Caractérisation de la végétation macrophytique d'un lac hautement eutrophe: le Greifensee (Suisse)

The qualitative and quantitative distribution of macrophytic vegetation of Greifensee, one of the most eutrophic lakes of Switzerland, was studied with the help of colour aerial photographs and verifications on the field. This distribution is discussed in relation to the trophic level of the lake and compared with that of several other Swiss lakes.      

Principal Modes and Related Frequencies of Sea Surface Temperature Variability in the Pacific Coast of North America

We examined monthly time-series (1950 to 1999) of sea surface temperature (SST) anomalies in 47 quadrants (2° × 2°) along the Pacific coast of North America. Correlation, clustering and principal components analyses were applied to identify the spatial structure in coastal SST. The resulting modes and the individual series were investigated using spectral analysis to identify the most significant time-scales of variability, and the propagation of the main signals was explored by computing the wavenumber-frequency spectrum of each spatial mode. Results showed that coastal SST variability in the northeast Pacific conformed to three main geographical modes. A tropical mode extends from the equator to about the entrance to the Gulf of California. This mode appears related to two low frequency components of the El Niño-Southern Oscillation of about 3 and 5 years. The SST anomaly related to these signals propagates poleward, seemingly at low speeds (≈0.08 m s^?1). A temperate (or transitional) mode, which includes the coastal areas along the California Current System, also shows the 5-year signal plus a decadal-scale component (periods between 10–17 years). Finally, a subarctic mode includes the coastal areas along the Gulf of Alaska and is dominated by the interdecadal variability that is characterized by the Pacific Decadal Oscillation.     

One million years of cultural evolution in a stable environment at Atapuerca (Burgos,Spain)

The present paper analyses the evidence provided by three sites (Sima del Elefante, Gran Dolina, and Galería) located in the Trinchera del Ferrocarril of the Sierra de Atapuerca. These three sites are cave infillings that contain sediments deposited from approximately 1.2 Ma to 200 kyr. Pollen, herpetofauna, and small and large mammal remains are used as proxies to obtain a general picture of the environmental changes that occurred at the Sierra de Atapuerca throughout the one million-year period represented at these sites. Similarly, cultural changes are tracked analyzing the evidence of human behavior obtained from the study of several bone and lithic assemblages from these three sites. At least three periods with different cultural features, involving technology, subsistence and behavior, are determined from the available evidence. The first two periods correspond to the Mode 1 technology and Homo antecessor: the first is dated around 1.2 to 1.0 Ma and reflects opportunistic behavior both in technology and subsistence. The second period is around 800 kyr BP. Mode 1 technology is still maintained, but subsistence strategies include systematic hunting and the use of base camps. The third period is dated between 500 ka and 200 ka and corresponds to the Mode 2 technology and the acquisition of directional hunting and other organizational strategies by Homo heidelbergensis. A transition from Mode 2 to Mode 3 seems to appear at the end of this time-range, and may reflect the early phases of a fourth cultural change. With regard to the environment, our main conclusion is that there was an absence of extremely harsh conditions at Atapuerca throughout this time period. The presence of Mediterranean taxa was constant and the dominant landscape was a savannah-like open environment, probably with small forest patches. An alternation of Mediterranean and mesic species as the dominant component of the tree storey was induced by the climatic cycles, and steppes spread across the landscape during the drier periods. In any case, it is not possible to establish clear cut-off points separating entirely different environmental episodes. Our results show no evidence of any relationship between environmental change and cultural change at the Sierra de Atapuerca.     

La pêche de la PerchePerca fluviatilis dans les trois lacs subjurassiens (Morat,Neuchâtel et Bienne)

The catch of perch (Perca fluviatilis) taken by professional and sport fishing is studied in three lakes located at the foot of the Swiss Jura mountains (lakes of Morat, Neuchatel and Bienne) where the annual productivity reaches 6 kg/ha. A three year cycle in the catches was induced since fifteen years by fishing pressure. Laws are suggested to improve the situation.      

Les macrophytes du lac de Bienne

The study of the qualitative and quantitative distribution of macrophytic vegetation of Bienne lake is realized with the help of colour aerial photographies and verifications on the field. This distribution is discussed in relation to the trophic level of the lake and compared with that of the Geneva lake and Morat lake.     

Mise au point sur le Néogène du domaine égéen

Résumé Cette note commente les classifications du Néogène établies dans les diverses régions de la Paratéthys et de l'Egéide. Elle présente une mise au point de quelques tableaux (qui tiennent compte des divisions du Néogène oriental parues ces dernières années. Elle se termine par un schéma comparatif du Néogène dans le domaine égéen et des étages et sous-étages établis en Italie et dans la Paratéthys centrale et orientale.

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This note comments the classifications of the Neogene for the different regions belonging to the Paratethys and to the Aegeid. Several tables taking into account the eastern Neogene divisions published recently are discussed. A coinparative scheme is presented for the Neogene of the Aegean area and the stages or substages in Italy and in the central and eastern Paratethys.

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Zusammenfassung Diese Arbeit bespricht die Gliederungen des Neogens in den verschiedenen Sedimentationsräumen der Paratethys und der Ägäis. Sie bringt eine kritische Erläuterung einiger Tabellen, die sich nach den in den letzten Jahren veröffentlichten Einteilungen richten. Ein vergleichendes Schema wird gegeben für das Neogen im ägäischen Raum und für die Stufen und Unterstufen des Neogens in Italien sowie in der zentralen und östlichen Paratethys.

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Problèmes tectoniques dans le Bassin de Transylvanie

Zusammenfassung Das Siebenbürgische Becken verdankt seine Entstehung der Schollen-Struktur der Karpaten. Es besteht aus einer relativ wenig erhöhten Scholle, die von sehr hohen Schollen umringt ist. Dieser Zustand besteht erst seit dem Mittel-Miozän. Vorher war ein großer Teil des Beckens Festland. Im Neogen breitete es sich über das Maramure-Becken aus, das erst zum Ende des Pliozäns selbständig wurde. Von den vier tektonischen Einheiten, die sich ringsum befinden: Südkarpaten, Ostkarpaten, Apuseni-Gebirge und Verborgenes Apuseni-Gebirge, ist das Becken durch mehr oder minder wichtige Krustalbrüche begrenzt. Die Begrenzung des Beckens im NW ist weniger deutlich. Hier erhebt sich das Grundgebirge fortschreitend, bis es in Form von kleinen kristallinen Inseln: Mese-Preluca, Prisaca-Gebirge u. a. an der Oberfläche erscheint. Obwohl das Becken einheitlich erscheint, besteht es dennoch aus zwei großen, einem Nord- und einem Südbezirk. Die Grenze dazwischen wird im Westen durch die Richtung der kristallin-mesozoischen Falten des Apuseni-Gebirges und im Osten durch die Verschiebung der Krustalbrüche in der Gegend von Sovata-Gheorghieni, welche das Erscheinen des Neoeruptivs bedingte, angegeben. Der südliche Bezirk wird durch eine schwache Erhebung charakterisiert, die die Erhaltung von mächtigen pliozänen Ablagerungen bedingt hat. Hier wurden 14 tektonische Elemente — Blöcke und Brüche — festgestellt, welche dem Becken das Aussehen eines Amphitheaters verleihen. Der nördliche Bezirk zeichnet sich durch die schon während des Oberpliozäns bestende Erhebung des Grundgebirges in nordwestlicher Richtung aus. Diese Erhebung hat das Paläogen auf großen Oberflächen zutage gebracht, während das Pliozän vollständig abgetragen wurde. Das vorneozoische Grundgebirge besteht aus zahlreichen Blöcken, deren Bewegungen Brüche in der relativ dünnen Decke bedingt haben. Die Kreuzung der radiären mit den longitudinalen Tiefbrüchen ist oftmals durch Salzstöcke und Horizontalflexur gekennzeichnet. Bisher wurde den Faltenvorgängen große Wichtigkeit beigemessen. Heute ist die wichtige Rolle der Brüche bekannt, die das Erscheinen des neogenen Eruptivs auch im Innern des Beckens bedingt hat.

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The Transylvanian basin owes its existence to the block-faulted structure of the Carpathian regions. It represents a relatively slightly uplifted block surrounded by strongly uplifted ones. This situation only dates from the Middle Miocene, until which date a great part of the basin represented dry land for a long period. During the Neogene it also included the Maramure basin which only became independent at the end of the Pliocene time. The basin is separated from the four surrounding units, namely the South Carpathians, the East Carpathians, the Apuseni Mountains and the hidden Apuseni Mountains by fractures which are sometimes very important. Crustal fractures delimit the basin from the first three units. The border of the basin is less clear in the NW, where it comes in touch with the hidden Apuseni Mountains. Above the latter the basin marks a gradual upheaval, up to the crystalline islands in Mese, Prisaca and Preluca. Though of apparently unitary character, the basin consists of two large sectors: one to the south and the other one to the north. The separation line between them is indicated by the trend of the crystalline-Mesozoic folds west of Turda, as well as by the displacement that affected, at Sovata-Gheorgheni level, the zone where the new volcanic formations occured. The southern sector is characterized by moderate uplifting; that allowed the preserving of a large quantity of pliocene sediments. A number of fourteen tectonic elements represented by blocks and faults conferring upon the basin the aspect of an amphitheatre, have been distinguished in the above sediments. The northern sector is characterized by a gradual uplifting in the northwestern direction which started in the Upper Pliocene. Due to this uplift the Paleogene formations have been exposed on large areas. The most important consequence was, however, an almost total erosion of the Pliocene deposits. Since the pre-Neozoic basement was built up of numerous blocks, their movements have determined a great number of fractures in the relatively thin cover of Paleogene-Miocene age. On the basin borders, one may notice the presence of numerous faults showing a radial arrangement. These faults disappear towards the inner part of the basin. The intersections between the crustal faults and the radial faults are frequently marked by the presence of salt massifs and by displacements. Great significance was assigned in the past to the folded structures: anticlines and domes. Nowadays, we consider the faults as more important than the folds. The appearance of volcanic Neogene rocks, even in the inner part of the basin, justifies this idea.

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Résumé L'auteur décrit la construction tectonique du bassin de Transylvanie, qui est situé entre quatre unités structurales: Les Carpates méridionales, les Carpates orientales, les Monts Apuseni et les îles cristallines du NW. Le bassin de Transylvanie se détache de ces unités structurales par des fractures. De nos jours, ces déformations par fractures prennent de plus en plus d'importance, tandisque jusqu'alors on attachait plus de significance aux phénomènes de plissement.

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Comparaison au moyen de la lysotypie entre souches d'Aeromonas de pisciculture et souches isolées de l'homme

The spreading of bacteria of the genusAeromonas in intensive fish rearing tanks was analyzed during one year. Lysotyping has established epidemiologic correlations between the strains ofAeromonas isolated from the aquatic environment and those of clinical (human) origin.

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Dédié à Wolfgang Geiger     

Excrétion de carbone organique par le phytoplancton lémanique

The release of soluble organic carbon by the phytoplankton in the trophogenic layer of Lake Geneva has been investigated by¹⁴C method from March to November 1984. The carbon excretion rate varied from 0.01 to 0.5 mg C·m⁻³·h⁻¹ and depended primarily upon the rate of its photosynthetic assimilation. The carbon excretion rate varied generally between 2 and 5% of photoassimilated carbon and exceptionally exceeded 6%. These values were underestimated from part of heterotrophic reassimilation. The study of the carbon balance over 24 hours has shown that night excretion represents less than 10% of losses due to respiration. Heterotrophic activity measured by¹⁴C glucose assimilation exhibited seasonal variations following the same general pattern as excretion. The quantity of phytoplankton excretion products appeared to be superior to the needs in organic compounds of heterotrophic organisms in the trophogenic layer.