ALBERT

Beschreibung: It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight some of the more representative examples in the text, and discuss some ecological and evolutionary aspects of the use of chemosensory information for prey decision making. Curiously, only one example illustrates the ability of birds to detect predator odours and we have found no examples for terrestrial insects, suggesting a fruitful area for future study.

Beschreibung: Horizontal starch gel electrophoresis was employed to investigate levels of genetic differentiation between 13 samples of the neritic squid species Loligo forbesi Steenstrup obtained from throughout the majority of its known geographical range. Six enzyme loci identified in a preliminary study as being polymorphic were screened for variation between samples. No significant differences in allele distribution were detected between any of the samples obtained from the Faroe Bank in the north to Lisbon in the south, suggesting that squid throughout this range in the vicinity of the continental shelf are able to maintain panmixia, and effectively belong to a single population sharing a common gene pool. No clinal variation in allele distribution was detected throughout this range, a result which complements the findings of a detailed morphological companion study of the same individuals. Comparison of this homogenous European continental shelf population with squid from the Azores revealed highly significant (P〈0.01) differences in allele distribution at five of the six polymorphic enzyme loci studied. A genetic identity value (I) equivalent to 0.93 over 33 loci was obtained. Analysis of F-statistics suggested migration rates between sites to be as low as one individual per five generations, a rate deemed insufficient under most models to prevent divergence by random genetic drift. The large distance and oceanic depths separating the Azores from continental Europe seem to present an effective barrier to gene flow to L. forbesi, a squid belonging to a family considered to be confined in distribution to relatively shallow, near coastal waters. The two populations of squid in the Azores and along the European continental shelf currently both ascribed to L. forbesi should therefore probably best be regarded as relative subspecies.

Beschreibung: Beak lengths (lower rostral length and upper rostral length) were taken for a sample of Moroteuthis ingens which were captured on the Chatham Rise, New Zealand. Beak lengths were plotted against both mantle length and wet weight to determine the relationship between these parameters for future use in biomass estimates in predator analysis. Although M. ingens is markedly sexually dimorphic, with females reaching 5 times the weight of males, there was no obvious sexual dimorphism in either lower or upper rostral length. This resulted in sex-specific relationships between both LRL and mantle length, LRL and weight; and URL and mantle length, and URL and weight. Males appeared to have a curvilinear relationship between beak length and mantle length and beak length and weight (even for log-transformed data). There was also considerable spread in the data in the plot between beak length and weight for females of similar weight. These characteristics of the data makes biomass estimates based on rostral length measurements for this species difficult. Other beak parameters may prove more useful for estimating biomass of M. ingens.

Beschreibung: Body size at sexual maturity, egg-size distributions, and potential reproductive output have been estimated for female and male squid, Loligo forbesi Steenstrup, off the west coast of Scotland. Two size modes at maturity were found in both sexes, but separation into size cohorts was more pronounced in males (180 and 350 mm mantle length, ML). Preliminary ageing studies based on statolith ring-counts suggest that these size modes are not due to different age groups at breeding. Females have a single size mode of mature eggs in the proximal oviduct, but may have at least two size modes of eggs within the ovary. This finding is interpreted as evidence of batch-spawning in this squid. There was a weak relationship between total egg numbers (range 1000 to 16000) and body size (range 196 to 318 mm ML) and between mature egg size and body size. Males showed a strong positive relationship between spermatophore length and body length but a weak relationship between total number of spermatophores and body size. The results are discussed in the context of flexibility of breeding strategies in the loliginids and variety of life-cycle patterns.

Beschreibung: This study assesses the potential of the tropical loliginid squid Photololigo sp. to lay multiple batches of eggs and examines changes in somatic growth during reproduction. Histological analysis of the ovary and the relative size of the oviduct to mantle weight and ovary weight were used to determine the potential for multiple spawning. Ovaries of mature females always had immature and mature oocytes present, suggesting that not all the oocytes were maturing simultaneously and that multiple batches of eggs were being produced. Furthermore, poor correlations of oviduct weight with body size and ovary weight indicated that mature oocytes were not accumulating in the oviduct for a single spawning event. Both these observations supported the hypothesis that Photololigo sp. has the potential to lay multiple batches of eggs throughout its life. Specific growth rates, length-weight relationships, relative growth of somatic and reproductive tissue and microscopic assessment of muscle tissue were compared between immature and mature females. Growth rates of immature females were almost twice as fast as those of mature females. Mature females also had no large muscle fibres present, suggesting that energy for reproduction was mobilised from the muscle tissue.

Beschreibung: A new image of the French continental crust between Brabant (Belgium) and the Basque province of Spain is presented on the basis of considerable recent geological and geophysical information as well as the compilation and reInterprétation of previously available data. The resulting section, which shows the main basement structures to a depth of 45 km, also is the first nonspeculative image of the westernmost part of the Variscan orogen. The French Global Geoscience Transect reveals a complete picture of this orogen between its remnant root and the surface. The divergent thrusts are bounded on the north and in the south by the old Brabant and Ebro-Aquitaine cratons, respectively; these thrusts also involve two previous plate boundaries. The lower part of the orogen is limited by a layered lower crust, probably of Permian age. Near the surface the Hercynian orogen is buried—near the northern end of the transect by the Paris Basin, which can be considered an eastward extension of the English Channel, and in the south by the South Armorican continental margin, which makes a transition between the oceanic crust of the Bay of Biscay and the axis of the Variscan orogen. In this area, the deep Parentis graben is located at the site of pronounced crustal thinning, since only 7 km of Hercynian crust are now preserved.

Beschreibung: Alkaline volcanic rocks including nephelinites, basanites and trachybasalts dredged from the volcanic pedestal of Rakahanga Atoll and from a volcanic edifice with 100 satellite volcanoes at the eastern edge of the Manihiki Plateau, ca. 40 km southwest of the atoll, fall well within the category of EM-type ocean island basalts. They indicate a hotspot involvement during the formation of the plateau basement. The rocks are thought to be products of explosive eruptions which took place subaerially or in shallow water in the Aptian. The volcanoes, together with other volcanic eruption centers, most likely were responsible for the formation of the 230 m thick volcaniclastite layer which rests on the basement for at least 5000 km2 of the eastern part of the Manihiki Plateau. Erosion has prevented any substantial sediment cover on the volcanic cone field and most of the slope of Rakahanga and thin pelagic limestones were deposited instead at least since the Maastrichtian.

Beschreibung: A model is presented which tests the representation of the maturity process in terms of gonadosomatic indices (GSI) in chokka squid Loligo vulgaris reynaudii. It assumes that the true maturation process is reflected by the results of histological investigation, which cannot be used in large-scale ecological work in the field. However, the maturity scales used in ecological studies define some morphological categories which can be linked directly to microscopic development. Therefore, the overlap of GSI ranges for each morphological maturity category may be used to judge how well the GSIs represent the histological stages. Results have shown that the overlap is large and that GSI cannot be recommended as adequately reflecting the maturation process in squid. A morphological scale of maturity with possible broad applications in exploited families of squid is proposed as a better representation of the maturation process than GSI.

Beschreibung: Morphological differences between paralarvae of two loliginid squid species common in southern African waters (Loligo vulgaris reynaudii and Lolliguncula mercatoris) are described. The differences are: Loligo — "cheek patches" consisting of four dark chromatophores, nine large dark dorsal chromatophores on the mantle, tentacular clubs broad and much wider than tentacle stalks, proximal row of three club suckers with others tetraserial, suckers large enough to appear crowded on the club surface; Lolliguncula — "cheek patches" with three dark chromatophores, two pairs of" large, dark dorsal chromatophores on the mantle, tentacular clubs narrow, proximal club suckers arranged in three pairs, suckers small, not particularly crowded. Relationships with other myopsids are briefly discussed.

Beschreibung: The natural feeding of 485 Octopus mimus (164 to 3088 g) was studied in relation to the species' life cycle and environmental seasonal variations off the north of Chile from autumn 1991 to summer 1992. Analysis of digestive-tract contents revealed that O. mimus preyed upon 25 different prey items belonging to five zoological groups (Teleostei, Mollusca, Crustacea, Echinodermata and Polychaeta). Cannibalism was only occasional. The results indicate that the diet and food intake of this species are significantly affected by sex and maturation. Senescent individuals ingest a small amount of food, and their diet is mainly based on small, not very motile prey. The food intake, expressed as body weight, of non-senescent individuals is higher in females than in males. Seasonal changes in sea-water temperature seem to be followed by adjustments in food intake. Like other Octopus species, O. mimus appears to be an opportunistic predator.

Beschreibung: The relationship between reproduction and condition was studied in a 15 mo sample of 919 maturing, mature and post-spawning female Octopus mimus (388 to 3714 g) caught in Iquique (North Chile). O. mimus is a semelparous species, with reproduction taking place all year round. Investment in reproductive tissues was, on average, 9.9% of mature female body weight, independent of season. However, somatic growth during maturation was dependent on season and varied between 26 and 63% of the whole-body growth in weight. The condition of females did not vary markedly until spawning, although seasonal variations were apparent, winter being the most unfavourable. Condition deteriorated dramatically after spawning, during parental care of the eggs. During this period, somatic-tissue depletion, mainly from the muscles, was 〉25% of the total body weight of mature females. The fecundity of O. mimus was probably limited by the costs associated with parental care of the eggs.

Beschreibung: Detrital sediment is carried from land to the sea by three agents, rivers, glaciers, and winds. The shoreline is an arbitrary boundary within the detrital sediment transport system, which extends from a site of origin across areas of temporary storage to a site of long-term deposition. The most important of the agents moving sediment across the land is river transport, estimated to be in the order of 20×1012 kg of sediment annually at present. Analysis of drainage basins indicates that relief and runoff are the most important factors in determining the sediment load of rivers. The competence of rivers to transport sediment is governed by the volume flow, gradient, and the sediment load itself. Today, most large rivers are fed by snowmelt in highland areas, runoff from rainfall in the drainage basin, and groundwater inflow. Along the river course, water is lost to evaporation and groundwater infiltration. River courses can often be divided into two segments, a degradational section in which the gradient is relatively steep and little temporary storage of sediment takes place, and an aggradational section where the gradient is sharply reduced through meandering, and where large-scale temporary sediment storage forms a flood plain. Lakes trap sediment inland and prevent its transport to the sea. Today, many high and mid-latitude rivers are interrupted by lakes of glacial origin. There are also some large areas of internal drainage that deliver no sediment to the sea. The load carried by rivers has been markedly altered by human activity, and may have doubled over the past few thousand years, only to be reduced in the past century by the widespread construction of dams. The ancient use of fire in hunting and its subsequent use in clearing land has increased erosion. Extensive deforestation and cultivation processes have also increased the sediment supply. Dam construction is a relatively new factor and affects the sediment transport system by trapping sediment before it can reach the sea. The resulting lower sediment supply from rivers is, at least in part, compensated by increased coastal erosion. Glacial erosion is difficult to estimate. There is an ongoing controversy whether ice sheets are effective erosive agents or not. Estimates of the present global flux of glacial detritus range from 0.8–50×1012 kg annually, with the lower value most probable. The dust flux is in the order of 0.5 to 0.9×1012 kg annually, but may vary greatly with time.

Beschreibung: Bottom shots have been used for a number of years in seismic studies on the ocean floor. Most experiments utilized explosives as the energy source, though researchers have recognized the usefulness of collapsing water voids to produce seismoacoustic signals. Implosive sources, however, suffered generally from a lack of control of source depth. We present a new experimental tool, called SEEBOSEIS, to carry out seismic experiments on the seafloor utilizing hollow glass spheres as controlled implosive sources. The source is a 10-inch BENTHOS float with penetrator. Inside the sphere we place a small explosive charge (two detonators) to destabilize the glass wall. The time of detonation is controlled by an external shooting device. Test measurements on the Ninetyeast Ridge, Indian Ocean, show that the implosive sources can be used in seismic refraction experiments to image the subbottom P- wave velocity structure in detail beyond that possible with traditional marine seismic techniques. Additionally, the implosions permit the efficient generation of dispersed Scholte waves, revealing upper crustal S-wave velocities. The frequency band of seismic energy ranges from less than 1 Hz for Scholte modes up to 1000 Hz for diving P-waves. Therefore, broadband recording units with sampling rates 〉2000 Hz are recommended to sample the entire wave field radiated by implosive sources.

Beschreibung: This chapter discusses the rates of protein synthesis in fish. Protein synthesis can be viewed at a number of levels. Whole-animal values can be integrated into the descriptions of assimilation/growth or assimilation/metabolism patterns in different fish species and is the focus of the chapter. The measurement of protein synthesis rates in body organs and tissues can provide information on the extent to which differences exist among various tissues and offer a challenge in understanding the integration of organ metabolism into whole animal physiology. The majority of methods for estimating protein synthesis measure the flux of an amino acid or nitrogen. This involves the use of tracer substances—that is, amino acids labeled with an isotope, which are given in a single dose or by continuous infusion. The measurements, parameters, and formulae that are commonly employed in the studies of protein growth, synthesis, and degradation are described in the chapter. It discusses the mechanism of nutrition and protein synthesis in the fish and explains the impact that protein synthesis has upon the rates of oxygen consumption.

Beschreibung: In the Neil Brown Instruments' MKIIIB-CTD (conductivity-temperature-depth profiler), the system's digital outputs for the three basic measurements of temperature, conductivity and pressure typically show some small amplitude deviations from smooth calibrations which should be corrected for to achieve high accuracies, as required, e.g. within the Hydrographic Program (WHP) of the current World Ocean Circulation Experiment (WOCE). These deviations show up as (i) a strong nonlinearity or even discontinuity of several mK close to 0°C in temperature output leading to too high subzero temperatures; (ii) a jump of order 0.002 mS cm−1 in conductivity output when passing the half-range value 32.768 mS cm−1, which causes jumps in the relation of potential temperature and salinity; and (iii) errors in pressure measurements of up to 4 dbar due to mechanical hysteresis and both static and dynamic responses to temperature changes. The existence of these effects is demonstrated, and methods to reduce the associated errors are suggested.

Beschreibung: Based on various lines of evidence such as the widespread occurrence of basalts, pumice, volcanic glass shards and their transformational products (zeolites, palagonites, and smectite-rich sediments), we suggest the presence of a volcanic province in the Central Indian Basin (CIB). In addition to the rocks studied, the occurrence of many morpho-tectonic features such as seamounts, abyssal hills and major fracture zones at 73 degrees E, 75 degrees 45'E and 79 degrees E, have helped in correlating and in deciphering the source of the rock types. Further, the large manganese nodule fields in the CIB are seen to occur in conjunction with the volcanic materials, since the latter forms nuclei and substrates for ferromanganese deposits. It is concluded that a spatial relation exists between the occurrence of the volcanic materials and the ferromanganese deposit in the CIB

Beschreibung: A study of the echo peak amplitudes from known nodule areas is initiated to observe the acoustic response for varying nodule abundances and number densities. A statistical study of the peak amplitudes from different nodule areas confirms that the coefficient of variation is the highest for medium nodule abundance and number density. Echo fluctuation study based on the Rician probability density function (PDF) establishes that the non‐nodule sediment bottom contributes to less scattering, i.e., it is a microtopographic type, whereas scattering is dominant in the nodule‐bearing areas. The spectral studies are conducted on depth data of different areas. This study ensures that the signal scattering in the nodule bottom area is due to the nodules lying on the seabed rather than the large / small‐scale topographic variations. The study based on Poisson PDF for nodule area confirms this fact again. Agreement between the nodule distribution and the Poisson distribution parameter is clearly seen. Such a relation is not observed in the case of Rician density functions.

Beschreibung: The diet of emperor penguins Aptenodytes forsteri was studied during late austral summer at Drescher Inlet, eastern Weddell Sea, Antarctica. Antarctic krill Euphausia superba was a major component of the food, accounting for 75% of all prey items. Emperor penguins appear to feed on krill during shallow dives under the fast sea ice. Fish, mainly nototheniids, accounted for less than 20% by number of all prey. An evaluation of the main prey types in terms of mass indicated, however, that fish represented up to 75% approximately of prey mass. Feeding experiments were performed on captive penguins and showed that squid beaks can accumulate for up to 3 weeks within the stomach without any clear signs of erosion. The lack of cephalopod soft parts in the samples makes it likely that all squid beaks were derived from animals captured some time previously. Squid seems to be a very minor dietary component of emperor penguins at the Drescher Inlet.

Beschreibung: A method for attaching acoustic transmitters externally to deep-water fishes in situ is described. Tags, each comprising a transmitter connected to a dart, were fired at fish from a pneumatic gun held by the manipulator arm of a submersible. The method was applied successfully for tagging coelacanths and may have application for use with other species of fishes living at depths to about 1000 m. The usefulness of direct observation for monitoring the effects of tags on fish is evaluated in relation to the effects of the tagging method on coelacanths.

Beschreibung: Plastic debris accumulates in the marine environment following its use in agricultural, industrial and social activities. Its ultimate fate is accomodation in sediments where it may persist for times up to centuries or longer. There appears to be an increasing flux of materials with time and an increased areal coverage of the benthos. Impacts upon bottom organisms can take many forms. Systematic monitoring tactics for the extent of seafloor coverage by plastics are yet to be incorporated into national programs.

Beschreibung: The sea-ice export out of the central Arctic through the Fram Strait is a key variable in the Arctic climate system. Satellite data provide the only basis for mapping ice features with a high spatial and temporal resolution in polar regions. An automatic drift algorithm has been employed and optimized to monitor the sea-ice drift velocity in the Greenland Sea with AVHRR data. The combination of the ice drift and the spatial ice distribution provides an insight into the ice transport processes along the coast of Greenland. The combination with sea-ice thickness measurements allows an estimation of the spatial distribution of the sea-ice mass flux. The seasonal and spatial variability of the mass flux allows further predictions of the meridional melting and freezing processes along the East Greenland Current. This investigation covers the years 1993 and 1994. Seasonal and spatial distributions of the sea-ice drift were derived. The derived absolute values in this study are in good agreement with estimates proposed by other authors.

Beschreibung: Dinoflagellate cysts and other organic-walled microfossils have been studied in recent surface sediments from the entire Norwegian-Greenland Sea. More than 30 taxa have been recognized, of which only few show a distinct distribution pattern, and allow description of four assemblages. The occurrence of most taxa is related to the relatively warmer waters of the Norwegian Sea. Algidaspaeridium? minutum s.1., Brigantedinium simplex and Impagidinium? pallidum are the only species showing a preference for colder water masses. Two species, I.? pallidum and Nematosphaeropsis labyrinthus are mainly restricted to the oceanic environment, whereas the other species have also been reported from neritic environments in previous studies. Due to the limited knowledge of the ecological and sedimentological factors influencing the occurrence of dinoflagellate cysts in oceanic environments, their distribution in recent sediments can be only related to surface water masses in a broad sense. Although the distribution of assemblages correlates with specific surface water masses, comparison with assemblages recovered from sediment traps deployed basinwide in the Norwegian-Greenland Sea (Dale and Dale, 1992) revealed some major discrepancies in species composition and percentage abundances. The differences cannot be explained with certainty at the moment, although there is some evidence that transport of dinoflagellate cysts and other fossilizable microplankton in water masses by currents, in sea-ice and sediments may modify the assemblages found in recent oceanic surface sediments from the Norwegian-Greenland Sea.

Beschreibung: Benthic foraminifera and surface sediments were analyzed from 23 box-core and core-top samples from 250 to 3600 m depth at the southern Portuguese continental margin between 37 and 38 °N. This area is affected by the MOW which flows northwards along the slope between 600 and 1500 m waterdepth. Sediment structures, grain-size distribution and clay mineral assemblages of surface sediments indicate active winnowing in the upper part of the MOW, and deposition of the fine fraction near its lower boundary. R-mode cluster analyses of foraminiferal census data from the 〉 250 μm fraction revealed four associations. The ‘Shelf Edge Association’ occurs on glauconitic shelf and upper slope sands down to 268 m. The ‘Upper Slope Association’ is recognized between 498 and 1300 m where sand-silt-clays to clayey silts are encountered. The ‘Lower Slope Association’ is found between 1405 and 2985 m and differs markedly from assemblages below 3000 m (‘Deep Water Association’) where the near-surface sediments are soft hemipelagic clays. The ‘Boundary Layer Association’ shows no significant depth limits but abundance maxima both in the density interface above the MOW and in the interval of decreasing turbulence below it. The boundaries of the ‘Shelf Edge’ and ‘Upper Slope Association’ correspond to these hydrographic boundary layers whereas the boundary between ‘Lower Slope’ and ‘Deep Water Assemblage’ is related to threshold values of nutrient flux to the benthic community. Examination of hard-substrates reveals 27 different species of epibenthic foraminifera. Six of these, the ‘Epibenthos Group’, were found attached to elevated substrates only within the MOW. Above the MOW, elevated substrates were inhabited by different species, whilst below the MOW they were not used by any epibenthic foraminifers. Evidently, the hydrodynamic environment of the MOW current provides an ecological niche which is efficiently used by opportunistic suspension feeders. The ‘Epibenthos Group’ is more abundant in the middle part of the study area between 37 °20′ and 37 °40′N where the sand content of surface sediments is also higher. Both indicate an enhanced sediment-water interaction in this area which results from an obstruction of the MOW flow by the ‘Principes d'Avis’ basement spur.

Beschreibung: Fluxes of phosphate across the sediment–water interface have been measured using inhibitors of bacterial activity sterilization and chloramphenicol and a control in order to quantify the influence of bacterial abundance on them. Results show that phosphate concentration in the interstitial water decreased when bacteria were present, in relation to treated aquaria. The measured (Jo) and theoretical fluxes (Jd) of phosphate also were higher when bacterial activity was suppressed. Mass balance calculated for Carbon, Nitrogen and Phosphorus in the sediment revealed a loss of theses compounds when bacterial activity was suppressed, and a net accumulation of Carbon and Phosphorus, and loss of Nitrogen under natural conditions.

Beschreibung: The flow field in the area of what was thought to be the source region of the North Brazil Current (NBC) off the northeast coast of Brazil between 5 degrees 30'S and 10 degrees S was investigated in austral spring during November 1992 and compared with observations in October 1990. The data were taken with several different instruments, including vessel-mounted ADCP, lowered-ADCP, Pegasus, CTD and XBTs. The flow was found off the coast at 5 degrees 30'S as well as at 10 degrees S as an undercurrent, the North Brazil Undercurrent (NBUC). The NBUC shows a subsurface core at about 200 m depth with velocities of up to 90.0 cm s(-1), resulting in large northward transports of more than 22 Sv in the upper 1000 m. The transport is about the same at 5 degrees 30'S and 10 degrees S, hence no net inflow from the east is required to feed the NBUC. The climatological Ekman transport is to the south between 5 degrees 30'S and 10 degrees S, and in consequence the northward flow near the surface was reduced and might be one reason for the existence of the undercurrent. The flow near the coast was to the north at 10 degrees S, therefore the Brazil Current had to start as a coastal current south of 10 degrees S. For the zonal sections at 5 degrees 30'S and 10 degrees S the geostrophic computations relative to the density surface sigma(1) = 32.15 kg m(-3) (about 1150 m depth) resulted in transports comparable to those obtained from direct measurements. The results further show that the choice of a correct level of no motion can be supported by the direct observations. A shallower reference based on water mass boundaries alone would reduce the NBUC transport to almost zero. Computations with data from the historical data base for austral fall resulted in a weaker NBUC of less than 20 Sv near 10 degrees S, indicating a possible seasonal signal in the NBUC with a stronger NBUC in austral spring.

Beschreibung: The Laptev Sea is of great significance for studying the processes of the initial breakup of continents. It is the southern termination of the Gakkel spreading ridge and thus the location of structural features resulting from a continental margin/spreading ridge intersection. The present-day understanding of the Laptev Shelf geology is based on the Russian multichannel seismic reflection data and extrapolation of the terrestrial geology. Geologic and plate-kinematic data are used to constrain the interpretation of the seismic reflection data. The Laptev Rift System consists of several deep subsided rifts and high standing blocks of the basement. From west to east these are: the West Laptev and South Laptev rift basins, Ust' Lena Rift, East Laptev and Stolbovoi horsts, Bel'kov-Svyatoi Nos and Anisin rifts. The central and eastern parts of the shelf have the greatest contrasts in the gravity field ranging from −60 mGal over the rifts to 50 mGal over the horsts. The rifts contain up to five seismic stratigraphic units bounded by clear regional reflectors and underlain by folded heterogeneous basement. They are suggested to be Late Cretaceous to Holocene in age and reflect different stages of spreading ridge/continental margin interaction. The estimated total thickness of the rift-related sediments varies between 4 and 8–10 km while the sedimentary cover on the uplifts is significantly reduced and generally does not exceed 1–2 km. An eastward decrease of the total thickness of the sedimentary sections from about 10 km in the South Laptev Basin to 4–5 km in the Bel'kov-Svyatoi Nos Rift and the simplicity of the entire rift structure may indicate a rejuvenation of the rifts in the same direction. The entire rift system is covered by the uppermost seismic unit, which probably reflects a deceleration of the rifting during the last reorganization of the North American/Eurasian plate interaction since about 2 Ma.

Beschreibung: Russian and German scientists have investigated the extreme environmental system in and around the Laptev Sea in the Siberian Arctic. For the first time a major comprehensive research program combining the efforts of several projects addressed both oceanic and terrestrial processes, and their consequences for marine and terrestrial biota, landscape evolution as well as land-ocean interactions. The primary scientific goal of the multidisciplinary program was to decipher past climate variations and their impact on contemporary environmental changes. Extensive studies of the atmosphere, sea ice, water column, and sea-floor on the Laptev Sea Shelf, as well as of the vegetation, soil development, carbon cycle, permafrost behaviour and lake hydrology, and sedimentationon Taymyr Peninsula and Severnaya Zemlya Archipelago were performed during the past years under a framework of joint research activities. They included land and marine expeditions during spring (melting), summer (ice free), and autumn (freezing) seasons. The close bilateral cooperation between many institutions in Russia and Germany succeeded in drawing a picture of important processes shaping the marine and terrestrial environment in northern Central Siberia in Late Quaternary time. The success of the projects, which ended in late 1997, resulted in the definition and establishment of a new major research effort which will concentrate on establishing a better understanding of the paleoclimatic and paleoenvironmental record of the area. This is important because it allows to be able to judge rates and extremes of potential future environmental changes.

Beschreibung: During the ARCTIC '91 expedition aboard RV Polarstern (ARK VIII/3) to the Central Arctic Ocean, a box corer sample on the Gakkel Ridge at 87 degrees N and 60 degrees E yielded a layer of sand-sized, dark brown volcanic glass shards at the surface of the sediment core. These shards have been investigated by petrographic, mineralogical, geochemical and radiogenic isotope methods. The nearly vesicle-free and aphyric glass shards bear only minute microphenocrysts of magnesiochromite and olivine (Fo(88-89)). Most glasses are fresh, although some show signs of incipient low-temperature alteration. From their shapes and sizes, the glass shards most likely formed by spalling of glassy rinds of a nearby volcanic outcrop. Geochemically, the glasses are relatively unfractionated tholeiites with E-MORB trace element compositions. Thus, they are quite similar to the previously investigated ARK IV/3-11-370-5 basalts from 86 degrees N. The Nd and Sr isotopic ratios of PS 2167-2 glasses are significantly lower than for ARK IV/3-11-370-5 basalts and suggest an isotopically heterogeneous mantle source of Gakkel Ridge MORE between 86 degrees and 87 degrees N. The positive Delta-8/4 Pb value (similar to 16) and high Sr-87/Sr-86 ratio (0.70270), found for PS 2167-2 glasses are similar to that of ARK IV/3-11-370-5 basalts and show the influence of the DUPAL isotopic anomaly in the high Arctic mantle. These results argue against the presence of an 'anti-DUPAL anomaly' in the mantle below the North Pole region and simple models of whole-mantle convection.

Beschreibung: Analogue experiments in part I led to the conclusion that pyroclastic flows depositing very highgrade ignimbrite move as dilute suspension currents. In the thermo–fluid–dynamical model developed, the degree of cooling of expanded turbulent pyroclastic flows dynamically evolves in response to entrainment of air and mass loss to sedimentation. Initial conditions of the currents are derived from column-collapse modeling for magmas with an initial H2O content of 1–3 wt.% erupting through circular vents and caldera ring-fissures. The flows spread either longitudinally or radially from source up to a runout distance that increases with higher mass flux but decreases with higher gas content, temperature, bottom slope and coarser initial grain size. Progressive dilution by entrainment and sedimentation causes pyroclastic currents to transform into buoyant ash plumes at the runout distance. The ash plumes reach stratospheric heights and distribute 30–80% of the erupted material as widespread co-ignimbrite ash. Pyroclastic suspension currents with initial mass fluxes of 107-1012 kg/s can spread for tens of kilometers with only limited cooling, although they move as supercritical, strongly entraining currents for the eruption conditions considered here. With increasing eruption mass flux, cooling during passage through the fountain diminishes while cooling during flow transport increases. The net effect is that eruption temperature exerts the prime control on emplacement temperature. Pyroclastic suspension currents can form welded ignimbrite across their entire extent if eruption temperature is To11.3.Tmw, the minimum welding temperature. High eruption rates, a large fraction of fine ash, and a ring-fissure vent favor the formation of extensive high-grade ignimbrite. For very hot eruptions produc ing sticky, partially molten pyroclasts, analysis of particle aggregation systematics shows that factors favoring longer runout also favor more efficient aggregation, which reduces runout. As a result, very high-grade ignimbrites cannot spread more than a few tens of kilometers from their source. In cooler pyroclastic currents, particles do not aggregate, and the sedimentation process may involve re-entrainment of particles, which potentially leads to more extensive cooling and longer runout; such effects, however, are only significant when net erosion of substrate occurs. Model results can be employed to estimate mass flux and duration of ignimbrite eruptions from measured ignimbrite masses and aspect ratios. The model also provides an alternative explanation of the observed decrease in H/Lratios with ignimbrite mass.

Beschreibung: AVHRR satellite imagery of the southern Mid-Atlantic Bight during May 1993 revealed a large area of cold water over the shelf break and slope that appeared to spin up into a series of southward propagating anticyclonic eddies. The eddies had diameters of 35–45 km at the surface and moved southward at about 20 cm/sec. A radial TOYO CTD (to 50m) and ADCP velocity (to 400m) transect was conducted across the southern-most of these eddies. The upper 50 meters had minimum temperatures of less than 7°C and salinities of about 33 pss, characteristics similar to cold pool waters usually found over the continental shelf. ADCP velocity data from one of the eddies revealed anticyclonic flow extending to a depth of about 250m. The transport of cold pool water by the eddies was estimated to be 0.1 to 0.2 Sv which is of the same order as the annual mean alongshore transport of shelf water in this region. The origin of the deeper water within the eddy is unlikely to be the continental shelf because the shelf break is less than 100 m. The depth and velocity profiles along the TOYO transect were consistent with the constant potential vorticity eddy model of Flierl (1979) although the source of the eddy kinetic energy is uncertain. The cause for the exodus of cold pool water from the shelf, which extended northward to at least 38°N, is unclear but must involve the establishment of an alongshore baroclinic pressure gradient against the usual southwestward shelf flow. It is possible that the intrusion of Gulf Stream waters onto the shelf near Cape Hatteras was a precursor of this off shelf transport. The southern-most eddy was marked by high biological productivity and very high oxygen supersaturation. The phytoplankton bloom detected within the exported cold pool water, located over the continental slope, suggests a mechanism whereby production fueled by nutrients derived from the shelf can be locally exported into deep water

Beschreibung: The assessment of direct effects of anthropogenic CO2 increase on the marine biota has received relatively little attention compared to the intense research on CO2-related responses of the terrestrial biosphere. Yet, due to the rapid air–sea gas exchange, the observed past and predicted future rise in atmospheric CO2 causes a corresponding increase in seawater CO2 concentrations, [CO2], in upper ocean waters. Increasing [CO2] leads to considerable changes in the surface ocean carbonate system, resulting in decreases in pH and the carbonate concentration, [CO2−3]. These changes can be shown to have strong impacts on the marine biota. Here we will distinguish between CO2-related responses of the marine biota which (a) potentially affect the ocean's biological carbon pumps and (b) are relevant to the interpretation of diagnostic tools (proxies) used to assess climate change on geological times scales. With regard to the former, three direct effects of increasing [CO2] on marine plankton have been recognized: enhanced phytoplankton growth rate, changing elemental composition of primary produced organic matter, and reduced biogenic calcification. Although quantitative estimates of their impacts on the oceanic carbon cycle are not yet feasible, all three effects increase the ocean's capacity to take up and store atmospheric CO2 and hence, can serve as negative feedbacks to anthropogenic CO2 increase. With respect to proxies used in palaeo-reconstructions, CO2-sensitivity is found in carbon isotope fractionation by phytoplankton and foraminifera. While CO2- dependent isotope fractionation by phytoplankton may be of potential use in reconstructing surface ocean pCO2 at ancient times, CO2-related effects on the isotopic composition of foraminiferal shells confounds the use of the difference in isotopic signals between planktonic and benthic shells as a measure for the strength of marine primary production. The latter effect also offers an alternative explanation for the large negative swings in δ13C of foraminiferal calcite between glacial and interglacial periods. Changes in [CO2−3] affect the δ18O in foraminiferal shells. Taking this into account brings sea surface temperature estimates for the glacial tropics closer to those obtained from other geochemical proxies.

Beschreibung: High-resolution Nd- and Pb-isotope time series for the last 8 Myr are reported for four Atlantic ferromanganese crusts, dated by 10Be/9Be chronology. These are compared to new high-resolution and high-precision Pb-isotope time series and recently published Nd-isotope time series for two previously studied crusts from the NW Atlantic Ocean. These records allow a more detailed examination of Atlantic deepwater variability over the time period of intensification of Northern Hemisphere Glaciation (NHG). Changes in the Pb-isotope time series started after 3 Ma, but were most dramatic over the last 1.8 Myr, coinciding with changes of Pb-isotopes in the Arctic Ocean. This latter change post-dates the intensification of NHG at 3.1 to 2.5 Ma and reflects an increase in the input of material eroded from the Archean Shield of Canada and Greenland. Shifts in Nd- and Pb-isotope compositions in a crust from the Blake Plateau occur before ∼5 Ma and most prominent at ∼8 Ma suggest that water masses from either the Pacific or Southern Ocean influenced the isotope composition of this crust. The relatively high εNd values around 8 Ma recorded by the Blake Plateau crust are explained by a contribution of eastward flowing Pacific water through the Panama Gateway into the Caribbean Sea. This high εNd signal decreased between 8 and 5 Ma suggesting that the supply of Pacific water into the Caribbean became restricted. This is earlier than the Caribbean seawater salinity increase at 4.2 Ma deduced from δ18O data, and may indicate that there was only a surface water connection between the Caribbean and Pacific between ∼5 and 4.2 Ma. The closure of the Panama Gateway to intermediate and deep water exchange (〉200 m depth) apparently occurred much earlier than the intensification of Northern Hemisphere Glaciation at 3.1–2.5 Ma, and cannot therefore have been a direct cause of this climatic change, but may, as recently argued, only have been a necessary precondition

Beschreibung: Mixed methane–sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the Cascadia convergent margin. Vent fields from which methane-charged, low-salinity fluids containing sulfide, ammonia, 4He, and isotopically light CO2 escape are associated with these exposures. They characterize a newly recognized mechanism of dewatering at convergent margins, where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward. This process augments the convergence-generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate. Discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths. The enhanced turnover results from the oxidation of methane, hydrogen sulfide, and ammonia by vent biota. The injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide. A large fraction of the methane is oxidized within the water column and generates δ13C anomalies of the dissolved inorganic carbon pool.

Beschreibung: Water samples from surface and bottom waters of two bights of the Baltic Sea were analysed for dissolved and/or particulate concentrations of Al, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn, in addition to the main oceanographic variables, at 27 stations during six cruises between February 1990 and July 1992. The metal values show distinct regional differences, with maximum concentrations at the near-shore stations, The levels of total Hg exhibit a significant negative relationship with salinity. In surface layers, seasonal differences due to biogenic uptake of elements could not be detected for any of the dissolved metals. In bottom waters, however, summer-time concentrations of a number of metals are in clear excess of winter levels either due to diffusion of metals (Go, Fe, Mn) from the sediments under low-oxygen or anaerobic conditions, or due to mineralization processes (Cd, Zn) of recently sedimented biogenic particulates. With the exception of Fe and Pb, the particulate fractions are of minor importance, with slight variabilities between the seasons only. The K-D values (ratio between metal concentrations in the particulate and dissolved fractions) decrease by more than two orders of magnitude in the order Fe-Pb-Mn-Co-Zn-Cd-Cu-Ni. Finally, the results are discussed with regard to a trace metal monitoring programme in the area.

Beschreibung: The capture of 52 specimens of the cirrate octopod Grimpoteuthis glacialis (Robson, 1930), of dorsal mantle length 20-165 mm during a 1996 trawling survey near the Antarctic Peninsula allowed the basic biology of the species to be examined. Their presence in bottom trawls at depths of 333-879 m, but their absence from benthopelagic and pelagic trawls, is consistent with a primarily benthic habitat. The largest single sample, 40 animals, came from a soft mud bottom and highlights the patchy nature of the distribution. Males tended to be bigger in total length and mass than females of similar mantle length. The males, however, were mature at a smaller size. Mature males have tiny sperm packets, rather than typical cephalopod spermatophores, in their distal reproductive tract. Mature females have large, smooth eggs in the proximal oviduct, in the huge oviducal gland and in the distal oviduct. Eggs in the distal oviduct have a thick, sticky coating that hardens in seawater into a secondary egg case. Ovarian eggs vary greatly in size, possibly indicating protracted egg laying. Observations on live animals indicate that the species swims primarily by fin action, rather than by jetting or medusoid pulses with the arm/web complex. It may be capable of limited changes in colour pattern, especially on the oral surface of the web. Three pairs of surface structures that appear superficially to be white spots anterior to the eyes and near the bases of the fins are actually transparent patches in the skin. When considered in association with the transparent subdermal layer and the anatomy of the eyes, optic nerves and optic lobes, these clear patches seem to function in detecting unfocused light on the horizontal plane of the benthic animal.

Beschreibung: Hydrothermal activity in the Central Bransfield Basin revealed an active low-temperature vent field on top of a submarine volcanic structure. A temperature anomaly was detected and the sea floor showed various patches of white silica (opal-A) precipitate exposures and some yellow–brown Fe-oxyhydroxide crusts. Enriched dissolved methane concentrations were encountered. Sediment was near 24°C just after the grab came on deck. No dense population of chemosynthetically based macrofauna known from other hydrothermal venting areas was present, except for pogonophora. The observations suggest that the sedimented hydrothermal field at Hook Ridge is a low-temperature end-member branch from a deeper hydrothermal source.

Beschreibung: A seasonally-varying sedimentation pattern was observed for the alkenone flux measured with sediment traps in the northern North Atlantic. In the Norwegian Sea (traps were set at 500, 1000 and 3000 m) the alkenone flux varied between 0.1 and 7.1 μg m−2 d−1 and followed the seasonal pattern of the bulk parameters. Maximum fluxes occurred from mid-October until mid-November and were also high in May. A surprising result was that considerably higher particle fluxes were observed at 3000 m. For the alkenone flux, the highest additional input of 250% was observed during the period when sediment resuspension was greatest in summer. At the Barents Sea continental margin (traps at 1840 and 1950 m) the alkenone fluxes follow the sedimentation pattern of the bulk parameters, with a less visible signal of distinct seasonality observed in the 1950 m trap. The sedimentation of total alkenones varied between 0.8 and 144 μg m−2 d−1 at 1840 m and between 0.5 and 31.0 μg m−2 d−1 at 1950 m. Resuspension and lateral advection contributed significantly to measured fluxes in the two near-bottom traps. Alkenone concentrations were determined in faecal pellets of Appendicularia, ostracods and euphausids from selected samples at the Barents Sea site. The alkenone flux in pellets (4% to 24% of total) was 5 to 6 times higher at 1950 m depth than at 1840 m and the major part (77–78%) of the total flux of C37:3 reaching the near-bottom trap at 1950 m was associated with faecal pellets of the meso-zooplankton. Spatial and temporal variations of the U37k′ signals were observed, indicating that the imprint in the alkenone signal depends on the origin and transport pathway of the organic material. Strong deviations occur in areas where nepheloid layers contribute particles of long residence times to the primary flux.

Beschreibung: Investigations of factors affecting feeding success in fish larvae require knowledge of the scales of variability of the feeding process itself and the indices used to assess this variability. In this study, we measured short-term (diel) variability in feeding rates of wild haddock (Melanogrammus aeglifinus) larvae four times per day during a 10-d cruise in the northern North Sea. Feeding activity was evaluated using indices of gut fullness, prey digestive state and biochemical measurements (tryptic enzyme activity). The gut fullness and the enzyme activity indices indicated moderate to high rates of food consumption throughout the cruise. Time series analysis of the three indices showed significant diel variability in all indices and enabled identification of significant lags between food uptake and peak digestive enzyme activity. The typical pattern of food consumption and digestion was characterized by maximal ingestion of prey early in the evening (19:00 hrs) and peak digestive enzyme activity at 01:00 hrs. The time scale over which enzyme activities reacted to prey ingestion was ca. 6 h, and is consistent with expectations from controlled laboratory experiments with other larval fish species. Significant diel variability in tryptic enzyme activity suggests that attempts to relate this measure of feeding success to other variables (e.g. food concentrations) should take care to accommodate natural cycles in feeding activity before making statistical comparisons.

Beschreibung: Two newly designed underway systems for the measurement of CO2 partial pressure (pCO2) in seawater and the atmosphere are described. Results of an intercomparison experiment carried out in the North Sea are presented. A remarkable agreement between the two simultaneously measured (pCO2) data sets was observed even though the spatial variability in surface pCO2 was high. The average difference of all l -min averages of the seawater pCO2 was as low as 0.15 μatm with a standard deviation of 1.2 μatm indicating that no systematic difference is present. A closer examination of the profiles shows that differences tend to be highest during maxima of the pCO2 gradient (up to 14 μatm/min). The time constants of both systems were estimated from laboratory experiments to 45 s, respectively, 75 s thus quantitatively underlining their capability of a fast response to pCO2 changes

Beschreibung: While the aggregation and mass settlement of diatoms at the termination of blooms results in significant export of carbon from the surface ocean, the mechanisms of bloom aggregation have been poorly understood. The aggregation of a multispecies diatom bloom was investigated under controlled conditions in a 1200 liter, nutrient-enriched, laboratory mesocosm in order to elucidate the parameters sufficient to accurately predict bloom aggregation. A diverse bloom of diatoms dominated by several species of Chaetoceros and Thalassiosira progressed through a classic pattern of exponential, stationary, and senescent phases in the mesocosm. Aggregates larger than 0.5 mm became detectable on the eighth day after inoculation, and aggregates 〉1 mm increased exponentially from Day 10 onward producing the appearance of a mass aggregation event late on Day 10. The bloom aggregated sequentially with Thalassiosira dominating early aggregates and Chaetoceros dominating later ones. Chaetoceros resting spores formed only in aggregates. Aggregation was not linked to nutrient depletion or to the physiological state of the cells since the onset of aggregation and the mass aggregation event occurred 1 to 3 days prior to nutrient depletion and while carbon:nitrogen ratios of cells were still very low and growth rates high. Moreover, visible aggregates did not form in the mesocosm until cell abundances were considerably higher than abundances observed to aggregate in nature, suggesting that aggregation was not strongly linked to phytoplankton cell concentration. Complementary studies in this volume clarify the role of non-phytoplankton particles in aggregation of the mesocosm bloom. The mesocosm approach proved highly effective in producing an aggregating diatom bloom under controlled conditions.

Beschreibung: The gene coding for the anion-specific porin of the halophilic eubacterium Ectothiorhodospira (Ect.) vacuolata was cloned and sequenced, the first such gene so analyzed from a purple sulfur bacterium. It encodes a precursor protein consisting of 374 amino acid (aa)-residues including a signal peptide of 22-aa residues. Comparison with aa sequences of porins from several other members of the Proteobacteria revealed little homology. Only two regions showed local homology with the previously sequenced porins of Neisseria species, Comamonas acidovorans, Bordetella pertussis, Alcaligenes eutrophus, and Burkholderia cepacia. Genomic Southern blot hybridization studies were carried out with a probe derived from the 5′ end of the gene coding for the porin of Ect. vacuolata. Two related species, Ect. haloalkaliphila and Ect. shaposhnikovii, exhibited a clear signal, while the extremely halophilic bacterium Halorhodospira (Hlr.) halophila (formerly Ect. halophila) did not show any cross-hybridization even at low stringency. This result is in good accordance with a recently proposed reassignment within the family Ectothiorhodospiraceae, which included the separation of the extremely halophilic species into the new genus Halorhodospira.

Beschreibung: Facies analysis, fossil dating, and the study of the metamorphism in the Late Triassic to Early Cretaceous sedimentary successions in the central part of the Northern Calcareous Alps allow to reconstruct the tectonic evolution in the area between the South Penninic Ocean in the northwest and the Tethys Ocean with the Hallstatt Zone in the southeast. The Triassic as well as the Early and Middle Jurassic sediments were deposited in a rifted, transtensive continental margin setting. Around the Middle/Late Jurassic boundary two trenches in front of advancing nappes formed in sequence in the central part of the Northern Calcareous Alps. The southern trench (Late Callovian to Early Oxfordian) accumulated a thick succession of gravitatively redeposited sediments derived from the sedimentary sequences of the accreted Triassic–Liassic Hallstatt Zone deposited on the outer shelf and the margin of the Late Triassic carbonate platform. During a previous stage these sediments derived from sequences deposited on the more distal shelf (Salzberg facies zone of Hallstatt unit, Meliaticum), and in a later stage from more proximal parts (Zlambach facies zone of Hallstatt unit, Late Triassic reef belt). Low temperature–high pressure metamorphism of some Hallstatt limestones before redeposition is explained by the closure of parts of the Tethys Ocean in Middle to Late Jurassic times and associated subduction. In the northern trench (Late Oxfordian to Kimmeridgian) several hundred meters of sediment accumulated including redeposited material from a nearby topographic rise. This rise is interpreted as an advancing nappe front as a result of the subduction process. The sedimentary sealing by Tithonian sediments, documented by uniform deep-water sedimentation (Oberalm Formation), gives an upper time constraint for the tectonic events. In contrast to current models, which propose an extensional regime for the central and eastern Northern Calcareous Alps in the Late Jurassic, we propose a geodynamic model with a compressional regime related to the Kimmerian orogeny.

Beschreibung: This note describes a method for the determination of the age of individual water mass contributions in a mixture of water masses. The method is based on a combination of Optimum Multi parameter analysis and CFC analysis. Synthetic data designed to mirror the situation in the permanent thermocline of the eastern Indian Ocean are used to demonstrate the method. The feasibility of applications to oceanic data is discussed.

Beschreibung: Rubrik "Neues aus dem Geologenarchiv (1997)"

Beschreibung: We have employed electronmicroscopical methods (SEM, TEM) to document the microbial community associated with the marine sponge Aplysina cavernicola (formerly Verongia cavernicola, class Demospongiae). Five dominant bacterial types were identified, three of which resemble the morphotypes originally described by Vacelet (1975). One bacterial type possesses morphological properties that are characteristic of the genus Planctomyces. In addition, morphologically uniform bacteria which reside inside the nuclei of host cells were observed. Using in situ hybridization with fluorescently labelled rRNA probes directed against known bacterial groups, the phylogenetic affiliation of the mesohyl bacteria was assessed. It could be shown that the vast majority of mesohyl bacteria belongs to the domain Bacteria with a low GC content. Among the Bacteria, the delta-Proteobacteria were most abundant, followed by the gamma-Proteobacteria and representatives of the Bacteroides cluster. Clusters of Gram-positive bacteria with a high GC content were also found consistently in low amounts. No hybridization signal was obtained with probes specific to the domain Archaea, to the alpha- and beta-Proteobacteria and to the Cytophaga/Flavobacterium cluster. This study describes for the first time the application of the “top-to-bottom approach” using 16S rRNA probes and in situ hybridization to assess the microbial diversity in Aplysina sponges

Beschreibung: Controversy surrounding the mechanisms and controls on argon diffusion in K-feldspar has led us to undertake direct diffusion measurements on a crystal with simple microtextures, over a range of temperatures. Measurements of argon diffusion profiles in a gem-quality iron-rich orthoclase heated in a cold seal apparatus, have been undertaken in situ using an ultra-violet laser ablation microprobe (UVLAMP) technique. The results agree very closely with the previously determined bulk values for Benson Mines orthoclase (activation energy ( E)=43.8±1 kcal mol -1) and vacuum furnace cycle-heating studies of K-feldspars ( E=46±6 kcal mol -1). However, instead of defining a single activation energy ( E) and diffusion coefficient ( Do), the data yield two sets of parameters: a low-temperature (550-720°C) array with an E of 47.2±2.5 kcal mol -1 (198.2±10.5 kJ mol -1) and a Do of 0.0374 +0.1123-0.0281 cm 2 s -1, and a high-temperature (725-1019°C) array with an E of 63.8±3.4 kcal mol -1 (268.0±14.3 kJ mol -1) and a Do of 55.0 +225.5-44.2 cm 2 s -1. The new results closely reproduce two sets of apparent activation energies previously measured in cycle-heating studies of Madagascar K-feldspar (40±3 and 57±3 kcal mol -1). Previous interpretations of the two arrays have included multiple domains with variable activation energies and fast track diffusion. However, the UV depth profile analyses indicate simple diffusion to the grain surface and importantly, diffusion radii calculated by combining the UVLAMP and cycle-heating data, are the same as the physical grain sizes used in the experiments, around 1 mm. Vacuum furnace stepped heating experiments on slowly cooled K-feldspars have been interpreted as showing diffusion radii of around 6 μm and indicate complex populations of sub-grains. This study indicates that Madagascar K-feldspar and thus probably all gem-quality K-feldspars act as single diffusion domains and that short-circuit (or pipe) diffusion was not an important loss mechanism. An apparent diffusion compensation relationship in the stepped heating data for Madagascar K-feldspar implies that similar relationships seen in other K-feldspars are a result of a range of diffusion mechanisms.

Beschreibung: The pelagic nekton community was sampled with the RMT 25 opening/closing net and a neuston net at two stations in the Scotia Sea south of the Antarctic Polar Front in the open ocean (Station 1) and on the South Georgia northwestern slope (Station 2). Downward oblique tows were made with the RMT 25 through discrete 200 m layers to 1000 m in daylight and darkness. A total of 119 cephalopods representing nine species were removed from the samples, and mantle and arm lengths were measured to the nearest 0.1 mm. The most abundant species at each station was an undescribed Brachioteuthis sp. (B. ?picta). Galiteuthis glacialis and Alluroteuthis antarcticus were caught at both stations. Histioteuthis eltaninae, Bathyteuthis abyssicola and Psychroteuthis glacialis were caught at Station 1. Mastigoteuthis psychrophila and a Chiroteuthis sp. were caught at Station 2. B. ?picta was present throughout the water column to 1000 m at both stations, with little evidence of ontogenetic descent. There was evidence for ontogenetic descent in G. glacialis. This species was absent from the Antarctic Surface Water (ASW) at Station 1, where it was concentrated in the Circumpolar Deep Water (CDW). At Station 2 it was present throughout the water column to 1000 m. The other species were all caught in the core of the CDW (〉400 m). In juvenile B. ?picta, G. glacialis and A. antarcticus, growth of the brachial crown is positively allometric with respect to mantle length. Recent data on biomass spectra in high-latitude pelagic systems show that they are characterised by the presence of peaks of biomass separated by biomass minima. Positive allometric growth in the brachial crown of these antarctic oceanic squid is suggested to have evolved as an adaptation to the peaked, or domed, structure of the pelagic biomass spectrum which must be spanned by these predators as their optimum prey size increases with growth. Interspecific differences in the allometry of tentacle growth are probably related to differences in strategies for stalking and capture of prey.

Beschreibung: The late Eocene through Oligocene changes in the paleoceanography of the southernmost Indian Ocean have been reconstructed by means of a coarse fraction analysis of closely spaced samples (20 cm = about 20 kyr) from ODP Site 744, Kerguelen Plateau. Surface water productivity, reconstructed from accumulation rates of opal skeletons and benthic foraminifers is low in the early late Eocene, increases at about 36 Ma and shows a sharp increase to maximum values in the earliest Oligocene. In the early late Oligocene it decreases gradually to a minimum and increases again to a maximum in the latest Oligocene. Beside this general trend productivity varies in short-term cycles of a duration of about 400 kyr (340 kyr in the latest Oligocene) with maxima in productivity in warmer Oligocene periods. These productivity variations are reflected by strong variations in carbonate dissolution. Changes in bottom water mass chemistry have been deduced from the degree of carbonate dissolution and it's relation to productivity proxies. Following Kennett and Stott (1990), it is suggested that a proto-antarctic bottom water (proto-AABW) and an overlying warm, saline deep water (WSDW) from low latitudes shifted vertically and latitudinally with time and exerted their influence on the sediments of Site 744. Proto-AABW is detected by means of strong carbonate dissolution when productivity is low. WSDW is detected by means of an excellent carbonate preservation despite high productivity. Terrigenous material occurs as very coarse ice-rafted detritus (IRD) in the late Eocene (167–168.5 mbsf) and after a main shift in oxygen isotopes in the early Oligocene. Very low amounts of 40–125 μm sized mica and very few quartz grains occur only in high productivity periods and at the transition from low to high productivity periods. These occurrences are attributed to wind/current supply during warmer Oligocene intervals.

Beschreibung: The history of the Late Weichselian northwestern Barents Shelf, including western Svalbard, has been investigated by provenance/sedimentologist studies of five cores from the continental shelf and slope west of Svalbard. The chronostratigraphy of the cores is based on AMS 14C dates and oxygen isotope analyses. Interpretations of the cores suggest that the ice sheets of western Svalbard and northwestern Barents Sea experienced advances and retreats in two steps. The first significant ice advance beyond the present coastline occurred ca. 22,000 14C yr B.P. and was followed by an ice advance to the shelf edge ca. 18,000 14C yr B.P. Ice recession from the outer shelf and the southwestern Barents Sea began 14,800 14C yr B.P. and was followed by a second ice recession between 13,000 and 12,000 14 C yr B.P. during which ice withdrew from the inner shelf. A minor readvance of the ice sheet on the shelf west of Svalbard occurred close to 12,400 14C yr B.P. The first deglaciation event was associated with release of icebergs containing ice-rafted detritus, while the later episode also included significant amounts of meltwater and fine-grained sediment.

Beschreibung: Microfaunal studies of planktic foraminifera carried out on 21 sediment cores from the Norwegian-Greenland Sea (NGS) reveal the spatial and lateral distribution as well as meltwater implication of today's non-polar/subpolar species Beella megastoma (Earland). Previous findings are verified in that this foraminifera is characteristic only of the deglaciation phases of Termination II, III, and VI and not the ensuing interglacial optima, thus, rendering this species a ‘meltwater’ indicator. Its distribution is restricted to cores from the central, i.e., more ‘pelagic’, part of the NGS covering an area as far north as 77 ° latitude. A detailed investigation of Termination II indicates that B. megastoma first appeared in the southwest of the NGS at ~131 ka and then about 6 kyr later in the eastern and northern parts of the NGS. For the entire duration B. megastoma always coincided with the deposition of distinct ice-rafted detritus (IRD) suggesting the presence of drifting icebergs during this period. Two different oceanographic models, each with a two-stepped evolution of the post-Saalian surface water circulation, are proposed to account for this time transgressive character. The mechanism of brine formation as possible oceanic phenomenon forcing Atlantic water northwards is suggested for being responsible for the occurrence of B. megastoma in the NGS during early Termination II. The presence of B. megastoma always ceased with the culmination of the interglacial optimum, oxygen isotopic Substage 5.51 (Eemian), when the subpolar foraminiferal fauna reached highest abundances and a general lack of IRD is observed.

Beschreibung: Stable carbon and oxygen isotopes of the polar planktic foraminifera Neogloboquadrina pachyderma sinistral from sediment cores of the Norwegian Sea reveal several anomalous 13C and δ18O depletions in the surface water during the last glacial to interglacial transition and during the later Holocene. The depletions that are observed between the Last Glacial Maximum (LGM) and the end of the main deglacial phase were caused by massive releases of freshwater from thawing icebergs, which consequently resulted in a stratification of the uppermost surface water layer and a non-equilibrium between the water below and the atmosphere. At ~8.5 ka (14C BP) this strong iceberg melting activity ceased as defined by the cessation of the deposition of ice-rafted detritus. After this time, the dominant polar and subpolar planktic foraminiferal species rapidly increased in numbers. However, this post-deglacial evolution towards a modern-type oceanographic environment was interupted by a hitherto undescribed isotopic event (~7–8 ka) which, on a regional scale, is only identified in eastern Norwegian Sea surface water. This event may be associated with the final pulse of glacier meltwater release from Fennoscandia, which affected the onset of intensified coastal surface water circulation off Norway during a time of regional sea-level rise. All these data indicate that surface water changes are an integral part of deglacial processes in general. Yet, the youngest observed change noted around 3 ka gives evidence that such events with similar effects occur even during the later Holocene when from a climatic point of view relativelystable conditions prevailed.

Beschreibung: Past hydrothermal activity has been exarpined from the compositions of the bottom sediments adjoining the rift zone at 21 °S in the EPR. The dating studies have been performed using radiocarbon and nonequilibrium 230Th. Some 644 bottom-sediment samples were analyzed for 24 elements. About 40% of the variability is due to factors that reflect the hydrothermal activity. In the surface layer, the detailed distribution of fluxes of the main ore-forming elements Fe and Mn, Cu (an element of hydrogene-hydrothermal origin), and Ti (an element entering the sediments from bedrock weathering) were studied. The maximal fluxes for elements of hydrothermal origin occur at a considerable distance from the ridge axis, since hydrothermal elements entered the sediments only after the plume had broken up. Elevated concentrations of elements of edaphogene origin on the other hand adjoin the ridge axis. Using seven columns of bottom sediments with ages in the range from 24 to 340 thousand years, we analyzed the change with time in the. content of hydrothermal material and the fluxes of hydrothermal material and of Fe/Mn and 1 Ni. It is shown that the most effective indicator of change in hydrothermal activity on the moving floor is provided not by the flux of hydrothermal material but by its concentration and the Fe/Mn ratio. The cyclic nature of the hydrothermal process is most reliably indicated by the changes in concentration of the ore material, but only in columns near the source.

Beschreibung: Ice rafted debris in high latitude ocean sediments represent a complex record of the changing paleoenvironment of the oceans and, in particular, of the growth and decay of ice sheets along the margins of high latitudes. Physical properties measured on sediment cores taken from the Rockall Plateau were examined to determine the distribution of ice rafted debris layers and Heinrich events in the northeastern North Atlantic. These sediment core records may provide one of the keys to reconstruct the iceberg flow between the northeastern Atlantic and the Norwegian Sea. Magnetic susceptibility (MS) and Gamma Ray Attenuation Porosity Evaluator (GRAPE) density changes of these cores revealed that since about 65 ka, dropstone layers are recorded in both MS and GRAPE data of Rockall Plateau sediments. Rockall Plateau sediments show peaks in physical properties that correlate with Heinrich events (H1, H2, H4, H5, H6). Heinrich layer 3 was not observed. The stratigraphy and physical properties represent the Heinrich layers: H1 = 14–15 ka (MS = 52 μcgs, ϱ = 1.64 g/cm3), H2 = 23 ka (MS = 64 μcgs, ϱ = 1.8 g/cm3), H4 = 41 ka (MS = 53 μcgs, ϱ = 1.75 g/cm3), H5 = 50 ka (MS = 53 μcgs, ϱ = 1.75 g/cm3), H6 = 64 ka (MS = 100 μcgs, ϱ = 1.69 g/cm3). Heinrich events at Rockall Plateau sites point to a northward flow of icebergs in the northeastern Atlantic which may indicate a flow pattern to regions north of 54 °N.

Beschreibung: Single crystal ages of sanidine phenocrysts from pumice lapilli of the Late Glacial phonolitic Laacher See Tephra (East Eifel Volcanic Field, FRG) are determined by laser probe 40Ar/ 39Ar analysis. Sanidine megacrysts from the East and West Eifel (SAN6001, 410.4 ± 0.9 kyr; SAN6165, 469.8 ± 1.1 kyr) are applied as irradiation monitors, and their potential as Quaternary interlaboratory single crystal standards assessed. The apparent ages of Laacher See sanidine phenocrysts range from 6.4 ± 3.8 kyr to 127 ± 2 kyr (1σ), comprising up to four distinct subpopulations of crystals with individual ages, weighted mean apparent ages or isochron ages of 127 kyr, 55 kyr, 25 kyr and 12.9 kyr. The Laacher See Tephra 40Ar/ 39Ar eruption age is estimated as 12,900 ± 560 yr BP. Older crystals are interpreted as remnants of three earlier magma emplacement and crystallization events in the Laacher See magma system. These recycled, older crystals make up ca. 20% of the apparent juvenile sanidine phenocryst population in the essential phonolite clasts studied.

Beschreibung: An undisturbed 16 m late Pliocene-Pleistocene sediment core spanning 2.6 Myr of deposition was recovered from the Manihiki Plateau by the German research vessel Sonne in 1990. This core 34KL complements the heavily disturbed late Pliocene-Pleistocene core sections of DSDP Site 317, and is well suited for stratigraphic correlation. The sediments consist of calcareous microfossils (93–97% CaCO3), minor portions of siliceous microfossils and detrital minerals. All important calcareous microfossil zones could be identified and correlated with the magnetostratigraphic and isotope stratigraphic events, stages and periods. Due to the high degree of silica dissolution, the late Quaternary radiolarian Buccinosphaera invaginata Zone is the only siliceous fossil zone which could be identified. An interval with Globigerinoides gomitulus/pink was found within the middle Pleistocene which is clearly distinguished from the Globigerinoides ruber/pink interval of the late Pleistocene. The magnetostratigraphic Gauss-Matuyama and Matuyama-Brunhes boundaries as well as the Olduvai and Jaramillo events were clearly identified. The δ180 curve displays the 100 kyr (Milankovitch) and the 41 kyr (Laplace) cyclicity periods. The beginning of the Laplace Period and the last occurrence of the calcareous nannofossil Discoaster brouweri, which marks the end of the Pliocene, fall within the base of the Olduvai Event. There is also a marked drop in sedimentation rates around this time, which seems to be a regional phenomenon. Prominent 3.5 kHz subbottom reflectors at 8 ms and 15 ms reflection time are related to lithologic changes near the Mid-Pleistocene Revolution (MPR) and the beginning of the Laplace Period or the Pleistocene, respectively. It is possible to trace these reflectors laterally to the eroded eastern edge of the Manihiki Plateau where they can be tied to older strata.

Beschreibung: Four spicule-bearing chaetetid sponges are described from Upper Triassic (Norian) reef carbonates of the WesternTaurids (Antalya-Region, SW Turkey): Atrochaetetes alakirensisCuif & Fischer, Blastochaetetes dolomiticusBizzarini & Braga, Ptychochaetetes sp. and ?Bauneia sp.. Spicules are preserved as calcitic pseudomorphs. They are either short and thick or long and slender, corresponding to typical styles; oxes are rarely present in Atrochaetetes alakirensis. The styles are mainly embedded in the secondary rigid skeleton, but their rounded ends appear to be attached to the primary wall. In Blastochaetetes dolomiticus and ?Bauneia sp. styles are also embedded in the primary wall. A comparison of these spicule-skeletons with those of other chaetetids, especially Paleozoic species, confirms the polyphyletic origin of the Taxon Chaetetida.

Beschreibung: The main objective of this research paper is to estimate the new-ice production in the Laptev Sea flaw lead during the 1991/1992 winter season. A one-dimensional energy balance model was applied to calculate ocean-to-atmosphere heat flux and the resulting new-ice formation over open water. For a detailed estimate of regional ice production, the flaw lead was divided into 14 sections based on the analysis of NOAA-satellite images and Russian ice charts. Opening and maintenance of the lead sections are controlled by offshore winds, whereas closing of open water is caused by onshore winds. Since the orientation of the lead varies from section to section, the same regional wind forcing can cause different local lead behavior. Model results reveal that the seasonally accumulated thickness of new ice formed in the different lead sections—under the assumption of instantaneous lateral new-ice removal from the water surface—varies from 1.3 m to 13 m over temporarily open water and may reach 20 m over permanently open water. The corresponding ice volume produced in the sections varies between 3.4 km3 and 59 km3 and amounts to 258 km3 for the entire lead. The significant regional variations in new-ice production are due to differences in (i) the number of days that a lead section is open (open-lead days), (ii) the oceanic heat loss during open-lead days, and (iii) the areal extent of the lead sections. As compared to other studies,—at least during 1991/1992 winter season—the Laptev Sea flaw lead produced between 28 and 617% more initial sea ice than the Kara, Barents, East Siberian and Chukchi leads. Despite its limited areal extent of roughly 36,000 km2, which represents only 8% of the entire Laptev Sea, the flaw lead produces about 32% of the annual shelf ice. The ice production in the flaw lead is 5.3 times higher than the remainder of the shelf (7.4 m vs. 1.4 m). Furthermore, the Laptev Sea flaw lead produces 2.6% of the ice annually formed the entire Arctic Mediterranean Sea and contributes about 9% to the volume of the Siberian branch of the Transpolar Drift Ice System. This makes the Laptev Sea flaw lead a significant producer of Arctic sea ice on local and regional scales, whereas the contribution of lead ice to the entire volume of annually formed pack in high northern latitudes amounts only to roughly 1.3%.

Beschreibung: Rubrik "Neues aus dem Geologenarchiv (1994)": Da die Jahresversammlung 1995 in Bremen vor allem der Meeresgeologie gewidmet war, soll durch die Veröffentlichung eines im Archiv verwahrten Briefs zur Planung der ersten "Meteor"-Expedition an den Wiederbeginn der deutschen Hochseeforschung nach dem ersten Weltkrieg erinnert werden. Scon im Sommer 1919 wurden in der Admiralität der damaligen Reichsmarine Pläne erörtert, wie man wieder an die Tradition der Forschungsfahrten der Kaiserlichen Marine mit S.M.S.S. "Gazelle", "Planet" und "Möwe" anknüpfen könne. Ein 1915 vom Stapel gelaufenes Kanonenboot "Meteor" bot sich zum Ausbau als Forschungsschiff an (F. Spiess, 1928). Vorschläge für Forschungsfahrten wurnden von der Deutschen Seewarte und vom Berliner Institut für Meereskunde eingeholt. Dessen damaliger Direktor, der vor allem durch seine Eiszeitforschungen bekannt gewordene Geograph Geheimrat Professor Albrecht Penck (Leipzig 1858 - Prag 1945), legte daraufhin der Marineleitung eine Denkschrift seines Abteilungsvorstands Alfred Merz (Wien 1880 - Buenos Aires 1925) für eine dreijährige Expedition in den Pazifik vor. (Auszug)

Beschreibung: Sediment proxy data from the Norwegian, Greenland, and Iceland seas (Nordic seas) are presented to evaluate surface water temperature (SST) differences between Holocene and Eemian times and to deduce from these data the particular mode of surface water circulation. Records from planktic foraminiferal assemblages, CaCO3 content, oxygen isotopes of foraminifera, and iceberg-rafted debris form the main basis of interpretation. All results indicate for the Eemian comparatively cooler northern Nordic seas than for the Holocene due to a reduction in the northwardly flow of Atlantic surface water towards Fram Strait and the Arctic Ocean. Therefore, the cold polar water flow from the Arctic Ocean was less influencial in the southwestern Nordic seas during this time. As can be further deduced from the Eemian data, slightly higher Eemian SSTs are interpreted for the western Iceland Sea compared to the Norwegian Sea (ca. south of 70°N). This Eemian situation is in contrast to the Holocene when the main mass of warmest Atlantic surface water flows along the Norwegian continental margin northwards and into the Arctic Ocean. Thus, a moderate northwardly decrease in SST is observed in the eastern Nordic seas for this time, causing a meridional transfer in ocean heat. Due to this distribution in SSTs the Holocene is dominated by a meridional circulation pattern. The interpretation of the Eemian data imply a dominantly zonal surface water circulation with a steep meridional gradient in SSTs.

Beschreibung: The vestimentiferan tubeworm Riftia pachyptila derives most or all of its nutrition from intracellular chemosynthetic bacterial symbionts. Because purified preparations of symbionts respire nitrate, possibly nitrite, and oxygen, host transport of nitrate is a topic of interest. In the present study, we have developed a nitrate detection assay that utilizes a nitrite reductase-deficient Escherichia coli strain for the reduction of nitrate to nitrite, which is then determined spectrophotometrically. Nitrate and nitrite concentrations were measured in the blood and coelomic fluids of R. pachyptila collected from hydrothermal vent sites at 9°N and 13°N. The blood was shown to have nitrate concentrations up to one hundred times that of ambient sea water (40 μM). Blood nitrate levels reached concentrations of 〉1 mM, while nitrite was measured in the range of 400–700 μM. The concentrations of nitrate and nitrite in the coelomic fluids were 150–240 μM and 〈20 μM, respectively. The nitrate determination technique we present here is simple, applicable for laboratory and shipboard use on sea water or biological fluids, and works reliably within the 0.5 to 2000 μM range.

Beschreibung: Exposure of Fucus spiralis germlings to precise copper concentrations (0 to 844 nM Cu2+) in chemically defined medium demonstrated a relationship between urltrastructural changes and growth retardation with increasing copper concentration. Electron-translucent vesicles, present in ova, which normally disappear after fertilization, accumulated in germlings exposed to Cu2+ above 10.6 nM, suggesting that copper may inhibit a metabolic pathway involved in cell wall formation which is initiated by fertilization No membrane damage was observed during the exposure period. During a post-exposure period in copper-free medium, recovery occurred (rhizoid extension, apical hair formation) in germlings previously exposed to concentrations below 106 nM Cu2+ and electron-translucent vesicles became granular and disappeared. It is proposed that the electron-translucent vesicles contain a cell wall precursor and that copper inhibits its incorporation into the cell wall, preventing growth and development of the zygote.

Beschreibung: Eight techniques for cleaning particulate material and epibionts from the tissue of Fucus vesiculosus were tested on seaweed collected from a metal-contaminated estuary in the southwest of England. When assessed by scanning electron microscopy, only one was found to have efficiently removed the particulate material on the tissue. This technique consisted of applying a 1:9 ethanol:seawater mixture to the surface of the thallus, and scraping with a PTFE spatula. Analysis of Cu, As, Fe, Mn, and Zn content in the tissues cleaned by this technique showed that, in this case, only Fe concentrations decreased significantly when compared to tissue cleaned by rinsing in seawater only. The study is the first to systematically assess cleaning techniques for marine macroalgae and illustrates the need for standard methods for the sampling and analysis of seaweed tissue

Beschreibung: Variations in the speciation of iron in the northern North Sea were investigated in an area covering at least two different water masses and an algal bloom, using a combination of techniques. Catalytic cathodic stripping voltammetry was used to measure the concentrations of reactive iron (FeR) and total iron (FeT) in unfiltered samples, while dissolved iron (FeD) was measured by GFAAS after extraction of filtered sea water. FeR was defined by the amount of iron that complexed with 20 μM 1-nitroso-2-napthol (NN) at pH 6.9. FeT was determined after UV-digestion at pH 2.4. Concentrations of natural organic iron complexing ligands and values for conditional stability constants, were determined in unfiltered samples by titration. Mean concentrations of 1.3 nM for FeR, 10.0 nM for FeT and 1.7 nM for FeD were obtained for the area sampled. FeR concentrations increased towards the south of the area investigated, as a result of the increased influence of continental run off. FeR concentrations were found to be enhanced below the nutricline (below ∼40 m) as a result of the remineralisation of organic material. Enhanced levels of FeT were observed in some surface samples and in samples collected below 30 m at stations in the south of the area studied, thought to be a result of high concentrations of biogenic particulate material and the resuspended sediments respectively. FeD concentrations varied between values similar to those of FeT in samples from the north of the area to values similar to those of FeR in the south. The bloom was thought to have influenced the distribution of both FeR and FeT, but less evidence was observed for any influence on FeR and FeD. The concentration of organic complexing ligands, which could possibly include a contribution from adsorption sites on particulate material, increased slightly in the bloom area and in North Sea waters. Iron was found to be fully (99.9%) complexed by the organic complexing ligands at a pH of 6.9 and largely complexed (82–96%) at pH 8. The ligands were almost saturated with iron suggesting that the ligand concentration could limit the concentration of iron occurring as dissolved species.

Beschreibung: Abundance, biofacies and ATP content of benthic foraminifera (〉63 μm) were studied in the Northeast Water (NEW) Polynya (77–81°N, 5–17°W) over the ice-free summer, 1993, to investigate how a polynya system might influence the underlying benthic community. In the living assemblage, distinguished by Rose Bengal staining, over 60 taxa could be identified. The biofacies identified was similar to that of other Arctic shelf habitats. Foraminifera were counted in 3 size fractions (63–125 μm, 125–250 μm and 〉250 μm), with 65% of the foraminifera occurring in the smallest size fraction (63–125 μm). Total abundances (〉63 μm) in the uppermost 1 cm averaged approximately 200 ind/10 cm3 and declined down-core, as did the number of species. Abundances and species composition correlated positively with sediment chlorophyll and ATP content, with maxima occurring in the shallower northern regions of the polynya, suggesting a general dependence on food. Foraminera biomass was estimated to be 0.1-0.3 g Corg/m2. Abundances, biomass and ATP content were comparable to ice-free, deep-sea regions in the Norwegian Sea. Temporal changes observed over a 2 month period at one location were difficult to distinguish from spatial and analytical variability. Contrary to expectations, growth was unpronounced at the community and at a species level, implying either a delayed response of the benthic foraminiferal community to food inputs from the overlying water column or the presence of biological limitations other than food, such as predation.

Beschreibung: Viable counts of aerobic and anaerobic chemotrophic sulphur-oxidizers as well as phototrophic sulphur bacteria were determined in sediment samples taken from two different areas along the Baltic Sea shore which were known to regularly develop sulphidic conditions. Depth profiles of bacterial cell counts were correlated with concentration profiles of chloride, sulphate, sulphide, nitrate and phosphate in the pore water of these sediments and with potential activities of nitrate reduction, thiosulphate transformation and sulphate formation. The data revealed a complex multilayered structure within the sediments. Sulphide was released into the water from sediments of both sampling areas, but it was found that light and the availability of oxygen significantly reduced this amount. In the highly reduced sediment at Hiddensee, the highest numbers of phototrophic and chemotrophic sulphur-oxidizers were found near the sediment surface. Therefore, it was concluded that the combined action of both groups of bacteria most efficiently oxidizes reduced sulphur compounds in the top layers of the sediments. Nitrate may replace oxygen as final electron acceptor and will support oxidation of sulphide, in particular when oxygen and light are limiting

Beschreibung: Colonization structures of the large parasitic foraminifer Hyrrokkin sarcophaga Cedhagen, 1994 on Lophelia pertusa, Acesta excavata and Delectopecten vitreus are described from a deep-water coral reef mound on the mid-Norwegian shelf at 240 to 300 m water depth. Hyrrokkin sarcophaga is the only epibiont which is capable of attaching itself on the soft tissue-protected coral skeleton where it tends to form clusters of 3 to 8 specimens close to the tentacles of Lophelia. The foraminifer excavates a pit up to 1.5 mm deep and etches a straight channel through the skeleton of the host which ends within the soft tissue. In contrast to Lophelia, infested bivalves show a strong wound repair reaction and seal the etched channels by intense calcification. The etching is only performed by adult specimens. Substrate pitting is considered to improve the attachment strength while boring enables the parasite to secure a persistent nutrient source.

Beschreibung: The present literature on biologically mediated fluxes from the benthic nepheloid layer (BNL) across the sediment-water interface into the sediment and vice versa is reviewed. The processes involved are categorised according to direct bioresuspension and biodeposition, i.e. direct interception of the animal with particles, and those effects, which are indirectly created by benthic organisms, e.g., changes of physical properties in the sediments, constructions like tubes and pits and the corresponding changes in hydrodynamic conditions. It is concluded that benthic organisms significantly increase the flux of particles across the interface and that the physically created fluxes are easily modified by a factor of 2 and more.

Beschreibung: Sediment cores containing up to twenty-five ash layers were taken at three sites close to Vesterisbanken Seamount in the Greenland Basin. These ash layers imply frequent eruptions of the volcano within the last 60 ka. The eruptions led to airborne transport and volcaniclastic turbidity flows which transported volcanic glassy and crystalline material from the volcano into the surrounding basin. During the eruption and the transport the glass and the crystal particles were mixed. The glasses range in composition between basanites and phonolites/benmoreites with MgO contents of 8 to 0.65%. The glass analyses follow a distinct trend of fractionation suggesting the crystallization of the phases olivine, clinopyroxene, plagioclase, kaersutite, Cr-spinel, Ti-magnetite and apatite. A strong zonation of clinopyroxene and kaersutite phenocrysts implies mixing processes in the magma system although the liquid compositions do not lie on mixing trends. A geochemical study of the bulk ashes shows that some ash layers possess distinct chemical compositions. The ashes are more evolved than the lavas of the volcano, suggesting fractionation of liquid from crystallized material during the eruption or transport of the ashes. Sixteen layers are statistically combined into four groups, of which several can be correlated from core to core reflecting individual eruptive events.

Beschreibung: Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (〈2µm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected.

Beschreibung: Stable isotope records of demosponges from the Caribbean and Coral Sea are described for the purpose of studying the influence of fossil fuel CO2 on the carbon isotopic composition of dissolved inorganic carbon (DIC) in surface water. The slow-growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in δ13CDIC from pre-industrial times (early 19th century) to the present. We observed similar shapes and ranges in δ13C curves measured on Caribbean specimens collected from water depths of 25, 84 and 91 m as well as a specimen collected in shallow waters off New Caledonia. The records reveal a highly significant correlation with atmospheric δ13CCO2. δ13CDIC values for Caribbean and Coral Sea surface waters were calculated using the δ13C sponge records. While δ13C of atmospheric CO2 decreased by about 1.4‰ from the early 19th century to 1990, δ13CDIC of Caribbean and Coral Sea surface waters decreased by 0.9±0.2‰ and 0.7±0.3‰, respectively. No isotopic equilibrium between surface water DIC and atmospheric CO2 was observed, either during the pre-industrial steady state or during the last 100 years. The lower amount of depletion in the surface water δ13CDIC with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water DIC. The lower δ13C decrease in the Coral Sea points to a stronger influence of the subsurface water source compared to the Caribbean.

Beschreibung: The record of glacier fluctuations in western Scandinavia, as reconstructed from continental data, has been correlated with records of ice-rafted detritus (IRD) from well-dated sediment cores from the Norwegian Sea covering the past 150,000 yr B.P. The input of IRD into the ocean is used as a proxy for ice sheet advances onto the shelf and, thus, for the calibration of a glaciation curve. The marine results generally support land-based reconstructions of glacier fluctuations and improve the time-control on glacial advances. The Saalian ice sheet decayed very rapidly approximately 125,000 yr B.P. In the Early Weichselian, a minor but significant IRD maximum indicates the presence of icebergs in isotope substage 5b (especially between 95,000 and 83,000 yr B.P.). Reduced amounts of calcareous nannofossils indicate that surface waters were influenced by meltwater discharges during isotope substages 5d and 5b. An extensive build-up of inland ice began again during isotope stage 4, but maximum glaciation was reached only in early stage 3 (58,000-53,000 yr B.P.). Marine sediments have minimum carbonate content, indicating strong dilution by lithogenic ice-rafted material. Generally, the IRD accumulation rate was considerably higher in stages 4-2 than in stage 5. A marked peak in IRD accumulation rates from 47,000 to 43,000 yr B.P. correlates well with a second Middle Weichselian ice sheet advance dated by the Laschamp/Olby paleomagnetic event. Minimum ice extent during the Ålesund interstade (38,500-32,500 yr B.P.) and several glacial oscillations during the Late Weichselian are also seen in the IRD record. Of several late Weichselian glacial oscillations on the shelf, at least four correspond to the North Atlantic Heinrich events. Ice sheet behavior was either coupled or linked by external forcing during these events, whereas internal ice sheet mechanisms may account for the noncoherent fluctuations.

Beschreibung: Data from sections across the Eurasian Basin of the Arctic Ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the Arctic Ocean and on sources of the deep waters of the Nansen, Amundsen and Makarov basins. Using salinity, H218O, and mass balances we estimate the river-runoff and the sea-ice melt water fractions contained in the upper waters of the Arctic Ocean and infer pathways of the river-runoff signal from the shelf seas across the central Arctic Ocean to Fram Strait. The average mean residence time of the river-runoff fraction contained in the Arctic Ocean halocline is determined to be about 11 to 14 years. Pacific water entering through Bering Strait is traced using silicate and its influence on the halocline waters of the Canadian Basin is estimated. Water column inventories of river-runoff and sea-ice melt water are calculated for a section just north of Fram Strait and implications of these inventories for sea-ice export through Fram Strait are discussed. Comparison of the ratios of shelf water, Atlantic water and the deep waters of the Arctic Ocean indicate that the sources of the deep and bottom waters of the Eurasian Basin are located in the Barents and Kara seas.

Beschreibung: Climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the Nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes. Combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice-rafted debris (IRD) allows separation of local and global effects and subdivision of the marine oxygen isotope events 6.2–5.4, which include the last interglaciation, into: (1) a meltwater phase after glacial stage 6, recorded by large amounts of IRD and low foraminiferal abundance, indicating surface water warming; (2) an IRD-free period with high deposition rates of subpolar foraminifera and other CaCO3pelagic components, recognized here as the “full” interglaciation; and (3) a phase with the recurrence of IRD and the demise of subpolar species. Comparison of ice-core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial Holocene were similar. The records show no significantly different variations in the proxy data. In contrast, the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions (Terminations I and II) that preceded these two interglaciations. These suggest that during Termination II the climatic evolution in the Nordic seas was less affected by abrupt changes in ocean–atmosphere circulation than during the last glacial to interglacial transition.

Beschreibung:  The reflectance of sediments (gray level) were measured on 11 sediment cores from the Norwegian–Greenland–Iceland Sea (Nordic seas). The analyzed time interval covers the past five glacial–interglacial cycles. Although the results demonstrate that the gray-level method has a potential for stratigraphic purposes, it is indicated that gray-level changes in the Nordic seas are not necessarily driven by variations in the content of biogenic calcite. A detailed comparison of gray-level values with contents of total CaCO3 (carbonate) and total organic carbon (TOC) reveals no overall causal link between these proxies. However, specific glacial core sections with layers containing organic-rich sediment clasts as a consequence of iceberg-rafting seem to correlate well with law gray-level values. Of those cores which show relatively high and comparable carbonate values in the last three main interglacial intervals (stages 11, 5.5, and 1), stage 11 is always marked by the highest gray-level values. A close inspection of the surface structure of the foraminiferal tests as well as the conduction of reflectance measurements on these tests leads to the conclusion that enhanced carbonate corrosion occurred during stage 11. The test corrosion not only affected the reflectance of the tests by making them appear whiter, it also seems responsible for the comparatively high gray-level values of the total sediment in stage 11. In contrast, the relatively low gray-level values found in stages 5.5, and 1 are not associated with enhanced test corrosion. This observation implies that variable degrees of carbonate corrosion can have a profound effect on total sediment reflectance.

Beschreibung: Short-term iron enrichment experiments were carried out with samples collected in areas with different phytoplankton activity in the northern North Sea and northeast Atlantic Ocean in the summer of 1993. The research area was dominated by high numbers of pico-phytoplankton, up to 70,000 ml−1. Maximum chlorophyll a concentrations varied from about 1.0 μg l−1 in a high-reflectance zone (caused by loose coccoliths, remnants from a bloom of Emiliania huxleyi) and about 3.5 μg l−1 in a zone in which the phytoplankton were growing, to about 0.5 μg l−1 in the northeast Atlantic Ocean. From the high-reflectance zone to the northeast Atlantic Ocean, nitrate concentrations increased from 0.5 μM to 6.0 μM. Concentrations of reactive iron in surface water showed an opposite trend and decreased from about 2.6 nM in the high-reflectance zone to 〈1.0 nM in the northeast Atlantic Ocean. In the research area, no signs of true iron deficiency were found, but iron enrichments in the high-reflectance zone, numerically dominated by Synechococcus sp., resulted in increased nitrate uptake. Ammonium uptake was hardly affected. Strong support for the effect of Fe on cell physiology is given by the increase in the f-ratio. Net growth rates of the phytoplankton (changes in cell numbers over 24 h) were almost unchanged. Phytoplankton collected from the northeast Atlantic Ocean, did not show changes in the nitrogen metabolism upon addition of iron. Net growth rates in these incubations were low or negative, with only slightly higher values with additional iron.

Beschreibung: Catalytic cathodic stripping voltammetry (CSV) preceded by adsorptive collection of complexes of 1-nitroso-2-napthol (NN) can be used to determine iron in seawater. It is shown here that iron(II) is effectively masked in the presence of 2,2-dipyridyl (Dp) so that iron(III) is measured selectively. The concentration of iron(II) is then calculated as the difference between the concentrations of reactive iron (Fe-R) in the absence and presence of 2 mu M Dp, Fe-R being defined as that which was complexed by 20 mu M NN at pH 6.9 in the presence of 1.8 mM H2O2 and 5 ppm sodium dodecyl sulphate. A 30 min reaction time was allowed for Dp to react with iron(II) in seawater prior to the determination of reactive iron(III) using the same conditions as used for Fe-R. Detection limits of 0.08 nM, 0.077 nM and 0.12 nM were obtained for Fe-R, iron(III) and iron(II), respectively, using a 60 s deposition time. The method was utilised to determine the redox speciation of iron in the northern North Sea. Concentrations of Fe-R ranged between 0.8 and 3.5 nM with nutrient-like depth profiles. Iron(II) was found to be present at concentrations up to 1.2 nM, the highest concentrations occurring in the upper 20 m of the water column.

Beschreibung: The mean pressures required to collapse gas vesicles in turgid cells of cyanobacteria from the Baltic Sea were 0·91 MPa (9·1 bar) in Aphanizomenon flos-aquae, 0·83 MPa in Nodularia sp. collected from the main deep basins and 0·34 MPa in Nodularia from shallower coastal regions. The gas vesicles were strong enough to withstand the depth of winter mixing, down to the permanent halocline (60 m in the Bornholm Sea, 90 m in the Eastern Gotland Sea) or to the sea bottom (30 m or less in the shallow Arkona Sea and Mecklenburg Bight). The cyanobacteria had low cell turgor pressures, within the range 0·08–0·18 MPa. The colonies were highly buoyant: the Aphanizomenon colonies floated up at a mean velocity of 22 m per day and the Nodularia colonies at 36 m per day. The colonies remained floating when up to half of the gas vesicles had been collapsed. In summer the cyanobacteria were mostly restricted to the water above the thermocline and in calm conditions their concentration increased towards the top of the water column. A series of colony concentration profiles indicated that, following a deep mixing event, the population of colonies moved upward with a net velocity of 22 m per day, similar to the colony floating velocity. This demonstrated that the buoyancy provided by gas vesicles would give a selective advantage to populations of cyanobacteria by enabling them to float into the higher irradiance of the near-surface water.

Beschreibung: The widespread view that scleractinian corals in cold and deep waters of high latitudes are slow growing organisms that do not form reefs is challenged by the discovery of a huge coral reef over 13 km in length, 10 to 35 m in height and up to 300 m in width formed by the coral Lophelia pertusa in water depths of 270 to 310 m at 64°N on the Sula Ridge, Mid-Norwegian Shelf. Cruises in 1994, 1995 and manned submersible operations in May 1997 provide data and observations from which the structure and development of the Sula Ridge coral reef have been determined. The Fennoscandian icesheet retreated from the Mid-Norwegian shelf prior to 12,000 years before present and modern oceanographic conditions were established at 8000 years before present. Coral growth since that time has resulted in a large deep-water shelf reef for which recent stable isotopic studies have demonstrated high growth rates for these azooxanthellate cold-water corals. Information on the geometry of deep-water coral reefs and their environmental controls is still fragmentary, controversial and raises issues of conservation in this area of active fishing and oil exploration. This paper reports on the discovery of what is probably one of the largest deep-water coral reefs existing in the northeast Atlantic and indicates that its siting is due to post-glacial structures (iceberg plough marks), events (the second Storegga Slide) and local conditions on the seafloor. Surprisingly, reef accumulation rates on the Sula Ridge are comparable with those measured on tropical coral reefs.

Beschreibung: An ultra-violet laser ablation microprobe (UVLAMP) has been applied for the first time to investigate argon partition coefficients for olivines and clinopyroxenes grown from silicate melts at 1 bar argon pressure. These preliminary measurements yield crystal/melt partition coefficients ranging from 0.138 (±0.01) to 0.013 (±0.003) for olivine and 0.589 (±0.003) to 0.0016 (±0.0005) for clinopyroxene. The higher values may indicate sub-microscopic melt inclusions, or some other heterogeneous distributions of `non-equilibrium' argon in the crystals. The lower values are probably more representative of true partition coefficients and fall at least an order of magnitude below the previously reported experimental data. The possibility of anomalous, high argon contents for crystals in previous studies is discussed in terms of surface adsorption, `trapped' argon and early partial melting.

Beschreibung: Detailed investigations have been made of two amphibole samples where 40Ar/39Ar age spectra have been interpreted to show argon diffusive loss. Both samples display complex compositional zoning that reflects partial major and minor element chemical re-equilibration during later thermal events that is associated with the loss of radiogenic 40Ar. The apparent diffusive loss age spectra in these samples are an artefact of this chemical re-equilibration process. One sample additionally shows the effect of potassium gain and contamination with a potassium-rich phase (biotite). The resulting ages in this sample are geologically meaningless and the apparent fit to a theoretical diffusive loss curve is coincidental. This study shows that volume diffusive loss of argon appears to operate at slower rates than argon loss by chemical re-equilibration in amphiboles.

Beschreibung: We provide evidence that the symbiosis of fungal endophyte and plant host should only be defined in the broad sense as originally used by De Bary to mean the living together of organisms of different species. Using endophytic fungi that were isolated from healthy plant tissue,- we tested for the potential pathogenicity of the fungal isolates and did physiological experiments to understand the endophyte-host association. Due to the variability of the interaction with respect to the role of the endophyte and with respect to the physiological Status of both partners, only a definition of symbiosis that does not specify the advantages and disadvantages for the individual partners can accurately describe this interaction.

Beschreibung: The late Quaternary sedimentary history of the continental margin off Portugal was reconstructed from sediment gravity cores. Hemipelagic sedimentation (lithofacies A) was dominant during glacial times. It was interrupted periodically by deposition of shelf- and upper-slope-derived silty and sandy terrigenous material by dilute turbidity currents (lithofacies B and C), ice-rafted debris during distinct periods of breakdown of North Atlantic ice sheets (Heinrich events, lithofacies D) and large amounts of pteropods (lithofacies F). Settling of biogenic particulate material (lithofacies E) prevailed during the Holocene, when sea level and sea surface temperatures were high and terrigenous shelf-input was low. Downslope transport was dominant on the northern part of the Portuguese margin, culminating in frequent turbidity current transport between 35 and 70 ka. This may be due to a humid climate and a high fluvial input. Pteropod muds are confined to cores south of 41°N. Prominent peaks in pteropod concentration were radiocarbon dated at 17.8 and 24.6 ka. Layers rich in ice-rafted debris (IRD) were found along the entire margin. The base of these layers have been dated at 13.6–15.9 14C ka, 21.0–22.0 14C ka, 33.8 14C ka and ±64.5 ka, which correspond well with the ages of Heinrich events 1, 2, 4 and 6 in the central North Atlantic. Heinrich events 0 (10.5 ka), 3 (27 ka) and 5 (50 ka) rarely influenced sedimentation on the Portuguese slope. A mineralogical study of the IRD within Heinrich layers suggests that most icebergs were derived from the Laurentide Ice Sheet in the Hudson Strait and Hudson Bay area through the Labrador Current and the Canary Current and flowed in a southward direction along the margin. IRD from European ice sheets may have been mixed in during Heinrich event 6. On their way along the margin the icebergs lost much of their sediment load due to melting of the ice in a progressively warmer climate. The southernmost latitude studied (37°N) may be close to the southeastern extension of iceberg transport during Heinrich events.

Beschreibung: The photoactive yellow protein of Ectothiodospira halophila (PYP) was purified to homogeneity by an advanced method and applied as an affinity ligand for the isolation of an anti-PYP IgG fraction which was used for immunoscreening. The distribution of proteins immunologically related to PYP was investigated in protein fractions of 51 strains from 38 species of non-halophilic and halophilic phototrophic and chemotrophic eubacteria and archaeobacteria. Strong immunoreactive bands indicating the presence of authentic PYP on Western blots (apparent mass 17.8 kDa) was only found in the strains of E. halophila. Additionally, two soluble proteins of Chromatium salexigens and Rhodospirillum salexigens (apparent molecular masses 16.4 and 19 kDa, respectively) cross-reacted to approx. 6% and 4%. Analyses of cell fractions of E. halophila revealed that PYP is a cytoplasmic protein.

Beschreibung: The late Eocene through Oligocene changes in the paleoceanography of the southernmost Indian Ocean have been reconstructed by means of a coarse fraction analysis of closely spaced samples (20 cm = about 20 kyr) from ODP Site 744, Kerguelen Plateau. Surface water productivity, reconstructed from accumulation rates of opal skeletons and benthic foraminifers is low in the early late Eocene, increases at about 36 Ma and shows a sharp increase to maximum values in the earliest Oligocene. In the early late Oligocene it decreases gradually to a minimum and increases again to a maximum in the latest Oligocene. Beside this general trend productivity varies in short-term cycles of a duration of about 400 kyr (340 kyr in the latest Oligocene) with maxima in productivity in warmer Oligocene periods. These productivity variations are reflected by strong variations in carbonate dissolution. Changes in bottom water mass chemistry have been deduced from the degree of carbonate dissolution and it's relation to productivity proxies. Following Kennett and Stott (1990), it is suggested that a proto-antarctic bottom water (proto-AABW) and an overlying warm, saline deep water (WSDW) from low latitudes shifted vertically and latitudinally with time and exerted their influence on the sediments of Site 744. Proto-AABW is detected by means of strong carbonate dissolution when productivity is low. WSDW is detected by means of an excellent carbonate preservation despite high productivity. Terrigenous material occurs as very coarse ice-rafted detritus (IRD) in the late Eocene (167–168.5 mbsf) and after a main shift in oxygen isotopes in the early Oligocene. Very low amounts of 40–125 μm sized mica and very few quartz grains occur only in high productivity periods and at the transition from low to high productivity periods. These occurrences are attributed to wind/current supply during warmer Oligocene intervals.

Beschreibung: High resolution interdisciplinary analyses of the clay and coarse (〉40 μm) fractions of ODP Leg 113 Site 690 Eocene-Oligocene sediments on the flank of the Maud Rise, provide information on paleoproductivity, water masses, paleoclimate and erosion in the Antarctic range as well as on the cyclicity of these processes. Three time intervals are distinguished: 1. (1) The middle Eocene, characterized by (a) nearly pure smectites, (b) productivity varying between relatively high values in the 42–44 Ma interval to very low values after 42 Ma, and (c) cyclic variations which correspond to changes in clay mineral associations. A warm saline deep water mass is inferred to have protected carbonate shells against dissolution at Site 690. We interpret the abundant mica in the coarse fraction as distributed by intermediate currents. 2. (2) The latest middle Eocene-late Eocene, characterized by low productivity values increasing with time. Kaolinite and illite concentrations also increase. Since the middle/late Eocene boundary mixing in the water column, which starts during a cooling event, causes similar clay mineral assemblages at Site 690 and at Site 689 on top of Maud Rise. 3. (3) The Oligocene, separated from the Eocene by a hiatus, is characterized by high productivity, highly increased amounts of illite and other minerals originating from erosion and physical weathering of Antarctica, and by cyclic variations of clay mineral indices which appear to be synchronous with productivity variations with a 400–450 kyr cyclicity. Six periods of strong carbonate dissolution associated with low productivity levels are attributed to incursions of cold carbonate aggressive bottom water of a “Proto-AABW” type.

Beschreibung: The concept of sequence-stratigraphy uses the stratal geometries at the margins of carbonate platforms to define depositional sequences and systems tracts. The aim of this study was to research if prograding, purely aggrading and retrograding phases of a Cretaceous carbonate platform showed differences in the composition and facies type of the slope sediments. The Vercors Plateau in SE France provides excellent outcrops to study this relationship. Continuous exposure of the platform-to-basin transition allowed direct examination of the margin geometries. Five successions were measured and sampled in great detail. Samples were thin-sectioned and point-counted, using point-count groups characterizing palaeoenvironments along the platform-to-basin transect. The composition logs as well as the numerical analysis of the point-count data, both show a clear relationship between grain composition and stratal geometry. The prograding and purely aggrading intervals are similar in composition, as they are both relatively coarse grained, and enriched in platform biota and limeclasts. Retreating units are relatively fine grained and rich in basinal grains (small benthic foraminifers, sponge spicules), non-carbonate grains and embedding material. These observations suggest that the retreating intervals represent incipient drownings of the platform. However, rather than distinctly separated groups the different phases of platform development form a continuous range of variation between high platform input and high basinal input. Compared to the prograding units the purely aggrading intervals are relatively rich in peloids, which may be suggestive of relatively low-energy conditions on the platform during aggradation. The compositional analysis also revealed significant variation in the frequency of ooids, but these variations showed no relationship with the progradation, aggradation or retreat of the platform.

Beschreibung: Seismic profiles from a venting area on the western margin of Paramushir Island (Sea of Okhotsk) reveal a local complex structure and an interesting, unusual pattern of the bottom simulating reflector (BSR). The BSR is gradual rising towards the venting area. The geothermal gradient and the bottom temperature confirmed the methane hydrate. The temperature appears to be the most important factor controlling the hydrate stability. A locally higher heat flow caused the upward migration of the hydrate stability field and the subsequent degradation of the hydrated sediments, causing gas vent formation and the flux of methane gas into the water column.