Contribution palynostratigraphique (dinokystes, pollen et spores) à la connaissance de la mer de Champlain: coupe de Saint-Césaire, Québec

1989 ◽  
Vol 26 (12) ◽  
pp. 2450-2464 ◽  
Author(s):  
Anne de Vernal ◽  
Claire Goyette ◽  
Cyril G. Rodrigues
Keyword(s):  
High Resolution ◽  
Relative Abundance ◽  
Surface Waters ◽  
Dinoflagellate Cysts ◽  
Site Location ◽  
Morphological Variations ◽  
Forest Tundra ◽  
Arctic Conditions ◽  
Shrub Tundra ◽  
Pollen And Spores

High-resolution continental (pollen and spores) and marine (dinoflagellate cysts) microfloral records were obtained from a section consisting of about 0.5 m of glaciolacustrine and 2.5 m of Champlain Sea deposits at the Saint-Césaire site. The pollen and spore assemblages indicate the existence of a regional open vegetation of shrub tundra to forest tundra. Fluctuations in the percentages of Picea and shrub and herb taxa are related to regional afforestation and paleogeographical evolution of the basin. The Champlain Sea sediments contain an abundant dinocyst flora dominated by Operculodinium centrocarpum, Brigantedinium spp., and Algidasphaeridium? minutum, which indicate cold Arctic conditions in surface waters. Fluctuations in concentration (102–104∙cm−3) and relative abundance of dinocyst species are attributed to changes in dinoflagellate productivity and paleoceanographic conditions, notably paleosalinity. Morphological variations of Operculodinium centrocarpum and Algidasphaeridium? minutum led to this description of the varieties, named "cezare" after the site location.

Postglacial paleoceanography of Hudson Bay: stratigraphic, microfaunal, and palynological evidence

1990 ◽  
Vol 27 (7) ◽  
pp. 946-963 ◽  
Author(s):  
Guy Bilodeau ◽  
Anne de Vernal ◽  
Claude Hillaire-Marcel ◽  
Heiner Josenhans
Keyword(s):  
Surface Waters ◽  
Latitudinal Gradient ◽  
Water Mass ◽  
Water Masses ◽  
Hudson Bay ◽  
Marine Invasion ◽  
Arctic Conditions ◽  
Pollen And Spores ◽  
Abundance And Diversity ◽  
Lake Ojibway

Cores containing representative sequences of postglacial sediments in northern and southern Hudson Bay were analyzed for their microfaunal (foraminifers and ostracods) and palynological (dinocysts, pollen, and spores) content in order to reconstruct the evolution of environments since the last glaciation.In southern Hudson Bay, the marine invasion of the Tyrrell Sea at ca. 8000 BP, following the Lake Ojibway episode, was accompanied by the development of an Arctic-type microflora and microfauna indicative of a dense seasonal sea-ice cover and stratified water masses. Shortly after 8000 BP, the establishment of subarctic conditions in surface waters was accompanied by more intense homogenization of water masses. Subarctic conditions have persisted throughout most of the postglacial interval despite a recent surface-water cooling.In northern Hudson Bay, micropaleontological and lithological data reveal a succession of proximal to distal glaciomarine environments characterized by low biogenic productivity, harsh Arctic conditions, and stratified water masses. An increase in dinocyst abundance and diversity, after 6000 BP, indicates the establishment of cool subarctic conditions in surface waters, while foraminifer assemblages suggest intensified mixing of water masses.The micropaleontological records of northern and southern Hudson Bay reveal a strong latitudinal gradient in biogenic productivity and water mass characteristics throughout the postglacial interval. "Interglacial" conditions, established in southern Hudson Bay very shortly after it was invaded by the sea, seem to have occurred much later in northern Hudson Bay.

scholarly journals High Resolution pH Measurements Using a Lab-on-Chip Sensor in Surface Waters of Northwest European Shelf Seas

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2622 ◽  
Author(s):  
Victoire Rérolle ◽  
Eric Achterberg ◽  
Mariana Ribas-Ribas ◽  
Vassilis Kitidis ◽  
Ian Brown ◽  
...  
Keyword(s):  
High Resolution ◽  
Surface Waters ◽  
Ph Sensor ◽  
Ph Measurements ◽  
Lab On Chip ◽  
European Shelf ◽  
Shelf Seas ◽  
On Chip ◽  
Chemistry Dynamics ◽  
Northwest European Shelf

Increasing atmospheric CO2 concentrations are resulting in a reduction in seawater pH, with potential detrimental consequences for marine organisms. Improved efforts are required to monitor the anthropogenically driven pH decrease in the context of natural pH variations. We present here a high resolution surface water pH data set obtained in summer 2011 in North West European Shelf Seas. The aim of our paper is to demonstrate the successful deployment of the pH sensor, and discuss the carbonate chemistry dynamics of surface waters of Northwest European Shelf Seas using pH and ancillary data. The pH measurements were undertaken using spectrophotometry with a Lab-on-Chip pH sensor connected to the underway seawater supply of the ship. The main processes controlling the pH distribution along the ship’s transect, and their relative importance, were determined using a statistical approach. The pH sensor allowed 10 measurements h−1 with a precision of 0.001 pH units and a good agreement with pH calculated from a pair of discretely sampled carbonate variables dissolved inorganic carbon (DIC), total alkalinity (TA) and partial pressure of CO2 (pCO2) (e.g., pHDICpCO2). For this summer cruise, the biological activity formed the main control on the pH distribution along the cruise transect. This study highlights the importance of high quality and high resolution pH measurements for the assessment of carbonate chemistry dynamics in marine waters.

High resolution monitoring of dissolved Cu and Co in coastal surface waters of the Western North Sea

2003 ◽  
Vol 23 (6) ◽  
pp. 611-623 ◽  
Author(s):  
Eric P. Achterberg ◽  
Constant M.G. van den Berg ◽  
Carlo Colombo
Keyword(s):  
High Resolution ◽  
North Sea ◽  
Surface Waters

The Holocene evolution of permafrost near the tree line, on the eastern coast of Hudson Bay (northern Quebec)

1987 ◽  
Vol 24 (11) ◽  
pp. 2206-2222 ◽  
Author(s):  
Michel Allard ◽  
Maurice K. Seguin
Keyword(s):  
Climatic Conditions ◽  
Snow Accumulation ◽  
Eastern Coast ◽  
Permafrost Degradation ◽  
Tree Line ◽  
Stratigraphic Sequence ◽  
Forest Tundra ◽  
Discontinuous Permafrost ◽  
Shrub Tundra ◽  
Peat Plateaus

Permafrost evolution in postglacial marine silts near the tree line was reconstructed using landform analysis, 14C dating, and palynostratigraphic analysis of peat sections. In the forest–tundra, below the tree line, four sites in peat plateaus have a stratigraphic sequence indicating an alluvial plain environment from 6000 to 4800 BP followed by a wetland supporting trees and shrubs with deep snow accumulation and without permafrost. Ground heave occurred between 1900 and 1200 BP as peat plateaus and palsas were formed. In the shrub–tundra, above the tree line, three permafrost sites with buried peat beds suggest that climatic conditions were cold enough for discontinuous permafrost in the surrounding landscape starting from land emergence, about 5800 BP; however, fen expansion and sedge peat accumulation continued over unfrozen ground until 2300, 1560, and 1400 BP. At these dates, the sites were buried with silt, probably as a result of mass wasting on nearby permafrost mounds and then permafrost aggraded under the sites. Generally, the palynostratigraphic data reflect a marked cooling of climate starting by 3200–2700 BP and culminating in a major period of permafrost aggradation between 1900 and 1200 BP. Permafrost degradation has been dominant since then despite other possible cold intervals. Nowadays, the permafrost in marine silts is twice as thick and three times more widespread in the shrub–tundra than in the forest–tundra.

Contrasting climate- and land-use-driven tree encroachment patterns of subarctic tundra in northern Norway and the Kola PeninsulaThis article is a contribution to the series Tree recruitment, growth, and distribution at the circumpolar forest–tundra transition.

2011 ◽  
Vol 41 (3) ◽  
pp. 437-449 ◽  
Author(s):  
Sigrun Aune ◽  
Annika Hofgaard ◽  
Lars Söderström
Keyword(s):  
Mountain Birch ◽  
Response Patterns ◽  
Reindeer Herding ◽  
Forest Tundra ◽  
Tree Encroachment ◽  
Arctic Conditions ◽  
Sapling Survival ◽  
Betula Pubescens Ehrh ◽  
Different Response ◽  
Biotic Control

High-latitude regions are experiencing substantial climate change, and the forest–tundra transition is assumed to sensitively track these changes through advancing treeline and increased tundra encroachment. However, herbivores may influence these responses. The present study addresses, through analyses of age structures, growth characteristics, and climate correspondence, how mountain birch (Betula pubescens Ehrh. ssp. czerepanovii (Orlova) Hämet-Ahti) treelines and sapling cohorts beyond the treeline have responded to the last decade’s warming in six North European subarctic areas with different climate and grazing characters. The results show different response patterns among areas representing advancing, stationary, and possibly retreating treelines. Recruitment was abundant over the last decades in all areas except one, with predominantly arctic conditions, where both tree and sapling cohorts were old. Areas with high annual precipitation show advancing birch populations characterized by young individuals and partly overlapping tree and sapling age distributions. Areas in reindeer herding districts show stationary or retreating birch populations characterized by nonoverlapping age distributions and low sapling survival. Recruitment patterns beyond the treeline generally corresponded with non-growing-season climate variables, mainly precipitation, indicating the importance of a protecting snow cover. The results highlight the important interplay between abiotic and biotic control over tundra encroachment and treeline dynamics and the importance of multisite studies when addressing responses to warming.

Pollen Analysis of the 1973 Ice Core from Devon Island Glacier, Canada

1984 ◽  
Vol 22 (1) ◽  
pp. 68-76 ◽  
Author(s):  
John H. McAndrews
Keyword(s):  
Late Holocene ◽  
Ice Core ◽  
Ice Sheet ◽  
Early Holocene ◽  
The Arctic ◽  
Devon Island ◽  
Glacier Ice ◽  
Shrub Tundra ◽  
Low Arctic ◽  
Pollen And Spores

Meltwater from a 299-m-long ice core was filtered and analyzed for fossil pollen and spores. Pollen concentration was higher in the late Holocene and interglacial intervals (ca. 7 liter−1) than in the early Holocene and Wisconsinan (ca. 1–2 liter−1) ones. The late Holocene and interglacial assemblages were dominated by Alnus (alder), whereas the early Holocene and Wisconsinan ones were dominated by Betula (birch) and Artemisia (sage). During the Holocene and probably the last interglaciation, most of the pollen and spores were blown a minimum of 1000 km from low arctic shrub tundra and adjacent subarctic Picea (spruce) forest; these areas were dominated by the arctic air mass during the summer pollinating season. During the Wisconsinan-early Holocene, glacier ice and arctic air were more widespread and pollen sources were more distant; thus, at this time relatively little pollen was incorporated into the ice.The Devon ice-core data suggest that there should have been pollen in the continental ice sheet of Wisconsin time. When the ice sheet retreated this pollen would be carried by meltwater and redeposited with silt and clay together with contemporary pollen, producing an ecologically anomalous assemblage.

scholarly journals Distribution of Yellow Wagtail Forms Motacilla flava – Complex in the North of Western Siberia, Russia

2017 ◽  
Vol 10 (1) ◽  
pp. 1-9
Author(s):  
Mikhail G. Golovatin ◽  
Vasiliy A. Sokolov
Keyword(s):  
Western Siberia ◽  
Northern Taiga ◽  
Yamal Peninsula ◽  
Yellow Wagtail ◽  
Forest Tundra ◽  
Ob River ◽  
North East ◽  
The North ◽  
Taiga Forest ◽  
Shrub Tundra

On the basis of the materials obtained from the studies carried out from 2000 to 2015, we present the data on distribution of the Yellow Wagtail forms in the north of Western Siberia, i.e. within the overlapping boundaries of the ranges of a complex set of several polytypical forms – Motacilla flava sensu lato. Four forms have been identified here: two forms from the group of Western Yellow Wagtails (M. f. thunbergi and M. f. beema & flava) and two forms from the group of Eastern Yellow Wagtails (M. t. plexa and M. t. tschutschensis). Western “black-headed” form M. f. thunbergi is spread in the area of the northern taiga, forest tundra and south shrub tundra within the Ob River basin, while eastern “black-headed” form M. t. plexa is found in the shrubby tundra and further to the east from the Ob River in forest tundra and northern taiga. Western “light headed” wagtails M. f. beema & flava spread as far as 65º05'N along the floodplain of the Ob River. Eastern “light-headed” wagtail M. t. tschutschensis penetrates the Taz peninsula and, through the anthropogenic sites, the north-east coast of the Yamal Peninsula, i.e. the Sabetta area as far as 71º14'N. The entire range of the Yellow Wagtail is characterized by the interchange of zones inhabited by “black-headed” (without the expressed eyebrows on males) and “light-headed” (with notable eyebrows on males or white-headed) forms from the north to the south.

scholarly journals Coupling physics and biogeochemistry thanks to high resolution observations of the phytoplankton community structure in the North-Western Mediterranean Sea

2017 ◽  
Author(s):  
Pierre Marrec ◽  
Andrea M. Doglioli ◽  
Gérald Grégori ◽  
Mathilde Dugenne ◽  
Alice Della Penna ◽  
...  
Keyword(s):  
High Resolution ◽  
Surface Waters ◽  
Phytoplankton Community ◽  
Western Mediterranean ◽  
Fine Scale ◽  
Phytoplankton Community Structure ◽  
The North ◽  
Cold Core ◽  
North Western

Abstract. Fine-scale physical structures and ocean dynamics strongly influence and regulate biogeochemical and ecological processes. These processes are particularly challenging to describe and understand because of their ephemeral nature. The OSCAHR (Observing Submesoscale Coupling At High Resolution) campaign has been conducted in fall 2015 in which, a fine-scale structure in the North Western Mediterranean Ligurian subbasin was pre-identified using both satellite and numerical modeling data. Along the ship track, various variables were measured at the surface (temperature, salinity, chlorophyll-a and nutrients concentrations) with ADCP current velocity. We also deployed a new model of CytoSense automated flow cytometer (AFCM) optimized for small and dim cells, for near real-time characterization of surface phytoplankton community structure of surface waters with a spatial resolution of few km and a hourly temporal resolution. For the first time with this type of AFCM we were able to resolve Prochlorococcus and Synechococcus picocyanobacteria. The vertical physical dynamics and biogeochemical properties of the studied area were investigated by continuous high resolution CTD profiles thanks to a moving vessel profiler (MVP) during the vessel underway associated to a 1-m vertical resolution pumping system deployed during fixed stations. The observed fine-scale feature presented a cyclonic structure with a relatively cold core surrounded by warmer waters. Surface waters were totally depleted in nitrate and phosphate. In addition to the doming of the isopycnals by the cyclonic circulation, an intense wind event induced Ekman pumping. The upwelled subsurface cold nutrient-rich water fertilized surface waters, characterized by an increase in Chl-a concentration. Prochlorococcus, pico- and nano-eukaryotes were more abundant in cold core waters while Synechococcus dominated in warm boundary waters. Nanoeukaryote were the main contributors (> 50 %) in terms of pigment content (FLR) and biomass. Biological observations based on the mean cell's red fluorescence recorded by AFCM combined with physical properties of surface waters suggest a distinct origin for two warm boundary waters. Finally, the application of a matrix growth population model based on high-frequency AFCM measurements in warm boundary surface waters provides estimates of in-situ growth rate and apparent net primary production for Prochlorococcus (μ = 0.21 d−1, NPP = 0.11 mgC m−3 d−1) and Synechococcus (μ = 0.72 d−1, NPP = 2.68 mgC m−3 d−1), which corroborate their opposite surface distribution pattern. The innovative adaptive strategy applied during OSCAHR with a combination of several multidisciplinary and complementary approaches involving high-resolution in-situ observations and sampling, remote-sensing and model simulations provided a deeper understanding of the marine biogeochemical dynamics through the first trophic levels.

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