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This study provides a general description and mapping of hemi-arctic subzones and ecoclimatic regions lying between Hudson Bay and Ungava Bay in Nouveau-Québec. Dis-tinctive distributions of dominant tree species (white spruce, black spruce and tamarack) and also of the main coniferous formations were mapped in order to provide ecological subdivisions of this territory. Data suggest that present and historical climatic factors are responsible for the nature and the specific pattern of the proposed ecological limits.

Keywords: Limites écologiques, Hémi-arctique, toundra forestière, espèces conifériennes, Nouveau-Québec, Ecological limits, Hemi-arctic, Forest tundra, Coniferous formations, Nouveau-Québec

P.N. Savitsky (1895-1968) was a Russian pioneer of the so-called "structural geography", because of its links with the Prague linguistic circle. He was the first to propose, during and after World War I, a geopolitical vision of "Eurasia", an entity which, according to its advocates, is neither Europe nor Asia, but the "place of development" of the Russian Empire and the USSR, successor of the Mongol Empire. The "Eurasia" trend finds its origin in the Russian cultural tradition, which provides it an interpretation of evolution with "internal laws" and "external influences" establishing a natural link between language, culture and Landschaft of peoples, considered as living organisms. The second origin is an original usage of the geographical method of his time. It consists of underlining the definition of "cores" to build up "structures", delimited by the overlapping of natural or human isolines.

Keywords: Eurasie, géopolitique, linguistique, structures, P.N. Savitsky, Eurasia, geopolitics, linguistics, structures, P.N. Savitsky

In spite of a large body of work on the uptake of trace metals in aquatic organisms in the last two decades, very little attention has been devoted to echinoderms (urchins, starfish, and sea cucumbers, among the most important ones), a large group of invertebrates forming a major component of most coastal ecosystems. In the course of our research program on the role of echinoderms in the biogeochemical cycling of some trace metals in coastal environment, an experiment has been conducted on the uptake and the retention of mercury species with starfish Leptasterias polaris over a 40-day exposure period.Starfish were caught near Pointe-au-Père (Québec, Canada) and were acclimatized to laboratory conditions for 10 days in a flow-through aquarium. Forty stars (84 ± 14 g) were divided in two groups, kept in two aquariums, one for inorganic mercury and the other for methylmercury exposure. Animals were isolated from each other by mean of small 65-mm net cubicles allowing free circulation of seawater at a rate of 2 L.min-1. This flow rate provided a rapid renewal of seawater and ensured the elimination of any soluble mercury excreted during the course of the experiment. Control starfish receiving only uncontaminated mussels were also maintained in both aquariums to monitor the possible uptake of mercury from seawater. Blue mussels were collected in the vicinity of Pointe-au-Père and were contaminated following a technique described elsewhere (PELLETIER and LAROCQUE, 1987). Average levels of inorganic mercury and methylmercury (MeHg) in mussels were 13 ± 3 and 14 ± 4 mg.kg-1, respectively. Each starfish received one contaminated mussel per day over a 40-day period. Mussels were weighed before to be introduced in cages and their empty shells weighed again after ingestion by starfish in order to evaluate the amount of food and mercury taken up daily by each star. Two starfish were sampled in each aquarium every five days and dissected for pyloric caeca, gonads, and endoskeleton. Coelomic fluid was also collected. Both mercury species were analysed as total mercury (assuming a preservation level of ± 85-90% of the speciation during the course of the experiment) in biological tissues by cold vapour atomic adsorption spectrophotometry (detection limit=0.005 mg.kg-1 ww). The coefficient of variation was ± 15% and the recovery yield of MeHg-spiked samples was 92 ± 12%.The concentration of inorganic mercury reached 7.56 mg.kg-1 (wet weight) in pyloric caeca and the uptake rate was 0.22 mg.kg-1.d-1. Concentrations in gonads and endoskeleton were 10 to 20 times lower than in caeca (Fig. 1). The uptake rate of MeHg (0.17 mg.kg-1d-1) was slightly slower and the maximum concentration reached in caeca was 5.34 mg.kg-1. Mercury concentrations found in coelomic fluid were low and at least 100 times smaller than those in ceaca. No mercury was found in tissues of control starfish indicating that mercury excreted by diffusion in water by contaminated starfish was not re-adsorbed by other starfish in aquariums. The mercury load in each organ of stars was calculated and expressed as a percent (%) of total Hg uptake for each chemical species (Fig. 2). The inorganic Hg loads in pyloric caeca, gonads and endoskeleton reached a steady-state after only 10 days and remained unchanged up to the end of the experiment. The behaviour of MeHg was totally different as the loads in caeca decreased from 95% to 65% but increased from almost zero up to 30% in endoskeleton. Finally, the retention (%) of mercury species was calculated by dividing the actual total amount of mercury in each starfish by the total amount of mercury received from mussels (Fig. 3). The retention of inorganic Hg was about 50% throughout the exposure period whereas the retention of MeHg increased up to 90-95% at the end of the experiment.A kinetic model, based upon the assumption that the uptake process of Hg species in the digestive system is quite similar to an ion-exchange adsorption mechanism between a contamination solution and a solid surface, was developed. The integrated equation of the rate law was expressed as: (ln(C0-q))/q0-q = K'(C0m-q0)t + ln (C0m/q0)were Co is the initial concentration of mercury in the prey, qo is the maximun amount of mercury being absorbed, and m stands for the wet weight of the animal. This equation allowed the plot of its left-hand side against time and the slope provided an estimation of an apparent exchange rate constant for each mercury species (Fig. 4). The rate constant k'MeHg was slightly higher than k'Hg, indicating a faster exchange rate for MeHg between digested mussel tissues and binding sites (and also between sites) in caeca. However, a faster exchange rate do not mean a faster uptake rate because transport rate towards other organs also play an important role in the whole bioaccumulation process. In conclusion, starfish, by its ability to digest all ingested tissues, seems to be in a position to play a major role in the sequestration of methylmercury (high retention) from mussels and from other potential preys and in recycling inorganic mercury in solution (low retention). Starfish can be seen as "marine digester" which engulfs bivalves and other invertebrates (following species) and sends back soluble metabolites and trace metals which have not been bioaccumulated.

Keywords: Échinodermes, étoile de mer, mercure, méthylmercure, prise en charge, rétention, échange ionique, modèle cinétique, constante de vitesse, Echinoderms, starfish, mercury, methylmercury, uptake, retention, ion-exchange rate, kinetic model, constant rate

Fishing is one of the most important socio-economic activities in the Mediterranean and particularly in the Maghreb. In Algeria, it has become an employment sector for a large part of the coastal population in recent decades. The exploitation of the sea also represents one of the main animal protein resources for most coastal inhabitants. This paper is a contribution to the analysis of the socio-economic dynamics of fisheries in relation to two main aspects: the first is the governance mode of coastal natural resources, and the second is the context of fragility of the coastal ecosystems characterizing the Mediterranean Sea. This work is based on a study of the fishing port of Jijel (Boudis), considered as one of the most important fishing infrastructures of Eastern Algeria. This port has undergone profound transformations due to massive public investments for the development of port infrastructure as part of a national policy of economic recovery. Public actions have led to the broadening of the regional influence of the marketing of seafood products to consumers throughout the Eastern Algerian coastline as well as the interior territories. The modernization of the port has accompanied the improvement of the transport and the channels of resale of the fish resources; however, the governance of the fishing activity in Jijel fails to master the multiple ecological, economic and social constraints.

Keywords: mer méditerranée, écosystèmes côtiers, ressources halieutiques, gouvernance des ressources naturelles, acteurs de la pêche, pêche artisanale, pêche, port de Jijel, Boudis, Algérie, Mediterranean Sea, coastal ecosystem, governance of natural resources, fisheries, artisanal fishiery, fishermen, stakeholders, Port of Jijel, Boudis, Algeria

ABSTRACTA vertical section in the 10-12 m terrace at the mouth of Ruisseau Bellechasse, near Berthier-sur-Mer, on the south shore of the middle St. Lawrence estuary, provides evidence for a 12-m maximum level for the middle Holocene Laurentian transgression. This level is two meters higher than suggested in the past. The 4-m thick intertidal unit deposited during the transgression overlies an erosion surface cut into a stratified silt and clay deposit (rhythmites), poorly fossiliferous and dated circa 10 ka. Radiocarbon dates on wood and on aquatic and intertidal plant debris in situ released ages BP between 5.4 and 6 ka (N-8). This chronology is slightly older than at Montmagny - Cap-Saint-lgnace reference sites, located approximately 30 km downstream. The Anse de Bellechasse section does not present the full sequence of Holocene events observed at Montmagny. However, there are a few fluvial terraces related to the St. Lawrence water level; one was built up circa 1.4 ka, two other between 0.5 and 0.7 ka suggesting minor fluctuations of the base level during the last two millenia.

AbstractAs many others, these two straits are places of transit which concern both the bordering states and the Great Powers, and which hold two prime functions, as ocean gateways, and as cross gateways. As ocean gateways, these two straits have symmetrical functions giving access to the seas bordering Europe, common functions on the ocean route between Asia and the main harbours of Northern Europe, and their particular functions. As cross gateways, the Pas-de-Calais (or Strait of Dover) has much higher flows than the Strait of Gibraltar, although on this last place, they are growing fast. With this plurality of functions, these straits appear as true cross-roads, and they are also places of geopolitical conflicts, because of very high migrating pressures, and attempts for a geopolitical control of these straits, by the presence of enclaves, especially on the Strait of Gibraltar.

The morphology of the Québec region and the lower St. Lawrence valley is reappraised in this article divided in three parts. The physical landscape is described in part I ; the structural conditions are examined in part II and the morphological problems are presented in part III.The relief is the result of a succession of glacial episodes and submersion and emersion episodes which followed glaciation. The over deepening of the Limoilou depression and the opening of Calvaire lake and Cap Rouge depressions are the results of the glacier. To the submerged phase correspond the alluvial fill, especially thick in the Limoilou depression, and during the emersion phase, the St. Lawrence cut in soft schists the Ancienne Lorette and the lower terrace which would have been shaped after the over deepening of the Limoilou depression.