ALBERT

Description: The monograph introduces the reader to the world of inductive well logging - an established method for surveying the electrical conductivity of rocks surrounding a borehole. The emphasis is on developing a theory of inductive logging and on understanding logging tools basic physics, since this theory and understanding furnish valuable insights for inventing practical induction logging techniques. The first chapter of the book presents the basic laws of electromagnetism from a point of view that will facilitate the application of the theory to problems in electromagnetic logging. Many topics that play an important role in the design and interpretation of tools readings are covered. The vertical resolution and radial depth of investigation of different induction tools is systematically considered. Special attention is paid to principles of induction logging with transversal induction coils, to transient method of induction logging in media with cylindrical and horizontal interfaces and to the influence of anisotropy on the electromagnetic field measured in a conducting medium. Multi-coil differential induction probes and induction logging based on measuring the inphase component of the secondary field or the quadrature component difference are also described in detail. The last chapter is devoted to mathematical modeling of the response of induction logging tools in 3D geometries. The theory of inductive logging presented in this volume can be applied to logging after drilling as well as logging while drilling. Introduction. 1. Basic electromagnetic laws and Maxwell's equations. 2. Electromagnetic field of the magnetic dipole in a uniform conducting medium. 3. Methods for the solution of direct problems of induction logging. 4. Electromagnetic field of a vertical magnetic dipole on the axis of a borehole 5. Quasistationary magnetic field of a vertical magnetic dipole in a formation with a finite thickness. 6. The two-coil induction probe on the borehole axis, when the bed has a finite thickness. 7. Multi-coil dioeerential induction probes. 8. Induction logging based on measuring the inphase component of the secondary field or the quadrature component difference of type Q Hz(omega1) - omega1/omega2 Q Hz(omega2). 9. Transient induction logging. 10. Principles of induction logging with transversal induction coils. 11. The influence of anisotropy on the field of the magnetic dipole in a conducting medium. 12. Mathematical modeling of the response of induction logging tools in 3D geometries.

Description: High concentrations of free C32 bis-homohopanoic acids (up to 433 μg/g dry wt) occur in microbial mats at methane seeps in anoxic Black Sea waters. These compounds show a strong preference for the ‘geological’ 17α(H),21β(H)- over the ‘biological’ 17β(H),21β(H)-configuration (αβ/ββ ratios up to 30.7) and indicate the potential formation of αβ-hopanoids in modern environments. Strong 13C-depletions (δ13C as low as −78.4‰ PDB) indicate an in situ generation of these hopanoids by biota involved in the anaerobic cycling of methane carbon. The inferred presence of hopanoids indigenous to a permanently anoxic marine environment is significant because these lipids are not known to occur in strictly anaerobic bacteria.

Description: The 14C-dating of microbial carbonate structures growing at methane seeps in anoxic waters of the Black Sea has shown a gradual increase with depth of the age of carbonates of these buildups. Comparing the radiocarbon age of the base and middle parts of the microbial structures gives an approximate time of origin of the deepest and shallowest microbial buildups as about 5300 and 2900 years before present, respectively. These dates correspond to the first appearance of hydrogen sulfide in the deepest Black Sea waters and to the stabilization of the upper boundary of the anoxic zone around the present-day level.

Description: Since the early 1970s, marine chemists have gained a first-order understanding of the concentrations, distributions, and chemical behaviors of trace metals in seawater. Important factors initiating this quantum leap in knowledge were major advances in modern analytical chemistry and instrumentation, along with the development and adoption of clean techniques. An instrumental development in the mid-1970s that spurred the early research on trace metals was the availability of the sensitive graphite furnace as the sample introduction system to an atomic absorption spectrometer. More recently, the appearance of inductively coupled plasma (ICP) mass spectrometers has provided an even more sensitive and powerful instrumental capability to the arsenal of marine chemists. In addition to these instruments back in shore-based laboratories, there has been the development of sensitive shipboard methods such as stripping voltammetry and flow injection analysis (FIA) systems with either chemiluminescence or catalytically enhanced spectrophotometric detection. Along with the development of these highly sensitive analytical techniques came a recognition and appreciation of the importance of handling contamination issues by using clean techniques during all phases of sampling and analysis. This is necessary due to low concentrations of trace metals in seawater relative to the ubiquitousness of metals on a ship or in a laboratory (e.g., dust, steel hydrowire, rust, paint with copper and zinc antifouling agents, brass fittings, galvanized material, sacrificial zinc anodes, etc.). As a result, seawater concentrations of most trace metals have now been accurately determined in at least some parts of the oceans, and their oceanic distributions have been found to be consistent with oceanographic processes.The concentrations and distributions of trace metals in seawater are controlled by a combination of processes. These processes include external sources of trace metals delivered by rivers along ocean boundaries, by wind-blown dust from arid and semi-arid regions of the continents, and by hydrothermal circulation at mid-ocean ridges. Processes removing trace metals from seawater include active biological uptake or passive scavenging onto either living or nonliving particulate material. Much of this particulate material (along with its associated trace metals) is internally recycled either in the water column or in surficial sediments. The ultimate sink of trace metals is generally marine sediments. These various sources and sinks are superimposed on the general circulation and mixing of the oceans, resulting in the characteristic distributions of each trace metal. One of the first examples of the emergence of oceanographically consistent vertical profiles was for the trace-metal cadmium (Boyle et al., 1976; Martin et al., 1976; Bruland et al., 1978a). These studies demonstrated that the distribution of dissolved cadmium in the sea follows a pattern similar to that of the nutrients phosphate and nitrate. Sparked by these surprising results, several investigators during the following two decades were able to obtain excellent data sets on a wide variety of trace metals. This chapter will attempt to provide a basic overview of what is known about the controls of the concentrations and distributions of trace metals in the open ocean. Subtleties in their distributions will not be presented. The distributions of trace metals in coastal regions are more dynamic and complicated and will not be discussed in this chapter.The bulk of the data for vertical profiles of trace metals in seawater are from papers published in the 1980s and 1990s and most of the profiles are from either the North Pacific or North Atlantic. There is a paucity of vertical profiles from the South Atlanticand South Pacific. It has recently been argued that a new "GEOSECS"-type trace-metal program needs to be in place in order to provide appropriate global coverage of trace metals. Much of the impetus for such a program comes from the recognition of iron as an important micronutrient influencing global biogeochemical cycles in the oceans (Moore et al., 2002) and the potential role of other trace metals such as zinc. In particular, there is a pressing need for an expansion of the global database of dissolved iron distributions in the oceans. These measurements are needed to both initiate and verify models and to identify processes not contained in existing models.There have been a number of reviews of trace elements in seawater that form a foundation for this chapter. Among them are: Bruland (1983) on oceanographically consistent data sets; Burton and Statham (1990) on trace metals in seawater; and Donat and Bruland (1995) on trace elements in oceans. There are two reviews that deal with more of the biological role of trace metals: Bruland et al. (1991) on interactive influence of bioactive trace metals on biological production in ocean waters; and Hunter et al. (1997) on biological roles of trace metals in natural waters. A highly complementary chapter in this Treatise that deals with the influence of essential trace metals on biological processes has been written by Morel et al. (Chapter 6.05). Turning to "on-line" sources of information, Nozaki has done an excellent job perusing the available literature and compiling vertical profiles from the North Pacific for each element in a periodic table that makes an excellent figure (http://www.agu.org/eos_elec/97025e.html). Ken Johnson, a marine chemist at the Monterey Bay Aquarium Research Institute (MBARI), has a web site with a periodic table of the elements containing a brief review of information on each element (http://www.mbari.org/chemsensor/pteo.htm).

Description: This chapter discusses the chemical and biological aspects of melanin in condensed form. Melanin, the natural cosmetics of skin, hair, and feathers, represent broadly a group of natural and synthetic pigments of diverse origin and chemical functions. In nature, they usually occur in the form of insoluble fine granules accumulated in certain parts of animal and plant tissues. Some related synthetic melanins are also known. These are named after the compounds from which they were prepared via chemical and enzymatic oxidation, such as tyrosine-melanin, dopa-melanin, and catechol-melanin. The pigmentation of human skin has substantial protective, social, and cosmetic significance. Although melanins lack well-defined physical and spectral characteristics, they possess some effective chemical properties by acting as redox polymers, ion exchangers, and radical scavengers. The extensive studies of these chemical reactivities of melanin and putative melanin precursors have led researchers to infiltrate into many areas of scientific research, including the molecular biology of pigment-related genes.

Description: The Hamburg Ocean Primitive Equation model has undergone significant development in recent years. Most notable is the treatment of horizontal discretisation which has undergone transition from a staggered E-grid to an orthogonal curvilinear C-grid. The treatment of subgridscale mixing has been improved by the inclusion of a new formulation of bottom boundary layer (BBL) slope convection, an isopycnal diffusion scheme, and a Gent and McWilliams style eddy-induced mixing parameterisation. The model setup described here has a north pole over Greenland and a south pole on the coast of the Weddell Sea. This gives relatively high resolution in the sinking regions associated with the thermohaline circulation. Results are presented from a 450 year climatologically forced integration. The forcing is a product of the German Ocean Model Intercomparison Project and is derived from the European Centre for Medium Range Weather Forecasting reanalysis. The main emphasis is on the model's representation of key quantities that are easily associated with the ocean's role in the global climate system. The global and Atlantic northward poleward heat transports have peaks of 1.43 and 0.84 PW, at 18degrees and 21degrees N respectively. The Atlantic meridional overturning streamfunction has a peak of 15.7 Sv in the North Atlantic and an outflow of 11.9 Sv at 30degrees S. Comparison with a simulation excluding BBL shows that the scheme is responsible for up to a 25% increase in North Atlantic heat transport, with significant improvement of the depths of convection in the Greenland, Labrador and Irminger Seas. Despite the improvements, comparison with observations shows the heat transport still to be too weak. Other outstanding problems include an incorrect Gulf Stream pathway, a too strong Antarctic Circumpolar Current, and a too weak renewal of Antarctic Intermediate Water. Nevertheless, the model has been coupled to the atmospheric GCM ECHAM5 and run successfully for over 250 years without any surface flux corrections. (C) 2002 Elsevier Science Ltd. All rights reserved.

Description: A decrease in temperature (ΔT up to 45.5 °C) and chloride concentration (ΔCl up to 4.65 mol/l) characterises the brine–seawater boundary in the Atlantis-II, Discovery, and Kebrit Deeps of the Red Sea, where redox conditions change from anoxic to oxic over a boundary layer several meters thick. High-resolution (100 cm) profiles of the methane concentration, stable carbon isotope ratio of methane, and redox-sensitive tracers (O2, Mn4+/Mn2+, Fe3+/Fe2+, and SO42−) were measured across the brine–seawater boundary layer to investigate methane fluxes and secondary methane oxidation processes. Substantial amounts of thermogenic hydrocarbons are found in the deep brines (mostly methane, with a maximum concentration up to 4.8×105 nmol/l), and steep methane concentration gradients mainly controlled by diffusive flow characterize the brine–seawater boundary (maximum of 2×105 nmol/l/m in Kebrit Deep). However, locally the actual methane concentration profiles deviate from theoretical diffusion-controlled concentration profiles and extremely positive δ13C–CH4 values can be found (up to +49‰ PDB in the Discovery Deep). Both, the actual CH4 concentration profiles and the carbon-13 enrichment in the residual CH4 of the Atlantis-II and Discovery Deeps indicate consumption (oxidation) of 12C-rich CH4 under suboxic conditions (probably utilizing readily available—up to 2000 μmol/l—Mn(IV)-oxihydroxides as electron acceptor). Thus, a combined diffusion–oxidation model was used to calculate methane fluxes of 0.3–393 kg/year across the brine–seawater boundary layer. Assuming steady-state conditions, this slow loss of methane from the brines into the Red Sea bottom water reflects a low thermogenic hydrocarbon input into the deep brines.

Description: An α-spectrometric method for the rapid determination of radium isotopes (223Ra, 224Ra and 226Ra) in environmental samples is presented. Using EmporeTM Radium Rad Disks complete separation of the target radionuclides is achieved. The high selectivity of these Rad Disks allows the straightforward use of 225Ra as yield tracer. Chemical yield is up to 92±9%. The chemical procedure can be accomplished within 5 h. α-Sources show energy resolution in the range of typically 26–40 keV (FWHM). Despite minimal thickness of the sources no significant radon (Rn) losses can be observed.

Description: In the present work responses of carp (Cyprinus carpio) head kidney-derived neutrophils to the blood parasite T. borreli, and the consequences of these responses for parasite survival and other host response mechanisms, were studied. In co-cultures of head kidney leucocytes (HKL) with viable and lysed T. borreli a prominent shape change of neutrophilic granulocytes towards increased size and complexity was observed. In addition, the longevity of neutrophils in vitro was prolonged in the presence of T. borreli antigens. In these cultures, neutrophils also exhibited an increased phagocytosis activity. An up regulation of the production of nitric oxide (NO) and reactive oxygen species (ROS) was observed in T. borreli- and mitogen-stimulated HKL cultures. However, addition of live, fluorescence-labelledT. borreli to previously stimulated HKL cultures, revealed neither killing nor phagocytosis of the parasite by activated neutrophils. Moreover, viable T. borreli, when added to HKL cultures of infected carp, reduced their phagocytosis activity and NO production. Supernatants of co-cultures between T. borreli and HKL also contained mediators, which suppressed a mitogen-induced proliferative response of peripheral blood leucocytes (PBL) in vitro. Thus, while T. borreli itself appeared not to be sensitive to responses of activated neutrophils, the flagellates interferes with the production of immunomodulatory signals of these cells, probably resulting in a partial immunosuppression, which may favour the parasite development in vivo.

Description: A numerical model was applied to investigate and to quantify biogeochemical processes and methane turnover in gas hydrate-bearing surface sediments from a cold vent site situated at Hydrate Ridge, an accretionary structure located in the Cascadia Margin subduction zone. Steady state simulations were carried out to obtain a comprehensive overview on the activity in these sediments which are covered with bacterial mats and are affected by strong fluid flow from below. The model results underline the dominance of advective fluid flow that forces a large inflow of methane from below (869 mumol cm(-2) a(-1)) inducing high oxidation rates in the surface layers. Anaerobic methane oxidation is the major process, proceeding at a depth-integrated rate of 870 mumol cm(-2) a(-1). A significant fraction (14%) of bicarbonate produced by anaerobic methane oxidation is removed from the fluids by precipitation of authigenic aragonite and calcite. The total rate of carbonate precipitation (120 mumol cm(-2) a(-1)) allows for the build-up of a massive carbonate layer with a thickness of I m over a period of 20,000 years. Aragonite is the major carbonate mineral formed by anaerobic methane oxidation if the flow velocity of methane-charge fluids is high enough ( greater than or equal to10 cm a(-1)) to maintain super-saturation with respect to this highly soluble carbonate phase. It precipitates much faster within the studied surface sediments than previously observed in abiotic laboratory experiments, suggesting microbial catalysis. The investigated station is characterized by high carbon and oxygen turnover rates (approximate to1000 mumol cm(-2) a(-1)) that are well beyond the rates observed at other continental slope sites not affected by fluid venting. This underlines the strong impact of fluid venting on the benthic system, even though the flow velocity of 10 cm a(-1) derived by the model is relative low compared to fluid flow rates found at other cold vent sites. Non-steady state simulations using measured fluid flow velocities as forcing demonstrate a rapid respond of the sediments within a few days to changes in advective flow. Moreover, they reveal that efficient methane oxidation in these sediments prevents methane outflow into the bottom water over a wide range of fluid flow velocities (〈80 cm a(-1)). Only at flow rates exceeding approximately 100 cm a(-1), does dissolved methane break through the sediment surface to induce large fluxes of up to 5000 mumol CH4 cm(2) a(-1) into the overlying bottom water.

Description: This paper reviews major results of the recent German research priority program “Changes of the geo-biosphere during the last 15,000 years”, a contribution to PAGES focussing on changes of the geo-biosphere during the Weichselian Lateglacial. Different continental archives such as annually laminated lacustrine sediments, floodplain sediments, and speleothems were used to reconstruct environmental response to climatic changes and the Laacher See eruption event at ca 12,900 cal BP. Special emphasis is paid to establish a reliable time control using varve counting, high-precision radiocarbon dating of tree-ring series, and AMS radiocarbon dating of terrestrial plant macrofossils recovered from lacustrine sediments to correlate and synchronize large-scale environmental changes and events in central Europe.

Description: The sources of non-anthropogenic Pb in seawater have been the subject of debate. Here we present Pb isotope time-series that indicate that the non-anthropogenic Pb budget of the northernmost Pacific Ocean has been governed by ocean circulation and riverine inputs, which in turn have ultimately been controlled by tectonic processes. Despite the fact that the investigated locations are situated within the Asian dust plume, and proximal to extensive arc volcanism, eolian contributions have had little impact. We have obtained the first high-resolution and high-precision Pb isotope time-series of North Pacific deep water from two ferromanganese crusts from the Gulf of Alaska in the NE Pacific Ocean, and from the Detroit Seamount in the NW Pacific Ocean. Both crusts were dated applying 10Be/9Be ratios and yield continuous time-series for the past 13.5 and 9.6 Myr, respectively. Lead isotopes show a monotonic evolution in 206Pb/204Pb from low values in the Miocene (≤18.57) to high values at present day (≥18.84) in both crusts, even though they are separated by more than 3000 km along the Aleutian Arc. The variation exceeds the amplitude found in Equatorial Pacific deep water records by about three-fold. There also is a striking similarity in 207Pb/204Pb and 208Pb/204Pb ratios of the two crusts, indicating the existence of a local circulation cell in the sub-polar North Pacific, where efficient lateral mixing has taken place but only limited exchange (in terms of Pb) with deep water from the Equatorial Pacific has occurred. Both crusts display well-defined trends with age in Pb–Pb isotope mixing plots, which require the involvement of at least four distinct Pb sources for North Pacific deep water. The Pb isotope time-series reveal that eolian supplies (volcanic ash and continent-derived loess) have only been of minor importance for the dissolved Pb budget of marginal sites in the deep North Pacific over the past 6 Myr. The two predominant sources have been young volcanic arcs, one located in the northeastern part and one located in the northwestern part of the Pacific margin, from where material has been eroded and delivered to the ocean, most likely via riverine pathways.

Description: The Swatch of No Ground is a shelf canyon that deeply incises the Bengal shelf near the Ganges–Brahmaputra river mouth, cuts the foreset beds of the subaqueous river delta and acts as temporary depocenter between river mouth and Bengal fan. Sedimentation rates in the Swatch of No Ground are highest near the canyon head at ∼50 cm a−1, decreasing to ∼15 cm a−1 in 600 m water depth. The canyon deposits consist of intercalated fine (silt–clay) and coarse (silt–sand) grained deposits. In seismic profiles, small-scale sedimentary structures and parallel-bedded layers reveal that sediment in the canyon is mainly deposited from suspension. During fair weather conditions tidal currents are the dominant mechanism that transports plumes of suspended river load towards the canyon, forming fine-grained silt–clay layers. During storm conditions, sediment is resuspended on the inner shelf and subaqueous delta east of the canyon. Storm-generated bottom currents transport the resuspended sediment alongshelf to the canyon where the particles are trapped and form graded coarse silt–sand layers. Channels and gullies in the Swatch of No Ground indicate active gravity-driven currents with an erosional character in the upper canyon and non-depositional character below ∼450 m, suggesting that persistent or ephemeral currents presently export sediment to the Bengal fan. Numerous slumps and slides observed in the canyon show small-scale acoustically transparent layers that indicate sediment liquefaction presumably initiated along the steep canyon margin. These mudflows move downslope and halt where the canyon gradient decreases. One widespread acoustically transparent layer with an age of approximately 140–160 years BP can be traced throughout much of the canyon and is probably the result of large-scale sediment remobilization triggered by a catastrophic event like an earthquake. This may represent decennial-to-centennial scale events that remove large quantities of sediment and prevent the canyon from rapid infilling.

Description: This paper is an observational study of small-scale coherent eddies in the Labrador Sea, a region of dense water formation thought to be of considerable importance to the North Atlantic overturning circulation. Numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat, yet their small size has hindered observational progress. A large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms, current meter moorings and satellite altimetry. Details of the current and water mass structure of individual eddy events, as they are swept past by an advecting flow, can then be extracted from the mooring data. A transition is seen during mid-1997, with long-lived boundary current eddies dominating the central Labrador Sea year-round after this time, and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time. The TOPEX / Poseidon altimeter covers the Labrador Sea with a loose “net” of observations, through which coherent eddies can seem to appear and disappear. By concentrating on locating and describing anomalous events in individual altimeter tracks, a portrait of the spatial and temporal variability of the underlying eddy field can be constructed. The altimeter results reveal an annual “pulsation” of energy and of coherent eddies originating during the late fall at a particular location in the boundary current, pinpointing the time and place of the boundary current-type eddy formation. The interannual variability seen at the mooring is reproduced, but the mooring site is found to be within a localized region of greatly enhanced eddy activity. Notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling. These eddy observations, as well as hydrographic evidence, suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region.

Description: A three-dimensional physical oceanographic model was used to simulate the temporal evolution of ichthyoplankton distributions in the Bornholm Basin, Baltic Sea. The Bornholm Basin is one of the major spawning grounds for cod (Gadus morhua callarias L.) and sprat (Sprattus sprattus balticus S.) in the Baltic Sea with a large number of historic survey data as well as material from ongoing investigations being available. The aim of the present study was to investigate the quantitative influence of different factors on abundance estimates of early life stages (eggs and larvae) of cod and sprat. Influences under consideration were advective losses, uncertainty due to non-sufficient spatial sampling resolution (e.g. number of stations) and effects of the sampling strategy (e.g. sequence of stations). The numerical simulations were performed for two time periods with contrasting meteorological forcing conditions. Errors in abundance estimates were highest at high wind speeds and when the organisms showed a patchy distribution. Advective losses were highest for the shallowest distributed life stages (cod and sprat larvae). Under strong west-wind conditions, losses due to transport out of the surveyed area reached up to 〉10% after 2 days. Different sampling strategies had no impact on overall accuracy. Errors due to sampling resolution amounted to 2–26% for the standard grid of 45 stations. The results suggest that wind forcing might serve as a first rough approximation for the reliability of historic abundance estimates.

Description: As a part of the Russian-German project "Siberian River-Runoff (SIRRO)" the major element composition of the dissolved load and the major and trace element composition of particulate load and bottom sediment of the Yenisei River and Estuary were analyzed and examined in context of the basin lithology and climate. In addition, the processes controlling the transformation of the river load in the estuarine mixing zone were investigated. The chemical composition of the dissolved and particulate load of the Yenisei fluvial endmember is generally comparable to that of other major world rivers. The dissolved load is chiefly controlled by carbonate weathering and the chemical composition of the river suspended particulate matter (SPM) is similar to that of the North American Shale Composite (NASC), which represents the weathering product of the upper continental crust. The Chemical Index of Alteration (CIA) of the Yenisei SPM amounts to 71, which indicates moderate chemical weathering. With regard to the SPM geochemistry, the Yenisei occupies an intermediate position between the adjacent rivers Khatanga and the Lena. Drastic changes in the composition of the river load are seen in the mixing zone between fresh and salt water. While dissolved Na, Ca, Mg, K, CI, S04, F, Br, Sr and HC03 behave conservatively, dissolved Fe is completely removed from solution at very low salinities. Particulate Mn exhibits a pronounced mid-salinity minimum concomitant with a maximum of dissolved Mn, which is probably related to suboxic conditions in the area of the so-called "marginal filter", where highest turbidities are found. The Mn-minimum in SPM is paralleled by depletions of the elements Ba, Zn, Cd, Ni, Cu and V, which can be associated with manganese particles. The estuarine bottom sediments are composed of mud and sand and the sedimentological parameters of the bottom sediments have to be considered for the interpretation of the bulk geochemical data. The chemical composition of the mud is comparable to the SPM, whereas the sand is relatively enriched in Si/Al, Ba/Al, Zr/Al and Sr/Al ratios and depleted in transition metals.

Description: The late Quaternary palaeoenvironmental history of the southern Windmill Islands, East Antarctica, has been reconstructed using diatom assemblages from two long, well-dated sediment cores taken in two marine bays. The diatom assemblage of the lowest sediment layers suggests a warm climate with mostly open water conditions during the late Pleistocene. During the following glacial, the Windmill Islands were covered by grounded ice preventing any in situ bioproductivity. Following deglaciation, a sapropel with a well-preserved diatom assemblage was deposited from ∼10 500 cal yr BP. Between ∼10 500 and ∼4000 cal yr BP, total organic carbon (Corg) and total diatom valve concentrations as well as the diatom species composition suggest relatively cool summer temperatures. Hydrological conditions in coastal bays were characterised by combined winter sea-ice and open water conditions. This extensive period of glacial retreat was followed by the Holocene optimum (∼4000 to ∼1000 cal yr BP), which occurred later in the southern Windmill Islands than in most other Antarctic coastal regions. Diatom assemblages in this period suggest ice-free conditions and meltwater-stratified waters in the marine bays during summer, which is also reflected in high proportions of freshwater diatoms in the sediments. The diatom assemblage in the upper sediments of both cores indicates Neoglacial cooling from ∼1000 cal yr BP, which again led to seasonally persistent sea-ice on the bays. The Holocene optimum and cooling trends in the Windmill Islands did not occur contemporaneously with other Antarctic coastal regions, showing that the here presented record reflects partly local environmental conditions rather than global climatic trends.

Description: The surface water in the Transpolar Drift in the Arctic Ocean has a strong signature of 228Ra. In an earlier study of 228Ra in the open Arctic we showed that the major 228Ra source had to be in the Siberian shelf seas, but only a single shelf station was published so far. Here we investigate the sources of this signal on the Siberian shelves by measurements of 228Ra and 226Ra in surface waters of the Kara and Laptev Sea, including the Ob, Yenisey and Lena estuaries. In the Ob and Lena rivers we found an indication for a very strong and unexpected removal of both isotopes in the early stage of estuarine mixing, presumably related to flocculation of organic-rich material. Whereas 226Ra behaves conservatively on the shelf, the distribution of 228Ra is governed by large inputs on the shelves, although sources are highly variable. In the Kara Sea the maximum activity was found in the Baydaratskaya Bay, where tidal resonance and low freshwater supply favour 228Ra accumulation. The Laptev Sea is a stronger source for 228Ra than the Kara Sea. Since a large part of Kara Sea water flows through the Laptev Sea, the 228Ra signal in the Transpolar Drift can be described as originating on the Laptev shelf. The combined freshwater inputs from the Eurasian shelves thus produce a common radium signature with a 228Ra/226Ra activity ratio of 4.0 at 20% river water. The radium signals of the individual Siberian rivers and shelves cannot be separated, but their signal is significantly different from the signal produced on the Canadian shelf (Smith et al., in press). In this respect, the radium tracers add to the information given by Barium. Moreover, with the 5.8 year half-life of 228Ra, they have the potential to serve as a tracer for the age of a water mass since its contact with the shelves.

Description: Nowhere is the relationship between microorganisms and eukaryotes as diverse, intimate and clinically relevant as in the gastrointestinal tract. An estimated 500–1000 mostly anaerobic species reside in the intestine, approaching enormous densities of 1011–1012 organisms per gram colon content. The commensal interactions between intestinal microorganisms and animal hosts have been difficult to study in the past because of the diversity of microorganisms involved and because of the lack of culturability that accompanies many microbial consortia. However, recent work has provided new insights into these interactions. The recent paper by Stappenbeck et al. [1] as well as several other recent contributions from Gordon's group at the Washington University School of Medicine in St Louis, MO, USA, provide new insights into the commensal bacteria–host relationships in the intestine [2]. Their work was built on the observation that the intestinal blood system of germ-free mice is only poorly vascularized compared with that of conventional animals. When germ-free mice were inoculated with the intestinal flora of conventional mice, vascularization of the blood capillary system grew to normal levels within just ten days. Interestingly, inoculation of germ-free mice with the common gut bacterium Bacteroides thetaiotaomicron also induced growth of the intestinal capillary network to normal levels. The authors could show that Paneth cells play a role in microbially induced angiogenesis. These cells are localized within the crypts of the intestinal cell wall and secrete antimicrobial compounds such as α-defensins or cryptins [3]. In genetic knockout mice that lack Paneth cells, growth of the intestinal capillary network could not be induced following microbial exposure. This report is the first example of intestinal microorganisms affecting mammalian developmental processes by stimulating intestinal angiogenesis.

Description: The aim of this paper was to examine historical physico-chemical water quality parameters (1990–1997) in the River Frome, East Stoke (NGR SY867868), in order to show both annual and seasonal (monthly) trends. EpCO2 (defined as the partial pressure of CO2 in natural water divided by the equilibrium partial pressure of CO2) levels ranged from mean values of 6.32±0.41 in spring/summer to 7.86±1.17 in autumn/winter. A decreasing trend in mean annual EpCO2 was also observed, with a high of 9.61 in 1990 and a low of 5.22 in 1996. The variations were attributed to changes in pH, which showed an inverse relationship with river discharge (r2=0.47). Both pH and EpCO2 levels were strongly linked to biological activity with increases caused by primary productivity. Filterable reactive phosphorus (FRP) and total phosphorus (TP) concentrations correlated with river discharge. The results showed that the majority of the phosphorus load was transported during storm events, which agrees with results from an export coefficient model predicting phosphorus loading in the Frome catchment. Recent River Frome monitoring campaigns using an in situ flow-injection (FI)-based monitor were in agreement with phosphorus concentration and related physico-chemical trends observed during historical sampling and laboratory analysis.

Description: A review of the data on heavy metals in aerosols over the seas of the Russian Arctic is presented. Results of heavy metal studies in aerosols obtained during 11 research expeditions in summer/autumn period from 1991 to 2000, and at Severnaya Zemlya and Wrangel Island in spring, in 1985–1989 are discussed. Concentrations of most heavy metals in the atmosphere in the marine boundary layer in the Russian Arctic are nearly of the same order as literature data from other Arctic areas. The content of heavy metals in the aerosols over the seas of the Russian Arctic shows an annual variation with maximal concentrations during the winter/spring season. In the summer/autumn period increased concentrations of heavy metals could be explained, in most cases, by natural processes (generation of sea salt aerosols, etc.). In some cases, aerosols from Norilsk and Kola Peninsula were detected. Particular attention was paid to estimation of horizontal and vertical fluxes of atmospheric heavy metals. We estimated annual variations in long-range transport of heavy metals into the Russian Arctic in 1986–1995. In winter and spring, up to 50% of the average air pollutant concentrations in the Russian Arctic are due to the Arctic atmospheric pollution itself. Moreover, the monthly and annual averaged fluxes of six anthropogenic chemical elements (arsenic, nickel, lead, vanadium, zinc and cadmium) onto the surface in the Arctic were estimated, and the values obtained were in reasonable agreement with the literature data available.

Description: The global biodiversity crisis has motivated new theory and experiments that explore relationships between biodiversity (species richness and composition in particular), productivity and stability. Here we emphasize that these relationships are often bi-directional, such that changes in biodiversity can be both a cause and a consequence of changes in productivity and stability. We hypothesize that this bi-directionality creates feedback loops, as well as indirect effects, that influence the complex responses of communities to biodiversity losses. Important, but often neglected, mediators of this complexity are trophic interactions. Recent work shows that consumers can modify, dampen or even reverse the directionality of biodiversity-productivity-stability linkages inferred from the plant level alone. Such consumer mediation is likely to be common in many ecosystems. We suggest that merging biodiversity research and food-web theory is an exciting and pressing frontier for ecology, with implications for biodiversity conservation.

Description: The internal microstructure of a ferromanganese nodule (#2392, from 154°37.52′W, 9°37.56′N, at water depth 5194 m) was examined in detail on polished sections, and radiometrically dated (230Thex/232Th) along a high-resolution (0.1 mm) depth profile (0–1.3 mm), spanning approximately 271 ka. The fabric shows typical stromatolithic structure and exhibits four orders of basic cyclic growth pattern, namely laminae bands, laminae zones, laminae groups and laminae pairs having average thicknesses of 402–454, 185–206, 58–67 and 15–18 μm, respectively. A profile from the depth of 200–2661 μm was selected to obtain the geochemical series using line-scanning electron microprobe analyses, which provide a record of paleoceanographic oscillations during the growth period. Power spectral analysis of the geochemical series for Al, Mn, Fe and Fe/Mn from the depth of 200–1220 μm, where no obvious discontinuity could be observed, display conspicuous cyclicities. The cycles of laminae zones, laminae groups and laminae pairs are reflected in the spectral patterns as well. The significant spectral peaks are located at 186, 108, 66 μm. Together with the cycle of laminae bands, the ratios of these cyclicities are close to those of Milankovitch orbital cycles. Through tuning to orbital cycles, a net growth rate of 4.5 mm/Ma is derived for the profile, which is in perfect agreement with the growth rate of 4.6 mm/Ma determined by 230Thex/232Th dating. Therefore, the rhythmic growth of ferromanganese nodules appears definitely associated with Milankovitch cycles, and the growth cyclicities may offer a new tool for estimating growth rates of ferromanganese nodules and paleoenvironmental reconstruction at substage resolution when supported by radiometric dating.

Description: Gravity driven mass-flow deposits proven by sedimentary and digital echosounder data are indicative for prevailing dynamic sedimentary conditions along the continental margin of the western Argentine Basin. In this study we present geochemical data from a total of 23 gravity cores. Pore-water SO4 is generally depleted within a few meters below the sediment surface by anaerobic oxidation of methane (AOM). The different shapes of SO4 profiles (concave, kink- and s-type) can be consistently explained by sedimentary slides possibly in combination with changes in the CH4 flux from below, thus, mostly representing transient pore-water conditions. Since slides may keep their original sedimentary signature, a combined analysis and numerical modeling of geochemical, physical properties, and hydro acoustic data could be applied in order to reconstruct the sedimentary history. We present first order estimates of the dating of sedimentary events for an area where conventional stratigraphic methods failed to this day. The results of the investigated sites suggest that present day conditions are the result of events that occurred decades to thousands of years ago and promote a persisting mass transport from the shelf into the deep-sea, depositing high amounts of reactive compounds. The high abundance of reactive iron phases in this region maintains low hydrogen sulfide levels in the sediments by a nearly quantitative precipitation of all reduced sulfate by AOM. For the total region we estimate a SO4 (or CH4) flux of 6.6 × 1010 moles per year into the zone of AOM. Projected to the global continental slope and rise area, this may sum up to about 2.6 × 1012 moles per year. Provided that the sulfur is completely fixed in the sediments it is about twice the global value of the recent global sulfur burial in marine sediments of 1.2 × 1012 moles per year as previously estimated. Thus, AOM obviously contributes very significantly to the regulation of global sulfur reservoirs, which is hitherto not sufficiently recognized. This finding may have implications for global geochemical models, as sulfur burial is an important control factor in the development of atmospheric oxygen levels over time.

Description: Observations from a four-year current meter mooring at 28°44′N, 13°28′W in the Lanzarote passage are used to describe the transport variability of the Eastern Boundary Current of the North Atlantic Subtropical Gyre. Three different water masses are found in the passage: North Atlantic Central Water in the upper levels (roughly Full-size image (〈1 K)), Antarctic Intermediate Water (roughly Full-size image (〈1 K)) and Mediterranean Water in the layer above the bottom at Full-size image (〈1 K). The mean southward transport of NACW is Full-size image (〈1 K)Full-size image (〈1 K) which is the transport of the easternmost branch of the Canary Current. Fluctuations of NACW transport are large, ranging from Full-size image (〈1 K) southward to Full-size image (〈1 K) northward. Every autumn a consistent northward transport is observed, which may be related with the eastern boundary upwelling dynamics. The mean transports of AAIW and MW are Full-size image (〈1 K) northward and Full-size image (〈1 K) southward, respectively. Fluctuations of transport of AAIW and MW are large, from 1.0 to Full-size image (〈1 K) and from −0.32 to Full-size image (〈1 K), respectively. Thus, the mass transports for each water mass show a high standard deviation of comparable magnitude to the mean. This highlights the importance of the temporal variability of the currents in this passage. A remarkable feature of our observations is that the mean transports of NACW and AAIW during an El Niño event are significantly different.

Description: Explosive ocean island volcanism in the Greenland–Iceland–Norwegian Sea (GIN Sea) is indicated by marine tephra layers at 10–300 ka. Peaks of explosive volcanism occurred in oxygen isotope stages 8, 7, 5 and 1. The depositional age of the tephra was estimated using the oxygen isotope stratigraphy and dating of marine records. Geochemical analyses of the tephra layers show that all originate from Iceland. Here we report the characteristics of tephra from these major Icelandic events in 30 deep-sea cores from the GIN Sea. Our findings provide constraints on the distribution of tephra from the eruption source. For the Vedde Ash (oxygen isotope stage 1) we estimate a minimum fallout area of 2∗105 km2, stretching from central Greenland in the west and southern Sweden in the east, to 71°N in the GIN Sea. The magnitude of the eruption and the regional wind conditions controlled the extent and concentrations of these ash fallout events. Oceanic circulation and differential settling may have affected the distribution and final deposition of ash particles such as bubble wall shards.

Description: New 238U–230Th disequilibria data by thermal ionisation mass spectrometry are presented for a comprehensive set of postglacial basaltic lavas from the neovolcanic zones in Iceland. The new data show a striking systematic decrease in 230Th excess towards central Iceland and the presumed centre of the Iceland plume. This finding would appear paradoxical if source composition was the main factor responsible for generating the 238U–230Th disequilibria, because generally main rift lavas erupted proximal to the plume should be generated from a melting column that initiates deeper in the garnet stability field, compared to the marginal rift zones. Preferential crustal interaction in central Iceland, where the crust is thickest, involving either old (〉350 kyr) Icelandic crust or lower crustal melts, may provide a viable explanation for only part of the data variation, namely the moderately low 238U–230Th disequilibria found in the more evolved SE rift lavas. Moreover, there is no variation of 230Th excesses with degree of differentiation (Mg# or ppm Th) overall, or within individual rift systems, to indicate that crustal contamination causes the radial variation in 230Th excess. The 238U–230Th disequilibria variation is therefore ascribed to variable dynamic parameters in the melting regime induced by interaction of the Iceland plume with the rift systems. The higher 230Th excesses in alkalic off-rift lavas (Snæfellsnes Peninsula) (24±3%) compared to the main rift lavas (15±3%) is consistent with more garnet-rich lithologies dominating the bulk melt compositions away from the main rifts and indicates small-scale source heterogeneity beneath Iceland. The data are reconciled within a model in which mantle upwelling rates in the centre of the plume are significantly faster than at the margins, consistent with fluid dynamic predictions for a plume head. The radial variation observed in (230Th/238U) provides independent support that the centre of the Iceland plume is located beneath SE Iceland, as has been proposed from seismic tomographic studies. For a reasonable range of mantle porosities (Φ=0.05–0.2%) we can explain the Iceland data with a dynamic melting model, by relatively fast mantle upwelling rates in the centre (∼5–20 cm/yr), compared to those at the margins (∼1–4 cm/yr). The radial variation is also shown to be consistent with, though not requiring, a model of deep dehydration melting [Ito et al., Earth Planet. Sci. Lett. 165 (1999) 81–96]. In such a scenario, the generation of (moderately) low 238U–230Th disequilibria will be confined to the lowermost part of the melting column, which is characterised by fast upwelling and low porosity. For Φ values down to 0.05% in the lower part of the hydrous melting zone, moderately low 230Th excesses (5–10%) are likely to result, whereas higher 230Th excesses may arise for lower values of Φ.

Description: Twelve gravity cores from various settings within the Mayotte barrier reef–lagoon complex were studied to determine the sedimentology of the sequence stratigraphic systems tracts that formed during the Holocene transgression. Our studies focussed on the determination of physical, chemical, mineralogical and biological parameters of the sediments from specific systems tracts. These parameters determine the thickness and facies of each systems tracts and are controlled by the rate and amplitude of sea-level rise, lagoonal topography and environmental changes. The lowstand systems tract (LST) (before 11.5 ka BP) comprises ferralitic or organic-rich paleosoils in the proximal and middle lagoon and karstified Pleistocene reefal carbonates in the distal lagoon. The transgressive systems tract (TST) (11.5–7 ka BP) consists of a lower terrigenous and an upper mixed terrigenous–carbonate or carbonate-dominated unit. Locally, mangrove muds were deposited. The highstand systems tract (HST) can be divided into an early highstand (eHST) (7–1 ka BP) and a late highstand systems tract (lHST) (after 1 ka BP). In the proximal lagoonal wedge, the early highstand systems tract consists of terrigenous or mixed terrigenous–carbonate muds to sandy muds. In the middle lagoon, it shows carbonate mud to sandy mud and carbonate gravel to reefal carbonates in the distal lagoons. Terrigenous muds dominate the late highstand systems tract in the proximal lagoonal wedge. In the mid-lagoonal plain, mixed terrigenous–carbonate or carbonate mud to sandy mud dominates, while carbonate gravel to reefal carbonate prevails in the distal lagoon. For the last 9 ka, sedimentation in the lagoon of Mayotte has been spatially divided into a proximal terrigenous and a distal, carbonate-dominated province. Maximum carbonate concentrations between 4 and 1 ka BP coincide with the time of maximum solar insolation. After 1 ka BP, a general decrease in carbonate concentrations can be observed. This coincides with increased terrigenous sediment input, which results from a reduction in accommodation space and to some extent is of anthropogenic origin.

Description: In an attempt to characterise the role of nitric oxide (NO) in immune responses of carp, carp leucocytes obtained during an acute T. borreli infection were examined, for their capacity to generate NO. In a second set of experiments the impact NO on viability of the parasite and on the modulation of functional carp leucocyte responses were testedin vitro . Both in carp head-kidneys and in the peripheral blood, the fractions of lymphoblasts among separated leucocytes were increased. However, the relative proportions of granulocytes among head-kidney leucocytes (HKL) significantly decreased during infection, whereas granulocytes appeared among peripheral blood leucocytes (PBL). The cellular dynamics of HKL and PBL of infected carp were paralleled by an enhanced spontaneous NO release in vitro. NO production was further increased after addition of viable parasites to these cultures. The hypothesis that NO had a possible role in granulocyte activation and lymphocyte proliferation in carp was supported by the reduction of mitogen-induced proliferative responses of PBL from healthy carp in the presence of NO donor substances. The negative effects of NO on lymphocyte proliferation were contrasted by enhancing effects on granulocyte functions: the inhibition of NO generation in T. borreli -stimulated HKL cultures by the l-arginine analogue L-NMMA reduced the viability of granulocytes and their phagocytic activity. Even massive amounts of nitric oxide produced by donor substances (up to 600 μmol l−1 NO−2) caused no reduction in the numbers of viable T. borreli flagellates in vitro. Thus, in carp, T. borreli seems to induce high amounts of NO in vivo which are apparently not harmful for the parasite but which may interfere with co-ordinated interactions of activated cells aiming at the defence of the parasite.

Description: This paper investigates the mechanism which generates decadal modulations in the amplitude of the El Niño-Southern Oscillation phenomenon (ENSO). Our analysis is based on a multicentury present-day climate simulation performed with an ENSO-resolving Coupled General Circulation Model (CGCM). In consistency with observations, it is found that ENSO variance undergoes changes with a time scale of about 10–20 years. This decadal beat is closely linked to the second dominant pattern of tropical (sub)surface temperature variability. The dipole-like characteristic of this mode is generated mainly by the interplay of horizontal, vertical advection and mixing. We suggest a nonlinear mechanism, which is capable of generating decadal tropical climate anomalies as well as decadal ENSO amplitude modulations (DEAMs) without invoking extratropical dynamics. This mechanism is based on the idea of homoclinic orbits. This new paradigm is validated using a low-dimensional ENSO model that is derived empirically from the CGCM simulation.

Description: We discovered and investigated several cold-seep sites in four depth zones of the Sea of Okhotsk off Northeast Sakhalin: outer shelf (160–250 m), upper slope (250–450 m), intermediate slope (450–800 m), and Derugin Basin (1450–1600 m). Active seepage of free methane or methane-rich fluids was detected in each zone. However, seabed photography and sampling revealed that the number of chemoautotrophic species decreases dramatically with decreasing water depth. At greatest depths in the Derugin Basin, the seeps were inhabited by bacterial mats and bivalves of the families Vesicomyidae (Calyptogena aff. pacifica, C. rectimargo, Archivesica sp.), Solemyidae (Acharax sp.) and Thyasiridae (Conchocele bisecta). In addition, pogonophoran tubeworms of the family Sclerolinidae were found in barite edifices. At the shallowest sites, on the shelf at 160 m, the seeps lack chemoautotrophic macrofauna; their locations were indicated only by the patchy occurrence of bacterial mats. Typical seep-endemic metazoans with chemosynthetic symbionts were confined to seep sites at depths below 370 m. A comparative analysis of the structure of seep and background communities suggests that differences in predation pressure may be an important determinant of this pattern. The abundance of predators such as carnivorous brachyurans and asteroids, which can invade seeps from adjacent habitats and efficiently prey on sessile seep bivalves, decreased very pronouncedly with depth. We conclude from the obvious correlation with the conspicuous pattern in the distribution of seep assemblages that, on the shelf and at the upper slope, predator pressure may be high enough to effectively impede any successful settlement of viable populations of seep-endemic metazoans. However, there was also evidence that other depth-related factors, such as bottom-water current, sedimentary regimes, oxygen concentrations and the supply of suitable settling substrates, may additionally regulate the distribution of seep fauna in the area. As a consequence of the pronounced pattern in the distribution of seep communities, their ecological significance as food sources of surrounding background fauna increased with water depth. Isotopic analyses suggest that in the Derugin Basin seep colonists feed on chemoautotrophic seep organisms, either directly or by preying on metazoans with chemosynthetic symbionts. In contrast, seep organisms apparently do not contribute to the nutrition of the adjacent background fauna on the shelf and at the slope. In this area, elevated epifaunal abundances at seep sites were caused primarily by the availability of suitable settling substrates rather than by an enrichment of food supply.

Description: Observation data from the southern Kara Sea demonstrate high interannual variability of bottom water temperature, salinity, and nutrients in summer. Low oxygen isotope events reconstructed from samples taken along the growth direction on shells of living bivalves show variations which reflect salinity changes probably caused by summer river run-off. These records indicate that the freshwater signal is discernible at the sea floor in water depths of at least 30 m, but is not observed in 70 m water depth. There is no evidence for a correlation between nutrients and carbon isotope composition ofthe bivalve shells.

Description: U-series disequilibria are presented for Holocene samples from the Canary Islands and interpreted with special emphasis on the separate roles of plume vs. lithospheric melting processes. We report Th and U concentrations and (238U)/(232Th), (230Th)/(232Th), (230Th)/(238U) and (234U)/(238U) for 43 samples, most of which are minimally differentiated, along with (226Ra)/(230Th) and (231Pa)/(235U) for a subset of these samples, measured by thermal ionization mass spectrometry (TIMS). Th and U concentrations range between 2 and 20 ppm and 0.5 and 6 ppm, respectively. Initial (230Th)/(238U) ranges from 1.1 to 1.6. (226Ra)/(230Th)o ranges between 0.9 and 1.8 while (231Pa)/(235U)o ranges between 1.0 and 2.0. Our interpretation of results is based on a three-fold division of samples as a function of incompatible element ratio, such as Nb/U. The majority of samples have Nb/U = 47 ± 10, similar to most MORB and OIB. Higher ratios are found exclusively in alkali basalts and tholeiites from the eastern Canary Islands whereas lower ratios are exclusively found in differentiated rocks from the western Canary Islands. Those with ordinary Nb/U ratios are attributed to melting within the slowly ascending HIMU-dominated Canary plume. Higher Nb/U, generally found in more silica rich basalts from the eastern islands, is attributed to lithospheric contamination. Based on their trace element characteristics, two possible contaminants are amphibole veins (± other minerals) crystallized in the mantle from previous plume-derived basanite or re-melted plume-derived intrusive rocks. The high Nb/U signature of these materials is imparted on a melt of the lithosphere created either by the diffusive infiltration of alkalis or by direct reaction between basanites and peridotite. Mixing between plume-derived basanite and lithospheric melt accounts for the U-series systematics of most eastern island magmas including the well-known Timanfaya eruption. Lower Nb/U ratios in differentiated rocks from the western islands are attributed to fractional crystallization of amphibole ± phlogopite ± sphene from basanite during its ascent through the lithosphere. Based on changes in disequilibria, phonolites and tephrites are interpreted to result from rapid differentiation of primitive parents within millennia.

Description: On active tectonic margins methane-rich pore fluids are expelled during the sediment compaction and dewatering that accompany accretionary wedge development. Once these fluids reach the shallow subsurface they become oxidized and precipitate cold seep authigenic carbonates. Faults or high-porosity stratigraphic horizons can serve as conduits for fluid flow, which can be derived from deep within the wedge and/or, if at seafloor depths greater than ∼300 m, from the shallow source of methane and water contained in subsurface and surface gas hydrates. The distribution of fluid expulsion sites can be mapped regionally using sidescan sonar systems, which record the locations of surface and slightly buried authigenic carbonates due to their impedence contrast with the surrounding hemipelagic sediment. Hydrate Ridge lies within the gas hydrate stability field offshore central Oregon and during the last 15 years several studies have documented gas hydrate and cold seep carbonate occurrence in the region. In 1999, we collected deep-towed SeaMARC 30 sidescan sonar imagery across the Hydrate Ridge region to determine the spatial distribution of cold seep carbonates and their relationship to subsurface structure and the underlying gas hydrate system. High backscatter on the imagery is divided into three categories, (I) circular to blotchy with apparent surface roughness, (II) circular to blotchy with no apparent surface roughness, and (III) streaky to continuous with variable surface roughness. We interpret the distribution of high backscatter, as well as the locations of mud volcanoes and pockmarks, to indicate variations in the intensity and activity of fluid flow across the Hydrate Ridge region. Seafloor observations and sampling verify the acoustic signals across the survey area and aid in this interpretation. Subsurface structural mapping and swath bathymetry suggest the fluid venting is focused at the crests of anticlinal structures like Hydrate Ridge and the uplifts along the Daisy Bank fault zone. Geochemical parameters link authigenic carbonates on Hydrate Ridge to the underlying gas hydrate system and suggest that some of the carbonates have formed in equilibrium with fluids derived directly from the destabilization of gas hydrate. This suggests carbonates are formed not only from the methane in ascending fluids from depth, but also from the shallow source of methane released during the dissociation of gas hydrate. The decreased occurrence of high-backscatter patches and the dramatic reduction in pockmark fields, imaged on the eastern part of the survey, suggest gas hydrate near its upper stability limit may be easily destabilized and thus, responsible for these seafloor features. High backscatter along the left-lateral Daisy Bank fault suggests a long history of deep-seated fluid venting, probably unrelated to destabilized gas hydrate in the subsurface.

Description: Aragonite is precipitated by a new CO2-diffusion technique from a Ca2+–Mg2+–Cl− solution between 10 and 50 °C. Crystallisation of aragonite instead of calcite occurs by maintaining a [Mg2+]/[Ca2+] ratio of 2 in the fluid. The dissolved inorganic carbon (DIC) is received by diffusion of CO2 through a polyethylene membrane (diffusion coefficient: DCO2=10−6.4 cm2 s−1 at 19 °C). It is suggested that significant amounts of DIC may be transferred by diffusion of CO2 in natural systems if the CO2 gradient is high. The CO2-diffusion technique is used as a kind of simple mixed flow reactor for the co-precipitation of barium and strontium with aragonite. The distribution coefficients of Ba2+ and Sr2+ decrease from 10 to 50 °C according to DBa,a*=2.42−0.03595T (°C) and DSr,a*=1.32−0.005091T (°C). At 25 °C, the distribution coefficients are DBa,a*=1.5±0.1 and DSr,a*=1.19±0.03. The effect of temperature on DBa,a* is about one order of magnitude higher versus that on DSr,a*. Thus, Ba2+ may be a potential paleotemperature indicator if the composition of the solution is known.

Description: As food protein digestion is instrumental for promoting growth, the main protease in young marine fish larvae, trypsin, was studied in pre-leptocephalus larvae of Anguilla japonica. Tryptic enzyme activity was monitored until day 24 and rates of growth until day 36 after hatch in larval A. japonica derived from artificially matured parent fish. Tryptic activity increased with larval age and developmental stage until day 16, after which tryptic levels stabilized. In start-feeding larvae, tryptic activities increased after ingestion of an artificial diet, but elevated tryptic activities could also be found in larvae with guts void of prey, possibly due to intestinal retention of trypsin secreted in response to ingestion of a previous meal. Gut retention time for trypsin was estimated to be at least 15 h. The gut evacuation time for the artificial diet depended on the meal size and was in the range of 1-5.5 h. Rates of larval growth in length were ca. 5% day-1 during the yolk-sac stage, declining to ca. 1% day-1 in older larvae. Vision was highly important for initiation of feeding. Results provide the first quantitative information on aspects of protein digestion in eel larvae. 2003 Elsevier Science B.V. All rights reserved.

Description: Ningaloo Reef, situated on the central west coast, is Australia's largest fringing reef system extending southward from 22°S for over 200 km. Its narrow lagoon is backed by a coastal plain, which is largely composed of an emergent Last Interglacial reef on the flank of folded Tertiary limestones. The west-facing reef is exposed to strong oceanic swells across a narrow (8 km) continental shelf. Climatic aridity, cyclones, tsunamis, and the poleward flowing Leeuwin Current all influence the reef system. Seismic profiling and a coring and dating program along a transect through a reef pass indicate two periods of reef development in the northern part of the reef: Holocene and Last Interglacial. Seaward of the crest, the Holocene reef forms either a prominent 500 m-wide bulge with 10 m of relief and an abrupt seaward slope, or a series of discrete patch reefs. Holocene reef development is limited to depths of less than 30 m and reaches a maximum thickness of ca. 10–15 m below the reef crest. U/Th TIMS dates from distal parts of the Last Interglacial section between −18 and −36 m give ages toward the end of the high stand (120–115 ka). Last Interglacial reef growth was more extensive of the two, filling much of the available accommodation space, perhaps as a result of a stronger Leeuwin Current. This substrate subsequently provided an antecedent foundation for Holocene reef development.

Description: The Santi Petri dome (western Betics, southern Spain) shows a core-complex-like structure, where migmatitic gneisses and schists outcrop below low-grade slates and phyllites, all of which form the basement of the Neogene Málaga basin. The migmatites and schists suffered a coaxial-flattening event during isothermal decompression and were later exhumed by ductile ESE non-coaxial stretching. Further exhumation was achieved by W- to SW-transport brittle low-angle normal faulting. Subsequently these extensional structures were gently folded in the core of a NE/SW-oriented antiform during the Tortonian. Finally the Santi Petri domal geometry was accentuated by the interference of orthogonal high-angle faults with ENE–WSW and NNW–SSE orientation. This core-complex-like structure, formed by superposition of extensional and compressive tectonic events, does not represent a classical, purely extensional core complex, which shows that metamorphic structure and geometry are not decisive criteria to define a core-complex.

Description: High-resolution palaeoclimate records recovered from the Iberian margin in core MD95-2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka. Large-scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer Neogloboquadrina pachyderma (sinistral), and in some instances the occurrence of ice-rafted debris (IRD). Ice-rafting episodes were prevalent in both of the last two glacials with greater intensity in Stages 2 through 4, than in Stage 6. The six youngest Heinrich events are well defined during the last glacial but detrital carbonate is absent from Heinrich layers HL6, HL5 and HL3. Dansgaard–Oeschger stadial-equivalent sub-millennial IRD deposition events have been detected, in particular during Stage 3, allowing a good match with the cooling displayed in the Greenland ice core (GISP2). Sea-surface temperature off Portugal in Stage 6 was in general warmer than during the last glacial, pointing towards a weaker southward influence of polar water masses. Ice rafting occurred mainly in mid-MIS (Marine Isotope Stage) 6 (between 173 and 153 kyr) as a group of poorly differentiated, short-duration quasi-continuous events, mainly marked by the high abundance of sinistral N. pachyderma. Differences exist in IRD composition relative to the last glacial, with a reduced Canadian-derived detrital carbonate component, combined with an important contribution of volcanic particles. The lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas.

Description: In contrast to the situation observed in mammals and birds, a switching between different sex determination systems frequently occurred during the evolution of the teleost fish lineage. This might be due to a frequent turnover of sex-determining signals at the top of the sex determination cascade (master sex-determining genes in the case of genetic sex determination). Alternatively, different variations of a same master gene might decide the sex of individuals in different sex determination systems. In the medaka Oryzias latipes, a Y-specific copy of the putative transcription factor gene dmrt1 very likely corresponds to the master sex-determining gene inducing male formation [Nature 417 (2002) 559; Proc. Natl. Acad. Sci. U. S. A. 99 (2002) 11778]. This gene, alternately called dmY and dmrt1Y, has been formed by duplication of the autosomal dmrt1. In order to determine if an orthologue of dmrt1Y was also located in the sex determination region of the related platyfish Xiphophorus maculatus, Southern blot analysis was performed on genomic DNA from XY and YY males and WY and XX females using both medaka and human dmrt1 cDNA as probes. Using different restriction enzymes, no evidence for sex-specific dmrt-containing genomic fragments could be found in the platyfish. No dmrt gene could be detected by low-stringency Southern blot analysis of genomic inserts from 60 bacterial artificial chromosome (BAC) clones linked to the sex-determining locus on the X and Y chromosomes. Six different groups of BAC clones containing dmrt genes were isolated from a platyfish genomic library. X. maculatus dmrt1 gene and cDNA were characterised. In adult, expression of dmrt1 was detected only in testis. Phylogenetic analysis indicated that the duplication of dmrt1 that led to the formation of dmY/dmrt1Y within the medaka lineage clearly occurred after its divergence from the platyfish lineage. Hence, a dmY/dmrt1Y orthologue generated by this particular event of duplication does not correspond to the master sex-determining gene in the platyfish.

Description: Optical turbidity surveys combined with pigment, plankton, and current measurements were used to investigate the vertical and horizontal dynamics of suspended particulate matter (SPM) in the Laptev Sea, one of the largest Siberian shelf seas, during the ice-free period. Optical measuring devices prove to be an excellent tool to measure SPM distribution in real time. SPM concentrations were quantified owing to the high correlation of water samples and optical backscatter. Thus, the formation and distribution of the bottom nepheloid layer, a layer of increased SPM concentration, and its significance for the sediment transport on the Laptev Sea shelf can be described. Two nepheloid layers exist in the eastern and central Laptev Sea. Formation and concentration of the surface layer are mainly related to the amount of phytoplankton and zooplankton occurrence. However, in the vicinity of the Lena Delta, the concentration is strongly dependent on riverine discharge. The bottom nepheloid layer is suggested to develop during and briefly after the spring breakup, when about 60% of the mean annual sediment input is discharged onto the shelf. SPM spreads over the shelf and is kept in suspension within the bottom layer. Especially during the ice-free period, almost no sedimentation takes place. However, bottom material is resuspended due to wind-induced increased bottom currents, mainly in paleo-river valleys and on shoals. Valleys act as transport conduits during the ice-free period and SPM is shifted within them. An intermediate layer near Stolbovoy Bank is probably caused by the displacement of the bottom layer from the topographic highs into the valleys. The combined turbidity and current measurements indicate that most of the sediment transport on the Laptev Sea shelf takes place in the bottom nepheloid layer.

Description: Dredged samples from the Geophysicist seamount volcano in the northeastern part of the Kurile Basin include volcanic and volcanoclastic rocks ranging from basalt to andesite. The rocks have geochemical features typical of high-K island-arc calc-alkaline volcanism. They are enriched in LILE and depleted in Zr, Ti, Nb, Ta and Y. The chondrite-normalized REE patterns are characterized by enrichment of LREE similar to those of island-arc lava from the submarine volcanoes of rear-arc zone of the Kurile Island Arc. The volcanic rocks have a wide range of 87Sr/86Sr ratios (0.70287-0.70652), varying 143Nd/144Nd and Pb isotopic ratios. Their trace-element compositions and Sr-Nd-Pb isotope signatures may be explained by a small addition of crustal continental component to mantle-derived magmas that suggest the existence of thinned continental basement under the eastern part of the Kurile Basin.

Description: The vertical density gradients in the Nordic Seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter. These gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera, the isotopic signatures of which represent different calcification depths in the water column. Comparison of δ18O values from foraminiferal tests in plankton hauls, sediment traps, and nearby core top samples with the calculated δ18Ocalcite profile of the water column revealed species-specific δ18O vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment. On the basis of core top samples obtained along a west–east transect across various hydrographic regions of the Nordic Seas, δ18O values of Turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25–75 m water depth. The isotopic signatures of Neogloboquadrina pachyderma (s) reflect water masses near and well below the pycnocline between 70 and 250 m off Norway, where the Atlantic inflow leads to thermal stratification. Here, temperatures in the calcification depth of N. pachyderma (s) differ from sea surface temperature by approximately −2.5°C. In contrast, N. pachyderma (s) calcifies very close to the sea surface (20–50 m) in the Arctic domain of the western Nordic Seas. However, further west N. pachyderma (s) prefers somewhat deeper, more saline water at 70–130 m well below the halocline that confines the low saline East Greenland Current. This implies that the δ18O values of N. pachyderma (s) do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on δ18O is too conservative, because it overestimates sea surface salinity. Minimum δ18O differences (〈0.2‰) between N. pachyderma (s) and T. quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification, whereas thermal stratification leads to δ18O differences of 〉0.4 to 〉1.5‰.

Description: Hydrographic, nutrient and halocarbon tracer data collected in July–August 1994 in the Norwegian Sea, the Faroe Bank Channel (FBC), the Iceland and Irminger Basins and the Iceland Sea are presented. Special attention was given to the overflow waters over the Iceland–Scotland Ridge (ISOW). The Iceland–Scottland overflow water (ISOW) was identified along its pathway in the Iceland Basin, and entrainment of overlying water masses was quantified by multivariate analysis (MVA) using principal component analysis (PCA) and Partial Least Square (PLS) calibration. It was concluded that the deeper portion of the ISOW in the FBC was a mixture of about equal parts of Norwegian Sea Deep Water (NSDW) and Norwegian Sea Arctic Intermediate Water (NSAIW). The mixing development of ISOW during its descent in the Iceland Basin was analysed in three sections across the plume. In the southern section at 61°N, where the ISOW core was observed at Full-size image (〈1 K) depth, the fraction of waters originating north of the ridge was assessed to be 54%. MVA assessed the fractional composition of the ISOW to be 21% NSDW, 22% NSAIW, 18% Northeast Atlantic Water (NEAW), 11% Modified East Icelandic Water, 25% Labrador Sea Water (LSW) and 3% North East Atlantic Deep Water. It may be noted that the fraction of NEAW is of the same volume as the NSDW. On its further path around the Reykjanes Ridge, the ISOW mixed mainly with LSW, and at 63°N in the Irminger Basin, it was warmer and fresher (θ=2.8°C and S=34.92) than at 61°N east of the ridge Full-size image (〈1 K). The most intensive mixing occurred immediately west of the FBC, probably due to high velocity of the overflow plume through the channel, where annual velocity means exceeded Full-size image (〈1 K). This resulted in shear instabilities towards the overlying Atlantic waters and cross-stream velocities exceeding Full-size image (〈1 K) in the bottom boundary layer. The role of NSAIW as a component of ISOW is increasing. Being largely a product of winter convection in the Greenland Sea when no Greenland Sea Deep Water (GSDW) is formed, it spreads above the older and denser deep water in the Nordic Seas. Little or no GSDW, which earlier was considered to be the principal overflow water, has been formed since 1970. This shows that the Iceland–Scotland overflow may also be maintained with intermediate waters as the principal overflowing component. Decadal variability in ISOW properties has not been insignificant, as since the early 1960s there has been a decrease in salinity and temperature, by 0.06 and up to 0.5°C, respectively. Such a trend applies also to the LSW, particularly in the Irminger Basin, where it was warmer, saltier and less dense in the late 1950s and early 1960s Full-size image (〈1 K) than in 1994 Full-size image (〈1 K). CFC tracers were used to assign apparent ages of water masses, showing that the NSDW had an apparent age of about 30 years and that the age of Iceland Sea Deep Water exceeded 25 years. NSAIW observed in the southern Norwegian Sea was estimated to be 6–16 years old. An upper age limit of LSW in the Iceland Basin was found to be 18–19 years. It was further concluded that the products of the onset of intense wintertime convection in the Labrador Sea in the late 1980s were not yet observed in the northern central part of the Iceland Basin. The LSW in the Irminger Basin was found to be significantly younger. Two layers were found there. A shallower layer at a depth of 1000–Full-size image (〈1 K) depth was older than the layer beneath by about 4 years, while the deeper layer at 1500–Full-size image (〈1 K) depth was assessed at an apparent age ranging between less than 1 (formed during the previous winter) and 4 years.

Description: An analysis of TOPEX/POSEIDON altimeter data and in situ current and temperature data obtained between April 1995 and October 1996 from a moored array shows strong intraseasonal fluctuations in the southwestern Arabian Sea, an oceanic region where the Great Whirl (GW), a predominantly wind-generated, very energetic anticyclone, is present during the Southwest Monsoon. Fluctuation periods between 30 and 50 days, up to 100 days during some years, are observed in the 8-year altimetric dataset, mostly during late summer and fall. These fluctuations are largest in a 1000 km-wide region off the Somali, Omani and Yemeni coasts north of 5°N, suggesting a local generation mechanism. The in situ data at different moorings show strong and coherent fluctuations that are characterized by southwestward phase propagation and northward energy propagation. Their periods range from 30 to 60 days and increase steadily from July 1995 to January 1996. In the first stage, these periods are at and below the cut-off period of freely propagating, first baroclinic mode Rossby waves, but approach this theoretical limit later in the year. Instabilities of the flow in the transition region between the Southern Gyre and the GW are likely sources of these fluctuations.

Description: Living and dead benthic foraminiferal assemblages from two size fractions, 63–250 μm and 〉250 μm, were studied at 128 stations from the shelves down to abyssal plains of the Gulf of Guinea in the eastern equatorial Atlantic. The sample size ranged between 300 and 400 cm2 of the sediment/water interface, with a penetration depth of 1 cm. Environmental parameters were quantified for sediment composition, food webs, bottom-water oxygen concentrations, and benthic oxygen respiration. Seven major station groupings (named G1–G7) are subdivided by factor analysis. The three most abundant species therein are discussed with respect to their ecological requirements, for both size classes and for living and dead counts. For 49 living species, the range of environmental gradients is established, and for five species live observations are reported. Five station groupings can be attributed toward stepwise ranges scaled by bathymetry and flux rates of organic carbon (G4, 27–75 m; G5, 68–269 m; G6, 250–740 m; G2, 674–2007 m; G1, 1475–4970 m). Two geographically restricted station groupings locally interfinger with other groupings in the upper bathyal and abyssal water depths (G7, 82–451 m; G3, 1002–4658 m). G7 shows lowered oxygen concentrations and benthic oxygen respirations, whereas hemipelagic sediments are typical of G3. The interfingering of G7 and G3, however, is not purely a result of the increasing number of species most perfectly adapted to these environments but rather that these groupings are structured by the decrease of species with lower tolerance towards environmental perturbation. In fact, the more common species have an environmental range much broader than the environmental frame of the groupings they dominate. This observation holds for all size classes and for live and dead counts. We conclude that species-specific preferences and thresholds provide a more valuable and more consistent tool in environmental research than the environmental ranges observed for assemblages.

Description: The geologic setting of the formerly glaciated mid-Norwegian continental margin exerts specific controls on the formation of a bottom-simulating reflector (BSR) and the inferred distribution of gas hydrates. On the continental slope the lithology of glacigenic debris flow deposits and pre-glacial basin deposits of the Kai Formation prevent gas-hydrate formation, because of reduced pore size, reduced water content and fine-grained sediment composition. Towards the continental shelf, the shoaling and pinch-out of the gas-hydrate stability zone terminates the area of gas-hydrate growth. These geological controls confine the occurrence of gas hydrates and ensuing formation of a BSR to a small zone along the northern flank of the Storegga submarine slide and the slide area itself. A BSR inside the slide area indicates a dynamically adjusting gas-hydrate system to post-slide pressure–temperature equilibrium conditions. These observations, together with widespread evidence for fluid flow and deep-seated hydrocarbon reservoirs, suggest that the formation of BSR and gas hydrates on the mid-Norwegian continental margin is dominated by an advection of gas from the strata distinctly beneath the gas-hydrate stability zone. Fluids migrate upward within the Naust Formation and are deflected laterally by hydrated sediments and less permeable layers. Gases continually accumulate at the top of the slope, where overpressure eventually results in the formation of blow-out pipes and consequent pockmark development on the seabed.

Description: Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions mimicking sedimentation below the euphotic zone. Changes in the concentrations of biogenic silica, silicic acid, cell numbers, chlorophyll a and transparent exopolymer particles (TEP) were monitored within aggregates and in the surrounding seawater (SSW) during two 42-day experiments. Whereas the concentration of dispersed diatoms decreased over the course of the experiment, the amount of aggregated cells remained roughly constant after an initial increase. Initially only 6% of cells were aggregated and at the end of the experiment more than 60% of cells were enclosed within aggregates. These data imply lower dissolution rates for aggregated cells. However, fluxes of silica between the different pools could not be constrained reliably enough to unequivocally prove reduced dissolution for aggregated cells.

Description: Mixotrophy, a combination of phototrophic and phagotrophic nutrition, has been found in several classes of phytoplankton (Booras et al. 1988, Jones 2000) and appears to be a successful evolutionary strategy. Heterotrophic nutrition of phytoplankton has been suggested to be an important source of mineral nutrients (Nygaard and Tobiesen 1993). Potentially limiting mineral nutrients, particularly phosphorus (P), are often several orders of magnitude more concentrated in the biomass of food organisms of mixotrophs (e.g. in bacteria) than in the dissolved phase (Vadstein 2000). We used radioactive tracer experiments to show that the simultaneous uptake of P from dissolved inorganic and particular P sources by the marine phytoflagellate Chrysochromulina polylepis followed basic predictions of optimal foraging theory (Stephens and Krebs 1986). Chrysochromulina takes up its P rather unselectively from both bacterial P and dissolved P sources at low dissolved P concentrations, while it becomes more selective at higher dissolved inorganic P (DIP) concentrations. The onset of mixotrophic processes was dependent on DIP concentrations. These findings support the view of mixotrophy as a strategy of nutrient uptake in nutrient poor (oligotrophic) pelagic environments (Nygaard and Tobiesen 1993) and show that ideas of optimal foraging can be applied to unicellular organisms.

Description: Ostracod assemblages from coretop sediments collected at 26 localities at different depths of the Laptev Sea shelf and upper continental slope were investigated for assemblage studies. A total of 41 species belonging to 19 genera and 12 families have been identified. Three assemblages have been established that could be linked to environmental factors such as water depth, bottom salinities, water mass circulation and sea-ice transportation. The species-rich and abundant assemblages of the western and central Laptev Sea were related to the Atlantic waters occupying the upper continental slope. These include relatively deep-water forms that show clear affinities to North Atlantic and Arctic Ocean assemblages (Cytheropteron biconvexa, C. testudo, C. simplex, C. nodosoalatum, C. inflatum, C. porterae, Krithe glacialis, K. minima, Pseudocythere caudata, Polycope punctata, P. orbicularis). In the eastern middle shelf region, the assemblage is comprised of Acanthocythereis dunelmensis together with other normal marine species (Semicytherura complanata, Elofsonella concinna, Cluthia cluthae). This assemblage seems connected to the winter flaw polynya which is believed to be the main area of sediment entrainment into sea ice. The inner shelf assemblage of the southern Laptev Sea is dominated by shallow-water euryhaline species (Paracyprideis pseudopunctillata and Heterocyprideis sorbyana) with admixture of the brackish-water species Roundstonia macchesneyi. The unusual occurrence of a number of shallow-water ostracod species on the upper continental slope may be explained by ice-rafting which these ostracods are probably able to survive.

Description: Xenolith samples of marine terrigenous sediments and altered Jurassic MORB from Gran Canaria (Canary Islands) represent samples of sub-island oceanic crust. These samples are postulated to define end-members for crustal contamination of basaltic and felsic ocean island magmas. The meta-igneous rocks show great heterogeneity in oxygen isotope compositions (δ18O 3.3–8.6‰), broadly correlating with their stratigraphic position in the oceanic crust. Gabbros interpreted as fragments of oceanic crust layer 3 have δ18O values of 3.3–5.1‰, which is lower than MORB (5.7–6.0‰). Layer 2 lavas and dykes show a broader range of δ18O of 4.1–8.6‰. Therefore, high-temperature metamorphism seems to have been the dominant process in layer 3, while both high- and low-temperature alteration have variably affected layer 2 rocks. Siliciclastic sediments have high δ18O values (14.1–16.4‰), indicating diagenesis and low-temperature interaction with seawater. The oxygen isotope stratigraphy of the crust beneath Gran Canaria is typical for old oceanic crust and resembles that in ophiolites. The lithologic boundary between older oceanic crust and the igneous core complex at 8–10 km depth—as postulated from geophysical data—probably coincides with a main magma stagnation level. There, the Miocene shield phase magmas interacted with preexisting oceanic crust. We suggest that the range in δ18O values (5.2–6.8‰) [Chem. Geol. 135 (1997) 233] found for shield basalts on Gran Canaria, and those in some Miocene felsic units (6.0–8.5‰), are best explained by assimilation of various amounts and combinations of oceanic and island crustal rocks and do not necessarily reflect mantle source characteristics.

Description: Four cores from the fringing reefs and five sediment cores from Mayotte Lagoon, Comoro Archipelago, southwest Indian Ocean, which reached the Pleistocene/Holocene boundary, form the database of this study. They offer the opportunity to reexamine and complete the postglacial sea-level curve, especially for the time interval between 11.6 to 8 kyr cal BP. Between 11.6 kyr cal BP until present the history of sea-level rise showed the following steps: (1) by about 19 mm/yr between 11.6 and 9.6 kyr cal BP, (2) by 9 mm/yr between 9.6 and 8 kyr cal BP, (3) by 3 mm/yr between 8 and 7 kyr cal BP, and (4) by 0.9 mm/yr after 7 kyr cal BP until stabilisation at present level at 2.5 kyr cal BP. In addition, a decline in the rates of sea-level rise or even a stillstand is observed between 13 to 11.6 kyr cal BP. The flooding of the lagoon of Mayotte was controlled by the depth of the reefal passages, which were cut by rivers and/or due to erosion during the time of emergence since the last interglacial. The differences in the shape of the sea-level curve from Mayotte compared to those from other sites located far from the former glaciated regions are related to: (1) the small size of the island, (2) the rapid downward movement of this small volcanic island with the oceanic plate into the mantle due to hydro–isostatic compensation after addition of meltwater, and (3) the location between large continents.

Description: The nature of rhythmic carbonate-rich successions such as limestone^marl alternations has been, and still is, subject to controversy. The possibility of an entirely diagenetic origin for the rhythmic calcareous alternations is discarded by most authors. One problem with an entirely diagenetic, self-organized development of limestone^marl alternations is the fact that limestone and marl beds in many examples are laterally continuous over hundreds of meters or even kilometers. In an entirely self-organized system, lateral coupling would be very limited; thus one would expect that, rather than laterally continuous beds, randomly distributed elongate nodules would form. We address the origin of limestone^marl alternations using a computer model that simulates differential diagenesis of rhythmic calcareous successions. The setup uses a cellular automaton model to test whether laterally extensive, rhythmic calcareous alternations could develop from homogeneous sediments in a process of self-organization. Our model is a strong simplification of early diagenesis in fine-grained, partly calcareous sediments. It includes the relevant key mechanisms to the question whether an external trigger is required in order to obtain laterally extensive limestone^ marl alternations. Our model shows that diagenetic self-organization alone is not sufficient to produce laterally extensive, correlatable beds. Although an external control on bedding formation could be considered to have solved the problem as commonly assumed, we here suggest an interesting third possibility: the rhythmic alternations were formed through the interaction of both an external trigger and diagenetic self-organization. In particular we observe that a very limited external trigger, either in time or amplitude, readily forms correlatable beds in our otherwise diagenetic model. Remarkably, the resulting rhythmites often do not mirror the external trigger in a one-to-one fashion and may differ in phase, frequency and number of couplets. Therefore, the interpretation of calcareous rhythmites as a one-to-one archive of climate fluctuations may be misleading. Parameters independent of diagenetic alteration should be considered for unequivocal interpretation.

Description: A new technique for the precise and accurate determination of Cd stable isotope compositions has been developed and applied to geological materials and meteorites. The Cd isotope analyses are performed by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) using external normalization to Ag for mass bias correction. The accuracy of the new procedure was ascertained by the comparison of data for meteorites with published results acquired by thermal ionization mass spectrometry and double spiking. Some results were also confirmed by measurements using external normalization to Sb on a different MC-ICPMS instrument. A long-term reproducibility of ± 1.1 εCd/amu (2 sd) was obtained for separate dissolutions and multiple analyses of several rock and meteorite samples (εCd/amu represents the deviation of a Cd isotope ratio of a sample relative to the JMC Cd standard in parts per 104, normalized to a mass difference of 1 amu). As little as 5–20 ng of Cd are sufficient for the acquisition of precise and accurate data. Terrestrial rock and mineral samples display little variations in Cd isotope compositions (εCd/amu between −1 and +1.2), except for a tektite sample that was found to be enriched in the heavy Cd isotopes by +7.6 εCd/amu. The carbonaceous chondrites Orgueil, Murchison and Allende have Cd isotope ratios that are unfractionated relative to the JMC Cd standard and terrestrial rocks. The ordinary chondrites analyzed in this study and a Rumuruti chondrite display Cd isotope fractionations, ranging from −19 to +36 εCd/amu. These results suggest that substantial (inorganic) natural Cd isotope fractionations are generated only by evaporation and/or condensation processes. The lack of resolvable Cd isotope variations between the different carbonaceous chondrites, despite large differences in Cd concentrations, implies that the primary depletion of Cd in the early solar system did not involve Rayleigh evaporation. The Cd isotope fractionation in ordinary and Rumuruti chondrites is probably due to the redistribution of Cd by evaporation and condensation processes during thermal metamorphism on the parent bodies. Models that explain the enrichments of highly volatile elements in unequilibrated ordinary chondrites by primary equilibrium condensation appear to be inconsistent with the Cd isotope data.

Description: The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the Palomares area have permitted us to define the geometry and location of sedimentary depocentres related with the PFZ. These data show an eastward displacement between the Upper Tortonian to Messinian and the Pliocene–Quaternary sedimentary depocentres, towards the presently active Arteal fault, which bounds the western mountain front of Sierra Almagrera, showing that deformation along this fault zone has migrated towards the east, from the Palomares segment, with its main activity during the Upper Tortonian and Messinian, towards the Arteal fault, active during the Pliocene and Quaternary.

Description: The blooms of cyanobacteria that develop each summer in the Baltic Sea are composed of two functional groups, namely the small-sized picocyanobacteria (Synechococcus sp.) and the larger, colony-forming, filamentous N2-fixing cyanobacteria. The former encompassed both red (phycoerythrin-rich) and blue-green (phycocyanin-rich) species. The majority of the picocyanobacteria measured less than 1 μm and this size fraction comprised as much as 80% of the total cyanobacterial biomass and contributed as much as 50% of the total primary production of a cyanobacterial bloom. The picocyanobacteria are incapable of fixing N2, do not possess gas vesicles and are not toxic. However, a small filamentous Pseudanabaena sp. that could potentially fix N2 was isolated from the picocyanobacteria fraction. The larger cyanobacteria may form surface scums because they possess gas vesicles that make them buoyant. Although their biomass was less than the picocyanobacteria, they therefore form the more conspicuous and nuisance-forming part of the bloom. The larger cyanobacteria were composed mainly of three different species: Nodularia spumigena, Aphanizomenon flos-aquae and Anabaena sp. These all belong to the heterocystous, N2-fixing cyanobacteria. N. spumigena and A. flos-aquae were the dominant species; only N. spumigena was toxic. Although individual Nodularia filaments showed a range of different phenotypes, they all belong to one species as judged from 16S rDNA sequencing. Through determination of the genotypes of many individual Nodularia filaments, it was shown that this population was not clonal and that horizontal exchange of genetic information occurs. N. spumigena and A. flos-aquae were different with respect to their photosynthetic and N2-fixing potentials. Depending on prevailing environmental conditions, these differences would promote the proliferation of one species over the other and hence would determine overall the toxicity of a bloom. Daily integrals of photon irradiance rather than temperature determined the onset of bloom formation. During a bloom, the diazotrophic cyanobacteria fixed N2 at a rate that was 10–20% in excess of their own demand for N. Picocyanobacteria assimilated most of this excess N as shown by 15N incorporation. During bloom conditions, the diazotrophic cyanobacteria met about 50% of the N demand of the total cyanobacterial community. The picocyanobacteria were predominantly N-limited while the diazotrophic cyanobacteria were probably iron limited. These findings allow us to understand the formation of toxic cyanobacterial blooms and also to develop tools to predict bloom formation.

Description: ottom simulating reflectors (BSRs) were detected in multichannel seismic reflection data acquired in the vicinity of Isla Mocha across the southern Chile margin and near 33°S. Geothermal gradients were determined from the depth of the BSR that is interpreted to mark the thermally controlled base of a gas hydrate layer. Ground truth for the assessment and additional thermal constraints were provided by downhole measurements obtained during Ocean Drilling Program (ODP) Leg 202 in Site 1233 at 41°S and Sites 1234 and 1235 near 36°S. Both BSR-derived data and downhole temperatures were used to calculate heat flow anomalies and provide new constraints on the thermal regime of the continental slope and downgoing slab in Chile between 32°S and 41°S. Downhole chemical logs of Th, U, and K from Site 859 of ODP Leg 141 have been used to assess the radiogenic heat production in the margin wedge. Heat production is low (∼0.8 μW/m3). However, knowledge of this reduces the errors of estimating the contribution from frictional heating along the subduction thrust fault. With respect to the Eocene age of the incoming oceanic lithosphere, heat flow appears to decrease landward of the deformation front as expected due to the advective transport of heat into the subduction zone by the downgoing slab. Calculations of conductive fore-arc heat flow show that the modelled seafloor heat flow agrees with the measured heat flow only if there is negligible frictional heating. At 33°S, temperatures in the fault zone reach 100°C approximately 60 km landward of the deformation front and are coincident with the onset of earthquake activity and hence mark the up-dip limit of the seismogenic zone. The up-dip limit shifts seaward going to the south, reflecting the progressive southward decrease of lithospheric age of the subducting plate.

Description: The sedimentary facies, sediment dynamics and sequence architecture of modern high-energy shelves in the mid and high latitudes are largely governed by wave abrasion processes. Cool-water carbonates may form there, if the influx and/or net accretion of siliciclastics is kept at a minimum. Little dilution of the carbonate produced in situ is generally promoted by a wide “epicontinental” shelf, subdued topography of the adjacent mainland, the predominance of limestone outcrops, and an arid climate. The aforementioned requirements are rarely met, and thus will automatically lead to the formation of mixed siliciclastic–cool-water carbonates. Such an example is found in the Early to Mid-Miocene Lagos-Portimão Formation (Algarve, S-Portugal), which formed on a narrow high-energy shelf of the Atlantic Ocean that was bounded by a mountain range. The sediments of the formation consist of fossiliferous sandstone (FS), shell beds, and rhodolith blankets. Along strike, the stratification of the formation is monotonous for tens of kilometres and well exposed in coastal cliffs, whereas no outcrops of dip sections exist. The bulk skeletal composition of the sediments is typical for the warm-temperate climatic zone: various endo- and epibenthic bivalves, bryozoans, coralline algae, echinoderms, gastropods, and large foraminifers (Heterostegina). In some very rare beds, a few isolated, not framework-forming specimens of zooxanthellate corals (Porites, Tarbellastrea) indicate temporally elevated surface water temperatures close to the lower threshold of the coral reef ecosystem. In sandstones, the fauna is well preserved and burrowing bivalves are commonly found in life position. In limestone beds, the state of preservation of the grains ranges from intact to disintegrated and abraded specimens. We infer an accumulation of the shell beds through winnowing of fine materials (siliciclastic sand and carbonate mud) at wave abrasion depth and concentration of calcareous skeletons associated with the subsequent attraction of new epibiota in a complex shell bed. The vertical alternation of fossiliferous sandstone and shell beds, and in-phase variations of the “Photo Index” (photic biota vs. bryozoans) and “Bryozoan Index” (bivalves vs. bryozoans) is envisaged to document variations of water depth (and sea level). Sandstone units built up when wave abrasion depth (WAD) rose above the sea floor during TST (and early HST), whereas the shell beds formed during LST when the WAD for sand intersected with the sea floor. Clastic sediments were probably brought on the outer shelf during early transgression, and by longshore currents. Sea-level signatures inferred in the mixed siliciclastic–cool-water carbonate shelf setting of S-Portugal therefore significantly deviate from conventional concepts of carbonate sequence stratigraphy, which were developed for flat-topped platforms. Successful interpretations of ancient mixed sequences must therefore take into consideration the processes of production, concentration and accretion of the carbonate sediments.

Description: The concentrations of dissolved and suspended particulate Cd, Cu and Zn have been determined in water samples obtained during two axial transects of the Rio Tinto-Huelva Ria system in south-west Spain, which is severely impacted by acid mine drainage. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and, in the upper estuary, constituted 〉99 of total metal in the water column. Dissolved metals behaved non-conservatively on each transect, with maximum concentrations in the low salinity region. There was no evidence of metal adsorption within the turbidity maximum zone, despite the high specific surface areas of resuspending particles. Measurements of electrophoretic mobility showed that the suspended particulate matter (SPM) had a positive surface charge in the salinity range 0-4, where the waters had a pH〈3. Desorption experiments were carried out in which SPM from the turbidity maximum zone was resuspended in coastal seawater. The desorption of the metals was monitored for 24 h, using anodic stripping voltammetry (ASV) to detect the variation in total dissolved Cd, Cu and Zn and the species of Cu and Zn. Total dissolved Cd concentrations doubled during the incubation period, whereas the concentration of total dissolved Cu declined and that of Zn remained rather constant. The ASV-labile fraction of dissolved Cu and Zn showed an initial sharp release followed by a slower uptake. However, desorption was shown to be a minor source of dissolved metals and made little contribution to the non-conservative behaviour in the low salinity zone. The results are used to predict the effects of acid mine drainage on estuarine ecology. © 2002 Elsevier Science Ltd. All rights reserved.

Description: Topoisomerase IIalpha (top2) is a target of some of the most useful anticancer drugs. All clinically approved top2 drugs act to stabilize a drug-enzyme-DNA cleavable complex. Here we report the novel top2 activity of neoamphimedine, an isomer of the marine pyridoacridine amphimedine. Neoamphimedine was cytotoxic in yeast and mammalian cell lines. Neoamphimedine exhibited enhanced toxicity in top2 over-expressing yeast cells and was toxic in every mammalian cell line tested. However, neoamphimedine did not possess enhanced toxicity in a mammalian cell line sensitive to stabilized cleavable complexes. Therefore, we hypothesized that neoamphimedine is a top2-dependent drug, whose primary mechanism of action is not the stabilization of cleavable complexes. Top2-directed activity was determined in purified enzyme systems. Neoamphimedine-induced catenation of plasmid DNA only in the presence of active top2. This catenation correlated with the ability of neoamphimedine to aggregate DNA. Catenation was also observed using a filter-binding assay and transmission electron microscopy. Catenation was confirmed when only restriction enzyme digestion could resolve the catenated plasmid complex to monomer length plasmid DNA. Neoamphimedine also showed potent anti-neoplastic activity in human xenograft tumors in athymic mice. Neoamphimedine was as effective as etoposide in mice bearing KB tumors and as effective as 9-aminocamptothecin in mice bearing HCT-116 tumors. Amphimedine did not induce DNA aggregation or catenation in vitro, nor did it display any significant anti-neoplastic activity. These results suggest that neoamphimedine has a novel top2-mediated mechanism of cytotoxicity and anticancer potential.

Description: This paper discusses the distribution of dissolved Cu and Co in coastal surface waters of the western North Sea. High resolution data (more than 5500 (Cu) and 12000 (Co) data points), obtained using on-line flow-analysis techniques, clearly showed enhanced trace metal levels near the coast and estuarine outflows. In an offshore direction, the high metal levels were gradually diluted with metal-depleted seawater originating in the North Atlantic. The data indicated benthic sources for Cu and Co due to diagenetic remobilisation, sediment resuspension with injection of interstitial waters into the overlaying water and/or desorption from resuspended particles. Some evidence of biological removal of dissolved Cu was apparent in offshore coastal waters with enhanced chlorophyll concentrations. The study demonstrates how high resolution trace metal data allows us to deconvolute complex metal input and removal processes in dynamic coastal waters. © 2003 Elsevier Science Ltd. All rights reserved.

Description: The Rio Tinto and Rio Odiel drain the Iberian Pyrite Belt, an important metal-rich sulphide deposit. The rivers are highly acidic (pH 2.2-3.6) and have milli-molar SO4 and Fe concentrations and micro-molar Co, Cu, Mn and Zn concentrations. Observed dissolved metal levels were at a maximum during autumn and early winter surveys (e.g. Rio Tinto: 460-856 μM Cu), and lower in late winter, spring and summer (121-175 μM Cu). This variability is attributed to the production of concentrated acid mine drainage (AMD) during periods of enhanced microbial activity at higher temperatures in summer, and a subsequent run-off of the AMD into the rivers with the first rain in the autumn. Lower temperatures and dilution by winter floods resulted in a reduction of river metal concentration towards the end of the wet season. Metal distributions in the estuarine mixing zones of the Tinto and Odiel were governed by the acidity. The lack of metal transfer from the dissolved to the particulate phase in the low salinity region is attributed to the electrostatic repulsion between the metal cations and positive charges on particle surfaces, and/or to the protonation of adsorption sites at low pH. Dissolved Pb was an exception and showed marked removal in the low salinity zone at low pH (pH 2.5), due to its particle reactive nature. The gross metal fluxes from the Rio Tinto and Rio Odiel are important on a global scale, for example amounting to 8.1 and 1.6 of the estimated global riverine dissolved Zn and Cu fluxes. The fluxes of metals from the estuary contribute to enhanced dissolved metal concentrations observed in the Gulf of Cadiz. © 2003 Elsevier Ltd. All rights reserved.

Description: Atmospheric iron and underway sea-surface dissolved (〈0.2 μm) iron (DFe) concentrations were investigated along a north-south transect in the eastern Atlantic Ocean (27°N/16°W-19°S/5°E). Fe concentrations in aerosols and dry deposition fluxes of soluble Fe were at least two orders of magnitude higher in the Saharan dust plume than at the equator or at the extreme south of the transect. A weaker source of atmospheric Fe was also observed in the South Atlantic, possibly originating in southern Africa via the north-easterly outflow of the Angolan plume. Estimations of total atmospheric deposition fluxes (dry plus wet) of soluble Fe suggested that wet deposition dominated in the intertropical convergence zone, due to the very high amount of precipitation and to the fact that a substantial part of Fe was delivered in dissolved form. On the other hand, dry deposition dominated in the other regions of the transect (73-97), where rainfall rates were much lower. Underway sea-surface DFe concentrations ranged 0.02-1.1 nM. Such low values (0.02 nM) are reported for the first time in the Atlantic Ocean and may be (co)-limiting for primary production. A significant correlation (Spearman's rho = 0.862, p〈0.01) was observed between mean DFe concentrations and total atmospheric deposition fluxes, confirming the importance of atmospheric deposition on the iron cycle in the Atlantic. Residence time of DFe in the surface waters relative to atmospheric inputs were estimated in the northern part of our study area (17 ± 8 to 28 ± 16 d). These values confirmed the rapid removal of Fe from the surface waters, possibly by colloidal aggregation. © 2003 Elsevier Ltd. All rights reserved.

Description: A shipboard analytical intercomparison of dissolved (〈0.2 μm) iron in the surface waters of the Atlantic Ocean was undertaken during October 2000. A single underway surface (1-2 m) seawater sampling and filtration protocol was used, in order to minimise differences from possible sample contamination. Over 200 samples (1/h) were collected over 12 days and analysed immediately using four different analytical methods, based on three variants of flow injection with luminol chemiluminescence (FI-CL) and cathodic stripping voltammetry (CSV). Dissolved iron concentrations varied between 0.02 and 1.61 nM during the intercomparison. On average, CSV Electroanalysis 12 (2000) 565 measured 0.08 nM higher iron concentrations than one FI-CL method Anal. Chim. Acta 361 (1998) 189, which measured 0.13 nM higher iron values than the other two Anal. Chem. 65 (1993) 1524; Anal. Chim. Acta 377 (1998) 113, Statistical analyses (paired two-tailed t-test) showed that each analytical method gave significantly different dissolved iron concentrations at the 95% confidence interval. These data however, represent a significant improvement over earlier intercomparison exercises for iron. The data have been evaluated with respect to accuracy and overall inter-laboratory replicate precision, which was generally better than the 95% confidence intervals reported for the NASS Certified Reference Materials. Systematic differences between analytical methods were probably due to the extraction of different physico-chemical forms of iron during preconcentration, either on the micro-column resin (in the FI methods) or with competing ligand equilibration (in the CSV method). Small systematic concentration differences may also have resulted from protocols used for quantification of the analytical blank and instrument calibration. © 2003 Elsevier B.V All rights reserved.

Description: Studies on nitrogen in natural waters have generally focussed on dissolved inorganic nitrogen (DIN), primarily because of relative ease of analysis and the important influence of DIN on water quality. Advances in analytical techniques now permit the systematic study of dissolved organic nitrogen (DON), and this work has shown that DON is quantitatively significant in many waters. This article describes the sampling and analytical protocols required for rapid, precise and reliable determinations of DON, involving high-temperature catalytic oxidation (HTCO), coupled to chemiluminescence detection. This approach simultaneously determines dissolved organic carbon (DOC) and total dissolved nitrogen (TDN), and DON is derived by subtraction of DIN measured by colorimetry. The DON determination is simple to perform, exhibits excellent precision (〈1 for C and 1.5 for N) and is applicable to a wide range of natural waters. © 2003 Published by Elsevier B.V.

Description: Developments in instrument miniaturisation and automation have resulted in the manufacture of portable electrochemical instrumentation for continuous trace-metal measurements from the banks of estuaries and on board ships. The most recent developments in flow cells with gel-coated iridium (Ir) micro-electrode arrays have resulted in submersible in situ voltammetric probes that allow long-term trace-metal monitoring at sub-nanomolar concentrations in coastal waters. This article overviews the design and the application of field-deployable voltammetric instrumentation for trace-metal monitoring. © 2003 Published by Elsevier B.V.

Description: Time-dependent sorption experiments have been carried out under controlled laboratory conditions, using filtered river water and particles from the turbidity maximum zone (TMZ) of the Tamar Estuary (UK). Adsorptive cathodic stripping voltammetry (ACSV) was used to determine ACSV labile and total dissolved Cu and Ni, without prior sample handling and/or pre-concentration. The ACSV metal lability is theoretically defined and is dependent upon the α-coefficient (αMAL) of the added ACSV ligand. The fraction of labile dissolved Cu in the river water was in the range 28-41 of the total, while labile Ni was 80-90 of the total dissolved Ni. After 24 h incubation with the particles, the concentration of total dissolved Cu was reduced to half the original value and involved the removal of 40 of labile Cu and 70 of the non-labile Cu. Removal of total dissolved Ni after 24h ranged from 40 to 60 and the uptake kinetics were dominated by adsorption of labile Ni. The kinetics of adsorption for the different chemical forms of Cu and Ni were interpreted by assuming a first-order reversible reaction between the dissolved components and the particulate phase. The chemical response time for the removal of labile Cu was 1.1 and 0.5 h for non-labile Cu. The chemical response time for labile Ni was in a range from 0.7 to 0.3 h. The results are interpreted in terms of the role played by chemical kinetics in determining the phase transport of metals in the reactive zones of estuaries. © 2003 Elsevier Science B.V. All rights reserved.

Description: In the western Baltic Sea, the highly competitive blue mussel Mytilus edulis tends to monopolize shallow water hard substrata. In many habitats, mussel dominance is mainly controlled by the generalist predator Carcinus maenas. These predator-prey interactions seem to be affected by mussel size (relative to crab size) and mussel epibionts. There is a clear relationship between prey size and predator size as suggested by the optimal foraging theory: Each crab size class preferentially preys on a certain mussel size class. Preferred prey size increases with crab size. Epibionts on Mytilus, however, influence this simple pattern of feeding preferences by crabs. When offered similarly sized mussels, crabs prefer Balanus-fouled mussels over clean mussels. There is, however, a hierarchy of factors: the influence of attractive epibiotic barnacles is weaker than the factor 'mussel size'. Testing small mussels against large mussels, presence or absence of epibiotic barnacles does not significantly alter preferences caused by mussel size. Balanus enhanced crab predation on mussels in two ways: Additional food gain and, probably more important, improvement in handling of the prey. The latter effect is illustrated by the fact that artificial barnacle mimics increased crab predation on mussels to the same extent as do live barnacles. We conclude that crab predation preferences follows the optimal foraging model when prey belong to different size classes, whereas within size classes crab preferences is controlled by epibionts

Description: Morphodynamic modeling is employed in the present work to predict the long-term evolution (over the next 100 years) of typical sedimentary coasts in the western Russian Arctic. The studied objects are the coasts of Varandey (the Barents Sea), Baydaratskaya Bay and Harasavey (the Kara Sea). The model developed takes into account both the short-term processes (storm events) and long-term factors (for example, changes in sea level, inter-annual variations in gross sediment flux, lack or excess of sediment supply). Predicted and observed morphological changes in coastal profiles are shown to agree well for time scales ranging from weeks to decades. It is revealed that under given environmental conditions, the morphological evolution is strongly influenced by storm surges and associated wind-driven circulation. The water level gradient created by a surge generates a seaward flow at the bed. This outflow is shown to be an important destructive mechanism contributing to the erosion and recession of Arctic coasts. The rate of change is found to depend on both the exposure of the coast (relative to the direction of dominant winds) and its height above the sea. The open coast of Varandey is expected to retreat as much as 300–500 m over 100 years, while recession of the less exposed coasts of Baydaratskaya Bay would not exceed about 100 m/century. If long-term sediment losses are insignificant, the rate of erosion decays with time and the morphodynamic system may tend toward equilibrium. It is concluded that the expected relative sea-level rise (up to 1 m over the nearest 100 years) is non-crucial to the future coastal evolution if an erosion activity is already high enough.

Description: The distributions of chemicals within the ocean are governed by a variety of biological, chemical, physical, and geological processes. The relative importance of each process in controlling a geochemical element's distribution varies from substance to substance, depending on its chemical reactivity and role in various biogeochemical cycles. Often, these processes are poorly understood and inextricably intertwined. Consider, for example, the distribution of dissolved oxygen in the Atlantic.

Description: Two new compounds isolated from an extract of a Central Asian lichen [Umbilicaria proboscidea (L.) Schrader=Syn.: Gyrophora proboscidea (L.) Ach.] are glucosides with mono- and di-prenylated xanthones as the aglycones and a saccharide moiety from two glucoses linked at C-7. The structures were elucidated on the basis of extensive spectroscopic analysis (1D and 2D NMR, MS, IR and UV) and by hydrolysis. Two new compounds (1, 2) isolated from an extract of a Central Asian lichen [Umbilicaria proboscidea (L.)] Schrader are glucosides with mono- and di-prenylated xanthones as the aglycones and a saccharide moiety from two glucoses linked at C-7. The structures were elucidated on the basis of extensive spectroscopic analysis (1D and 2D NMR, MS, IR and UV) and by hydrolysis.

Description: Analysis of three recent diagenetic model codes (OMEXDIA, CANDI and STEADYSED) revealed that codes have a rigid, static and problem-specific character, leaving little autonomy for the application user. The resulting lack of flexibility and extensibility, and the associated need for ground-level reprogramming, constitutes a major barrier for potential model users. Present codes have apparently passed a critical threshold of code complexity, above which code development becomes time-consuming and expensive using the present procedure-oriented techniques. We have explored the advantages of object-oriented technology and the concept of a problem-solving environment to improve the quality of software for reactive transport modelling. A general blueprint for an object-oriented code for modelling early diagenesis is presented. The MEDIA environment consists of a toolbox of building blocks (element, species and process objects), which can be combined freely by the user to construct new models (without the need for recompilation). An object-oriented database stores current objects and accommodates new user-defined building blocks. Altogether, it is advocated that by improving the software quality, one can substantially lower the threshold for using model codes as an integrated data-analysis tool.

Description: We investigated the stomach contents of Dall's porpoises collected in pelagic waters spanning most of their range in the North Pacific and the Bering Sea. Analysis revealed the porpoises fed mainly on myctophid fishes in the subarctic North Pacific and on gonatid squids as well as myctophid fishes in the Bering Sea. Most of the prey items were mesopelagic micronekton, primarily fishes and squids that migrate vertically to shallower waters at night. Stomach content was greater during twilight hours, suggesting the porpoises foraged actively on myctophids at night in shallower waters. Stomach contents were strongly characterized by local mesopelagic prey fauna, and prey species selectivity was not apparent. The annual consumption by Dall's porpoises was estimated to be 2.0–2.8 million tons, or 4.7–6.5% of the biomass of mesopelagic fishes in the subarctic North Pacific, and may account for approximately 24–33% of the overall mortality of mesopelagic micronekton, especially myctophids. Myctophids are also common, but less important, prey of other subarctic predators. Dall's porpoises are likely the primary consumers of myctophids in the subarctic North Pacific. Since myctophids are the major component of the mesotrophic level, the trophic relationship between myctophids and Dall's porpoises is thought to be an important pathway of mass and energy in the pelagic food web in the subarctic North Pacific.

Description: The influence of both predator and prey size on the shift from a pulling to a drilling predatory response was examined in the intertidal octopus Octopus dierythraeus, using an experimental program. Additionally, selective drilling, where particular regions of the prey are targeted, was examined for a variety of bivalve and gastropod prey. O. dierythraeus always initially attempted to pull bivalves apart. Shells that were eventually drilled were always subjected to significantly more pulling attempts than those that could be pulled apart, indicating that octopus are willing to expend more energy to access the flesh quickly. There was no defined threshold where bivalve size caused an octopus to switch from a pulling to a drilling response. Instead, there was a broad size range where the octopus could adopt either handling method and it varied for each individual. Octopus may only able to pull open bivalves before the molecular ratchet or ‘catch’ mechanism that many bivalves possess is engaged. This might explain the lack of a relationship between either octopus or bivalve size and the success of pulling, as it is likely that when the bivalves were presented to individual octopus they were either setting the ‘catch’ mechanism, or had already engaged it. O. dierythraeus demonstrated selective drilling on a variety of molluscan prey, with penetration sites differing between prey species. O. dierythraeus targeted the valve periphery, which was the thinnest part of the shell, therefore minimizing handling time. O. dierythraeus always drilled gastropods, but did not target the thinnest regions of the shells, with drill site varying according to the morphology of the prey. Elongate species with pronounced aperture lips were drilled in the apical region, close to the columella on the side of the opercula whereas nonelongate species were drilled immediately above the aperture. The location of drilling sites may represent a trade-off between targeting the most effective places to inject paralyzing secretions and the mechanically simplest places to drill.

Description: We analyse the cephalopod–parasite systems taking into account the abiotic and biotic factors that may affect the host risk of infection (contact) with parasites. On the basis of 2000 individuals comprising 10 cephalopod species collected at a microgeographic area (Galician waters, NW Spain), an attempt is made to find associations between parasite relative species diversity (RSD) and cephalopod life cycle characteristics. Additionally, an index of similarity and the ratios of adult/immature (A/I) and specialist/generalist (S/G) regarding the parasite condition were used to define cephalopod ecological groupings at those species with similar risk of becoming infected with a given parasite fauna. Results show the existence of three ecological groupings (coastal, intermediate, and nerito-oceanic), which suggest that the ecological niche of a cephalopod species is more important in determining its risk of parasitic infection than is phylogeny.

Description: This paper describes the history of cephalopod fisheries in Chile over the past 40 years. Continuous monitoring of three species was undertaken between 1978 and 1999: Loligo gahi, Dosidicus gigas and Octopus mimus. Total cephalopod catches increased from 69 tonnes in 1978 (0.13% total mollusc catch) to 3503 tonnes in 1996 (3.64%). A maximum haul of 15,169 tonnes was taken in 1992 (11.27% total mollusc catch). Small-scale fisheries accounted for the majority of cephalopod captures and industrial catches were rare. L. gahi is caught year-round mainly in the south of Chile, with maximum catches in summer and autumn. Catches of D. gigas are also year-round, mainly concentrated in central Chile. O. mimus has been fished since 1978, although recorded as Octopus vulgaris until the 1990s. The O. mimus fishery is located on the north coast of Chile, and catches are made for the most of the year. Octopus has been landed in the south of Chile since 1991, and is considered as O. mimus in capture statistics despite the fact that several species are represented, including Enteroctopus megalocyathus.

Description: Dissolved organic matter (DOM) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils. Tremendous strides have been made in the past 25 years to more fully describe the composition of DOM and its role in soil. The papers in this special issue contribute to this literature by both summarizing recent research and reporting on new projects. Based on the papers presented here and others in the literature, I suggest that the following three questions would prove fruitful for future research on DOM in soils: (1) How large are various sources and sinks and how are they controlled?; (2) What is the ecological significance of dissolved organic nitrogen (DON) in comparison to dissolved organic carbon (DOC)?; (3) How are fluxes altered in human-dominated environments? In support of answering these questions, I recommend that emphasis be placed on developing new analytical techniques (isotopic, or detailed characterization of DOM constituents), increasing interchanges between aquatic and terrestrial biogeochemists and developing an integrated conceptual approach to the study of DOM in soils that addresses interactions among solid soil organic matter, microorganisms including fungi and mycorrhizal fungi, and DOM.

Description: The Illex illecebrosus fishery in the northwestern Atlantic Ocean is trawl-based. I. illecebrosus normally lives less than 1 year. One option for managing such a short-lived species is the use of catch and effort data obtained from fishing vessels during the fishing season to manage the fishery in real time. Verification of the accuracy of data reports is important. Conceivably, information contained in the data stream of vessel position and time provided by a remote data logger could be used to reconstruct the vessel’s activities to assess the reliability of industry reports. This study describes quantitatively the types of vessel operating activities that take place on a typical I. illecebrosus fishing trip and assesses the possibility of reconstructing these activities reliably from the simple data stream of vessel position and time. Seven activities were identified, six of which occurred commonly: steaming to and from port, searching, towing, set-up time between tows, steaming overnight and laying-to overnight. Processing the catch, as a discrete activity, occurred rarely. Each activity could be characterized in terms of its duration and distance traveled, the average vessel speed, and the tendency for vessel speed to change during the activity. Most activities were conducted in a linear manner. Accordingly, reasonable estimates of the distance and duration of these activities could be obtained simply from the knowledge of the starting and ending position and time. Analysis of search time and subsequent catch revealed that searching did not improve catch. More squid would have been caught had the vessels used this time for towing. Catch per unit effort (CPUE) can be calculated using duration or distance in the denominator. In this set of fishing trips, the two were equivalent. Catch bore a nonlinear relationship with CPUE. In particular, larger catches were associated with incrementally larger CPUEs. The uniqueness of each activity when described by its characteristic speed, duration and distance, and the consistency of these characteristics for each activity between vessels suggests that vessel behavior might be assessed remotely using a time series of position and time. Such a capability might be important in any real-time management plan where industry vessels necessarily must be depended upon for data on catch and CPUE.

Description: The combined effects of photoperiod and feeding frequency on survival and growth of juvenile cuttlefish has been studied in experimental rearing. During juvenile cuttlefish growth, survival and growth rate were low when the photoperiod was short (8 h of light and 16 h of dark). Increased frequency of diet did not stimulate the appetite of animals reared in normal or long photoperiod (16 h of light and 8 h of dark). However, by studying the combined effects of photoperiod and feeding frequency, we have demonstrated that an increase in feeding frequency can enhance survival and growth in the group receiving the shortest period of light per day. Temperature is an important factor in the regulation of the incubation period of eggs and of growth after hatching, but it also appears in this investigation that the combined effect of photoperiod and feeding frequency must be considered during growth of juvenile cuttlefish.

Description: Gauss–Seidel is often the smoother of choice within multigrid applications. In the context of unstructured meshes, however, maintaining good parallel efficiency is difficult with multiplicative iterative methods such as Gauss–Seidel. This leads us to consider alternative smoothers. We discuss the computational advantages of polynomial smoothers within parallel multigrid algorithms for positive definite symmetric systems. Two particular polynomials are considered: Chebyshev and a multilevel specific polynomial. The advantages of polynomial smoothing over traditional smoothers such as Gauss–Seidel are illustrated on several applications: Poisson’s equation, thin-body elasticity, and eddy current approximations to Maxwell’s equations. While parallelizing the Gauss–Seidel method typically involves a compromise between a scalable convergence rate and maintaining high flop rates, polynomial smoothers achieve parallel scalable multigrid convergence rates without sacrificing flop rates. We show that, although parallel computers are the main motivation, polynomial smoothers are often surprisingly competitive with Gauss–Seidel smoothers on serial machines.

Description: A hydrate state-of-the-art is given for fundamental measurements and modeling of phase equilibria and kinetics, via a 204 paper summary of the triennial International Hydrate Conference in May 2002. Emphasis is given to new measurement techniques with their application in the next generation of hydrate modeling. Future challenges are presented. With this Phase Equilibria Plenary Lecture in the 17th International Conference on Chemical Thermodynamics, goes my appreciation for both the honor, and the motivation to attempt a state-of-the-art summary. All too frequently such summaries take on a personal perspective that omit important developments, perhaps because they were not developed by the writer, and were therefore less familiar. Yet currently we are two months after the fourth triennial International Conferences on Gas Hydrates (Yokohama, Japan, 19–23 May 2002). That conference was blessed with a chairman who provided two volumes (1062 pages) written by 500 (even!) authors. A CD of conference papers is available at nominal cost through the ICGH-4 Secretariat (icgh@mori.mech.keio.ac.jp). The challenge of this invited manuscript is to provide a pure and applied phase equilibria summary of the above conference, supplemented by a few other references, in an overview of the hydrate community’s current direction. The conference provides a technical snapshot of hydrate research over the world, making it possible to weave a few current threads into the hydrate fabric in space and time. Emerging images provide some clues to the future. To supplement this view the reader may wish to turn to the other reviews [1], [2], [3], [4], [5], [6] on pure and applied phase equilibria of hydrates.

Description: The MEDIA (Modelling Early DIAgenesis) software package comprises a flexible and extensible software system that provides problem-solving assistance for simulating 1D reactive transport in surface sediments. MEDIA allows multiple diagenetic models to be built by extending a model template with new model components from a toolbox of available objects (elements, species, parameters, reactions). A detailed review is given of the transport and reaction components available for model construction. Upon assemblage, the model is channelled to the numerical subunit of the MEDIA package. Via a canonical transformation, the user-defined mixed kinetic-equilibrium model is rearranged into a proper set of differential algebraic equations (DAE), for which both steady state and transient solutions can be calculated. Steady-state profiles are obtained either directly using a Newton–Raphson method, or alternatively, as the asymptotic result of a dynamic simulation. Dynamic simulations involve a global implicit procedure based on the stiff-ODE solver package VODE, employing a direct substitution approach to reduce the number of equations in the DAE system. Verification of the MEDIA code was accomplished (1) by comparison with analytic models and (2) by emulating the model formulation and output of the existing diagenetic model code STEADYSED. As an example application, a diagenetic model was constructed to analyse an extensive dataset collected from a marine sediment in the Santa Barbara Basin (California). The different pathways of organic matter mineralization were modelled, and the coupling among the biogeochemical cycles of C, O, N, S, Mn and Fe was investigated. Depth profiles of both porewater and solid-phase constituents could be reproduced with great accuracy.