive depth, and underwater wing strokes, along with wing morphology and blood stable isotope signatures and stress hormones. Acceleration-temperature-depth loggers were attached to chick-guarding birds, and data were obtained from 7 COMUs and 12 TBMUs. Both species showed similar mean trip duration (13.2 h for COMUs and 10.5 h for TBMUs) and similar diurnal patterns of diving (frequent dives to various depths in the daytime and less frequent dives to shallow depths in the nighttime). During the daytime, the dive depths of COMUs had two peaks in shallow (18.1 m) and deep (74.2 m) depths, while those of TBMUs were 20.2 m and 59.7 m. COMUs showed more frequent wing strokes during the bottom phase of dives (1.90 s-1) than TBMUs (1.66 s-1). Fish occurred more frequently in the bill loads of COMUs (85 %) than those of TBMUs (56 %). The δ15N value of blood was significantly higher in COMUs (14.5 ‰) than in TBMUs (13.1 ‰). The relatively small wing area (0.053 m2) of COMUs compared to TBMUs (0.067 m2) may facilitate their increased agility while foraging and allow them to capture more mobile prey such as larger fishes that inhabit deeper depths. These differences in food resource use may lead to the differential responses of the two murre species to marine environmental changes in the Bering Sea.

  3. Distribution of Arctic and Pacific copepods and their habitat in the northern Bering Sea and Chukchi Sea

    NASA Astrophysics Data System (ADS)

    Sasaki, H.; Matsuno, K.; Fujiwara, A.; Onuka, M.; Yamaguchi, A.; Ueno, H.; Watanuki, Y.; Kikuchi, T.

    2015-11-01

    The advection of warm Pacific water and the reduction of sea-ice extent in the western Arctic Ocean may influence the abundance and distribution of copepods, i.e., a key component in food webs. To understand the factors affecting abundance of copepods in the northern Bering Sea and Chukchi Sea, we constructed habitat models explaining the spatial patterns of the large and small Arctic copepods and the Pacific copepods, separately, using generalized additive models. Copepods were sampled by NORPAC net. Vertical profiles of density, temperature and salinity in the seawater were measured using CTD, and concentration of chlorophyll a in seawater was measured with a fluorometer. The timing of sea-ice retreat was determined using the satellite image. To quantify the structure of water masses, the magnitude of pycnocline and averaged density, temperature and salinity in upper and bottom layers were scored along three axes using principal component analysis (PCA). The structures of water masses indexed by the scores of PCAs were selected as explanatory variables in the best models. Large Arctic copepods were abundant in the water mass with high salinity water in bottom layer or with cold/low salinity water in upper layer and cold/high salinity water in bottom layer, and small Arctic copepods were abundant in the water mass with warm/saline water in upper layer and cold/high salinity water in bottom layers, while Pacific copepods were abundant in the water mass with warm/saline in upper layer and cold/high salinity water in bottom layer. All copepod groups were abundant in areas with deeper depth. Although chlorophyll a in upper and bottom layers were selected as explanatory variables in the best models, apparent trends were not observed. All copepod groups were abundant where the sea-ice retreated at earlier timing. Our study might indicate potential positive effects of the reduction of sea-ice extent on the distribution of all groups of copepods in the Arctic Ocean.

  4. Holocene History of the Bering Sea Bowhead Whale ( Balaena mysticetus) in Its Beaufort Sea Summer Grounds off Southwestern Victoria Island, Western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Dyke, Arthur S.; Savelle, James M.

    2001-05-01

    The fossil remains of 43 bowhead whales were mapped on the raised beaches of western Wollaston Peninsula, Victoria Island, Canadian Arctic, near the historic summer range limit of the Bering Sea stock in the Beaufort Sea. The elevations and radiocarbon ages of the remains demonstrate that the bowhead ranged commonly into the region following the submergence of Bering Strait at ca. 10,000 14C yr B.P. until ca. 8500 14C yr B.P. During the same interval, bowheads ranged widely from the Beaufort Sea to Baffin Bay. Subsequently, no whales reached Wollaston Peninsula until ca. 1500 14C yr B.P. Late Holocene populations evidently were small, or occupations were brief, in comparison to those of the early Holocene. Although the late Holocene recurrence may relate to the expansion of pioneering Thule whalers eastward from Alaska, there are few Thule sites and limited evidence of Thule whaling in the area surveyed to support this suggestion.

  5. Climate change and control of the southeastern Bering Sea pelagic ecosystem

    NASA Astrophysics Data System (ADS)

    Hunt, George L., Jr.; Stabeno, Phyllis; Walters, Gary; Sinclair, Elizabeth; Brodeur, Richard D.; Napp, Jeffery M.; Bond, Nicholas A.

    2002-12-01

    We propose a new hypothesis, the Oscillating Control Hypothesis (OCH), which predicts that pelagic ecosystem function in the southeastern Bering Sea will alternate between primarily bottom-up control in cold regimes and primarily top-down control in warm regimes. The timing of spring primary production is determined predominately by the timing of ice retreat. Late ice retreat (late March or later) leads to an early, ice-associated bloom in cold water (e.g., 1995, 1997, 1999), whereas no ice, or early ice retreat before mid-March, leads to an open-water bloom in May or June in warm water (e.g., 1996, 1998, 2000). Zooplankton populations are not closely coupled to the spring bloom, but are sensitive to water temperature. In years when the spring bloom occurs in cold water, low temperatures limit the production of zooplankton, the survival of larval/juvenile fish, and their recruitment into the populations of species of large piscivorous fish, such as walleye pollock ( Theragra chalcogramma), Pacific cod ( Gadus macrocephalus) and arrowtooth flounder ( Atheresthes stomias). When continued over decadal scales, this will lead to bottom-up limitation and a decreased biomass of piscivorous fish. Alternatively, in periods when the bloom occurs in warm water, zooplankton populations should grow rapidly, providing plentiful prey for larval and juvenile fish. Abundant zooplankton will support strong recruitment of fish and will lead to abundant predatory fish that control forage fish, including, in the case of pollock, their own juveniles. Piscivorous marine birds and pinnipeds may achieve higher production of young and survival in cold regimes, when there is less competition from large piscivorous fish for cold-water forage fish such as capelin ( Mallotus villosus). Piscivorous seabirds and pinnipeds also may be expected to have high productivity in periods of transition from cold regimes to warm regimes, when young of large predatory species of fish are numerous enough to

  6. Phytoplankton distributions and their nutrient environment in the Eastern Bering Sea.

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Nishitani, H.; Narita, H.; Jordan, R. W.

    2004-12-01

    After 1997, coccolithophorids blooms have been frequently observed by research vessels and satellites in the Eastern Bering Sea shelf, where diatoms have previously been dominate. Here, we present CTD, Chl-a, nutrient and phytoplankton data collected during cruises of the T/S Oshoro-Maru and R/V Mirai vessels from 2000 to 2003. Our goal is to refine the relation between phytoplankton distribution and water characteristics, and the controlling features of coccolithophorids blooms in the Eearstern Bering Sea. Samplings were carried out alone 166_E#8249;W from 55_E#8249;N to 59_E#8249;N. For cell counting, seawater samples were filtered through a 25-mm Millipore HA filter, and identification and counting of phytoplankton was performed with a scanning electron microscope. The scale of bloom and abundance of coccolithophorids were different in each year. The most dominant phytoplankton group was coccolithophorids in 2000, which agrees with the large bloom observed by satellite. In 2001, diatoms dominated at 70% and coccolithophorids accounted for 30% at 58, 58.5_E#8249;N. In 2002 and 2003, diatoms dominated at nearly 100% at all stations. Coccolithophorids abundance was nearly halted by pycnocline, since coccolithophorids existed in the middle shelf domain, which is known to be an area of cold-water pool distribution. The difference in density between the surface mixed layer and the cold-water pool gradually increased from 1980 to 2002, that is, seawater stratification in the middle shelf domain was strengthened as the result of the increased surface temperature and decreased salinity that have occurred recently. When stratification strengthens, the supply of nutrients to the surface from the cold-water pool is reduced. Consequently, coccolithophorids take precedence over diatoms in this condition. However, if the decreased salinity in the surface water depended on the increased river discharge, then the nutrients in the surface water would increase. River discharge has

  7. Results of the US contribution to the joint US/USSR Bering Sea experiment. [atmospheric circulation and sea ice cover

    NASA Technical Reports Server (NTRS)

    Campbell, W. J.; Chang, T. C.; Fowler, M. G.; Gloersen, P.; Kuhn, P. M.; Ramseier, R. O.; Ross, D. B.; Stambach, G.; Webster, W. J., Jr.; Wilheit, T. T.

    1974-01-01

    The atmospheric circulation which occurred during the Bering Sea Experiment, 15 February to 10 March 1973, in and around the experiment area is analyzed and related to the macroscale morphology and dynamics of the sea ice cover. The ice cover was very complex in structure, being made up of five ice types, and underwent strong dynamic activity. Synoptic analyses show that an optimum variety of weather situations occurred during the experiment: an initial strong anticyclonic period (6 days), followed by a period of strong cyclonic activity (6 days), followed by weak anticyclonic activity (3 days), and finally a period of weak cyclonic activity (4 days). The data of the mesoscale test areas observed on the four sea ice option flights, and ship weather, and drift data give a detailed description of mesoscale ice dynamics which correlates well with the macroscale view: anticyclonic activity advects the ice southward with strong ice divergence and a regular lead and polynya pattern; cyclonic activity advects the ice northward with ice convergence, or slight divergence, and a random lead and polynya pattern.

  8. Spring plankton dynamics in the Eastern Bering Sea, 1971-2050: Mechanisms of interannual variability diagnosed with a numerical model

    NASA Astrophysics Data System (ADS)

    Banas, Neil S.; Zhang, Jinlun; Campbell, Robert G.; Sambrotto, Raymond N.; Lomas, Michael W.; Sherr, Evelyn; Sherr, Barry; Ashjian, Carin; Stoecker, Diane; Lessard, Evelyn J.

    2016-02-01

    A new planktonic ecosystem model was constructed for the Eastern Bering Sea based on observations from the 2007-2010 BEST/BSIERP (Bering Ecosystem Study/Bering Sea Integrated Ecosystem Research Program) field program. When run with forcing from a data-assimilative ice-ocean hindcast of 1971-2012, the model performs well against observations of spring bloom time evolution (phytoplankton and microzooplankton biomass, growth and grazing rates, and ratios among new, regenerated, and export production). On the southern middle shelf (57°N, station M2), the model replicates the generally inverse relationship between ice-retreat timing and spring bloom timing known from observations, and the simpler direct relationship between the two that has been observed on the northern middle shelf (62°N, station M8). The relationship between simulated mean primary production and mean temperature in spring (15 February to 15 July) is generally positive, although this was found to be an indirect relationship which does not continue to apply across a future projection of temperature and ice cover in the 2040s. At M2, the leading direct controls on total spring primary production are found to be advective and turbulent nutrient supply, suggesting that mesoscale, wind-driven processes—advective transport and storminess—may be crucial to long-term trends in spring primary production in the southeastern Bering Sea, with temperature and ice cover playing only indirect roles. Sensitivity experiments suggest that direct dependence of planktonic growth and metabolic rates on temperature is less significant overall than the other drivers correlated with temperature described above.

  9. Microplastic pollution in deep-sea sediments.

    PubMed

    Van Cauwenberghe, Lisbeth; Vanreusel, Ann; Mees, Jan; Janssen, Colin R

    2013-11-01

    Microplastics are small plastic particles (<1 mm) originating from the degradation of larger plastic debris. These microplastics have been accumulating in the marine environment for decades and have been detected throughout the water column and in sublittoral and beach sediments worldwide. However, up to now, it has never been established whether microplastic presence in sediments is limited to accumulation hot spots such as the continental shelf, or whether they are also present in deep-sea sediments. Here we show, for the first time ever, that microplastics have indeed reached the most remote of marine environments: the deep sea. We found plastic particles sized in the micrometre range in deep-sea sediments collected at four locations representing different deep-sea habitats ranging in depth from 1100 to 5000 m. Our results demonstrate that microplastic pollution has spread throughout the world's seas and oceans, into the remote and largely unknown deep sea.

  10. Cooling in the western Bering Sea in 1999: quick propagation of La Niña signal or compensatory processes effect?

    NASA Astrophysics Data System (ADS)

    Radchenko, V. I.; Khen, G. V.; Slabinsky, A. M.

    In 1999, synoptic and hydrological conditions in the western Bering Sea were characterized by negative SST and air temperature anomalies, extensive ice coverage and late melting. Biological processes were also delayed. In 1999, the average zooplankton biomass was 1.76 g/m 3, approximately half the average 3.07 g/m 3 in 1998. Pacific salmon migrated to the northeastern Kamchatka streams two weeks later. This contrasts with 1997 (spring and summer) and 1998 (summer) when positive SST anomalies were widely distributed throughout the northwestern Bering Sea shelf. Since the second half of the 1990s, seasonal atmospheric processes developed over the western Bering Sea that were similar to those of the cold decades of the 1960-1970s. A meridional atmospheric circulation pattern began to replace zonal transport. Colder Arctic air masses have shifted over the Bering Sea region and shelf water temperatures have cooled considerably with the weakening of zonal atmospheric circulation. Temperature decreased in the cold intermediate layer during its renewal in winter. Besides, oceanic water inflow intensified into the Bering Sea in intermediate layers. Water temperature warmed to 4°C and a double temperature maximum existed in the warm intermediate layer in late summer in both 1997 and 1998. Opposing trends of cold water temperature and a warm intermediate layer led to an increase of vertical gradients in the main thermocline and progressing frontogenesis. It accelerates frontal transport and can be regarded as a chief cause of increased water exchange with the Pacific Ocean.

  11. Origins of the subsurface ammonium maximum in the Southeast Bering Sea

    NASA Astrophysics Data System (ADS)

    Mordy, Calvin W.; Stabeno, Phyllis J.; Righi, Dylan; Menzia, Frederick A.

    2008-08-01

    In the Bering Sea, it has long been argued that ammonium-rich bottom water from the middle shelf of Bristol Bay is tidally diffused seaward resulting in a mid-depth ammonium tongue over the outer shelf. Weak horizontal mean flows in the region (relative to an especially strong tidal component) support this contention. We examined the distribution of ammonium further north in the vicinity of the Pribilof Islands. On the middle shelf, bottom waters had concentrations of 4-7 μmol kg -1, and over the outer shelf there was a mid-depth ammonium tongue. Optimal multiparameter analysis of hydrographic data suggested that bottom waters from the middle shelf were prevalent across the outer shelf, and could account for this ammonium tongue. Drifter tracks demonstrated that middle shelf water was incorporated into a westward flow along the shelf break south of St. George Island, and mean flows derived from several decades of drifter tracks also show prominent cross-shelf advection in the region. This was consistent with a scalar argument suggesting that, in the vicinity of the Pribilof Islands, the seaward movement of middle shelf water, and loss of nitrogen over the middle shelf, was the result of advection rather than tidally driven lateral diffusion.

  12. Tritium and plutonium in waters from the Bering and Chukchi Seas

    USGS Publications Warehouse

    Landa, E.R.; Beals, D.M.; Halverson, J.E.; Michel, R.L.; Cefus, G.R.

    1999-01-01

    During the summer of 1993, seawater in the Bering and Chukchi Seas was sampled on a joint Russian-American cruise [BERPAC] of the RV Okean to determine concentrations of tritium, 239Pu and 240Pu. Concentrations of tritium were determined by electrolytic enrichment and liquid scintilation counting. Tritium levels ranged up to 420 mBq L-1 showed no evidence of inputs other than those attribute atmospheric nuclear weapons testing. Plutonium was recovered from water samples by ferric hydroxide precipitation, and concentrations were determined by thermal ionization mass spectrometry. 239+240Pu concentrations ranged from <1 to 5.5 [mu]Bq L-1. These concentrations are lower than those measured in water samples from other parts of the ocean during the mid-1960's to the late 1980's. The 240Pu:239Pu ratios, although associated with large uncertainties, suggest that most of the plutonium is derived from world-wide fallout. As points of comparison, the highest concentrations of tritium and plutonium observed here were about five orders of magnitude lower than the maximum permissible concentrations allowed in water released to the off-site environs from licensed nuclear facilities in the United States. This study and others sponsored by the International Atomic Energy Agency and the Office of Naval Research's Arctic Nuclear Waste Assessment Program are providing data for the assessment of potential radiological impacts in the Arctic regions associated with nuclear waste disposal by the former Soviet Union.

  13. The plume of the Yukon River in relation to the oceanography of the Bering Sea

    NASA Technical Reports Server (NTRS)

    Dean, Kenneson G.; Mcroy, C. Peter; Ahlnas, Kristina; Springer, Alan

    1989-01-01

    The ecosystem of the northern Bering-Sea shelf was studied using data from the NOAA Very High Resolution Radiometer and AVHRR and the Landsat MSS and Thematic Mapper (TM) in conjunction with shipboard measurements. Emphasis was placed on the influence of the Yukon River on this inner shelf environment and on the evaluation of the utility of the new Landsat TM data for oceanography. It was found that the patterns of water mass distribution obtained from satellite images agreed reasonably well with the areal patterns of temperature, salinity, and phytoplankton distributions. The AVHRR, MSS, and TM data show that the Yukon-River discharge is warmer and more turbid than the surrounding coastal water that originates to the south; thus, the Yukon water contributes to the higher temperatures and lower transmissivity of the coastal water. The high resolution of the TM thermal IR band made it possible to observe complex patterns and structures in the surface water that could not be resolved on previous data sets.

  14. Seasonal Storminess in the North Pacific, Bering Sea, and Alaskan Regions

    NASA Astrophysics Data System (ADS)

    Shippee, N. J.; Atkinson, D. E.; Walsh, J. E.; Partain, J.; Gottschalck, J.; Marra, J.

    2012-12-01

    Annually, extra-tropical cyclones present a high impact natural hazard to the North Pacific, Bering Sea, and Alaskan regions. In these regions, extensive subsistence and commercial fishing, new oil and gas field development, tourism, growing interest in and exploitation of new commercial shipping potential, and increasing military and Coast Guard activity, all represent potential parties impacted by storms in these waters. It is of interest to many parties to begin developing capacity to provide some indication of storm activity at a monthly- to seasonal-outlook (30 to 90 days) timeframe. Using storm track data from NOAA's Climate Prediction Center for the North Pacific and Alaskan region, an experimental seasonal storminess outlook product, using eigen-based methods similar to the operational seasonal temperature and precipitation products currently produced at NOAA CPC, has been created and tested in hindcast mode using predicted states of ENSO, the Pacific Decadal Oscillation (PDO), the Pacific-North American Pattern (PNA), and the Arctic Oscillation (AO). A sample of the seasonal storminess outlook product will be shown along with a discussion of the utility of individual teleconnection patterns in the generation of the product.

  15. Recruitment variation of eastern Bering Sea crabs: Climate-forcing or top-down effects?

    NASA Astrophysics Data System (ADS)

    Zheng, Jie; Kruse, Gordon H.

    2006-02-01

    During the last three decades, population abundances of eastern Bering Sea (EBS) crab stocks fluctuated greatly, driven by highly variable recruitment. In recent years, abundances of these stocks have been very low compared to historical levels. This study aims to understand recruitment variation of six stocks of red king ( Paralithodes camtschaticus), blue king ( P. platypus), Tanner ( Chionoecetes bairdi), and snow ( C. opilio) crabs in the EBS. Most crab recruitment time series are not significantly correlated with each other. Spatial distributions of three broadly distributed crab stocks (EBS snow and Tanner crabs and Bristol Bay red king crab) have changed considerably over time, possibly related in part to the regime shift in climate and physical oceanography in 1976-1977. Three climate-forcing hypotheses on larval survival have been proposed to explain crab recruitment variation of Bristol Bay red king crab and EBS Tanner and snow crabs. Some empirical evidence supports speculation that groundfish predation may play an important role in crab recruitment success in the EBS. However, spatial dynamics in the geographic distributions of groundfish and crabs over time make it difficult to relate crab recruitment strength to groundfish biomass. Comprehensive field and spatially explicit modeling studies are needed to test the hypotheses and better understand the relative importance and compound effects of bottom-up and top-down controls on crab recruitment.

  16. Use of nearshore and estuarine areas by gray whales (Eschrichtius robustus) in the eastern Bering Sea

    USGS Publications Warehouse

    Gill, Robert E.; Hall, John D.

    1983-01-01

    During spring aerial surveys of the coast of the southeastern Bering Sea significant numbers of gray whales were seen in nearshore waters along the north side of the Alaska Peninsula. Many (50-80%) of these animals were observed surfacing with mud trails or lying on their sides, characteristics both associated with feeding. A migration route close to shore (within 1-2 km) was used until whales neared Egegik Bay, where they began to head west 5-8 km offshore, across northern Bristol Bay. Smaller numbers of gray whales were present throughout summer in nearshore waters and estuaries along the north side of the Alaska Peninsula. At Nelson Lagoon gray whales normally used the lagoon in spring, were absent during early summer, returned in mid-summer, and then were present until late November when they departed for the wintering grounds. Gray whales were present in the lagoon most often during periods of peak tidal flow; those that appeared to be feeding were oriented into the current. Three behaviors that appeared to be associated with feeding were observed: side-feeding from a stationary position within shallow waters of lagoon channels, diving within the lagoon and in nearshore waters, and elliptical side-feeding in the surf zone along the outer coast. Large crustaceans of the genus Crangon were available to and probably eaten by gray whales at Nelson Lagoon.

  17. Change in the Nd isotopic composition of the bottom water and detrital sediments on the Bering Slope over the last 500 kyrs with implications for the formation of the North Pacific Intermediate Water

    NASA Astrophysics Data System (ADS)

    Jang, K.; Huh, Y.; Han, Y.

    2015-12-01

    The Bering Sea is a potential location for the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) and may play an important role in the global heat distribution. We reconstructed the neodymium isotopic ratio (ɛNd) of authigenic Fe-Mn oxide coatings and detrital sediments on the Bering Slope (IODP Expedition 323 site U1345; water depth 1008 m) over the last 500 kyrs. The ɛNd is a quasi-conservative water mass tracer. We compared three different leaching techniques to assure that authigenic signals are captured without contamination from terrigenous sources: (1) leaching (3 hours) with 0.02 M hydroxylamine hydrochloride (HH) in 25% buffered acetic acid after decarbonation; sediment/solution (v/v) > 10, (2) leaching (1 hour) with 0.02 M HH in 25% buffered acetic acid without decarbonation; sediment/solution ~ 1, and (3) leaching (1 hour) with 0.005 M HH in 1.5% buffered acetic acid-0.003 M Na-EDTA without decarbonation; sediment/solution > 40. The low Al concentrations and less radiogenic ɛNdvalues indicated that method (2) is the most appropriate leaching process. The average ɛNd of the authigenic fraction over the last 500 kyrs is -3.3 ± 0.9 (1σ, n=38), with large temporal fluctuations. The ɛNd of authigenic and detrital fractions are well correlated (r2 ~ 0.66), suggesting that the bottom water composition in the Bering Sea was governed by terrigenous inflow from surrounding areas. Radiogenic ɛNd peaks (up to -1.9) seem to be influenced by radiogenic water inflow from the the Kamchatka or Aluetian arcs. The high bulk density and low b* values imply higher terrigenous versus biological contribution and enhanced sea ice formation. Subsequent brine formation would have triggered sinking of radiogenic surface water, forming the NPIW. On the other hand, non-radiogenic ɛNd troughs (down to -5.3) are observed at times of low bulk density and high b* values. We presume higher biological productivity which is supported by the high opal content at

  18. Potential effects of temperature on the benthic infaunal community on the southeastern Bering Sea shelf: Possible impacts of climate change

    NASA Astrophysics Data System (ADS)

    Coyle, K. O.; Konar, B.; Blanchard, A.; Highsmith, R. C.; Carroll, J.; Carroll, M.; Denisenko, S. G.; Sirenko, B. I.

    2007-11-01

    In the late 1950s, Soviet researchers collected benthic infaunal samples from the southeastern Bering Sea shelf. Approximately 17 years later, researchers at University of Alaska Fairbanks also sampled the region to assess infaunal biomass and abundance. Here, the two data sets were examined to document patterns and reveal any consistent differences in infaunal biomass among major feeding groups between the two time periods. No significant differences in the geometric mean biomass of all taxa pooled were indicated between the two study periods (1958-1959=49.1 g m -2; 1975-1976=60.8 g m -2; P=0.14); however, significant differences were observed for specific functional groups, namely carnivores, omnivores and surface detritivores. Of the 64 families identified from both data sets from all functional groups, 21 showed statistically significant ( P⩽0.05) differences in mean biomass. Of the 21 families showing significant differences, 19 (91%) of the families had higher mean biomass in the 1975-1976 data set. The above differences suggest a trend toward higher overall infaunal biomass for specific functional groups during mid 1970s compared with the late 1950s. Temperature measurements and literature data indicate that the mid-1970s was an unusually cold period relative to the period before and after, suggesting a mechanistic link between temperature changes and infaunal biomass. Food-web relationships and ecosystem dynamics in the southeastern Bering Sea indicate that during cold periods, infaunal biomass will be elevated relative to warm periods due to elevated carbon flux to the benthos and exclusion of benthic predators on infaunal invertebrates by the cold bottom water on the shelf. As long-term observations of temperature and sea-ice cover indicate a secular warming trend on the Bering Sea shelf, the potential changes in food-web relationships could markedly alter trophic structure and energy flow to apex consumers, potentially impacting the commercial, tourist

  19. Coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Mathis, Jeremy T.; Cross, Jessica N.; Bates, Nicholas R.

    2011-02-01

    Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (Ω) of the two most important carbonate minerals, calcite (Ωcalcite) and aragonite (Ωaragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9-8.1 and Ωcalcite and Ωaragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and Ωcalcite and Ωaragonite. However, Ωcalcite and Ωaragonite decreased by ˜0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, Ωaragonite decreased by ˜0.35 and became highly undersaturated. The observed suppression and undersaturation of Ωcalcite and Ωaragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.

  20. Oxygen isotopic composition of bottom seawater and tunicate cellulose used as indicators of water masses in the northern Bering and Chukchi Seas

    SciTech Connect

    Grebmeier, J.M. ); Cooper, L.W.; DeNiro, M.J. )

    1990-07-01

    Oxygen isotopic composition of bottom seawater and tunicate cellulose were used as short-term and long-term indicators, respectively, of water-mass characteristics in the northern Bering and Chukchi Seas. Oxygen isotopic composition of northeastern Bering Sea waters is influenced by Yukon River inflows of {sup 18}O-depleted continental water mixing with relatively {sup 18}O-enriched waters contributed by the Anadyr Current. Tunicate cellulose sampled under Alaska coastal water is more depleted in {sup 18}O than that collected under Bering shelf and Anadyr waters, which reflects the oxygen isotopic composition of these waters. Tunicate cellulose collected under the mixed Bering shelf water displays intermediate {delta} {sup 18}O values. Oxygen isotopic analyses of bottom seawater were used to determine the spatial location and influence of continental and coastal-derived precipitation and of sea-ice formation on water-mass structure on the continental shelf of the northern Bering and Chukchi Seas. Results indicate that the oxygen isotopic composition of tunicate cellulose, averaged over multiple seasons, may serve as a long-term biochemical indicator of water-mass patterns in ice-covered polar regions where continuous sampling is impractical.

  1. A comparison of ship and Coastal Zone Color Scanner mapped distribution of phytoplankton in the southeastern Bering Sea

    NASA Technical Reports Server (NTRS)

    Mcclain, C. R.; Sambrotto, R. N.; Ray, G. C.; Muller-Karger, F. E.

    1990-01-01

    Twenty-one Coastal Zone Color Scanner (CZCS) images of the southeastern Bering Sea are examined in order to map the near-surface distribution of phytoplankton during 1979 and 1980. The information is compared with the mesoscale (100-1000 km) distribution of phytoplankton inferred from pooled ship sampling obtained during the Processes and Resources of the Bering Shelf (PROBES) intensive field study during the late 1970s and early 1980s. The imagery indicates that open-water phytoplankton blooms occur first in late April in coastal waters, peak in early May over the middle shelf, and decay rapidly afterwards, reaching concentration minima in June in both regions. These patterns show that the earlier ship observations are valid for most of the eastern Bering shelf. A very tight correlation is found between the PROBES surface chlorophyll a concentrations and mean mixed-layer chlorophyll concentrations. The significant discrepancies between CZCS and ship-based chlorophyll estimates may be due to aliasing in time by the CZCS. It is concluded that neither satellite nor ship alone can do an adequate job of characterizing the physics or biological dynamics of the ocean.

  2. Millennial-scale variability of marine productivity and terrigenous matter supply in the western Bering Sea over the past 180 kyr

    NASA Astrophysics Data System (ADS)

    Riethdorf, J.-R.; Nürnberg, D.; Max, L.; Tiedemann, R.; Gorbarenko, S. A.; Malakhov, M. I.

    2013-06-01

    We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach, our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas export production was low. Minor increases in marine productivity occurred during intervals of Marine Isotope Stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. The terrigenous material is suggested to be derived from continental sources on the eastern Bering Sea shelf and to be subsequently transported via sea ice, which is likely to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait is considered to have had an additional impact. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard-Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.

  3. Assessment of high latitude variability and extreme events in the Bering Sea as simulated by a global climate model

    NASA Astrophysics Data System (ADS)

    Walston, Joshua M.

    Atmospheric and Oceanic observations of the Arctic and Subarctic are relatively sparse and hinder our ability to analyze short term variability and long-duration anomalies of physical and biological variables over decadal time scales. Earth System Models (ESM's), such as the Community Earth System Model (CESM1), represent a useful tool to advance the understanding and the predictive potential of large-scale shifts in the climate and climate related impacts. This thesis initially focuses on assessing the skill of the Community Climate System Model (CCSM4), to capture natural variability of the climate system. Subsequently, I examine the impacts of variability and seasonal-scale extremes of the physical environment on the marine ecosystem of the eastern Bering Sea as simulated by an earth system model, the CESM1, which includes the CCSM4 and earth system elements. A performance assessment of key atmospheric components (air temperature, sea level pressure, wind speed and direction) simulated by the CCSM4 over the Bering Sea and Arctic domains suggests a general improvement in model predictions at high latitudes relative to the model's predecessor, the CCSM3. However, several shortcomings, with possible implications for marine ecosystem modeling, still remain in this version of the CCSM. The most important of which includes an under-simulated Siberian High and a large northwest displacement of the Aleutian Low resulting in a negative bias of up to 8 hPa over the Bering Sea. The simulated inter-annual variability of surface air temperature and sea level pressure over the Bering Sea was found to exceed observed variability by ˜1.5 to 2 times. The displaced pressure systems and increased variability could have important ramifications for modeling efforts that use CCSM atmospheric output as drivers for marine ecosystem studies. When the CCSM was combined with other earth system elements to form the CESM, the coupled model was found to simulate strong linear relationships

  4. Geochemical characters of Quaternary tephra beds and their stratighraphic position in the sedimentary core drilled at the site U1343 in the central Bering Sea

    NASA Astrophysics Data System (ADS)

    Aoki, K.; Asahi, H.; Nagatsuma, Y.; Kurihara, K.; Fukuoka, T.; Sakamoto, T.; Iijima, K.

    2012-12-01

    The project IODP exp.323 in the Bering Sea focused on analyzing long-term ocean and climate trends during 5 Ma, and drilled seven sites (sites 1339-1345). Up to now, the studies of long-term tephrochronology in this area are very rare, though a part of histories of several volcanoes and late Pleistocene to Holocene volcanisms and studies for geochemistry of magma were reported in detail. Our objectives are to reveal how many widespread tephras are found in the Bering Sea and which of volcanoes or volcanic zones provided them. First of all, we analyzed forty-eight tephra samples in the sedimentary core collected at site U1343, near the Bering self sloop. Sediments in site U1343 (57°33.4'N, 175°49.0'E, water depth 1956 mbsf, core length 779.18 m) include three paleomagnetic events (the BM boundary;0.788 Ma, Jaramillo; 0.998 Ma, Cobb Mountain;1.173 Ma). The bottom datum event is reported as 2.0-2.2 Ma (diatom) at 716.4 m. All tephra samples were washed by flesh water and decanting, dried up naturally, sieved by the mesh of dia.250, 125 and 63 micrometer. We observed every tephra under the binocular/polarizing microscopes, and analyzed major-element composition of volcanic glass shards by EPMA (10nA, 15kV, probe dia.10 micrometer). All samples include many kinds of volcanic glass shards (color: colorless to dark brown, form: bubble-wall type, pumice type, fiber type). Diameter of grain size is normally less 125 micrometer, and volcanic glass size in some layers is concentrated in the less 63 micrometer. Thickness of tephra samples is approximately 0.5 cm to 4 cm. In the basis of geochemicalc analysis of volcanic glass shards in 48 samples, though every sample includes volcanic glass shards, we can distinguish the two groups roughly; glass-rich samples (31 samples) and contaminated samples (17 samples). Contaminated samples include course sands (lithic fragments, rounded minerals, fossil fragments), besides volcanic glass shards. Number of contaminated samples

  5. Metals in diet of Bering Sea walrus: Mya sp. as a possible transmitter of elevated cadmium and other metals

    USGS Publications Warehouse

    Miles, A. Keith; Hills, Susan

    1994-01-01

    Elevated levels of cadmium in Pacific walrus (Odobenus rosmarus divergens) and northern fur seals (Callorhinus ursinus) have been reported in populations from the Bering Sea (Goldblatt & Anthony, 1983; Taylor et al., 1989). Russian and US authorities are concerned because of the possible health hazards from consuming pinniped meat harvested for subsistence peoples. The effects of cadmium on marine mammals have not been determined, but high concentrations of this element in humans and laboratory animals have been correlated with renal, skeletal, and biochemical dysfunctions (Friberg et al., 1986).

  6. Migration dynamics of Pacific herring ( Clupea pallasii) and response to spring environmental variability in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Tojo, Naoki; Kruse, Gordon H.; Funk, Fritz C.

    2007-11-01

    In the southeastern Bering Sea, Pacific herring ( Clupea pallasii) migrate from the Pribilof Islands region where they overwinter, to the Alaska coast where they spawn in spring. The migration sustains a nearshore commercial fishery that targets roe-bearing females just prior to spawning. Herring also are taken as bycatch in groundfish trawl fisheries, where time and area closures in these fisheries are triggered by herring bycatch caps. Using herring bycatch data collected since the 1970s by National Marine Fisheries Service (NMFS) observers aboard groundfish fishing vessels, a retrospective analysis was conducted to describe the seasonal migration pattern of Pacific herring in the southeastern Bering Sea and to study its spatial and temporal variability. Observed changes in herring catch per unit of effort were compared with variability in climate and oceanographic conditions. The seasonal migration is complex, but annual shifts in migration routes and a possible northward shift of the overwintering grounds was identified. Pre-spawning herring aggregated in different areas depending on whether spawning occurred early or late in spring. The thermal structure of the ocean around the ice edge appears to influence herring migration timing and route as well as spawning date. Thus, on the basis of recent changes in sea-ice extent and duration, we suggest that the herring bycatch savings area that was developed from data collected in the 1980s should be revised to reflect prevailing conditions.

  7. Echinobothrium raschii n. sp. (Cestoda: Diphyllidea) from Rhinoraja longi (Chondrichthyes, Rajoidei) in the Bering Sea.

    PubMed

    Campbell, R A; Andrade, M

    1997-02-01

    Echinobothrium raschii n. sp. from the spiral intestine of Rhinoraja longi in the Bering Sea, off the Aleutian Islands of Alaska is described. On the basis of the armature of the rostellum and cephalic peduncle the new species most closely resembles Echinobothrium acanthinophyllum, Echinobothrium acanthocolle, Echinobothrium coronatum and Echinobothrium helmymohamedi. Echinobothrium raschii n. sp. can be differentiated from all but E. coronatum by the possession of a continuous row of 27-36 lateral hooklets per side on the scolex and 21-26 spines per row on the cephalic peduncle. In E. acanthinophyllum there are fewer spines per row on the cephalic peduncle (13) and only 2 groups of 4 lateral hooklets per side instead of a continuous row of lateral hooklets; E. acanthocolle bears only 5 spines per row on the cephalic peduncle and has no lateral hooklets; E. helmymohamedi has 10-12 spines per row on the cephalic peduncle and bears no lateral hooklets. Echinobothrium raschii n. sp. can be distinguished from E. coronatum by number of spines per row on the cephalic peduncle (average 24 vs. 32) and testes number (17-23 vs. 9-11). The combined characters of 2 groups of 23-25 large apical hooks, a continuous alternating row of 27-36 hooklets on each side of the scolex between the groups of large apical hooks, 21-26 spines per row on the cephalic peduncle, and 17-23 testes per segment differentiates E. raschii from all other species of Echinobothrium. The prevalence of infection was 50% and mean intensity of infection was 8.7 worms per host. The current status of the genus Echinobothrium is discussed and a tabulation of the species presented.

  8. Biomass, growth, and development of populations of herbivorous zooplankton in the southeastern Bering Sea during spring

    SciTech Connect

    Vidal, J.; Smith, S.L.

    1985-09-01

    Two distinct communities of herbivorous zooplankton, separated by an oceanographic front, inhabit the continental shelf and slope of the southeastern Bering Sea during spring. The community over the outer shelf and slope is dominated by populations of large-sized oceanic copepods (mainly Neocalanus ssp.) that develop early in spring and attain maximum biomass and growth rates by mid- to late spring. Total biomass and growth rates of herbivores follow the spring outburst of phytoplankton; during April and May biomass increases from less than or equal to1 to approx.14 g C m/sup -2/ on the slope and to approx.10 g C m/sup -2/ on the outer shelf, and maximum growth rates >500 and approx.300 mg C m/sup -2/ day/sup -1/ occure on the slope and outer shelf, respectively in May. The dominant species, N. plumchrus, grows from copepodid I and V between late March and early May, and after attaining maximum body weight in late May and early June it begins its downward migration. The inshore community on the middle shelf is dominated by the euphausiid Thysanoessa raschi in April and May and by the copepod Calanus marshallae in late May and early June. Total biomass (less than or equal to g C m/sup -2/) and growth rates (less than or equal to50 mg C m/sup -2/) of the inshore community are substantially lower than those of the offshore community and show a delayed response to the spring bloom of phytoplankton; both biomass and growth rates increase about one month after the bloom. Small herbivorous copepods contributed little to the total biomass and growth rates of either community and the cumulative community growth rates during April and May decreases from 18.3 g C m/sup -2/ on the slope to 2.5 g C m/sup -2/ on the middle shelf. 79 refs., 15 figs., 7 tabs.

  9. Phytoplankton and sediments in Yellow Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sediment and phytoplankton cloud the waters of the Yellow Sea in this true-color MODIS image acquired March 18, 2002. The swirls of sediment appear as a murky brownish blue color, while the phytoplankton are purely blue green and are concentrated around the small island in the lower right corner of the image.

  10. Mass and energy transfer to seabirds in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Schneider, David C.; Hunt, George L.; Harrison, Nancy M.

    It has been hypothesized that differentiation in food web structure occurs across the Bering Sea continental shelf as a result of seasonal differentiation of water masses. We tested this idea using an apex predator, pelagic birds. Seasonal abundance of birds in central Bristol Bay was estimated from counts made while underway between hydrographic stations. Prey and body mass were determined from birds collected at sea. Daily intake was estimated as an allometric function of body mass. Annual occupancy was estimated as the integral of a normal curve fit to seasonal data. Estimated carbon flux to seabirds in the middle domain was 0.12 gC m -2 y -1 in 1980, 0.18 gC m -2 y -1 in 1981. Carbon flux to seabirds in the adjacent waters of the outer shelf domain was 1.8 times higher than in the middle domain in 1980, 1.6 times higher in 1981. Carbon flux to seabirds in the inner domain was 1.2 times higher than in the middle domain in 1980, and 3.3 times higher in 1981. Carbon flux to seabirds in the outer domain was due primarily to non-diving species, principally northern fulmars ( Fulmarus glacialis) during the summer and autumn, and Larus gulls in the autumn and winter. Flux to seabirds in the inner domain was due to diving birds, principally murres ( Uria sp.) in the spring and shearwaters ( Puffinus sp.) during the summer. The euphausiid Thysanoessa raschii was the primary food source of shearwaters in shallow waters of the inner shelf domain. A more diverse set of prey, including squid, jellyfish, hyperiids, and fish, was taken by shearwaters and fulmars in the deeper waters of the outer and middle shelf domains. This result suggests that prey diversity is higher in seasonally stratified waters of outer Bristol Bay than in mixed waters of inner Bristol Bay. Greater energy flux to diving species in shallow water, and greater energy flux to non-divers in deep water may be a function of topographic control of prey patchiness.

  11. Modeling marine protected areas for threatened eiders in a climatically changing Bering Sea.

    PubMed

    Lovvorn, James R; Grebmeier, Jacqueline M; Cooper, Lee W; Bump, Joseph K; Richman, Samantha E

    2009-09-01

    Delineating protected areas for sensitive species is a growing challenge as changing climate alters the geographic pattern of habitats as well as human responses to those shifts. When human impacts are expected within projected ranges of threatened species, there is often demand to demarcate the minimum habitat required to ensure the species' persistence. Because diminished or wide-ranging populations may not occupy all viable (and needed) habitat at once, one must identify thresholds of resources that will support the species even in unoccupied areas. Long-term data on the shifting mosaic of critical resources may indicate ranges of future variability. We addressed these issues for the Spectacled Eider (Somateria fischeri), a federally threatened species that winters in pack ice of the Bering Sea. Changing climate has decreased ice cover and severely reduced the eiders' benthic prey and has increased prospects for expansion of bottom trawling that may further affect prey communities. To assess long-term changes in habitats that will support eiders, we linked data on benthic prey, sea ice, and weather from 1970 to 2001 with a spatially explicit simulation model of eider energy balance that integrated field, laboratory, and remote-sensing studies. Areas estimated to have prey densities adequate for eiders in 1970-1974 did not include most areas that were viable 20 years later (1993-1994). Unless the entire area with adequate prey in 1993-1994 had been protected, the much reduced viable area in 1999-2001 might well have been excluded. During long non-foraging periods (as at night), eiders can save much energy by resting on ice vs. floating on water; thus, loss of ice cover in the future might substantially decrease the area in which prey densities are adequate to offset the eiders' energy needs. For wide-ranging benthivores such as eiders, our results emphasize that fixed protected areas based on current conditions can be too small or inflexible to subsume long

  12. Early life ecology of Alaska plaice ( Pleuronectes quadrituberculatus) in the eastern Bering Sea: Seasonality, distribution, and dispersal

    NASA Astrophysics Data System (ADS)

    Duffy-Anderson, Janet T.; Doyle, Miriam J.; Mier, Kathryn L.; Stabeno, Phyllis J.; Wilderbuer, Thomas K.

    2010-07-01

    We examined the patterns of abundance and distribution of Alaska plaice, Pleuronectes quadrituberculatus, eggs, larvae and pelagic juveniles over the southeastern Bering Sea shelf to better understand factors controlling transport and recruitment of flatfish in the Bering Sea. Ichthyoplankton data were derived from plankton surveys conducted in 1997, 1999, 2002, 2003, and 2005. Temperature, salinity, depth, and abundance of microzooplankton were measured concurrently. Eggs and larvae were primarily collected from depths < 200 m, with the majority occurring over bottom depths ranging 50-100 m. Eggs were present throughout the water column, though densities of preflexion stage larvae were concentrated at depths 10-20 m. There was no evidence of vertical migration for pre-flexion stages. Spawning in Alaska plaice occurs primarily east of Port Moller in April and May, and eggs and larvae appear to drift to the north and northeast, an observation based on satellite-tracked drifter information, model output, and collections of older, later-stage postlarvae. Connectivity between spawning areas and nursery habitats is likely influenced by wind forcing, so climate-mediated changes to dispersal trajectory or timing is expected to have significant impacts on recruitment in this species, though entrainment in consistent, directional currents may modify these effects.

  13. Juvenile Chinook Salmon abundance in the northern Bering Sea: Implications for future returns and fisheries in the Yukon River

    NASA Astrophysics Data System (ADS)

    Murphy, James M.; Howard, Kathrine G.; Gann, Jeanette C.; Cieciel, Kristin C.; Templin, William D.; Guthrie, Charles M.

    2017-01-01

    Juvenile Chinook Salmon (Oncorhynchus tshawytscha) abundance in the northern Bering Sea is used to provide insight into future returns and fisheries in the Yukon River. The status of Yukon River Chinook Salmon is of concern due to recent production declines and subsequent closures of commercial, sport, and personal use fisheries, and severe restrictions on subsistence fisheries in the Yukon River. Surface trawl catch data, mixed layer depth adjustments, and genetic stock mixtures are used to estimate juvenile abundance for the Canadian-origin stock group from the Yukon River. Abundance ranged from a low of 0.62 million in 2012 to a high of 2.58 million in 2013 with an overall average of 1.5 million from 2003 to 2015. Although abundance estimates indicate that average survival is relatively low (average of 5.2%), juvenile abundance was significantly correlated (r=0.87, p=0.005) with adult returns, indicating that much of the variability in survival occurs during early life-history stages (freshwater and initial marine). Juvenile abundance in the northern Bering Sea has increased since 2013 due to an increase in early life-history survival (average juveniles-per-spawner increased from 29 to 59). The increase in juvenile abundance is projected to produce larger runs and increased subsistence fishing opportunities for Chinook Salmon in the Yukon River as early as 2016.

  14. Petrology and isotopic composition of Quaternary basanites dredged from the Bering Sea continental margin near Navarin Basin

    USGS Publications Warehouse

    Davis, A.S.; Gunn, S.H.; Gray, L.-B.; Marlow, M. S.; Wong, F.L.

    1993-01-01

    Quaternary basanites were recovered from the continental margin of the Bering Sea near Navarin Basin. The basanites are highly vesicular flow rock and hyaloclastites similar to other alkalic volcanic rocks erupted repeatedly during the last Cenozoic on islands in the Bering Sea region and in mainland Alaska. K-Ar ages for the basanites indicate at least two episodes of volcanism at about 1.1 and 0.4 Ma. Trace-element data indicate these alkalic lavas have been generated by small, but variable, amounts of partial melting of a metasomatized lherzolite source. The relativley primitive compositions (MgO >9%), presence of mantle-derived xenoliths in some alkalic lavas, and presence of forsteritic olivine with low CaO and high NiO suggest that magma rose rapidly from great depth without spending time in large, long-lived magma chambers. Alkalic volcanism apparently resulted from upwelling and decompressional melting of small isolated mantle diapirs in response to local lithospheric attenuation associated with jostling of blocks during adjustment to regional stresses. -from Authors

  15. Trophic cascades and future harmful algal blooms within ice-free Arctic Seas north of Bering Strait: A simulation analysis

    NASA Astrophysics Data System (ADS)

    Walsh, John J.; Dieterle, Dwight A.; Chen, F. Robert; Lenes, Jason M.; Maslowski, Wieslaw; Cassano, John J.; Whitledge, Terry E.; Stockwell, Dean; Flint, Mikhail; Sukhanova, Irina N.; Christensen, John

    2011-11-01

    Within larger ice-free regions of the western Arctic Seas, subject to ongoing trophic cascades induced by past overfishing, as well as to possible future eutrophication of the drainage basins of the Yukon and Mackenzie Rivers, prior very toxic harmful algal blooms (HABs) - first associated with ∼100 human deaths near Sitka, Alaska in 1799 - may soon expand. Blooms of calcareous coccolithophores in the Bering Sea during 1997-1998 were non-toxic harbingers of the subsequent increments of other non-siliceous phytoplankton. But, now saxitoxic dinoflagellates, e.g. Alexandrium tamarense, were instead found by us within the adjacent downstream Chukchi Sea during SBI cruises of 2002 and 2003. A previous complex, coupled biophysical model had been validated earlier by ship-board observations from the Chukchi/Beaufort Seas during the summer of 2002. With inclusion of phosphorus as another chemical state variable to modulate additional competition by recently observed nitrogen-fixers, we now explore here the possible consequences of altered composition of dominant phytoplankton functional groups [diatoms, microflagellates, prymnesiophyte Phaeocystis colonies, coccolithophores, diazotrophs, and dinoflagellates] in relation to increases of the toxic A. tamarense, responding to relaxation of grazing pressure by herbivores north of Bering Strait as part of a continuing trophic cascade. Model formulation was guided by validation observations obtained during 2002-2004 from: cruises of the SBI, CHINARE, and CASES programs; moored arrays in Bering Strait; other RUSALCA cruises around Wrangel Island; and SBI helicopter surveys of the shelf-break regions of the Arctic basin. Our year-long model scenarios during 2002-2003 indicate that post bloom silica-limitation of diatoms, after smaller simulated spring grazing losses, led to subsequent competitive advantages in summer for the coccolithophores, dinoflagellates, and diazotrophs. Immediate top-down control is exerted by imposed

  16. Remote Correlation of Paleoceanographic Events in the Northern Parts of Bering and Barents Seas during the Termination I and Early Holocene

    NASA Astrophysics Data System (ADS)

    Ivanova, E. V.; Ovsepyan, E.; Murdmaa, I.; de Vernal, A.; Risebrobakken, B.; Seitkalieva, E.; Radionova, E.; Alekhina, G.

    2014-12-01

    The Barents and Bering seas are closely linked to the High Arctic and to the THC by marine gateways as well as by land-sea and ocean-atmosphere interactions. Our multi-proxy time series demonstrate that these remote seas exhibited dramatic changes during the deglaciation through a succession of global and regional paleoceanographic events including the beginning of Termination I (BT1), Heinrich-1 or Oldest Dryas (OD), Bølling-Allerød (B/A), Younger Dryas (YD) and early Holocene (EH). In the NW Barents Sea, the increased subsurface-to-bottom Atlantic water inflow via the Kvitøya-Erik Eriksen trough (cores S 2519 and S 2528) is inferred at the late OD, late B/A and late YD/EH transition. These events are generally coupled with the strengthened AMOC. A remarkable sea surface warming and sea ice retreat are documented at ~ 13 ka BP. Surface warming and strong Atlantic water inflow were followed by intense iceberg calving in the Erik Eriksen Trough as indicated by the high IRD content of Core S-2519. The rock fragments are unsorted and mainly angular suggesting their ice-rafted (likely iceberg-rafted) origin. Svalbard glaciers apparently derived the material dominated by black schistous mudstones, hard limestones with coral remains, fine-grained sandstones from nearby islands, and icebergs spread it in the Kvitøya-Erik Eriksen Trough during the early deglaciation. The ice rafted coarse terrigenous material supply during the BT1 is also suggested for the NW Bering Sea. In the NW Pacific, NW Bering Sea and Sea of Okhotsk, surface bioproductivity peaked at B/A and EH mainly due to the global warming, enhanced nutrient supply by surface currents from the flooded northeastern shelf, intensified vertical mixing and water exchange through the opened straits. Oxygen-depleted bottom water at intermediate depths characterized several locations including the NW Bering Sea (Core SO201-2-85KL).

  17. Synthesis of information on the effects of noise and disturbance on major haulout concentrations of Bering Sea pinnipeds. Final report

    SciTech Connect

    Johnson, S.R.; Burns, J.J.; Malme, C.I.; Davis, R.A.

    1989-02-17

    The study investigated the use of terrestrial haulout sites in the eastern Bering Sea by four species of pennipeds, northern fur seal, northern sea lion, harbor seal and pacific walrus. Historical information on the use of each site was summarized. Available information on the effects of airborne and waterborne noise, and human disturbance (from stationary and moving sources) was reviewed. The authors also conducted a detailed analysis of the acoustic environment of eight haulout sites that were representative of others used by each of the four species studied. The analyses included investigations of (1) characteristics airborne and underwater ambient noise, (2) characteristics of industrial noise sources, including aircraft, small boats, fishing trawlers and commercial cargo traffic, and (3) sound transmission loss in air, water, and through the air-water surface. As a means to evaluate the potential vulnerability of each haulout site to noise and disturbance, a quantitative rating system (IPSI) whereby an index of sensitivity was assigned to each site.

  18. The Bering Sea ice cover during March 1979: Comparison of surface and satellite data with the Nimbus-7 SMMR

    NASA Technical Reports Server (NTRS)

    Martin, S.; Cavalieri, D. J.; Gloersen, P.; Mcnutt, S. L.

    1982-01-01

    During March 1979, field operations were carried out in the Marginal Ice Zone (MIZ) of the Bering Sea. The field measurements which included oceanographic, meteorological and sea ice observations were made nearly coincident with a number of Nimbus-7 and Tiros-N satellite observations. The results of a comparison between surface and aircraft observations, and images from the Tiros-N satellite, with ice concentrations derived from the microwave radiances of the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) are given. Following a brief discussion of the field operations, including a summary of the meteorological conditions during the experiment, the satellite data is described with emphasis on the Nimbus-7 SMMR and the physical basis of the algorithm used to retrieve ice concentrations.

  19. Sediment reworking rates in deep sediments of the Mediterranean Sea.

    PubMed

    Barsanti, M; Delbono, I; Schirone, A; Langone, L; Miserocchi, S; Salvi, S; Delfanti, R

    2011-07-01

    Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented. ²¹⁰Pb(xs) and ¹³⁷Cs vertical profiles, together with ¹⁴C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D(b)). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments. Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm² yr⁻¹), and the highest values of ²¹⁰Pb(xs) and ¹³⁷Cs inventories. Intermediate values of SML and D(b) (~6 cm and ~0.040 cm² yr⁻¹, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D(b) of 0.011 cm² yr⁻¹ are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D(b) of ~0.005 cm² yr⁻¹).

  20. Volcano hazards and potential risks on St. Paul Island, Pribilof Islands, Bering Sea, Alaska

    NASA Astrophysics Data System (ADS)

    Feeley, T. C.; Winer, G. S.

    2009-05-01

    the island. Thus, a new vent could form at any place on the island, including St. Paul's insular shelf and areas farther offshore. Because of the remote location of St. Paul in the storm-lashed Bering Sea, risks related to volcano hazards may be greater than they would be in a different setting where more stable meteorological conditions prevail and access by monitoring and relief groups is less challenging.

  1. Millennial-scale variability of marine productivity and terrigenous matter supply in the western Bering Sea over the past 180 kyr

    NASA Astrophysics Data System (ADS)

    Riethdorf, J.-R.; Nürnberg, D.; Max, L.; Tiedemann, R.; Gorbarenko, S. A.; Malakhov, M. I.

    2012-12-01

    We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas primary production was low. Minor increases in marine productivity occurred during warm intervals of stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. Seasonal sea-ice is suggested to act as the dominant transport agent for terrigenous material. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait and the Aleutian passes is considered to have had an additional impact. Sea-ice dynamics are thought to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard-Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.

  2. Petrology and provenance of deep sea drilling project sand and sandstone from the north pacific ocean and the bering sea

    NASA Astrophysics Data System (ADS)

    Gergen, Leslie Dickson; Ingersoll, Raymond V.

    1986-12-01

    Sand and sandstone compositions from different types of basins reflect provenance terranes governed by plate tectonics. One hundred and one thin sections of Upper Miocene to Holocene sand-sized material were examined from DSDP/IPOD Sites in the North Pacific Ocean and the Bering Sea. The Gazzi-Dickinson point-counting method was used to establish compositional characteristics of sands from different tectonic settings. Continental margin forearc sands from the western North America continental margin arc system are clearly different from backarc/marginal-sea sands from the Aleutian intraoceanic arc system. The forearc sands have average QFL percentages of 29-42-29, LmLvLst percentages of 32-34-34, 3 Fmwk%M and 0.82 P/F. Aleutian backarc sands have average QFL percentages of 8-22-69. LmLvLst percentages of 9-85-6, 0.5 Fmwk%M and 0.96 P/F. A trend of increasing QFL%Q and decreasing LmLvLst%Lv westward in the backarc region of the Aleutian Ridge reflects the influence of the Asiatic continental margin. Aleutian backarc sands without continental influence have average QFL percentages of 1-20-79, LmLvLst percentages of 1-98-1, 0 Fmwk%M and 0.99 P/F. Of the continental margin forearc samples, sands on the Astoria Fan (west of the Oregon—Washington trench) contain the highest LmLvLst%Lv and lowest P/F; sands from mixed transform-fault and trench settings (Delgada Fan and Gulf of Alaska samples) have slightly higher Qp/Q (0.03); and sands from the Pacific-Juan de Fuca-North America triple junction have the highest Fmwk%M. Delgada Fan and Gulf of Alaska sands have average QFL percentages of 27-38-35, LmLvLst percentages of 37-26-37, 2 Fmwk%M and 0.86 P/F. Astoria Fan sands have average QFL percentages of 35-41-24, LmLvLst percentages of 30-47-23, 3 Fmwk%M and 0.74 P/F. The triple-junction sands have average QFL percentages of 28-59-13, LmLvLst percentages of 25-26-49, 9 Fmwk%M and 0.87 P/F. The petrologic data from the modern ocean basins examined in this study can provide

  3. Spring Bloom Dynamics of the Eastern Bering Sea Shelf as Estimated from Oxygen/Argon Ratios and Triple Oxygen Isotopes

    NASA Astrophysics Data System (ADS)

    Prokopenko, M.; Granger, J.; Mordy, C. W.; Difiore, P.; Cassar, N.; Cokelet, E.; Kachel, N. B.; Kachel, D. N.; Sambrotto, R.; Moran, B.

    2008-12-01

    The Bering Sea's position at the end of the global ocean "conveyor belt" and shoaling of nutrient rich water masses onto its broad shelf make the Eastern Bering Sea shelf one of the most productive regions of the polar oceans, with reported annual primary production rates of 150 to 500 gC*m-2 yr-1. Much of this production occurs during spring blooms, which follow the inception of water column stratification after the retreat of sea-ice. The fate of the bloom biomass determines the amount of the export production available to higher trophic levels in the shelf ecosystem, but due to the hydrographic variability of the ice edge regime direct measurements of productivity rates are not easily extrapolated in space and time. Hence, a more integrative approach is needed. Here we report estimates of Net Community and Gross Photosynthetic Production rates (GPP and NCP) obtained from O2/Ar and triple oxygen isotope ratios measured as a part of the BEST (Bering Sea Ecosystem Study) project during six weeks of spring 2007. Under steady state conditions, NCP and new production should be stoichiometrically equivalent to net photosynthetic O2 production and can be estimated from oxygen air-sea exchange fluxes. In this study, O2/Ar ratios, used to distinguish between biological and physical components of oxygen flux, were measured continuously by a quadrupole mass spectrometer equipped with an Equilibrator Inlet (EIMS, modified from Kaiser et al., 2005). To calibrate EIMS results, discrete samples were collected from the ship's underway seawater system and from hydrocasts. Dissolved O2 and Ar were cryogenically isolated and extracted offline and analyzed on an IRMS at the Geosciences Dept, Princeton Univ. To estimate the rates of gross photosynthetic production, oxygen triple isotope ratios of dissolved O2 were measured on the same discrete samples. Ventilation rates (piston velocities) were calculated based on Quikscat wind speeds and the parameterization of Wanninkhof (1992

  4. Surface nitrate utilization in the Bering sea since 180 kA BP: Insight from sedimentary nitrogen isotopes

    NASA Astrophysics Data System (ADS)

    Riethdorf, Jan-Rainer; Thibodeau, Benoit; Ikehara, Minoru; Nürnberg, Dirk; Max, Lars; Tiedemann, Ralf; Yokoyama, Yusuke

    2016-03-01

    We present high-resolution records of sedimentary nitrogen (δ15Nbulk) and carbon isotope ratios (δ13Cbulk) from piston core SO201-2-85KL located in the western Bering Sea. The records reflect changes in surface nitrate utilization and terrestrial organic matter contribution in submillennial resolution that span the last 180 kyr. The δ15Nbulk record is characterized by a minimum during the penultimate interglacial indicating low nitrate utilization (~62-80%) despite the relatively high export production inferred from opal concentrations along with a significant reduction in the terrestrial organic matter fraction (mterr). This suggests that the consumption of the nitrate pool at our site was incomplete and even more reduced than today (~84%). δ15Nbulk increases from Marine Isotope Stage (MIS) 5.4 and culminates during the Last Glacial Maximum, which indicates that nitrate utilization in the Bering Sea was raised during cold intervals (MIS 5.4, 5.2, 4) and almost complete during MIS 3 and 2 (~93-100%). This is in agreement with previous hypotheses suggesting that stronger glacial stratification reduced the nutrient supply from the subeuphotic zone, thereby increasing the iron-to-nutrient ratio and therefore the nitrate utilization in the mixed surface layer. Large variations in δ15Nbulk were also recorded from 180 to 130 ka BP (MIS 6), indicating a potential link to insolation and sea-level forcing and its related feedbacks. Millennial-scale oscillations were observed in δ15Nbulk and δ13Cbulk that might be related to Greenland interstadials.

  5. Cetacean distribution and relative abundance on the central eastern and the southeastern Bering Sea shelf with reference to oceanographic domains

    NASA Astrophysics Data System (ADS)

    Moore, S. E.; Waite, J. M.; Friday, N. A.; Honkalehto, T.

    2002-10-01

    Visual line-transect surveys for cetaceans were conducted in the central-eastern Bering Sea (CEBS) from 5 July to 5 August 1999, and in the southeastern Bering Sea (SEBS) from 10 June to 3 July 2000, in association with a pollock stock assessment survey aboard the NOAA ship Miller Freeman. Observers scanned for cetaceans with 25× (Big Eye) binoculars from the flying bridge (platform height=12 m) at survey speeds of 18.5-22 km h -1 (10-12 knots). Transect survey effort was 1761 km in 1999, in a study area 196,885 km 2; and 2194 km in 2000, in a study area 158,561 km 2. An additional 609 and 402 km of trackline was surveyed in 1999 and 2000, respectively, while in transit to or from pollock survey way points. Fin whales ( Balaenoptera physalus) were the most common large whale, and Dall’s porpoise ( Phocoenoides dalli) the most common small cetacean in both regions. In the CEBS (1999), uncorrected cetacean abundance estimates were: 3368 (CV=0.29) fin whales, 810 (CV=0.36) minke whales ( B. acutorostrata), 14,312 (CV=0.26) Dall’s porpoise and 693 (CV=0.53) harbor porpoise ( Phocoenaphocoena). In the SEBS (2000), uncorrected abundance estimates were: 683 (CV=0.32) fin whales, 102 (CV=0.50) humpback whales ( Megaptera novaeangliae), 1003 (CV=0.26) minke whales, 9807 (CV=0.20) Dall’s porpoise and 1958 (CV=0.21) harbor porpoise. These are the first estimates of cetacean abundance that can be directly compared between two regions of the eastern Bering Sea. Distributions of some species were associated with bathymetric features, and there were occasions when prey associations were obvious. For example, in the SEBS, fin whales occurred on the Middle Shelf (50-100 m) and on the Outer Shelf (100-200 m) near the Pribilof canyon, but in the CEBS fin whales occurred primarily on the Outer Shelf along the 200 m isobath (i.e. the Green Belt). Fin whales were sometimes associated with echo-sounder backscatter from a mixture of fish schools and zooplankton. Humpback whales

  6. Mesoscale eddies transport deep-sea sediments.

    PubMed

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-08-04

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process.

  7. Bioaccumulation of persistent organochlorine pesticides (OCPs) by gray whale and Pacific walrus from the western part of the Bering Sea.

    PubMed

    Tsygankov, Vasiliy Yu; Boyarova, Margarita D; Lukyanova, Olga N

    2015-10-15

    The feeding habits of a gray whale (Eschrichtius robustus) and a Pacific walrus (Odobenus rosmarus divergens), caught from the western Bering Sea in the summers of 2010 and 2011, have been studied, and concentration of persistent organochlorine pesticides (OCPs) in their organs determined. The total OCP concentration (∑HCH+∑DDT) in muscles and liver of the gray whales varies from 297 to 3581 and from 769 to 13,808 ng/g lipids, respectively. The total OCP concentration (∑HCH+∑DDT) in muscles and liver of the Pacific walruses varies from 197 to 5659 and from 4856 to 90,263 ng/g lipids, respectively. The specifics of diet as a source of pesticide accumulation in these two marine mammal species are discussed.

  8. Cetacean distribution and abundance in relation to oceanographic domains on the eastern Bering Sea shelf: 1999-2004

    NASA Astrophysics Data System (ADS)

    Friday, Nancy A.; Waite, Janice M.; Zerbini, Alexandre N.; Moore, Sue E.

    2012-06-01

    Visual line transect surveys for cetaceans were conducted on the eastern Bering Sea shelf in association with pollock stock assessment surveys aboard the NOAA ship Miller Freeman in June and July of 1999, 2000, 2002, and 2004. Transect survey effort ranged from 1188 km in 1999 to 3761 km in 2002. Fin whales (Balaenoptera physalus) were the most common large whale in all years except 2004 when humpback whales (Megaptera novaeangliae) were more abundant. Dall's porpoise (Phocoenoides dalli) were the most common small cetacean in all years. Abundance estimates were calculated by year for each oceanographic domain: coastal, middle, and outer/slope. The middle and outer/slope domains were divided into two strata ("north" and "south") because of variable survey effort. The distribution and abundance of baleen whales changed between the earlier (colder) and later (warmer) survey years. Fin whales consistently occupied the outer shelf and secondarily the middle shelf, and their abundance was an order of magnitude greater in cold compared to warm years. Humpback whales "lived on the margin" of the northern Alaska Peninsula, eastern Aleutian Islands and Bristol Bay; their preferred habitat is possibly associated with areas of high prey availability due to nutrient upwelling and aggregation mechanisms. Minke whales (Balaenoptera acutorostrata) occur shoreward of fin whales in the outer and middle shelf and in coastal habitats along the Alaska Peninsula. The highest abundance for this species was observed in a cold (1999) year. No clear relationship emerged for odontocetes with regard to warm and cold years. Dall's porpoise occupied both outer and middle domains and harbor porpoise (Phocoena phocoena) were more common in middle and coastal domains. This study provided a unique, broad-scale assessment of cetacean distribution and abundance on the eastern Bering Sea shelf and a baseline for future comparisons.

  9. Effects of CO2 and iron availability on rbcL gene expression in Bering Sea diatoms

    NASA Astrophysics Data System (ADS)

    Endo, H.; Sugie, K.; Yoshimura, T.; Suzuki, K.

    2014-12-01

    Iron (Fe) can limit phytoplankton productivity in approximately 40% of the global ocean, including high-nutrient, low-chlorophyll (HNLC) waters. However, there is little information available on the impact of CO2-induced seawater acidification on natural phytoplankton assemblages in HNLC regions. We therefore conducted an on-deck experiment manipulating CO2 and Fe using Fe-deficient Bering Sea waters during the summer of 2009. The concentrations of CO2 in the incubation bottles were set at 380 and 600 ppm in the non-Fe-added (control) bottles and 180, 380, 600, and 1000 ppm in the Fe-added bottles. The phytoplankton assemblages were primarily composed of diatoms followed by haptophytes in all incubation bottles as estimated by pigment signatures throughout the 7 day incubation period. At the end of incubation, the relative contributions of diatoms to chlorophyll a biomass decreased significantly with increased CO2 levels in the controls, whereas minimal changes were found in the Fe-added treatments. These results indicate that, under Fe-deficient conditions, the growth of diatoms was negatively affected by the increase in CO2 availability. To confirm this, we estimated the expression and phylogeny of rbcL (which encodes the large subunit of RubisCO) mRNA in diatoms by quantitative reverse transcription PCR and clone library techniques, respectively. Interestingly, regardless of Fe availability, the expression and diversity of rbcL cDNA decreased in the high CO2 treatments (600 and 1000 ppm). The present study suggests that the projected future increase in seawater pCO2 could reduce the RubisCO activity of diatoms, resulting in a decrease in primary productivity and a shift in the food web structure of the Bering Sea.

  10. Effects of CO2 and iron availability on rbcL gene expression in Bering Sea diatoms

    NASA Astrophysics Data System (ADS)

    Endo, H.; Sugie, K.; Yoshimura, T.; Suzuki, K.

    2015-04-01

    Iron (Fe) can limit phytoplankton productivity in approximately 40% of the global ocean, including in high-nutrient, low-chlorophyll (HNLC) waters. However, there is little information available on the impact of CO2-induced seawater acidification on natural phytoplankton assemblages in HNLC regions. We therefore conducted an on-deck experiment manipulating CO2 and Fe using Fe-deficient Bering Sea water during the summer of 2009. The concentrations of CO2 in the incubation bottles were set at 380 and 600 ppm in the non-Fe-added (control) bottles and 180, 380, 600, and 1000 ppm in the Fe-added bottles. The phytoplankton assemblages were primarily composed of diatoms followed by haptophytes in all incubation bottles as estimated by pigment signatures throughout the 5-day (control) or 6-day (Fe-added treatment) incubation period. At the end of incubation, the relative contribution of diatoms to chlorophyll a biomass was significantly higher in the 380 ppm CO2 treatment than in the 600 ppm treatment in the controls, whereas minimal changes were found in the Fe-added treatments. These results indicate that, under Fe-deficient conditions, the growth of diatoms could be negatively affected by the increase in CO2 availability. To further support this finding, we estimated the expression and phylogeny of rbcL (which encodes the large subunit of RuBisCO) mRNA in diatoms by quantitative reverse transcription polymerase chain reaction (PCR) and clone library techniques, respectively. Interestingly, regardless of Fe availability, the transcript abundance of rbcL decreased in the high CO2 treatments (600 and 1000 ppm). The present study suggests that the projected future increase in seawater pCO2 could reduce the RuBisCO transcription of diatoms, resulting in a decrease in primary productivity and a shift in the food web structure of the Bering Sea.

  11. Distribution of fish and macrozooplankton in ice-covered and open-water areas of the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    De Robertis, Alex; Cokelet, Edward D.

    2012-06-01

    The eastern Bering Sea shelf is a productive ecosystem with extensive commercial fisheries. Although the area is well-studied during summer months, little is known about the abundance and distribution of fish and macrozooplankton during periods of seasonal ice cover. The use of an icebreaker during the Bering Sea Ecosystem Study (BEST) provided a platform for spring acoustic surveys of fish and zooplankton in ice-covered areas for the first time. Icebreaker measurements were complemented with observations from conventional vessels during spring and summer. In spring, very little backscatter from fish (dominated by walleye pollock, Theragra chalcogramma) was observed in the ice-covered northern areas where near-bottom waters were cold (<˜0.5 °C), including areas where walleye pollock are abundant in summer. The majority of fish were observed within 40 km (and often slightly inside) the ice edge over similar seafloor depths as in summer. Together, these observations suggest that pollock, a dominant component of the ecosystem, shift their distribution to a more restricted geographic area in spring, following the ice edge southeast along the bathymetry, away from areas of cold water and extensive ice cover, then reoccupying these areas in summer. In contrast, acoustic backscatter attributed to zooplankton (likely dominated by euphausiids) was more evenly distributed, and less restricted by water temperature and ice cover. The implications of this seasonal shift in fish distribution are uncertain, but this may affect predator-prey interactions by reducing overlap of pollock with euphausiids, an important prey source, while increasing overlap of adult and juvenile pollock and potentially increasing cannibalism.

  12. Effects of seasonal and interannual variability in along-shelf and cross-shelf transport on groundfish recruitment in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Vestfals, Cathleen D.; Ciannelli, Lorenzo; Duffy-Anderson, Janet T.; Ladd, Carol

    2014-11-01

    The Bering Sea responds rapidly to atmospheric perturbations and over the past several decades has experienced extreme variability in both its physical and biological characteristics. These changes can impact organisms that inhabit the region, particularly marine fishes, as normal current patterns to which reproductive habits are tuned can be disrupted, which, in turn, may influence recruitment and population dynamics. To understand the influence of ocean circulation on groundfish recruitment in the eastern Bering Sea, we examined transport along and across the Bering Slope derived from 23 years (1982-2004) of simulations from a Regional Ocean Modeling System (ROMS) ocean circulation model. We expected that changes in the strength and position of the Bering Slope Current (BSC) would affect recruitment in selected species (Pacific cod, walleye pollock, Greenland halibut, Pacific halibut, and arrowtooth flounder), and that circulation features along and across the shelf edge would be strongly influenced by atmospheric forcing. Variability in along-shelf transport at three transects along the path of the BSC, cross-shelf transport across the 100 and 200 m isobaths, and transport through Unimak Pass were examined. Strong seasonal and interannual variations in flow were observed, with transport typically highest during fall and winter months, coinciding with timing of spawning activity in the five species. Significant correlations were found between transport, BSC position, and groundfish recruitment. Pacific cod, in particular, benefitted from decreased along-shelf and on-shelf flow, while Pacific halibut recruitment increased in relation to increased on-shelf transport through southern canyons. The results of this study improve our understanding of variability in circulation and associated effects on groundfish recruitment in the eastern Bering Sea.

  13. Sediment dispersal in the northwestern Adriatic Sea

    USGS Publications Warehouse

    Harris, C.K.; Sherwood, C.R.; Signell, R.P.; Bever, A.J.; Warner, J.C.

    2008-01-01

    Sediment dispersal in the Adriatic Sea was evaluated using coupled three-dimensional circulation and sediment transport models, representing conditions from autumn 2002 through spring 2003. The calculations accounted for fluvial sources, resuspension by waves and currents, and suspended transport. Sediment fluxes peaked during southwestward Bora wind conditions that produced energetic waves and strengthened the Western Adriatic Coastal Current. Transport along the western Adriatic continental shelf was nearly always to the south, except during brief periods when northward Sirocco winds reduced the coastal current. Much of the modeled fluvial sediment deposition was near river mouths, such as the Po subaqueous delta. Nearly all Po sediment remained in the northern Adriatic. Material from rivers that drain the Apennine Mountains traveled farther before deposition than Po sediment, because it was modeled with a lower settling velocity. Fluvial sediment delivered to areas with high average bed shear stress was more highly dispersed than material delivered to more quiescent areas. Modeled depositional patterns were similar to observed patterns that have developed over longer timescales. Specifically, modeled Po sediment accumulation was thickest near the river mouth with a very thin deposit extending to the northeast, consistent with patterns of modern sediment texture in the northern Adriatic. Sediment resuspended from the bed and delivered by Apennine Rivers was preferentially deposited on the northern side of the Gargano Peninsula, in the location of thick Holocene accumulation. Deposition here was highest during Bora winds when convergences in current velocities and off-shelf flux enhanced delivery of material to the midshelf. Copyright 2008 by the American Geophysical Union.

  14. Interaction of oil with sea ice. Appendix 4. The Bering Sea ice cover during March 1979: comparison of surface and satellite data with the Nimbus-7 smmr (scanning multichannel microwave radiometer)

    SciTech Connect

    Martin, S.; McNutt, S.L.; Cavalieri, D.J.; Gloersen, P.

    1982-01-01

    During March 1979, field operations were carried out in the Marginal Ice Zone (MIZ) of the Bering Sea. This report presents the results of a comparison between surface and aircraft observations, and images from the Tiros-N satellite, with ice concentrations derived from the microwave radiances of the Nimbus-7 Scanning Multichannel Microwave Radiometer.

  15. Manifestation of the petrogeneration zones of Northern and the Bering seas in ground magnetic anomalies and anomalies of satellite Champ

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Krasinsky, Egor; Petrova, Alevtina; Demina, Irina

    2010-05-01

    The purpose of this paper are showed results of studying of specificity of a deep structure of zones of petrogeneration Northern and the Bering seas on aeromagnetic and satellite magnetometric datas. Research lateral and vertical heterogeneitys an earth's crust of Northern sea is carried out on the basis of the analysis of measurements of satellite Champ at height of 100 km and the digital database created on materials of sea shooting of a geomagnetic field, executed on non-magnetic schooner "Zarya". On sea measurements in Northern sea through large oil fields and gas ( Frigg, Ekofisk, Forties trough, Leman, etc.). Geomagnetic sections for an interval of depths from 1 up to 30 km are constructed. It has allowed to study character of distribution of magnetization of breeds of a cover, horizontal lamination intracore layers of an earth's crust and to allocate in zones petrogeneration synvertical fluidoconduct zones the channels described by alternation of not magnetic and low-magnetic layers. They were showed on geomagnetic sections as permeable zones quasi- laminated structures with the lowered magnetic properties in an interval of depths from 8 up to 28 km. Comparison to a map of the magnetic anomalies measured at height of 100 km by satellite Champ, has shown, that areas of the greatest petrocongestions North Sea рифта at height of 100 km are dated for a zone of gradients and a minimum of northeast displacement of regional anomalies of western and east blocks of Northern sea. It corresponds to representations about an orientation of a fissuring zone and the increased size of a geothermal gradient North Sea rift and is corresponded position allocated on hydromagnetic structures deep fluidoconduct channels. Thus, distribution to water areas of deposits of deposits is emphasized not only low-magnetic areas in a thickness of a sedimentary cover where they are directly located, but also by not magnetic lenses in breeds of the base spreading it in intervals of

  16. Was the Aleutian basin more enclosed. Its deep oxygen deficient, and the geothermal gradient steepened in the middle Tertiary Implications for the petroleum potential of the Bering Sea

    SciTech Connect

    Scholl, D.W.; Stevenson, A. )

    1990-06-01

    Circulation of north Pacific waters through the Aleutian Basin of the deep Bering Sea (3,500-4,000 m) is presently vigorous and affects all depths. Energetic currents enter and exit the Bering Sea via deepwater (1,000-4,000 m) passes in the Aleutian Ridge. But geologic evidence suggests that in the middle Tertiary (or earlier), the basin was possibly stagnant or poorly ventilated. A sequence of undeformed sedimentary deposits typically more than 4 km thick underlies the south-central bathymetric deep of the basin. The basinal sequence includes hundreds of velocity-amplitude anomalies (VAMPs), which are deep-water bright spots associated with underlying velocity pull-downs. The VAMPs are thought to record the pooling of thermogenic gas at subbottom depths of 800 to 1,000 m. Because VAMPs are largely confined to the basin's bathymetric low, subsurface source beds that supplied the gases must be located here. Favorable preservation of organic matter over the basin deep may reflect a former oxygen-poor bottom-water environment. Tectonic reconstructions indicate that prior to the middle Tertiary a more laterally continuous Aleutian Ridge restricted circulation with the north Pacific, a circumstance that would have favored incomplete deep basin ventilation. New information concerning the paleoceanographic history of the Bering Sea, the prospect that organic-rich source beds have been deposited, and the likelihood that an episode of early Tertiary backarc spreading enhanced the basin's geothermal gradient, combine to improve the petroleum potential of the Aleutian basin.

  17. Correlation between recruitment and fall condition of age-0 pollock (Theragra chalcogramma) from the eastern Bering Sea under varying climate conditions

    NASA Astrophysics Data System (ADS)

    Heintz, Ron A.; Siddon, Elizabeth C.; Farley, Edward V.; Napp, Jeffrey M.

    2013-10-01

    Fishery managers require an understanding of how climate influences recruitment if they are to separate the effects of fishing and climate on production. The southeastern Bering Sea offers opportunities to understand climate effects on recruitment because inter-annual oscillations in ice coverage set up warm or cold conditions for juvenile fish production. Depth-averaged temperature anomalies in the Bering Sea indicate the past nine years have included three warm (2003-2005), an average (2006), and five cold (2007-2011) years. We examined how these climatic states influenced the diet quality and condition (size, energy density and total energy) of young-of-the-year (YOY) pollock (Theragra chalcogramma) in fall. The implications of fall condition were further examined by relating condition prior to winter to the number of age-1 recruits-per-spawner the following summer (R/S). The percentage of lipid in pollock diets was threefold higher in cold years compared with warm years, but stomach fullness did not vary. Consequently, fish energy densities were 33% higher in cold years (P<0.001) than in warm years. In contrast, neither fish size (P=0.666), nor total energy (P=0.197) varied with climatic condition. However, total energy was significantly (P=0.007) and positively correlated with R/S (R2=0.736). We conclude that recruitment to age-1 in the southeastern Bering Sea is improved under environmental conditions that produce large, energy dense YOY pollock in fall.

  18. Determination of the chlorophyll a concentration by MODIS-Aqua and VIIRS satellite radiometers in Eastern Arctic and Bering Sea

    NASA Astrophysics Data System (ADS)

    Salyuk, P. A.; Stepochkin, I. E.; Bukin, O. A.; Sokolova, E. B.; Mayor, A. Yu.; Shambarova, J. V.; Gorbushkin, A. R.

    2016-12-01

    The waters of the Bering and Chukchi seas, as well as the De Long Strait, are investigated based on the data obtained in August 2013 during the scientific expedition of the Far Eastern Floating University on the research vessel Professor Khlyustin. Chlorophyll a concentrations calculated from MODIS-Aqua and VIIRS satellite data by ocean color and obtained by means of shipboard flow-through fluorometric measurements are comparatively analyzed. Vessel data are corrected for standard spectrophotometric measurements and the vertical depth distribution of phytoplankton. It has been found that, in the waters of the Eastern Arctic, satellite radiometers showed overestimated chlorophyll a concentrations in the upper seawater layer visible from the satellite. This is associated with the additional contribution of colored dissolved organic matter in the sea surface color. In the De Long Strait, satellite measurements incorrectly estimate the depth integrated chlorophyll a concentration, since the bulk of phytoplankton cells at a chlorophyll a concentration of 10-20 g/L is at depths of 25-30 m with luminosity of 5%.

  19. Seabird sockeye salmon co-variation in the eastern Bering Sea: Phenology as an ecosystem indicator and salmonid predictor?

    NASA Astrophysics Data System (ADS)

    Sydeman, William J.; Abraham, Christine L.; Vernon Byrd, G.

    2008-08-01

    Seabirds ( Rissa spp. and Uria spp.) and sockeye salmon ( Onchorhynchus nerka) of the eastern Bering Sea share similarities in their trophic ecology. We tested the role of seabirds as indicators of food web conditions that affect sockeye salmon at sea survival by investigating co-variation between seabirds breeding on the Pribilof Islands and returns of Bristol Bay sockeyes. We examined seabird phenology (hatching dates of eggs) against sockeye returns based on the year of ocean entry. Annual seabird hatching date was inversely related to sockeye returns, with the strongest co-variation found for sockeye which entered the ocean at 2 years of age (age 2 x smolts). The mechanism supporting this co-variation is unknown, but both birds and salmon may be responding to changes in prey availability (a "bottom-up" effect). The co-variation between seabird hatching date and sockeye returns supports the idea that variation in seabird breeding parameters indicates food web conditions that also affect other upper trophic level predators in marine systems. Coupling seabird phenology with existing annual predictions for Bristol Bay salmon may improve forecasts and fishery management.

  20. Modeling spatial patterns of limits to production of deposit-feeders and ectothermic predators in the northern Bering Sea

    NASA Astrophysics Data System (ADS)

    Lovvorn, James R.; Jacob, Ute; North, Christopher A.; Kolts, Jason M.; Grebmeier, Jacqueline M.; Cooper, Lee W.; Cui, Xuehua

    2015-03-01

    Network models can help generate testable predictions and more accurate projections of food web responses to environmental change. Such models depend on predator-prey interactions throughout the network. When a predator currently consumes all of its prey's production, the prey's biomass may change substantially with loss of the predator or invasion by others. Conversely, if production of deposit-feeding prey is limited by organic matter inputs, system response may be predictable from models of primary production. For sea floor communities of shallow Arctic seas, increased temperature could lead to invasion or loss of predators, while reduced sea ice or change in wind-driven currents could alter organic matter inputs. Based on field data and models for three different sectors of the northern Bering Sea, we found a number of cases where all of a prey's production was consumed but the taxa involved varied among sectors. These differences appeared not to result from numerical responses of predators to abundance of preferred prey. Rather, they appeared driven by stochastic variations in relative biomass among taxa, due largely to abiotic conditions that affect colonization and early post-larval survival. Oscillatory tendencies of top-down versus bottom-up interactions may augment these variations. Required inputs of settling microalgae exceeded existing estimates of annual primary production by 50%; thus, assessing limits to bottom-up control depends on better corrections of satellite estimates to account for production throughout the water column. Our results suggest that in this Arctic system, stochastic abiotic conditions outweigh deterministic species interactions in food web responses to a varying environment.

  1. Iron sulfide minerals in Black Sea sediments

    NASA Astrophysics Data System (ADS)

    Franke, C.; Robin, E.; Henkel, S.; Kasten, S.; Bleil, U.

    2009-04-01

    This study presents an integrated geochemical, environmental magnetic, and electron microscopic approach to better understand the physicochemical processes in deep sea sediments from the northwestern Black Sea. The investigated gravity core GC 214 was retrieved in 2007 during RV Meteor cruise M72/1 west of the Crimean Peninsula in a water depth of 1686 mbsf. Geochemical analyses of the pore water and solid phase indicate non-steady state sedimentation. The oxygen-depleted water column conditions, anaerobic oxidation of methane (AOM) and related microbially-driven sulfate reduction favor a highly complex iron sulfide mineral assemblage in the sediment column. The detailed magnetic susceptibility and remanence measurements indicate an irregularly stratified depth profile showing intervals of particularly high values. Further environmental magnetic analyses depict strongly elevated coercivities for those depth horizons, suggesting greigite as one of the main magnetic carrier minerals. Automated chemical classification (ACC), using electron dispersive spectrometer (EDS) attached to a JEOL840 scanning electron microscope (SEM), on dispersed particle samples permitted the identification of greigite (Fe3S4) next to pyrrhotite (Fe7S8), pyrite (FeS2) and monosulfides (FeS), but also allowed for the absolute quantification of the various mineral phases. These analyses were carried out on magnetic extracts and density separates to be able to calculate budgets between the different present iron sulfides. We obtained excellent correlations between the different iron sulfide concentrations and the magnetic signal. Additional analyses on polished sections yield inside into the details of the sulfidization pathways along the depth profile of the sediment sequence and help to develop a more general process model for this particular geochemical (paleo-)environment. Keywords: Black Sea, iron sulfides, environmental magnetism, anaerobic oxidation of methane (AOM), scanning electron

  2. Accumulation and maternal transfer of polychlorinated biphenyls in Steller Sea Lions (Eumetopias jubatus) from Prince William Sound and the Bering Sea, Alaska.

    PubMed

    Wang, Jun; Hülck, Kathrin; Hong, Su-Myeong; Atkinson, Shannon; Li, Qing X

    2011-01-01

    The western stock of the Steller sea lion (Eumetopias jubatus) in the northern Pacific Ocean has declined by approximately 80% over the past 30 years. This led to the listing of this sea lion population as an endangered species in 1997. Chemical pollution is [corrected] one of several contributing causes. In the present study, 145 individual PCBs were determined in tissues of male sea lions from Tatitlek (Prince William Sound) and St. Paul Island (Bering Sea), and placentae from the Aleutian Islands. PCBs 90/101, 118, and 153 were abundant in all the samples. The mean toxic equivalents (TEQ) were 2.6, 4.7 and 7.4 pg/g lw in the kidney, liver, and blubber samples, respectively. The mean TEQ in placentae was 8 pg/g lw. Total PCBs concentrations (2.6-7.9 μg/g lw) in livers of some males were within a range known to cause physiological effects, further [corrected] suggesting the possibility of adverse effects on this stock.

  3. Foraging habitats of lactating northern fur seals are structured by thermocline depths and submesoscale fronts in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Nordstrom, Chad A.; Battaile, Brian C.; Cotté, Cédric; Trites, Andrew W.

    2013-04-01

    The relationships between fine-scale oceanographic features, prey aggregations, and the foraging behavior of top predators are poorly understood. We investigated whether foraging patterns of lactating northern fur seals (Callorhinus ursinus) from two breeding colonies located in different oceanographic domains of the eastern Bering Sea (St. Paul Island—shelf; Bogoslof Island—oceanic) were a function of submesoscale oceanographic features. We tested this by tracking 87 lactating fur seals instrumented with bio-logging tags (44 St. Paul Island, 43 Bogoslof Island) during July-September, 2009. We identified probable foraging hotspots using first-passage time analysis and statistically linked individual areas of high-use to fine-scale oceanographic features using mixed-effects Cox-proportional hazard models. We found no overlap in foraging areas used by fur seals from the two islands, but a difference in the duration of their foraging trips—trips from St. Paul Island were twice as long (7.9 d average) and covered 3-times the distance (600 km average) compared to trips from Bogoslof Island. St. Paul fur seals also foraged at twice the scale (mean radius=12 km) of Bogoslof fur seals (6 km), which suggests that prey were more diffuse near St. Paul Island than prey near Bogoslof Island. Comparing first passage times with oceanographic covariates revealed that foraging hotspots were linked to thermocline depth and occurred near submesoscale surface fronts (eddies and filaments). St. Paul fur seals that mixed epipelagic (night) and benthic (day) dives primarily foraged on-shelf in areas with deeper thermoclines that may have concentrated prey closer to the ocean floor, while strictly epipelagic (night) foragers tended to use waters with shallower thermoclines that may have aggregated prey closer to the surface. Fur seals from Bogoslof Island foraged almost exclusively over the Bering Sea basin and appeared to hunt intensively along submesoscale fronts that may have

  4. Development of a Seasonal Extratropical Cyclone Activity Outlook for the North Pacific, Bering Sea, and Alaskan Regions

    NASA Astrophysics Data System (ADS)

    Shippee, N. J.; Atkinson, D. E.; Walsh, J. E.; Partain, J.; Gottschalck, J.; Marra, J. J.

    2013-12-01

    Storm activity (i.e. 'storminess') and associated forecasting skill in the North Pacific, Bering Sea, and Alaska is relatively well understood on a daily to weekly scale, however, two important elements are missing from current capacity. First, there is no way to predict storm activity at the monthly to seasonal time frame. Second, storm activity is characterized in terms that best serve weather specialists, and which are often not very informative for different sectors of the public. Increasing the utility of forecasts for end users requires consultation with these groups, and can include expressing storm activity in terms of, for example, strong-wind return intervals or ship hull strength. These types of forecasts can provide valuable information for use in community planning, resource allocation, or potential risk assessment. A preliminary study of seasonal storminess predictability in the North Pacific and Alaska regions has shown that a key factor related to the annual variation of seasonal storminess is the strength of the Aleutian Low as measured using indices such as the North Pacific Index (NPI) or Aleutian Low Pressure Index (ALPI). Use of Empirical Orthogonal Function (EOF) analysis to identify patterns in storminess variability indicates that the primary mode of annual variation is found to be best explained by the variation in the strength of the Aleutian Low. NPI and the first component of storm activity for the entire region are found to be are highly correlated (R = 0.83). This result is supported by the works of others such as Rodionov et al. (2007), who note the impact of the strength of the Aleutian Low on storm track and speed. Additionally, the phase of the Pacific Decadal Oscillation (PDO), along with NPI, have been shown to be highly correlated with annual variance in the seasonal storminess for the North Pacific and Alaska. Additional skill has been identified when the phase of the Pacific Decadal Oscillation (PDO) is explicitly considered

  5. Comparison of environmental conditions in the Bering Sea and Davis Strait and the effects on microwave signature returns; March and April, 1979

    NASA Technical Reports Server (NTRS)

    Mcnutt, S. L.; Martin, S.

    1982-01-01

    Aircraft data collected in the Bering Sea in March, 1979 using a 6.6 GH sub z (C Band) microwave radiometer and a 13.9 GH sub z (Ku Band) scatterometer, reinforce the difficulties in interpreting first year ice types found near the ice edge in a marginal ice zone. An ice interpretation scheme using data taken with a 13.3 GH sub z (Ku Band) scatterometer and a 19.4 GH sub z (K Band) radiometer in Davis Strait also shows ambiguity in the first year ice signal and indicates that ice interpretation becomes more difficult near the ice edge and under warmer conditions. This report also compares X Band SAR data taken in Davis Strait with similar imagery collected in the Bering Sea. Ice core samples from the Bering test area offer a basis for speculation on changes in ice morphology which affect the signature return at the ice edge, and help explain the difficulty of the sensors in discerning the two different ice types found on the photography and in the core samples.

  6. Comparison of spring-time phytoplankton community composition in two cold years from the western Gulf of Alaska into the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Stauffer, Beth A.; Goes, Joaquim I.; McKee, Kali T.; do Rosario Gomes, Helga; Stabeno, Phyllis J.

    2014-11-01

    The Bering Sea is a highly productive ecosystem providing the main oceanographic connection between the North Pacific and Arctic oceans. The atmospheric connection with the Arctic Ocean leads to seasonal sea ice formation in the Bering Sea, the areal extent and timing of retreat of which have important implications for primary productivity and phytoplankton community composition in this region. Hydrographic data from cruises and satellite sea ice and sea surface temperature data in spring 2011 and 2012 suggest classification of these years as relatively warmer and colder years, respectively. Locations in the western Gulf of Alaska (Pavlof Bay), at the north end of an eastern pass through the Aleutian Islands (Unimak Pass), and on the continental shelf of the Bering Sea (M2) were visited in both years. Stratification was apparent on the shelf in 2012, while the water column was comparatively well-mixed at other locations in both years. Phytoplankton biomass was highest in 2011 overall and specifically on the shelf in both years, while minimal biomass was measured within the well-mixed Unimak Pass in 2012. Surface phytoplankton size distributions included substantial contributions of picoplankton (<3 μm) in 2011 (21-35%), while micro- (20-200 μm) and nanoplankton (3-20 μm) comprised 79% and 95% of biomass in Pavlof Bay and at M2, respectively, in 2012. Analyses of similarity revealed spatial variability in the phytoplankton assemblages within each year (2011: R=0.588, p<0.004; 2012: R=0.646, p<0.004). Additionally, between-year variability had a strong and significant effect on differences between assemblages across all locations (R=0.579, p<0.0003), likely masking differences between sites when years were grouped (R=0.134, p<0.079). These differences were likely driven by the dominance (up to 75% in Unimak Pass) of the colonial prymnesiophyte Phaeocystis sp. at all sites in 2011, resulting in reduced community diversity, compared to more widespread abundance of

  7. A comparison between late summer 2012 and 2013 water masses, macronutrients, and phytoplankton standing crops in the northern Bering and Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Danielson, Seth L.; Eisner, Lisa; Ladd, Carol; Mordy, Calvin; Sousa, Leandra; Weingartner, Thomas J.

    2017-01-01

    Survey data from the northern Bering and Chukchi sea continental shelves in August-September 2012 and 2013 reveal inter-annual differences in the spatial structure of water masses along with statistically significant differences in thermohaline properties, chemical properties, and phytoplankton communities. We provide a set of water mass definitions applicable to the northern Bering and Chukchi continental shelves, and we find that the near-bottom Bering-Chukchi Summer Water (BCSW) was more saline in 2012 and Alaskan Coastal Water (ACW) was warmer in 2013. Both of these water masses carried higher nutrient concentrations in 2012, supporting a larger chlorophyll a biomass that was comprised primarily of small (<10 μm) size class phytoplankton, so the classical relation between higher nutrient loads and larger phytoplankton does not hold for this region in late summer. The distributions of phytoplankton biomass and size structure reveal linkages between the wind fields, seafloor topography, water mass distributions and the pelagic production. The water mass structure, including the strength and location of stratification and fronts, respectively, differed primarily because of the August regional wind field, which was more energetic in 2012 but was more persistent in direction in 2013. High concentrations of ice in winter and early spring in 2012 and 2013 resembled conditions of the 1980s and early 1990s but the regional ice retreat rate has accelerated in the late 1990s and 2000s so the summer and fall ice concentrations more closely resembled those of the last two decades. Our data show that wind forcing can shut down the Alaskan Coastal Current in the NE Chukchi Sea for periods of weeks to months during the ice-covered winter and during the summer when buoyancy forcing is at its annual maximum. We hypothesize that a decrease in salinity and nutrients from 2012 to 2013 was a consequence of a decreased net Bering Strait transport from 2011 to 2012. Biological

  8. Preliminary genetic analysis of juvenile chum salmon from the Chukchi Sea and Bering Strait

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The arctic region has experienced warming in recent years, resulting in decreased summer sea ice cover and increased sea surface temperatures. In September 2007, the U.S. BASIS survey extended surface trawling into the Chukchi Sea. Juvenile (young-of-the-year) chum salmon were collected at most stat...

  9. Input of Terrestrial Palynomorphs since the Last Deglaciation from Sediments of the Chukchi Sea Shelf, Western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Delusina, I.; Kim, S. Y.; Nam, S. I.; Woo, K. S.

    2014-12-01

    We report the palynology of marine sediment core ARA02B/01A-GC from the Western margin of the shallow shelf of the Chukchi Sea in the Arctic, a site which was synchronously influenced by climatic changes during the last deglaciation with those in the Bering Strait. The core contains a rich concentration of continental palynomorphs, even though the coring location is quite a distance from land. The catchment area for the observed palynomorphs includes the territories of both North America (Alaska and North Canada) and Northern Siberia (Chukotka peninsula and Northern East-Siberian coast). Based on this fact, we can reconstruct a common paleoenvironmental history for this location and the Bering Strait during the postglacial interval. We hypothesize that palynomorphs were carried to the sea during low sea-ice coverage intervals by large rivers (Yukon, Mackenzie and Siberian rivers) and were then transferred by oceanic currents. During intervals of extensive sea-ice coverage the source of the palynomorphs was predominantly eroded shelf sediments. The percentage ratio of tree-herb pollen and spores in the palynomorph assemblages shows that favorable conditions for an increase in forest vegetation took place between ~8 and 4 kyr BP, which coincides with maximum freshwater input to the sea. During a climatic optimum at ~5 kyr BP, as inferred from the total dominance of tree and herb pollen, the Chukchi Sea was apparently warmer than today. This represents the maximum ice-free period for the sea. The low sea-ice interval ended ~3 kyr BP, as suggested by a sharp drop in tree pollen, a reduction in fresh water input, and a drop in the concentration of the algae Pediastrum. Our data correlate well with data from marine core HLY0501-5 from the Bering Strait (Polyak et al., 2009) for the interval of 10-8 kyr BP, but shows a divergence since ~4 kyr BP, which may correspond to the beginning of the differentiation of North American and East-Siberian ecosystem zones.

  10. Bering Sea millennial-scale climate variability during Marine Isotope Stages 22 and 21 (~900 ka): evidence for an active bipolar seesaw?

    NASA Astrophysics Data System (ADS)

    Kender, Sev; Hall, Ian R.; Becker, Julia; Aiello, Ivano W.; Radi, Taoufik; Asahi, Hirofumi

    2013-04-01

    The mid-Pleistocene transition (MPT), characterised by glacial intensification and lengthening, is marked by particularly abrupt ice sheet growth during the first ~100 ka glacial of Marine Isotope Stage (MIS) 22. Millennial-scale climate variability has been proposed to have become intensified during MPT glacials due to North American ice sheet growth beyond a critical size causing basal instability, but direct evidence for intensified millennial-scale climate variability during MIS 22 is so far lacking. In addition, evidence for an active 'bipolar seesaw' during the MPT has not yet been documented, despite this being a critical assumption in synthetically-produced Greenland ice core records. In this study we investigate MIS 22/21 (~910-840 ka) using high resolution (~0.3 ka) benthic foraminiferal oxygen isotopes (δ18O), ice-rafted debris (IRD) counts and lower resolution dinoflagellate cyst transfer functions for sea surface conditions, from Bering Sea Site U1343 (IODP Expedition 323, ~2 km water depth). During the transition from glacial MIS 22 to interglacial 21, surface water proxies indicate sea ice duration reduced, and productivity increased slightly, both indicative of warming sea surface temperatures during the deglacial. However, coincident with these shifts is a transient reversal (increase) in benthic δ18O, suggesting deep water briefly cooled. We suggest that the transient deglacial deep water cooling at Site U1343 implies a signal originating in the Southern Hemisphere (Ocean), as deep water in the Bering Sea is predominantly composed of Pacific Deep Water, which is sourced from Antarctic Bottom Water. Comparison with a similar resolution record from the North Atlantic (Site U1313) shows an equally transient increase in North Atlantic Deep Water (NADW) production occurred synchronously with the Bering Sea deep water cooling reversal. The coincident Bering Sea surface warming, Southern Ocean cooling, and NADW production increase is similar to the

  11. The Structure of Genetic Diversity in Eelgrass (Zostera marina L.) along the North Pacific and Bering Sea Coasts of Alaska

    PubMed Central

    Talbot, Sandra L.; Sage, George K; Rearick, Jolene R.; Fowler, Meg C.; Muñiz-Salazar, Raquel; Baibak, Bethany; Wyllie-Echeverria, Sandy; Cabello-Pasini, Alejandro; Ward, David H.

    2016-01-01

    Eelgrass (Zostera marina) populations occupying coastal waters of Alaska are separated by a peninsula and island archipelago into two Large Marine Ecosystems (LMEs). From populations in both LMEs, we characterize genetic diversity, population structure, and polarity in gene flow using nuclear microsatellite fragment and chloroplast and nuclear sequence data. An inverse relationship between genetic diversity and latitude was observed (heterozygosity: R2 = 0.738, P < 0.001; allelic richness: R2 = 0.327, P = 0.047), as was significant genetic partitioning across most sampling sites (θ = 0.302, P < 0.0001). Variance in allele frequency was significantly partitioned by region only in cases when a population geographically in the Gulf of Alaska LME (Kinzarof Lagoon) was instead included with populations in the Eastern Bering Sea LME (θp = 0.128–0.172; P < 0.003), suggesting gene flow between the two LMEs in this region. Gene flow among locales was rarely symmetrical, with notable exceptions generally following net coastal ocean current direction. Genetic data failed to support recent proposals that multiple Zostera species (i.e. Z. japonica and Z. angustifolia) are codistributed with Z. marina in Alaska. Comparative analyses also failed to support the hypothesis that eelgrass populations in the North Atlantic derived from eelgrass retained in northeastern Pacific Last Glacial Maximum refugia. These data suggest northeastern Pacific populations are derived from populations expanding northward from temperate populations following climate amelioration at the terminus of the last Pleistocene glaciation. PMID:27104836

  12. Bidecadal variability in the Bering Sea and the relation with 18.6 year period nodal tidal cycle

    NASA Astrophysics Data System (ADS)

    Osafune, S.; Yasuda, I.

    2010-02-01

    Bidecadal variations are investigated in the Bering Sea, especially in the southeastern basin adjacent to the Aleutian passes, where vertical mixing may be strong because of the diurnal tide. Those variations found in this region are synchronized with the 18.6 year period nodal tidal cycle, and the temporal patterns are similar to ones around the northwestern subarctic Pacific near the Kuril Straits reported by a previous study. Salinity and density in the upper layer are high in the periods when the diurnal tide is strong. In the intermediate layer, layer thickness is large, and isopycnal potential temperature and apparent oxygen utilization are low in the same periods. It is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing, and a simple two-dimensional model, assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current, succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer.

  13. Proximate composition, energetic value, and relative abundance of prey fish from the inshore eastern Bering Sea: Implications for piscivorous predators

    USGS Publications Warehouse

    Ball, J.R.; Esler, Daniel; Schmutz, J.A.

    2007-01-01

    Changing ocean conditions and subsequent shifts in forage fish communities have been linked to numerical declines of some piscivorous marine birds and mammals in the North Pacific. However, limited information about fish communities is available for some regions, including nearshore waters of the eastern Bering Sea, where many piscivores reside. We determined proximate composition and energetic value of a suite of potential forage fish collected from an estuary on the Yukon-Kuskokwim Delta, Alaska, during 2002 and 2003. Across species, energy density ranged from 14.5 to 20.7 kJ g−1 dry mass and varied primarily as a function of lipid content. Total energy content was strongly influenced by body length and we provide species-specific predictive models of total energy based on this relationship; some models may be improved further by incorporating year and date effects. Based on observed energetic differences, we conclude that variation in fish size, quantity, and species composition of the prey community could have important consequences for piscivorous predators.

  14. Spatial and temporal effects of salinity, temperature and chlorophyll on the communities of zooplankton in the southeastern Bering Sea

    SciTech Connect

    Smith, S.L.; Vidal, J.

    1984-01-01

    Analyses of 402 samples collected from late March through early June 1980 have shown that the two communities of zooplankton over the southeastern shelf of the Bering Sea are kept separate spatially by the lack of advection and frontal characteristics of the salinity distributions. The abundance of copepods over the middle shelf, between 50 and 100 m isobaths approximately, was highly correlated with seasonal warming of the surface layer, while abundances of copepods over the outer shelf and slope were not. The spring bloom of phytoplankton influenced abundances over the middle shelf more profoundly than the outer shelf; of the twelve taxa which composed most of the biomass of copepods over the middle shelf, eleven were significantly more abundant during the bloom than they were prior to the bloom. Over the outer shelf, only six of eighteen taxa were significantly more abundant during the bloom, and over the slope, three of eighteen. Differences in abundance of copepods between domains and among stations within each domain were greatest early in the study. During the study, stations of each domain became more similar in the abundance of their characteristic taxa. 43 references, 18 figures, 3 tables.

  15. Body Size Regression Formulae, Proximate Composition and Energy Density of Eastern Bering Sea Mesopelagic Fish and Squid

    PubMed Central

    2015-01-01

    The ecological significance of fish and squid of the mesopelagic zone (200 m–1000 m) is evident by their pervasiveness in the diets of a broad spectrum of upper pelagic predators including other fishes and squids, seabirds and marine mammals. As diel vertical migrators, mesopelagic micronekton are recognized as an important trophic link between the deep scattering layer and upper surface waters, yet fundamental aspects of the life history and energetic contribution to the food web for most are undescribed. Here, we present newly derived regression equations for 32 species of mesopelagic fish and squid based on the relationship between body size and the size of hard parts typically used to identify prey species in predator diet studies. We describe the proximate composition and energy density of 31 species collected in the eastern Bering Sea during May 1999 and 2000. Energy values are categorized by body size as a proxy for relative age and can be cross-referenced with the derived regression equations. Data are tabularized to facilitate direct application to predator diet studies and food web models. PMID:26287534

  16. Body Size Regression Formulae, Proximate Composition and Energy Density of Eastern Bering Sea Mesopelagic Fish and Squid.

    PubMed

    Sinclair, Elizabeth H; Walker, William A; Thomason, James R

    2015-01-01

    The ecological significance of fish and squid of the mesopelagic zone (200 m-1000 m) is evident by their pervasiveness in the diets of a broad spectrum of upper pelagic predators including other fishes and squids, seabirds and marine mammals. As diel vertical migrators, mesopelagic micronekton are recognized as an important trophic link between the deep scattering layer and upper surface waters, yet fundamental aspects of the life history and energetic contribution to the food web for most are undescribed. Here, we present newly derived regression equations for 32 species of mesopelagic fish and squid based on the relationship between body size and the size of hard parts typically used to identify prey species in predator diet studies. We describe the proximate composition and energy density of 31 species collected in the eastern Bering Sea during May 1999 and 2000. Energy values are categorized by body size as a proxy for relative age and can be cross-referenced with the derived regression equations. Data are tabularized to facilitate direct application to predator diet studies and food web models.

  17. The Structure of Genetic Diversity in Eelgrass (Zostera marina L.) along the North Pacific and Bering Sea Coasts of Alaska.

    PubMed

    Talbot, Sandra L; Sage, George K; Rearick, Jolene R; Fowler, Meg C; Muñiz-Salazar, Raquel; Baibak, Bethany; Wyllie-Echeverria, Sandy; Cabello-Pasini, Alejandro; Ward, David H

    2016-01-01

    Eelgrass (Zostera marina) populations occupying coastal waters of Alaska are separated by a peninsula and island archipelago into two Large Marine Ecosystems (LMEs). From populations in both LMEs, we characterize genetic diversity, population structure, and polarity in gene flow using nuclear microsatellite fragment and chloroplast and nuclear sequence data. An inverse relationship between genetic diversity and latitude was observed (heterozygosity: R2 = 0.738, P < 0.001; allelic richness: R2 = 0.327, P = 0.047), as was significant genetic partitioning across most sampling sites (θ = 0.302, P < 0.0001). Variance in allele frequency was significantly partitioned by region only in cases when a population geographically in the Gulf of Alaska LME (Kinzarof Lagoon) was instead included with populations in the Eastern Bering Sea LME (θp = 0.128-0.172; P < 0.003), suggesting gene flow between the two LMEs in this region. Gene flow among locales was rarely symmetrical, with notable exceptions generally following net coastal ocean current direction. Genetic data failed to support recent proposals that multiple Zostera species (i.e. Z. japonica and Z. angustifolia) are codistributed with Z. marina in Alaska. Comparative analyses also failed to support the hypothesis that eelgrass populations in the North Atlantic derived from eelgrass retained in northeastern Pacific Last Glacial Maximum refugia. These data suggest northeastern Pacific populations are derived from populations expanding northward from temperate populations following climate amelioration at the terminus of the last Pleistocene glaciation.

  18. Structure-forming corals and sponges and their use as fish habitat in Bering Sea submarine canyons.

    PubMed

    Miller, Robert J; Hocevar, John; Stone, Robert P; Fedorov, Dmitry V

    2012-01-01

    Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide.

  19. Structure-Forming Corals and Sponges and Their Use as Fish Habitat in Bering Sea Submarine Canyons

    PubMed Central

    Miller, Robert J.; Hocevar, John; Stone, Robert P.; Fedorov, Dmitry V.

    2012-01-01

    Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide. PMID:22470486

  20. North Pacific right whale up-call source levels and propagation distance on the southeastern Bering Sea shelf.

    PubMed

    Munger, Lisa M; Wiggins, Sean M; Hildebrand, John A

    2011-06-01

    Call source levels, transmission loss, and ambient noise levels were estimated for North Pacific right whale (Eubalaena japonica) up-calls recorded in the southeastern Bering Sea in autumn of 2000 and 2001. Distances to calling animals, needed to estimate source levels, were based on two independent techniques: (1) arrival-time differences on three or more hydrophones and (2) shallow-water dispersion of normal modes on a single receiver. Average root-mean-square (rms) call source levels estimated by the two techniques were 178 and 176 dB re 1 μPa at 1 m, respectively, over the up-call frequency band, which was determined per call and averaged 90 to 170 Hz. Peak-to-peak source levels were 14 to 22 dB greater than rms levels. Transmission loss was approximately 15∗log(10)(range), intermediate between cylindrical and spherical spreading. Ambient ocean noise within the up-call band varied from 72 to 91 dB re 1 μPa(2)/Hz. Under average noise conditions, call spectrograms were detectable for whales at distances up to 100 km, but propagation and detection distance may vary depending on environmental parameters and anthropogenic noise. Obtaining distances to animals and acoustic detection range is a step toward using long-term passive acoustic recordings to estimate abundance for this critically endangered whale population.

  1. Patterns in connectivity and retention of simulated Tanner crab (Chionoecetes bairdi) larvae in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Richar, Jonathan I.; Kruse, Gordon H.; Curchitser, Enrique; Hermann, Albert J.

    2015-11-01

    The eastern Bering Sea (EBS) population of Tanner crab (Chionoecetes bairdi) has exhibited high variability in recruitment to the commercially exploited stock since the late 1970s. Concurrently, apparent shifts in crab distribution have also been observed. Larval advection patterns and associated local retention offer a potential mechanism for these observations. The Regional Ocean Modeling System (ROMS) was used to simulate larval Tanner crab advection patterns over 1978-2004 based on larval hatching sites inferred from the distributions of reproductive females sampled during annual National Marine Fisheries Service trawl surveys. Connectivity among EBS subregions was examined by comparing start and end float locations after 60 days of simulated drift. High levels of retention (>50% of floats) were observed in the majority of source subregions, and contributed significantly to the total number of endpoints in each region. Patterns in advection and resultant interregional connectivity were variable, with strongest sustained connectivity occurring along shelf, within individual domains. Increased settlement potential in the outer domain and southern middle domain after 1990 is consistent with an observed geographic shift in fishery productivity. Apparent reliance of Bristol Bay on local larval retention validates recent spatial fishery management to conserve this area as a subpopulation.

  2. The Structure of Genetic Diversity in Eelgrass (Zostera marina L.) along the North Pacific and Bering Sea Coasts of Alaska

    USGS Publications Warehouse

    Talbot, Sandra; Sage, Kevin; Rearick, Jolene; Fowler, Megan C.; Muñiz-Salazar, Raquel; Baibak, Bethany; Wyllie-Echeverria, Sandy; Cabello-Pasini, Alehandro; Ward, David H.

    2016-01-01

    Eelgrass (Zostera marina) populations occupying coastal waters of Alaska are separated by a peninsula and island archipelago into two Large Marine Ecosystems (LMEs). From populations in both LMEs, we characterize genetic diversity, population structure, and polarity in gene flow using nuclear microsatellite fragment and chloroplast and nuclear sequence data. An inverse relationship between genetic diversity and latitude was observed (heterozygosity: R2 = 0.738, P < 0.001; allelic richness: R2 = 0.327, P = 0.047), as was significant genetic partitioning across most sampling sites (θ = 0.302, P < 0.0001). Variance in allele frequency was significantly partitioned by region only in cases when a population geographically in the Gulf of Alaska LME (Kinzarof Lagoon) was instead included with populations in the Eastern Bering Sea LME (θp = 0.128–0.172; P < 0.003), suggesting gene flow between the two LMEs in this region. Gene flow among locales was rarely symmetrical, with notable exceptions generally following net coastal ocean current direction. Genetic data failed to support recent proposals that multiple Zostera species (i.e. Z. japonica and Z. angustifolia) are codistributed with Z. marina in Alaska. Comparative analyses also failed to support the hypothesis that eelgrass populations in the North Atlantic derived from eelgrass retained in northeastern Pacific Last Glacial Maximum refugia. These data suggest northeastern Pacific populations are derived from populations expanding northward from temperate populations following climate amelioration at the terminus of the last Pleistocene glaciation.

  3. Foraging responses of black-legged kittiwakes to prolonged food-shortages around colonies on the Bering Sea shelf.

    PubMed

    Paredes, Rosana; Orben, Rachael A; Suryan, Robert M; Irons, David B; Roby, Daniel D; Harding, Ann M A; Young, Rebecca C; Benoit-Bird, Kelly; Ladd, Carol; Renner, Heather; Heppell, Scott; Phillips, Richard A; Kitaysky, Alexander

    2014-01-01

    We hypothesized that changes in southeastern Bering Sea foraging conditions for black-legged kittiwakes (Rissa tridactyla) have caused shifts in habitat use with direct implications for population trends. To test this, we compared at-sea distribution, breeding performance, and nutritional stress of kittiwakes in three years (2008-2010) at two sites in the Pribilof Islands, where the population has either declined (St. Paul) or remained stable (St. George). Foraging conditions were assessed from changes in (1) bird diets, (2) the biomass and distribution of juvenile pollock (Theragra chalcogramma) in 2008 and 2009, and (3) eddy kinetic energy (EKE; considered to be a proxy for oceanic prey availability). In years when biomass of juvenile pollock was low and patchily distributed in shelf regions, kittiwake diets included little or no neritic prey and a much higher occurrence of oceanic prey (e.g. myctophids). Birds from both islands foraged on the nearby shelves, or made substantially longer-distance trips overnight to the basin. Here, feeding was more nocturnal and crepuscular than on the shelf, and often occurred near anticyclonic, or inside cyclonic eddies. As expected from colony location, birds from St. Paul used neritic waters more frequently, whereas birds from St. George typically foraged in oceanic waters. Despite these distinctive foraging patterns, there were no significant differences between colonies in chick feeding rates or fledging success. High EKE in 2010 coincided with a 63% increase in use of the basin by birds from St. Paul compared with 2008 when EKE was low. Nonetheless, adult nutritional stress, which was relatively high across years at both colonies, peaked in birds from St. Paul in 2010. Diminishing food resources in nearby shelf habitats may have contributed to kittiwake population declines at St Paul, possibly driven by increased adult mortality or breeding desertion due to high foraging effort and nutritional stress.

  4. Foraging Responses of Black-Legged Kittiwakes to Prolonged Food-Shortages around Colonies on the Bering Sea Shelf

    PubMed Central

    Paredes, Rosana; Orben, Rachael A.; Suryan, Robert M.; Irons, David B.; Roby, Daniel D.; Harding, Ann M. A.; Young, Rebecca C.; Benoit-Bird, Kelly; Ladd, Carol; Renner, Heather; Heppell, Scott; Phillips, Richard A.; Kitaysky, Alexander

    2014-01-01

    We hypothesized that changes in southeastern Bering Sea foraging conditions for black-legged kittiwakes (Rissa tridactyla) have caused shifts in habitat use with direct implications for population trends. To test this, we compared at-sea distribution, breeding performance, and nutritional stress of kittiwakes in three years (2008–2010) at two sites in the Pribilof Islands, where the population has either declined (St. Paul) or remained stable (St. George). Foraging conditions were assessed from changes in (1) bird diets, (2) the biomass and distribution of juvenile pollock (Theragra chalcogramma) in 2008 and 2009, and (3) eddy kinetic energy (EKE; considered to be a proxy for oceanic prey availability). In years when biomass of juvenile pollock was low and patchily distributed in shelf regions, kittiwake diets included little or no neritic prey and a much higher occurrence of oceanic prey (e.g. myctophids). Birds from both islands foraged on the nearby shelves, or made substantially longer-distance trips overnight to the basin. Here, feeding was more nocturnal and crepuscular than on the shelf, and often occurred near anticyclonic, or inside cyclonic eddies. As expected from colony location, birds from St. Paul used neritic waters more frequently, whereas birds from St. George typically foraged in oceanic waters. Despite these distinctive foraging patterns, there were no significant differences between colonies in chick feeding rates or fledging success. High EKE in 2010 coincided with a 63% increase in use of the basin by birds from St. Paul compared with 2008 when EKE was low. Nonetheless, adult nutritional stress, which was relatively high across years at both colonies, peaked in birds from St. Paul in 2010. Diminishing food resources in nearby shelf habitats may have contributed to kittiwake population declines at St Paul, possibly driven by increased adult mortality or breeding desertion due to high foraging effort and nutritional stress. PMID:24671108

  5. Iron Sulfide Minerals in Black Sea Sediments

    NASA Astrophysics Data System (ADS)

    Franke, Christine; Robin, Eric; Henkel, Susann; Courtin-Nomade, Alexandra; Bleil, Ulrich

    2010-05-01

    This study presents a mutidisciplinary geochemical and environmental magnetic approach, integrating advanced mineralogical techniques to better understand the physicochemical syn-sedimentary and post-depositional processes in the anoxic sediments from the northwestern Black Sea. The investigated gravity core GC 214 was retrieved in 2007 during RV METEOR cruise M72/1 west of the Crimean Peninsula in a water depth of 1686 mbsf. Geochemical analyses of the pore water and solid phase indicate non-steady state sedimentation. The oxygen-depleted water column conditions, anaerobic oxidation of methane (AOM), and related microbial-driven sulfate reduction favor a highly complex iron sulfide mineral assemblage in the sediment column. The detailed magnetic susceptibility and remanence measurements indicate an irregularly stratified depth profile showing intervals of particularly high values. Further environmental magnetic analyses of hysteresis loops depict strongly elevated coercivity values for those depth horizons, suggesting metastable ferrimagnetic greigite (Fe3S4) as the main magnetic carrier phase. Automated chemical classification (ACC), using electron dispersive spectrometer (EDS) attached to a JEOL 840 scanning electron microscope (SEM) on dispersed particle samples permitted the absolutequantification of the various present iron mineral phases with depth, identified as greigite (Fe3S4), pyrrhotite (Fe7S8), pyrite (FeS2), and monosulfides (FeS), such as troilite or markasite. The statistically stable ACC analyses were carried out on magnetic extracts and density separates to be able to calculate budgets between the different present iron sulfides. We also obtained excellent correlations between the different iron sulfide concentrations and the magnetic signal, which open the possibility to link the absolute particle concentrations to the magnetic signal. Additional synchrotron based micro-XRD analyses on polished sections yield inside into the details of the

  6. Taxonomy of the early life stages of arrowtooth flounder (Atheresthes stomias) and Kamchatka flounder (A. evermanni) in the eastern Bering Sea, with notes on distribution and condition

    NASA Astrophysics Data System (ADS)

    De Forest, Lisa; Duffy-Anderson, J. T.; Heintz, R. A.; Matarese, A. C.; Siddon, E. C.; Smart, T. I.; Spies, I. B.

    2014-11-01

    Arrowtooth flounder (Atheresthes stomias) and Kamchatka flounder (A. evermanni) are closely related flatfish species that co-occur in the eastern Bering Sea. As adults, arrowtooth flounder can be distinguished from Kamchatka flounder; however, larvae and early juveniles can only be indentified to the genus level due to morphological similarities. This has precluded studies of ecology for the early life stages of both species in the eastern Bering Sea. In this study, we developed a genetic technique to identify the larvae and early juveniles of the two species using mtDNA cytochrome oxidase subunit I (COI). Genetically identified specimens were then examined to determine a visual identification method based on pigment patterns and morphology. Specimens 6.0-12.0 mm SL and≥18.0 mm SL can be identified to the species level, but species identification of individuals 12.1-17.9 mm SL by visual means alone remains elusive. The distribution of larvae (<25.0 mm SL) of both arrowtooth flounder and Kamchatka flounder is similar in the eastern Bering Sea; however, juvenile (≥25.0 mm SL) Kamchatka flounder occur closer to the shelf break and in deeper water than juvenile arrowtooth flounder. Condition was determined for larvae and juveniles of each species by analyzing lipid content (%) and energy density (kJ/g dry mass). Kamchatka flounder larvae on average had higher lipid content than arrowtooth flounder larvae, but were also larger on average than arrowtooth flounder larvae in the summer. When corrected for length, both species had similar lipid content in the larval and juvenile stages.

  7. Fluorescence, pigment and microscopic characterization of Bering Sea phytoplankton community structure and photosynthetic competency in the presence of a Cold Pool during summer

    NASA Astrophysics Data System (ADS)

    Goes, Joaquim I.; Gomes, Helga do Rosario; Haugen, Elin M.; McKee, Kali T.; D'Sa, Eurico J.; Chekalyuk, Alexander M.; Stoecker, Diane K.; Stabeno, Phyllis J.; Saitoh, Sei-Ichi; Sambrotto, Raymond N.

    2014-11-01

    Spectral fluorescence measurements of phytoplankton chlorophyll a (Chl a), phytoplankton phycobilipigments and variable fluorescence (Fv/Fm), are utilized with High Performance Liquid Chromatography (HPLC) estimates of phytoplankton pigments and microscopic cells counts to construct a comprehensive picture of summer-time phytoplankton communities and their photosynthetic competency in the eastern Bering Sea shelf. Although the Bering Sea was ice-free during our study, the exceptionally cold winter that preceded the summer of 2008 when our cruise took place, facilitated the formation of a "Cold Pool" (<2 °C) and its entrapment at depth in the northern middle shelf. The presence of a strong pycnocline over the entire middle and outer shelves restricted inorganic nutrient fluxes into the surface waters resulting in phytoplankton populations that were photo-physiologically stressed due to nutrient limitation. Elevated Chl a concentrations recorded in the Green Belt along the shelf edge of the Bering Sea, were due to Phaeocystis pouchetii and nano-sized cryptophytes. Although inorganic nutrients were not limiting in the Green Belt, Fv/Fm values were low in all probability due to iron limitation. Phytoplankton communities in the low biomass surface waters of the middle shelf were comprised of prasinophytes, haptophytes, cryptophytes and diatoms. In the northern part of the middle shelf, a sinking bloom made up of the centric diatoms Chaeotoceros socialis, Thalassiosira nordenskioeldii and Porosira glacialis was located above the Cold Pool. The high biomass associated with this senescent bloom and its accretion above the pycnocline, suggests that the Cold Pool acts as a barrier, preventing sinking phytoplankton from reaching the bottom where they can become available to benthic organisms. We further posit that if summer-time storms are not energetic enough and the Cold Pool is not eroded, its presence facilitates the transfer of the large spring phytoplankton bloom to

  8. Puzzling mass movement features in the Navarinsky Canyon head, Bering Sea

    USGS Publications Warehouse

    Carlson, P.R.; Karl, Herman A.; Edwards, B.D.

    1982-01-01

    Two types of morphologic features in the head of Navarinsky Canyon are attributed to mass movement of near-surface sediment. A series of pull-aparts is located downslope of large sand waves. These pull-aparts, possibly induced by liquefaction, affect the upper 5 to 10 m of sandy sediment (water depths 350 to 600 m) on a 1o slope. A hummocky elongate mound of muddy sand (water depths 550 to 800 m) contains chaotic internal reflectors to a subbottom depth of 30 to 40 m and possibly is the product of a shallow slide. We speculate that Holocene seismicity is the likely triggering mechanism. ?? 1982 A. M. Dowden, Inc.

  9. Platinum group nuggets in deep sea sediments

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.; Bates, B. A.; Wheelock, M. M.

    1984-01-01

    The existence of iron meteor oblation spheres in deep sea sediments was known for over a century. These spheres generally were believed to be composed of either pure magnetite and wustite or an oxide shell surrounding a NiFe metal core. A large number of 300 micron to 600 micron spheres found were pure oxide spheres, usually containing a solitary 10 micron platinum group nugget (pgn) composed almost entirely of group VIII metals. Twelve PGN's were analyzed and most had chondritic abundances with some depletions that correlate with element volatility. PGN formation by oxidation of a molten metal sphere entering the atmosphere cannot occur if the oxygen abundance in the atmosphere is less than half of its present value. The first appearance of PGN's in the geological record should mark when, in the Earth's history, oxygen rose to this level.

  10. Updated analysis of flatfish recruitment response to climate variability and ocean conditions in the Eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Wilderbuer, Thomas; Stockhausen, William; Bond, Nicholas

    2013-10-01

    This study provides a retrospective analysis of the relationship between physical oceanography, biology and recruitment of three Eastern Bering Sea flatfish stocks: flathead sole (Hippoglossoides elassodon), northern rock sole (Lepidopsetta polyxystra), and arrowtooth flounder (Atheresthes stomias) during the period 1978-2005. Stock assessment model estimates of recruitment and spawning stock size indicate that temporal patterns in productivity are consistent with decadal scale (or shorter) patterns in climate variability, which may influence marine survival during the early life history phases. Density-dependence (through spawning stock size) was statistically significant in a Ricker stock-recruit model of flatfish recruitment that included environmental terms. Wind-driven advection of northern rock sole and flathead sole larvae to favorable nursery grounds was found to coincide with years of above-average recruitment. Ocean forcing of Bristol Bay surface waters during springtime was mostly on-shelf (eastward) during the 1980s and again in the early 2000s, but was off-shelf (westerly) during the 1990s, corresponding with periods of good and poor recruitment, respectively. Finally, the Arctic Oscillation was found to be an important indicator of arrowtooth flounder productivity. Model results were applied to IPCC (Intergovernmental Panel on Climate Change) future springtime wind scenarios to predict the future impact of climate on northern rock sole productivity and indicated that a moderate future increase in recruitment might be expected because the climate trends favor on-shelf transport but that density-dependence will dampen this effect such that northern rock sole abundance will not be substantially affected by climate change.

  11. Vertical changes in abundance, biomass and community structure of copepods down to 3000 m in the southern Bering Sea

    NASA Astrophysics Data System (ADS)

    Homma, Tomoe; Yamaguchi, Atsushi

    2010-08-01

    Vertical changes in abundance, biomass and community structure of copepods down to 3000 m depth were studied at a single station of the Aleutian Basin of the Bering Sea (53°28'N, 177°00'W, depth 3779 m) on the 14th June 2006. Both abundance and biomass of copepods were greatest near the surface layer and decreased with increase in depth. Abundance and biomass of copepods integrated over 0-3000 m were 1,390,000 inds. m -2 and 5056 mg C m -2, respectively. Copepod carcasses occurred throughout the layer, and the carcass:living specimen ratio was the greatest in the oxygen minimum layer (750-100 m, the ratio was 2.3). A total of 72 calanoid copepod species belonging to 34 genera and 15 families occurred in the 0-3000 m water column (Cyclopoida, Harpacticoida and Poecilostomatoida were not identified to species level). Cluster analysis separated calanoid copepod communities into 5 groups (A-E). Each group was separated by depth, and the depth range of each group was at 0-75 m (A), 75-500 m (B), 500-750 m (C), 750-1500 m (D) and 1500-3000 m (E). Copepods were divided into four types based on the feeding pattern: suspension feeders, suspension feeders in diapause, detritivores and carnivores. In terms of abundance the most dominant group was suspension feeders (mainly Cyclopoida) in the epipelagic zone, and detritivores (mainly Poecilostomatoida) were dominant in the meso- and bathypelagic zones. In terms of biomass, suspension feeders in diapause (calanoid copepods Neocalanus spp. and Eucalanus bungii) were the major component (ca. 10-45%), especially in the 250-3000 m depth. These results are compared with the previous studies in the same region and that down to greater depths in the worldwide oceans.

  12. Evidence of prolonged aragonite undersaturations in the bottom waters of the southern Bering Sea shelf from autonomous sensors

    NASA Astrophysics Data System (ADS)

    Mathis, Jeremy T.; Cross, Jessica N.; Monacci, Natalie; Feely, Richard A.; Stabeno, Phyllis

    2014-11-01

    The southeastern shelf of the Bering Sea is a dynamic area that experiences seasonal variability in primary production and remineralization of organic matter, both of which control the carbon biogeochemistry of the water column. Surface-water partial pressure of carbon dioxide (pCO2) is greatly reduced in summer by biological production, which increases carbonate mineral saturation states (Ω). In contrast, the export of large quantities of organic matter from surface blooms drives an active remineralization loop that sharply increases pCO2 near the bottom, lowering pH and suppressing Ω. New observations from moored biogeochemical sensors in 2011 showed that seasonal net community production lowers surface-water pCO2, causing large gradients between the ocean and atmosphere that are sustained throughout the summer, confirming that these waters likely remain supersaturated with respect to aragonite throughout the open water season. On the other hand, moored sensors deployed near the bottom showed that pCO2 levels exceed 500 μatm by early June and remain at these high levels well into the autumn months, indicating that the bottom waters are likely continuously undersaturated in aragonite for at least several months during each year. Only a small fraction of the increased pCO2 can currently be attributed to the intrusion of anthropogenic CO2 from the atmosphere, while the majority is due to natural respiration processes. The biological impacts, along with the timing and duration of these undersaturation events, could play a role in the development of larval and juvenile calcifiers in the region and will change as anthropogenic CO2 concentrations continue to rise.

  13. Holocene palynomorph records since the last deglaciation from the Chukchi Sea shelf sediments, western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Kim, So-Young; Nam, Seung-Il; Polyak, Leonid; Delusina, Irina

    2015-04-01

    Organic-walled microscopic organisms in marine sediments such as dinoflagellate cysts, pollen, spores and freshwater algae from the Chukchi Sea shelf sediment document spatial and temporal variations in the paleoenvironmental history in relation to regional climatic changes during the Holocene. The records presented here are derived from a sediment core from the shallow shelf of the Chukchi Sea in the western Arctic (core ARA02B/01A-GC), a site which allows us to assess the timing of the Bering Strait opening and its influence over the regional environmental system during the last post glacial interval. The sediment core contains a rich concentration of terrestrially derived pollen and spores, indicating considerable changes in vegetation over the catchment area including the territories of both North America (Alaska and Northern Canadian Arctic) and Northern Siberia (Chukotka peninsula and Northern East-Siberian coast) during the last 10 kyr BP. We speculate that the palynomorphs were predominantly supplied from eroded shelf sediments during intervals of extensive sea-ice coverage, while they were carried to the shelves by large rivers (Yukon, Mackenzie and Siberian rivers) and then transferred by oceanic currents during low sea-ice coverage intervals. In particular, the percentage ratio between tree-herb pollen and spores, and the algae Pediastrum in the palynomorph assemblages represent significant changes in the western Arctic vegetation associated with freshwater inputs, including increased forest vegetation between ~8 and 4 kyr BP, a climatic optimum at ~5 kyr BP and a termination of the low sea-ice interval at ~3 kyr BP. In parallel, marine palynomorphs (dinoflagellate cysts) document significant changes in the marine environments, typically for a prominent increase in dinoflagellate cyst concentrations as well as total organic carbon and nitrogen contents since ca. 8 kyr BP suggesting increased nutrient inputs and marine productivity in the study area. Our

  14. Differential responses of seabirds to environmental variability over 2 years in the continental shelf and oceanic habitats of southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takashi; Kokubun, Nobuo; Kikuchi, Dale M.; Sato, Nobuhiko; Takahashi, Akinori; Will, Alexis P.; Kitaysky, Alexander S.; Watanuki, Yutaka

    2016-04-01

    Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to different marine environmental conditions over 2 years. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. Between the study years, winter ice retreated earlier and summer water temperatures were relatively warmer in 2014 compared to those in 2013. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf but showed a relatively higher use of the shelf break and oceanic basin in 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and bimodally at 150-250 and 300-350 km in 2014 for RLKI and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between the years in RLKI but differed in TBMU, showing higher levels of physiological stress incurred by murres in 2013, the year of relatively cooler sea surface temperatures with later sea-ice retreat. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU. These results suggest that the response of ecosystem dynamics to climate variability in the southeastern Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those habitats for foraging.

  15. Paleogeographic sedimentation settings in the northern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Trimonis, E. S.; Emelyanov, E. M.; Vaikutene, G.

    2008-10-01

    The grain-size and chemical composition of the bottom sediments and their diatom assemblages from the northern Baltic Sea is discussed. Characteristic layers are distinguished based on the lithostratgraphy and sediment core correlation, which reflect the transition from the lacustrine to marine sedimentation settings during the initial Holocene. Sediment cores demonstrate lateral variations in the sedimentation patterns during the marine (Yoldia Sea), the lacustrine (Ancylus Lake), and the subsequent marine (Littorina Sea) stages: first two stages were characterized by the clay deposition, while the latter one featured accumulation of silty-clayey and clayey muds in bottom depressions. Sea-level fluctuations and corresponding environmental changes are recorded in microlaminated sequences, in particular, sapropelic muds.

  16. Bering Sea Wave and Ice Measurements in Support of Arctic West Winter 1986

    DTIC Science & Technology

    1988-04-01

    Basic Results and Prospects on Hydro- Meteorological Conditions of Shipboard Icing ." Investigation of the Physical Nature of Ship...effect on radar systems. Shipboard icing can result from a variety of causes as indicated in References • 8 and 9. These include: "* ; a. Supercooled...Shekhtman, A.N., " Hydrometeorological Conditions in the Icing -Up of Vessels at Sea," Naval Scientific and Technical Information Center (U.K.), Translation

  17. Bering Strait

    Atmospheric Science Data Center

    2014-05-15

    ... west, the Bering Strait separates the United States and the Russian Federation by only 90 kilometers. It is named for Danish explorer Vitus ... the Alaskan mainland in 1741 while leading an expedition of Russian sailors. This view of the region was captured by the Multi-angle ...

  18. Climate change, pink salmon, and the nexus between bottom-up and top-down forcing in the subarctic Pacific Ocean and Bering Sea.

    PubMed

    Springer, Alan M; van Vliet, Gus B

    2014-05-06

    Climate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem.

  19. A multivariate analysis of observed and modeled biophysical variability on the Bering Sea shelf: Multidecadal hindcasts (1970-2009) and forecasts (2010-2040)

    NASA Astrophysics Data System (ADS)

    Hermann, Albert J.; Gibson, Georgina A.; Bond, Nicholas A.; Curchitser, Enrique N.; Hedstrom, Kate; Cheng, Wei; Wang, Muyin; Stabeno, Phyllis J.; Eisner, Lisa; Cieciel, Kristin D.

    2013-10-01

    Coupled physical/biological models can be used to downscale global climate change to the ecology of subarctic regions, and to explore the bottom-up and top-down effects of that change on the spatial structure of subarctic ecosystems—for example, the relative dominance of large vs. small zooplankton in relation to ice cover. Here we utilize a multivariate statistical approach to extract the emergent properties of a coupled physical/biological hindcast of the Bering Sea for years 1970-2009, which includes multiple episodes of warming and cooling (e.g. the recent cooling of 2005-2009), and a multidecadal regional forecast of the coupled models, driven by an IPCC global model forecast of 2010-2040. Specifically, we employ multivariate empirical orthogonal function (EOF) analysis to derive the spatial covariance among physical and biological timeseries from our simulations. These are compared with EOFs derived from spatially gridded measurements of the region, collected during multiyear field programs. The model replicates observed relationships among temperature and salinity, as well as the observed inverse correlation between temperature and large crustacean zooplankton on the southeastern Bering Sea shelf. Predicted future warming of the shelf is accompanied by a northward shift in both pelagic and benthic biomass.

  20. Climate change, pink salmon, and the nexus between bottom-up and top-down forcing in the subarctic Pacific Ocean and Bering Sea

    PubMed Central

    Springer, Alan M.; van Vliet, Gus B.

    2014-01-01

    Climate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem. PMID:24706809

  1. Sediment Bacterial Communities Reflect the History of a Sea Basin

    PubMed Central

    Lyra, Christina; Sinkko, Hanna; Rantanen, Matias; Paulin, Lars; Kotilainen, Aarno

    2013-01-01

    How entire microbial communities are structured across stratified sediments from the historical standpoint is unknown. The Baltic Sea is an ideal research object for historical reconstruction, since it has experienced many fresh- and brackish water periods and is depleted of dissolved oxygen, which increases the sediment's preservation potential. We investigated the bacterial communities, chemical elements (e.g. Cr, Pb Na, P, Sr and U) and sediment composition in a stratified sediment core dated by radiocarbon and spanning 8000 years of Baltic Sea history, using up-to-date multivariate statistics. The communities were analysed by 16S rRNA gene terminal restriction fragment length polymorphism. The communities of the deep Early Litorina and surface Late Litorina Sea laminae were separated from the communities of the middle Litorina Sea laminae, which were associated with elevated concentrations of U and Sr trace elements, palaeo-oxygen and palaeosalinity proxies. Thus, the Litorina Sea laminae were characterized by past oxygen deficiency and salinity increase. The communities of the laminae, bioturbated and homogeneous sediments were differentiated, based on the same historical sea phases, with correct classifications of 90%. Palaeosalinity was one of the major parameters that separated the bacterial communities of the stratified sediments. A discontinuous spatial structure with a surprising increase in community heterogeneity was detected in Litorina Sea sediments from 388 to 422 cm deep, which suggests that a salinity maximum occurred in the central Gulf of Finland app. 6200–6600 years ago. The community heterogeneity decreased from the surface down to 306 cm, which reflected downcore mineralization. The plateau of the decrease was in the app. 2000-year-old sediment layers. Bacterial community data may be used as an additional tool in ocean-drilling projects, in which it is important to detect mineralization plateaus both to determine historically comparable

  2. Fungi and macroaggregation in deep-sea sediments.

    PubMed

    Damare, Samir; Raghukumar, Chandralata

    2008-07-01

    Whereas fungi in terrestrial soils have been well studied, little is known of them in deep-sea sediments. Recent studies have demonstrated the presence of fungal hyphae in such sediments but in low abundance. We present evidence in this study that one of the apparent reasons for the poor detection of fungi in deep-sea sediments is their cryptic presence in macroaggregates. Fungal biomass carbon from different core sections of deep-sea sediments from approximately 5000 m depth in the Central Indian Ocean was estimated based on direct microscopic detection of fungal mycelia. Treatment of sediment samples with ethylenediamine tetra-acetic acid (EDTA) enabled more frequent detection and significantly higher biomass than in samples without such treatment. Treatment with EDTA resulted in detecting various stages of breakdown of aggregates in the sediments, gradually revealing the presence of fungal hyphae within them. Experimental studies of a deep-sea, as well as three terrestrial isolates of fungi, showed that all could grow at 200 bar and 5 degrees C in a nutrient medium and in deep-sea sediment extract. Hyphae of fungi grown in sediment extract under the above conditions showed various stages of accretion of particles around them, leading to the formation of aggregates. Such aggregates showed the presence of humic material, carbohydrate, and proteins. We suggest that fungi in deep-sea sediments may be involved in humic aggregate formation by processes very similar to those in terrestrial sediments. The importance of such a process in carbon sequestration and food web in the deep sea needs to be examined.

  3. 76 FR 13593 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-14

    ... (AFA) of 1998 (Public Law 105-277, Title II of Division C); and (3) meet one or both of the following.... Vessels that meet these criteria subsequently will be referred to as ``non-AFA crab vessels.'' The CR Program did not establish sideboard limits for AFA vessels with historical participation in the Bering...

  4. 76 FR 17088 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-28

    ... authorized to conduct directed fishing for pollock under the American Fisheries Act (AFA) of 1998 (Public Law.... Vessels that meet these criteria subsequently will be referred to as ``non-AFA crab vessels.'' The CR Program did not establish sideboard limits for AFA vessels with historical participation in the Bering...

  5. Nutrient Enrichment Coupled with Sedimentation Favors Sea Anemones over Corals

    PubMed Central

    Liu, Pi-Jen; Hsin, Min-Chieh; Huang, Yen-Hsun; Fan, Tung-Yung; Meng, Pei-Jie; Lu, Chung-Cheng; Lin, Hsing-Juh

    2015-01-01

    Fine sediments, which account for the majority of total fluvial sediment flux, have been suggested to degrade coral reefs on a global scale. Furthermore, sediment impacts can be exacerbated by extreme rainfall events associated with global climate change and anthropogenic nutrient enrichment. We report the findings from a series of mesocosm experiments exploring the effects of short-term sedimentation and nutrient enrichment on the interactions between the hard coral Acropora muricata, the sea anemone Mesactinia ganesis, and the green macroalga Codium edule. Mesocosms were manipulated to simulate either unimpacted reefs or reefs exposed to elevated levels of fine sediments for 10 or 14 days to simulate the effects of heavy rainfall. The first and second experiments were aimed to examine the effects of inorganic and organic sediments, respectively. The third experiment was designed to examine the interactive effects of nutrient enrichment and elevated sediment loads. Neither inorganic nor organic sediment loadings significantly affected the physiological performance of the coral, but, importantly, did reduce its ability to compete with other organisms. Photosynthetic efficiencies of both the green macroalga and the sea anemone increased in response to both sediment loadings when they were simultaneously exposed to nutrient enrichment. While organic sediment loading increased the nitrogen content of the green macroalga in the first experiment, inorganic sediment loading increased its phosphorus content in the second experiment. The coral mortality due to sea anemones attack was significantly greater upon exposure to enriched levels of organic sediments and nutrients. Our findings suggest that the combined effects of short-term sedimentation and nutrient enrichment could cause replacement of corals by sea anemones on certain coral reefs. PMID:25897844

  6. New Scientific Drilling in the Bering Sea--Results Imply Contribution of Thermogenic Methane to Beringian Margin BSR and Miocene Termination of Subduction Beneath Bowers Ridge

    NASA Astrophysics Data System (ADS)

    Scholl, D. W.

    2011-12-01

    METHANE BENEATH THE BERINGIAN MARGIN: Based on an acoustically prominent BSR (~450 m), it has long been surmised that large volumes of methane gas and methane hydrate occur within the Cenozoic deposits that thickly (5-10 km) drape the Beringian continental margin. In 2009, IODP Exp. 323 drilled three sites along the margin to recover the late Cenozoic paleoceanographic history stored there. On deck, warming sediment cores vigorously released interstitial methane gas. Disassociation of pore-space methane hydrate was inferred, but hydrate was not visually seen. P/T conditions at the BSR (24 C at 360 bars) matched those of the expected phase transition from methane gas below to methane hydrate above. Reflection records below bright sectors of the BSR display gas-blanking effects traceable to subsurface depths of several km, at which the thermal gradient of 50-55 deg C/km implies thermogenic methane would be generated. Since at least the early Miocene, surface water overlying the Beringian margin has been a biologically productive garden spot. Large quantities of organic matter can be expected to have accumulated in the underlying slope deposits. Deep, glacial-age canyon cutting, normal faulting, and diagenetic fracturing of siliceous shale (opal-A to opal-CT) provide venting paths for deep-generated methane. It is posited that ascending thermogenic methane importantly nourishes the sub-margin hydrate BSR. END OF SUBDUCTION AND ARC VOLCANISM AT BOWERS RIDGE: Submarine Bowers Ridge, which is not volcanically active, projects oddly northward and curvingly westward into the Bering Sea Basin from the mid point of the Aleutian Arc. The ridge rises as high as 3500 m to flatten near 600 m at wave-planed platforms cut across basement rock. The ridge's magnetic, velocity, and gravity characteristics are typical of an arc massif. A sediment-filled, trench-shaped trough along the base of the ridge's northern flank implies a former subduction zone underthrust the ridge to the

  7. [Microphallus kurilensis sp. nov., a new species of microphallids from the pygmaeus species group (Trematoda, Microphallidae) from the coastal areas of Okhotsk and Bering Seas].

    PubMed

    Galaktionov, K V; Regel', K V; Atrashkevich, G I

    2010-01-01

    The pygmaeus-species group is composed of close related species from the genus Microphallus in which metacercariae develop inside daughter sporocysts without encystment. Infection of periwinkles Littorina (Neritremna) spp. with intramolluscan stages of a new species of this group (Microphallus kurilensis sp. nov.) was recorded on the coasts of Sakhalin and Kuril islands, north of the Sea of Okhotsk and Chukchi Peninsula (the Bering Sea). Application of molecular methods allowed us to establish that M. kurilensis metacercariae are conspecific with one of the morphotypes of microphallid adults obtained from the intestine of the Pacific common eider (Somateria mollissima v-nigrum), which was shot in the north of the Sea of Okhotsk (Galaktionov, Olson, and Blasco-Costa, in press). The adults of the same morphotype were recorded in the Pacific common eider from the northwestern part of the Bering Sea (Chukchi Peninsula). In the course of experimental infection of the slaty-backed gull Larus schistisagus chicks with metacercariae of M. kurilensis, few microphallid adults were obtained. These adults were identical in their morphology with specimens of the microphallid morphotype from the Pacific common eider, which had been identified as M. kurilensis based on molecular data. Morphological description of metacercaria and adult of M. kurilensis and list of their differences from the same developmental stages of other species from pygmaeus-group are provided. It is concluded that M. kurilensis is transmitted in the host system including periwinkle Littorina (Neritrema) and seaducks (predominately, Pacific common eider). Most probably, distribution of M. kurilensis is not limited by the north Asiatic coast but expanded to the North American coast of the Pacific Ocean.

  8. Fatty acid and stable isotope characteristics of sea ice and pelagic particulate organic matter in the Bering Sea: tools for estimating sea ice algal contribution to Arctic food web production.

    PubMed

    Wang, Shiway W; Budge, Suzanne M; Gradinger, Rolf R; Iken, Katrin; Wooller, Matthew J

    2014-03-01

    We determined fatty acid (FA) profiles and carbon stable isotopic composition of individual FAs (δ(13)CFA values) from sea ice particulate organic matter (i-POM) and pelagic POM (p-POM) in the Bering Sea during maximum ice extent, ice melt, and ice-free conditions in 2010. Based on FA biomarkers, differences in relative composition of diatoms, dinoflagellates, and bacteria were inferred for i-POM versus p-POM and for seasonal succession stages in p-POM. Proportions of diatom markers were higher in i-POM (16:4n-1, 6.6-8.7%; 20:5n-3, 19.6-25.9%) than in p-POM (16:4n-1, 1.2-4.0%; 20:5n-3, 5.5-14.0%). The dinoflagellate marker 22:6n-3/20:5n-3 was highest in p-POM. Bacterial FA concentration was higher in the bottom 1 cm of sea ice (14-245 μg L(-1)) than in the water column (0.6-1.7 μg L(-1)). Many i-POM δ(13)C(FA) values were higher (up to ~10‰) than those of p-POM, and i-POM δ(13)C(FA) values increased with day length. The higher i-POM δ(13)C(FA) values are most likely related to the reduced dissolved inorganic carbon (DIC) availability within the semi-closed sea ice brine channel system. Based on a modified Rayleigh equation, the fraction of sea ice DIC fixed in i-POM ranged from 12 to 73%, implying that carbon was not limiting for primary productivity in the sympagic habitat. These differences in FA composition and δ(13)C(FA) values between i-POM and p-POM will aid efforts to track the proportional contribution of sea ice algal carbon to higher trophic levels in the Bering Sea and likely other Arctic seas.

  9. Tectonics and petroleum potential of sedimentary basins in the Bering, Okhotsk, Japan seas, and island arcs

    SciTech Connect

    Levin, L.E. )

    1993-09-01

    In this vast region located in the northwestern part of the Pacific rim, basins of two main genetic types possess petroleum potential. These two types are represented by basins of the recent active margin and basins of the transitional zone between analogs of the passive margin and the recent active margin. For basins of the active margin, the mean density of potential resources is estimated at 5000 MT/km[sup 2] or more. The total area of these basins is 324,000 km[sup 2] among which 120,000 km[sup 2] are in the Russian sector. Ultimate resources of hydrocarbons are estimated at 1.62 billing MT of oil equivalent. Basins of the zone, transitional from analogs of the passive margin to the recent active margin, are characterized by a number of factors favorable for petroleum occurrence. One of the important factors is the presence of rift trough and foredeeps that are potential sites for zones of oil and gas accumulation. The age of the rifts varies from the late Cretaceous through the Oligocene-Miocene in the Olyutorsky and Litke basins, to the Neogene in the Okhotsk Sea and Tatar-Japan basins. Only a small area of the rifts has been proven to contain zones of oil and gas accumulation. Based on the structural characteristics, the rifts are subdivided into oil-gas bearing, potentially oil-gas bearing, and nonprospective for hydrocarbon exploration. Potential hydrocarbon resources of basins of this type are estimated to be not less than 15.12 billion MT of oil equivalent including 9.2 billion MT in the Russian sector. New large zones of oil and gas accumulation are expected to be found both on the shallow shelf and in some deep-water basins such as in the Aleutian and Kuril basins.

  10. Marine-entry timing and growth rates of juvenile Chum Salmon in Alaskan waters of the Chukchi and northern Bering seas

    NASA Astrophysics Data System (ADS)

    Vega, Stacy L.; Sutton, Trent M.; Murphy, James M.

    2017-01-01

    Climate change in the Arctic has implications for influences on juvenile Chum Salmon Oncorhynchus keta early life-history patterns, such as altered timing of marine entry and/or early marine growth. Sagittal otoliths were used to estimate marine entry dates and daily growth rates of juvenile Chum Salmon collected during surface trawl surveys in summers 2007, 2012, and 2013 in the Chukchi and northern Bering seas. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to discriminate between freshwater and marine sagittal growth on the otoliths, and daily growth increments were counted to determine marine-entry dates and growth rates to make temporal and regional comparisons of juvenile Chum Salmon characteristics. Marine-entry dates ranged from mid-June to mid-July, with all region and year combinations exhibiting similar characteristics in entry timing (i.e. larger individuals at the time of capture entered the marine environment earlier in the growing season than smaller individuals in the same region/year), as well as similar mean marine-entry dates. Juvenile Chum Salmon growth rates were on average 4.9% body weight per day in both regions in summers 2007 and 2012, and significantly higher (6.8% body weight per day) in the Chukchi Sea in 2013. These results suggest that juvenile Chum Salmon in the northern Bering and Chukchi seas currently exhibit consistent marine-entry timing and early marine growth rates, despite some differences in environmental conditions between regions and among years. This study also provides a baseline of early marine life-history characteristics of Chum Salmon for comparisons with future climate change studies in these regions.

  11. Controls on the distribution of deep-sea sediments

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, A.; O'Callaghan, S.; Müller, R. D.

    2016-08-01

    Deep-sea sediments represent the largest geological deposit on Earth and provide a record of our planet's response to conditions at the sea surface from where the bulk of material originates. We use a machine learning method to analyze how the distribution of 14,400 deep-sea sediment sample lithologies is connected to bathymetry and surface oceanographic parameters. Our probabilistic Gaussian process classifier shows that the geographic occurrence of five major lithologies in the world's ocean can be predicted using just three parameters. Sea-surface salinity and temperature provide a major control for the growth and composition of plankton and specific ranges are also associated with the influx of non-aerosol terrigenous material into the ocean, while bathymetry is an important parameter for discriminating the occurrence of calcareous sediment, clay and coarse lithogenous sediment from each other. We find that calcareous and siliceous oozes are not linked to high surface productivity. Diatom and radiolarian oozes are associated with low salinities at the surface but with discrete ranges of temperatures, reflecting the diversity of planktonic species in different climatic zones. Biosiliceous sediments cannot be used to infer paleodepth, but are good indicators of paleotemperature and paleosalinity. Our analysis provides a new framework for constraining paleosurface ocean environments from the geological record of deep-sea sediments. It shows that small shifts in salinity and temperature significantly affect the lithology of seafloor sediment. As deep-sea sediments represent the largest carbon sink on Earth these shifts need to be considered in the context of global ocean warming.

  12. Characterization of plutonium in deep-sea sediments of the Sulu and South China Seas.

    PubMed

    Dong, Wei; Zheng, Jian; Guo, Qiuju; Yamada, Masatoshi; Pan, Shaoming

    2010-08-01

    Anthropogenic Pu isotopes are important geochemical tracers for sediment studies. Their distributions and sources in the water columns as well as the sediments of the North Pacific have been intensively studied; however, information about Pu in the Southeast Asian seas is limited. To study the isotopic composition of Pu, and thus to identify its sources, we collected sediment core samples in the South China Sea and the Sulu Sea during the KH-96-5 Cruise of the R/V Hakuho Maru. We analysed the activities of (239+240)Pu and the atom ratios of (240)Pu/(239)Pu using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS). The (240)Pu/(239)Pu atom ratios in the sediments of both areas (inventory weighted mean: 0.251 for the South China Sea and 0.280 for the Sulu Sea) were higher than the global fallout value (0.178+/-0.019), suggesting the existence of Pu from the Pacific Proving Grounds in the North Pacific. Low inventories of (239+240)Pu in sediments were observed in the South China Sea (3.75 Bq/m(2)) and the Sulu Sea (1.38 Bq/m(2)). Most of the Pu input is still present in the water column. Scavenging and benthic mixing processes were considered to be the main processes controlling the distribution of Pu in the deep-sea sediments of both study areas.

  13. Organic carbon burial rates in the Baltic Sea sediments

    NASA Astrophysics Data System (ADS)

    Winogradow, A.; Pempkowiak, J.

    2014-02-01

    Recent studies indicate the important role of the marine environment in the circulation of CO2. This is due to the occurrence of the so called "biological pump" mechanism. A special role in this process is played by the shelf seas. The paper presents estimates of organic carbon burial rates in the Baltic Sea sediments. Quantification of the burial rate required the determination of organic carbon accumulation rate to the Baltic sediments and the carbon return flux from sediments to the water column. Results of both sediment and mass accumulation rates as well as profiles of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) were used. Sediment accumulation rates were based on 210Pb method validated by 137Cs measurements and ranged from 66 g m-2 yr-1 to 744 g m-2 yr-1 as regards mass accumulation rates and from 0.07 cm yr-1 to 0.25 cm yr-1 as regards linear accumulation rates. Carbon deposition to the Baltic sediments amounts to 1.955 ± 0.585 Tg m-2 yr-1, while 0.759 ± 0.020 g m-2 yr-1 of carbon returns from sediments to the water column. Thus the organic carbon burial rate in the Baltic Sea sediments is equal to 1.197 ± 0.584 Tg C m-2 yr-1.

  14. Gravitational failure of sea cliffs in weakly lithified sediment

    USGS Publications Warehouse

    Hampton, M.A.

    2002-01-01

    Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.

  15. The relationship between sea ice concentration and the spatio-temporal distribution of vocalizing bearded seals (Erignathus barbatus) in the Bering, Chukchi, and Beaufort Seas from 2008 to 2011

    NASA Astrophysics Data System (ADS)

    MacIntyre, Kalyn Q.; Stafford, Kathleen M.; Conn, Paul B.; Laidre, Kristin L.; Boveng, Peter L.

    2015-08-01

    Bearded seals (Erignathus barbatus) are widely distributed in the Arctic and sub-Arctic; the Beringia population is found throughout the Bering, Chukchi and Beaufort Seas (BCB). Bearded seals are highly vocal, using underwater calls to advertise their breeding condition and maintain aquatic territories. They are also closely associated with pack ice for reproductive activities, molting, and resting. Sea ice habitat for this species varies spatially and temporally throughout the year due to differences in underlying physical and oceanographic features across its range. To test the hypothesis that the vocal activity of bearded seals is related to variations in sea ice, passive acoustic data were collected from nine locations throughout the BCB from 2008 to 2011. Recording instruments sampled on varying duty cycles ranging from 20% to 100% of each hour, and recorded frequencies up to 8192 Hz. Spectrograms of acoustic data were analyzed manually to calculate the daily proportion of hours with bearded seal calls at each sampling location, and these call activity proportions were correlated with daily satellite-derived estimates of sea ice concentration. Bearded seals were vocally active nearly year-round in the Beaufort and Chukchi Seas with peak activity occurring from mid-March to late June during the mating season. The duration of call activity in the Bering Sea was shorter, lasting typically only five months, and peaked from mid-March to May at the northernmost recorders. In all areas, call activity was significantly correlated with higher sea ice concentrations (p < 0.01). These results suggest that losses in ice cover may negatively impact bearded seals, not just by loss of habitat but also by altering the behavioral ecology of the BCB population.

  16. Paleoproductivity and paleoceanography of the last 4.3 Myrs at IODP Exp. 323 Site U1341 in the Bering Sea based on biogenic opal content

    NASA Astrophysics Data System (ADS)

    Iwasaki, S.; Takahashi, K.; Kanematsu, Y.; Sakamoto, T.; Sakai, S.; Onodera, J.; Asahi, H.; Ravelo, A. C.; Science Team of IODP Exp. 323.

    2011-12-01

    The Bering Sea is known as a North Pacific marginal sea with a high biological productivity with its key location between the Pacific Ocean and the Arctic Ocean for the surface water circulation. Because that biogenic opal productivity is influenced by surface water structure, water circulation and sea ice cover, such conditions can be reconstructed by measuring biogenic opal content. Previous knowledge from the region including the vicinity indicates that biogenic opal productivity is generally high during interglacials and low during glacials (Narita et al., 2002; Okazaki et al., 2005; Iwasaki et al., in press). During the IODP Expedition 323, seven sites were drilled in the Bering Sea. Among them, Site U1341 was drilled to approximately 600 mbsf with a more or less complete record of the last 4.3 Myrs. The objectives of our study are to: (1) reconstruct the paleoproductivity change; and (2) compare the productivity change with that of other regions. Based on the analysis of over 1,400 samples, several notable trends are observed. First, the overall change is decreasing in biogenic opal content (from ~60% to 10-35%) during the last 4.3 Myrs. During the warm Pliocene without sea-ice diatoms the convection was sufficient to keep up high nutrient concentrations in the surface layers, also seen in the ship board data of "heavily silicified diatoms" (Takahashi et al., 2011). On the other hand, during the late Pleistocene, for example, overall biogenic opal values are low while substantial fluctuations (10-65%) due to change in climate are seen. Sufficient sea-ice cover, with sea-ice diatoms and dinoflagellates in ship board data (Takahashi et al., 2011), during the cold intervals of the Milakovitch cycles is responsible for the notably low values. The changes from warm to cold intervals are matched up generally well with other available ship board data: natural ganmma ray radiation, bulk density, & color reflectance (b*). Furthermore, the amplitudes of biogenic opal

  17. Aerial Surveys of Endangered Whales in the Northern Bering, Eastern Chukchi, and Alaskan Beaufort Seas, 1985: With a Seven Year Review, 1979-85.

    DTIC Science & Technology

    1986-08-01

    8217 . " - • " " " ’ " ’"" . - - - " "" "° " " "" " " , , - " UUSS USSRA as LEGENDJ 0GV S CAPE PRINCE OF WALES % .4(DO crnM BERING SEA OCG 00 M 0a hI)rO 0 0 0 1 Kp 000...o,,o_.._ .- Demarcation Pt Cape Lisbuneo 680I , ialn 680: 660 USSR16 100 15 1 apatocni Prince of Wales AndSK i nest coe s dNo o i 64...and migration patterns of the white whale ( Beluga ), Delphinapterus leucas. Rep. int. Whal. Commn. vol. 30:465-480. 1980. Herzing, D.L. and B.R. Mate

  18. Spatial and geographical changes in the mesozooplankton community in the Bering and Chukchi Seas during the summers of 2007 and 2008

    NASA Astrophysics Data System (ADS)

    Matsuno, Kohei; Landeira Sanchez, Jose M.; Yamaguchi, Atsushi; Hirawake, Toru; Kikuchi, Takashi

    2016-09-01

    From July to August 2007 and June to July 2008, the horizontal/geographical changes in the zooplankton community in the Bering and Chukchi Seas were studied. The geographical patterns, which were common for these two years, were observed for salinity, chlorophyll a (Chl. a), zooplankton chaetognaths, hydrozoans and the whole zooplankton community. Among them, the patterns of salinity and Chl. a were related with the horizontal distribution of the water masses. The distributions of the two carnivorous taxa were correlated with their prey (copepods or barnacle larvae). The analysis of the structural equation model (SEM) revealed that the horizontal distribution of the zooplankton abundance and biomass were governed by the different taxa. Thus, the zooplankton abundance was governed by the numerically dominant but smaller-bodied taxa, such as the barnacle larvae and copepod Pseudocalanus spp., while the zooplankton biomass was determined by the large-bodied copepods, such as Calanus glacialis/marshallae and Eucalanus bungii.

  19. Aerial surveys of endangered cetaceans and other marine mammals in the northwestern Gulf of Alaska and southeastern Bering Sea. Final report

    SciTech Connect

    Brueggeman, J.J.; Green, G.A.; Grotefendt, R.A.; Chapman, D.G.

    1987-09-01

    Aerial surveys were conducted in the Northwestern Gulf of Alaska and southeastern Bering Sea to determine the abundance, distribution, and habitat use patterns of endangered cetaceans and other marine mammals. Four species of cetaceans listed by the Federal Government as endangered were observed: gray, humpback, finback, and sperm whales. Sightings were also made to seven nonendangered species of cetaceans: minke, Cuvier's beaked, Baird's beaked, belukha, and killer whales, and Dall and harbor porpoises. Results show that the project area is an important feeding ground for relatively large numbers of humpback and finback whales and lower numbers of gray whale migration route between seasonal ranges. The project area also supports a variety of other marine mammals both seasonally and annually.

  20. A time-series study of the spring bloom at the Bering Sea ice edge I. Physical processes, chlorophyll and nutrient chemistry

    NASA Astrophysics Data System (ADS)

    Niebauer, H. J.; Alexander, Vera; Henrichs, Susan M.

    1995-12-01

    An intense but short-lived phytoplankton bloom develops in the low-salinity melt waters at the edge of the Bering Sea ice as the ice melts and retreats each spring. In spring 1988 we followed the development of this bloom by sampling every 3 h while following a freely drifting drogue in the marginal ice-edge zone for two four-day periods. The first period (29 April-3 May) was at an early stage of the bloom while the second period (10-13 May) was at the peak of the bloom. Early in the bloom, the phytoplankton consumed all the nitrate (˜400 mmoles m -2) initially present in the surface water producing large accumulations of particulate carbon (>1000 mmoles C m -2). By the time of peak chlorophyll concentrations (˜35 mg M -3), nitrate concentrations had been depleted so that the sustained high productivity depended on either recycled or imported nutrients. After this point, there was little net additional accumulation of biomass. From these data plus cruise data from previous years, we find that the Bering Sea ice-edge bloom typically begins in the last week of April and appears to precede blooms in the adjacent ice-free waters by days to weeks. The variability in bloom onset observed over several years is not linked very closely to the large scale climatic variations found in this region, but rather appears to be related to local weather during the end of April and the first part of May, with calm, sunny weather being required to initiate the blooms.

  1. A cross-shelf gradient in δ15N stable isotope values of krill and pollock indicates seabird foraging patterns in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Jones, Nathan M.; Hoover, Brian A.; Heppell, Scott A.; Kuletz, Kathy J.

    2014-11-01

    Concurrent measurements of predator and prey δ15N isotope values demonstrated that a cross-shelf isotopic gradient can propagate through a marine food web from forage species to top-tier predators and indicate foraging areas at a scale of tens of kilometers. We measured δ13C and δ15N in muscle tissues of thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla), and in whole body tissues of walleye pollock (Gadus chalcogrammus) and krill (Thysanoessa spp), sampled across the continental shelf break in the Bering Sea in 2008 and in 2009. We found significant basin-shelf differences at fine scales (<100 km) in δ15N among murres but not kittiwakes, and no such differences in δ13C in either seabird species at that scale. We then quantified the multi-trophic signal and spatial structure of a basin-shelf δ15Nitrogen gradient in the central and southern Bering Sea, and used it to contrast foraging patterns of thick-billed murres and kittiwakes on the open ocean. Seabird muscle δ15N values were compared to baselines created from measurements in krill and pollock tissues sampled concurrently throughout the study area. Krill, pollock, and murre tissues from northern, shallow, shelf habitat (<200 m) were enriched 1-2‰ in δ15N relative to samples taken from deeper habitats (>200 m) to the south and west. Krill δ15N baseline values predicted 35-42% of the variability in murre tissue values. Patterns between kittiwakes and prey were less coherent. The persistence of strong spatial autocorrelation among sample values, and a congruence of geospatial patterns in δ15N among murre and prey tissues, suggest that murres forage repeatedly in specific areas. Murre isotope values showed distinct geospatial stratification, coincident with the spatial distribution of three colonies: St. Paul, St. George, and Bogoslof. This suggests some degree of foraging habitat partitioning among colonies.

  2. Modeling connectivity of walleye pollock in the Gulf of Alaska: Are there any linkages to the Bering Sea and Aleutian Islands?

    NASA Astrophysics Data System (ADS)

    Parada, Carolina; Hinckley, Sarah; Horne, John; Mazur, Michael; Hermann, Albert; Curchister, Enrique

    2016-10-01

    We investigated the connectivity of walleye pollock in the Gulf of Alaska (GOA) and linkages to the Bering Sea (BS) and Aleutian Island (AL) regions. We used a spatially-explicit Individual-based model (IBM) coupled to 6 years of a hydrodynamic model that simulates the early life history of walleye pollock in the GOA (eggs to age-0 juveniles). The processes modeled included growth, movement, mortality, feeding and the bioenergetics component for larvae and juveniles. Simulations were set to release particles on the 1st of the month (February to May) in fourteen historical spawning areas in the GOA up to the 1st of September each year. Model results reproduced the link between the Shelikof Strait spawning area and the Shumagin nursery region for March and April spawners, besides other Potential Nursery Areas (PNAs) found in the GOA. A prominent finding of this study was the appearance of the BS as important PNAs for several GOA spawning grounds, which is supported by a consistent flow into the BS through Unimak Pass. The simulations showed the highest density of simulated surviving pollock in the western Bering Sea (WBS) region with the lowest coefficients of variation of the whole domain. Three spawning sectors were defined, which aggregate multiple spawning areas in the eastern (EGOA), central (CGOA) and western Gulf of Alaska (WGOA). A connectivity matrix showed strong retention within the CGOA (25.9%) and EGOA (23.8%), but not in the WGOA (7.2%). Within the GOA, the highest connectivity is observed from EGOA to CGOA (57.8%) followed by the connection from CGOA to WGOA (24.3%). Overall, one of the most prominent connections was from WGOA to WBS (62.8%), followed by a connection from CGOA to WBS (29.2%). In addition, scenarios of shifting spawning locations and nursery sectors of GOA, BS and AL are explored and implications for walleye pollock stock structure hypotheses are discussed.

  3. Modelling of contemporary sedimentation in the Azov Sea

    NASA Astrophysics Data System (ADS)

    Sorokina, V.; Berdnikov, S.; Venevsky, S.

    2009-04-01

    Contemporary sedimentation in the Azov Sea was estimated spatially detailed mathematical model for transport and sedimentation of the particulate matter. The model TRASEAS includes dynamic of suspended and eposited terrigenous matter in water column and at the bottom and accounts for realistic bathymetry. Distinct spatiotemporal features of the terrigenous sedimentation in the second half of the 20th century were recognized. The decrease in the accumulation of terrigenous sediments and diminishing in the areas with a negative balance of the terrigenous matter was found. This was related to the 2.5-fold fall in the volumes of the matter supplied from land. In general, during the second half of the 20thcentury the rate of sedimentation decreased from 1000 to 400 g/m2/year with spatial variation. In the central part of the sea, which is relatively far from source of terrigenous matter, the rate of sedimentation has value of about 300 g/m2/year. In Taganrog Bay and in the inner sea , areas with a negative balance of terrigenous sedimentation increased up to 30%.

  4. Deep-sea methane seep sediments in the Okhotsk Sea sustain diverse and abundant anammox bacteria.

    PubMed

    Shao, Sudong; Luan, Xiwu; Dang, Hongyue; Zhou, Haixia; Zhao, Yakun; Liu, Haitao; Zhang, Yunbo; Dai, Lingqing; Ye, Ying; Klotz, Martin G

    2014-02-01

    Marginal sea methane seep sediments sustain highly productive chemosynthetic ecosystems and are hotspots of intense biogeochemical cycling. Rich methane supply stimulates rapid microbial consumption of oxygen; these systems are thus usually hypoxic to anoxic. This and reported evidence for resident nitrogen fixation suggest the presence of an anaerobic ammonium-oxidizing (anammox) bacterial community in methane seep sediments. To test this hypothesis, we employed detection of genes encoding 16S rRNA gene and hydrazine dehydrogenase (hzo) to investigate the structure, abundance and distribution of the anammox bacterial community in the methane seep sediments of the Okhotsk Sea. Diverse complements of Candidatus Scalindua-related 16S rRNA and hzo gene sequences were obtained. Most of the deep-sea sites harbored abundant hzo genes with copy numbers as high as 10(7)  g(-1) sediment. In general, anammox bacterial signatures were significantly more abundant in the deep-water sediments. Sediment porewater NO3-, NOx- (i.e. NO3- + NO2-), NOx-/NH4+ and sediment silt content correlated with in situ distribution patterns of anammox bacterial marker genes, likely because they determine anammox substrate availability and sediment geochemistry, respectively. The abundance and distribution of anammox bacterial gene markers indicate a potentially significant contribution of anammox bacteria to the marine N cycle in the deep-sea methane seep sediments.

  5. Polycyclic aromatic hydrocarbons in sediments of China Sea.

    PubMed

    Li, Yanxia; Duan, Xiaoyong

    2015-10-01

    Increasing pollution pressures were placed in the coastal and estuarine ecosystems in China because of the elevated pollutants discharged from various sources. Polycyclic aromatic hydrocarbons (PAHs) in the environment were closely linked to human activities, which have been intensively studied for their geochemical interest as markers. In this review, the status of PAH contamination in China Sea was assessed by comprehensive reviews of the concentrations, sources, and fates of PAHs in sediments of China Sea. PAH concentrations in China Sea sediments decreased from north to south due to the higher emissions in North China. Atmosphere was probably the main carrier of PAHs in the north due to the higher contents of atmospheric fine particles and higher wind speeds. However, riverine inputs were probably the most important sources of PAHs in the coastal sediments of South China due to higher rainfall.

  6. Presence of oxygen and aerobic communities from sea floor to basement in deep-sea sediments

    NASA Astrophysics Data System (ADS)

    D'Hondt, Steven; Inagaki, Fumio; Zarikian, Carlos Alvarez; Abrams, Lewis J.; Dubois, Nathalie; Engelhardt, Tim; Evans, Helen; Ferdelman, Timothy; Gribsholt, Britta; Harris, Robert N.; Hoppie, Bryce W.; Hyun, Jung-Ho; Kallmeyer, Jens; Kim, Jinwook; Lynch, Jill E.; McKinley, Claire C.; Mitsunobu, Satoshi; Morono, Yuki; Murray, Richard W.; Pockalny, Robert; Sauvage, Justine; Shimono, Takaya; Shiraishi, Fumito; Smith, David C.; Smith-Duque, Christopher E.; Spivack, Arthur J.; Steinsbu, Bjorn Olav; Suzuki, Yohey; Szpak, Michal; Toffin, Laurent; Uramoto, Goichiro; Yamaguchi, Yasuhiko T.; Zhang, Guo-Liang; Zhang, Xiao-Hua; Ziebis, Wiebke

    2015-04-01

    The depth of oxygen penetration into marine sediments differs considerably from one region to another. In areas with high rates of microbial respiration, O2 penetrates only millimetres to centimetres into the sediments, but active anaerobic microbial communities are present in sediments hundreds of metres or more below the sea floor. In areas with low sedimentary respiration, O2 penetrates much deeper but the depth to which microbial communities persist was previously unknown. The sediments underlying the South Pacific Gyre exhibit extremely low areal rates of respiration. Here we show that, in this region, microbial cells and aerobic respiration persist through the entire sediment sequence to depths of at least 75 metres below sea floor. Based on the Redfield stoichiometry of dissolved O2 and nitrate, we suggest that net aerobic respiration in these sediments is coupled to oxidation of marine organic matter. We identify a relationship of O2 penetration depth to sedimentation rate and sediment thickness. Extrapolating this relationship, we suggest that oxygen and aerobic communities may occur throughout the entire sediment sequence in 15-44% of the Pacific and 9-37% of the global sea floor. Subduction of the sediment and basalt from these regions is a source of oxidized material to the mantle.

  7. Mangrove sedimentation and response to relative sea-level rise

    USGS Publications Warehouse

    Woodroffe, CD; Rogers, K.; Mckee, Karen L.; Lovelock, CE; Mendelssohn, IA; Saintilan, N.

    2016-01-01

    Mangroves occur on upper intertidal shorelines in the tropics and subtropics. Complex hydrodynamic and salinity conditions influence mangrove distributions, primarily related to elevation and hydroperiod; this review considers how these adjust through time. Accumulation rates of allochthonous and autochthonous sediment, both inorganic and organic, vary between and within different settings. Abundant terrigenous sediment can form dynamic mudbanks; tides redistribute sediment, contrasting with mangrove peat in sediment-starved carbonate settings. Sediments underlying mangroves sequester carbon, but also contain paleoenvironmental records of adjustments to past sea-level changes. Radiometric dating indicates long-term sedimentation, whereas Surface Elevation Table-Marker Horizon measurements (SET-MH) provide shorter perspectives, indicating shallow subsurface processes of root growth and substrate autocompaction. Many tropical deltas also experience deep subsidence, which augments relative sea-level rise. The persistence of mangroves implies an ability to cope with moderately high rates of relative sea-level rise. However, many human pressures threaten mangroves, resulting in continuing decline in their extent throughout the tropics.

  8. Mangrove Sedimentation and Response to Relative Sea-Level Rise.

    PubMed

    Woodroffe, C D; Rogers, K; McKee, K L; Lovelock, C E; Mendelssohn, I A; Saintilan, N

    2016-01-01

    Mangroves occur on upper intertidal shorelines in the tropics and subtropics. Complex hydrodynamic and salinity conditions, related primarily to elevation and hydroperiod, influence mangrove distributions; this review considers how these distributions change over time. Accumulation rates of allochthonous and autochthonous sediment, both inorganic and organic, vary between and within different settings. Abundant terrigenous sediment can form dynamic mudbanks, and tides redistribute sediment, contrasting with mangrove peat in sediment-starved carbonate settings. Sediments underlying mangroves sequester carbon but also contain paleoenvironmental records of adjustments to past sea-level changes. Radiometric dating indicates long-term sedimentation, whereas measurements made using surface elevation tables and marker horizons provide shorter perspectives, indicating shallow subsurface processes of root growth and substrate autocompaction. Many tropical deltas also experience deep subsidence, which augments relative sea-level rise. The persistence of mangroves implies an ability to cope with moderately high rates of relative sea-level rise. However, many human pressures threaten mangroves, resulting in a continuing decline in their extent throughout the tropics.

  9. Mangrove Sedimentation and Response to Relative Sea-Level Rise

    NASA Astrophysics Data System (ADS)

    Woodroffe, C. D.; Rogers, K.; McKee, K. L.; Lovelock, C. E.; Mendelssohn, I. A.; Saintilan, N.

    2016-01-01

    Mangroves occur on upper intertidal shorelines in the tropics and subtropics. Complex hydrodynamic and salinity conditions, related primarily to elevation and hydroperiod, influence mangrove distributions; this review considers how these distributions change over time. Accumulation rates of allochthonous and autochthonous sediment, both inorganic and organic, vary between and within different settings. Abundant terrigenous sediment can form dynamic mudbanks, and tides redistribute sediment, contrasting with mangrove peat in sediment-starved carbonate settings. Sediments underlying mangroves sequester carbon but also contain paleoenvironmental records of adjustments to past sea-level changes. Radiometric dating indicates long-term sedimentation, whereas measurements made using surface elevation tables and marker horizons provide shorter perspectives, indicating shallow subsurface processes of root growth and substrate autocompaction. Many tropical deltas also experience deep subsidence, which augments relative sea-level rise. The persistence of mangroves implies an ability to cope with moderately high rates of relative sea-level rise. However, many human pressures threaten mangroves, resulting in a continuing decline in their extent throughout the tropics. *

  10. Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Kokubun, N.; Kikuchi, D. M.; Sato, N.; Takahashi, A.; Will, A.; Kitaysky, A. S.; Watanuki, Y.

    2015-11-01

    Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to the inter-annual change in environmental conditions. Between the study years, winter ice retreated earlier and summer water temperatures were warmer in 2014 compared to those in 2013. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf, but showed a relatively higher use of the shelf break and oceanic basin in the colder year, 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and, bimodally, at 150-250 and 300-350 km in 2014 for RLKI, and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between years in RLKI, but differed in TBMU, showing higher levels of physiological stress incurred by murres during the colder year, 2013. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU, while δ13C (a proxy of prey origin) were lower in 2014 than in 2013 in both species, suggesting possible differences in influx of oceanic prey items into foraging areas. These results suggest that the response of ecosystem dynamics to climate variability in the southeast Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those

  11. Sulfate reduction in deep-sea sediments

    NASA Technical Reports Server (NTRS)

    Canfield, D. E.

    1991-01-01

    Sulfate reduction rates calculated from about 200 DSDP pore water sulfate profiles have been contoured and plotted on a map covering most areas of the world ocean. Rates show a remarkable spatial consistency, with high rates observed near the continental margins, becoming progressively lower toward the central ocean basins. Relatively elevated rates are also found in the eastern equatorial Pacific, a site of upwelling and correspondingly high rates of primary organic production. Overall, the distribution of sulfate reduction in pelagic sediments looks very similar to the distribution of primary organic carbon production. When rates are directly compared, however, the correlation between sulfate reduction and primary production is only moderately strong. Perhaps the most important influence on sulfate reduction is sediment deposition rate and the control this has over the fraction of the sedimentary organic carbon flux that becomes available for sulfate reduction. The slower the rate of sediment deposition the more time for oxic respiration and the less organic carbon that escapes to the zone of sulfate reduction. To predict most accurately sulfate reduction rates, however, the variables of primary production, water depth, and sediment deposition rate must all be integrated.

  12. Novel pyropheophorbide steryl esters in Black Sea sediments

    SciTech Connect

    King, L.L.; Repeta, D.J. )

    1991-07-01

    A series of non-polar chlorophyll degradation products (NPCs) with greater than 10 components has been isolated from Black Sea sediment and identified as pyropheophorbide steryl esters by visible and mass spectrometry. These compounds have been previously observed in seawater and sediment trap samples, and may be formed during grazing of phytoplankton by zooplanktonic herbivores. In Black Sea sediments, NPCs constitute 14% of the total phorbins determined spectroscopically at 660 nm, and 39% of the total chlorophyll degradation products measured by high pressure liquid chromatography. NPCs therefore constitute a significant sedimentary sink for chlorophyll. The distribution of sterols released by hydrolysis of NPCs most closely resembles sterols in suspended particulate matter collected from the euphotic zone and is quite different from the distribution of solvent-extractable sterols in sediments. Sterols extracted from sediemtns have high concentrations of 4-methylsterols and high stanol/stenol ratios. BNPC-derived sterols have very low concentrations of 4-methylsterols and low stanol/stenol ratios. The authors suggest that these differences reflect an enhanced preservation of HPCs in sediments relative to free sterols and phorbins. As a result, the original production of sterols in the euphotic zone may be more closely approximated by the distribution of NPC-derived sterols than by the distribution of free sterols in sediments.

  13. Synthetic stratigraphy of epicontinental seas: a carbonate sedimentation model and its applications in sea level studies

    SciTech Connect

    Cisne, J.L.; Gildner, R.F.

    1984-04-01

    Carbonates from the central parts of epicontinental seas are ideal strata for detailed study of eustatic sea level change. On the basis of sedimentation model in which carbonate accumulation rate is directly proportional to water depth, we developed synthetic stratigraphies for sea level histories expected for post-glacial transgression and for constant and sinusoidally fluctuating ocean ridge volume increase. These histories give distinctly different trends for water depth as a function of stratigraphic position in the sections' bathymetric curves. In general, water depth is proportional to the rate of sea level rise. Depth-dependent sedimentation leads to a time lag between sea level fluctuation and corresponding depth fluctuation which, as examples show, can approach 10/sup 6/ years for depth fluctuations of even a few meters--a fundamental consideration for reconstructing sea level curves, time-correlating sections by bathymetric curves, and relating water depth on continents to ocean ridge volume. Bathymetric curves based on gradient analysis of fossil assemblages (coenocorrelation curves) for American Middle Ordovician sections approximate patterns expected for sinusoidally increasing sea level. The model's predictions are tested in an ''artificial experiment'' that takes advantage of differential subsidence between the craton's middle and its edge to make a difference in the bathymetric histories of sections that otherwise record the same sea level history. The depth dependence in sedimentation was that above wave base net accumulation per year was very roughly 3 x 10/sup -6/ of the water depth.

  14. Methane in coastal sea water, sea ice, and bottom sediments, Beaufort Sea, Alaska

    USGS Publications Warehouse

    Lorenson, T.D.; Kvenvolden, Keith A.

    1995-01-01

    This report summarizes data acquired from 1990 to 1994 for the gas-hydrate portion of the USGS project 'Permafrost and gas hydrate as possible sources of methane' of the USGS Global Change and Climate History program. The objective of this project has been to test the hypothesis that gas hydrate deposits of the Beaufort Sea continental shelf are destabilized by the ~10?C temperature increase that has resulted from the Holocene transgression of the Arctic Ocean. To test this idea we have selected an area off the north coast of Alaska centered on Harrison Bay. We have measured the concentration of methane in surficial sediments, in the water column when ice is present and absent, and in seasonal sea ice. Our results show that more methane is present in the water when ice is present than when ice is absent, and that methane is also present within the ice itself, often at higher concentrations than in the water. Thus the Beaufort Sea shelf of Alaska is a seasonal source of methane. The primary source of this methane has not yet been defined, but gas hydrate is a reasonable candidate.

  15. Chemical composition of sediments from White Sea, Russian Arctic

    NASA Astrophysics Data System (ADS)

    Gamza, Olga; Shevchenko, Vladimir; Novigatsky, Aleksandr

    2010-05-01

    The White Sea, the only Russian inland sea, is located on the north of outlying districts of the European part of Russia, belongs to Arctic Ocean. Area of water of sea occupies about 90 tousend square kilometers. The sea can be divided into some general parts: neck, funnel, basin and 4 Bays: Dvina Bay, Kandalaksha Bay, Mezen Bay and Onega Bay. The purpose of this work was geochemical mapping of the surface sediments of this area. The main tasks were: compilation data base of element composition of the surface sediments, geochemical mapping of each element, research of the anormal concentration of elements on the surface. To detect the content of chemical elements several methods were used: atomic absorption spectrometry (P.P. Shirshov Institute of Oceanology); neutron activation analysis (Vernadsky Institute of Geochemistry and Analytical Chemistry), total and organic carbon analysis, photometric method to detection Si, Al, P (P.P. Shirshov Institute of Oceanology). Bulk composition is one of the fundamental characteristics of sediments and bottom deposites of modern basins. Coarse-grained sediments with portion of pelitic component <50% is spread on the shallow area (Kandalaksha Bay), in areas with high hydrodynamic activity of near-bottom water. Under the conditions of their low activity, fine-grained facies are common(>80%). Character of elements distribution correlates with facial distribution of sediments from White Sea. According to litologic description, bottom surface of Dvina Bay is practically everywhere covered by layer of fine-grained sand. In the border area between Dvina Bay and White Sea basin on terraced subwater slope aleurite politic silts are abundant. They tend to exhange down the slope to clay silts. In Onega Bay fractions of non-deposition are observed. They are characterized by wide spread of thin blanket poorgraded sediments, which are likely to be relic. Relief of Kandalakscha Bay bottom is presented as alternation of abyssal fosses (near

  16. Sediment dynamics in the Adriatic Sea investigated with coupled models

    USGS Publications Warehouse

    Sherwood, Christopher R.; Book, Jeffrey W.; Carniel, Sandro; Cavaleri, Luigi; Chiggiato, Jacopo; Das, Himangshu; Doyle, James D.; Harris, Courtney K.; Niedoroda, Alan W.; Perkins, Henry; Poulain, Pierre-Marie; Pullen, Julie; Reed, Christopher W.; Russo, Aniello; Sclavo, Mauro; Signell, Richard P.; Traykovski, Peter A.; Warner, John C.

    2004-01-01

    Several large research programs focused on the Adriatic Sea in winter 2002-2003, making it an exciting place for sediment dynamics modelers (Figure 1). Investigations of atmospheric forcing and oceanic response (including wave generation and propagation, water-mass formation, stratification, and circulation), suspended material, bottom boundary layer dynamics, bottom sediment, and small-scale stratigraphy were performed by European and North American researchers participating in several projects. The goal of EuroSTRATAFORM researchers is to improve our ability to understand and simulate the physical processes that deliver sediment to the marine environment and generate stratigraphic signatures. Scientists involved in the Po and Apennine Sediment Transport and Accumulation (PASTA) experiment benefited from other major research programs including ACE (Adriatic Circulation Experiment), DOLCE VITA (Dynamics of Localized Currents and Eddy Variability in the Adriatic), EACE (the Croatian East Adriatic Circulation Experiment project), WISE (West Istria Experiment), and ADRICOSM (Italian nowcasting and forecasting) studies.

  17. Cetacean distribution and abundance in relation to oceanographic domains on the eastern Bering Sea shelf, June and July of 2002, 2008, and 2010

    NASA Astrophysics Data System (ADS)

    Friday, Nancy A.; Zerbini, Alexandre N.; Waite, Janice M.; Moore, Sue E.; Clapham, Phillip J.

    2013-10-01

    As part of the Bering Sea Project, cetacean surveys were conducted to describe distribution and estimate abundance on the eastern Bering Sea shelf. Three marine mammal observers conducted visual surveys along transect lines sampled during the Alaska Fisheries Science Center walleye pollock assessment survey in June and July of 2008 and 2010. Distribution and abundance in 2008 and 2010 (cold years) are compared with results from a similar survey conducted in 2002 (a warm year), as the only three years that the entire survey area was sampled; patterns largely match those previously observed. Abundance estimates for comparable areas in 2002, 2008 and 2010 were as follows: humpback whales (Megaptera novaeangliae): 231 (CV=0.63), 436 (CV=0.45), and 675 (CV=0.80); fin whales (Balaenoptera physalus): 419 (CV=0.33), 1368 (CV=0.34), and 1061 (CV=0.38); minke whales (Balaenoptera acutorostrata): 389 (CV=0.52), 517 (CV=0.69), and 2020 (CV=0.73); Dall's porpoise (Phocoenoides dalli): 35,303 (CV=0.53), 14,543 (CV=0.32), and 11,143 (CV=0.32); and harbor porpoise (Phocoena phocoena): 1971 (CV=0.46), 4056 (CV=0.40), and 833 (CV=0.66). It should be noted that these abundance estimates are not corrected for biases due to perception, availability, or responsive movement. Estimates for humpback, fin and minke whales increased from 2002 to 2010, while those for harbor and Dall's porpoise decreased; trends were significant for fin whales. It is likely that changes in estimated abundance are due at least in part to shifts in distribution and not just changes in overall population size. Annual abundance estimates were examined by oceanographic domain. Humpback whales were consistently concentrated in coastal waters north of Unimak Pass. Fin whales were broadly distributed in the outer domain and slope in 2008 and 2010, but sightings were sparse in 2002. Minke whales were distributed throughout the study area in 2002 and 2008, but in 2010 they were concentrated in the outer domain and

  18. Microbial community composition and diversity in Caspian Sea sediments

    PubMed Central

    Mahmoudi, Nagissa; Robeson, Michael S.; Castro, Hector F.; Fortney, Julian L.; Techtmann, Stephen M.; Joyner, Dominique C.; Paradis, Charles J.; Pfiffner, Susan M.; Hazen, Terry C.

    2014-01-01

    The Caspian Sea is heavily polluted due to industrial and agricultural effluents as well as extraction of oil and gas reserves. Microbial communities can influence the fate of contaminants and nutrients. However, insight into the microbial ecology of the Caspian Sea significantly lags behind other marine systems. Here we describe microbial biomass, diversity and composition in sediments collected from three sampling stations in the Caspian Sea. Illumina sequencing of 16S rRNA genes revealed the presence of a number of known bacterial and archaeal heterotrophs suggesting that organic carbon is a primary factor shaping microbial communities. Surface sediments collected from bottom waters with low oxygen levels were dominated by Gammaproteobacteria while surface sediments collected from bottom waters under hypoxic conditions were dominated by Deltaproteobacteria, specifically sulfate-reducing bacteria. Thaumarchaeota was dominant across all surface sediments indicating that nitrogen cycling in this system is strongly influenced by ammonia-oxidizing archaea. This study provides a baseline assessment that may serve as a point of reference as this system changes or as the efficacy of new remediation efforts are implemented. PMID:25764536

  19. Microbial community composition and diversity in Caspian Sea sediments.

    PubMed

    Mahmoudi, Nagissa; Robeson, Michael S; Castro, Hector F; Fortney, Julian L; Techtmann, Stephen M; Joyner, Dominique C; Paradis, Charles J; Pfiffner, Susan M; Hazen, Terry C

    2015-01-01

    The Caspian Sea is heavily polluted due to industrial and agricultural effluents as well as extraction of oil and gas reserves. Microbial communities can influence the fate of contaminants and nutrients. However, insight into the microbial ecology of the Caspian Sea significantly lags behind other marine systems. Here we describe microbial biomass, diversity and composition in sediments collected from three sampling stations in the Caspian Sea. Illumina sequencing of 16S rRNA genes revealed the presence of a number of known bacterial and archaeal heterotrophs suggesting that organic carbon is a primary factor shaping microbial communities. Surface sediments collected from bottom waters with low oxygen levels were dominated by Gammaproteobacteria while surface sediments collected from bottom waters under hypoxic conditions were dominated by Deltaproteobacteria, specifically sulfate-reducing bacteria. Thaumarchaeota was dominant across all surface sediments indicating that nitrogen cycling in this system is strongly influenced by ammonia-oxidizing archaea. This study provides a baseline assessment that may serve as a point of reference as this system changes or as the efficacy of new remediation efforts are implemented.

  20. Archaeal Diversity in Marine Sediments in the South China Sea

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Wang, P.; Liu, Z.; Zhao, M.; Zhang, C.

    2010-12-01

    Archaea are widespread and play an important role in the global carbon and nitrogen cycles. However, we still have limited knowledge about archaeal diversity and their function in the natural environment. The purpose of this study was to examine the diversity, distribution and abundance of archaea associated with methane-rich sediments in the South China Sea. A gravity core (HQ08-48PC, 714 cm) was collected from the northern South China Sea and aseptically sliced into 20-cm sections. Samples from near the surface (0-20 cm), middle (350-370 cm) and bottom (630-650 cm) of the core were used for the construction of archaeal clone libraries. Chemical analysis indicated that the core was rich in methane (13.6-58.8 ppm) and had low TOC/TN ratios (< 8), which indicated a marine source of the organic matter. Total amino acids ranged between 2.72 µmol/g and 8.75 µmol/g. Phylogenetic analysis revealed that archaeal community structures were dramatically different and Crenarchaeaota dominates over Euryarchaeota among the surface, middle and bottom sediments of the core. The dominant archaeal groups were MGI (40%), MBGB (27%) and MCG (9%) in the surface sediment, MCG (35%), MBGD (20%) and MCG (20%) in the middle sediment, and MCG (52%) and MBGD (33%) in the bottom sediment. MCG and MBGD increased in phytotypes with increasing depth of the core, indicating their potential importance in deeper marine subsurface. The archaeal lipids (GDGTs) showed an increase in abundance with depth. Calculations of TEX86 based on certain types of GDGTs suggested a dramatic change in sea surface temperature (SST) that might correspond to the transition from the last glacial maximum (LGM) to post-glacial period. This study will enhance our understanding of archaeal diversity and function as well as their paleoclimate applications in the South China Sea.

  1. Geological evolution and analysis of confirmed or suspected gas hydrate localities: Volume 10, Basin analysis, formation and stability of gas hydrates of the Aleutian Trench and the Bering Sea

    SciTech Connect

    Krason, J.; Ciesnik, M.

    1987-01-01

    Four major areas with inferred gas hydrates are the subject of this study. Two of these areas, the Navarin and the Norton Basins, are located within the Bering Sea shelf, whereas the remaining areas of the Atka Basin in the central Aleutian Trench system and the eastern Aleutian Trench represent a huge region of the Aleutian Trench-Arc system. All four areas are geologically diverse and complex. Particularly the structural features of the accretionary wedge north of the Aleutian Trench still remain the subjects of scientific debates. Prior to this study, suggested presence of the gas hydrates in the four areas was based on seismic evidence, i.e., presence of bottom simulating reflectors (BSRs). Although the disclosure of the BSRs is often difficult, particularly under the structural conditions of the Navarin and Norton basins, it can be concluded that the identified BSRs are mostly represented by relatively weak and discontinuous reflectors. Under thermal and pressure conditions favorable for gas hydrate formation, the relative scarcity of the BSRs can be attributed to insufficient gas supply to the potential gas hydrate zone. Hydrocarbon gas in sediment may have biogenic, thermogenic or mixed origin. In the four studied areas, basin analysis revealed limited biogenic hydrocarbon generation. The migration of the thermogenically derived gases is probably diminished considerably due to the widespread diagenetic processes in diatomaceous strata. The latter processes resulted in the formation of the diagenetic horizons. The identified gas hydrate-related BSRs seem to be located in the areas of increased biogenic methanogenesis and faults acting as the pathways for thermogenic hydrocarbons.

  2. Sedimentation and mixing rates of radionuclides in Barents Sea sediments off Novaya Zemlya

    NASA Astrophysics Data System (ADS)

    Smith, J. N.; Ellis, K. M.; Naes, K.; Dahle, S.; Matishov, D.

    Radionuclide measurements have been conducted on sediment cores collected in 1992 in the south-eastern region of the Barents Sea, known as the Pechora Sea. Cesium-137 and 239,24OPu activities in surface sediments are generally less than 30 Bq/kg, with the highest levels being measured in sediments off the southwestern coastline of the island of Novaya Zemlya. High correlations between both 137Cs and 239,24OPu and the concentration of fine (< 63 μm) particles in surface sediments indicate that much of the variance in radionuclide concentrations throughout the Pechora Sea can be explained by particle size fractionation. However, elevated activities of 137Cs (138 Bq/kg), 60Co (92 Bq/kg), 241Am (433 Bq/kg), and especially 239,24OPu (8.47 × 103 Bq/kg) were measured in one surface sediment sample from the fjord of Chernaya Bay on the southern coast of Novaya Zemlya. The source of radioactive contamination is two underwater nuclear tests conducted in Chernaya Bay in 1955 and 1957. The 238Pu /239,240Vu activity ratio of 0.0245 in Chernaya Bay is equivalent to values measured in global fallout. The 240Pu /239Pu atom ratio (0.0304), measured by mass spectrometry, is much lower than values (0.18) typical of global fallout, but is consistent with ratios measured for fallout from the early (1951-1955) series of weapons tests at the Nevada Test Site. The timing of the Chernaya Bay source term, estimated from the 241Am /241Pu ratio, is consistent with the timing of the 1955 and 1957 underwater nuclear tests. Relatively low initial yields of 241Pu ( 241Pu /239Pu atom ratio = 0.00 123) in these tests have resulted in relatively low 241Am /239,240Pu activity ratios (0.05) in recent sediments in Chernaya Bay. Radionuclide tracer profiles in cores from the Pechora Sea can be simulated using a two-layer biodiffusion model with rapid, near-homogeneous mixing in the surface mixed layer and reduced mixing in the deep layer. Lead-210 profiles are consistent with a wide range of

  3. Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments

    NASA Astrophysics Data System (ADS)

    Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B.

    2012-10-01

    Investigated sediment cores from the southeastern Black Sea provide a high-resolution record from mid latitudes of the Laschamp geomagnetic polarity excursion. Age constraints are provided by 16 AMS 14C ages, identification of the Campanian Ignimbrite tephra (39.28±0.11 ka), and by detailed tuning of sedimentologic parameters of the Black Sea sediments to the oxygen isotope record from the Greenland NGRIP ice core. According to the derived age model, virtual geomagnetic pole (VGP) positions during the Laschamp excursion persisted in Antarctica for an estimated 440 yr, making the Laschamp excursion a short-lived event with fully reversed polarity directions. The reversed phase, centred at 41.0 ka, is associated with a significant field intensity recovery to 20% of the preceding strong field maximum at ˜50 ka. Recorded field reversals of the Laschamp excursion, lasting only an estimated ˜250 yr, are characterized by low relative paleointensities (5% relative to 50 ka). The central, fully reversed phase of the Laschamp excursion is bracketed by VGP excursions to the Sargasso Sea (˜41.9 ka) and to the Labrador Sea (˜39.6 ka). Paleomagnetic results from the Black Sea are in excellent agreement with VGP data from the French type locality which facilitates the chronological ordering of the non-superposed lavas that crop out at Laschamp-Olby. In addition, VGPs between 34 and 35 ka reach low northerly to equatorial latitudes during a clockwise loop, inferred to be the Mono lake excursion.

  4. Archaeal diversity in surface sediments of the South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, P.; Wei, Y.; Zhang, C.

    2010-12-01

    The South China Sea is one of the largest marginal seas on Earth and known to be one of the global hot spots of biodiversity. Yet, little is known about the abundance, diversity, and distribution of archaea in it. In this study the diversity and distribution of archaea in the surface sediments of the South China Sea were investigated. The samples were collected from seven sites from south to north of the sea with water depths ranging from 1455 m to 3697 m. Phylogenetic analysis revealed that the relative abundances of Euryarchaeota and Crenarchaeota species (OTUs at 2% cutoff) varied from site to site (Eury: 19.4%-67.6%, Cren: 32.4%-80.6%); however, they were about equal in species distribution (46.9% and 53.1%, respectively) for the total seven archaeal clone libraries. The Crenarchaeota predominates in MD05-2902 and MD05-2904 (80.6% and 70.4%); the Euryarchaeota predominates in MD05-2894 (67.6%). The archaeal groups MGI, MBGB, MCG and SAGMEG were dominant in most of the surface samples. MBGE was only dominant in MD05-2894 (64.7%). Overall, these results indicate that the community structures of archaea vary considerably in the surface sediments of the South China Sea.

  5. δ(34)S values in recent sea sediments and their significance using several sediment profiles from the western Baltic Sea.

    PubMed

    Hartmann, Martin; Nielsen, Heimo

    2012-01-01

    The isotope ratios of various sulphur components (total sulphur content in the sediment, sulphate and H(2)S in the pore-water) were measured in a number of cores from recent marine sediments taken from the Kieler Bucht (Kiel Bay) region in the western Baltic Sea. Additionally, the quantitative contents of total sulphur, sulphate, sulphide, chloride, organic carbon, iron and water in the sediment and in the pore-water solutions, respectively, were determined. These investigations provided the following results: 1. The sulphur contained in the sediment (∼ 0.3-2% of the dry sample) was for the most part introduced only after sedimentation. This confirms the deliberations of Kaplan et al. [The Distribution and Isotopic Abundance of Sulfur in Recent Marine Sediments off Southern California, Geochim. Cosmochim. Acta 27, 297 (1963)]. The organic substance contributes to the sulphur content of the sediment only to an insignificant degree (in our samples with ∼5-10% of the total sulphur). 2. The sulphate in the pore-waters has been identified as a source for sulphur in the sediment. During normal sedimentation, the exchange of sulphate by diffusion significant for changes in the sulphur content goes down to a sediment depth of 4-6 cm. In this process, the sulphate consumed by reduction and formation of sulphide or pyrite is mostly replaced. The uppermost sediment layer thus represents a partially open system for the total sulphur. The diagenesis of the sulphur is allochemical. At depths below 4-6 cm, we are dealing with a closed system. The further diagenesis of sulphur here is isochemical. 3. The isotope values of the sediment sulphur are influenced primarily by sulphur which comes into the sediment by diffusion and which is bound by subsequent bacteriological reduction as either sulphide or pyrite. As a consequence of the prevailing reduction of (32)S and reverse-diffusion of sulphate into the open sea water, a (32)S enrichment takes place in the uppermost layer of

  6. Distribution of phosphorus in the eastern Adriatic Sea sediments (Croatia)

    NASA Astrophysics Data System (ADS)

    Matijević, Slavica; Bogner, Danijela; Kušpilić, Grozdan; Veža, Jere

    2014-05-01

    Phosphorus (P) is very important nutrient for the eastern Adriatic Sea owing to its limiting role in the primary production. Orthophosphate concentrations are low (median HPO42- value: 0.039 µmol dm-3) as a consequence of relatively small number of freshwater inflows and cyclonic circulation of oligotrophic eastern Mediterranean water masses. Due to anthropogenic influence in coastal areas such as bays, estuaries and channel waters, P concentrations increment occurred leading to the formation of trophic gradient from the open sea towards the coast. As marine sediment presents the ultimate sink for particulate organic P from the water column, as well as for inorganic P forms, knowledge about distribution of different sediment P species is of great importance for understanding the burial, diagenesis and environmental geochemical significance of P. This paper presents results of P distribution at the eastern Adriatic sites of different trophic status (open sea, channel, estuary, semi-enclosed bay under the anthropogenic influence and fish farms) during 2002-2012. In the water column dissolved and particulate inorganic and organic P were analyzed. In all sediments total phosphorus (organic and inorganic P) was determined, while at certain sites beside organic P, inorganic P forms were examined using modified SEDEX methods (P in biogenic - P-FD; authigenic - P-AUT and in detrital apatite - P-DET; phosphorus bound to iron oxides and hydroxides - P-Fe). Various geochemical variables in the water column and sediment (HPO42- concentration, sediment redox potential, granulometric composition, carbonate content, iron, organic carbon and total nitrogen content) were also investigated. Results proved total P concentrations range between 3 and 161 µmol g-1, with highest values at sites under the strong anthropogenic impact including fish farms, estuaries and bay areas. Major inorganic P species in the eastern Adriatic was P-Fe form. Fish debris P species P-FD, prevailed in

  7. Ship-borne Observations of Atmospheric Black Carbon Aerosol Particles over the Arctic Ocean, Bering Sea, and North Pacific Ocean during September 2014

    NASA Astrophysics Data System (ADS)

    Taketani, F.; Miyakawa, T.; Takashima, H.; Komazaki, Y.; Kanaya, Y.; PAN, X.; Inoue, J.

    2015-12-01

    Measurements of refractory black carbon (rBC) aerosol particles using a highly sensitive online single particle soot photometer were performed on-board the R/V Mirai during a cruise across the Arctic Ocean, Bering Sea, and the North Pacific Ocean (31 August-9 October 2014). The measured rBC mass concentrations over the Arctic Ocean in the latitudinal region > 70°N were in the range 0-66 ng/m3 for 1-min averages, with an overall mean value of 1.0 ± 1.2 ng/m3. Single-particle-based observations enabled the measurement of such low rBC mass concentrations. The effects of long-range transport from continents to the Arctic Ocean were limited during the observed period, suggesting that such low rBC concentration levels would prevail over the Arctic Ocean. An analysis of rBC mixing states showed that particles with a non-shell/core structure made a significant contribution to the rBC particles detected over the Arctic Ocean.

  8. Tectonic Evolution of the Bristol Bay basin, southeast Bering Sea: Constraints from seismic reflection and potential field data

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.; McGeary, Susan E.; Klemperer, Simon L.

    2003-10-01

    We interpret the tectonic evolution of the Bristol Bay basin, also known as the North Aleutian basin, on the basis of a deep seismic reflection profile, lithologic data from a well, unreversed seismic refraction profiles, a bathymetry profile, a magnetics profile, forward modeling of a gravity profile, and flexural modeling of a basin-wide paleosurface. We present evidence that (1) an early or middle Eocene through late Miocene phase of extension led to fault-controlled subsidence; (2) a late Eocene through early Miocene phase of volcanic-arc loading led to flexural subsidence, which was amplified by additional factors possibly including lithospheric cooling, tectonic compression, reverse or thrust faulting, or small-scale intrusions of dense magma; and (3) a late Miocene through Holocene resurgence of arc volcanism and a northward prograding delta continued (or possibly increased) flexural subsidence in the back arc region. Our interpretations imply that the fault-controlled subsidence in the Bristol Bay basin is genetically linked to that found in the other outer Bering Shelf basins, but the subsequent flexural subsidence of these basins is not related. More fundamentally, our observations suggest that the basin's evolution is unusual and has components typically found in both back arc (extension) and retroarc foreland (flexure) basins.

  9. Bacterial methanogenesis in holocene sediments in the Baltic Sea

    SciTech Connect

    Lein, A.Y.; Namsaraev, B.B.; Trotsyuk, V.Y.; Ivanov, M.V.

    1981-01-01

    Soviet biologists have found evidence of viable methanogenic microorganisms in mud samples collected in 1978 from the Baltic Sea by the research ship Academician Kurchatov. Experiments with radioactive carbon and direct measurements of the samples' methane concentrations led to several conclusions: (1) the process of bacterial methanogenesis occurs mainly via carbon dioxide reduction, (2) the methanogenic intensity depends on the depth of the deposited sediment and its distance from land; shallow-water sediments found in gulfs produced more methane than deepwater ones taken from low spots, (3) organic-matter consumption during bacterial methane reduction makes up 0.14-7.9 mg of carbon/kg of wet mud per year; this is over 20 times less than during bacterial sulfate reduction, (4) The bulk of the methane generated migrates from the muds into the water and (5) marine sediments are undersaturated with methane, suggesting that the methane migrates via filtration of pore waters, not by diffusion.

  10. Change in coccolith size and morphology due to response to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi seas

    NASA Astrophysics Data System (ADS)

    Saruwatari, Kazuko; Satoh, Manami; Harada, Naomi; Suzuki, Iwane; Shiraiwa, Yoshihiro

    2016-05-01

    Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic oceans in 2010 were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains, namely MR57N isolated from the northern Bering Sea and MR70N at the Chukchi Sea. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (estimated as the percentage of calcified cells) was similar at 10-20 % at all temperatures. On the other hand, the specific growth rate of MR70N was affected less by changes in salinity in the range 26-35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters. The central area elements of coccoliths varied from thin lath type to well-calcified lath type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities with change in their morphology. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may

  11. Abundance and distribution of Arctic cod (Boreogadus saida) and other pelagic fishes over the U.S. Continental Shelf of the Northern Bering and Chukchi Seas

    NASA Astrophysics Data System (ADS)

    De Robertis, Alex; Taylor, Kevin; Wilson, Christopher D.; Farley, Edward V.

    2017-01-01

    We conducted acoustic-trawl (AT) surveys of the northern Bering and Chukchi Seas during ice-free periods in 2012 and 2013. The mixed species assemblages in the study area required refinement of standard AT survey methods, and adjustment of trawl catches for the effects of trawl selectivity. Sensitivity analyses indicate that the AT abundance estimates are relatively robust to the assumptions of the analysis. These surveys indicate that midwater fishes are dominated by age-0 Arctic cod (Boreogadus saida), age-0 saffron cod (Eleginus gracilis), capelin (Mallotus villosus), and Pacific herring (Clupea pallasii). In both years, age-0 Arctic cod were distributed principally ≥69.5 °N, age-0 saffron cod were abundant in coastal areas between 66.5 and 69.5 °N, and Pacific herring were distributed south of 67 °N. These three fishes exhibited consistent associations with temperature, salinity and bottom depth: e.g., age-0 Arctic cod were abundant at lower mean water column temperatures than saffron cod. In contrast, capelin were distributed throughout the study area, and were not consistently associated with environmental measures. There was a geographic trend in body length, with smaller Arctic cod, saffron cod and capelin in northern areas, but smaller herring in the south. Arctic cod, saffron cod, herring and capelin were all >2 times more abundant in 2013 than 2012. Sizeable populations of age-0 Arctic cod were observed in the northern Chukchi Sea, which suggests that this area is an important nursery ground. However, relatively few older Arctic cod were observed in this and other surveys of the area, which suggests that either overwinter mortality of age-0 Arctic cod is high, and/or these fish are not retained on the Chukchi shelf.

  12. Does location really matter? An inter-colony comparison of seabirds breeding at varying distances from productive oceanographic features in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Harding, Ann; Paredes, Rosana; Suryan, Robert; Roby, Daniel; Irons, David; Orben, Rachael; Renner, Heather; Young, Rebecca; Barger, Christopher; Dorresteijn, Ine; Kitaysky, Alexander

    2013-10-01

    Central place foragers, such as breeding seabirds, need to commute between their nests and foraging grounds, thus close proximity of the breeding colony to productive oceanographic features might be beneficial for seabird reproduction. We tested this hypothesis by investigating the at-sea foraging and breeding behavior of thick-billed murres (Uria lomvia) nesting at three colonies (Bogoslof, St. Paul, and St. George Islands) in the Bering Sea located at different distances from the productive continental shelf-break. We found that distances to feeding areas differed only during night trips among colonies. St. Paul murres foraged entirely on the shelf, whereas St. George murres commuted to the continental shelf-break at night and foraged on the shelf during the day. Bogoslof murres foraged in oceanic waters in close proximity to the colony. Murres breeding at the both Pribilof colonies spent less time attending nests and had higher levels of stress hormone corticosterone compared to murres breeding at Bogoslof, although chick-provisioning rates and fledging success were similar among the three colonies. Lower nest attendance and higher corticosterone suggest lower food availability in the Pribilof domain compared to the Bogoslof region. Murres breeding at the Pribilofs used different foraging strategies to buffer effects of food shortages on their reproduction: flight costs associated with longer distance night trips at St. George were presumably balanced by benefits of higher density and/or more lipid rich prey in the continental shelf-break regions, whereas the additional distance of St. Paul from the continental shelf-break may have outweighed any energetic gain. Murres exhibited a remarkable degree of plasticity of foraging strategies in response to changes in their food availability, but the breeding success of murres did not reflect either food limitations or the colony proximity to productive oceanographic features.

  13. Biophysical transport model suggests climate variability determines distribution of Walleye Pollock early life stages in the eastern Bering Sea through effects on spawning

    NASA Astrophysics Data System (ADS)

    Petrik, Colleen M.; Duffy-Anderson, Janet T.; Mueter, Franz; Hedstrom, Katherine; Curchitser, Enrique N.

    2015-11-01

    The eastern Bering Sea recently experienced an anomalously warm period followed by an anomalously cold period. These periods varied with respect to sea ice extent, water temperature, wind patterns, and ocean circulation. The distributions of Walleye Pollock early life stages also differed between periods, with larval stages found further eastward on the shelf in warm years. Statistical analyses indicated that these spatial distributions were more closely related to temperature than to other covariates, though a mechanism has not been identified. The objective of this study was to determine if variable transport could be driving the observed differences in pollock distributions. An individual-based model of pollock early life stages was developed by coupling a hydrodynamic model to a particle-tracking model with biology and behavior. Simulation experiments were performed with the model to investigate the effects of wind on transport, ice presence on time of spawning, and water temperature on location of spawning. This modeling approach benefited from the ability to individually test mechanisms to quantitatively assess the impact of each on the distribution of pollock. Neither interannual variability in advection nor advances or delays in spawning time could adequately represent the observed differences in distribution between warm and cold years. Changes to spawning areas, particularly spatial contractions of spawning areas in cold years, resulted in modeled distributions that were most similar to observations. The location of spawning pollock in reference to cross-shelf circulation patterns is important in determining the distribution of eggs and larvae, warranting further study on the relationship between spawning adults and the physical environment. The different distributions of pollock early life stages between warm and cold years may ultimately affect recruitment by influencing the spatial overlap of pollock juveniles with prey and predators.

  14. Influence of sea level change on sediment provenance variations since the last glaciation in the southern South China Sea

    NASA Astrophysics Data System (ADS)

    Jiwarungrueangkul, T.; Liu, Z.; Zhao, Y.

    2015-12-01

    Clay mineralogy and grain size of 170 sediment samples from Core MD05-2893 located near the Molengraaff paleo-river mouth on the upper Sunda slope in the southern South China Sea were investigated to assess the effect of sea level change on sediment provenance variations. The clay mineral results show high contents of smectite (35-55%), moderate contents of illite (16-31%), kaolinite (11-29%), and chlorite (8-15%). Due to distinction of clay mineral assemblages from each sediment provenance, the Indonesian Archipelago is the majority of smectite source, whereas North Boneo mainly provides illite to the southern South China Sea. Therefore, the smectite/illite ratio is applied to determine the sediment provenance variations. Both the mineralogical ratio and median grain size show consistent sediment source and dynamic variations since the last glaciation, in which case the response of sediment provenance change due to the sea level rise is expected. Our study suggests a three-stage evolution of the sediment provenance variation on the Sunda slope in the southern South China Sea: (1) during the low sea level stand of the last glaciation, the high content of smectite implies that the Indonesian Archipelago provided the majority of sediments to this area through the Molengraaff paleo-river system; (2) during the sea level rise of the deglaciation, the decreasing of smectite content but the increasing of illite indicates that the Indonesian Archipelago reduced in sediments supply due to regression of coastline, whereas North Boneo increased sediment supply; (3) during the high sea level stand of Holocene, the smectite content increases again, implying that the Indonesian Archipelago provides sediments to this area again through the ocean circulation. Consequently, the sea level rise mainly results in sediment provenance change in the southern South China Sea since the last deglaciation.

  15. Sediments in Arctic sea ice: Implications for entrainment, transport and release

    USGS Publications Warehouse

    Nurnberg, D.; Wollenburg, I.; Dethleff, D.; Eicken, H.; Kassens, H.; Letzig, T.; Reimnitz, E.; Thiede, Jorn

    1994-01-01

    Despite the Arctic sea ice cover's recognized sensitivity to environmental change, the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood. Sea ice sediment inclusions were studied in the central Arctic Ocean during the Arctic 91 expedition and in the Laptev Sea (East Siberian Arctic Region Expedition 1992). Results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central Arctic Ocean. This study documents the regional distribution and composition of particle-laden ice, investigates and evaluates processes by which sediment is incorporated into the ice cover, and identifies transport paths and probable depositional centers for the released sediment. In April 1992, sea ice in the Laptev Sea was relatively clean. The sediment occasionally observed was distributed diffusely over the entire ice column, forming turbid ice. Observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment. In the central Arctic Ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes. The surface sediment accumulation in central Arctic multi-year sea ice exceeds by far the amounts observed in first-year ice from the Laptev Sea in April 1992. Sea ice sediments are generally fine grained, although coarse sediments and stones up to 5 cm in diameter are observed. Component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles. The biogenous components, namely shells of pelecypods and benthic foraminiferal tests, point to a shallow, benthic, marine source area. Apparently, sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing. Clay mineralogy of ice-rafted sediments provides information on potential source areas. A smectite

  16. Quantifying the importance of sediment resuspension for the North Sea and Baltic Sea ecosystem

    NASA Astrophysics Data System (ADS)

    Nissen, Cara; Schrum, Corinna; Daewel, Ute; Fennel, Katja; Castaño Primo, Rocío

    2014-05-01

    Including sedimentary processes such as resuspension in marine coupled bio-physical models is crucial to realistically simulate the dynamics of biologically important chemical variables (e.g oxygen and the macro-nutrients nitrate, phosphate and silicate). These comprise diffusive release of dissolved nutrients and resuspension of particulate organic material, which occurs when a critical bottom shear stress (τcrit) acting on the sediment particles is exceeded. In global and regional modelling approaches sediment-water exchange is often parametrized by sedimentation and constant release rates and dynamic resuspension resolving the tidal cycle is often neglected in coupled physical-biological ecosystem models. During resuspension, sediment particles get transported back into the water column. Thereby, both the turbidity of the water and nutrient availability by releasing dissolved nutrients from the pore-water are changed. Since both light and nutrients are limiting factors in primary production, it is near by hand to suspect resuspension to play an important role in the growth of phytoplankton. Here, we assess the role of resuspension and its dynamic consideration for the modelled productivity and CO2 air-sea exchange in the North Sea and Baltic Sea using the coupled 3D physical-biological model ECOSMO. ECOSMO is a coupled hydrodynamic-sea ice-NPZD-carbonate-system model and is implemented for the North Sea and Baltic Sea. Its ecosystem module includes interactions between three functional groups of phytoplankton, two of zooplankton, detritus, oxygen, three nutrient cycles (nitrogen, phosphorus, silicate) and sediment pools. In the North Sea, wind forcing and strong tides lead to a frequent exceedance of the critical bottom shear stress and therefore, resuspension events take place regularly, especially in the shallow coastal areas where the tidal range is largest. Here, the model results indicate a clear increase in estimated primary production when dynamical

  17. Inactivated phosphorus by added aluminum in Baltic Sea sediment

    NASA Astrophysics Data System (ADS)

    Rydin, Emil

    2014-12-01

    Decreased phosphorus (P) retention in aquatic sediments during hypoxic periods results in increased P recycling to the water column. To revert to less productive conditions in the enclosed bays of the Baltic Sea archipelago, increased sediment P burial capacity is needed. Aluminum (Al) addition is considered to be a cost-effective lake restoration method, as it improves sediment P burial capacity. However, little is known about its ability to permanently bind P in brackish systems. In summer 2000, Al sulfate granules were added to a hypoxic bottom area in the Östhammar bay, Sweden. Sediment core samples from the area were collected 10 years later. A peak in Al and P was detected at 20 cm sediment depth, reflecting the added Al and P trapped to it. Only part of the added Al was recovered, but the recovered Al (8 g Al/m2) trapped P at a ratio of 5:1 (molar). Chemical fractionation showed that P extracted as 'Al-P' constituted 55% of the trapped P, indicating that Al added also trapped P extracted as other P forms.

  18. Geochemical peculiarities of sediments in the northeastern Black Sea

    NASA Astrophysics Data System (ADS)

    Rozanov, A. G.; Gursky, Yu. N.

    2016-11-01

    We present the results of chemical determinations of Al, Fe, Mn, Cu, Ni, Co, Cr, Pb, Sb, and As in Black Sea sediments over a profile from the Kerch Strait to the eastern part of a deep depression (2210 m). The lithological and geochemical variations were studied in the horizontal and vertical profiles of sediments up to 3 m thick. The tendencies in the distributions of the studied metals during Pleistocene and Holocene sedimentation were analyzed beginning from Neoeuxinian freshwater deposits via the overlaying Drevnechernomorian beds with elevated contents of sapropel to modern clayey carbonate deposits with coccolithophorids. Statistical factor analysis isolated five factors: two main factors (75% of the total dispersion) and three subordinate factors. The first leading biogenic factor (47% of dispersion) reflects the correlation between Corg, Cu, and Ni; the second terrigenous factor (28% of dispersion) combimes Fe, Al, Cr, and Sb. The chemical composition of the sediments reflects the manifestation of diagenesis of landslide processes and mud volcanism along with sedimentation regularities.

  19. Influence of timing of sea ice retreat on phytoplankton size during marginal ice zone bloom period on the Chukchi and Bering shelves

    NASA Astrophysics Data System (ADS)

    Fujiwara, A.; Hirawake, T.; Suzuki, K.; Eisner, L.; Imai, I.; Nishino, S.; Kikuchi, T.; Saitoh, S.-I.

    2016-01-01

    The size structure and biomass of a phytoplankton community during the spring bloom period can affect the energy use of higher-trophic-level organisms through the predator-prey body size relationships. The timing of the sea ice retreat (TSR) also plays a crucial role in the seasonally ice-covered marine ecosystem, because it is tightly coupled with the timing of the spring bloom. Thus, it is important to monitor the temporal and spatial distributions of a phytoplankton community size structure. Prior to this study, an ocean colour algorithm was developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll a (chl a) derived from cells larger than 5 µm to the total chl a, using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analysed the pixel-by-pixel relationships between FL during the marginal ice zone (MIZ) bloom period and TSR over the period of 1998-2013. The influences of the TSR on the sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and the TSR was widely found in the shelf region during the MIZ bloom season. However, we found a significant positive (negative) relationship between the SST (ΔOHC) and TSR. Specifically, an earlier sea ice retreat was associated with the dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that the duration of the nitrate supply, which is important for the growth of large-sized phytoplankton in this region (i.e. diatoms), can change according to the TSR. In addition, under-ice phytoplankton blooms are likely to occur in years with late ice retreat, because sufficient light for phytoplankton growth can pass through the ice and penetrate into the water columns as a result of an increase in solar radiation toward the summer solstice

  20. Influence of pycnocline topography and water-column structure on marine distributions of alcids (Aves: Alcidae) in Anadyr Strait, Northern Bering Sea, Alaska

    USGS Publications Warehouse

    Haney, J. Chris

    1991-01-01

    Systematic ship-board surveys were used to simultaneously record seabird abundances and resolve coarse-scale (3 to 10 km) horizontal and fine-scale (1 to 10 m) vertical variability in water-column structure and bathymetry for portions of the coastal zone in Anadyr Strait near western St. Lawrence Island, northern Bering Sea, Alaska, during August and September 1987. Three plankton-feeding alcids, parakeet (Cyclorrhynchus psittacula), crested (Aethia cristatella) and least (A. pusilla) auklets, each exhibited distinct associations for different pycnocline characteristics. Least auklets were more abundant in mixed water, but they also occurred within stratified water where the pycnocline and upper-mixed layer were shallow (≤8 m) and thin (≤10 m), respectively. Low body mass (85 g), high buoyancy, and relatively poor diving ability may have restricted this auklet to areas where water-column strata nearly intersected the surface, or to areas from which strata were absent altogether due to strong vertical mixing. Parakeet and crested auklets, which are larger-bodied (ca. 260 g) planktivores with presumably greater diving ability, were more abundant in stratified water, and both species exhibited less specific affinities for water-column characteristic at intermediate and shallow levels. All three auklets avoided locations with strong pycnocline gradients (≤0.22σtm−1), a crude index of the strong, subsurface shear in water velocities characteristic of this region. Auklet distributions in Anadyr Strait were consistent with: (1) strata accessibility, as estimated from relationships between body mass and relative diving ability, (2) possible avoidance of strong subsurface water motions, and (3) habits and distributions of plankton prey. In contrast, largebodied (>450 g) alcids [i.e., common (Uria aalge) and thick-billed (U. lomvia) murres, pigeon guillemots (Cephus columba), tufted (Fratercula cirrhata), and horned (F. corniculata) puffins feeding on fish or

  1. High-Precision 40Ar/39Ar Geochronology and Geology of St. George Island, Pribilof Islands, Alaska: Implications for Eruption Rates in the Bering Sea Basalt Province

    NASA Astrophysics Data System (ADS)

    Feeley, T. C.; Cosca, M. A.; Hamblock, J. M.; Underwood, S. J.

    2007-12-01

    New high-precision 40Ar/39Ar ages and geologic mapping establish an eruptive chronology for St. George Island, Pribilof Islands, Alaska. St. George is part of the Bering Sea basalt province (BSBP), a group of 15 late Cenozoic (mostly < 6 Ma) alkalic to tholeiitic basaltic volcanic fields widely distributed on islands in the Bering Sea, along the west coast of Alaska, and along the coast of northeast Russia. Twelve samples of washed, but otherwise untreated, whole-rock basalts from St. George were cut with a micro-wire saw into chips ~3 mm3 in size and irradiated for 40Ar/39Ar analysis. The chips were incrementally heated with a CO2 laser equipped with an integrator lens, and analyzed using a NU Instruments Noblesse mass spectrometer equipped with a Faraday cup and two ion counting electron multipliers. Detector intercalibration was done using automated air pipettes. A minimum of 20 heating steps were measured per sample, with the data often defining age plateaux. Isochron plots of the data yield ages ranging from 1.57 ± 0.04 to 2.89 ± 0.11 Ma, with trapped 40Ar/36Ar ratios ranging from 312 to 330. The stratigraphic positions of the dated rocks are known directly from field relations and there are no discrepancies between the 40Ar/39Ar ages and this sequence. Geochemical data combined with the age data indicate no progressive petrologic trends during evolution of the magmatic system, except for intermittent eruption of distinctive plagioclase-phyric basalts with low to moderate MgO contents (7 - 5 wt%) beginning at ~2.0 Ma. The new age data combined with volume estimates indicate an average subaerial eruption rate of ~107 m3km-2yr-1, which is adjusted for 3% sedimentary and ultramafic basement rocks beneath the volcanic pile, an average vesicularity of 5%, and an assumed surficial erosion value of 20%. This rate is identical to the estimate (110 m3km-2yr-1) by Mukasa et al. (JGR 112, 2007) for St. George Island. Both estimates, however, do not account for

  2. Sea-ice processes in the Laptev Sea and their importance for sediment export

    USGS Publications Warehouse

    Eicken, H.; Reimnitz, E.; Alexandrov, V.; Martin, T.; Kassens, H.; Viehoff, T.

    1997-01-01

    Based on remote-sensing data and an expedition during August-September 1993, the importance of the Laptev Sea as a source area for sediment-laden sea ice was studied. Ice-core analysis demonstrated the importance of dynamic ice-growth mechanisms as compared to the multi-year cover of the Arctic Basin. Ice-rafted sediment (IRS) was mostly associated with congealed frazil ice, although evidence for other entrainment mechanisms (anchor ice, entrainment into freshwater ice) was also found. Concentrations of suspended particulate matter (SPM) in patches of dirty ice averaged at 156 g m-3 (standard deviation ?? = 140 g m-3), with a background concentration of 5 g m-3. The potential for sediment entrainment over the broad, shallow Laptev Sea shelf during fall freeze-up was studied through analysis of remote-sensing data and weather-station records for the period 1979-1994. Freeze-up commences on 26 September (?? = 7 d) and is completed after 19 days (?? = 6 d). Meteorological conditions as well as ice extent prior to and during freeze-up vary considerably, the open-water area ranging between 107 x 103 and 447 x 103 km2. Ice motion and transport of IRS were derived from satellite imagery and drifting buoys for the period during and after the expedition (mean ice velocities of 0.04 and 0.05 m s-1, respectively). With a best-estimate sediment load of 16 t km-2 (ranging between 9 and 46 t km-2), sediment export from the eastern Laptev Sea amounts to 4 x 10-6 t yr-1, with extremes of 2 x 10-6 and 11 x 106 t yr-1. Implications for the sediment budget of the Laptev shelf, in particular with respect to riverine input of SPM, which may be of the same order of magnitude, are discussed.

  3. Modern processes controlling the sea bed sediment formation in Barents Sea

    NASA Astrophysics Data System (ADS)

    Balanyuk, I.; Dmitrievsky, A.; Shapovalov, S.; Chaikina, O.; Akivis, T.

    2009-04-01

    The Barents Sea is one of the key regions for understanding of the postglacial history of the climate and circulation of the World Ocean. There are the limits of warm North Atlantic waters penetration to the Arctic and a zone of interaction between Atlantic and Arctic waters. The Barents Se's limits are the deep Norwegian Sea in the West, the Spitsbergen Island and the Franz Josef Land and the deep Nansen trough in the North, the Novaya Zemlya archipelago in the East and the North shore of Europe in the South. An analysis of Eurasian-Arctic continental margin shows correspondence between the rift systems of the shelf with those of the ocean. This relation can be observed in the central Arctic region. All the rift systems underlying the sediment basin are expressed in the sea bed relief as spacious and extensive graben valleys burnished by lobes. Two transverse trenches cross both shelf and continental slope, namely the Medvezhinsky trench between Norway and Spitsbergen in the West and the Franz Victoria trench between Spitsbergen and the Franz Josef Land in the North. The Barents and the Kara Seas are connected by the Kara Gate Strait and wide transverse trough of Saint Anna in the North-West. The recent assessment of the eolian solid sediment supply to the Barents Sea is about 0.904 tons. The Barents Sea as a whole should be considered as "starving" in terms of its feeding with solid sediment matter. Observations show the considerable part of the sea bottom to be free of Holocene sediment cover. The more ancient Quaternary units or bedrock can be seen at the bottom surface. This phenomenon is the most typical for arches of relatively shallow elevations. Thick accumulations of new sediments are connected with fjords. The amount of sea ice delivered from the Barents Sea to the Arctic Ocean is 35 km3 a year. This value should be added by iceberg delivery from the North island of Novaya Zemlya, the Franz Josef Land, the Spitsbergen Island and North Norway but most of

  4. Natural radionuclide and plutonium content in Black Sea bottom sediments

    SciTech Connect

    Strezov, A.; Stoilova, T.; Yordanova, I.

    1996-01-01

    The content of uranium, thorium, radium, lead, polonium, and plutonium in bottom sediments and algae from two locations at the Bulgarian Black Sea coast have been determined. Some parent:progeny ratios for evaluation of the geochemical behavior of the nuclides have been estimated as well. The extractable and total uranium and thorium are determined by two separate radiochemical procedures to differentiate the more soluble chemical forms of the elements and to estimate the potential hazard for the biosphere and for humans. No distinct seasonal variation as well as no significant change in total and extractable uranium (also for {sup 226}Ra) content is observed. The same is valid for extractable thorium while the total thorium content in the first two seasons is slightly higher. Our data show that {sup 210}Po content is accumulated more in the sediments than {sup 210}Pb, and the evaluated disequilibria suggest that the two radionuclides belong to more recent sediment layers deposited in the slime samples compared to the silt ones for the different seasons. The obtained values for plutonium are in the lower limits of the data cited in literature, which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio {sup 238}Pu: {sup 239+240}Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural radionuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling locations for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed. 38 refs., 6 figs., 7 tabs.

  5. Natural radionuclide and plutonium content in Black Sea bottom sediments.

    PubMed

    Strezov, A; Yordanova, I; Pimpl, M; Stoilova, T

    1996-01-01

    The content of uranium, thorium, radium, lead, polonium, and plutonium in bottom sediments and algae from two locations at the Bulgarian Black Sea coast have been determined. Some parent:progeny ratios for evaluation of the geochemical behavior of the nuclides have been estimated as well. The extractable and total uranium and thorium are determined by two separate radiochemical procedures to differentiate the more soluble chemical forms of the elements and to estimate the potential hazard for the biosphere and for humans. No distinct seasonal variation as well as no significant change in total and extractable uranium (also for 226Ra) content is observed. The same is valid for extractable thorium while the total thorium content in the first two seasons is slightly higher. Our data show that 210Po content is accumulated more in the sediments than 210Pb, and the evaluated disequilibria suggest that the two radionuclides belong to more recent sediment layers deposited in the slime samples compared to the silt ones for the different seasons. The obtained values for plutonium are in the lower limits of the data cited in literature, which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio 238Pu:239 + 240Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural radionuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling locations for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed.

  6. Coastal erosion vs riverline sediment discharge in the Arctic shelfx seas

    USGS Publications Warehouse

    Rachold, V.; Grigoriev, M.N.; Are, F.E.; Solomon, Sean C.; Reimnitz, E.; Kassens, H.; Antonow, M.

    2000-01-01

    This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal ero- sion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45x106 t a-1) mainly of the Mackenzie River. which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10x106 t a-1, more than 70% of which are related to the Lena River. In comparison with the CBS. the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4x106 t a-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6x106 t a-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.

  7. Modern sedimentation and extreme event in the South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Huang; Su, Chih-Chieh

    2016-04-01

    The South China Sea is the largest marginal sea of the northwest Pacific. It is situated at the plate boundary of the Eurasian, Philippine Sea, and Indian plates and also on the North Western Pacific corridor of typhoons. The unique tectonic and climatic environment makes it has to face the potential of seafloor destructions, like submarine landslides and slumps, and high sediment discharges which induced by typhoon from Philippine. In this study, we analysis the sediment properties of modern extreme event records in cores and attempt to evaluate the history of extreme events in the South China Sea. Twelve gravity cores were collected in the central South China Sea basin and around Taiping island by using R/V Ocean Research 1 from 2014 to 2015 and a series of analysis including multi-sensor core logger, XRF core scanner (Itrax), core surface images, X-radiographs, bulk density, grain size, Pb-210 chronology and X-ray diffractometer were conducted in this study. On core surface images, an obvious brownish oxidized layer exist in core top with higher Pb-210 activity beneath this oxidized layer, and we speculate this layer is caused by nature hazard. According to the sampling time, we conjecture the oxidized layer might formed by typhoon Haiyan in 2013. In addition, the Itrax data shows high manganese content only exist in this layer which might related to the modern industrial pollution delivered by typhoon induced flooding from Philippine. The sedimentation rate of the non-event years in these cores which derived from Pb-210 chronology method is about 0.02 ~0.03 cm/yr. On contrary, the event layer caused by Haiyan with a recorded maximum 87cm deposits in the South China Sea. This study aims to characterize the typhoon induced deposits in the turbidite layer and use it to identify whether the other event layers recorded in these cores were related to typhoon activities and to reconstruct the strong tropical cyclone history in the western Pacific.

  8. Zooplankton species composition, abundance and biomass on the eastern Bering Sea shelf during summer: The potential role of water-column stability and nutrients in structuring the zooplankton community

    NASA Astrophysics Data System (ADS)

    Coyle, Kenneth O.; Pinchuk, Alexei I.; Eisner, Lisa B.; Napp, Jeffrey M.

    2008-08-01

    The southeastern Bering Sea sustains one of the largest fisheries in the United States, as well as wildlife resources that support valuable tourist and subsistence economies. The fish and wildlife populations in turn are sustained by a food web linking primary producers to apex predators through the zooplankton community. Recent shifts in climate toward warmer conditions may threaten these resources by altering productivity and trophic relationships in the ecosystem on the southeastern Bering Sea shelf. We examined the zooplankton community near the Pribilof Islands and on the middle shelf of the southeastern Bering Sea in summer of 1999 and 2004 to document differences and similarities in species composition, abundance and biomass by region and year. Between August 1999 and August 2004, the summer zooplankton community of the middle shelf shifted from large to small species. Significant declines were observed in the biomass of large scyphozoans ( Chrysaora melanaster), large copepods ( Calanus marshallae), arrow worms ( Sagitta elegans) and euphausiids ( Thysanoessa raschii, T. inermis) between 1999 and 2004. In contrast, significantly higher densities of the small copepods ( Pseudocalanus spp., Oithona similis) and small hydromedusae ( Euphysa flammea) were observed in 2004 relative to 1999. Stomach analyses of young-of-the-year (age 0) pollock ( Theragra chalcogramma) from the middle shelf indicated a dietary shift from large to small copepods in 2004 relative to 1999. The shift in the zooplankton community was accompanied by a 3-fold increase in water-column stability in 2004 relative to 1999, primarily due to warmer water above the thermocline, with a mean temperature of 7.3 °C in 1999 and 12.6 °C in 2004. The elevated water-column stability and warmer conditions may have influenced the zooplankton composition by lowering summer primary production and selecting for species more tolerant of a warm, oligotrophic environment. A time series of temperature from

  9. Paleoecology of late-glacial peats from the bering land bridge, Chukchi Sea shelf region, northwestern Alaska

    USGS Publications Warehouse

    Elias, S.A.; Short, S.K.; Phillips, R.L.

    1992-01-01

    Insect fossils and pollen from late Pleistocene nonmarine peat layers were recovered from cores from the shelf region of the Chukchi Sea at depths of about 50 m below sea level. The peats date to 11,300-11,000 yr B.P. and provide a limiting age for the regional Pleistocene-Holocene marine transgression. The insect fossils are indicative of arctic coastal habitats like those of the Mackenzie Delta region (mean July temperatures = 10.6-14??C) suggesting that 11,000 yr ago the exposed Chukchi Sea shelf had a climate substantially warmer than modern coastal regions of the Alaskan north slope. The pollen spectra are consistent with the age assignment to the Birch Interval (14,000-9000 yr B.P.). The data suggest a meadow-like graminoid tundra with birch shrubs and some willow shrubs growing in sheltered areas. ?? 1992.

  10. Delineating ecological regions in marine systems: Integrating physical structure and community composition to inform spatial management in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Baker, Matthew R.; Hollowed, Anne B.

    2014-11-01

    Characterizing spatial structure and delineating meaningful spatial boundaries have useful applications to understanding regional dynamics in marine systems, and are integral to ecosystem approaches to fisheries management. Physical structure and drivers combine with biological responses and interactions to organize marine systems in unique ways at multiple scales. We apply multivariate statistical methods to define spatially coherent ecological units or ecoregions in the eastern Bering Sea. We also illustrate a practical approach to integrate data on species distribution, habitat structure and physical forcing mechanisms to distinguish areas with distinct biogeography as one means to define management units in large marine ecosystems. We use random forests to quantify the relative importance of habitat and environmental variables to the distribution of individual species, and to quantify shifts in multispecies assemblages or community composition along environmental gradients. Threshold shifts in community composition are used to identify regions with distinct physical and biological attributes, and to evaluate the relative importance of predictor variables to determining regional boundaries. Depth, bottom temperature and frontal boundaries were dominant factors delineating distinct biological communities in this system, with a latitudinal divide at approximately 60°N. Our results indicate that distinct climatic periods will shift habitat gradients and that dynamic physical variables such as temperature and stratification are important to understanding temporal stability of ecoregion boundaries. We note distinct distribution patterns among functional guilds and also evidence for resource partitioning among individual species within each guild. By integrating physical and biological data to determine spatial patterns in community composition, we partition ecosystems along ecologically significant gradients. This may provide a basis for defining spatial management

  11. Spatial Match-Mismatch between Juvenile Fish and Prey Provides a Mechanism for Recruitment Variability across Contrasting Climate Conditions in the Eastern Bering Sea

    PubMed Central

    Siddon, Elizabeth Calvert; Kristiansen, Trond; Mueter, Franz J.; Holsman, Kirstin K.; Heintz, Ron A.; Farley, Edward V.

    2013-01-01

    Understanding mechanisms behind variability in early life survival of marine fishes through modeling efforts can improve predictive capabilities for recruitment success under changing climate conditions. Walleye pollock (Theragra chalcogramma) support the largest single-species commercial fishery in the United States and represent an ecologically important component of the Bering Sea ecosystem. Variability in walleye pollock growth and survival is structured in part by climate-driven bottom-up control of zooplankton composition. We used two modeling approaches, informed by observations, to understand the roles of prey quality, prey composition, and water temperature on juvenile walleye pollock growth: (1) a bioenergetics model that included local predator and prey energy densities, and (2) an individual-based model that included a mechanistic feeding component dependent on larval development and behavior, local prey densities and size, and physical oceanographic conditions. Prey composition in late-summer shifted from predominantly smaller copepod species in the warmer 2005 season to larger species in the cooler 2010 season, reflecting differences in zooplankton composition between years. In 2010, the main prey of juvenile walleye pollock were more abundant, had greater biomass, and higher mean energy density, resulting in better growth conditions. Moreover, spatial patterns in prey composition and water temperature lead to areas of enhanced growth, or growth ‘hot spots’, for juvenile walleye pollock and survival may be enhanced when fish overlap with these areas. This study provides evidence that a spatial mismatch between juvenile walleye pollock and growth ‘hot spots’ in 2005 contributed to poor recruitment while a higher degree of overlap in 2010 resulted in improved recruitment. Our results indicate that climate-driven changes in prey quality and composition can impact growth of juvenile walleye pollock, potentially severely affecting recruitment

  12. Spatial match-mismatch between juvenile fish and prey provides a mechanism for recruitment variability across contrasting climate conditions in the eastern Bering Sea.

    PubMed

    Siddon, Elizabeth Calvert; Kristiansen, Trond; Mueter, Franz J; Holsman, Kirstin K; Heintz, Ron A; Farley, Edward V

    2013-01-01

    Understanding mechanisms behind variability in early life survival of marine fishes through modeling efforts can improve predictive capabilities for recruitment success under changing climate conditions. Walleye pollock (Theragra chalcogramma) support the largest single-species commercial fishery in the United States and represent an ecologically important component of the Bering Sea ecosystem. Variability in walleye pollock growth and survival is structured in part by climate-driven bottom-up control of zooplankton composition. We used two modeling approaches, informed by observations, to understand the roles of prey quality, prey composition, and water temperature on juvenile walleye pollock growth: (1) a bioenergetics model that included local predator and prey energy densities, and (2) an individual-based model that included a mechanistic feeding component dependent on larval development and behavior, local prey densities and size, and physical oceanographic conditions. Prey composition in late-summer shifted from predominantly smaller copepod species in the warmer 2005 season to larger species in the cooler 2010 season, reflecting differences in zooplankton composition between years. In 2010, the main prey of juvenile walleye pollock were more abundant, had greater biomass, and higher mean energy density, resulting in better growth conditions. Moreover, spatial patterns in prey composition and water temperature lead to areas of enhanced growth, or growth 'hot spots', for juvenile walleye pollock and survival may be enhanced when fish overlap with these areas. This study provides evidence that a spatial mismatch between juvenile walleye pollock and growth 'hot spots' in 2005 contributed to poor recruitment while a higher degree of overlap in 2010 resulted in improved recruitment. Our results indicate that climate-driven changes in prey quality and composition can impact growth of juvenile walleye pollock, potentially severely affecting recruitment variability.

  13. Glacial-interglacial changes in sediment source to the Meiji sediment deposit in the North Pacific Ocean using Ar and Nd isotopic fingerprints: A drift deposit or a displaced Yukon River submarine fan?

    NASA Astrophysics Data System (ADS)

    Vanlaningham, S.; Pisias, N.; Duncan, R. A.

    2007-12-01

    A large sediment deposit known as the Meiji Drift lies just outside of the Bering Sea in the northwestern Pacific Ocean. It is thought that the deposit is related to deep-water circulation in (and out of) the Bering Sea, although no notable deep water forms there presently. We have applied bulk sediment 40Ar-39Ar dating and Nd isotopic analyses to the silt-sized fraction from Ocean Drilling Project core site 884 (51°27' N, 168°20' E). Measurements are made over the last 130,000 years to document sediment source(s) to the Meiji Drift and to determine whether provenance changes through time. There is an order-of-magnitude range in bulk sediment 40Ar-39Ar ages and around ten ɛNd units of change, both varying on glacial-interglacial cycles. During glacials, bulk sediment 40Ar-39Ar plateau ages range between 40-80 Ma while Nd isotopic values range from ɛNd = -1 to ɛNd = +2. During interglacials, the downcore samples become considerably younger and more radiogenic, with bulk sediment plateau ages falling between 2-15 Ma and Nd isotopic values ranging between ɛNd = +5 to ɛNd = +9. These data illustrate that older source rocks such as those drained by the Yukon River are the dominant origin of sediments during glacials. This is when the Bering Strait is exposed and all terrigenous sediment entering the Bering region is routed to the North Pacific. Conversely, the Kamchatkan and Aleutian Volcanic Arcs straddling the Meiji Drift contribute the majority of sediment during interglacials. Notably, however, the Ar-Nd provenance record from the Meiji Drift suggests that Yukon-derived material continued to be transported to the North Pacific further into the Holocene and shut off around 5,000 years ago. This is coincident with a major reorganization of the Yukon River delta and further illustrates a possible linkage between the Yukon River and the Meiji Drift. The large ranges in bulk Ar and Nd isotopic values illuminate that this approach will reveal a detailed history of

  14. 78 FR 63951 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-25

    ... the hook-and-line C/Ps active in the GOA that are not FLCC members. The Council noted that although... at subpart H of 50 CFR part 600. Background The proposed action would amend the BSAI FMP and revise... licenses that allow vessels to catch and process at-sea are assigned a catcher/processor (C/P)...

  15. 77 FR 52674 - Fisheries of the Exclusive Economic Zone Off Alaska; Groundfish Fisheries in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-30

    ...), Commerce. ACTION: Notice of a public scoping meeting for an environmental impact statement; request for...), will hold a public scoping meeting and accept written comments from the public to determine the issues... cumulative impacts to be addressed in the Environmental Impact Statement (EIS) for the Steller Sea...

  16. Incorporating Sediment Compaction Into a Gravitationally Self-consistent Model for Global Sea-level Change

    NASA Astrophysics Data System (ADS)

    Ferrier, K.; Mitrovica, J. X.

    2015-12-01

    In sedimentary deltas and fans, sea-level changes are strongly modulated by the deposition and compaction of marine sediment. The deposition of sediment and incorporation of water into the sedimentary pore space reduces sea level by increasing the elevation of the seafloor, which reduces the thickness of sea-water above the bed. In a similar manner, the compaction of sediment and purging of water out of the sedimentary pore space increases sea level by reducing the elevation of the seafloor, which increases the thickness of sea water above the bed. Here we show how one can incorporate the effects of sediment deposition and compaction into the global, gravitationally self-consistent sea-level model of Dalca et al. (2013). Incorporating sediment compaction requires accounting for only one additional quantity that had not been accounted for in Dalca et al. (2013): the mean porosity in the sediment column. We provide a general analytic framework for global sea-level changes including sediment deposition and compaction, and we demonstrate how sea level responds to deposition and compaction under one simple parameterization for compaction. The compaction of sediment generates changes in sea level only by changing the elevation of the seafloor. That is, sediment compaction does not affect the mass load on the crust, and therefore does not generate perturbations in crustal elevation or the gravity field that would further perturb sea level. These results have implications for understanding sedimentary effects on sea-level changes and thus for disentangling the various drivers of sea-level change. ReferencesDalca A.V., Ferrier K.L., Mitrovica J.X., Perron J.T., Milne G.A., Creveling J.R., 2013. On postglacial sea level - III. Incorporating sediment redistribution. Geophysical Journal International, doi: 10.1093/gji/ggt089.

  17. Exploiting sedimentation datasets to model the impact of sediment loading on sea level at the Yellow River Delta

    NASA Astrophysics Data System (ADS)

    Pico, T.; Mitrovica, J. X.; Ferrier, K.

    2015-12-01

    In order to accurately depict glacial isostatic adjustment (GIA) of the solid Earth and consequent sea level, it is necessary to incorporate the loading and unloading of the crust occurring over glacial cycles in the form of sediment erosion and deposition. The inclusion of sediment loading in GIA models becomes even more imperative when studying sea level at densely populated centers along coastlines, many of which are located at large river deltas. Sediment deposition at deltas influences sea level by introducing a load, which in turn alters crustal elevation and perturbs the gravitational field. These sediment loads vary in space and time over glacial cycles, as deltas prograde during sea-level highstands and shelves are exposed during lowstands. The Yellow River serves as an archetypical case study of fluvial response to glacial cycles. Draining the highly erodible, glacially derived Loess Plateau, the Yellow River's sediment flux is the 2nd highest in the world. This site provides an ideal location for modeling sediment loads in order to investigate how glacial cycles control sedimentation history and regional sea level. This study employs datasets constraining deposition and erosion that are physically recorded in dated sediment cores, seismic sections, and river flux measurements. These sedimentary datasets elucidate how loading varies spatially and with time in the basin, but also, importantly, data of fossil-bearing cores act to constrain sea level history during this period. Thus, we utilize physical sedimentary data as both an input to our model and a check on the predicted local sea level. Our gravitationally self-consistent global model is then capable of exploring and constraining how evolving sediment loads and migrating depositional centers impact local predicted crustal deformation, and therefore sea-level, over glacial timescales.

  18. Change in coccolith morphology by responding to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Saruwatari, K.; Satoh, M.; Harada, N.; Suzuki, I.; Shiraiwa, Y.

    2015-11-01

    Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic Oceans during the R/V MIRAI cruise in 2010 (MR10-05) were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains of MR57N isolated from the northern Bering Sea (56°58' N, 167°11' W) and MR70N at the Chukchi Sea (69°99' N, 168° W). This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (the percentage of calcified cells) was similar at 10-20 % at all temperatures. On the other hand, the specific growth rate of strain MR70N was affected less by changes in salinity in the range 26-35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters, such as length of the distal shield (LDS), length of the inner central area (LICA), and the thickness of distal shield elements. The central area elements of coccoliths varied from grilled type to closed type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities due to their marked morphometric adaptation ability. Because all

  19. Foraging segregation of two congeneric diving seabird species (common and thick-billed murres) breeding on St. George Island, Bering Sea

    NASA Astrophysics Data System (ADS)

    Kokubun, N.; Yamamoto, T.,; Sato, N.; Watanuki, Y.; Will, A.; Kitaysky, A. S.; Takahashi, A.

    2015-11-01

    Sub-arctic environmental changes are expected to affect the ecology of marine top predators. We examined the characteristics of foraging behavior of two sympatric congeneric diving seabirds, common (Uria aalge: hereafter COMU) and thick-billed (U. lomvia: hereafter TBMU) murres breeding on St. George Island located in the seasonal sea-ice region of the Bering Sea. We investigated their flight duration, diel patterns of dive depth, and underwater wing strokes, along with morphology and blood stable isotopes. Acceleration-temperature-depth data loggers were attached to chick-guarding birds, and behavioral data were obtained from 7 COMU and 12 TBMU. Both species showed similar trip duration (13.21 ± 4.79 h for COMU and 10.45 ± 7.09 h for TBMU) and similar diurnal patterns of diving (frequent dives to various depths in the daytime and less frequent dives to shallow depths in the nighttime). During the daytime, dive depths of COMU had two peaks in shallow (18.1 ± 6.0 m) and deep (74.2 ± 8.7 m) depths, while those of TBMU were 20.2 ± 7.4 m and 59.7 ± 7.9 m. COMU showed more frequent wing strokes during the bottom phase of dives (1.90 ± 0.11 s-1) than TBMU (1.66 ± 0.15 s-1). Fishes occurred with higher proportion in the bill-loads brought back to chicks in COMU (85 %) than in TBMU (56 %). δ15N value of blood was significantly higher in COMU (14.47 ± 0.27 ‰) than in TBMU (13.14 ± 0.36 ‰). Relatively small wing area (0.053 ± 0.007 m2) of COMU compared to TBMU (0.067 ± 0.007 m2) may make them more agile underwater and thus enable them to target more mobile prey including larger fishes that inhabit deeper depths. These differences in foraging behavior between COMU and TBMU might explain the differences in their responses to long-term marine environmental changes.

  20. 76 FR 6083 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Pollock in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-03

    ... Sea CDQ DFA. The remaining 12,500 mt of pollock is apportioned to the AFA Inshore sector (50 percent), AFA catcher/processor sector (40 percent), and the AFA mothership sector (10 percent). The 2011...,588 76,260 ICA \\1\\ 24,768 n/a n/a n/a 33,804 n/a n/a n/a AFA Inshore 353,466 140,486 98,340...

  1. 78 FR 14932 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Pollock in the Bering Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ... Sea CDQ DFA. The remaining 10,500 mt of pollock is apportioned to the AFA Inshore sector (50 percent), AFA catcher/processor sector (40 percent), and the AFA mothership sector (10 percent). The 2013.../a 33,669 n/a n/a n/a AFA Inshore 549,551 219,820 153,874 329,730 544,316 217,726 152,408 326,589...

  2. Multi-Decadal Variability in the Bering Sea: A Synthesis of Model Results and Observations from 1948 to the Present

    DTIC Science & Technology

    2013-12-01

    Alaska from 1948–2009. .............................36 Figure 21. H1 case run monthly mean heat content and ice thickness anomalies with 13, 37, and...atmospheric loading, clouds and fronts, ice sheets/ caps , permafrost, river runoff, and air-sea ice -land interactions and coupling (Maslowski et al...are addition of model components for ice sheets, ice caps , mountain glaciers, and dynamic vegetation (Maslowski et al. 2012). The RASM model domain

  3. Hydrodynamic condition and suspended sediment diffusion in the Yellow Sea and East China Sea

    NASA Astrophysics Data System (ADS)

    Li, Guangxue; Qiao, Lulu; Dong, Ping; Ma, Yanyan; Xu, Jishang; Liu, Shidong; Liu, Yong; Li, Jianchao; Li, Pin; Ding, Dong; Wang, Nan; Olusegun A, Dada; Liu, Ling

    2016-08-01

    Based on monthly averaged current, temperature, and salinity, we analyzed the changes of suspended sediment concentration (SSC) and the relationship with the warm current, coastal current, and cold water mass (CWM) in the East China Seas (ECSs). The result shows that the coastal current and surface diluted water are the route for transporting suspended sediment. The Kuroshio and its derived warm current branches play the important role of the continental shelf circulation system and control the diffusion of suspended sediment. High SSC has been mainly concentrated in coastal current and CWM. Two sedimentary dynamic patterns have been identified. The winter-half-year pattern lasts almost 7 months. The coastal currents off the Shandong Peninsula, northern Jiangsu, Zhejiang-Fujian coast are the main routes for diffusion and deposition of the suspended sediment from the Yellow River and Changjiang River. The summer-half-year pattern is characterized by the well-developed CWM. All CWMs have a unique function to trap suspended sediment under the thermocline due to weakening tidal current and residual current there. These CWMs in the Yellow Sea (YS) and north ECS are connected together. The layer above the thermocline is characterized by diluted water with low salinity, high temperature. Suspended sediment can be transported into the Okinawa Trough and the South Korea coast during this period. A strong eddy always occur nearby the Kuroshio bend at northeast Taiwan, which has promoted the exchange between the ECS shelf and Okinawa Trough, and the development of the shelf edge current and Taiwan warm current (TWC).

  4. Community structure of archaea from deep-sea sediments of the South China Sea.

    PubMed

    Wang, Peng; Li, Tao; Hu, Anyi; Wei, Yuli; Guo, Wenting; Jiao, Nianzhi; Zhang, Chuanlun

    2010-11-01

    Using the archaeal 16S rRNA gene, we determined the community structures of archaea of subseafloor sediments (∼9-11 m below seafloor) from two geographically distant cores (MD05-2896, south, water depth 1,657 m; MD05-2902, north, water depth 3,697 m) in the South China Sea. Euryarchaeota accounted for 61.4% of total archaeal clone libraries at MD05-2896 and 56.2% at MD05-2902. At both locations, the Euryarchaeota-related sequences were dominated by Marine Benthic Group D, Terrestrial Miscellaneous Eryarchaeotal Group, and South African GoldMine Euryarchaeotal Group; the Crenarchaeota-related sequences were dominated by Marine Benthic Group B, Marine Group I, pSL12, and C3. The community structure showed no significant difference with depth at each location, suggesting the lack of stratification of archaeal populations in the deep-sea marine sediments in the South China Sea. On the other hand, the community structure is significantly different between the two sites, which may be related to geographical difference in the South China Sea.

  5. Sea-level responses to sediment transport over the last ice age cycle

    NASA Astrophysics Data System (ADS)

    Ferrier, K.; Mitrovica, J. X.

    2013-12-01

    Sea-level changes over the last ice age cycle were instrumental in steering Earth's topographic evolution. These sea-level variations were driven by changes in surface mass loads, including not only ice and ocean mass variations but also the transfer of rock from eroding mountains to sedimentary deposits. Here we use an extended numerical model of ice age sea level (Dalca et al., 2013) to explore how sediment erosion and deposition affected global sea-level variations over the last ice age cycle. The model takes histories of ice and sediment loads as inputs, and it computes gravitationally self-consistent sea level responses by accounting for the deformational, gravitational, and rotational perturbations in the Earth's viscoelastic form. In these model simulations, we use published estimates of erosion rates, sedimentation rates, and ice sheet variations to constrain sediment and ice loading since the Last Interglacial. We explore sea-level responses to several erosional and depositional scenarios, and in each we quantify the relative contributions of crustal deformation and gravitational perturbation to the computed sea-level change. We also present a case study to illustrate the effects that sediment transfer can have on sea level at the regional scale. In particular, we focus on the region surrounding the Indus River, where fluvial sediment fluxes are among the highest on Earth. Preliminary model results suggest that sediment fluxes from Asia to the ocean are large enough to produce a significant response in sea level along the northeastern coast of the Arabian Sea. Moreover, they suggest that modeled sea-level histories are sensitive to the timing and spatial distribution of sediment erosion and deposition. For instance, sediment deposition along the continental shelf - which may have been the primary site of Indus River sediment deposition during the Holocene - produces a different sea-level response than sediment deposition on the deep-sea Indus Fan, where

  6. Shallow gas in Cenozoic sediments of the Southern North Sea

    NASA Astrophysics Data System (ADS)

    Trampe, Anna F.; Lutz, Rüdiger; Franke, Dieter; Thöle, Hauke; Arfai, Jashar

    2013-04-01

    Shallow petroleum systems in the southern North Sea are known for several decades but they were not actively explored for a long time. In recent years these unconventional shallow petroleum systems are studied in greater detail and one shallow gas field (A-12) is in production in the Netherlands. Additionally, oil was encountered in Miocene sandstones in the southern Danish North Sea (Lille John well) just north of the Danish-German border. Seismic amplitude anomalies are an indication for hydrocarbons in sediments. Therefore we have mapped the occurrence of seismic amplitude anomalies in the German North Sea based on more than 25.000 km of 2D seismic data and around 4.000 km2 of 3D seismic data. Amplitude anomalies are ubiquitous phenomena in the study area. These anomalies are not only caused by hydrocarbons but also by changing lithologies e.g. peat or fluid migration. Therefore several classes of seismic anomalies, e.g. bright spots, chimneys, blanking areas and velocity pull-down were mapped. Examples for these classes were studied with AVO (amplitude variation with offset) analyses to verify the existence or non-existence of gas in the sediments. Shallow gas can be produced and transported through the dense pipeline grid of the southern and central North Sea or it could be burned offshore close to wind parks in small power plants and the electric energy then transported through the existing power connections of the wind parks. Thus enabling a continuous energy supply during calm wind periods. This study is carried out within the framework of the project "Geoscientific Potential of the German North Sea (GPDN)" in which the Cenozoic sedimentary system was mapped in great detail. A detailed model of delta evolution (Baltic river system) was developed which serves as a structural framework. The studied interval is time equivalent to the Utsira formation which is used offshore Norway for sequestration of CO2. These different possibilities of using or exploiting

  7. Climatic Atlas of the Outer Continental Shelf Waters and Coastal Regions of Alaska. Volume 2. Bering Sea. Revision

    DTIC Science & Technology

    1988-01-01

    Downsview, clouds, waves, and such supplemental informa- of potential impact by oil and gas exploration Ontario. Data summaries were made possible tion...exception of icebreakers and other specially designed ships. It makes the /1 cleanup of oil spills difficult, if not impossible, Kotlik by hampering...the operation of cleanup equip- " p LJ 172’ 170" 168" 166"* 1n 6n ment and by trapping oil under the ice. Sea ice 1 1 1 t She PointU also has

  8. Sediment sources and their contribution along northern coast of the South China Sea: Evidence from clay minerals of surface sediments

    NASA Astrophysics Data System (ADS)

    Liu, Jianguo; Yan, Wen; Chen, Zhong; Lu, Jun

    2012-09-01

    Clay minerals of surface sediment samples from nine bays/harbors along northern coast of the South China Sea (SCS) are used for sediment sources and contribution estimation in the study areas. Results reveal that sediments in the study bays/harbors seem to be a mixture of sediments from the Pearl, Hanjiang River and local islands/rivers, but their clay mineral assemblage is distinct from that of Luzon and Taiwan sediments, indicating that sediments are derived mainly from the neighboring sources through riverine input and partly from localized sediments. Due to input of local sediments in the northern SCS, sediments from both east of the Leizhou Peninsula (Area IV) and next to the Pearl River estuary (PRE, Area II) have high smectite percent. Affected by riverine input of the Pearl and Hanjiang Rivers, sediments in west of the PRE (Area III) and east of the PRE (Area I) have high illite (average 47%) and kaolinite (54%) percents, respectively. Sediment contributions of various major sources to the study areas are estimated as the following: (1) the Hanjiang River provide 95% and 84% sediments in Areas I and II, respectively, (2) the Pearl River supply 79% and 29% sediments in Areas III and IV, respectively and (3) local sediments contribute the rest and reach the maximum (˜71%) in Area IV.

  9. Effects of sediment transport and deposition on crustal loading, Earth's gravitational field, and sea level

    NASA Astrophysics Data System (ADS)

    Ferrier, K.; Mitrovica, J. X.; Perron, T.; Milne, G. A.; Wickert, A. D.

    2012-12-01

    Spatial patterns in static sea level are controlled by the interplay between the history of ice mass variations and the associated deformational, gravitational and rotational perturbations in the Earth's state. Over the last decade, there has been a renewed effort to extend classic treatments of ice-age sea-level change (Farrell and Clark, 1976) to incorporate effects such as shoreline migration due to the local onlap or offlap of seawater and changes in the extent of grounded, marine-based ice, as well as feedbacks between sea level and the orientation of Earth's rotation axis. To date, the impact of sediment transport - whether in the context of glacial processes, or other processes such as fluvial deposition - has not been incorporated into a gravitationally self-consistent sea-level theory. Here we briefly summarize the main elements of a new sea-level theory that includes sediment transport, and we apply this new theory to investigate crustal deformation and sea-level changes driven by sediment deposition on the Mississippi fan in the Gulf of Mexico. The calculations incorporate sediment transport from the start of the last glacial cycle through to the present and are constrained to conserve sediment and ocean mass. We compare relative sea level histories predicted with and without sediment transport at sites in and around the Gulf of Mexico, and we quantify the relative impacts of gravitational and deformational effects of sediment deposition. We also explore the extent to which sea-level changes associated with sediment transport impact the interpretation of paleo-sea-level records. Our new sea-level formulation provides an important component of a comprehensive coupling between sediment transfer and sea level on local, regional and global spatial scales, and on time scales extending from decades to tens of thousands of years. References: Farrell, W.E., and Clark, J.A., 1976. On postglacial sea level: Geophysical Journal of the Royal Astronomical Society, v

  10. 75 FR 81921 - Fisheries of the Exclusive Economic Zone Off Alaska; Steller Sea Lion Protection Measures for the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-29

    ... Zone Off Alaska; Steller Sea Lion Protection Measures for the Bering Sea and Aleutian Islands... Economic Zone Off Alaska; Steller Sea Lion Protection Measures for the Bering Sea and Aleutian Islands... Steller sea lion protection measures to ensure that the Bering Sea and Aleutian Islands management...

  11. Regularities of Corg distribution in bottom sediments of the Russian part of the Sea of Azov

    NASA Astrophysics Data System (ADS)

    Fedorov, Yu. A.; Dotsenko, I. V.; Kuznetsov, A. N.; Belov, A. A.; Loginov, E. A.

    2009-04-01

    The principal regularities were ascertained for the spatiotemporal distribution of organic carbon in the water and bottom sediments of the Russian part of the Sea of Azov. The relationships between allo- and autochthonous organic matter in water and bottom sediments from different parts of the sea aquatic area were found. The behavior of organic carbon in the water-bottom sediments system was characterized as the effect of the variability of hydrochemical, biological, and hydrological factors ad processes.

  12. Quality Assurance Project Plan for Verification of Sediment Ecotoxicity Assessment Ring(SEA Ring)

    EPA Science Inventory

    The objective of the verification is to test the efficacy and ability of the Sediment Ecotoxicity Assessment Ring (SEA Ring) to evaluate the toxicity of contaminants in the sediment, at the sediment-water interface, and WC to organisms that live in those respective environments.

  13. Nutrients cycling in response to opal productivity during the last 600 kyr in the Bering Sea (IODP Exp. 323 Site U1343): diatom silicon isotope and sedimentary nitrogen isotope

    NASA Astrophysics Data System (ADS)

    Kim, Sunghan; Takahashi, Kozo; Kanematsu, Yoshiyuki; Asahi, Hirofumi; Ikehara, Minoru; Khim, Boo-Keun

    2014-05-01

    Multidisciplinary paleoceanographic proxies (biogenic opal, diatom silicon isotope, and sedimentary nitrogen isotope, benthic foraminifera oxygen isotope) were analyzed for Site U1343 of IODP Exp. 323, in order to investigate the degree of nutrient utilization in response to glacial-interglacial changes of opal productivity in the Bering Sea. According to oxygen isotope of benthic foraminifera, an age model for Site U1343 represents a record of 600 ka. High diatom silicon isotope values during interglacial periods were attributed to increased opal production under nutrient-replete conditions, which would have resulted in higher silicic acid utilization along with increased diatom productivity. In contrast, low diatom silicon isotope values during glacial periods were caused by reduced opal production due to extensive sea ice. Such condition can lead to lower silicic acid utilization along with decreased diatom productivity. Thus, silicic acid cycling between subsurface and surface waters was active during interglacial periods, but weak during glacial periods. High sedimentary nitrogen isotope values generally occurred with high biogenic opal, particularly during warm (low oxygen isotope) periods, indicating higher nitrate utilization with increased diatom productivity. In contrast, low sedimentary nitrogen isotope values were found primarily in conjunction with low biogenic opal particularly during cold (high oxygen isotope) periods, reflecting lower nitrate utilization with decreased diatom productivity. Thus, nitrate cycling between subsurface and surface waters was active during warm periods and weak during cold periods. Diatom productivity at Site U1343 was significantly restricted owing to extensive sea ice during glacial/cold periods, emphasizing the important role in controlling orbital-scale nutrient utilization by diatoms in the slope area of the Bering Sea.

  14. Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

    2016-04-01

    A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

  15. Habitat quality of the coastal southeastern Bering Sea for juvenile flatfishes from the relationships between diet, body condition and prey availability

    NASA Astrophysics Data System (ADS)

    Yeung, Cynthia; Yang, Mei-Sun

    2017-01-01

    The distribution and body condition of juvenile northern rock sole (NRS), Lepidopsetta polyxystra, and yellowfin sole (YFS), Limanda aspera, were studied in relation to prey availability across the coastal shelf at the Alaska Peninsula boundary of the eastern Bering Sea (EBS) to assess spatial variability in habitat quality. Juveniles of ≤ 20 cm and adults of ≥ 30 cm total length were collected from bottom trawl catch samples at stations located 10 to 120 km from the Alaska Peninsula coast, and in bottom depths of 28 to 85 m. Stomach contents and stable isotopes of carbon and nitrogen from muscle tissue were analyzed to describe diet composition. The quantity and quality of prey did not significantly affect the distribution of juvenile NRS and YFS. Spatial mismatch between the diet composition and the infauna prey assemblage suggested that prey availability was not limiting across the area, allowing fish to select for prey, presumably to maximize net energy gain. The body condition of juvenile NRS was higher in the eastern section of the area (Bristol Bay) - where they shared spatial and dietary niches with juvenile YFS, than in the west section (Unimak Island) where juvenile YFS were largely absent. A difference in body condition suggests that habitat quality may be higher in Bristol Bay. For NRS, stomach contents and stable isotopes in muscle tissue indicated an ontogenetic diet shift from amphipods to polychaetes from juvenile to adult stages. In contrast, for YFS, amphipods seemed to remain the primary prey and polychaetes the least important prey from juvenile to adult stage. Given that the high prey availability found in this south coastal area of EBS extends to areas across the EBS shelf, favorable habitat for juvenile flatfishes should be extensive. However, much of this potential juvenile habitat is underutilized by NRS, which were mainly limited to Bristol Bay and the Alaska Peninsula, whereas YFS did extend north over 500 km from Bristol Bay along

  16. [Genetic Differentiation of Sockeye Salmon Oncorhynchus nerka from Kamchatka River Basin and the Lake-River Systems of the West Coast of the Bering Sea as Inferred from Data on Single Nucleotide Polymorphism].

    PubMed

    Khrustaleva, A M; Klovach, N V; Vedischeva, E V; Seeb, J E

    2015-10-01

    The variability of 45 single nucleotide polymorphism loci (SNP) was studied in sockeye salmon from the Kamchatka River basin and four lake-river systems of the west coast of the Bering Sea. Based on the genetic differentiation estimates for the largest sockeye salmon populations of Eastern Kamchatka and Chukotka, the examined samples were combined into two regional groups represented by the population of the Kamchatka River drainage, which included numerous local subpopulations and seasonal races, and the northern population grouping from the rivers of Olutorsko-Navarinsky raion, wherein the sockeye salmon from Maynypilginskaya Lake-River system was relatively isolated. Considerable divergence was observed between the island (Sarannoe Lake, Bering Island) and continental populations. Genetic heterogeneity was revealed and groups of early- and late-maturing individuals were isolated in the sample of late-run sockeye salmon from Kamchatka River. In Apuka River, subdivision of the spawning run into two genetically distinct spatial and temporal groupings was also observed. The results suggest that the differentiation of sockeye salmon samples by single nucleotide substitution frequencies was largely due to differences in the direction and strength of local selection at some loci in the population complexes and intrapopulation groupings from the examined river basins of Eastern Kamchatka, Chukotka, and Commander Islands.

  17. Seasonal transportation and deposition of the suspended sediments in the Bohai Sea and Yellow Sea and the related mechanisms

    NASA Astrophysics Data System (ADS)

    Qiao, Lulu; Zhong, Yi; Wang, Nan; Zhao, Ke; Huang, Lingling; Wang, Zhen

    2016-05-01

    The Yellow River is well known for high concentration of suspended particulate matter (SPM), which is one of the most important SPM sources in the Bohai Sea and Yellow Sea, China. The mechanisms of long-distance transport and deposition of the Yellow River sediment discharges are hot topics. Based on field observations in four different seasons of 2010-2011 and 15 numerical experiments, this work studied the seasonal sediment transportation and deposition in the Bohai and Yellow Seas. Results show that the horizontal distribution of suspended sediment concentration in the Bohai Sea and Yellow Sea is neither closely related to the Yellow River discharge in flood and dry seasons nor to the temperature and salinity distributions in winter and summer because most of the Yellow River-discharged sediments deposited near the river mouth. However, the winter northerly wind events, especially the winter storm events with high waves, are the major factors inducing the long-distance transport of the sediments from the Bohai Sea to the Yellow Sea. The net SPMs are transported to the Yellow Sea from the Bohai Sea in both winter and summer. The net SPM flux at the Bohai Strait is 14.0 Mt/year by the combined effects of tides, wind, and waves. The SPM is transported to the Shandong Peninsula in the Yellow Sea for the generation of the mud wedge off the peninsula. The northern part of the mud wedge is related to the southerly wind in summer, and the southeastern part resulted from the winter northerly wind, especially the strong wind.

  18. 76 FR 63204 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Yellowfin Sole in the Bering...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-12

    ... management area (BSAI). This action is necessary to allow the 2011 total allowable catch of yellowfin sole to... Zone Off Alaska; Reallocation of Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area... of the 2011 yellowfin sole total allowable catch (TAC) assigned to the Bering Sea and...

  19. 76 FR 29671 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Pacific Cod in the Bering...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-23

    ... Economic Zone Off Alaska; Reallocation of Pacific Cod in the Bering Sea and Aleutian Islands Management... meters) length overall using hook-and-line or pot gear in the Bering Sea and Aleutian Islands management area. This action is necessary to allow the 2011 total allowable catch of Pacific cod to be...

  20. 75 FR 55689 - Fisheries of the