ALBERT

Description: Are the rare earth elements (REEs) in foraminifera a valuable proxy for use in paleoceanographic and climate change studies? In order to investigate this, we attempted a comprehensive study of REEs in planktonic and benthic foraminifera. Several different cleaning protocols were tested. Although the hydroxylamine used to clean all foraminifera in this study removes an unidentified source of REE contamination, it seems to remobilize metal oxides that are otherwise unaffected in flow-through dissolution. The calculated REE distribution coefficients, KD(REE)s, are between 100 and 500 for both planktonic and benthic foraminifera. These KDs are high compared to other elements in biogenic calcite but can be explained through a general model of element incorporation during foraminiferal calcification. From data taken from eight core tops in the southeast Pacific, we conclude that the REEs in planktonic foraminifera are, indeed, useful as a proxy for upper ocean water mass and mixed layer biogenic productivity. Alternatively, the REEs in benthic foraminifera are useful as a proxy for carbon flux to the sea floor. These proxies should be robust down core unless the sediments have undergone anoxic diagenesis, which stabilizes Fe carbonate thus overprinting the primary REE signature. However, it is clear from REE distributions in foraminiferal tests if anoxic conditions have occurred.

Description: A novel strategy is proposed for the efficient simulation of geochemical tracers in ocean models. The method captures the tracer advection and diffusion in a general circulation model (GCM) without any alteration (or even knowledge) of the GCM code. In comparison with offline tracer models, the proposed method is considerably more efficient and automatically includes all parameterizations of unresolved processes present in the most sophisticated GCMs. A comparison with a global configuration of the MIT GCM shows that the scheme can capture the complex three-dimensional transport of a state-of-the-art GCM. A key advantage of the proposed technique is the ability to directly compute steady-state solutions, a facility particularly well-suited to tracers such as natural radiocarbon. This capability is applied to develop a novel algorithm for accelerating the dynamical adjustment of ocean models.

Description: The distribution and evolution of water masses along the East Greenland Current (EGC) from south of the Fram Strait to the Denmark Strait were investigated using chlorofluorocarbons (CFCs) and the released tracer sulphur hexafluoride (SF6) together with hydrographic data. Water masses contributing to the Denmark Strait overflow, and to some extent also contributions to the Iceland–Scotland overflow, are discussed from observations in 1999. Special emphasis is put on the advection and mixing of Greenland Sea Arctic Intermediate Water (GSAIW), which could be effectively traced thanks to the release of sulphur hexafluoride in the Greenland Sea Gyre in 1996. By means of the dispersion of the tracer, Greenland Sea Arctic Intermediate Water was followed down to the Denmark Strait Sill as well as close to the Faroe–Shetland Channel. The results indicate that this water mass can contribute to both overflows within 3 years from leaving the Greenland Sea. The transformation of Greenland Sea Arctic Intermediate Water was dominated by water from the Arctic Ocean, especially by isopycnal mixing with upper Polar Deep Water (uPDW) but, to a less extent, also by Canadian Basin Deep Water. A mixture of Greenland Sea Arctic Intermediate Water and upper Polar Deep Water was lifted 500 m on its way through southwestern Iceland Sea, to a depth shallow enough to let it reach the sill of the Denmark Strait from where it can be incorporated in the densest layer of the overflow. The observations show contributions to the Denmark Strait overflow from both the East Greenland Current and the Iceland Sea.

Description: Sediment core data from a site in the central Nordic seas suggest that during the mid-Pleistocene revolution (MPR) this region has experienced a systematic change in its overall oceanographic and climatic conditions. First distinct changes occur around 1 Ma and reveal the beginning of a shift in climate periodicity from stronger 41-ka cycles towards a dominant 100-ka cyclicity. Most pronounced are the changes at the study region between about 700 and 420 ka, when parallel to the evolution of large 100-ka cycles a distinct decrease in the input of magnetic particles is observed. Also, for this interval an intensification of glacial conditions is indicated by a marked increase in the accumulation rates of ice-rafted debris (IRD) during marine isotope stages 16 and 12. The observed mid-Pleistocene changes were likely due to a gradual shift from a more zonal behavior of the coupled ocean–atmosphere system at high northern latitudes prior to the MPR to more meridionality thereafter, a shift that affected both the patterns of ocean circulation and ice drift in the Nordic seas region. Accordingly, the subsequent MPR-related changes of these two climate parameters should be responsible for the decrease in the concentration of magnetic particles at the study site after 700 ka. With the mid-Pleistocene strengthening of the Nordic heat pump the mode of deep-water production and the flow of bottom currents changed at high northern latitudes, which led to an increased export of magnetic particles from basaltic source regions around Greenland and Iceland into the subpolar North Atlantic. Consequently, less magnetic material was deposited in the Nordic seas than before the MPR when water mass exchange between the Nordic seas and the North Atlantic was more restricted. In addition, the large Late-Pleistocene expansions of glacial ice caps on the eastern margin of the Nordic seas led to a major change in the composition of IRD material in the study area, with more material originating from the Scandinavian and Barents Sea shelf regions, which ultimately caused a dilution of the magnetic signal.

Description: We review current knowledge and understanding of the biology and ecology of the calanoid copepod Calanus helgolandicus in European waters, as well as provide a collaborative synthesis of data from 18 laboratories and 26 sampling stations in areas distributed from the northern North Sea to the Aegean and Levantine Seas. This network of zooplankton time-series stations has enabled us to collect and synthesise seasonal and multi-annual data on abundance, body size, fecundity, hatching success and vertical distribution of C. helgolandicus. An aim was to enable comparison with its congener Calanus finmarchicus, which has been studied intensively as a key component of European and north east Atlantic marine ecosystems. C. finmarchicus is known to over-winter at depth, whereas the life-cycle of C. helgolandicus is less well understood. Overwintering populations of C. helgolandicus have been observed off the Atlantic coast between 400 and 800 m, while in the Mediterranean there is evidence of significant deep-water populations at depths as great as 4200 m. The biogeographical distribution of C. helgolandicus in European coastal waters covers a wide range of habitats, from open ocean to coastal environments, and its contribution to mesozooplankton biomass ranges from 6% to 93%. Highest abundances were recorded in the Adriatic and off the west coast of Spain. C. helgolandicus is generally found in 9–20 °C water, with maximum abundances from 13–17 °C. In contrast, C. finmarchicus is found in cooler water between 0 and 15 °C, with peak abundances from 0 to 9 °C. As water has warmed in the North Atlantic over recent decades, the range of C. helgolandicus and its abundance on the fringes of its expanding range have increased. This review will facilitate development of population models of C. helgolandicus. This will not only help answer remaining questions but will improve our ability to forecast future changes, in response to a warming climate, in the abundance and distribution of this important species.

Description: 1. Why study the Arctic? 2. The Siberian shelf seas as sensitive “environmental recorder” 3. Outlook

Description: Transfers of some important biogenic atmospheric constituents, carbon dioxide (CO2), methane (CH4), molecular nitrogen (N2), nitrous oxide (N2O), nitrate View the MathML source(NO3-), ammonia (NH3), methylamines (MAs) and dimethylsulphide (DMS), across the air–sea interface are investigated using published data generated mostly during the Arabian Sea Process Study (1992–1997) of the Joint Global Ocean Flux Study (JGOFS). The most important contribution of the region to biogeochemical fluxes is through the production of N2 and N2O facilitated by an acute, mid-water deficiency of dissolved oxygen (O2); emissions of these gases to the atmosphere from the Arabian Sea are globally significant. For the other constituents, especially CO2, even though the surface concentrations and atmospheric fluxes exhibit extremely large variations both in space and time, arising from the unique physical forcing and associated biogeochemical environment, the overall significance in terms of their global fluxes is not much because of the relatively small area of the Arabian Sea. Distribution and air–sea exchanges of some of these constituents are likely to be greatly influenced by alterations of the subsurface O2 field forced by human-induced eutrophication and/or modifications to the regional hydrography.

Description: Along the erosive convergent margin off Costa Rica a large number of mound-shaped structures exist built by mud diapirism or mud volcanism. One of these, Mound 12, an intermittently active mud volcano, currently emits large amounts of aqueous dissolved species and water. Chemosynthetic vent communities, authigenic carbonates, and methane plumes in the water column are manifestations of that activity. Benthic flux measurements were obtained by a video-guided Benthic Chamber Lander (BCL) deployed at a vent site located in the most active part of Mound 12. The lander was equipped with 4 independent chambers covering adjacent areas of the seafloor. Benthic fluxes were recorded by repeated sampling of the enclosed bottom waters while the underlying surface sediments were recovered with the lander after a deployment time of one day. One of the chambers was placed directly in the centre of an active vent marked by the occurrence of a bacterial mat while the other chambers were located at the fringe of the same vent system at a lateral distance of only 40 cm. A transport-reaction model was developed and applied to describe the concentration profiles in the pore water of the recovered surface sediments and the temporal evolution of the enclosed bottom water. Repeated model runs revealed that the best fit to the pore water and benthic chamber data is obtained with a flow velocity of 10 cm yr− 1 at the centre of the vent. The flux rates to the bottom water are strongly modified by the benthic turnover (benthic filter). The methane flux from below at the bacterial mat site is as high as 1032 μmol cm− 2 yr− 1, out of which 588 μmol cm− 2 yr− 1 is oxidised in the surface sediments by microbial consortia using sulphate as terminal electron acceptor and 440 μmol cm− 2 yr− 1 are seeping into the overlaying bottom water. Sulphide is transported to the surface by ascending fluids (238 μmol cm− 2 yr− 1) and is formed within the surface sediment by the anaerobic oxidation of methane (AOM, 588 μmol cm− 2 yr− 1). However, sulphide is not released into the bottom water but completely oxidized by oxygen and nitrate at the sediment/water interface. The oxygen and nitrate fluxes into the sediment are high (781 and 700 μmol cm− 2 yr− 1, respectively) and are mainly driven by the microbial oxidation of sulphide. Benthic fluxes were much lower in the other chambers placed in the fringe of the vent system. Thus, methane and oxygen fluxes of only 28 and 89 μmol cm− 2 yr− 1, respectively were recorded in one of these chambers. Our study shows that the aerobic oxidation of methane is much less efficient than the anaerobic oxidation of methane so that methane which is not oxidized within the sediment by AOM is almost completely released into the bottom water. Hence, anaerobic rather than aerobic methane oxidation plays the major role in the regulation of benthic methane fluxes. Moreover, we demonstrate that methane and oxygen fluxes at cold vent sites may vary up to 3 orders of magnitude over a lateral distance of only 40 cm indicating an extreme focussing of fluid flow and methane release at the seafloor.

Description: Measurements of Fe(II) and H2O2 were carried out in the Atlantic sector of the Southern Ocean during EisenEx, an iron enrichment experiment. Iron was added on three separate occasions, approximately every 8 days, as a ferrous sulfate (FeSO4) solution. Vertical profiles of Fe(II) showed maxima consistent with the plume of the iron infusion. While H2O2 profiles revealed a corresponding minima showing the effect of oxidation of Fe(II) by H2O2, observations showed detectable Fe(II) concentrations existed for up to 8 days after an iron infusion. H2O2 concentrations increased at the depth of the chlorophyll maximum when iron concentrations returned to pre-infusion concentrations (〈80 pM) possibly due to biological production related to iron reductase activity. In this work, Fe(II) and dissolved iron were used as tracers themselves for subsequent iron infusions when no further SF6 was added. EisenEx was subject to periods of weak and strong mixing. Slow mixing after the second infusion allowed significant concentrations of Fe(II) and Fe to exist for several days. During this time, dissolved and total iron in the infusion plume behaved almost conservatively as it was trapped between a relict mixed layer and a new rain-induced mixed layer. Using dissolved iron, a value for the vertical diffusion coefficient Kz = 6.7±0.7 cm2 s−1 was obtained for this 2-day period. During a subsequent surface survey of the iron-enriched patch, elevated levels of Fe(II) were found in surface waters presumably from Fe(II) dissolved in the rainwater that was falling at this time. Model results suggest that the reaction between uncomplexed Fe(III) and O2− was a significant source of Fe(II) during EisenEx and helped to maintain high levels of Fe(II) in the water column. This phenomenon may occur in iron enrichment experiments when two conditions are met: (i) When Fe is added to a system already saturated with regard to organic complexation and (ii) when mixing processes are slow, thereby reducing the dispersion of iron into under-saturated waters.

Description: A laboratory calibration study was undertaken with juvenile Sepia officinalis (80–85 g initial wet weight) to investigate the effects of different food rations and different starving intervals on RNA/dry weight (DW) ratios and RNA/DNA ratios in cephalopod mantle muscle at two different temperatures. The digestive gland index was also used as an additional indicator of recent growth. High food rations and low temperature went along with high RNA/DW ratios and high RNA/DNA ratios. Starving resulted in a linear decline in growth performance and a concomitant decrease in RNA/DW and RNA/DNA ratio, with RNA/DNA ratios representing the growth data better. RNA/DNA ratios decreased faster at higher temperatures. A fluorimetric assay for nucleic acid analysis was optimized for cephalopod mantle tissues and yielded reproducible RNA/DNA ratios with a relative variance below 10%. Thus, it may be possible to use this estimator of recently encountered feeding regime for the evaluation of mortality rates of early teuthid paralarvae to eventually support stock management. Also, log relative digestive gland weight showed a strong relationship with starving time, but, surprisingly, not with temperature. Data from the two temperatures analyzed could be combined to form a common regression line of relative digestive gland index with starving time. This indicator for recent growth might be especially suitable for large specimens with a well-developed digestive gland.

Description: We measured annual shell growth rates of a 374-year-old (radiometrically confirmed) bivalve mollusk specimen of Arctica islandica (Linnaeus). This bivalve represents the oldest ever reported individual animal. In addition, we analyzed 1051 individual powder samples from ontogenetic years two to 40 (= 80% of the entire shell height) for isotope analyses. Oxygen and carbon isotopes exhibit clear intra-annual cycles. The highest measured carbon isotope values (on average + 2.73‰) occurred during summer, i.e., during maximum primary productivity. The δ18Oaragonite-derived temperature time-series cover the period of AD 1496–1533. Temperatures calculated from oxygen isotopes ranged from 4.5 to 9.3 °C and exhibit a mean value of 6.2 °C. The latter coincides well with the 1854–2003 mean value of 6.81 °C for sea-surface temperature between February and September (= growing season of A. islandica). Neither oxygen nor carbon isotopes exhibit age-related, unidirectional trends. However, δ13Caragonite and δ18Oaragonite values fluctuated at decadal periods of four, six and eight to nine years (NAO-type periods) as well as 12–14 years which may represent teleconnections to cycles in the tropical Atlantic. Annual shell growth is positively correlated to intra-annual δ18Oaragonite minima, i.e., warm summer temperatures (R2 = 0.34), and to intra-annual δ13Caragonite minima (higher food supply; R2 = 0.42). Using a linear multiregression model, 65% of the variation in annual shell growth can be explained by summer temperature and food supply. The formation of extremely narrow annual increments coincides with major volcanic eruptions (e.g., Tambora 1815). A period of extremely variable growth occurred during the culmination of the Little Ice Age in Iceland between ca. AD 1550 and 1620. Shell growth during AD 1765–1780, however, was characterized by very little year-to-year variability, probably as the result of extremely mild climate near the end of the Little Ice Age. This study demonstrates that shells of A. islandica provide subseasonal to multidecadal, precisely dated multi-proxies of environmental variables from marine, mid to high latitudes. Such data can be used to validate and complement climate models and further assess human impact on climate and ecosystems.

Description: Based on hydrological data from 1979 to 1999 the average long-term salinity of the flaw polynya in the Eastern Laptev Sea is estimated. A new method to evaluate ice production based on hydrological rather than sea-ice observations is proposed. Average annual ice production in the polynya ranges between 3 and 4 m. The probability of convective mixing penetrating down to the seafloor is highest in the regions of the flaw polynya, but does not exceed 20% in the Eastern and 70% in the Western Laptev Sea. Conductivity-temperature-depth (CTD) measurements and observations of currents carried out in April-May 1999 allowed us to investigate the surface circulation along the margins of the Laptev Sea flaw polynya. The convective nature of the surface currents, with velocities measured as high as 62 cm/s, is discussed. Currents are most likely part of circulation cells, which arise as a result of brine rejection due to intensive ice formation in the polynya. It is shown that the spatial alignment of sea ice crystals in the marginal part of the polynya is most likely a consequence of the quasi-stationary cellular circulation

Description: Geochemical and rock magnetic investigations of sediments from three sites on the continental margin off Argentina and Uruguay were carried out to study diagenetic alteration of iron minerals driven by anaerobic oxidation of methane (AOM). The western Argentine Basin represents a suitable sedimentary environment to study nonsteady-state processes because it is characterized by highly dynamic depositional conditions. Mineralogic and bulk solid phase data document that the sediment mainly consists of terrigenous material with high contents of iron minerals. As a typical feature of these deposits, distinct minima in magnetic susceptibility (κ) are observed. Pore water data reveal that these minima in susceptibility coincide with the current depth of the sulfate/methane transition (SMT) where HS− is generated by the process of AOM. The released HS− reacts with the abundant iron (oxyhydr)oxides resulting in the precipitation of iron sulfides accompanied by a nearly complete loss of magnetic susceptibility. Modeling of geochemical data suggest that the magnetic record in this area is highly influenced by a drastic change in mean sedimentation rate (SR) which occurred during the Pleistocene/Holocene transition. We assume that the strong decrease in mean SR encountered during this glacial/interglacial transition induced a fixation of the SMT at a specific depth. The stagnation has obviously enhanced diagenetic dissolution of iron (oxyhydr)oxides within a distinct sediment interval. This assumption was further substantiated by numerical modeling in which the mean SR was decreased from 100 cm kyr−1 during glacial times to 5 cm kyr−1 in the Holocene and the methane flux from below was fixed to a constant value. To obtain the observed geochemical and magnetic patterns, the SMT must remain at a fixed position for ∼9000 yrs. This calculated value closely correlates to the timing of the Pleistocene/Holocene transition. The results of the model show additionally that a constant high mean SR would cause a concave-up profile of pore water sulfate under steady state conditions.

Description: Caldera volcanoes form due to collapse of a magma chamber roof into the underlying magma chamber. Many field, theoretical and experimental studies have postulated that calderas are delimited by reverse ring faults and are surrounded by peripheral concentric normal faults. In the simplest theoretical scenario, circular magma chambers produce circular calderas. Many calderas, however, are elliptical in shape, particularly those in extensional and compressive tectonic settings. Several factors may explain elliptical calderas. The first is the presence of an elliptical magma chamber, established by, for instance, preferential intrusion along pre-existing basement structures or differential spalling of the magma chamber walls. The second is the overlap (nesting) of several discrete calderas to form a single, larger elliptical structure. The third is asymmetric subsidence. The fourth is variable pre-collapse topography. A fifth possible factor is distortion of the caldera faults by the regional stress field during caldera formation. A sixth factor is the post-collapse distortion of the caldera structure due to continued regional deformation. To better understand relationships between caldera surface expression, reservoir geometry and regional tectonic stresses, we conducted scaled analogue experiments. These experiments examined the impact of regional stress and associated structures on calderas formed during evacuation of reservoirs (circular rubber balloons) of known dimensions and depths. The results show that, in principle, calderas produced in compression/extension experiments are elongated parallel to the direction of minimum horizontal compressive stress, despite the chamber beneath being circular in plan view. As a consequence, model ring fault orientation varied from steeply dipping where striking perpendicular to the minimum horizontal regional compressive stress, to shallower dips where striking parallel to the minimum horizontal regional compressive stress. This leads us to suggest that the influence of a regional stress field on caldera fault orientation during and/or after caldera formation may be significant in the development of elliptical calderas. In addition, such variation of caldera ring fault dip from steep to relatively shallow could influence location and behaviour of ring fissure eruptions.

Description: The greater Agulhas Current system has several components with high mesoscale turbulence. The phytoplankton distribution in the southwest Indian Ocean reflects this activity. We have used a regional eddy-permitting, coupled physical–biological model to study the physical–biological interactions and to address the main processes responsible for phytoplankton distribution in three different biogeochemical provinces: the southwest Subtropical Indian Gyre (SWSIG), the subtropical convergence zone (SCZ) and the subantarctic waters (SAW) south of South Africa. The biological model with four compartments (Nitrate–Phytoplankton–Zooplankton–Detritus) adequately reproduces the observed field of chlorophyll a. The phase of the strong modelled seasonality in the SWSIG is opposite to that of the SCZ that forms the southern boundary of the subtropical gyre. Phytoplankton concentrations are governed by the source-minus-sink terms, which are one order of magnitude greater than the dynamical diffusion and advection terms. North of 35°S, in the SWSIG, phytoplankton growth is limited by nutrients supply throughout the year. However, deeper stratification, enhanced cross-frontal transport and higher detritus remineralization explain the simulated higher concentrations of phytoplankton found in winter in the SWSIG. The region between 35° and 40°S constitutes a transition zone between the SCZ and the oligotrophic subtropical province. Horizontal advection is the main process bringing nutrients for phytoplankton growth. The front at 34°S represents a dynamical barrier to an extension further to the north of this advection of nutrients. Within the SCZ, primary production is high during spring and summer. This high productivity depletes the nutrient standing stock built up during winter time. In winter, nutrients supply in the convergence zone is indeed large, but the deep mixing removes phytoplankton from the euphotic zone and inhibits photosynthesis, yielding lower surface chlorophyll a concentrations. Waters south of the Subantarctic Front have a summer biomass close to that of frontal waters and higher than for subtropical waters. However, these simulated concentrations are slightly higher than the observed ones suggesting that limitation by iron and/or silica may play a role

Description: Large sums are spent annually collecting and, increasingly, electronically encoding field data, making them widely accessible. Earlier data were recorded on paper, and archived at a few institutions, which eventually discard them. Data recovery and distribution is a valuable contribution to science, as it counters the ‘shifting baseline’ syndrome and ensures long-term returns on funds society invested in data gathering. Data recovery need not be expensive. We present the data recovery from the Guinean Trawling Survey, conducted in the early 1960s off West Africa, which cost 0.2% of initial survey costs. Research and graduate training institutions, as well as funding agencies should make digital data globally available as part of their deliverables.

Description: Thermodynamic equations of stability and solubility of methane hydrate were developed using the method of Pitzer [Pitzer, K.S. (1991). Ionic interaction approach: Theory and data correlation. In: K.S. Pitzer (Editor), 2nd Edition, Activity Coefficients in Electrolyte Solutions. CRC Press, Roca Raton Ann Arbor Boston London, pp. 75–153.]. Dissociation pressures are calculated for different temperature and salinity conditions ranging from 273 to 293 K and 0–70 (salinity). The solubility of methane and methane hydrate in seawater is calculated for the same temperature and salinity ranges and for hydrostatic pressures (Pdis) up to 50 MPa. Since the composition of major pore water ions may change due to a variety of geochemical processes (i.e. anaerobic oxidation of organic matter or/and methane) affecting the activity of water, additional stability and solubility calculations are presented by substituting the equivalent amount of sulfate by hydrogen carbonate ions. Based on this rigorous thermodynamic analysis, the calculation of dissociation pressures has been approximated by empirical algorithms that are functions of temperature and salinity (chlorinity for pore water). Similar algorithms are presented for the calculation of methane concentrations in seawater and pore water equilibrated with methane hydrate as functions of salinity (chlorinity for pore water), temperature and hydrostatic pressure. In contrast to earlier approaches, the provided methods allow the calculation of these properties by easily applicable functions considering a continuous variation of the control parameters over a wide range of conditions that are met in the deep marine environment.

Description: The 1998 block-and-ash flow (BAF) deposits on the western flanks of Merapi were described both immediately following emplacement, and after one and two wet seasons of erosion. This afforded a unique combination of data on deposit morphology and internal structure from proximal to distal reaches. The deposits of the basal avalanches from individual BAF events were classified into three major and two minor facies in channelised reaches, primarily resulting from effects of channel confinement and slope. Termination reaches were classified into three facies, related to preevent topography. The deposit facies architecture was interpreted to understand particle transport and deposition within the framework of granular flow systematics. The transport model we propose for these basal avalanches involves unsteady flow conditions, generated by pulses of collapse as the source, and/or by development of kinetic waves during the granular flow. The coarsest clasts along with low-density material migrated to the wave/pulse fronts within these flows. Whereas, in bulk flow, grain dispersive pressures and kinetic sieving result in coarsest clasts being buoyed to the flow top, with this tendency being greatest on higher slopes (=greater kinetic energy) and with greater flow confinement (maximising particle collisions). Deposition begins as the flow reaches near its full extent. An initial pulse or flow wave freezes rapidly from its base upward and its rear forward as it looses kinetic energy and dispersive pressure, such that an upper higher energy part of the flow is still able to move downstream over the frozen base. Later waves or pulses then accrete progressively horizontally upslope banking up onto or overtopping earlier deposited sediment. Hence, the overall flow freezes from its front to its tail. At termination reaches in unconfined areas, the overflowing upper part of flow gradually deposits from its base upward, resulting in a slightly tapering sheet formed deposit, marked by a front made up of wood fragments and large boulders. On sudden slope breaks in termination areas, piling up of sediment occurs in flat reaches, producing whaleback type forms as the flows rapidly lost competence. One implication of this model is that each kinetic wave or flow-pulse crest developed within the basal avalanche represents a portion of greater flow depth (or stage height). Hence, development of these crests control the ability of parts of the basal avalanche to escape from confined channels and generate unexpected hazards.

Description: Several shipboard sections acquired in the western equatorial Atlantic along 35∘W35∘W allow for the first time to analyze the annual cycle of the density and velocity field in the upper 2000 m within this region. The amplitude of the annual harmonic of the velocity field shows several distinct maxima at the equator. Strong amplitudes up to View the MathML source15cms-1 are found in the depth range of the equatorial intermediate current (EIC) between 400 and 1000 m depth that are slightly shifted northward with respect to the equator. The meridional structure of the annual harmonics as well as upward phase propagation is consistent with downward propagating odd meridional mode Rossby waves. The observations are compared with a regional numerical model with very high vertical resolution. Good agreement is found between the simulated and observed structure and the amplitude of the annual harmonics. The model results suggest the presence of equatorial beams composed of wind-generated Kelvin and Rossby beams (causing seasonality in the near surface layer) as well as Rossby beams generated by the reflection of Kelvin beams at the eastern boundary (causing seasonality in the depth range of the EIC at the 35∘W35∘W section). The annual cycle of the sea surface height (SSH) observed by TOPEX/Poseidon altimetry indicates an east–west seesaw pattern that corresponds to the fast response (about 30 days lag) of the zonal SSH gradient to the annual cycle of the zonal wind field at the equator due to the propagation of lowest baroclinic mode equatorial waves. The increase of the easterly winds in the western equatorial Atlantic associated with El Nino in the beginning of 1997 led almost instantaneously to an adjustment of the zonal SSH gradient with elevated (depressed) SSH in the western (eastern) basin. In contrast, the velocity field at intermediate depths lags the zonal wind forcing by several months up to a year as the model simulation reveals.

Description: Temporal and spatial variations in the species composition of modern and Holocene assemblages of molluscs, ostracods, and foraminifers from the Laptev Sea shelf (Arctic Siberia) have been investigated to reconstruct palaeoenvironmental changes during the last postglacial times and associated sea-level rise. Analysis of coretop sediment samples allowed to distinguish four modern assemblages. The specific habitat preferences of these species groups, such as water depth and salinity, were then used to interpret past environmental changes on the basis of two radiocarbon-dated sediment cores from the eastern middle shelf region, i.e., obtained from the Yana (51 m water depth) and Lena (45 m water depth) palaeovalleys. Despite the water depth difference of the two core sites, all downcore data document uniform fossil evidence for a gradual transformation of the Laptev Sea shelf from a terrestrial to a marine environment due to the southward transgressing sea. Three major phases have been recognized. These reflect: (1) a nearshore brackish-water environment of the initial stage of inundation (11.3–11.1 in the Yana and 11.2–10.8 cal. ka in the Lena palaeovalley); (2) a shallow inner-shelf, fluvially affected environment (11.1–10.3 and 10.8–8.2 cal. ka); (3) a modern-like marine environment which eventually became established since 10.8 and 8.2 cal. ka, depending on the specific water depth of each core site.

Description: Ferromanganese crusts provide records of long term change in ocean circulation and continental weathering. However, calibrating their age prior to 10 Ma has been entirely based on empirical growth rate models using Co concentrations, which have inherently large uncertainties and fail to detect hiatuses and erosional events. We present a new method for dating these crusts by measuring their osmium (Os) isotope record and matching it to the well-known marine Os isotope evolution of the past 80 Ma. The well-characterised crust CD29-2 from the central Pacific, was believed to define a record of paleooceanographic change from 50 Ma. Previous growth rate estimates based on the Co method are consistent with the new Os isotope stratigraphy but the dating was grossly inaccurate due to long hiatuses that are now detectable. The new chronology shows that it in fact started growing prior to 70 Ma in the late Cretaceous and stopped growing or was eroded between 13.5 and 47 Ma. With this new technique it is now possible to exploit the full potential of the oceanographic and climatic records stored in Fe–Mn crusts.

Description: This paper establishes the predictability of a one-dimensional virtual plankton ecosystem created by Lagrangian Ensemble integration of an individual-based model. It is based on numerical experiments for a scenario, in which the surface fluxes have stationary annual cycles, and the annual surface heat budget is in balance, i.e. solar heating equals cooling to the atmosphere. Under these conditions, the virtual ecosystem also followed a stationary annual cycle. We investigate the stability of this ecosystem by studying the statistics of multi-year simulations of the ecosystem in a virtual mesocosm moored off the Azores. The integrations were initialised by a first guess at the state of the ecosystem at the end of the cooling season, when the mixed layer was approaching the annual maximum depth. The virtual ecosystem quickly adjusted to a stable attractor, in which the inter-annual variation was only a few percent of the multi-year mean. This inter-annual variation was due to random displacement of individual plankters by turbulence in the mixed layer. The inter-annual variance is nearly, but not exactly ergodic; the deviation is due to inheritance of zooplankton weight through lineages. The virtual ecosystem is independent of initial conditions: that is the proof of stability. The legacy of initialisation error decays within three years. The form of the attractor depends on three factors: the specification of the ecosystem model, the resource level (nutrients), and the annual cycle of external forcing. Sensitivity studies spanning the full range of model parameters and resource levels demonstrate that the virtual ecosystem is globally stable. In extreme cases the zooplankton becomes extinct during the simulation; the attractor adjusts gracefully to this new regime, without the emergence of vacillation or a strange attractor that would signal instability. At high resource levels, some of the zooplankton produce two generations per year (as was observed by Marshall and Orr [Marshall, S. M., and Orr, A. P. (1955). The biology of a marine copepod. Edinburgh: Oliver and Boyd. 188 pp.]; again the attractor adjusts gracefully to the new regime. Ocean circulation does not disrupt the stability of the virtual ecosystem. This is demonstrated by a numerical experiment in which the virtual ecosystem drifts with the mean circulation on a five-year cycle, following a track in the Sargasso Sea that penetrates deep into the zones of annual heating and cooling. The legacy of initialisation error decays within three cycles of the external forcing. Thereafter the ecosystem lies on a five-year geographically/lagrangian attractor. The stability of virtual ecosystems offers useful predictability with a good sign-to-noise ratio. (c) 2005 Elsevier Ltd. All rights reserved.

Description: A model simulation of the climate during Maunder Minimum (MM) (1645–1715) was performed using the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM). A multi-year equilibrium integration with prescribed solar insolation, atmospheric composition and sea surface temperatures (SSTs) for MM conditions was compared with a present-day (PD) simulation. We find that during MM the stratosphere was significantly warmer (up to 3 K) than during PD, and dynamically more disturbed in winter. The warming is due to the dominant effect of the lower atmospheric CO2 concentration during MM, which leads to a reduced emission of long-wave radiation, and compensates the cooling due to the reduced solar irradiance. The troposphere was about 1–1.5 K cooler in the annual mean during MM. The global mean surface air temperature decreased by 0.86 K. Northern hemisphere winters were on average characterized by cooler and drier weather over the northern parts of the continents, with an increase in precipitation in the southern parts. These climate anomalies are shown to be related to a shift in the North Atlantic Oscillation (NAO) towards a predominantly low phase during MM. The simulated climate anomalies are in very good agreement with reconstructions from proxy-data. Changes in the dynamical coupling between the troposphere and stratosphere were found in the MM simulation, indicating the importance of the stratosphere for climate change.

Description: We investigated the influence of the composition of the vertical particle flux on the removal of particle reactive natural radionuclides (Th-230 and Pa-231) from the water column to the sediments. Radionuclide concentrations determined in sediment traps moored in the western, central and eastern Arabian Sea were related to the major components (carbonate, particulate organic matter (POC), opal, lithogenic material) of the particle flux. These data were combined with sediment trap data previously published from the Southern Ocean, Equatorial Pacific and North Atlantic [Z. Chase, R.F. Anderson, M.Q. Fleisher, P.W. Kubik, The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean, Earth Planet. Sci. Lett. 204 (2002) 215-229; J.C. Scholten, F. Fietzke, S. Vogler, M. Rutgers van der Loeff, A. Mangini, W Koeve, J. Waniek. P. Stoffers, A. Antia, J. Kass, Trapping efficiencies of sediment traps from the deep eastern North Atlantic: The Th-230 calibration, Deep Sea Research 1148 (2001) 2383-2408]. The correlations observed between the particle-dissolved distribution coefficients (K-d) of Th-230 and Pa-231 and the concentrations of the particle types depend on the sediment trap data set used. This result suggests that scavenging affinities of the nuclides differ between oceanic regions. Several factors (K-d values, reactive surface areas of particles, inter-correlations in closed data set) can, however, influence the observed relationships and thus hamper the interpretation of these correlation coefficients as a measure of relative scavenging affinities of the nuclides to the particle types investigated. The mean fractionation factor (F(Pa/Th)=K-d(Pa)/(K)d(Th)) from the Equatorial Pacific (F=0.11+/-0.03) is similar to that from the North Atlantic (F(Pa/Th)=0.077+/-0.026), and both are lower than the factors from the Arabian Sea (F(Pa/Th)=0.35+/-0.12) and from the Southern Ocean (F(Pa/Th) 0.87+/-0.4). For opal concentrations exceeding similar to60%, an increase in the fractionation factors is observed causing a higher mean fractionation factor for the Southern Ocean trap data set. For the other areas investigated, differences in the mean fractionation factors cannot be related to the particles types considered. In the Arabian Sea, seasonally variable Pa-231(ex)/Th-230(ex) ratios observed in the sediment traps as well as differences of the ratios between recently deposited phytodetritus (fluff) and normal surface sediments indicate seasonal changes in scavenging processes which the generally accepted reversible scavenging models do not envisage. We assume that variable sinking rates of particles, and/or particles not considered in this study (e.g. colloids, manganese oxides, transparent exopolymer particles) may play an important but as yet unexplored role in deep-water scavenging processes. (C) 2004 Elsevier B.V. All rights reserved.

Description: In the western equatorial Pacific the low-salinity core of Antarctic Intermediate Water (AAIW) is found at about 800 m depth between potential density levels σθ = 27.2 and 27.3. The pathways of AAIW and the degradation of its core are studied, from the Bismarck Sea to the Caroline Basins and into the zonal equatorial current system. Both historical and new observational data, and results from numerical circulation model runs are used. The observations include hydrographic stations from German and Japanese research vessels, and Eulerian and Lagrangian current measurements. The model is the JAMSTEC high-resolution numerical model based on the Modular Ocean Model (MOM 2). The general agreement between results from the observations and from the model enables us to diagnose properties and to provide new information on the AAIW. The analysis confirms the paramount influence of topography on the spreading of the AAIW tongue north of New Guinea. Two cores of AAIW are found in the eastern Bismarck Sea. One core originates from Vitiaz Strait and one from St. George’s Channel, probably arriving on a cyclonic pathway. They merge in the western Bismarck Sea without much change in their total salt content, and the uniform core then increases considerably in salt content when subjected to mixing in the Caroline Basins. Hydrographic and moored current observations as well as model results show a distinct annual signal in salinity and velocity in the AAIW core off New Guinea. It appears to be related to the monsoonal change that is typically found in the near-surface waters in the region. Lagrangian data are used to investigate the structure of the deep New Guinea Coastal Undercurrent, the related cross-equatorial flow and eddy-structure, and the embedment in the zonal equatorial current system. Results from 17 neutrally buoyant RAFOS floats, ballasted to drift in the AAIW core layer, are compared with a numerical tracking experiment. In the model 73 particles are released at five-day intervals from Station J (2.5°N, 142°E), simulating currents at a moored time series station north of New Guinea. Observed and model track patterns are fairly consistent in space and season. Floats cross the equator preferably north of Cenderawasih Bay, with a maximum range in eddy-motion in this region north of New Guinea. The northward route at 135°E is also reflected in a low-salinity tongue reaching up to 3°N. At that longitude the floats seem to ignore the zonally aligned equatorial undercurrents. Farther to the east (139 145°E), however, the float observations are consistent with low-latitude bands of intermediate currents.

Description: The dense overflow across the Denmark Strait is investigated with hydrographic and hydro-chemical data and the water mass composition of the Denmark Strait Overflow Water (DSOW) is determined by multivariate analysis. Hydrographical properties, the transient tracers CFC-11 and CFC-12, oxygen and nutrients are utilized for the water mass definitions. Distribution and characteristics of water masses north of Denmark Strait are described, the important water masses at the sill and the variability on weekly time-scales are discussed, and the entrainment and mixing of water into the overflow plume in the northern Irminger Basin is calculated. The analysis indicates that water masses both from the Nordic Seas and the Arctic Ocean are important for the formation of DSOW. It is found that water masses transported with the East Greenland Current make up about 75% of the overflow at the sill. The overflow at, and shortly south of, the sill is inhomogeneous with a low-salinity component dominated by Polar Intermediate Water. The high-salinity component of the overflow is mainly of Arctic origin. The water mass composition, and the short-term variability for 7 repeats of sections close to the sill are described, and these illustrate that the overflow is in fact a composite of a number of water masses with different formation and transport histories. This indicate that the overflow is a robust feature, but that it responds to variations in the circulation or atmospheric forcing that influences the formation of intermediate and deep water masses within the Arctic Mediterranean and the North Atlantic. At a section about 400 km south of the sill the overflow is well mixed and modified by entrainment of, mainly, Iceland–Scotland Overflow Water and Labrador Sea Water, together constituting 30% of the overflow plume. The entrainment of Middle Irminger Water dominates shortly downstream of the sill, before the overflow plume reaches too deep but the entrainment seems to be intermittent in time.

Description: The concept of compositional bimodality in carbonatites has become widely accepted and has been used to impose restrictions on the composition of carbonatite magmas. We agree that mineralogical bimodality exists in carbonatites (most are either calcitic or dolomitic/ankeritic), but we argue that there is no compositional bimodality. The idea of bimodality is based on the interpretation of a variety of element distribution diagrams which were compiled only from chemical analyses in which SiO2 is 〈 10 wt.%. All others were rejected. Even with such a restricted data set the case for compositional bimodality is extremely weak, but the inclusion of analyses with higher SiO2 content destroys it completely. Yet these more siliceous compositions must be included, for many carbonatites contain substantial amounts of Fe–Mg silicates which are an essential part of the magmatic mineralogy of the rocks. They account for much of the Mg in carbonatites that are otherwise calcitic. Many such carbonatites contain well in excess of 10 wt.% SiO2. Supporters of the bimodality concept argue that liquids having compositions between calcite and dolomite can precipitate neither calcite nor dolomite because the minimum on the solid solution loops in the system calcite–dolomite permits only a carbonate of intermediate composition. Therefore, it is argued, liquids of such intermediate composition cannot be parental to calcitic and dolomitic carbonatites; their parent magmas must be calcitic and dolomitic. This deduction is incorrect. It is well established that dolomitic liquids have calcite as the liquidus phase over substantial temperature intervals, and that this is followed by dolomite precipitation. Mixed calcite–dolomite carbonatites are explicable in this way. Therefore, dolomitic liquids can be parental to calcitic carbonatites. However, dolomitic carbonatites cannot crystallize from a calcitic liquid. We suggest that intermediate composition carbonatite magmas are probably common. Bimodality in carbonatites is solely mineralogical, not compositional.

Description: Nitrogen fixation is one of the important biochemical pathways that play a role in controlling the oceanic nitrogen inventory. Here we review nitrogen fixation in the ocean, with a particular emphasis on Trichodesmium, one of the dominant marine diazotrophs. Distribution data for diazotrophs are scarce, except in specific regions where Trichodesmium is known to bloom. Although some regions are clearly under-sampled, Trichodesmium can generally be found in tropical regions where temperature is at least 20 °C, except in the North Atlantic, where drift to higher latitudes is possible via the Gulf Stream. Likewise, biomass estimates are problematic because of the colony-forming habit of this organism. Trichodesmium grows slowly with reported maximum growth rates of approximately 0.14 d-1. Studies of the photosynthetic physiology indicate that Trichodesmium can tolerate high light intensity with Ik and Ic values of ∼300 and ∼140 μmole photons m−2 s−1, respectively. Review of the elemental composition of Trichodesmium indicates that the C:N molar ratio of 6.3:1 does not depart significantly from the predicted Redfield stoichiometry of 6.6:1. Overall, measured N:P ratios from the field and the laboratory were around 50, a significant departure from the Redfield stoichiometry of 16:1. Whether this indicates phosphorus limitation is not clear at present. The iron requirements of diazotrophs in general and of Trichodesmium in particular have been the subject of debate, but some recent laboratory studies have converged on Fe:C (μmole:mole) of approximately 50 at 70% of the maximum growth rates (μmax) to 250 at μmax for this species. There is a noticeable lack of information on growth rate as a function of phosphorus and fixed nitrogen sources. Although Trichodesmium is a non-heterocystous cyanobacterium, carbon and nitrogen fixation co-occur during the light period, indicating that light energy is required for both of these processes. This is likely to be achieved through cellular differentiation of the trichomes and a tight control of the temporal expression of many biochemical pathways. A summary table presents a set of values for the initial parameterisation of parameters relevant to the incorporation of nitrogen fixation in biological and biogeochemical models.

Description: We measured oxygen isotope compositions of 34 adakites, high-Mg andesites, and lavas suspected to contain abundant slab and sediment melts from the Western and Central Aleutians, the Andes, Panama, Fiji, Kamchatka, Setouchi (Japan), and the Cascades. This suite covers much of the diversity of arc lavas previously hypothesized to contain abundant ‘slab’ melts. Measured and calculated values of δ18O for olivine phenocrysts in these samples vary between 4.88‰ and 6.78‰, corresponding to calculated melt values of 6.36‰ to 8.17‰. Values of δ18O for these samples are correlated with other geochemical parameters having petrogenetic significance, including Sr/Y, La/Yb, 87Sr/86Sr, and 143Nd/144Nd. Archetypical adakites from Adak Island (Central Aleutian) and Cook Island (Andean Austral zone), previously interpreted to be nearly pure melts of basaltic and gabbroic rocks in subducting slabs, have values of δ18O slightly higher than those of normal mid-ocean-ridge basalts, and in oxygen isotope equilibrium with typical mantle peridotite (i.e., their subtle 18O enrichment reflects their Si-rich compositions and low liquidus temperatures, not 18O-rich sources). Other primitive adakites from Panama and Fiji show only subtle sub-per mil enrichments in the source. This finding appears to rule out the hypothesis that end-member adakites are unmodified partial melts of basaltic rocks and/or sediments in the top (upper 1–2 km) of the subducted slab, which typically have δ18O values of ca. 9–20‰, and also appears to rule out them being partial melts of hydrothermally altered gabbros from the slab interior, which typically have δ18O values of ca. 2–5‰. One explanation of this result is that adakites are mixtures of partial melts from several different parts of the slab, so that higher- and lower-δ18O components average out to have no net difference from average mantle. Alternatively, adakites might be initially generated with more extreme δ18O values, but undergo isotopic exchange with the mantle wedge before eruption. Finally, adakites might not be slab melts at all, and instead come from differentation and/or partial melting processes near the base of the arc crust in the over-riding plate. High-Mg andesites and Setouchi lavas are commonly higher in δ18O than equilibrium with the mantle, consistent with their containing variable amounts of partial melts of subducted sediments (as we conclude for Setouchi lavas), slab-derived aqueous fluid (as we conclude for the Cascades) and/or crustal contaminants from the over-riding plate (as we conclude for Kamchatka).

Description: The spreading of recently ventilated North Atlantic Deep Water (NADW) from the formation region to the equatorial Atlantic occurs mainly in the Deep Western Boundary Current (DWBC). When crossing the equator between 44°W and 35°W, the DWBC is split in two velocity cores through a chain of seamounts around the Atoll das Rocas at 3.5°S. Further eastward the DWBC contributes to the zonally oriented equatorial current system. The circulation of the NADW in the crucial region around the eastern tip of Brazil is examined using 8 CTD and Chlorofluorocarbon (CFC) sections along 35°W and along 5°S, respectively, taken mainly in spring and fall in the years 1990–2002. As expected from the short direct flow path between the two sections, the CFC concentrations in the upper NADW (1400–2200 m) were similar at 35°W and 5°S during boreal autumn. In spring, however, a significant downstream CFC decrease was observed. If one attributes the decrease solely to the older age of water further downstream, the CFC concentration age difference between 35°W and 5°S in May 2002 would be 3–5 years. We interpret the aging to be caused by an eastward detour of the flow with the deep equatorial circulation before reaching 5°S in spring. Another conspicuous anomaly was found in the middle NADW (2200–3400 m) with downstream decreasing salinities in boreal spring, but not in autumn. This variability might also be caused by differences in the deep equatorial circulation, but in contrast to the uNADW, one cannot exclude enhanced mixing with water of South Atlantic origin in spring to be the cause of that variability. No seasonal difference was observed in the hydrography or the CFC concentrations for the lower NADW. The weaker CFC decrease along the equator compared with that in the DWBC downstream of 35°W, and the topographic features along the downstream path, point to a predominantly eastward flow of the deep lNADW core. The lNADW CFC core is no longer observed at 11°S. Repeated observations of CFCs in the DWBC highlight the diverse variability affecting the components of NADW.

Description: High resolution oxygen isotope profiles of aragonitic bivalve shells (Astarte borealis) collected alive in different years are used to trace hydrographical changes on the Laptev Sea shelf, which are mainly forced by changes in riverine freshwater discharge and arctic atmospheric circulation patterns. By merging individual isotope profiles, a high resolution time series of relative changes in bivalve δ18O is obtained for the eastern Laptev Sea for the period 1969 to 1998. The resulting pattern in the δ18O time series reflects seasonal bottom-water salinity changes in the Laptev Sea, which is dominated by the peak input of freshwater discharged by the Lena River onto the Laptev Sea shelf during summer. The relative changes in summer bottom-water salinity, deduced from the δ18O values in the bivalves and the discharge anomaly of the Lena River, show a significant negative correlation. It is therefore suggested that the annual and subdecadal variations of the riverine freshwater and its influence on the shelf hydrography are imprinted in the bivalve shells. Moreover, we note that extreme summer precipitation anomalies in the Lena River catchment area affect the river discharge characteristics, events which are detectable in the δ18O time series. This all implies that δ18O records of bivalve shells have the potential to build long-term records of atmospheric-forced changes in arctic circulation.

Description: Twenty years of time series observations from the deep-sea mooring KIEL276 are used to obtain information on the frequency and propagation of meddies (Mediterranean Water eddies), on long-term changes in flow properties, and on a possible relation to the North Atlantic Oscillation. The mooring was set at the nominal position 33°N, 22°W at a water depth of more than 5200 m in the northern Canary Basin. It is located near the southern boundary of the Azores Current (AC), which is part of the North Atlantic subtropical gyre, and also in the large-scale Mediterranean Water (MW) tongue originating from the Strait of Gibraltar. The amplitudes of time-varying vertical quasi-geostrophic modes and the correlation of current and temperature changes at levels in the MW and the North Atlantic Central Water above are used to identify meddies. A total of 10 meddies passed the mooring during the period 1980–2000. Half of the events can be related to earlier observations. Directional changes in meddy-related velocities are used to estimate speeds and directions of meddy propagation. Directions of propagation are very homogeneous, with all the 10 meddies observed propagating with a southward velocity component within a sector of 90°, and typical speeds are 2–3 cm/s. Meddy occurrence was uneven in time, with six meddies found during the first four years and only four meddies during the remaining 16 years. Decadal changes show the annual-mean and the fluctuating kinetic energy levels at the site changing from lower values in the 1980s to high values in the 1990s. This change appears to be correlated with variations in the North Atlantic Oscillation (NAO) index, with a delay in oceanic response of about 3 years. A conceptual model of AC meanders is used to identify meander signals in the upper-layer time series. The AC axis appears to be closer to the site during the 1990s than during the preceding decade and indicates a southward or southwestward displacement of the AC with increasingly positive values of the NAO index. Meddy frequency is lower when the AC gets closer from the north. A reduction in meddy occurrence in the region just south of the AC is possibly caused by the shear-induced blocking of some meddies crossing the front from the north.

Description: Picophytoplankton are a small or major component of the phytoplankton community and present in all oceanic systems, from pole to pole. They dominate in the low chlorophyll biomass areas, such as the (sub)tropical regions, but also contribute considerably (up to 20%) in the high chlorophyll biomass areas. The ecosystems of occurrence contrast significantly in physical and chemical settings. This includes a strongly mixed upper water column replete in nutrients as well as a strongly thermally stratified euphotic zone depleted in nutrients at the surface with a steep inverse light and nutrient gradient. These changes impose a strong impact on the composition of the picophytoplankton community but also on the biochemical and physiological properties of the species present. In particular, the pigmentation and cellular carbon, nitrogen and phosphorus quota and requirement will differ from a stratified compared to a well-mixed water column. As a result no characteristic values for the parameters required for this specific algal group in a global phytoplankton carbon model (the SWAMCO model,Lancelot et al. (2000), Deep-Sea Res. I, 47, 1621) can be given. In the present paper an inventory is made of the biochemical, physiological and photosynthetic parameters of two species of cyanobacteria (Prochlorococcus and Synechococcus) and the pico-size class fraction of the eukaryote phytoplankton component. Other groups of phytoplankton, such as diatoms, Trichodesmium, Phaeocystis and coccolithophorids, will be discussed in separate papers in this issue. This inventory is a mixture of laboratory experiments using well-defined algal populations as well as data derived from field surveys including a mixture of species. Where possible, the relevance of the parameters will be discussed in relation to the nature of the physico-chemical conditions of the area of occurrence.

Description: Cathodic stripping voltammetry (CSV) is an analytical technique used for the analysis of low levels of analytes (principally trace metals and sulfur containing organic compounds) in aqueous solutions, and is based on the measurement of a reductive current response as a function of a potential scan towards more negative potentials. The technique is highly sensitive (limits of detection of 10− 10–10− 12 mol l− 1) because of the application of a preconcentrations step prior to the stripping step. During the preconcentration the analyte is collected on the surface of the working electrode (typically a mercury drop), often in the presence of an added electro-active ligand. The CSV technique has been used for automated measurements of trace metals in marine waters, but a key strength of CSV is in its use in trace metal speciation measurements in natural waters, in particular dissolved iron in marine waters.

Description: Two new cycloartane-type glycosides oleifoliosides A (1) and B (2) were isolated from the lower stem parts of Astragalus oleifolius. Their structures were identified as 3-O-[β-xylopyranosyl-(1 → 2)-α-arabinopyranosyl]-6-O–β-xylopyranosyl-3β,6α,16β,24(S),25-pentahydroxycycloartane and 3-O-[β-xylopyranosyl-(1 → 2)-α-arabinopyranosyl]-6-O–β-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxycycloartane, respectively, by means of spectroscopic methods (IR, 1D and 2D NMR, ESI-MS). Three known cycloartane glycosides cyclocanthoside E (3), astragaloside II (4) and astragaloside IV (5) were also isolated and characterized. All five compounds were evaluated for in vitro trypanocidal, leishmanicidal and antiplasmodial activities as well as their cytotoxic potential on primary mammalian (L6) cells. Except for the compound 5, all compounds showed notable growth inhibitory activity against Leishmania donovani with IC50 values ranging from 13.2 to 21.3 μg/ml. Only weak activity against Trypanosoma brucei rhodesiense was observed with the known compounds astragaloside II (4, IC50 66.6 μg/ml) and cyclocanthoside E (3, IC50 85.2 μg/ml), while all compounds were inactive against Trypanosoma cruzi and Plasmodium falciparum. None of the compounds were toxic to mammalian cells (IC50’s 〉 90 μg/ml). This is the first report of leishmanicidal and trypanocidal activity of cycloartane-type triterpene glycosides.

Description: The ethanolic root extract of Scrophularia lepidota, an endemic plant of the Turkish flora, has been investigated for its anti-protozoal and inhibitory effect towards plasmodial enoyl-ACP reductase (FabI), a key enzyme of fatty acid biosynthesis in Plasmodium falciparum. Chromatographic separation of the extract yielded 10 iridoids (1–10), two of which are new, and a known phenylethanoid glycoside (11). The structures of the new compounds were determined as 3,4-dihydro-methylcatalpol (8) and 6-O-[4″-O-trans-(3,4-dimethoxycinnamoyl)-α-l-rhamnopyranosyl]aucubin (scrolepidoside, 9) by spectroscopic means. The remaining metabolites were characterized as catalpol (1), 6-O-methylcatalpol (2), aucubin (3), 6-O-α-l-rhamnopyranosyl-aucubin (sinuatol, 4), 6-O-β-d-xylopyranosylaucubin (5), ajugol (6), ajugoside (7), an iridoid-related aglycone (10) and angoroside C (11). Nine isolates were active against Leishmania donovani, with the new compound 9 being most potent (IC50 6.1 μg/ml). Except for 4, all pure compounds revealed some trypanocidal potential against Trypanosoma brucei rhodesiense (IC50 values 29.3–73.0 μg/ml). Only compound 10 showed moderate anti-plasmodial (IC50 40.6 μg/ml) and FabI enzyme inhibitory activity (IC50 100 μg/ml). 10 is the second natural product inhibiting the fatty acid biosynthesis of Plasmodium falciparum.

Description: A high-resolution record of sea-level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt-marsh peat sequence at Chezzetcook, Nova Scotia, Canada. Former mean tide level positions are reconstructed with a precision of ±0.055 m using a transfer function derived from distributions of modern salt-marsh foraminifera. Our age model for the core section older than 300 years is based on 19 AMS 14C ages and takes into account the individual probability distributions of calibrated radiocarbon ages. The past 300 years is dated by pollen and the isotopes 206Pb, 207Pb, 210Pb, 137Cs and 241Am. Between AD 1000 and AD 1800, relative sea level rose at a mean rate of 17 cm per century. Apparent pre-industrial rises of sea level dated at AD 1500-1550 and AD 1700-1800 cannot be clearly distinguished when radiocarbon age errors are taken into account. Furthermore, they may be an artefact of fluctuations in atmospheric 14C production. In the 19th century sea level rose at a mean rate of 1.6 mm/yr. Between AD 1900 and AD 1920, sea-level rise accelerated to the modern mean rate of 3.2 mm/yr. This acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming. © 2005 Elsevier Ltd. All rights reserved.

Description: The compressional wave velocities (Vp), pressure derivatives (Vp′) and anisotropy (A) of three types of eclogites and country rocks from the Dabie–Sulu ultrahigh-pressure (UHP) metamorphic belt, China, have been measured under confining pressures up to 800 MPa. Type-1 eclogites, which are coarse-grained and subjected to almost no retrograde metamorphism, experienced recovery-accommodated dislocation creep at peak metamorphic conditions (in the diamond stability field). Type-2 eclogites are fine-grained reworked Type-1 materials that experienced recrystallization-accommodated dislocation creep under quartz/coesite boundary conditions during the early stage of exhumation. Type-3 eclogites are retrogressed samples that were overprinted by significant amphibolite facies metamorphism during a late stage of exhumation within the crust. Type-1 eclogites are richer in Al2O3 and MgO but poorer in SiO2 and Na2O than Type-2 and Type-3 eclogites. Anisotropy of Type-1 and Type-2 eclogites is generally low (〈4%) because volumetrically important garnet is elastically quasi-isotropic, while Type-3 eclogites can exhibit high anisotropy (〉10%) due to the presence of strongly anisotropic retrograde minerals such as amphibole, plagioclase and mica. The transition of the pressure dependence of velocity from the poroelastic to elastic regimes occurs at a critical pressure (Pc), which depends mainly on the density and distribution of microcracks and in turn on the exhumation history of rocks. The Vp–pressure relationship can be expressed by Vp=a(lnP)2+blnP+c (P≤Pc) and Vp=V0+DP (P≥Pc), where P is the confining pressure, a and b are constants describing the closure of microcracks below Pc, c is the velocity when P is equal to one (MPa), V0 is the projected velocity of a crack-free sample at room pressure, and D is the intrinsic pressure derivative above Pc. When data are curve-fit, pressure derivatives and anisotropy as functions of pressure are determined. The average Vp of the eclogites in the linear regime is 8.42+1.41×10−4P for Type-1, 7.80+1.58×10−4P for Type-2, and 7.33+2.04×10−4P for Type-3, where Vp is in km/s and P in MPa. The decrease in V0 and increase in D from Type-1 to Type-3 eclogites are attributed to a decrease in garnet content and an increase in retrograde minerals. The NE–SW trending, NW-dipping, slab-like high Vp anomaly (8.72 km/s at a depth of 71 km) which extends from the Moho to at least 110 km beneath the Dabie–Sulu region, can be interpreted as the remnant of a subducted slab which is dominated by Type-1 eclogites and has frozen in the upper mantle since about 200–220 Ma. Such relic crustal materials, subducted and preserved as eclogite layers intercalated with felsic gneiss, garnet–jadeite quartzite, marble and serpentinized peridotite, could be responsible for regionally observed seismic reflectors in the upper mantle.

Description: Sea-level change in the Mediterranean Sea during glacial cycles is determined by the temporally variable eustatic change and by the spatially variable glacio-hydro-isostatic response of the earth and ocean to the growth and decay of ice sheets. Superimposed upon this are the relative changes from any vertical tectonic movement of the land. For sites that are either tectonically stable or where the magnitude of tectonic uplift is known, comparisons of observed change with predictions of the glacio-hydro-eustatic signals provide constraints on the earth–ice parameters used. The resulting predictive models can then be used to interpolate sea-level change and shoreline migration between the spatially and temporally limited observational data set. Whether such parameters reflect the true properties of the mantle and ice sheets depends on whether an effective separation has been achieved from the inversion of the observational data set. This paper explores this issue and demonstrates that observations from certain regions in the Mediterranean are particularly important in effecting the separation. This is supported by a trial analysis of a small observation data set from sites that exhibit some of the desirable features of an ideal data set. Basin-wide predictions of sea-level change, palaeo-water depth and shoreline locations based on these analyses are presented for selected epochs.

Description: We review the biology, ecology, fisheries, and resource status of the red flying squid (Ommastrephes bartramii) in the North Pacific focusing on recent literature published in Japan. The North Pacific population of O. bartramii comprises two seasonal cohorts (fall and winter–spring) and four stocks: (1) central stock of the fall cohort, (2) east stock of the fall cohort, (3) west stock of the winter–spring cohort, and (4) central-east stock of the winter–spring cohort. The population makes an annual round-trip migration between its subtropical spawning grounds where the sea surface temperature ranges from 21 to 25 °C and its northern feeding grounds near the Subarctic Boundary. O. bartramii matures at 7–10 months and has an estimated 1-year life span. Near the Subarctic Frontal Zone, adult squid commonly occupy 0–40 m depths at night and 150–350 m depths during the day. They prey primarily on fishes, squids and crustaceans. Predators include marine mammals and swordfish (Xiphias gladius). The North Pacific population of O. bartramii was targeted by an international driftnet fishery during 1978–1992, and annual catches reached more than 350,000 t during the 1980s. It is now targeted by jigging vessels from Japan, China, South Korea and Taiwan. Annual catches in the Japanese jigging fishery ranged from 49,000 to 71,000 t during the mid-1990s, but dropped to below 25,000 t in 2000 and 2001.

Description: We identified environmental associations (depth, bottom temperature and bottom salinity) of the shortfin squid Illex argentinus in the Northern Patagonian Shelf. Data are from 15 research bottom trawl surveys conducted in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) between 1985 and 1998. Squid distribution in the surveyed area showed significant associations (p 〈 0.05) mostly with depth and bottom temperature. Bathymetric associations of squid detected in March–April, May–June and July–August cruises revealed a preference of squid for deep depths (80–280 m, intermediate and external shelf) and cool bottom temperatures (4–10 °C, subantarctic water) within the survey area. In contrast, the results observed during November–December cruises showed a preference of squid for shallower depths (70–90 m) and warmer bottom temperatures. The majority of two-way environmental analyses showed significant associations, suggesting the existence of a strong correlation between the environmental factors used in our analyses. The identification of significant associations between squid distribution and bottom temperature seem to be related to the presence of strong thermal gradients within the study area. This could be supporting the existence of an association between I. argentinus with the Brazil–Malvinas confluence front and also with the shelf break front.

Description: The delta plain of the Rhone shows many sandy beach ridges cropping out at the surface. We propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation of the morphology of the mouth lobes that they form. Morphologies of the lobes depend on four principal factors: (1) the variation of the relative sea level, which constitutes the morphogenic base level, (2) the fluvial input (volume of water discharge and sedimentary input, number and position of the mouths), (3) marine dynamics (volume and direction of the longshore drift, dominant wave direction) (4) the accommodation space created by the rise of relative sea level, along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea. Our conclusions are: the main Holocene paleo-delta lobes of Ulmet and Saint Ferréol were contemporaneous, being deposited from 4000 to 2000 yr BP. However, the fluvial style of their downstream channel (meandering for Ulmet channel and linear for Saint-Ferréol) and the lobe morphologies of both channels are contrasted: rounded in the case of Ulmet and elongated for Saint-Ferréol. The role of the accommodation space is confirmed by two recent drillholes traversing the entire Holocene succession, which reveal a prior stage of sedimentary filling in the case of the Saint-Ferréol lobe, thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe. The decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of Rhône. However, the high rate of progradation of Saint-Ferréol lobe after 2900 BP is probably a consequence of the increase of human activity after this date. The variation of relative sea level remains an important factor controlling the evolution of the Rhone delta after 6000 BP. The local (?) stabilization of the relative sea level between 4585 BP and 3520 BP played an important role in the triggering of coastal progradation (Saint-Ferréol lobe, eastern margin Rhône delta).

Description: Surface meteorology, upper ocean current, and hydrographic measurements, collected along a repeated survey pattern and from a central mooring in the western equatorial Pacific during late 1992 to early 1993, were used to analyse upper ocean momentum balances on the intraseasonal time scale. Wind stresses derived from meteorological measurements were compared with numerical weather prediction products. Advection terms in the momentum equations were estimated by planar fits to the current and hydrographic data. Pressure gradient terms were derived from planar fits to the dynamic heights calculated from the hydrographic data, referenced by balancing the momentum equation in a selected layer below the mixed layer. Under prevailing westerly winds, westward pressure gradient forcings of 2 x 10 -7 ms -2 were set up in the western equatorial Pacific, countering the surface wind, while the total advection tended to accelerate the eastward momentum in the surface layer. During both calm wind and westerly wind burst periods, zonal turbulent momentum fluxes estimated from the ocean budgets were comparable with those estimated from microstructure dissipation rate measurements and with zonal wind stresses, so that the zonal momentum could be balanced within error bars. The meridional momentum balances were noisier, which might be due to the fact that the short meridional length scale of the equatorial inertial-gravity waves could contaminate the dynamic signals in the mixed temporal/spatial sampling data, so that the meridional gradient estimates from the planar fits could be biased.

Description: Sands for the nourishment of beaches along the Emilia-Romagna coast (northern Adriatic Sea) were dredged from an offshore area characterised by relict sands formed during the last Adriatic post-glacial transgression. The short-term effects of the sand extraction on macrozoobenthic communities were investigated before, during and 1, 6 and 12 months after dredging at three impacted stations and seven control stations. Sand extraction activities did not significantly influence the granulometry and %TOC in the sediment but caused almost complete defaunation at dredging stations. Yet, just 12 months after the extraction, the recolonisation of communities at the impacted stations was at an advanced stage. Unlike other studies on the effects of extraction of marine sand, no significant settlement of opportunistic species was observed. The limited impact of the sand extraction operation on the physical characteristics of the sediment and hydrological-sedimentary characteristics in the relict sand area should aid its rapid recovery and the restoration of the original community in a short period of time (2–4 years after dredging).

Description: We used the Imaging-PAM fluorometer to map spatial variability of photosynthesis in three seagrass species, Halophila ovalis, Zostera capricorni and Posidonia australis. Photosynthesis was described by relative photosynthetic rate (PS/50), effective quantum yield (ΦPSII), non-photochemical quenching (NPQ and qN), electron transport rate (ETR) and leaf absorptivity. Photosynthetic patterns were linked to leaf age and light climate but patterns were not consistent across species. Longitudinal heterogeneity in photosynthesis was apparent along the leaves of all three species while lateral spatial heterogeneity was found only across Z. capricorni and H. ovalis leaves. Age of leaf tissue, determined by longitudinal location on the leaf, strongly influenced photosynthetic activity of Z. capricorni and P. australis. A comparison of H. ovalis leaves of differing maturity demonstrated the influence of leaf age on photosynthetic activity, yet a comparison of Z. capricorni leaves of differing maturity showed no leaf-age effects. Variations in stress-induced changes across a seagrass leaf can be used to identify areas or particular regions of the leaf, which are more susceptible to photodamage. Clear evidence of substantial within-leaf heterogeneity in photosynthetic activity (i.e., a two-fold variation in half saturation constant along a leaf of P. australis) has serious implications for use of small sections of leaf for photosynthetic incubations (such as O2 or single-point chlorophyll a fluorescence measurements).

Description: Gravity cores from the continental slope in the northwestern Black Sea were studied using high-resolution stable isotope, grain size and XRF-scanning data. The measurements provide a 30 000 years AMS 14C-dated record of variations in the hydrological regime of the Black Sea and give insight into changing paleoenvironments in the surrounding areas. Stable climatic conditions during the Last Glacial Maximum were followed by a series of meltwater pulses most likely originating from the Scandinavian ice sheet between 18 000 and 15 500 yr BP.1 This meltwater input rose the level of the Caspian Sea to a point that Caspian water could spill into the Black Sea via the Manych-depression north of the Caucasian mountains. High-frequency oscillations in the XRF-data during this period suggest a probable link to the arctic climate regime. Later, during the Bølling/Allerød and the early Holocene, prevailing high temperatures led to authigenic calcite precipitation through increased phytoplankton activity, interrupted by the Younger Dryas and the “8200 yr BP cold event” with dominant clastic sedimentation.

Description: The first high-resolution mapping of mud volcanoes and mud domes of the Central Mediterranean Ridge (Eastern Mediterranean) presented here is based on successive in situ observations from the Nautile submersible [MEDINAUT (1998) and NAUTINIL (2003) surveys] and near-bottom side-scan sonar data (MEDINETH cruise, 1999). Data were obtained over two types of clay-kinetic-related features previously identified south of Crete: the Olimpi field mud volcanoes and the Southern belt mud domes, characterized by highly contrasting morpho-acoustic characteristics. Using the new data we can better define the morphological and backscatter characteristics of both mud volcanoes and mud domes and illustrate their similarities and differences; and establish ground truth, in terms of the presence or not of mud flows, diagenetic carbonate pavements, active seepage and macro-and microbiology. This study reveals strong contrasts between: (1) large mud volcanoes, made of successive mud flows, and associated with diagenetic carbonates and fluid venting activity, and (2) smaller mud domes, characterized by steep slopes affected by sedimentary instabilities, and without any evidence of mud flow, specific fluid seepage activity, authigenic carbonate pavement, or biologic communities. From these results we demonstrate a strong variability of clay-kinetic structures from the central domain of the Mediterranean Ridge accretionary complex to its northern thrust boundary against the Cretan continental backstop. From an integration of the high-resolution results to the Mediterranean Ridge geologic and structural settings, a qualitative model is finally proposed to explain the mud volcano and mud dome emplacement.

Description: Sepia apama were tagged with acoustic transmitters and monitored on their native House Reef, Boston Bay, South Australia, with a radio acoustic positioning telemetry (RAPT) system. Cuttlefish were tagged with position-only and intra-mantle jet pressure transmitters. New data analyses were developed to handle problem data that arise with an uneven reef environment. Maximum range for the cuttlefish varied from 90 m to 550 m. Cuttlefish home range was between 5300 m2 and 23,700 m2. S. apama were found to be diurnal as average distance travelled was higher in the day than at night, and cuttlefish were active for 32 days, but only 18 nights. After the cuttlefish settled into reef crevices, activity spectrum and positioning analysis showed foraging behaviour at only 3.7% per day and 2.1% per night. Cuttlefish were found to spend more than 95% of the day resting, which suggests that their bioenergetics are more akin to those of octopus than of squid. The cuttlefish combination of predator avoidance, efficient foraging and quiescent lifestyle allows energy to be channelled into growth and fulfillment of the live-fast-die-young cephalopod philosophy.

Description: We review the fishery for the diamond squid (Thysanoteuthis rhombus) in Japan and recent Japanese research conducted on this species. T. rhombus occurs worldwide in tropical and subtropical waters, including near southern and central Japan, where it is targeted by a growing fishery. The annual catch in Japan increased from 339 t in 1989 to almost 6000 t in 2001, and during 1998–2003, averaged close to 4900 t. The main fishing grounds are located in the Sea of Japan, Okinawa Prefecture, and Kagoshima Prefecture, and 90% of the total catch is made in the Sea of Japan and Okinawa. In the Sea of Japan, it is caught with free-floating angling gear called “taru-nagashi” and inshore trap nets; the fishery there usually runs from July to February, with highest catches occurring in September–December. The annual catch in the Sea of Japan during 1998–2003 ranged between 1600 and 3700 t. In Okinawa, it is fished primarily in the daytime with free-floating angling gear called “hata-nagashi”; the fishery there runs mainly from November to April, with highest catches occurring in February–April. The annual catch in Okinawa increased from 15 t in 1989 to 2300 t in 2003. The free-floating egg masses of T. rhombus occur widely in surface waters near southern and central Japan, and paralarval distribution patterns suggest that it spawns over a wide area almost year-round. Part of the population is transported by the Tsushima Current into the Sea of Japan, but little is known about this migration. The vertical distribution of T. rhombus varies regionally; in Okinawa, it occurs mainly at 300–650 m depth during the day and 0–150 m depth at night, while in the Sea of Japan, it occurs mainly at 75–100 m depth during the day and 0–50 m depth at night. Its life span is thought to be about 1 year, and squid larger than 30 cm mantle length grow about 7–10 cm mo−1.

Description: The resolution of higher level phylogeny of the coleoid cephalopods (octopuses, squids, and cuttlefishes) has been hindered by homoplasy among morphological characters in conjunction with a very poor fossil record. Initial molecular studies, based primarily on small fragments of single mitochondrial genes, have produced little resolution of the deep relationships amongst coleoid cephalopod families. The present study investigated this issue using 3415 base pairs (bp) from three nuclear genes (octopine dehydrogenase, pax-6, and rhodopsin) and three mitochondrial genes (12S rDNA, 16S rDNA, and cytochrome oxidase I) from a total of 35 species (including representatives of each of the higher level taxa). Bayesian analyses were conducted on mitochondrial and nuclear genes separately and also all six genes together. Separate analyses were conducted with the data partitioned by gene, codon/rDNA, gene + codon/rDNA or not partitioned at all. In the majority of analyses partitioning the data by gene + codon was the appropriate model with partitioning by codon the second most selected model. In some instances the topology varied according to the model used. Relatively high posterior probabilities and high levels of congruence were present between the topologies resulting from the analysis of all Octopodiform (octopuses and vampire “squid”) taxa for all six genes, and independently for the datasets of mitochondrial and nuclear genes. In contrast, the highest levels of resolution within the Decapodiformes (squids and cuttlefishes) resulted from analysis of nuclear genes alone. Different higher level Decapodiform topologies were obtained through the analysis of only the 1st + 2nd codon positions of nuclear genes and of all three codon positions. It is notable that there is strong evidence of saturation among the 3rd codon positions within the Decapodiformes and this may contribute spurious signal. The results suggest that the Decapodiformes may have radiated earlier and/or had faster rates of evolution than the Octopodiformes. The following taxonomic conclusions are drawn from our analyses: (1) the order Octopoda and suborders Cirrata, Incirrata, and Oegopsida are monophyletic groups; (2) the family Spirulidae (Ram’s horn squids) are the sister taxon to the family Sepiidae (cuttlefishes); (3) the family Octopodidae, as currently defined, is paraphyletic; (4) the superfamily Argonautoidea are basal within the suborder Incirrata; and (5) the benthic octopus genera Benthoctopus and Enteroctopus are sister taxa.

Description: A series of regular large-scale acoustic surveys was carried out over the exclusive economic zone (EEZ) of the south and southeast Brazilian coast, along the external shelf and shelf break areas, during the winter of 1996 and the spring of 1997. Different echo-types were recorded, most of them due to small to medium size mesopelagic foraging fish such as Maurollicus stehmanni and Myctophidae species. Deeper acoustic records were also observed in the mesopelagic stratum at night forming extensive layers at depths of over 200 m. These echo-records were not registered during the day. An analysis of the echograms showed that the echo-traces at depths between 200 and 700 m were horizontally extended with colours varying from dark blue to light green. In order to sample the organisms, which formed the deep acoustic targets (DATs), further cruises were conducted with a combination of acoustics and fishing to capture organisms in the water column and on the bottom. This study analyses the results of the surveys in order to identify the organisms responsible for the echo records and evaluate their specific composition.

Description: Over a 12-year period (1989–2000) the spatial and temporal distribution of zooplankton in the Laptev Sea (Arctic Siberia) has been investigated. A total number of 111 taxa from 10 phyla were found. Sixteen species are reported from this region for the first time. The distribution and abundance of zooplankton on the Laptev Sea shelf is dependent on the main direction of river water spread, which varies between years. While the western and northeastern Laptev Sea shelf is dominated by a marine–neritic fauna, the central part is inhabited by a transitional brackish–marine assemblage. A brackish–neritic community characterizes the eastern and southeastern regions, where lowest salinities usually prevail. Closer to estuaries the summer zooplankton consists of both freshwater and brackish-water species, whereas in winter brackish-water species are dominant. Average zooplankton abundance varies seasonally and interannually, particularly in the southeastern Laptev Sea. The amplitude of these variations mainly depends on the state of the populations of the most common Copepoda species, the intensity of their reproduction, and their success in overwintering. Two seasonal abundance maxima were found, at the end of winter and at the end of summer. During the period of highest reproduction in summer the abundance may be 50 times greater than during overwintering. The average population abundance can vary by the factor of 2 in summer and in winter from year to year.

Description: Two active chemoherm build-ups growing freely up into the oceanic water column, the Pinnacle and the South East-Knoll Chemoherms, have been discovered at Hydrate Ridge on the Cascadia continental margin. These microbially-mediated carbonate formations rise above the seafloor by several tens of meters and display a pinnacle-shaped morphology with steep flanks. The recovered rocks are pure carbonates dominated by aragonite. Based on fabric and mineralogic composition different varieties of authigenic aragonite can be distinguished. Detailed visual and petrographic investigations unambiguously reveal the involvement of microbes during the formation of the carbonates. The fabric of the cryptocrystalline and fibrous aragonite can be described as thrombolitic. Fossilized microbial filaments in the microcrystalline aragonite indicate the intimate relationship between microbes and carbonates. The strongly 13C-depleted carbon isotope values of the samples (as low as − 48.1 ‰ PDB) are characteristic of methane as the major carbon source for the carbonate formation. The methane-rich fluids from which the carbonates are precipitated originate most probably from a gas reservoir below the bottom-simulating reflector (BSR) and rise through fault systems. The δ18O values of the aragonitic chemoherm carbonates are substantially higher (as high as 5.0 ‰ PDB) than the expected equilibrium value for an aragonite forming from ambient seawater (3.5 ‰ PDB). As a first approximation this indicates formation from glacial ocean water but other factors are considered as well. A conceptual model is presented for the precipitation of these chemoherm carbonates based on in situ observations and the detailed petrographic investigation of the carbonates. This model explains the function of the consortium of archaea and sulfate-reducing bacteria that grows on the carbonates performing anaerobic oxidation of methane (AOM) and enabling the precipitation of the chemoherms above the seafloor surrounded by oxic seawater. Beggiatoa mats growing on the surface of the chemoherms oxidize the sulfide provided by sulfate-dependent anaerobic oxidation of methane within an oxic environment. The contact between Beggiatoa and the underlying microbial consortium represents the interface between the overlying oxic water column and an anoxic micro-environment where carbonate formation takes place.

Description: Transport of Baltic sprat Sprattus sprattus L. larvae spawned on different spawning grounds was investigated by detailed drift model simulations for the years 1979–2002. Modeling approaches with and without diurnal vertical migration were applied. We used recently collected data on spawning location, vertical distribution and the timing of spawning as input to a particle tracking model. Results of this modeling study enabled the identification of potential nursery grounds for sprat originating from different spawning grounds. On average, westerly winds are prevailing over the Baltic Sea. This leads to on average higher abundance of juvenile sprat along the southern and the eastern coast lines of the Baltic. The horizontal distribution of simulated larval or 0-group sprat is consistent with the observed distribution of 0-group sprat obtained from the hydroacoustic field surveys. In addition, this analysis identifies the potential for advective mixing between juveniles originating from different spawning sites or from the same spawning site throughout the spawning season. High spatial overlap was found between Arkona- and Bornholm Basin larvae hatched at the beginning of the spawning season. Mixing probability of sprat juveniles between Arkona- and Gotland Basin as well as between Bornholm- and Gotland Basin were on relatively low levels.

Description: Results of particle flux studies using sediment traps in the northeast Atlantic Ocean at 33oN, 22oW, a time-series station (L1/K276) operated within the German contribution to the international Joint Global Ocean Flux Study (JGOFS) between summer 1993 and summer 2001, are presented. The particle flux at 2000 m depth is highly seasonal with only one main peak in February and March and is characterized by strong interannual variability. The comparison of the particle flux time series with the measurements of chlorophyll and phaeopigments in the sediment trap material, and chlorophyll-a concentrations at surface from SeaWiFS together with the similarity of the pattern observed in the alkenone flux, particulate organic carbon (POC) and calcium carbonate (CaCO3) leads to the conclusion that the particle flux at this position is fast and directly coupled to the phytoplankton development and decay in the overlying euphotic zone. SeaWiFS chlorophyll-a data (1997-2001) and characteristics of the upper water column (mixed layer depth, depth of nitracline, primary production) as predicted by an eddy-permitting model of the North Atlantic coupled with a simple nitrate-phytoplankton-zooplankton-detritus (NPZD) pelagic-ecosystem model are used to understand the observed interannual differences in particle flux at 2000 m. Our results suggest that the interannual differences in the observed particle flux are a direct consequence of the variability of phytoplankton biomass and primary production in the euphotic zone in this region.

Description: The importance of grain size as a fundamental property controlling other physically derived properties is well known. Recent grain-size studies on periplatform sediments of the Caribbean and western north Atlantic have shown that grain-size variability is coupled with changes in carbonate platform productivity and export in response to Pleistocene–Holocene glacio-eustacy. These findings showed that periplatform sediments are dominated by fine-grained material during sea-level highstands and coarser material during sea-level lowstands. This paper addresses the question of grain-size patterns in periplatform settings and their relationship to glacio-eustacy. Furthermore, it considers whether these patterns are applicable to different types of margin settings (accretionary-erosional). Here, existing data (Pleistocene–Holocene) from the accretionary western leeward margin of Great Bahama Bank (ODP Leg 166) and new data from the erosional eastern windward margin (ODP Leg 101) are used. The results show that the grain-size patterns of both margins are controlled by late Neogene sea-level fluctuations. The accretionary leeward margin sediments indicate the same grain-size pattern as previously described in the literature. However, the erosional windward margin shows a reverse pattern, with coarser sediments in interglacials and finer deposits in glacials. This proposes that the leeward margin grain-size pattern is controlled by the productivity-export mode of the platform. This is indicated by the platform-top-derived fine muds, transported off-bank, to form a thick sediment wedge on the low-angled slope during interglacials. In contrast, on the windward margin, the sediment flux pattern is controlled by the impact of mass transport processes. This is indicated by the increased occurrence of turbidites during interglacials that might be more frequent at this time because the steep-angled erosional slope is less apt for the deposition of excess fine material. This material is eroded and/or bypasses the slopes and is redeposited in the periplatform basin setting.

Description: In a sediment core from the leeward side of the Great Bahama Bank (Ocean Drilling Program ODP-Leg 166, 1006A-24H, early Pliocene) several paleoceanographic proxies were compared with carbonate mineralogy. The proxies measured on the planktonic foraminifera species Globigerinoides sacculifer are Mg/Ca and Sr/Ca elemental ratios, and δ18O values. These proxies are widely used in pelagic sediments to derive parameters of water masses, such as paleo-temperature and -salinity. To produce quantitative estimates it is necessary to verify that the primary shell mineralogy of the foraminifera was not altered diagenetically. Diagenetic alteration can be rapid in periplatform settings relative to pelagic deep-sea sediments, since the meta-stable carbonate phases provide an additional driving force for recrystallisation. We show that the Sr/Ca ratio of foraminiferal calcite can be used to assess the degree of diagenetic alteration of their shell chemistry. Using this method, we demonstrate that the primary signal in the oxygen-isotope ratios is preserved in the studied core. In the Mg/Ca record, the relative change of foraminiferal Mg/Ca ratios seems to be preserved, but absolute values are influenced by diagenesis. The second set of proxies comprises δ13C and C/N ratios of organic carbon. These are used in pelagic sediments in order to assess the origin of organic carbon (terrestrial or marine phytoplankton). It is demonstrated here that a simple two-end mixing model cannot explain the observed co-occurrence of relatively high δ13Corg and C/N values. As the δ13Corg values co-vary with the aragonite content, we attribute this signature to varying contribution of organic carbon from benthic algae, which are also the major aragonite producers on the platform top.

Description: 231Pa and 230Th are removed from the water column by a process of reversible scavenging which quickly removes 230Th to the sediment. 231Pa is less efficiently scavenged onto particles than 230Th and is therefore more effectively transported via advection and diffusion before it reaches the ocean sediment. This study combines particle fields (dust, opal, CaCO3, POC) derived from observations with the Bern3D intermediate complexity ocean model and an equilibrium-scavenging model for isotopes. The equilibrium partition coefficient for particulate versus dissolved isotope activity is varied with particle type. The model can explain many of the features of the global 231Pa and 230Th distribution. The success of such a simple model at representing the global pattern of 231Pa / 230Th activity ratio supports the use of this proxy in paleoceanographic studies. We use the model to address the controversy concerning which particle types are dominant in fractionating 231Pa / 230Th in the ocean. The lithogenic (dust) flux is found to be unimportant for 231Pa / 230Th fractionation— the ocean fractionation of 231Pa / 230Th is dominated by the distribution of the CaCO3 and opal flux. We also confirm that opal is a weak scavenger of 230Th.

Description: We present a numerical model study in order to quantify the effects of organic carbon (POC) degradation and fluid migration on methane and gas hydrate formation at ODP site 1040 (Costa Rica convergent margin). Various model runs show that POC-degradation in upper plate sediments yields a potential for methane hydrate formation between 0.8 and 2.5 vol.% of pore space. However, observed chlorinity anomalies cannot be explained by the amount and the distribution pattern of gas hydrates. Moreover, pore water profiles of ammonia do not match the observations. Setting up a moderate upward flow (0.03 cm yr− 1) of methane-enriched, low-chlorinity fluids (induced by dewatering of oceanic plate sediments) leads to a good approximation to measured pore water profiles, thus enabling a precise estimate of POC degradation kinetics. Fluid flow has a strong impact on the location of the upper limit of the modeled gas hydrate occurrence zone (GHOZ) and may increase the total amount of gas hydrate by more than 50%. Our best estimate of the amount of gas hydrate within the GHOZ is on average 1.65 vol.% of pore space, which corresponds to about 2.5 Tg of methane per km trench within the frontal prism of slope sediments. To comply with the fact that subducted pore waters are rich in sulfate and that there is striking evidence for fluid conduits at various depths we performed additional model runs, where we simulated fluid flow by using a Gauss-type rate law, allowing us to define distinct fluid sources. We can demonstrate that combined methane production in the upper plate sediments and sulfate reduction at the top of the down going slab is sufficient to prevent the upward movement of the zone of anaerobic oxidation of methane (AOM) to above the décollement at given upward advection rates. Steep pore water gradients along the plate boundary can be explained by lateral backflow within oceanic plate sediments. On a long term (in the order of at least some 100,000 years), fluid flow along conduits is likely to occur at low rates with temporarily increased pulses. All modeled runs are constrained by their compatibility to observed pore water profiles.

Description: The role of mantleplumes in the formation of intraplate volcanic islands and seamount chains is being increasingly questioned. Particular examples are the abundant and somewhat irregularly distributed island and seamount volcanoes off the coast of northwest Africa. New40Ar / 39Ar ages and Sr–Nd–Pb isotope geochemistry of volcanic rocks from seamounts northeast of the Madeira Islands (Seine and Unicorn) and northeast of the Canary Islands (Dacia and Anika), however, provide support for the plumehypothesis. The oldest ages of shield stage volcanism from Canary and Madeiravolcanic provinces confirm progressions of increasing age to the northeast. Average volcanicage progression of ∼1.2 cm/a is consistent with rotation of the African plate at an angular velocity of ∼0.20° ± 0.05 /Ma around a common Euler pole at approximately 56° N, 45° W computed for the period of 0–35 Ma. A Euler pole at 35° N, 45° W is calculated for the time interval of 35–64 Ma. The isotope geochemistry further confirms that the Madeira and Canary provinces are derived from different sources, consistent with distinct plumes having formed each volcanic group. Conventional hotspot models, however, cannot easily explain the up to 40 m.y. long volcanic history at single volcanic centers, long gaps in volcanic activity, and the irregular distribution of islands and seamounts in the Canary province. A possible explanation could involve interaction of the Canarymantleplume with small-scale upper mantle processes such as edge-driven convection. Juxtaposition of plume and non-plume volcanism could also account for observed inconsistencies of the classical hotspot concept in other volcanic areas.

Description: We have conducted a barometric study of basaltic lavas and mafic to ultramafic xenoliths from Cumbre Vieja volcano (La Palma) in order to reconstruct magma storage, plumbing and related intrusive island growth. The samples were collected both along the volcano's rift zone and from its subaerial and submarine flanks up to 30 km off the rift axis. Clinopyroxene–melt barometry of lavas yields a well-defined pressure range of 410–770 MPa (average 600 MPa) and shows no systematic variation with sample locality. This pressure range reflects a major fractionation level at ca. 15–26 km depth, within the uppermost mantle, where phenocrysts and melt last equilibrated. In contrast, microthermometry of CO2-dominated fluid inclusions in phenocrysts and xenoliths gives pressure estimates of 240 to 470 MPa (average 330 MPa), within the lower oceanic crust. These pressures are interpreted to reflect an underplating zone at 7–14 km depth where ascending magmas become ponded prior to eruption and where passing magmas temporarily stagnate during eruption. The underplating zone is inferred to extend to a radius of ca. 30 km at least, and its depth appears to increase slightly with distance to the rift axis. Our data thus show a remarkable pressure bimodality for long-term and short-term storage of magma that appears to be characteristic for Cumbre Vieja. By using a simple model based on the cumulative volume of material added to the crust, we have estimated uplift rates of 〉 0.5 m/ka due to underplating that occurs on the island scale. On a time-scale of some 10 ka, these uplift rates are of similar magnitude as global changes in sea-level. A second, more local mode of uplift and related faulting is caused by shallow intrusions into the volcanic edifice as is indicated by the highly irregular morphology of the Cumbre Vieja. We stress that intrusion-related uplift should be qualitatively considered when reconstructing the evolution of oceanic island volcanoes. Since most of the underplated material is inferred to consist of cumulate rocks being intimately mixed and juxtaposed with the lower oceanic crust and having similar densities, it is probably impossible to detect such an underplating zone seismically.

Description: Detailed heat flow surveys on the oceanic trench slope offshore Nicaragua and Central Chile indicate heat flow values lower than the expected conductive lithospheric heat loss and lower than the global mean for crust of that age. Both areas are characterised by pervasive normal faults exposing basement in a setting affected by bending-related faulting due to plate subduction. The low heat flow is interpreted to indicate increased hydrothermal circulation by the reactivation and new creation of faults prior to subduction. A previous global approach [1] [Stein C.A., Heat flow and flexure at subduction zones, Geophys. Res. Lett. 30 (2003) doi:10.1029/2003GL018478] failed to detect similar features in the global but sparse data set. Detailed inspection of the global data set suggests that the thickness of the sedimentary blanket on the incoming plate is an important factor controlling the local hydrogeological regime. Areas with a relatively thick sedimentary cover do not show any heat flow anomaly while areas where normal faulting exposes basement suffer from increased hydrothermal activity. Both geochemical data from arc volcanoes and seismological evidence from intra slab events suggest that the flux of water into the deep subduction zone is larger in areas characterised by reactivated hydrothermal circulation. It is reasonable to assume that the larger water flux is caused by serpentinization of the upper mantle, facilitated by bending-related faults cutting into the upper mantle.

Description: We present the first coral climate proxy data (Sr / Ca, δ18O, δ13C) from the Persian–Arabian Gulf using a Porites lutea coral collected offshore Kuwait. Both oxygen isotope- and Sr / Ca-ratios of the coral core investigated are statistically correlated with instrumental sea surface temperatures (SST) for the area from 1980–2002. However, the temperature calibration curve for Sr / Ca differs from other published curves in that its slope is much lower. The correlation coefficient between δ18Ocoral and instrumental SST is at the lower limit as compared to other sites. These differences most likely relate to insufficient data representation of cold winters and hot summers, and indicates that much higher sampling resolution is needed in marginal reef areas such as Kuwait with extreme environmental fluctuations, i.e., intra-annual SST-variation of 16–34 °C, as compared to low latitude locations with relatively low SST variation. Variations of carbon isotopes of the coral skeleton do not exhibit climate control, however, a negative excursion in 1991 might be attributed to the massive oil field fires of the II. Gulf War.

Description: The interaction between river water and landfast sea ice was investigated through synthetic aperture radar (SAR) remote sensing, ice-growth modeling, and ground-based ice-core and hydrographic studies in the Laptev Sea, Siberian Arctic, in 1996/1997 and 1998/1999. Ice-core data in conjunction with ice-growth and SAR backscatter modeling demonstrated that the contrasts in dielectric and microstructural properties between freshwater/brackish (salinity 〈 1 parts per thousand) and sea ice allow a mapping of the distribution of freshwater and brackish ice as influenced by Lena River discharge. This brackish zone (surface water salinities 〈 5) extended over 2000-3000 km(2) inshore of the 10-m isobath and exhibited distinct SAR backscatter coefficients and image texture. In the nearshore zone, bottomfast ice growth could be identified and tracked over the growth season. Occupying up to 250 km(2) along the Lena Delta, bottomfast ice was not as widespread as previously hypothesized, possibly due to ice being thinner by 10-20% relative to the signatures of any ice long-term mean. In SAR and ERS-2 scatterometer data, Laptev Sea landfast ice exhibits the lowest backscatter si a type in the Arctic Ocean, due to the lack of major deformation features. Stable-isotope data show that the landfast ice is composed of about 62% of river water, locking up 24% of the total annual Lena and Yana discharge. From ice-growth/isotopic-fractionation modeling and ice-core analysis, time series of surface water salinity have been derived, indicating freshening of under-ice waters during winter and north-/northeastward spreading of the river plume with under-ice spreading rates of 1.0-2.7 cm s(-1). A river freshwater budget for the inner Laptev shelf indicates flushing times of a year or more with cross-shelf export of 627 km(3) during the winter of 1998/1999. Based on these findings, the southeastern Laptev Sea can be considered an open, seasonally frozen estuary. This system contrasts with North American shelf environments, which show a different response to climate variability and change.

Description: ODP Leg 204, which drilled at Hydrate Ridge, provides unique insights into the fluid regime of an accretionary complex and delineates specific sub-seafloor pathways for fluid transport. Compaction and dewatering due to smectite–illite transition increase with distance from the toe of the accretionary prism and bring up fluids from deep within the accretionary complex to sampled depths (≤ 600 mbsf). These fluids have a distinctly non-radiogenic strontium isotope signature indicating reaction with the oceanic basement. Boron isotopes are also consistent with a deep fluid source that has been modified by desorption of heavy boron as clay minerals change from smectite to illite. One of three major horizons serves as conduit for the transport of mainly fluid. Our results enable us to evaluate fluid migration pathways that play important roles on massive gas hydrate accumulations and seepage of methane-rich fluids on southern Hydrate Ridge.

Description: Phases with massive abundances of Uvigerina species recorded in North Atlantic deep-sea cores were previously attributed to water mass properties or to extended high productivity during the last Glacial. We investigated the Uvigerina distribution in 53 sediment cores and 555 surface samples from the north-eastern Atlantic ranging from 308 to 708N and 1 to 4410 m water depth. Our results showed that Uvigerina pigmea dominated in late Pleistocene assemblages whereas Uvigerina peregrina and Uvigerina peregrina parva were common during the Holocene. Uvigerina pigmea lives today in the Gulf of Guinea and South Atlantic only (98N to 178S), but was present up to 548N during the Last Glacial Maximum. The species retreated north- and southwards during Termination I and disappeared in the north-eastern Atlantic off northern Portugal 6100 years ago. Uvigerina peregrina and U. peregrina parva spread out from isolated occurrences along the continental slope off western Iberia at the onset of Termination I. Uvigerina peregrina exhibited Recent abundance maxima at Goban Spur, Plateau des Landes, and the Iberian Margin. These areas are subjected to strong lateral advection by downslope transport and sediment focusing. The actual flux rate of particulate organic matter is locally raised by a factor of 4 to 5. Comparable flux rates were otherwise recorded at U. peregrina maxima under the NW-African coastal upwelling regime. The Recent distribution of U. pigmea and evidence from sediment cores show an organic carbon flux of 3.5 g C m-2 yr-1 as minimum for a sustainable population of this species. Alkenone, pigment and planktonic foraminiferal records from cores MD952039 and MD952040 revealed that a spring bloom dominated productivity dynamics and a balanced food particle composition of haptophyteae algae and diatoms were limiting environmental factors for U. pigmea during the Pleistocene. A widespread change from glacial to modern productivity characteristics during the last Deglaciation may have triggered the early Holocene disappearance of U. pigmea from the north-eastern Atlantic.

Description: Despite their importance for the global oceanic nitrogen (N) cycle, estimates of N fluxes in the Arabian Sea remain in considerable uncertainty. In this report, we summarize current knowledge of important processes, including denitrification, N2 fixation and nitrous oxide emissions. Additionally, we discuss anthropogenic impacts on the N cycle in the region. Existing studies suggest that the Arabian Sea is a significant source of N2O, and a major sink for fixed-N mainly due to enhanced rates of denitrification that occur in suboxic portions of the water column in the Arabian Sea. Sedimentary denitrification is small compared to water column denitrification, and additions of fixed-N via N2 fixation also are small compared to pelagic denitrification. As a consequence, the fixed-N budget of the Arabian Sea is dominated by an advective supply from the south, and by the sink arising from pelagic denitrification. Although relatively small compared to the advective supply, inputs of fixed-N from runoff and from the atmosphere may have significant impacts on surface waters and on the coastal waters of western India, and these inputs are rising because of human activities. Overall, the Arabian Sea’s nitrogen cycle is likely to respond sensitively to climate change and, in turn, have an impact on climate via its N2O and denitrification components.

Description: We use global climate simulations across one precessional cycle to investigate the effect of orbitally induced climatic changes on sedimentation in the Western Interior Seaway (WIS) of North America at the Cenomanian/Turonian boundary. The simulations include a control run with no orbital eccentricity and hence no precession cycle, and four runs with varying precession with an eccentricity of 0.05 having (1) northern spring equinox at perihelion, (2) northern winter solstice at perihelion, (3) northern fall equinox at perihelion, and (4) northern summer solstice at perihelion. These numeric climate simulations and field observations suggest that the WIS at the Cenomanian/Turonian boundary can be divided into three latitudinal units: (1) A northern unit (Alberta–Montana) between 51°N and 71°N paleolatitude where conditions remained constant under the influence of steady inflow of low salinity, cool waters which were devoid of calcareous plankton flowed in from the Arctic, preventing the development of bedding couplets. (2) A central unit (Wyoming–Colorado) between 41°N and 51°N paleolatitude where runoff from Western North America (WNA) was reduced by more than half when the northern hemisphere winter solstice coincided with perihelion, where bedding couplets are well developed. The central part of the WIS was characterized by warm saline waters with abundant calcareous plankton. However it experienced high summer surface runoff from the Sevier Highlands to the west during all orbital configurations except when the winters were unusually warm, with the northern hemisphere winter solstice occurring at perihelion. Seasonal dilution of the surface waters of the seaway may have resulted in formation of a “fresh water lid” with stratification of the water column throughout most of the precession cycle. When the northern hemisphere winter solstice was at perihelion, reduced runoff would promote vertical mixing. Concomitantly, a steady detrital sediment supply would occur in summer throughout the precession cycle except when the NH winter solstice was at perihelion, when it would be much reduced. Thus the marlstone of the limestone–marlstone couplets would represent most of the time of the precession cycle and the limestone layers would represent the time when the NH winter solstice was near perihelion. (3) A southern region (New Mexico–northern Mexico) from 21° to 42°N paleolatitude where the detrital sediment supply was much reduced and couplets are thicker and less well developed.

Description: The zebrafish (Danio rerio) is a widely used model for developmental biology, neurobiology, toxicology, and genetic disease. Recently, the zebrafish has been recognized as a valuable model for infectious disease and immunity. In this study the pathogenesis and inflammatory cytokine response of zebrafish to experimental Edwardsiella tarda infection was characterized. In challenge experiments, zebrafish embryos were susceptible to infection by immersion. Adult fish were susceptible to challenge by intraperitoneal (ip) injection but not static immersion unless the epithelial layer was perturbed by scraping prior to exposure. To determine if E. tarda infection induces a typical acute inflammatory response, mRNA expression levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα) were assessed by quantitative real-time PCR. The expression levels of IL-1β and TNFα were significantly upregulated in infected zebrafish embryos and adults. The methods developed in this study will be particularly valuable for targeted gene disruption studies of host immune components and in zebrafish genetic screens.

Description: The upper ocean large-scale circulation of the western tropical Atlantic from 11.5°S to the Caribbean in November and December 2000 is investigated from a new type of shipboard ADCP able to measure accurate velocities to 600 m depth, combined with lowered ADCP measurements. Satellite data and numerical model output complement the shipboard measurements to better describe the large-scale circulation. In November 2000 the North Brazil Undercurrent (NBUC) was strongly intensified between 11 and 5°S by inflow from the east, hence the NBUC was formed further to the north than in the mean. The NBUC was transporting 23.1 Sv northward at 5°S, slightly less than the mean of six cruises (Geophysical Research Letters (2002) 29 (7) 1840). At 35°W the North Brazil Current (NBC) transported 29.4 Sv westward, less than the mean of 13 cruises (Geophysical Research Letters (2003) 30 (7) 1349). A strong retroflection ring had just pinched off the NBC retroflection according to the satellite information. The inflow into the Caribbean south of 16.5°N originated in part of a leakage from the NBC retroflection zone and in part from the North Equatorial Current. A thermocline intensified ring with a transport of about 30 Sv was located off Guadeloupe carrying South Atlantic Central Water towards the north. Observed deviations of the November/December 2000 flow field from the November long-term mean flow field were related to an enhanced Intertropical Convergence Zone (ITCZ) associated with an increased North Equatorial Countercurrent (NECC), as well as to boundary current rings and Rossby waves with zonal wavelength of the order of 1000 km. At 44°W the presence of a Rossby wave associated with an anticyclonic circulation led to a strongly enhanced NBC of 65.0 Sv as well as to a combined NECC and Equatorial Undercurrent transport of 52.4 Sv, much stronger than during earlier cruises. While the 1/3°-FLAME model is unable to reproduce details of the vertical distribution of the observed horizontal flow at 44 °W for November 2000 as well as the horizontal distribution of some of the observed permanent current bands, a climatological simulation with the 1/12°-FLAME agrees much better with the observations and provides information on the spreading path between the sections. E.g., the interpretation that the widening in the Antarctic Intermediate Water layer of the westward flowing NBC at 44°W in November was caused by water from the Equatorial Intermediate Current was further supported by the model results

Description: Efficient monitoring of large-scale current systems for climate research requires the development of new techniques to estimate ocean transports. Here, a methodology for continuous estimation of dynamic height profiles and geostrophic currents from moored temperature sensors is presented. The technique is applied to moorings deployed in the Atlantic Deep Western Boundary Current at 26.5°N, off Abaco, the Bahamas (WOCE ACM-1 array). Relative geostrophic currents are referenced using bottom pressure sensors and available shipboard direct velocity (lowered-ADCP) sections over the period of the deployment, to obtain a time series of absolute volume transport. Comparison with direct velocity measurements from a complete array of current meters shows good agreement for the mean transport and its variablity on time scales longer than 10 days, but larger variability in the current meter derived transport at time scales shorter than 10 days. A rigorous error analysis assesses the contributions of various error sources in the geostrophic as well as direct transport estimates. Low-frequency drift of the bottom pressure sensors is found to be the largest error source in the geostrophic transport estimates and recommendations for improvement of the technique and related measurement technologies are made.

Description: We conducted irradiation experiments with riverine, estuarine, and marine water samples to investigate the possibility of photochemical methane (CH4) formation. CH4 photoproduction was undetectable under oxic conditions or in the absence of methyl radical precursors indicating that its photochemical formation is negligible in the present ocean. Significant photochemical CH4 production was observed in the presence of a methyl radical precursor such as acetone under strictly anoxic conditions. Our results indicate an indirect formation mechanism with coloured dissolved organic matter acting as photosensitizer. We suggest that photochemical CH4 formation might have occurred in the anoxic ocean surface layer of the Archean prior to the onset of O2 accumulation in the atmosphere at around 2300 million years ago. Oceanic CH4 photoproduction via methyl radical (CH3) precursors and its subsequent release to the atmosphere may have contributed to high CH4 mixing ratios in the Archean atmosphere.

Description: During the ELISA/MATER experiment floats released at about 600 m depth in the Levantine Intermediate Water layer south of Sardinia in July 1997 have revealed the existence of a coherent eddy, approximately 50 km in diameter and lasting for several months. This anticyclonic eddy was first observed south-west of Sardinia in November 1997 and drifted inside the Algerian Basin during the following months until April 1998. This eddy contained Levantine Intermediate Water at intermediate level and seemed to be related to 2 main large scale features: (a) a cyclonic gyre (250 km in diameter and 3–4 months period) located in the Algerian Basin and (b) a boundary current located along the continental slope south and west of Sardinia and originating from the Sardinia–Tunisia channel. We will first describe the “Sardinian” eddy, from a kinematical point of view, and the Algerian Gyre and second, give some insights about the eddy origin and its importance for LIW large scale spreading in the Western Mediterranean Sea.

Description: The three elongated Desertas Islands form the top of a 60-km-long NW–SE-striking submarine ridge southeast of Madeira (NE Atlantic). The alignment of eruptive centres and parallel dyke swarms indicates that the islands represent a deeply eroded volcanic rift zone. Detailed field studies combined with 40Ar/39Ar age determinations and geochemical analyses reveal the internal structure and evolution of this rift, which may serve as a type example of North Atlantic rift zones. The northern rift end is composed mainly of lava flows up to several meter thickness and few scoria. The central part is characterised by a 100- to 200-m-thick basal sequence of tuff as a result of explosive eruptions due to magma–sea water interaction during the early subaerial stage. These layers are overlain by subhorizontal lava flows reflecting the change from dominantly explosive to more effusive volcanism during island growth. The southern part is dominated by a basal tuff sequence, scoria and cinder cones, minor lava flows and sills up to 30 m in thickness. In general, bomb- and scoria-rich deposits, dykes and sills increase in frequency towards the south. In contrast to rift systems of Hawaiian volcanoes such as Kilauea, we did not find any volcanological or petrological indication of a central caldera underlain by a shallow magma reservoir feeding the rift. 40Ar/39Ar ages show that subaerial Desertas volcanism lasted from 〉5.1 to 1.9 Ma overlapping with the shield-building phases of Madeira island. Desertas lavas show no temporal or spatial variation in chemistry, except for samples from the top of the islands, erupted between ∼3.4 and 2 Ma, which are strongly REE and Y enriched. We suggest that the Desertas ridge represents a discrete volcano that became interconnected with Madeira by growth to the north–northeast. Major volcanic centres may have been located at the southern end of the ridge and/or near its central part. A conceivable explanation for the formation of the elongated Desertas rift is a local gravitative stress field causing preferred extension between the Madeira and Desertas edifices as they progressively overlapped. Our model thus emphasises the importance of edifice amalgamation and gravitative stress in the evolution of large volcanoes and their rift zones. The initiation of Desertas volcanism could be the result of a weak pulsating mantle plume and irregular motion of the African plate, combined with flexural stresses within the lithosphere due to the loads of Madeira and Porto Santo islands. Cessation of volcanism coincides with the exclusive occurrence of Y- and REE-enriched lavas that may be related to sediment assimilation. Our results indicate that models for Hawaiian rifts cannot necessarily be transferred to hotspot volcanoes associated with weak plumes and/or irregular plate motion.

Description: The speciation of strongly chelated iron during the 22-day course of an iron enrichment experiment in the Atlantic sector of the Southern Ocean deviates strongly from ambient natural waters. Three iron additions (ferrous sulfate solution) were conducted, resulting in elevated dissolved iron concentrations (Nishioka, J., Takeda, S., de Baar, H.J.W., Croot, P.L., Boye, M., Laan, P., Timmermans, K.R., in press. Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean. Marine Chemistry.) and significant Fe(II) levels (Croot, P.L., Laan, P., Nishioka, J., Strass, V., Cisewski, B., Boye, M., Timmermans, K.R., Bellerby, R.G., Goldson, L., Nightingale, P., de Baar, H.J.W., in press. Spatial and Temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment. Marine Chemistry.). Repeated vertical profiles for dissolved (filtrate 〈 0.2 μm) Fe(III)-binding ligands indicated a production of chelators in the upper water column induced by iron fertilizations. Abiotic processes (chemical reactions) and an inductive biologically mediated mechanism were the likely sources of the dissolved ligands which existed either as inorganic amorphous phases and/or as strong organic chelators. Discrete analysis on ultra-filtered samples (〈 200 kDa) suggested that the produced ligands would be principally colloidal in size (〉 200 kDa–〈 0.2 μm), as opposed to the soluble fraction (〈 200 kDa) which dominated prior to the iron infusions. Yet these colloidal ligands would exist in a more transient nature than soluble ligands which may have a longer residence time. The production of dissolved Fe-chelators was generally smaller than the overall increase in dissolved iron in the surface infused mixed layer, leaving a fraction (about 13–40%) of dissolved Fe not bound by these dissolved Fe-chelators. It is suggested that this fraction would be inorganic colloids. The unexpected persistence of such high inorganic colloids concentrations above inorganic Fe-solubility limits illustrates the peculiar features of the chemical iron cycling in these waters. Obviously, the artificial about hundred-fold increase of overall Fe levels by addition of dissolved inorganic Fe(II) ions yields a major disruption of the natural physical–chemical abundances and reactivity of Fe in seawater. Hence the ensuing responses of the plankton ecosystem, while in itself significant, are not necessarily representative for a natural enrichment, for example by dry or wet deposition of aeolian dust. Ultimately, the temporal changes of the Fe(III)-binding ligand and iron concentrations were dominated by the mixing events that occurred during EISENEX, with storms leading to more than an order of magnitude dilution of the dissolved ligands and iron concentrations. This had strongest impact on the colloidal size class (〉 200 kDa–〈 0.2 μm) where a dramatic decrease of both the colloidal ligand and the colloidal iron levels (Nishioka, J., Takeda, S., de Baar, H.J.W., Croot, P.L., Boye, M., Laan, P., Timmermans, K.R., in press. Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean. Marine Chemistry.) was observed.

Description: Fluid flow at cold vent sites is usually driven by the ascent of overpressured fluids from subsurface reservoirs. Porosity changes in surface sediments due to precipitation and dissolution of authigenic carbonates affects fluid flow and biogeochemical turnover. From observations, it is known that carbonate precipitates often occur in distinct layers in high concentrations, surrounded by layers with low carbonate content. Using a non-steady state model, we simulate aragonite and calcite precipitation and dissolution in a 2-m long sediment column, located under a bacterial mat at Hydrate Ridge, Cascadia accretionary margin. Assuming a constant pressure gradient over 7000 years, fluid flow, anaerobic oxidation of methane (AOM) rates, and carbonate precipitation and dissolution rates show strong oscillations evoked by changes in permeability and fluid flow over time. The porosity reaches values below 0.35 in the carbonate layers that reduce the fluid flow velocity from an initial value of 30 cm a−1 to a minimum value of about 2 cm a−1. These significant changes in the fluid flow system displace the depth of sulfate penetration. The simulation predicts cycles of carbonate crust formation and dissolution with a duration of 2000–2700 years resulting in several distinct carbonate layers. During periods of high fluid flow, AOM reaches rates over 1000 μmol cm−1 a−1 and methane fluxes out of the sediment reach 200 μmol cm−1 a−1. During periods of low fluid flow, AOM is about 450 μmol cm−1 a−1 and the methane flux into the bottom water vanishes completely. The oscillations are dampened so that fluid flow and biogeochemical turnover slowly approach steady state after about 7000 years towards the end of the simulation period, showing a 1-m-thick area at the surface with carbonate concentrations of about 25 wt.%. Flow oscillations may also impact the colonization of chemoautotrophic larva and bacteria in and on the sediment. The frequency of precipitation–dissolution cycles of 2000–2700 years is long enough for vent biota to react to changes in the sediments, for example explaining the occurrence of buried Calyptogena and Acharax mussel shells at former vent sites that are not presently active. The evaluation of side scan sonar data reveals large areas of cemented sediments and carbonate pavements north of the investigated site. The situation found in the investigated core may be characterized as intermediate stage of carbonate cementation. This ongoing process will also form a solid carbonate pavement at this site in the future.

Description: An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone and fertilized a patch of water within an eddy of the Antarctic Circumpolar Current (EisenEx, Nov. 2000). During the experiment, a physical speciation technique was used for iron analysis in order to understand the changes in iron distribution and size-fractionations, including soluble Fe (〈200 kDa), colloidal Fe (200 kDa–0.2 μm) and labile particle Fe (〉0.2 μm), throughout the development of the phytoplankton bloom. Prior to the first infusion of iron, dissolved (〈0.2 μm) iron concentrations in the ambient surface seawater were extremely low (0.06±0.015 nM) with colloidal iron being a minor fraction. For the iron addition, an acidified FeSO4 solution was released three times over a 23-day period to the eddy. High levels of dissolved iron concentrations (2.0±1.1 nM) were measured in the surface water until 4 days after the first iron infusion. After every iron infusion, when high iron concentrations were observed before storm events, there was a significant correlation between colloidal and dissolved iron concentrations ([Colloidal Fe]=0.7627[Dissolved Fe]+0.0519, R2=0.9346). These results indicate that a roughly constant proportion of colloidal vs. dissolved iron was observed after iron infusion (∼76%). Storm events caused a significant decrease in iron concentrations (〈0.61 nM in dissolved iron) and changed the proportions of the three iron size-fractions (soluble, colloidal and labile particle). The changes in each iron size-fraction indicate that colloidal iron was eliminated from surface mixed layer more easily than particulate and soluble fractions. Therefore, particle and soluble iron efficiently remain in the mixed layer, probably due to the presence of suspended particles and naturally dissolved organic ligands. Our data suggest that iron removal through colloidal aggregation during phytoplankton bloom should be considered in the oceanic iron cycle.

Description: Nitrogen fixation is one of the important biochemical pathways that play a role in controlling the oceanic nitrogen inventory. Here we review nitrogen fixation in the ocean, with a particular emphasis on Trichodesmium, one of the dominant marine diazotrophs. Distribution data for diazotrophs are scarce, except in specific regions where Trichodesmium is known to bloom. Although some regions are clearly under-sampled, Trichodesmium can generally be found in tropical regions where temperature is at least 20 °C, except in the North Atlantic, where drift to higher latitudes is possible via the Gulf Stream. Likewise, biomass estimates are problematic because of the colony-forming habit of this organism. Trichodesmium grows slowly with reported maximum growth rates of approximately 0.14 d-1. Studies of the photosynthetic physiology indicate that Trichodesmium can tolerate high light intensity with Ik and Ic values of ∼300 and ∼140 μmole photons m−2 s−1, respectively. Review of the elemental composition of Trichodesmium indicates that the C:N molar ratio of 6.3:1 does not depart significantly from the predicted Redfield stoichiometry of 6.6:1. Overall, measured N:P ratios from the field and the laboratory were around 50, a significant departure from the Redfield stoichiometry of 16:1. Whether this indicates phosphorus limitation is not clear at present. The iron requirements of diazotrophs in general and of Trichodesmium in particular have been the subject of debate, but some recent laboratory studies have converged on Fe:C (μmole:mole) of approximately 50 at 70% of the maximum growth rates (μmax) to 250 at μmax for this species. There is a noticeable lack of information on growth rate as a function of phosphorus and fixed nitrogen sources. Although Trichodesmium is a non-heterocystous cyanobacterium, carbon and nitrogen fixation co-occur during the light period, indicating that light energy is required for both of these processes. This is likely to be achieved through cellular differentiation of the trichomes and a tight control of the temporal expression of many biochemical pathways. A summary table presents a set of values for the initial parameterisation of parameters relevant to the incorporation of nitrogen fixation in biological and biogeochemical models

Description: Microsporidia are intracellular eukaryotic parasites that can infect a wide range of animal hosts with several genera causing opportunistic infections in immunodeficient patients. Their spore wall and their unique extrusion apparatus, which has the form of a long polar tube, confer resistance of these parasites against the environment and during host-cell invasion. In contrast to parasites of vertebrates, the spore-wall and polar-tube proteins of many microsporidia species still remain to be characterized, even though a great number of microsporidia infect invertebrates. Here, we have identified one spore-wall protein and three polar-tube proteins of the microsporidia Paranosema grylli that infects the cricket Gryllus bimaculatus. Incubation of intact spores with an alkaline–saline solution resulted in the selective extraction of a major 40 kDa protein. A wash of the discharged (or destroyed) spores with SDS and the following solubilization of their polar tubes with 50–75% 2-mercaptoethanol extracted a major protein of ca. 56 kDa. When the polar tubes were solubilized in the presence of SDS, two additional proteins of 46 and 34 kDa were extracted. Antibodies specific for these extracted proteins were generated and isolated by incubation of immune sera with the protein bands that had been transferred to nitrocellulose. Western blotting demonstrated the cross-reactivity of the anti-p46 and anti-p34 antibodies. Immuno-electron microscopy with the anti-p40 antibody revealed specific decoration of the microsporidia exospore. The 56, 46 and 34 kDa proteins were characterized as polar-tube components due to the clear antibody labeling of the polar filament.

Description: The BABEL profiles B, C, 1–7 form a 1200 km long nearly continuous cross-section through the Svecofennides. The near-vertical marine reflection profiles display a wide range of crustal structures that can be associated with both the accretionary Svecofennian orogeny (1.96–1.75 Ga) and the following Subjotnian and Jotnian rift-stages (1.65–1.11 Ga). The Svecofennian accretionary orogeny took place when a number of micro-plates with island arc affinities and surface expression of a large archipelago accreted to the continental Karelian plate. Some of the accreting terranes seem to have had older cores that have acted as crustal indentors during the collision. BABEL profiles 3 and 4 image a series of collisional terrane boundaries between Karelian continental margin, Savo arc (SA) and Central-Finland arc (CFA). In the north, the Karelian margin has been both over- and underthrust by the Savo arc. CFA comprises a folded thrust package on top of a continental nucleus and the Savo arc. The associated subduction zone and accretionary prism are interpreted to lie to the south, underneath the Bothnian basin area, where prominent NE-dipping, lower to middle crustal reflections are found along BABEL profiles 1 and 4. An oblique collision of the Central Finland arc and the continent resulted in the development of the strike-slip fault on the young, hot Savo arc. BABEL profiles 1, 6, 7 and C image the internal architecture of the Southern and Central Finland arcs. The unusually thick crust (55–60 km) hosts unreflective, high density, mafic intrusions acting as a crustal indentor. A highly reflective antiform structure developed on the southern side of it. Southern Finland arc complex (SFA) is an imbrication structure comprising stacked slices of arc-related crust on an older continental nucleus, Bergslagen nucleus. Prior to the collision, the SFA suffered from gravitational collapse during which the crust was thinned. Profile B images the architecture of the Central and Southern Swedish Svecofennides. The Sörmland terrane (SöB) is interpreted as the accretionary prism of the Southern Finland arc squeezed between the Svecofennian collage in the north and the advancing continent to the south. The southern continent/island arc is characterised by NE dipping crustal reflections and Moho offsets as well as step-wise increasing thickness of the crust. After the final collision, large volumes of mantle-derived material intruded the crust as large mushroom-shaped plutons. They are interpreted as the heat source for the TIB magmatism in southern and western Scandinavia.

Description: Diatoms are a major component of phytoplankton community. They tend to dominate under natural high-nutrient concentrations, as well as during artificial Fe fertilisation experiments. They are main players in the biogeochemical cycle of carbon (C), as they can account for 40% of the total primary production in the Ocean and dominate export production, as well as in the biogeochemical cycles of the other macro-nutrients, nitrogen (N), phosphorus (P), and silicon (Si). Another important nutrient is Fe, which was shown to have a direct or indirect effect on nearly all the biogeochemical parameters of diatoms. In the present paper, an inventory is made of the growth, physiology and fate of many diatom species, including maximum growth rate, photosynthetic parameters (maximum specific rate of photosynthesis, photosynthetic efficiency and light adaptation parameter), nutrient limitation (half-saturation constant for growth/uptake), cellular elemental ratios, and loss terms (sinking rates, autolysis rates and grazing rates). This is a first step for improvement of the parameterisation of physiologically based phytoplankton growth and global 3D carbon models. This review is a synthesis of a large number of published laboratory experiments using monospecific cultures as well as field data. Our compilation confirms that size is an important factor explaining variations of biogeochemical parameters of diatoms (e.g. maximum growth rate, photosynthesis parameters, half-saturation constants, sinking rate, and grazing). Some variations of elemental ratios can be explained by adaptation of intracellular requirements or storage of Fe, and P, for instance. The important loss processes of diatoms pointed out by this synthesis are (i) sinking, as single cells as well as through aggregation which generally greatly increases sinking rate, (ii) cell autolysis, which can significantly reduce net growth rates, especially under nutrient limitation when gross growth rates are low, and (iii) grazing by both meso- and micro-zooplankton. This review also defines gaps concerning our knowledge on some important points. For example, we need to better know which iron species is available for phytoplankton, as well as the impact of Fe on the variation of the elemental ratios, especially in terms of assimilation and regeneration of C and N. A better quantification of prey selection by microzooplankton and mesozooplankton in natural environments is also needed, including preference for the various phytoplankton and zooplankton species as well as for aggregates and faecal pellets.

Description: The accumulation of lithium by microorganisms was examined. Among the 70 strains of the 63 species tested (20 bacteria, 18 actinomycetes, 18 fungi, and 14 yeasts), a high lithium accumulating ability was exhibited by strains of the bacteria, Arthrobacter nicotianae and Brevibacterium helovolum. Lithium accumulation by A. nicotianae cells was strongly affected by the pH of the solution. The amount of accumulated lithium was maximum at pH 6. Cells immobilized with polyacrylamide gel also adsorbed lithium. They could be reused during repeated adsorptions, and adsorbed 548 micromol of lithium/g dry wt. cells. The adsorbed lithium was quantitatively and easily desorbed with 1 M hydrochloric acid using a column system.

Description: The Tehuantepec Ridge is one of the most prominent lithospheric structures of the Cocos Plate, yet its tectonic evolution hasremained poorly constrained until now. Calculated ocean floor ages and spreading rates, morphostructural analysis of the ridgeand the surrounding ocean floor are used to infer the tectonic evolution and pattern of the Tehuantepec Ridge and associatedstructures. The ocean floor age estimates south of the Tehuantepec Ridge suggest an age of ~26 Ma at the Middle Americatrench. A mean age difference across the Tehuantepec Ridge of ~7 Ma suggests that the Tehuantepec Ridge would be formed asa long transform fault on the Guadalupe plate, prior to 15 Ma.The full-spreading rate estimates show that there might be a differential full-spreading rate across the transform faultbetween 15 and 5 Ma, when the oceanic plate just south of Clipperton Fracture Zone was decelerating between 15 and 10 Ma,then accelerating for the next 5 Ma. We propose a model in which between 13 and 8 Ma temporarily transpressionalintratransform-spreading centers would have been existing as a consequence of the East Pacific Rise onset with an angle of~108clockwise with respect to the ceased Mathematician ridge. Our model estimates indicate that between 21 and 15 Ma aprominent pseudofault was formed south of the Tehuantepec Ridge due to an unstable offset on the Mathematician ridge thatmigrated northward. The Tehuantepec Ridge and the pseudofault trace bound a deeper oceanic basin than the surrounding area,with no corresponding anomalous depth on the western side of the East Pacific Rise. The complete absence of a pseudofaulttrace and a deeper oceanic basin on the western side of the East Pacific Rise, as well as the spreading rate changes, suggest theexistence of a microplate embedded into the Cocos Plate just south of the Tehuantepec Ridge. Also, the asymmetric and sharpmorphology of the Tehuantepec Ridge suggests that it may be the expression of a major transpressional structure along theformer transform fault on the Guadalupe plate 15–20 Ma ago.

Description: Dinoflagellates are an important component of the extant eukaryotic plankton. Their organic-walled, hypnozygotic cysts (dinocysts) provide a rich, albeit incomplete, history of the group in ancient sediments. Building on pioneering studies of the late 1970s and 1980s, recent drilling in the Southern Ocean has provided a wealth of new dinocyst data spanning the entire Paleogene. Such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of Paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts. Because dinocysts notably exhibit high abundances in neritic settings, dinocyst-based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera, coccolithophorids, diatoms and radiolaria. By presenting case-studies from around the globe, this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the Paleogene (65–25 Ma). Representing Earth's greenhouse–icehouse transition, this episode holds the key to the understanding of extreme transient climatic change. We discuss the potential of dinocysts for the reconstruction of Paleogene sea-surface productivity, temperature, salinity, stratification and paleo-oxygenation along with their application in sequence stratigraphy, oceanic circulation and general watermass reconstructions.

Description: Geochemical and petrographical studies of lavas and ignimbrites from the Quaternary Nisyros–Yali volcanic system in the easternmost part of the Hellenic arc (Greece) reveal insight into magma generating processes. A compositional gap between 61 and 68 wt.% SiO2 is recognized that coincides with the stratigraphic distinction between pre-caldera and post-caldera volcanic units. Trace element systematics support the subdivision of Nisyros and Yali volcanic units into two distinct suites of rocks. The variation of Nd and Hf present day isotope data and the fact that they are distinct from the isotope compositions of MORB rule out an origin by pure differentiation and require assimilation of a crustal component. Lead isotope ratios of Nisyros and Yali volcanic rocks support mixing of mantle material with a lower crust equivalent. However, 87Sr/86Sr ratios of 0.7036–0.7048 are incompatible with a simple binary mixing scenario and give low depleted mantle extraction ages (〈0.1 Ga), in contrast with Pb model ages of 0.3 Ga and Hf and Nd model ages of ca. 0.8 Ga. The budget of fluid-mobile elements Sr and Pb is likely to be dominated by abundant hydrous fluids characterised by mantle-like Sr isotope ratios. Late stage fluids probably were enriched in CO2, needed to explain the high Th concentrations. The occurrence of hydrated minerals (e.g., amphibole) in the first post-caldera unit with the lowermost 87Sr/86Sr ratio of 0.7036±2 can be interpreted as the result of the increased water activity in the source. The presence of two different plagioclase phenocryst generations in the first lava subsequent to the caldera-causing event is indicative for a longer storage time of this magma at a shallower level. A model capable of explaining these observations involves three evolutionary stages. First stage, assimilation of lower crustal material by a primitive magma of mantle origin (as modelled by Nd–Hf isotope systematics). This stage ended by an interruption in replenishment that led to an increase of crystallization and, hence, an increase in viscosity, suppressing eruption. During this time gap, differentiation by fractional crystallization led to enrichment of incompatible species, especially aqueous fluids, to silica depolymerisation and to a decrease in viscosity, finally enabling eruption again in the third stage.

Description: Measuring and modeling the surface charge of clays, and more especially smectites, has become an important issue in the use of bentonites as a waste confinement material aimed at retarding migration of water and solutes. Therefore, many studies of the acid–base properties of montmorillonite have appeared recently in the literature, following older studies principally devoted to cation exchange. It is striking that beyond the consensus about the complex nature of the surface charge of clays, there are many discrepancies, especially concerning the dissociable charge, that prevents intercomparison among the published data. However, a general trend is observed regarding the absence of common intersection point on raw titration curves at different ionic strengths. Analysis of the literature shows that these discrepancies originate from the experimental procedures for the preparation of the clays and for the quantification of their surface charge. The present work is an attempt to understand how these procedures can impact the final results. Three critical operations can be identified as having significant effects on the surface properties of the studied clays. The first one is the preparation of purified clay from the raw material: the use of acid or chelation treatments, and the repeated washings in deionized water result in partial dissolution of the clays. Then storage of the purified clay in dry or wet conditions strongly influences the equilibria in the subsequent experiments respectively by precipitation or enhanced dissolution. The third critical operation is the quantification of the surface charge by potentiometric titration, which requires the use of strong acids and bases. As a consequence, besides dissociation of surface sites, many secondary titrant consuming reactions were described in the literature, such as cation exchange, dissolution, hydrolysis, or precipitation. The cumulated effects make it difficult to derive proper dissociation constants, and to build adequate models. The inadequation of the classical surface complexation models to describe the acid–base behavior of clays is illustrated by the electrokinetic behavior of smectites, which is independent from the pH and the ionic strength. Therefore, there is still a need on one hand for accurate data recorded in controlled conditions, and on the other hand for new models taking into account the complex nature of the charge of clays.

Description: This paper presents seasonal variations of the wind characteristics and wind turbine characteristics in the regions around Elazig, namely Maden, Agin and Keban. Mean wind speed data in measured hourly time series format is statistically analyzed for the six year period 1998–2003. The probability density distributions are derived from the time series data and their distributional parameters are identified. Two probability density functions are fitted to the measured probability distributions on a seasonal basis. The wind energy characteristics of all the regions is studied based on the Weibull and Rayleigh distributions. Energy calculations and capacity factors for the wind turbine characteristics were determined for wind machines of different sizes between 300 and 2300 kW. It was found that Maden is the best region, among the regions analyzed, for wind characteristics and wind turbine characteristics.

Description: Arabidopsis genes encoding enzymes for each of the eight steps in l-arginine (Arg) synthesis were identified, based upon sequence homologies with orthologs from other organisms. Except for N-acetylglutamate synthase (NAGS; EC 2.3.1.1), which is encoded by two genes, all remaining enzymes are encoded by single genes. Targeting predictions for these enzymes, based upon their deduced sequences, and subcellular fractionation studies, suggest that most enzymes of Arg synthesis reside within the plastid. Synthesis of the l-ornthine (Orn) intermediate in this pathway from l-glutamate occurs as a series of acetylated intermediates, as in most other organisms. An N-acetylornithine:glutamate acetyltransferase (NAOGAcT; EC 2.3.1.35) facilitates recycling of the acetyl moiety during Orn formation (cyclic pathway). A putative N-acetylornithine deacetylase (NAOD; EC 3.5.1.16), which participates in the “linear” pathway for Orn synthesis in some organisms, was also identified. Previous biochemical studies have indicated that allosteric regulation of the first and, especially, the second steps in Orn synthesis (NAGS; N-acetylglutamate kinase (NAGK), EC 2.7.2.8) by the Arg end-product are the major sites of metabolic control of the pathway in organisms using the cyclic pathway. Gene expression profiling for pathway enzymes further suggests that NAGS, NAGK, NAOGAcT and NAOD are coordinately regulated in response to changes in Arg demand during plant growth and development. Synthesis of Arg from Orn is further coordinated with pyrimidine nucleotide synthesis, at the level of allocation of the common carbamoyl-P intermediate.