Identification of 0- and 1-group redfish (genus Sebastes) using electrophoresis     

Nedreaas  Kjell; Naevdal  Gunnar 《ICES Journal of Marine Science》1991,48(1):91-99

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Spatial variation in abundance, size composition and viable egg production of spawning cod (Gadus morhua L.) in Icelandic waters     

Marteinsdottir  Gudrun; Gudmundsdottir  Asta; Thorsteinsson  Vilhjalmur; Stefansson  Gunnar 《ICES Journal of Marine Science》2000,57(4):824-830

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A fungal epizootic in mussels at a deep-sea hydrothermal vent   总被引：1，自引：0，他引：1  

Cindy Lee Van Dover  Megan E. Ward  Joseph L. Scott  Jamie Underdown  Brooke Anderson  Christina Gustafson  Matthew Whalen  & Ryan B. Carnegie 《Marine Ecology》2007,28(1):54-62

Mass mortalities due to disease are important determinants of population and community structure in marine ecosystems, but the speed at which an epizootic may sweep through a population, combined with rapid selection for disease‐resistant stocks, can mask the ecological impact of disease in all but the most closely monitored populations. We document an emergent epizootic event in the deep sea that is occurring in mussels (Bathymodiolus brevior) at the Mussel Hill hydrothermal vent in Fiji Basin and we identify the causal agent as a black yeast (order Chaetothyriales) that elicits a pronounced host immune response and is associated with tissue deterioration. The yeast was not observed in other invertebrate taxa (the gastropods Ifremeria nautilei, Alviniconcha aff. hessleri; the limpets Lepetodrilus schrolli, Symmetromphalus aff. hageni; the polychaetes Branchipolynoe pettiboneae, Amphisamytha cf. galapagensis) associated with the mussel bed, nor in mussels (Bathymodiolus brevior) collected from adjacent Lau Basin mussel beds. Massive mussel mortality resulting from the fungal infection is anticipated at the Mussel Hill site in Fiji Basin; we expect that epizootic outbreaks in dense invertebrate communities have the potential to be major determinants of community structure in deep‐sea chemosynthetic ecosystems. The possibility that submersible assets may serve as vectors for transport of the fungus warrants further attention.  相似文献   

Statistical testing of a new testate amoeba‐based transfer function for water‐table depth reconstruction on ombrotrophic peatlands in north‐eastern Canada and Maine,United States     

Matthew J. Amesbury  Gunnar Mallon  Dan J. Charman  Paul D. M. Hughes  Robert K. Booth  Timothy J. Daley  Michelle Garneau 《第四纪科学杂志》2013,28(1):27-39

Proxy reconstructions of climatic parameters developed using transfer functions are central to the testing of many palaeoclimatic hypotheses on Holocene timescales. However, recent work shows that the mathematical models underpinning many existing transfer functions are susceptible to spatial autocorrelation, clustered training set design and the uneven sampling of environmental gradients. This may result in over‐optimistic performance statistics or, in extreme cases, a lack of predictive power. A new testate amoeba‐based transfer function is presented that fully incorporates the new recommended statistical tests to address these issues. Leave‐one‐out cross‐validation, the most commonly applied method in recent studies to assess model performance, produced over‐optimistic performance statistics for all models tested. However, the preferred model, developed using weighted averaging with tolerance downweighting, retained a predictive capacity equivalent to other published models even when less optimistic performance statistics were chosen. Application of the new statistical tests in the development of transfer functions provides a more thorough assessment of performance and greater confidence in reconstructions based on them. Only when the wider research community have sufficient confidence in transfer function‐based proxy reconstructions will they be commonly used in data comparison and palaeoclimate modelling studies of broader scientific relevance. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Groundwater isoscapes in a montane headwater catchment show dominance of well‐mixed storage          下载免费PDF全文

Bernhard Scheliga  Doerthe Tetzlaff  Gunnar Nuetzmann  Chris Soulsby 《水文研究》2017,31(20):3504-3519

We conducted an integrated groundwater–surface water monitoring programme in a 3.2‐km² experimental catchment in the Scottish Highlands by sampling all springs, seepages, and wells in six, spatially extensive synoptic surveys over a 2‐year period. The catchment has been glaciated, with steep hillslopes and a flat valley bottom. There is around 70% glacial drift cover in lower areas. The solid geology, which outcrops at higher elevations, is granite and metamorphic schist. The springs and seepages generally occur at the contact between the solid geology and drift or at breaks of slopes in the valley bottom. Samples were analysed for stable isotopes, Gran alkalinity and electrical conductivity. Despite the surveys encompassing markedly different antecedent conditions, the isotopic composition of groundwater at each location exhibited limited temporal variability, resulting in a remarkable persistence of spatial patterns indicating well‐mixed shallow, groundwater stores. Moreover, line‐conditioned excess values derived from the isotope data indicated no evidence of fractionation affecting the groundwater, which suggests that most recharge occurs in winter. The alkalinity and electrical conductivity of groundwater reflected geological differences in the catchment, being highest where more weatherable calcareous rocks outcrop at higher altitudes in the catchment. Springs draining these areas also had the most variable isotope composition, which indicated that they have shorter residence times than the drift covered part of the catchment. The study showed that even in geologically heterogeneous upland catchments, groundwater can be characterized by a consistent isotopic composition, reflecting rapid mixing in the recharge zone. Our work, thus, emphasizes the critical role of groundwater in upland catchments and provides tracer data that can help constrain quantitative groundwater models.  相似文献   

The Iceland 1986 GPS geodetic survey: tectonic goals and data processing results     

G. R. Foulger  G. Beutler  Roger Bilham  Pall Einarsson  S. Fankhauser  W. Gurtner  U. Hugentobler  W. Jason Morgan  M. Rothacher  Gunnar Thorbergsson  U. Wild 《Journal of Geodesy》1993,67(3):148-172

Summary The 1986 GPS survey of Iceland aimed to: (1) establish geodetic control in the South Iceland Seismic Zone (SISZ), to study destructive earthquakes there, (2) measure a country-wide network to form the basis of a new first order national network. 51 points were surveyed, with 20–30 km spacings within the SISZ and 100 km spacings elsewhere. The data were processed using the Bernese GPS software Version 3. Analysis was difficult due to poor satellite geometry and short-period ionospheric variations. However, an ambiguity-fixed, ionosphere-free solution gave accuracies of 1–2 cm in the horizontal and 2–3 cm in the vertical for the SISZ network and an ambiguity-free, ionosphere-free solution yielded accuracies of about 5 cm for the country-wide network. An ionosphere-free solution for the total survey with ambiguities fixed for the SISZ network only gave marginal additional improvements over the two separate solutions. GPS surveying has continued annually in Iceland with measurements in South Iceland in 1989 and 1992 (Hackman 1991; Sigmundsson 1992) and in North Iceland in 1987, 1990 and 1992 (Jahn et al. 1992; Foulger et al. 1992).  相似文献   

Environmental policy and regulation for oil exploration and shipping activities in the Barents Sea     

Gunnar Futs  ter 《Marine pollution bulletin》1994,29(6-12):348-353

The Barents Sea has one of the highest levels of biological production of all the world's oceans, and holds some of the largest fish stocks and concentrations of seabirds. Environmental conditions in the area make it particularly vulnerable to damage from human activities. Given the vulnerability of this ecosystem to the effects of human activity, and the fact that physical factors (e.g. reduced visibility, ice) increase risks due to oil exploitation and shipping activities, environmental authorities will work towards more stringent discharge limits and higher standards for emergency preparedness for both oil exploitation and shipping in the Barents Sea. The Norwegian Pollution Control Authority gives priority to preventive measures that can lower the probability of accidents and particular emphasis will be given to conditions attached to production licences and controls on activities in areas that have not yet been opened for petroleum activities. Within the Arctic Environmental Protection Strategy (the Rovaniemi-process), Norway has proposed that efforts should be made to improve the protection of Arctic marine areas, and further that a working group including representatives of all the Arctic countries should assess various legal instruments and possible measures, and make recommendations for action. Currently, no special international requirements apply to ships sailing in ice-infested waters, and the recommendations from the working group will therefore be of great importance in protecting the area from damage from shipping.  相似文献   

Geothermal energy,resources, production,stimulation | Paul Kruger and Carel Otte (Editors). Stanford Univ. Press,Stanford, Calif., 1973, 360 pp., U.S. $17.50     

Gunnar Bodvarsson 《Engineering Geology》1975,9(1):94-95

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A long-term record of photosynthetically available radiation (PAR) and total solar energy at 38.6°N, 78.2°W     

Thomas?R.?FisherEmail author  Anne?B.?Gustafson  Gregory?M.?Radcliffe  Karen?L.?Sundberg  J.?Court?Stevenson 《Estuaries and Coasts》2003,26(6):1450-1460

Photosynthetically available radiation (PAR; 400–700 nm, E m⁻² d⁻¹) is the fraction of the total solar energy (Mjoules m⁻² d⁻¹) that is used by organisms for photosynthesis and vision. We present a statistical summary of a 17-yr time series of PAR data (1982–1998) collected near Chesapeake Bay as well as a second set of data on PAR and total solar energy gathered over a shorter time span (1997–1998). The time series data (5,126 daily totals) varied between 1–67 E m⁻² d⁻¹ and were used to estimate the minimum and maximum values of PAR as a function of day of the year. In monthly frequency distributions of the PAR data, three modes were observed corresponding to sunny, partly cloudy, and overcast days. The second set of PAR and total solar energy data were used to examine the ratio of PAR to total solar energy, which was 2.04 E Mjoule⁻¹ for PAR between 10 and 70 E m⁻² d⁻¹. On overcast days, the ratio increased to as high as 3 E Mjoule⁻¹ as PAR increased in importance as a fraction of the total solar energy. These values were consistent with others in the literature, and the relationships reported here can be used to predict the climatology of PAR and total solar energy within the Chesapeake region. The PAR data were also combined with reported minimum values of PAR for net primary production in the surface mixed layer of the water column of aquatic systems to estimate the combinations of mixed layer depth and diffuse attenuation coefficient (number of optical depths) under which light limitation of phytoplankton primary production is expected to occur.  相似文献   

Modelling of uranium and neptunium chemistry in a deep rock environment     

Iréne Lundén  Karin Andersson  Gunnar Skarnemark 《Aquatic Geochemistry》1996,2(4):345-358

According to the present concept for final storage of spent nuclear fuel in Sweden, the spent fuel, encapsulated in copper or copper/steel canisters, will be placed in tunnels in a deep rock formation. The canisters will be surrounded by compacted bentonite clay acting as a buffer material. In connection with a safety analysis of such a storage facility, the total solubility of certain elements (e.g., uranium) as well as the transport properties (e.g., retardation due to sorption on mineral surfaces) of the long-lived radionuclides released from the canister have to be predicted or measured. The chemical conditions, governing the solubility and speciation of trace elements encountered in and around the repository depend on interactions between the ground water and the engineering materials in the repository and a production of oxidants due to radiolysis in the spent fuel. In the present study the speciation and solubility of uranium and neptunium in a bentonite-ground water system and in ground waters with compositions measured at a site at äspö, SE Sweden, have been calculated. The calculations have been carried out using a recent version of the geochemical computer code PHREEQE and the database HATCHES 5.0. Predictions of the uranium and neptunium concentrations in the ground water in the vicinity of a damaged high level waste repository have also been performed. The uranium concentration in the water in the bentonite barrier is predicted to be of the same order of magnitude or lower than that found in some granitic ground waters. For neptunium the calculations are uncertain due to the small amount of experimentally determined thermodynamic data and few verifications under the conditions (pH - Eh - carbonate concentration) considered. The predicted concentrations (ca 10^–12 m, corresponds to ca 0.006 Bq/l) may be regarded as high, considering the high toxicity of neptunium and its long half-life.  相似文献