Biological productivity enhancement over a continental shelf break (Bay of Biscay, NE Atlantic) evidenced by mesozooplankton aspartate transcarbamylase activity     

Jean-Pierre Bergeron  Noussith?? Koueta 《Journal of Oceanography》2011,67(2):249-252

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Local versus regional processes: can soil characteristics overcome climate and fire regimes by modifying vegetation trajectories?     

Aurélie Genries  Walter Finsinger  Hans Asnong  Yves Bergeron  Christopher Carcaillet  Michelle Garneau  Christelle Hély  Adam A. Ali 《第四纪科学杂志》2012,27(7):745-756

We analysed charcoal and pollen from sediments obtained from two lakes in the northwestern mixed‐wood Canadian boreal forest in order to reconstruct fire‐return intervals and vegetation dynamics over the last 8000 years. Sites were selected with contrasting soil properties (mesic versus dry‐sandy soils), allowing an estimation of the potential influence of soils on long‐term vegetation and fire dynamics. The sites likely experienced fewer fires during the period extending from 8000 to 4000 cal. a BP than over the last 4000 years. At both sites, eastern white pine (Pinus strobus) populations were most extensive shortly after deglaciation, with vegetation later shifting towards mixed woodlands with less P. strobus and more extensive Picea and Pinus banksiana populations. This gradual vegetation shift was probably induced by the establishment of colder and moister conditions along with a fire‐regime change. In spite of the parallel long‐term vegetation trajectories, vegetation composition differed between the two sites in both the past and present. Whereas Picea was more abundant at the mesic site, the fire‐adapted P. banksiana populations were more extensive at the sandy‐soil site. These differences in vegetation composition indicate that, in addition to climate changes and fire occurrence, soil properties also influenced vegetation dynamics. A likely increase in fire frequency in the Canadian boreal forest during the 21st century might therefore favour the expansion of these two disturbance‐adapted trees with spatial heterogeneity in the populations due to varying soil types. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Physicochemical conditions and timing of rodingite formation: evidence from rodingite-hosted fluid inclusions in the JM Asbestos mine,Asbestos, Québec     

Charles Normand  Anthony E Williams-Jones 《Geochemical transactions》2007,8(1):11

Fluid inclusions and geological relationships indicate that rodingite formation in the Asbestos ophiolite, Québec, occurred in two, or possibly three, separate episodes during thrusting of the ophiolite onto the Laurentian margin, and that it involved three fluids. The first episode of rodingitization, which affected diorite, occurred at temperatures of between 290 and 360°C and pressures of 2.5 to 4.5 kbar, and the second episode, which affected granite and slate, occurred at temperatures of between 325 and 400°C and pressures less than 3 kbar. The fluids responsible for these episodes of alteration were moderately to strongly saline (~1.5 to 6.3 m eq. NaCl), rich in divalent cations and contained appreciable methane. A possible third episode of alteration is suggested by primary fluid inclusions in vesuvianite-rich bodies and secondary inclusions in other types of rodingite, with significantly lower trapping temperatures, salinity and methane content. The association of the aqueous fluids with hydrocarbon-rich fluids containing CH₄ and higher order alkanes, but no CO₂, suggests strongly that the former originated from the serpentinites. The similarities in the composition of the fluids in all rock types indicate that the ophiolite had already been thrust onto the slates when rodingitization occurred.  相似文献   

Multicentury reconstruction of the Canadian Drought Code from eastern Canada and its relationship with paleoclimatic indices of atmospheric circulation   总被引：1，自引：0，他引：1  

M-P.?GirardinEmail author  J.?Tardif  M.?D.?Flannigan  Y.?Bergeron 《Climate Dynamics》2004,23(2):99-115

Inter-annual and -decadal scale variability in drought over the Abitibi Plains ecoregion (eastern Canada) was investigated using a 380-year dendroclimatic reconstruction of the Canadian Drought Code (CDC; July monthly average) i.e., a daily numerical rating of the average moisture content of deep organic layers. Spectral analyses conducted on the reconstructed CDC indicated a shift in spectral power after 1850 leading toward a reduction in interdecadal variability and an increase in interannual variability. Investigation on the causes for this shift suggested a decrease in North Pacific forcing after the mid-nineteenth century. Cross-continuous wavelet transformation analyses indicated coherency in the 8–16 and 17–32-year per cycle oscillation bands between the CDC reconstruction and the Pacific Decadal Oscillation (PDO) prior to 1850. Following 1850, the coherency shifted toward the North Atlantic Oscillation (NAO). Principal component analysis conducted over varying time windows reaffirmed that the Pacific forcing was restricted to the period about 1750–1850. Prior to and after this period, the CDC was correlated with the NAO. The shift around 1850 could reflect a northward displacement of the polar jet stream induced by a warming of the sea surface temperature along the North Pacific coast. A northward displacement of the jet stream, which inhibits the outflow of cold and dry Arctic air, could have allowed the incursion of air masses from the Atlantic subtropical regions.  相似文献   

Determining how the pelagic ecosystem over the continental shelf of the Bay of Biscay (NE Atlantic) functions: An approach using mesozooplankton enzyme activities as descriptors     

Jean-Pierre Bergeron  Daniel Delmas  Noussithé Koueta 《Estuarine, Coastal and Shelf Science》2009

A fisheries research cruise conducted in 2000 offered a first opportunity to take simultaneous measurements of the activities of three enzymes in mesozooplankton samples collected at a regional scale over the continental shelf of the Bay of Biscay in the NE Atlantic, with the aim of characterizing main aspects of the functioning of the biotic environment of small pelagic fish populations. The activity of the digestive endopeptidase trypsin was selected to characterize the assimilation rate of proteins, whereas pyruvate kinase (PK) was chosen as an indicator of carbohydrate assimilation and aspartate transcarbamylase (ATC) provided an overall assessment of mesozooplankton productivity. The Bay of Biscay region is subject to various strong physical driving forces that directly affect the primary structure of the pelagic food web. On our cruise, the phytoplankton biomass distribution reflected these different physical influences: diatoms dominated the nutrient-enriched coastal water; picoplankton dominated the northern-central part where nutrients were depleted; and nanoplankton were abundant at the shelf break where internal waves provided an input of nutrients. These and other results (on bacteria, particulate organic carbon distribution, among others) illustrate the differences that exist in the microbial food webs of different sectors of the bay. The living matter produced was characterized by the quality and quantity of the smallest prey items that were available to higher trophic levels. Variations in mesozooplankton enzyme activities may agree well not only with classically expected results, but also present unexpected special features: high ATC specific activities were measured around the mouth of the Gironde, in the nutrient-rich desalted water of the plume, but surprisingly not in front of the Loire river. PK specific activities reflected preponderantly the balance between phytoplankton cells sizes and the related bacterial abundance resulting from nutrient limitation (mainly P), that induces varying carbohydrates production potential. Trypsin specific activities were moderately variable, except in a restricted area where a highly abundant protein content characterized the particulate matter and in the plume of water flowing out of the Gironde. It is concluded that the presented approach of the metabolism of mesozooplankton communities may provide novel views on crucial processes occurring at the mesoscale, which fits in generally well with the scales of ecological factors mostly influential on small pelagic fish populations.  相似文献   

Numerical model of a mussel longline system: Coupled dynamics     

W. Raman-Nair  B. Colbourne  M. Gagnon  P. Bergeron 《Ocean Engineering》2008,35(13):1372-1380

The longline is modelled using lumped masses and tension-only springs including structural damping. The mussel culture is modelled as cylinders attached to the main line and the equations are formulated for the coupled dynamics of the main line, buoys and mussel socks using Kane's formalism. Surface waves are described by Stokes’ second-order wave theory. The hydrodynamic loads are applied via a Morison's equation approach using the instantaneous relative velocities and accelerations between the fluid field, the longline and the attached buoys and mussel masses. The algorithm is presented and the equations are solved using the Runge–Kutta routine “ode45” in MATLAB. Outputs include position, orientation and velocity of all components and tension in all line segments. The numerical model may be used to predict the dynamics of longline systems using drag coefficients determined from field measurements. We expect that the results will be useful for checking and optimizing shellfish aquaculture designs prior to installation and for modifying existing designs to safeguard against failure.  相似文献   

Comparing fire-history interpretations based on area, number and estimated volume of macroscopic charcoal in lake sediments     

Adam A. Ali  Philip E. Higuera  Yves Bergeron  Christopher Carcaillet   《Quaternary Research》2009,72(3):462-468

Sedimentary charcoal particles from lakes are commonly used to investigate fire history. Fire-history reconstructions are based on measuring the surface area or counting the number of charcoal fragments in adjacent samples. Recently, the volume of charcoal particles was advised as a more accurate method for quantifying past charcoal production. Large charcoal datasets, used to synthesize global fire history, include these different types of charcoal measurements and implicitly assume that they provide comparable fire-history information. However, no study has demonstrated that this assumption is valid. Here we compare fire-frequency reconstructions based on measurements of charcoal area and number, and estimates of charcoal volume from two lake sediment records from the eastern Canadian boreal forest. Results indicate that the three proxies provide comparable fire-history interpretations when using a locally defined threshold to identify fire events.  相似文献   

The missing metals problem – III. How many metals are expelled from galaxies?     

Nicolas Bouché  Matthew D. Lehnert  Anthony Aguirre  Céline Péroux  Jacqueline Bergeron 《Monthly notices of the Royal Astronomical Society》2007,378(2):525-540

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The deep structure of Gorringe Bank (NE Atlantic) and its surrounding area     

Andrée Bergeron  Jean Bonnin 《Geophysical Journal International》1991,105(2):491-502

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Observation of a variable,ZZ Ceti white dwarf: GD154     

B. Pfeiffer  G. Vauclair  N. Dolez  M. Chevreton  J. R. Fremy  G. Herpe  M. Barstow  S. J. Kleinman  T. K. Watson  J. A. Belmonte  S. O Kepler  A. Kanaan  O. Giovannini  R. E. Nather  D. E. Winget  J. Provencal  J. C. Clemens  P. Bradley  J. Dixson  A. D. Grauer  G. Fontaine  P. Bergeron  F. Wesemael  C. F. Claver  T. Matzeh  E. Leibowitz  P. Moskalik 《Astrophysics and Space Science》1993,210(1-2):201-204

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