ALBERT

Description: Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) is described from southern and western Japan and is characterized by the following combination of features: (i) the large, fragile, easily torn thalli, which are 30–55 μm thick in the upper and middle regions and often have microscopic marginal teeth; (ii) the production of zoids in the upper marginal region; (iii) a regular alternation of dioecious gametophytes and a sporophyte; (iv) the production of free-floating thalli from torn-off attached thalli, which reproduce vegetatively by fragmentation and form green tides in summer to autumn; (v) disorderly arranged cells that are polygonal or quadrangular in the upper and middle regions; and (vi) the chloroplast covering the outer face of cell, with 1–3 pyrenoids. Ulva ohnoi differs from U. armohcana Dion et al., U. fasciata Delile, U. reticulata Forsskal, U. scandinavica Eliding and U. spiulosaOkamura et Segawa, which all possess microscopic marginal serrations, in thallus shape, cell shape or life history pattern. It is also distinguished from morphologically similar species by sequences of the nuclear encoded internal transcribed spacers and the 5.8S ribosomal RNA gene and the plastid encoded large subunit of ribulose-l,5-bisphosphate carboxylase/oxgenase gene. Furthermore, crossing tests demonstrate that there is a reproductive boundary between U. ohnoi and the most closely related species, U. fasciata and U. reticulata.

Description: Measurements of the gas vesicle space in steady‐state light or phosphate‐limited cultures of Aphanizomenon flos‐aquae Ralfs, strain 7905 showed that gas vesicle content decreased as energy‐limited growth rate increased hut was the same at several phosphate‐limited growth rates. Upon a decrease in growth irradiance, gas vesicle content did increase in phosphate‐limited cultures, hut the cultures remained nonbuoyant as long as P was limiting. Buoyant, energy‐limited cultures lost their buoyancy in less than 2 h when exposed to higher irradiances. The primary mechanism for buoyancy loss was the accumulation of polysaccharide as ballast. Collapse of gas vesicles by turgor pressure played a minor role in the loss of buoyancy. When cultures were exposed to higher irradiances, cells continued to synthesize gas vesicles at the same rate as before the shift for at least 1 generation time. The amount of ballast required to make individual filaments in the population sink varied 4‐fold. This variation appears to be due to differences in gas vesicle content among individual filaments.

Description: The dissection of Heterorotula sponges collected in an area of geothermal activity at 126–145 m depth on the floor of Lake Taupo (de Rondeet al., 2002) revealed a dense population of associated Enchytraeidae. They represent three species of Marionina, two of which known but exotic (the Palaearctic M. ripariaBretscher, 1899 and the Chinese M. seminudaXie and Rota, 2001), and one new to science, M. spongicola sp. n. This is the first report of an ecological association between enchytraeids and poriferans in the lake profundal zone. The possible nature of such relationship (casual contact for feeding or dwelling for food and shelter) is discussed.

Description: In this article we review the indirect interactions prevailing in littoral communities and compare their importance to direct trophic interactions. We focus on the interaction between benthic algae and their herbivorous consumers, i. e. invertebrate grazers and herbivorous fish. In addition to the effects of grazers on periphyton biomass and production, we categorise and describe the types of indirect interactions observed and we present a quantitative meta-analysis to compare the effect magnitude of indirect and direct effects. Our review shows that herbivore-plant interactions comprise considerable complexity beyond consumption. We identify and review three different indirect interactions, which play important roles for periphyton-grazer interactions in benthic food webs. These are keystone predation, trophic cascading and habitat facilitation. Direct negative effects were stronger than indirect positive effect, because grazing leads in almost all studies to a decrease in algal biomass. We found positive effects of grazing on algal nutrient content, biomass-specific productivity and evenness. We found negative overall effects on species richness and area-specific productivity. Moreover, spatial heterogeneity was on average increased by grazing. The magnitudes of direct and indirect effects were often correlated

Description: While consumer species diversity is known to influence the capture of limited resources, little is known about how prey diversity impacts the transfer of energy and matter among trophic levels. Here, we perform a meta-analysis of experiments that have examined the impact of grazers on the biomass of periphytic algae to test the hypothesis that the magnitude of consumer (grazer) effects on prey (algae) depends on the species diversity of the prey assemblage. The analysis reveals that consumer effects tend to decrease as the diversity of a prey assemblage increases. This trend is robust for several different, yet complementary indices of grazer effect size and algal diversity. The trend also remains significant after statistically controlling for a variety of factors that can covary with prey diversity among studies. We discuss several possible mechanisms for the documented pattern, such as diversity enhancing the probability of inedibility and of positive interactions.

Description: Horizontal gene transfer is an important mechanism for the evolution of microbial genomes. Pathogenicity islands — mobile genetic elements that contribute to rapid changes in virulence potential — are known to have contributed to genome evolution by horizontal gene transfer in many bacterial pathogens. Increasing evidence indicates that equivalent elements in non-pathogenic species — genomic islands — are important in the evolution of these bacteria, influencing traits such as antibiotic resistance, symbiosis and fitness, and adaptation in general. This review discusses the recent lessons that have been learned from pathogenicity islands in pathogenic microorganisms and how they apply to the role of genomic islands in commensal, symbiotic and environmental bacteria.

Description: The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago1. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10–40) times 106 m3 s-1 of water2, 3, 4, 5, transporting North Atlantic Deep Water—from the overflow regions between Greenland and Scotland and from the Labrador Sea—into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8° S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.

Description: The Alhambra (14th century AD) in Granada (southeast Spain) is built at the summit of a Pliocene to Lower Pleistocene conglomeratic formation. Tens of small-scale normal faults crop out along the northern hillslope of the Alhambra, which have a N130–N150°E strike, dipping 65–75° mostly to the southwest. These are closely spaced faults (approximately 5–30 m) with centimetre to several metre displacements. Several topographic steps in this area coincide with hectometre- to kilometre-scale faults with the same kinematics as the small-scale ones. Some of these faults appear to be active and related to the present seismicity detected in this region, and associated with the cracks and other damage observed in the Alhambra. Several focal mechanisms calculated in this study are in accordance with the dominant NW–SE orientated normal faults. We interpret that the topographic steps of these faults are a consequence of repeated earthquakes during the past 800 ka. The last large earthquake of approximately 5.1 magnitude in this area occurred in 1431, destroying the Alixares Palace, the Arabian fence and part of the Alhambra wall. We consider the seismic risk associated with these faults to be moderate, as the displacement is partitioned into several hectometre- to kilometre-scale faults.

Description: Notations for Cd stable isotope compositions and the use of reference materials are discussed. It is proposed that Cd stable isotope data should be reported as variations of the 114Cd/110Cd ratio/ using either the δ114/110Cd or ε114/110Cd notations. Future publications should report results for BAM-1012 Cd, the only currently available international Cd isotope reference material. It is also recommended that “Münster Cd” and a range of specified geological reference materials are used as additional reference materials. The final choice of a primary “zero-delta” reference standard remains the most important outstanding question.

Description: The region of north Iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts. In this study we present total carbonate and δ18O records of benthic and planktic Foraminifera from nine sediment cores from the North Iceland Shelf. The results of this work indicate that the deglaciation of the Vestfirdir Peninsula was completed by 10 200 cal. yr BP. The 8200 cal. yr BP cold event is present only as a minor isotopic event, and seems not to have had much of a cooling effect on the bottom waters of the northwest Iceland shelf. The Holocene maximum warmth, attributed to a stronger North Icelandic Irminger Current, occurred between ca. 7800 and 6200 cal. yr BP. Over the past 4500 cal. yr BP a general cooling trend has occurred on the North Iceland Shelf, and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf. Relatively cooler waters were present at 4200–4000 cal. yr BP, 3200–2900 cal. yr BP, 2500–2350 cal. yr BP and 600–200 cal. yr BP, whereas relatively warmer waters were present on the shelf at 3750–3450 cal. yr BP, 2800–2600 cal. yr BP and 1700–1000 cal. yr BP.

Description: 1. Density gradients of cladocerans and copepods were generated in an enclosure experiment to compare the impact on the plankton of a filter feeder (Daphnia hyalina × galeata) with that of more selective feeders (calanoid and cyclopoid copepods). The experiment was conducted in situ over 25 days during spring in a mesotrophic lake, Schöhsee, Germany. 2. The plankton community was monitored regularly. Daphniids were able to graze on the phytoplankton present, which mainly consisted of small (〈1000 μm3) species, whereas copepods did not show any impact on algae. 3. At the end of the experiment, Daphnia and remaining cyclopoid copepods were harvested and sorted manually, prior to analyses for stable isotopes of carbon and nitrogen. Daphniids from mesocosms stocked purely with differing densities of Daphnia showed little variability in stable isotope values, whereas those that thrived in enclosure bags together with copepods exhibited lower δ13C values. 4. The change in Daphniaδ13C indicates a change of food sources, modified by the presence of the copepods: the higher the mean abundance of copepods in the enclosures, the more 13C-depleted the daphniids. Increasing abundance of high nucleic acid (HNA) bacteria in the copepod bags may account for the trend in Daphniaδ13C via increased grazing on the bacteria themselves, or via grazing on phytoplankton utilising isotopically light CO2 from respiratory release. 5. Cyclopoid copepod stable isotope signatures were related to Daphnia and copepod abundances in copepod bags, suggesting that cyclopoids preyed on the available zooplankton.

Description: Over the last two decades numerous studies have investigated the structure of the west Iberia continental margin, a non-volcanic margin characterized by a broad continent–ocean transition (COT). However, the nature and structure of the crust of the segment of the margin off SW Iberia is still poorly understood, because of sparse geophysical and geological data coverage. Here we present a 275-km-long multichannel seismic reflection (MCS) profile, line AR01, acquired in E–W direction across the Horseshoe Abyssal Plain, to partially fill the gap of information along the SW Iberia margin. Line AR01 runs across the inferred plate boundary between the Iberian and the African plates during the opening of the Central Atlantic ocean. The boundary separates crust formed during or soon after continental rifting of the SW Iberian margin from normal seafloor spreading oceanic crust of the Central Atlantic ocean. Line AR01 has been processed and pre-stack depth migrated to show the tectonic structure of the crust across the palaeo plate boundary. This boundary is characterized by a 30–40-km-wide zone of large basements highs related to landward-dipping reflections, which penetrate to depths of 13–15 km, and it marks a change in the character of the basement structure and relief from east to west. In this study, we have used pre-stack depth migrated images, the velocity model of line AR01 and magnetic data available in the area to show that the change in basement structure occurs across the fossil plate boundary, separating African oceanic crust of the M series (M21–M16) to the west from the transitional crust of the Iberian margin to the east.

Description: Active seismic investigations along the Pacific margin off Peru were carried out using ocean bottom hydrophones and seismometers. The structure and the P-wave velocities of the obliquely subducting oceanic Nazca Plate and overriding South American Plate from 8°S to 15°S were determined by modelling the wide-angle seismic data combined with the analysis of reflection seismic data. Three detailed cross-sections of the subduction zone of the Peruvian margin and one strike-line across the Lima Basin are presented here. The oceanic crust of the Nazca Plate, with a thin pelagic sediment cover, ranging from 0–200 m, has an average thickness of 6.4 km. At 8°S it thins to 4 km in the area of Trujillo Trough, a graben-like structure. Across the margin, the plate boundary can be traced to 25 km depth. As inferred from the velocity models, a frontal prism exists adjacent to the trench axis and is associated with the steep lower slope. Terrigeneous sediments are proposed to be transported downslope due to gravitational forces and comprise the frontal prism, characterized by low seismic P-wave velocities. The lower slope material accretes against a backstop structure, which is defined by higher seismic P-wave velocities, 3.5–6.0 km s−1. The large variations in surface slope along one transect may reflect basal removal of upper plate material, thus steepening the slope surface. Subduction processes along the Peruvian margin are dominated by tectonic erosion indicated by the large margin taper, the shape and bending of the subducting slab, laterally varying slope angles and the material properties of the overriding continental plate. The erosional mechanisms, frontal and basal erosion, result in the steepening of the slope and consequent slope failure.

Description: A recent meta-analysis indicates that trophic cascades (indirect effects of predators on plants via herbivores) are weak in marine plankton in striking contrast to freshwater plankton (Shurin et al. 2002, Ecol. Lett., 5, 785–791). Here we show that in a marine plankton community consisting of jellyfish, calanoid copepods and algae, jellyfish predation consistently reduced copepods but produced two distinct, opposite responses of algal biomass. Calanoid copepods act as a switch between alternative trophic cascades along food chains of different length and with counteracting effects on algal biomass. Copepods reduced large algae but simultaneously promoted small algae by feeding on ciliates. The net effect of jellyfish on total algal biomass was positive when large algae were initially abundant in the phytoplankton, negative when small algae were dominant, but zero when experiments were analysed in combination. In contrast to marine systems, major pathways of energy flow in Daphnia-dominated freshwater systems are of similar chain length. Thus, differences in the length of alternative, parallel food chains may explain the apparent discrepancy in trophic cascade strength between freshwater and marine planktonic systems.

Description: The climate of the last glacial period was extremely variable, characterized by abrupt warming events in the Northern Hemisphere, accompanied by slower temperature changes in Antarctica and variations of global sea level. It is generally accepted that this millennial-scale climate variability was caused by abrupt changes in the ocean thermohaline circulation. Here we use a coupled ocean–atmosphere–sea ice model to show that freshwater discharge into the North Atlantic Ocean, in addition to a reduction of the thermohaline circulation, has a direct effect on Southern Ocean temperature. The related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical North Atlantic caused by a fast wave-adjustment process. We present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of Greenland and Antarctic temperature changes, the slow changes in Antarctic temperature and its similarity to sea level, as well as a possible time lag of sea level with respect to Antarctic temperature during Marine Isotope Stage 3.

Description: The role of iron in enhancing phytoplankton productivity in high nutrient, low chlorophyll oceanic regions was demonstrated first through iron-addition bioassay experiments1 and subsequently confirmed by large-scale iron fertilization experiments2. Iron supply has been hypothesized to limit nitrogen fixation and hence oceanic primary productivity on geological timescales3, providing an alternative to phosphorus as the ultimate limiting nutrient4. Oceanographic observations have been interpreted both to confirm and refute this hypothesis5, 6, but direct experimental evidence is lacking7. We conducted experiments to test this hypothesis during the Meteor 55 cruise to the tropical North Atlantic. This region is rich in diazotrophs8 and strongly impacted by Saharan dust input9. Here we show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus. Saharan dust addition stimulated nitrogen fixation, presumably by supplying both iron and phosphorus10, 11. Our results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic.

Description: No need to wait for more information: industrialized fishing is already wiping out stocks.

Description: The formation and sinking of biogenic particles mediate vertical mass fluxes and drive elemental cycling in the ocean1. Whereas marine sciences have focused primarily on particle production by phytoplankton growth, particle formation by the assembly of organic macromolecules has almost been neglected2, 3. Here we show, by means of a combined experimental and modelling study, that the formation of polysaccharide particles is an important pathway to convert dissolved into particulate organic carbon during phytoplankton blooms, and can be described in terms of aggregation kinetics. Our findings suggest that aggregation processes in the ocean cascade from the molecular scale up to the size of fast-settling particles, and give new insights into the cycling and export of biogeochemical key elements such as carbon, iron and thorium.

Description: The deposition of atmospheric dust into the ocean has varied considerably over geological time1, 2. Because some of the trace metals contained in dust are essential plant nutrients which can limit phytoplankton growth in parts of the ocean, it has been suggested that variations in dust supply to the surface ocean might influence primary production3, 4. Whereas the role of trace metal availability in photosynthetic carbon fixation has received considerable attention, its effect on biogenic calcification is virtually unknown. The production of both particulate organic carbon and calcium carbonate (CaCO3) drives the ocean's biological carbon pump. The ratio of particulate organic carbon to CaCO3 export, the so-called rain ratio, is one of the factors determining CO2 sequestration in the deep ocean. Here we investigate the influence of the essential trace metals iron and zinc on the prominent CaCO3-producing microalga Emiliania huxleyi. We show that whereas at low iron concentrations growth and calcification are equally reduced, low zinc concentrations result in a de-coupling of the two processes. Despite the reduced growth rate of zinc-limited cells, CaCO3 production rates per cell remain unaffected, thus leading to highly calcified cells. These results suggest that changes in dust deposition can affect biogenic calcification in oceanic regions characterized by trace metal limitation, with possible consequences for CO2 partitioning between the atmosphere and the ocean.

Description: Nonmammalian tooth-bearing vertebrates usually replace their teeth throughout life. Much about how a replacement pattern is generated has been learned from zebrafish. However, to understand general mechanisms of tooth replacement, advantage can be taken from studying other, “nonmodel” species. We have mapped the patterns of tooth replacement in widely divergent aquatic osteichthyans using 2D charts, in which one axis is time, the other linear spacing along the tooth row. New teeth that are generated simultaneously are considered part of the same odontogenic wave. Using this approach, it appears that a similar, general pattern underlies very distinctive dentitions in distantly related species. A simple shift in spacing of odontogenic waves, or in distance between subsequent tooth positions along a row (or both), can produce dramatically different dentitions between life stages within a species, or between closely related species. Examples will be presented from salmonids, cyprinids, and cichlids. Our observations suggest that lines linking subsequent positions may have more biological significance than replacement waves (usually linking alternate positions), often used to explain the generation of patterns. The presence of a general pattern raises questions about common control mechanisms. There is now increasing evidence, at least for the zebrafish, to support a role for stem cells in continuous tooth renewal and control of replacement patterns.

Description: This contribution aims to report the reflections we had with the scientific community during two international workshops on reference materials for stable isotopes in Davos (2002) and Nice (2003). After evaluating the isotopic homogeneity of some existing reference materials, based on either certificates, literature data or specific inter-laboratory rounds, we confirm these as primary reference materials or propose new ones relative to which stable isotope compositions should be reported. We propose DSM-3 for Mg, NIST SRM 915a for Ca, L-SVEC for Li and NBS28 for Si. Cadmium does not yet have a well identified delta zero material, although three commercial mono-elemental Cd solutions have yielded the same isotopic composition relative to one another. In order to scale the linearity of any mass spectrometer, some secondary reference materials are also proposed: Cambridge-1 solution for Mg, the “Münster-Cd” and JEPPIM Cd solutions for Cd and the “Big Batch” silicate for Si. The team from Nancy propose to prepare a mixed spike solution for Li isotopes. Well-characterised natural samples such as ocean or continental waters, diatoms, sponges, rocks and minerals are needed to validate the entire analytical procedure, particularly to take into account the effect of sample mineralisation and of chemical manipulations for elemental separation prior to analysis.

Description: We present depth images, from portions of profiles that are close to flow-lines, of Cretaceous oceanic crust in the eastern Central Atlantic. Compared with post-stack time migrations, the images illustrate the improvement resulting from the application of pre-stack depth migration. The images document the scale and geometry of normal faulting in oceanic crust formed over 25 Myr at a half-spreading rate of less than 10 mm yr−1, and the variation in extensional style with position within the spreading segment. Away from major fault zones (FZs), most faults are subplanar, dip more than 35°, are associated with moderate basement relief (0.2–1 km relief) and may penetrate to deep crustal levels. These faults could be related to the lifting of the lithosphere out of the median valley to the flanking mountains. Also observed away from FZs are gently dipping to subhorizontal reflections in the upper crust, which resemble detachment faults. In contrast, the inside corner crust is more rugged, with basement highs rising up to 2 km above the intervening basins. This larger-scale topography is associated with a different style of faulting: the depth images reveal gently dipping (〈35°) faults that are rooted in the deep crust and that project to the ridgeward flank of the dome-shaped large basement highs (1–2 km vertical relief). The faults seem to continue as the ridge-facing flank of these highs and some may extend over the crest of the high to breakaways beyond. In this case, the domal highs that form the exhumed footwall to the faults can be described as oceanic core complexes. These controlling faults are up to 20 km long and have a heave of ∼10 km, sufficient to have accommodated up to 50 per cent extension and to have exhumed deep crustal and perhaps even mantle rocks. We suggest that similar faults can explain the structure and lithologies found at megamullion structures (oceanic core complexes) at inside corners near the present-day spreading ridge.

Description: Ecological stoichiometry describes the biochemical constraints of trophic interactions emerging from the different nutrient content and nutrient demand of producers and consumers, respectively. Most research on this topic originates from well-mixed pelagic food webs, whereas the idea has received far less attention in spatially structured habitats. Here, we test how light as well as grazing and nutrient regeneration by consumers affects growth and biomass of benthic primary producers. In the first laboratory experiment, we manipulated grazer presence (two different snail species plus ungrazed control), in the second experiment we factorially combined manipulation of grazer presence and light intensity. We monitored snail and periphyton biomass as well as dissolved and particulate nutrients (nitrogen and phosphorus) over time. Grazers significantly reduced algal biomass in both experiments. Grazers affected periphyton nutrient content depending on the prevailing nutrient limitation and their own body stoichiometry. In the nitrogen (N-) limited first experiment, grazers increased N both in the periphyton and in the water column. The effect was stronger for grazers with lower N-content. In the phosphorus (P-) limited second experiment, grazers increased the P-content of the periphyton, but the grazer with lower N-content had additionally positive effects on algal N. Light reduction did not affect periphyton biomass, but increased chlorophyll-, N- and P-content of the periphyton. These experiments revealed that the indirect effects of grazers on periphyton were bound by stoichiometric constraints of nutrient incorporation and excretion.

Description: Ambient UV radiation has substantially increased during the last decades, but its impact on marine benthic communities is hardly known. The aim of this study was to globally compare and quantify how shallow hard-bottom communities are affected by UV during early succession. Identical field experiments in 10 different coastal regions of both hemispheres produced a consistent but unexpected pattern: (i) UV radiation affected species diversity and community biomass in a very similar manner, (ii) diversity and biomass were reduced to a larger extent by UVA than UVB radiation, (iii) ambient UV levels did not affect the composition of the communities, and (iv) any UV effects disappeared during species succession after 2–3 months. Thus, current levels of UV radiation seem to have small, predictable, and transient effects on shallow marine hard-bottom communities.

Description: The influence of periodic salinity changes was investigated for 42 days under semicontinuous culture conditions with phosphorus limitation using phytoplankton assemblages from Lake Waihola, a tidally influenced shallow lake. To simulate tidal effects on the phytoplankton community, salinity in the cultures was increased in pulses at different intervals (3.5, 7, and 14 days), and these cultures were compared with those that experienced constant freshwater conditions. Salinity pulses significantly affected competition and succession with a major loss in diversity during the first days of the experiment due to the initial pulse that caused a transition from freshwater to brackish conditions in the cultures. After this initial phase, diversity index (H') and species number (Scorr) decreased less rapidly. The loss in H' and Scorr over time was highest under constant freshwater conditions and lowest in the treatment with an interval of 3.5 days between salinity pulses. At the end of the experiment, the combination of initial loss in H' and Scorr and the time course of H' and Scorr resulted in a U‐shaped relation between the interval length of salinity pulses and both H' and Scorrtemp1.txttemp1.txt. Our results indicate that salinity pulses at intervals of a few days tend to promote phytoplankton diversity. If saline intrusions in coastal freshwater systems occur only at spring tides, this will lead to decreases in diversity and species richness.

Description: Ecosystem resistance to a single stressor relies on tolerant species that can compensate for sensitive competitors and maintain ecosystem processes, such as primary production. We hypothesize that resistance to additional stressors depends increasingly on species tolerances being positively correlated (i.e. positive species co-tolerance). Initial exposure to a stressor combined with positive species co-tolerance should reduce the impacts of other stressors, which we term stress-induced community tolerance. In contrast, negative species co-tolerance is expected to result in additional stressors having pronounced additive or synergistic impacts on biologically impoverished functional groups, which we term stress-induced community sensitivity. Therefore, the sign and strength of the correlation between species sensitivities to multiple stressors must be considered when predicting the impacts of global change on ecosystem functioning as mediated by changes in biodiversity.

Description: Recent experiments, mainly in terrestrial environments, have provided evidence of the functional importance of biodiversity to ecosystem processes and properties. Compared to terrestrial systems, aquatic ecosystems are characterised by greater propagule and material exchange, often steeper physical and chemical gradients, more rapid biological processes and, in marine systems, higher metazoan phylogenetic diversity. These characteristics limit the potential to transfer conclusions derived from terrestrial experiments to aquatic ecosystems whilst at the same time provide opportunities for testing the general validity of hypotheses about effects of biodiversity on ecosystem functioning. Here, we focus on a number of unique features of aquatic experimental systems, propose an expansion to the scope of diversity facets to be considered when assessing the functional consequences of changes in biodiversity and outline a hierarchical classification scheme of ecosystem functions and their corresponding response variables. We then briefly highlight some recent controversial and newly emerging issues relating to biodiversity-ecosystem functioning relationships. Based on lessons learnt from previous experimental and theoretical work, we finally present four novel experimental designs to address largely unresolved questions about biodiversity-ecosystem functioning relationships. These include (1) investigating the effects of non-random species loss through the manipulation of the order and magnitude of such loss using dilution experiments; (2) combining factorial manipulation of diversity in interconnected habitat patches to test the additivity of ecosystem functioning between habitats; (3) disentangling the impact of local processes from the effect of ecosystem openness via factorial manipulation of the rate of recruitment and biodiversity within patches and within an available propagule pool; and (4) addressing how non-random species extinction following sequential exposure to different stressors may affect ecosystem functioning. Implementing these kinds of experimental designs in a variety of systems will, we believe, shift the focus of investigations from a species richness-centred approach to a broader consideration of the multifarious aspects of biodiversity that may well be critical to understanding effects of biodiversity changes on overall ecosystem functioning and to identifying some of the potential underlying mechanisms involved.

Description: The isolation and structure elucidation of two new oleanane-type triterpene glycosides, 29-(β-D-glucopyranosyloxy)-2α,3β,23-trihydroxyolean-12-en-28-oic acid (=(2α,3β,4α,29α)-29-(β-D-glucopyranosyloxy)-2,3,23-trihydroxyolean-12-en-28-oic acid; 1) and its C(20)-epimer, 30-(β-D-glucopyranosyloxy)-2α,3β,23-trihydroxyolean-12-en-28-oic acid (=(2α,3β,4α,29β)-29-β-D-glucopyranosyloxy)-2,3,23-trihydroxyolean-12-en-28-oic acid; 2), and a novel nortriterpene glycoside, (17S)-2α,18β,23-trihydroxy-3,19-dioxo-19(18[RIGHTWARDS ARROW]17)- abeo-28-norolean-12-en-25-oic acid β-D-glucopyranosyl ester (=(1R,2S,4aS,4bR,6aR,7R,9R,10aS,10bS)-3,4,4a,4b,5,6,6a,7,8,9,10,10a,10b,11-tetradecahydro-1-hydroxy-7-(hydroxymethyl)-3′,4′,4a,4b,7-pentamethyl-2′,8- dioxospiro[chrysene-2(1H),1′-cyclopentane]-10a-carboxylic acid β-D-glucopyranosyl ester; 3) from Phlomis viscosa (Lamiaceae) are reported. The structures of the compounds were asigned by means of spectroscopic (IR, 1D- and 2D-NMR, and LC-ESI-MS) and chemical (acetylation) methods.

Description: Marine and fisheries scientists are increasingly using metapopulation concepts to better understand and model their focal systems. Consequently, they are considering what defines a metapopulation. One perspective on this question emphasizes the importance of extinction probability in local populations. This view probably stems from the focus on extinction in Levins' original metapopulation model, but places unnecessary emphasis on extinction–recolonization dynamics. Metapopulation models with more complex structure than Levins' patch-occupancy model and its variants allow a broader range of population phenomena to be examined, such as changes in population size, age structure and genetic structure. Analyses along these lines are critical in fisheries science, where presence–absence resolution is far too coarse to understand stock dynamics in a meaningful way. These more detailed investigations can, but need not, aim to assess extinction risk or deal with extinction-prone local populations. Therefore, we emphasize the coupling of spatial scales as the defining feature of metapopulations. It is the degree of demographic connectivity that characterizes metapopulations, with the dynamics of local populations strongly dependent upon local demographic processes, but also influenced by a nontrivial element of external replenishment. Therefore, estimating rates of interpopulation exchange must be a research priority. We contrast metapopulations with other spatially structured populations that differ in the degree of local closure of their component populations. We conclude with consideration of the implications of metapopulation structure for spatially explicit management, particularly the design of marine protected area networks.

Description: The Patagonian longfin squid Loligo gahi undertakes horizontal ontogenetic migrations on the Falkland shelf: juveniles move from spawning grounds located in shallow, inshore waters (20–50 m depths) to feeding grounds near the shelf edge (200–350 m depths). Immature squid feed and grow in these offshore feeding grounds and, upon maturation, migrate back to inshore waters to spawn. The possible influence of environmental factors on L. gahi migrations was investigated using data from oceanographic transects, crossing the region of known L. gahi occurrence. They were made from the inshore waters of East Falkland eastwards to depths of 1250 m on a monthly basis from 1999 to 2001. Four main water types were found in the region: Shelf, Sub-Antarctic Superficial and Antarctic Intermediate water masses, and Transient Zone waters. The inshore spawning grounds occur in the Shelf Water mass, whereas the feeding squid (medium-sized immature and maturing individuals) were associated with the Transient Zone. The 5.5°C isotherm appeared to mark the limit of squid distribution into deeper waters in all seasons. Seasonal changes in water mass characteristics and location were found to be important for seasonal changes in L. gahi migrations on the Falkland shelf.

Description: The reproductive system is described from 15 giant squid Architeuthis sp., collected between 1972 and 2002 in South African waters. Distinctive features of the male reproductive system are the long muscular terminal organ, with elaboration of the anterior end, and modification of the tips of the ventral arms, probably hectocotilization. The spermatophoric organ has a long finishing gland that extends from the base of the gill. The terminal organ is differentiated internally into three distinct parts, involved in the guidance, storage, protection, expulsion and possibly the coating of spermatophores. Length of spermatophores in the terminal organ varied considerably. Several stages of spermatophores were found, from tentative to false to fully formed spermatophores, within a single animal. Distinctive features of the female reproductive system are a mesentery surrounding the main blood vessels of the ovary and attaching the ovary to the dorsal gladius chamber, multiple branching (at least three times) of the genital aorta that supplies the developing oocytes, high potential fecundity (3.5–6.2 ± 106 oocytes), small eggs and short oviducts that suggest intermittent (extended) spawning. Large concentrations and single spermatangia were found in various places in females, indicating non-specific deposition. The transfer of spermatophores is probably rapid, perhaps because of considerable sexual size dimorphism (at maturity, males are much smaller than females). Implants in males are probably self-induced since the majority were found within reach of the terminal organ opening (primarily on the ventral arms in males).

Description: This paper contains a collection of English translations of twenty-one of Hans Ertel's papers on geophysical fluid dynamics. The selected papers were originally published between 1942 and 1970 in either German or Spanish. This collection includes the four classic 1942 papers on vorticity and potential vorticity conservation principles and also papers on generalized conservation relations, hydrodynamic commutation formulas, Clebsch and Weber transformations, and isogons and isotachs in two-dimensional flows.

Description: A proposal is made to standardise the reporting of Ca isotope data to the δ44Ca/40Ca notation (or δ44Ca/42Ca) and to adopt NIST SRM 915a as the reference standard.

Description: Three simple fisheries indicators are presented: (i) percentage of mature fish in catch, with 100% as target; (ii) percent of specimens with optimum length in catch, with 100% as target; and (iii) percentage of ‘mega-spawners‘ in catch, with 0% as target, and 30–40% as representative of reasonable stock structure if no upper size limit exists. Application of these indicators to stocks of Gadus morhua, Sardinella aurita and Epinephelus aeneus demonstrate their usefulness. It is argued that such simple indicators have the potential to allow more stakeholders such as fishers, fish dealers, supermarket managers, consumers and politicians to participate in fisheries management and eventually hold and reverse the global pattern of convenience overfishing, which is defined here as deliberate overfishing sanctioned by official bodies who find it more convenient to risk eventual collapse of fish stocks than to risk social and political conflicts.

Description: We investigated genetic differentiation among populations of the clonal grass Elymus athericus, a common salt-marsh species occurring along the Wadden Sea coast of Europe. While E. athericus traditionally occurs in the high salt marsh, it recently also invaded lower parts of the marsh. In one of the first analyses of the genetic population structure in salt-marsh species, we were interested in population differentiation through isolation-by-distance, and among strongly divergent habitats (low and high marsh) in this wind- and water-dispersed species. High and low marsh habitats were sampled at six sites throughout the Wadden Sea. Based on reciprocal transplantation experiments conducted earlier revealing lower survival of foreign genotypes we predicted reduced gene flow among habitats. Accordingly, an analysis with polymorphic cross-species microsatellite primers revealed significant genetic differentiation between high and low marsh habitats already on a very small scale (〈 100 m), while isolation-by-distance was present only on larger scales (60–443 km). In an analysis of molecular variance we found that 14% of the genetic variance could be explained by the differentiation between habitats, as compared to only 8.9% to geographical (isolation-by-distance) effects among six sites 2.5–443 km distant from each other. This suggests that markedly different selection regimes between these habitats, in particular intraspecific competition and herbivory, result in habitat adaptation and restricted gene flow over distances as small as 80 m. Hence, the genetic population structure of plant species can only be understood when considering geographical and selection-mediated restrictions to gene flow simultaneously.

Description: Breaking waves markedly increase the rates of air–sea transfer of momentum, energy and mass. In light to moderate wind conditions, spilling breakers with short wavelengths are observed frequently. Theory and laboratory experiments have shown that, as these waves approach breaking in clean water, a ripple pattern that is dominated by surface tension forms at the crest. Under laboratory conditions and in theory, the transition to turbulent flow is triggered by flow separation under the ripples, typically without leading to overturning of the free surface15. Water surfaces in nature, however, are typically contaminated by surfactant films that alter the surface tension and produce surface elasticity and viscosity16, 17. Here we present the results of laboratory experiments in which spilling breaking waves were generated mechanically in water with a range of surfactant concentrations. We find significant changes in the breaking process owing to surfactants. At the highest concentration of surfactants, a small plunging jet issues from the front face of the wave at a point below the wave crest and entraps a pocket of air on impact with the front face of the wave. The bubbles and turbulence created during this process are likely to increase air–sea transfer.

Description: 1. We performed a mesocosm experiment to investigate the structuring and cascading effects of two predominant crustacean mesozooplankton groups on microbial food web components. The natural summer plankton community of a mesotrophic lake was exposed to density gradients of Daphnia and copepods. Regression analysis was used to reveal top-down impacts of mesozooplankton on protists and bacteria after days 9 and 15. 2. Selective grazing by copepods caused a clear trophic cascade via ciliates to nanoplankton. Medium-sized (20-40 mum) ciliates (mainly Oligotrichida) were particularly negatively affected by copepods whereas nanociliates (mainly Prostomatida) became more abundant. Phototrophic and heterotrophic nanoflagellates increased significantly with increasing copepod biomass, which we interpret as an indirect response to reduced grazing pressure from the medium-sized ciliates. 3. In Daphnia-treatments, ciliates of all size classes as well as nanoflagellates were reduced directly but the overall predation effect became most strongly visible after 15 days at higher Daphnia biomass. 4. The response of bacterioplankton involved only modest changes in bacterial biomass and cell-size distribution along the zooplankton gradients. Increasing zooplankton biomass resulted either in a reduction (with Daphnia) or in an increase (with copepods) of bacterial biovolume, activity and production. Patterns of bacterial diversity, as measured by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), showed no distinct grouping after 9 days, whereas a clear treatment-coupled similarity clustering occurred after 15 days. 5. The experiment demonstrated that zooplankton-mediated predatory interactions cascade down to the bacterial level, but also revealed that changes occurred rather slowly in this summer plankton community and were most pronounced with respect to bacterial activity and composition.

Description: Here we present a meta-analytic approach to analyzing population interactions across the North Atlantic Ocean. We assembled all available biomass time series for a well-documented predator–prey couple, Atlantic cod (Gadus morhua) and northern shrimp (Pandalus borealis), to test whether the temporal dynamics of these populations are consistent with the “top-down” or the “bottom-up” hypothesis. Eight out of nine regions showed inverse correlations of cod and shrimp biomass supporting the “top-down” view. Exceptions occurred only close to the southern range limits of both species. Random-effects meta-analysis showed that shrimp biomass was strongly negatively related to cod biomass, but not to ocean temperature in the North Atlantic Ocean. In contrast, cod biomass was positively related to ocean temperature. The strength of the cod–shrimp relationship, however, declined with increasing mean temperature. These results show that changes in predator populations can have strong effects on prey populations in oceanic food webs, and that the strength of these interactions may be sensitive to changes in mean ocean temperature. This means that the effects of overfishing in the ocean cascade down to lower trophic levels, as has been shown previously for lakes and coastal seas. In order to further investigate these processes, we establish a methodological framework to analyze species interactions from time series data.

Description: Noble-gas geochemistry is an important tool for understanding planetary processes from accretion to mantle dynamics and atmospheric formation. Central to much of the modelling of such processes is the crystal–melt partitioning of noble gases during mantle melting, magma ascent and near-surface degassing5. Geochemists have traditionally considered the 'inert' noble gases to be extremely incompatible elements, with almost 100 per cent extraction efficiency from the solid phase during melting processes. Previously published experimental data on partitioning between crystalline silicates and melts has, however, suggested that noble gases approach compatible behaviour, and a significant proportion should therefore remain in the mantle during melt extraction. Here we present experimental data to show that noble gases are more incompatible than previously demonstrated, but not necessarily to the extent assumed or required by geochemical models. Independent atomistic computer simulations indicate that noble gases can be considered as species of 'zero charge' incorporated at crystal lattice sites. Together with the lattice strain model9, 10, this provides a theoretical framework with which to model noble-gas geochemistry as a function of residual mantle mineralogy.

Description: Based on the analysis of seafloor topography together with historical, geological and palaeogeographical data obtained from published and archived sources, the position of former Ice Complex (IC) islands has been reconstructed. Within the Laptev Sea shelf and in the western part of the East Siberian Sea shelf, most of these islands have been destroyed by coastal thermal erosion and thermal abrasion during the last thousand years or so. The IC islands were the remnants of the ice-rich syncryogenic freshwater terrestrial deposits (so called IC), which covered most of the arctic coastal plains and the emerged arctic shelf during the Late Pleistocene. At the present time, sandbanks exist at the places of former IC islands. These sandbanks are the subject of intense seafloor thermal abrasion. The approximate rates of seafloor thermal abrasion and the time of complete disappearance of these islands during the last thousand years have been estimated. The rate is different for different islands and for different time intervals. The most common values are between 0.02 and 0.3 m/year. Schematic maps of the former IC islands within the Laptev Sea and western part of the East Siberian Sea shelves have been compiled.

Description: Five microsatellite markers were developed for the snow crab (Chionoecetes opilio) and polymerase chain reaction conditions and/or primer sequences of three previously developed microsatellites were adapted for fluorescent labelling analysis. All loci were analysed in 449 individuals from 11 sampling sites in the northwest Atlantic. The high degree of polymorphism exhibited by these microsatellites (mean of 34 alleles per locus and mean observed heterozygosity of 0.76) suggests that they will be suitable for spatial and temporal genetic analysis of C. opilio populations.

Description: Conceptual models predict counteractive effects of herbivores and nutrient enrichment on plant diversity and reversed effects of grazers under different nutrient regimes. I tested these hypotheses in 11 field experiments with periphyton communities in three different aquatic habitats (a highly eutrophic lake, an meso-eutrophic lake, and an meso-eutrophic part of the Baltic Sea coast) and in different seasons. Grazer access and nutrient supply were manipulated in a factorial design. Species richness and evenness were chosen as response variables. Both manipulated factors had significant and contrasting effects on diversity, with variable effect strength between sites and seasons. From the two aspects of diversity, evenness well reflected the changes in community composition. Fertilization tended to increase the dominance of few species and thus to decrease evenness, whereas grazers counteracted these effects by removing dominant life forms. The response of species richness was not as expected, since grazers decreased richness throughout, whereas nutrients had weaker effects but tended to increase richness. Species richness rather reflected changes in periphyton architecture. Grazers reduced algal richness presumably by co-consumption of rare species in the tightly connected periphyton assemblages, whereas enrichment may increase richness by providing more structure via increased dominance of filamentous species. Although grazer and nutrient effects on richness and evenness were opposing, there was no change in the effect of one factor by manipulation of the other.

Description: Explored were methods to derive preliminary information on growth from other known life history parameters such as maximum size and size and age at first maturity. Use was made of the fact that with asymptotic length known, only one point is needed to determine the general shape of a von Bertalanffy growth curve. An empirical relationship was used to predict asymptotic length from maximum observed length. We used mean size reached at age 1 or 2 or mean age and size at first maturity, as is often provided in the literature, to derive preliminary von Bertalanffy growth curves. Results of this approach were then compared with published growth estimates. We used an empirical relationship to predict length at first maturity from asymptotic length when only the age at first maturity was given in the literature. Temperate fishes usually have restricted spawning periods lasting a few months per year and maturity is typically reached in the first, second, third, or later year, i.e. in steps of 12 months, with larger species maturing later. We used data in FishBase (http://www.fishbase.org) to establish typical ranges for age at first maturity and growth performance of temperate fishes as a function of maximum size. We present an approach that uses this framework to derive preliminary growth estimates for species of which only the maximum size is known.

Description: In the eastern Karawanken Mountains, the siliciclastic sedimentary succession of the Hochwipfel Formation was deposited within a narrow marginal basin of the western Paleotethys. Variations of detrital sandstone modes define four petrofacies types, and allow the succession to be stratigraphically divided into Lower and Upper Hochwipfel Formation. Petrographical and geochemical provenance analysis indicate that the basal quartz-rich sandstones derived mainly from the Intraalpine Terrane in the north and the passive Gondwana margin in the south. In the sediments of the Upper Hochwipfel Formation, an increase of (meta)sedimentary as well as of magmatic lithoclasts is discernible indicating a convergent tectonic situation and increased sediment supply derived from a magmatic arc. Zusammenfassung: Die klastische Sedimentabfolge der karhonen HochwipfelFormation der Ostkarawanken wurde in einem schmalen Randbecken der westlichen Paläotethys abgelagert. Auf Grund der Modalzusammensetzung der Sandsteine lassen sich vier Petrofaziestypen unterscheiden, und die sedimentäre Abfolge in eine Untere und eine Obere Hochwipfel-Formation gliedern. Petrographische und geochemische Provenienz-Indikatoren deuten darauf hin, dass die basalen quarzreichen Sandsteine der unteren Hochwipfel-Formation überwiegend von dem nördlich gelegenen Intraalpinen Terran bzw. dem südlich gelegenen passiven Kontinentalrand Gondwanas stammen. In den Sedimenten der oberen Hochwipfel-Formation ist eine Zunahme von (meta)sedimentären Lithoklasten sowie magmatischen Gesteinsbruchstücken zu beobachten. Dies zeigt den Übergang zu einer konvergenten tektonischen Situation und den verstärkten Sedimenteintrag aus einem magmatischen Bogen an.

Description: Sediment proxy records from a continuous, 1.5 million year long deep-sea sediment core from a site in the western Norwegian Sea were used to obtain new insights into the nature of palaeoceanographic change in the northern North Atlantic (Nordic seas) during the climatic shift of the Mid-Pleistocene Revolution (MPR). Red-green sediment colour and magnetic susceptibility records both reveal significant differences in their mean values when comparing the intervals older than 700 000 yr (700 ka) with those from the past 500 kyr. The timing and duration of these changes indicates that the MPR in the Nordic seas is characterised by a gradual transition lasting about 200 kyr. Together with further sedimentological evidence this suggests that the mid-Pleistocene climate shift was accompanied by a general change in ice-drift pattern. It is further proposed that prior to the onset of the major late Pleistocene glaciations in the Northern Hemisphere a significant proportion of the ice in the eastern Nordic seas originated from a southern provenance, whereas later it dominantly came from the surrounding landmasses.

Description: More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic communities, and a large fraction of the annual food load can arrive in pulses within a few days1, 2. Owing to logistical constraints, the available data concerning the fate of such a pulse are scattered3, 4 and often contradictory5, 6, 7, 8, 9, 10, hampering global carbon modelling and anthropogenic impact assessments. We quantified (over a period of 2.5 to 23 days) the response of an abyssal benthic community to a phytodetritus pulse, on the basis of 11 in situ experiments. Here we report that, in contrast to previous hypotheses5, 6, 7, 8, 9, 10, 11, the sediment community oxygen consumption doubled immediately, and that macrofauna were very important for initial carbon degradation. The retarded response of bacteria and Foraminifera, the restriction of microbial carbon degradation to the sediment surface, and the low total carbon turnover distinguish abyssal from continental-slope ‘deep-sea’ sediments.

Description: Pseudocalanus elongatus is a key species in the pelagic zone of the deep basins of the Central Baltic Sea. The copepod serves as a major food organism for larval as well as for adult, pelagic planktivorous fish. Large interannual fluctuations in the standing stock of P. elongatus have been attributed to significant changes in the hydrographic environment over the last two decades. In particular, the decreasing salinity in the Baltic deep basins, a result of a change in atmospheric forcing leading to an increase in rainfall since the 1980s and of a lack of pulses of saline water intrusions from the North Sea, was found to affect reproduction and maturation of the copepod. In parallel, dramatic changes in the weight-at-age of herring, one of the most important commercial fishes of the Baltic Sea, have been observed since the late 1980s. Using time-series on herring stomach contents, as well as length and weight, we provide evidence for a chain of events relating variability in climate, salinity and P. elongatus abundance to changes in diet and condition of herring in the Central Baltic Sea.

Description: The shells of the planktonic foraminifer Neogloboquadrina pachyderma have become a classical tool for reconstructing glacial–interglacial climate conditions in the North Atlantic Ocean1, 2, 3. Palaeoceanographers utilize its left- and right-coiling variants, which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late Quaternary sediments1, 2, 4, 5. Recently discovered cryptic genetic diversity in planktonic foraminifers6, 7, 8 now poses significant questions for these studies. Here we report genetic evidence demonstrating that the apparent ‘single species’ shell-based records of right-coiling N. pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change. This is reflected in a species-dependent incremental shift in right-coiling N. pachyderma shell calcite δ18O between the Last Glacial Maximum and full Holocene conditions. Guided by the percentage dextral coiling ratio, our findings enhance the use of δ18O records of right-coiling N. pachyderma for future study. They also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies.

Description: Stable oxygen and carbon isotope profiles from modern bivalve shells were investigated in order to reconstruct short-term hydrographical changes in the river-shelf system of the Laptev Sea. Oxygen isotopic profiles obtained from the aragonitic species Astarte borealis exhibit amplitude cycles interpreted as annual hydrographical cycles. These records reflect the strong contrast between summer and winter bottom water conditions in the Laptev Sea. The seasonal variations in δ18O are mainly controlled by the riverine freshwater discharge during summer with 0.5‰ per salinity unit. Corrected for a defined species-dependent fractionation offset of -0.37‰, time-dependent salinity records were reconstructed from these δ18O profiles. They indicate a good correspondence to seasonal hydrographic changes and synoptical data. Persistent trends with shell growth towards more negative δ13C values are observed in all specimens and appear to be related to metabolic changes of the bivalves during ontogeny. In contrast, short-term fluctuations are likely linked to seasonal variabilities of the river water outflow patterns and enhanced phytoplankton productivity during summer. This is corroborated by a clear watermass-related distinction of the various δ13C records made on the basis of water depth and distance from the riverine source.

Description: A set of histological characteristics to judge ovarian development was established and used to elaborate morphological criteria of 10 maturity stages of Baltic cod Gadus morhua sampled throughout the annual cycle to represent different macroscopic maturity stages. The applied characteristics confirmed most stages of the macroscopic scale, but the separation of late immature and resting mature females remained imprecise. Atretic vitellogenic oocytes or encapsulated residual eggs identified the resting condition morphologically, but not all ovaries with visible signs of previous spawning showed such features. One ovarian stage that was previously classified as ‘ripening’ was changed to ‘spawning’, owing to the prevalence of hydrated eggs and empty follicles. Ovaries with malfunctions were defined by a separate stage. Macroscopic criteria were revised by comparing the gross anatomy of ovaries with their histology. Female length and gonado-somatic index supported stage definitions, but substantial variation in Fulton's condition factor and the hepato-somatic index rendered these of little use for this purpose. The time of sampling influenced staging accuracy. A female spawner probability function based on the proportion of ripening and ripe specimens in early spring seems to be the most appropriate method to estimate spawner biomass and reproductive potential.

Description: Standard length, dry mass and RNA : DNA ratio measurements of 3876 Atlantic cod Gadus morhua larvae and juveniles from 26 families of recruit (fish during their first year of spawning) and repeat spawners (fish which were in their subsequent spawning season) reared in two mesocosms (2500 and 4400 m3) under semi-natural conditions were analysed over a period of 10 weeks using microsatellites. Larvae from recruit spawners were significantly longer and heavier at hatch and throughout the 10 weeks. RNA : DNA ratios from recruit spawner offspring were only significantly higher at week 1. The smaller (2500 m3) mesocosm was characterized by low plankton density during the transition from endogenous to exogenous feeding followed by a higher density during the metamorphosis period (weeks 4 and 5), with the reverse pattern evident in the 4400 m3 mesocosm. Patterns of larval growth followed patterns of zooplankton density. Significant differences in RNA : DNA ratios between the mesocosms at all comparable sampling dates were found and within each mesocosm individual fish exhibited a wide range of growth and condition responses under the same environmental conditions. RNA : DNA ratios as a function of size differed in the amount of variability between mesocosms, indicating that the higher food density led to a higher proportion of well-conditioned larvae in the first 3 weeks. Food availability probably has a major role in determining offspring growth and condition, with limited effects due to maternal effects in cases where the broodstock females are approximately of similar size and condition.

Description: We have performed a 3-D seismic refraction tomography of a 48 × 48 km2 area surrounding ODP site 757, which is planned to host an International Ocean Network (ION) permanent seismological observatory, called the Ninetyeast Ridge Observatory (NERO). The study area is located in the southern part of the Ninetyeast Ridge, the trail left by the Kerguelen hotspot on the Indian plate. The GEOMAR Research Centre for Marine Geosciences and the Federal Institute for Geosciences and Natural Resources acquired 18 wide-angle profiles recorded by 23 ocean bottom hydrophones during cruise SO131 of R/V Sonne in spring 1998. We apply a first arrival traveltime tomography technique using regularized inversion to recover the 3-D velocity structure relative to a 1-D background model that was constructed from a priori information and averaged traveltime data. The final velocity model revealed the crustal structure down to approximately 8 km depth. Resolution tests showed that structures with approximately 6 km horizontal extent can reliably be resolved down to that depth. The survey imaged the extrusive layer of the upper crust of the Ninetyeast Ridge, which varies in thickness between 3 and 4 km. A high-velocity anomaly coinciding with a positive magnetic anomaly represents a volcanic centre from which crust in this area is thought to have formed. A pronounced low-velocity anomaly is located underneath a thick sedimentary cover in a bathymetric depression. However, poor ray coverage of the uppermost kilometre of the crust in this area resulted in smearing of the shallow structure to a larger depth. Tests explicitly including the shallow low-velocity layer confirmed the existence of the deeper structure. The heterogeneity of the upper crust as observed by our study will have consequences for the waveforms of earthquake signals to be recorded by the future seismic observatory.

Description: During peak spawning of sprat Sprattus sprattus in the Baltic Sea in May–June egg specific gravity averaged ±s.d. 1·00858 ± 0·00116 g cm−3 but was significantly higher in the beginning and significantly lower towards the end of the spawning season. A close relationship was found between egg diameter and egg specific gravity (r2 = 0·71). This relationship, however, changed during the spawning season indicating that some other factor was involved causing the decrease in specific gravity during the spawning period. The vertical egg distribution changed during the spawning season: eggs were distributed mainly in the deep layers early in the season, occurred in and above the permanent halocline during peak spawning, and above the halocline towards the end of the spawning season. Consequently, poor oxygen conditions in the deep layers and low temperatures in layers between the halocline and the developing thermocline may affect egg development. Thus, opportunities for egg development vary over the spawning season and among spawning areas, and depending on frequency of saline water inflows into the Baltic Sea and severity of winters, between years

Description: The Messinian salinity crisis—the desiccation of the Mediterranean Sea between 5.96 and 5.33 million years (Myr) ago1—was one of the most dramatic events on Earth during the Cenozoic era2. It resulted from the closure of marine gateways between the Atlantic Ocean and the Mediterranean Sea, the causes of which remain enigmatic. Here we use the age and composition of volcanic rocks to reconstruct the geodynamic evolution of the westernmost Mediterranean from the Middle Miocene epoch to the Pleistocene epoch (about 12.1–0.65 Myr ago). Our data show that a marked shift in the geochemistry of mantle-derived volcanic rocks, reflecting a change from subduction-related to intraplate-type volcanism, occurred between 6.3 and 4.8 Myr ago, largely synchronous with the Messinian salinity crisis. Using a thermomechanical model, we show that westward roll back of subducted Tethys oceanic lithosphere and associated asthenospheric upwelling provides a plausible mechanism for producing the shift in magma chemistry and the necessary uplift (approx1 km) along the African and Iberian continental margins to close the Miocene marine gateways, thereby causing the Messinian salinity crisis.

Description: 1. Negative effects of zooplankton on the availability of phosphorus (P) for phytoplankton as a result of the retention of nutrients in zooplankton biomass and the sedimentation of exoskeletal remains after moulting, have been recently proposed. 2. In a mesocosm study, the relative importance of these mechanisms was tested for the freshwater cladoceran Daphnia hyalina×galeata. A total of 13 mesocosm bags was suspended in a mesotrophic German lake during summer 2000 and fertilised with inorganic P in order to obtain a total nitrogen to total P ratio closer to the Redfield ratio. D. hyalina×galeata was then added at a logarithmically scaled density gradient of up to 40 ind. L−1. Zooplankton densities, dissolved inorganic, particulate organic (seston 〈100 μm), as well as total nutrient concentrations were monitored. Additionally, nutrient concentrations of sediment water removed from the bottom of the mesocosm bags via a manual pump were determined. 3. Seston carbon (C), seston P and total P were significantly negatively correlated with Daphnia densities. The amount of particulate P (∼5–6 μg P L−1) sequestered from the seston compartment by Daphnia corresponded roughly to the increase of zooplankton biomass (population growth). Soluble reactive phosphorous (SRP) was at all times high (∼25–35 μg P L−1) and possibly unavailable to phytoplankton as a result of P adsorption to calcite during a calcite precipitation event (whiting). P concentrations determined in sediment water were generally 〈60 μg P m−2 and thus never exceeded 1% of the total amount of P bound in particulate matter of the overlying water column. 4. Seston C : P ratios followed a polynomial second-order function: At Daphnia densities 〈40 ind. L−1 a positive linear relationship was evident, which is explained by the stronger reduction of P compared with C in seston, and transfer of seston P to zooplankton. Highest seston C : P ratios of ∼300 : 1 were observed at Daphnia densities of ∼30–50 ind. L−1, which is in agreement with proposed threshold values limiting Daphnia reproductive growth. At Daphnia densities 〉40–50 ind. L−1 C : P ratios were decreased because of the strong reduction of seston C at close to constantly low seston P-values of ∼3–4 μg P L−1. 5. At least for Daphnia, it may be concluded that – unlike population growth – the sedimentation of faecal pellets and carapaces after moulting seem negligible processes in pelagic phosphorus dynamics.

Description: The use of radar Doppler velocimetry for the observation of volcanic activity is new. We used this method to continuously observe the activity of one vent of Stromboli volcano, Italy, from the end of 2000 April until early May. During this period we recorded 702 eruptions, 132 of which occurred before a strong rain storm passed over the island on April 29. In order to interpret the recorded Doppler data we developed a program that simulates different strombolian eruption scenarios, for which we then calculate the theoretical Doppler spectra. Comparing our theoretical data with the observed data we are able to show that most of the eruptions are nearly vertical, although we did observe only one component of the eruption vector with our Doppler radar. One of the most interesting features of the data set is a significant change in eruptive behaviour that correlates with the occurrence of the rain storm: we find that on average the eruption duration increased by a factor of 2, eruptive velocities were much higher and indirect evidence indicates that the average particle diameter of the erupted material decreased. This change may have several causes, but the coincidence with the rain storm may be evidence of magma–water interaction and feedback on the volcanic activity. If the fluid source (rain) changing the eruptive style is at the surface and in near-surface layers then the main control on final eruption dynamics at Stromboli volcano must also be in rather shallow regions.

Description: The Archean Murchison greenstone belt, Northern Province, South Africa, represents a rifted volcanic arc sequence hosting the largest volcanogenic massive sulfide (VMS) district in Southern Africa. The VMS deposits of the "Cu-Zn line" developed during the initial phases of highly evolved felsic volcanism between 2971 and 2965 Ma and are closely associated with quartz-porphyritic rhyolite domes. Elevated heat supply along slow-spreading rift segments ensured regional hydrothermal convection along the entire rift axis. Recurrent volcanism resulted in frequent disruption of hydrothermal discharge and relative short-lived episodes of hydrothermal activity. Stable thermal conditions favoured the local development of mature hydrothermal vent fields from focused fluid discharge and sulfide precipitation in thin layers of volcaniclastic rocks. Ore mineralogy and geochemical composition attest to hydrothermal activity at moderate temperatures of 〈= 250 °C for the entire rift axis, with short-lived pulses of higher temperature(~ 300 °C) fluid upflow. Major and trace metal composition of the deposits attests to the highly differentiated felsic source rocks. Fluid and host rock compositions constrained favourable conditions for the enrichment of indium in the massive sulfide deposits defining the "Cu-Zn line" as a type example for the enrichment of indium in the volcanogenic environment.

Description: An excellent sediment record from the Arabian Sea traces recent patterns in the activity of the Asian monsoon. It reveals both variability in monsoon strength and links with climatic events elsewhere. The monsoon is the main determinant of environmental conditions over much of Asia, and so affects the most densely populated region on Earth. Differential heating of the north Indian Ocean and the northwest Pacific, and of the Asian land-mass, cause the seasonal reversal of monsoon winds. In summer, these winds blow northwards over the northern Indian Ocean, carrying huge amounts of moisture over the neighbouring land. The ensuing heavy rainfall can have devastating consequences for human life and livelihood. Conversely, agriculture in Asia depends on monsoon rains; and the seasonal upwelling of nutrient-laden subsurface waters, driven by monsoon winds, is essential to the success of coastal fisheries.

Description: A high-resolution mapping and sampling study of the Gakkel ridge was accomplished during an international ice-breaker expedition to the high Arctic and North Pole in summer 2001. For this slowest-spreading endmember of the global mid-ocean-ridge system, predictions were that magmatism should progressively diminish as the spreading rate decreases along the ridge, and that hydrothermal activity should be rare. Instead, it was found that magmatic variations are irregular, and that hydrothermal activity is abundant. A 300-kilometre-long central amagmatic zone, where mantle peridotites are emplaced directly in the ridge axis, lies between abundant, continuous volcanism in the west, and large, widely spaced volcanic centres in the east. These observations demonstrate that the extent of mantle melting is not a simple function of spreading rate: mantle temperatures at depth or mantle chemistry (or both) must vary significantly along-axis. Highly punctuated volcanism in the absence of ridge offsets suggests that first-order ridge segmentation is controlled by mantle processes of melting and melt segregation. The strong focusing of magmatic activity coupled with faulting may account for the unexpectedly high levels of hydrothermal activity observed.

Description: A compilation of δ44/40Ca (δ44/40Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF2 reference sample. The deviations in δ44/40Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between δ44/40Ca of NIST SRM 915a and seawater is defined as -1.88 O.O4%o (δ44/42CaNISTSRM915a/Sw= -0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation δ44/40CaSa/Sw=δ44/40CaSa/NIST SRM 915a - 1.88 (δ44/42CaSa/Sw=δ44/42CaSa/NIST SRM 915a - 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies.

Description: A 20-Myr record of creation of oceanic lithosphere is exposed along a segment of the central Mid-Atlantic Ridge on an uplifted sliver of lithosphere. The degree of melting of the mantle that is upwelling below the ridge, estimated from the chemistry of the exposed mantle rocks, as well as crustal thickness inferred from gravity measurements, show oscillations of ∼3–4 Myr superimposed on a longer-term steady increase with time. The time lag between oscillations of mantle melting and crustal thickness indicates that the mantle is upwelling at an average rate of ∼25 mm yr-1, but this appears to vary through time. Slow-spreading lithosphere seems to form through dynamic pulses of mantle upwelling and melting, leading not only to along-axis segmentation but also to across-axis structural variability. Also, the central Mid-Atlantic Ridge appears to have become steadily hotter over the past 20 Myr, possibly owing to north–south mantle flow.

Description: A total of five sediment cores from three sites, the Arctic Ocean, the Fram Strait and the Greenland Sea, yielded evidence for geomagnetic reversal excursions and associated strong lows in relative palaeointensity during oxygen isotope stages 2 and 3. A general similarity of the obtained relative palaeointensity curves to reference data can be observed. However, in the very detail, results from this high‐resolution study differ from published records in a way that the prominent Laschamp excursion is clearly characterized by a significant field recovery when reaching the steepest negative inclinations, whereas only the N–R and R–N transitions are associated with the lowest values. Two subsequent excursions also reach nearly reversed inclinations but without any field recovery at that state. A total of 41 accelerator mass spectrometry (AMS) 14C ages appeared to allow a better age determination of these three directional excursions and related relative palaeointensity variations. However, although the three sites yielded more or less consistent chronological as well as palaeomagnetic results a comparison to another site, PS2644 in the Iceland Sea, revealed significant divergences in the ages of the geomagnetic field excursions of up to 4 ka even on basis of uncalibrated AMS 14C ages. This shift to older 14C ages cannot be explained by a time‐transgressive character of the excursions, because the distance between the sites is small when compared with the size of and the distance to the geodynamo in the Earth's outer core. The most likely explanation is a difference of reservoir ages and/or mixing with old 14C‐depleted CO2 from glacier ice expelled from Greenland at site PS2644.

Description: The cyanobacteria Synechococcus and Prochlorococcus are important primary producers in marine ecosystems. Because currently available approaches for estimating microbial growth rates can be difficult to apply in the field, we have been exploring the feasibility of using quantitative rRNA measurements as the basis for making such estimates. In this study we examined the relationship between rRNA and growth rate in several Synechococcus and Prochlorococcus strains over a range of light-regulated growth rates. Whole-cell hybridization with fluorescently labeled peptide nucleic acid (PNA) probes was used in conjunction with flow cytometry to quantify rRNA on a per cell basis. This PNA probing technique allowed rRNA analysis in a phycoerythrin-containing Synechococcus strain (WH7803) and in a non-phycoerythrincontaining strain and in Prochlorococcus. All the strains showed a qualitatively similar tri-phasic relationship between rRNA·cell-1 and growth rate, involving relatively little change in rRNA·cell-1 at low growth rates, linear increase at intermediate growth rates, and a plateau and/or decrease at the highest growth rates. The onset of each phase was associated with the relative, rather than absolute, growth rate of each strain. In the Synechococcus strains, rRNA normalized to flow cytometrically measured forward angle light scatter (an indicator of size) was well-correlated with growth rate across strains. These findings support the idea that cellular rRNA may be useful as an indicator of in situ growth rate in natural Synechococcus and Prochlorococcus populations.

Description: A microsatellite dinucleotide-enriched library was obtained from the European squid (Loligo vulgaris) and five species-specific dinucleotide markers were optimized. These markers are highly polymorphic with average expected heterozygosity ranging from 0.706 to 0.927 and allele number ranging from 7 to 17. This set of primers is suitable for population genetic studies.

Description: A mature female Galiteuthis glacialis (430 mm mantle length) was caught south of the Falkland Islands (53°S, 58°W) at a depth of 976-1001 m over a bottom depth of 1582-2378 m. A total of 8 spermatangia (15-19 mm in length) were found inserted into the mantle wall, which was of gelatinous consistency. Its ovary contained 3 605±42 oocytes, mostly 2.2-2.5 mm in length, and there were 21 ripe eggs (3.0-3.2±2.2-2.7 mm) in the oviducts. Only one resorpting oocyte (1.4 mm) was found. This is the only description of a mature female of this species, though two spent females have been previously described and three more mentioned by other authors.

Description: The speed at which mid-ocean ridges grind out new ocean floor varies considerably. The slowest-spreading ridges are especially tough to study — but the latest data show that they are especially intriguing.

Description: A three-dimensional hydrodynamic model has been used to analyse temporally and spatially resolved circulation patterns in the Baltic Sea with special emphasis on drifting particles representing larval fish. The main purpose of this study was (i) to investigate potential drift patterns of larval fish, (ii) to identify its intra- and inter-annual variability for time periods based on the timing of spawning and (iii) to analyse its seasonal and spatial variability in dependence of the atmospheric forcing conditions. For the time period 1979–1998 temporally and spatially resolved simulated flow fields were used to describe the potential drift from the centre of main reproductive effort of Baltic cod (Gadus morhua). The results of the model runs demonstrate a general change in circulation pattern from retention during a first decade (1979–1988) to dispersion in the following decade (1989–1998). This increase in dispersion was related to an increase in the variability of the local wind forcing conditions over the Baltic. The more frequent occurrence of dispersion in spring of the recent decade was accompanied by a strong decay in biomass of one of the main larval fish feeding component in the central basin, the calanoid copepod Pseudocalanus elongatus. Larger dispersion of this prey organism may have affected the spatial overlap and thus the contact rates between predator and prey. Hence, this may have resulted in a food limitation for early life stages of Baltic cod and potentially contributed to the pronounced shift in cod peak spawning time from spring to late summer. Early life stages of cod originating from late spawning fish, benefited from a stronger dispersion in late summer and autumn, into shallow coastal areas with higher calanoid abundance.

Description: The simplified representation of clouds as horizontally homogeneous layers leads to qualitatively well known systematic errors in calculations of the domain averaged solar radiative fluxes. The present work tries to correlate the domain averaged radiative fluxes from three-dimensional (3d) cloud fields with the domain averaged properties of the cloudy atmosphere. The results will help to estimate the applicability of radiative transfer parameterizations in non-cloud-resolving circulation models. Three-dimensional cloud fields have been calculated from the mesoscale atmospheric circulation model GESIMA, and serve as input to a Monte Carlo radiative transfer code. The cloud fields have a pronounced 3d structure in extinction, scattering and absorption properties of the cloud hydrometeors (mixed-phase clouds). It is shown that domain averaged albedo is strongly correlated with cloud cover. The correlation coefficient is improved by adding cloud thickness or the combination of liquid water path and cloud top temperature. Absorption is described best by cloud top temperature together with liquid water path for small and ice water path for large solar zenith angles (SZA). Cloud thickness further improves the correlation with absorption. Total transmission as well as its parts diffuse and direct transmission correlate best with cloud cover and liquid water path, further with cloud top temperature or cloud thickness in case of the diffuse transmission. Nonlinear regressions based on the optimal three cloud parameters yield smallest correlation coefficients of 0.88 for albedo, 0.84 for absorption and 0.92 for total transmission. Only the correlation coefficient for diffuse transmission falls below 0.8 for very large SZAs. Because of this high correlation we conclude that it appears possible to parameterize domain averaged radiative fluxes for 3d cloud fields without information of the internal cloud structure. Die vereinfachte Annahme horizontal homogener Wolkenschichten führt zu qualitativ gut bekannten systematischen Fehlern in der Berechnung der gebietsgemittelten solaren Strahlungsflüsse. Die vorliegende Arbeit stellt den Zusammenhang zwischen gebietsgemittelten Strahlungsflüssen dreidimensionaler (3d) Wolkenfelder und den ebenso gemittelten Wolkeneigenschaften her. Die Ergebnisse dienen zur EinschÄtzung der Anwendbarkeit von Parametrisierungen der Strahlungsbilanz in nicht-wolkenauflösenden Zirkulationsmodellen. Mit Hilfe des mesoskaligen atmosphÄrischen Zirkulationsmodells GESIMA wurden die Eingangsfelder für ein Monte Carlo Strahlungstransportmodell berechnet. Die Wolkenfelder haben eine ausgeprÄgte 3d Strukur sowohl in der Extinktion als auch in den Streu- und Absorptionseigenschaften der Wolkenhydrometeore (Mischphasenwolken). Es stellt sich heraus, dass die gebietsgemittelte Albedo am stÄrksten mit dem Bedeckungsgrad, verbessert noch durch Hinzunahme der vertikalen Wolkenausdehnung beziehungsweise der Kombination aus Flüssigwasserpfad und Wolkenoberkantentemperatur, korreliert ist. Die Absorption lÄsst sich am besten durch die Wolkenoberkantentemperatur zusammen mit dem Flüssigwassergehalt bei kleinen und dem Eiswasserpfad bei großen Sonnenzenitwinkeln wiedergeben, weiter verbessert durch die vertikale Wolkenausdehnung. Sowohl die Gesamttransmission als auch ihre beiden Anteile, die diffuse und die direkte Transmission, korrelieren optimal mit dem Bedeckungsgrad und dem Flüssigwasserpfad und weiterhin mit der Wolkenoberkantentemperatur beziehungsweise der vertikalen Wolkenerstreckung bei der diffusen Transmission. Nichtlineare Regressionen mit drei jeweils optimalen Wolkenparametern ergeben kleinste Korrelationskoeffizienten von 0,88 für die Albedo, 0,84 für die Absorption und 0,92 für die Gesamttransmission. Einzig der Korrelationskoeffizient für die diffuse Transmission sinkt für sehr flache SonnenstÄnde unter 0,8. Aufgrund dieser hohen Korrelation schließen wir, dass es möglich erscheint, gebietsgemittelte Strahlungsflüsse dreidimensionaler Wolkenfelder ohne Informationen zur internen Wolkenstruktur zu parametrisieren.

Description: Serious concerns have been raised about the ecological effects of industrialized fishing1, 2, 3, spurring a United Nations resolution on restoring fisheries and marine ecosystems to healthy levels4. However, a prerequisite for restoration is a general understanding of the composition and abundance of unexploited fish communities, relative to contemporary ones. We constructed trajectories of community biomass and composition of large predatory fishes in four continental shelf and nine oceanic systems, using all available data from the beginning of exploitation. Industrialized fisheries typically reduced community biomass by 80% within 15 years of exploitation. Compensatory increases in fast-growing species were observed, but often reversed within a decade. Using a meta-analytic approach, we estimate that large predatory fish biomass today is only about 10% of pre-industrial levels. We conclude that declines of large predators in coastal regions5 have extended throughout the global ocean, with potentially serious consequences for ecosystems5, 6, 7. Our analysis suggests that management based on recent data alone may be misleading, and provides minimum estimates for unexploited communities, which could serve as the 'missing baseline'8 needed for future restoration efforts.

Description: The dehydration of subducting oceanic crust and upper mantle has been inferred both to promote the partial melting leading to arc magmatism and to induce intraslab intermediate-depth earthquakes, at depths of 50–300 km. Yet there is still no consensus about how slab hydration occurs or where and how much chemically bound water is stored within the crust and mantle of the incoming plate. Here we document that bending-related faulting of the incoming plate at the Middle America trench creates a pervasive tectonic fabric that cuts across the crust, penetrating deep into the mantle. Faulting is active across the entire ocean trench slope, promoting hydration of the cold crust and upper mantle surrounding these deep active faults. The along-strike length and depth of penetration of these faults are also similar to the dimensions of the rupture area of intermediate-depth earthquakes.

Description: According to small subunit ribosomal RNA (ss rRNA) sequence comparisons all known Archaea belong to the phyla Crenarchaeota, Euryarchaeota, and—indicated only by environmental DNA sequences—to the 'Korarchaeota'1, 2. Here we report the cultivation of a new nanosized hyperthermophilic archaeon from a submarine hot vent. This archaeon cannot be attached to one of these groups and therefore must represent an unknown phylum which we name 'Nanoarchaeota' and species, which we name 'Nanoarchaeum equitans'. Cells of 'N. equitans' are spherical, and only about 400 nm in diameter. They grow attached to the surface of a specific archaeal host, a new member of the genus Ignicoccus3. The distribution of the 'Nanoarchaeota' is so far unknown. Owing to their unusual ss rRNA sequence, members remained undetectable by commonly used ecological studies based on the polymerase chain reaction4. 'N. equitans' harbours the smallest archaeal genome; it is only 0.5 megabases in size. This organism will provide insight into the evolution of thermophily, of tiny genomes and of interspecies communication.

Description: Although they can provide valuable information on at-sea ecology, data-loggers may adversely affect energetics, diving performance, and breeding success of equipped birds. With the aim of determining the effects of leg-attached data-loggers on the activity budgets of Humboldt penguins (Spheniscus humboldti) while on land, we equipped birds kept at the Landau Zoo, Landau, Germany, with such devices. We followed them during sample periods and recorded the occurrence and length of behaviors. Birds quickly habituated to the devices within 1 day of deployment, and mean rates of device-pecking were low (0.7–1.7 pecks/hr), with device-induced behaviors accounting for 〈1% of the mean daily activity budget. The method of device attachment appears behaviorally less stressful than the traditional tape-based system in which devices are normally attached to the penguin's back. By facilitating the testing of newly developed data-loggers on captive birds, or the development of methods for device attachment, zoos and aquaria may strengthen their role in animal conservation by helping research on free-ranging animals.

Description: Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.

Description: Fungi or bacteria that produce secondary metabolites often have the potential to bring up various compounds from a single strain. The molecular basis for this well-known observation was confirmed in the last few years by several sequencing projects of different microorganisms. Besides well-known examples about induction of a selected biosynthesis (for example, by high- or low-phosphate cultivation media), no overview about the potential in this field for finding natural products was given. We have investigated the systematic alteration of easily accessible cultivation parameters (for example, media composition, aeration, culture vessel, addition of enzyme inhibitors) in order to increase the number of secondary metabolites available from one microbial source. We termed this way of revealing nature's chemical diversity the 'OSMAC (One Strain-Many Compounds) approach' and by using it we were able to isolate up to 20 different metabolites in yields up to 2.6 g L(-1) from a single organism. These compounds cover nearly all major natural product families, and in some cases the high production titer opens new possibilities for semisynthetic methods to enhance even more the chemical diversity of selected compounds. The OSMAC approach offers a good alternative to industrial high-throughput screening that focuses on the active principle in a distinct bioassay. In consequence, the detection of additional compounds that might be of interest as lead structures in further bioassays is impossible and clearly demonstrates the deficiency of the industrial procedure. Furthermore, our approach seems to be a useful tool to detect those metabolites that are postulated to be the final products of an amazing number of typical secondary metabolite gene clusters identified in several microorganisms. If one assumes a (more or less) defined reservoir of genetic possibilities for several biosynthetic pathways in one strain that is used for a highly flexible production of secondary metabolites depending on the environment, the OSMAC approach might give more insight into the role of secondary metabolism in the microbial community or during the evolution of life itself.

Description: A key question in ecology is which factors control species diversity in a community1, 2, 3. Two largely separate groups of ecologists have emphasized the importance of productivity or resource supply, and consumers or physical disturbance, respectively. These variables show unimodal relationships with diversity when manipulated in isolation4, 5, 6, 7, 8. Recent multivariate models9, 10, however, predict that these factors interact, such that the disturbance–diversity relationship depends on productivity, and vice versa. We tested these models in marine food webs, using field manipulations of nutrient resources and consumer pressure on rocky shores of contrasting productivity. Here we show that the effects of consumers and nutrients on diversity consistently depend on each other, and that the direction of their effects and peak diversity shift between sites of low and high productivity. Factorial meta-analysis of published experiments confirms these results across widely varying aquatic communities. Furthermore, our experiments demonstrate that these patterns extend to important ecosystem functions such as carbon storage and nitrogen retention. This suggests that human impacts on nutrient supply11 and food-web structure12, 13 have strong and interdependent effects on species diversity and ecosystem functioning, and must therefore be managed together.

Description: BOOK REVIEWED: Plate Tectonics: An Insider's History of the Modern Theory of the Earth / edited by Naomi Oreskes Westview Press: 2001. 448 pp.

Description: In periphyton communities, autotrophic algae and prokaryotes live in close spatial proximity to heterotrophic components such as bacteria and micro- and meiofauna. In factorial field experiments, we manipulated grazer access and nutrient supply to periphyton communities and measured the effects on algal, ciliate, meiofaunal, and bacterial biomass. We tested whether grazing macrozoobenthos affects all periphytic components (generalist consumption), whether nutrient effects propagate through the community, and whether interactions between the different periphyton groups allow for indirect feedback mechanisms. The experiments were conducted during three different seasons in a meso-eutrophic lake in Sweden (Lake Erken) and at an adjacent coastal marine site (Väddö) of similar productivity, but with contrasting grazer fauna. We found strong direct effects of nutrients and grazing on algae at both sites. Algal biomass increased in fertilized treatments and was significantly reduced when grazers were present. The algae clearly dominated the system quantitatively and were positively correlated to the biomass of ciliates and meiofauna. The effects of grazing and nutrients were more complex for heterotrophs than for algae. Generally, the presence of grazers tended to increase the biomass of bacteria, ciliates, and meiofauna. Thus, macrograzers were not generalist consumers of the entire community, but mainly reduced algae. Furthermore, the results suggested strong indirect effects of grazing, presumably through changes in nutrient supply and algal size structure. Nutrient enrichment had weak and inconsistent effects on bacterial, ciliate, and meiofaunal biomass. There was thus no complete propagation of bottom-up effects through the community, and strong internal feedback mechanisms within the periphyton mediated the effects of macroconsumers and nutrient enrichment.

Description: A high-resolution Holocene tephrochronology for northern Germany has been established based on systematic tephrostratigraphical analysis of three peat bogs. Microscopic volcanic ash layers have been traced and characterised petrographically and by the chemical composition of the glass shards. At least 37 ash horizons representing 16 different explosive volcanic eruptions have been identified and many can be correlated between the three sites, up to 100 km apart. The tephra layers can be related to Icelandic volcanic sources and some correlated to the eruptions of Askja 1875, Hekla 3, Hekla Selsund, Hekla 4 and Hekla 5, as well as to unspecified eruptions of Icelandic volcanic systems, e.g. Torfajökull. The source volcanoes for some tephra layers remain unidentified. Some tephra layers were known previously from the North Atlantic region (e.g. Sluggan, Glen Garry), others have not been recorded previously in the literature (e.g. microlite tephra). This study provides the first comprehensive Holocene tephrostratigraphical record for northern Germany, complementing the North Atlantic tephrostratigraphical dating framework, effectively extending it into central Europe. The study shows that Icelandic ash layers are even more widespread than hitherto thought.

Description: We studied the effects of water column mixing depth and background turbidity on phytoplankton biomass, light climate, and nutrients in two field enclosure experiments designed to test predictions of a dynamical model. In 1997 and 1998, we created gradients of mixing depth by enclosing the 100-μm-filtered phytoplankton community of a phosphorus-deficient lake in cylindrical plastic bags of varying depth (1.5–15 m) which were continuously mixed. To mimic different levels of background turbidity, we surrounded the transparent enclosure walls with a layer of opaque white (1997) or black (1998) plastic. The experiments were run for 4 wk (1997) and 6 wk (1998). The results supported two key assumptions of the model: specific production and specific sedimentation losses both decreased with increasing mixing depth. At all mixing depths, fast-sinking diatoms dominated the communities. In accordance with model predictions, algal biomass concentration and standing stock (summed over the mixed layer) showed a unimodal relationship to mixing depth when background turbidity was high (1998). When background turbidity was lower (1997), only the ascending limbs of the corresponding relationships were found, which supports the prediction that the mixing depth at which biomass peaks (i.e., becomes predominantly limited by light) increases with decreasing background turbidity. Also in accordance with predictions, light intensity at the bottom of the mixed layer decreased with increasing mixing depth and with increasing background turbidity. Finally, the data supported only the ascending limbs of the predicted inverse unimodal relationships among mixing depth and dissolved inorganic and total water column phosphorus. The absence of descending limbs in these relationships at low mixing depths was probably due to deviations of the experimental systems from two model assumptions. First, the remineralization rate of sedimented phosphorus may have been too slow to equilibrate with sedimentation losses over the experimental periods. Second, biomass yield per unit nutrient (the ratio of seston carbon to phosphorus) was not constant, but decreased with increasing mixing depth. To our knowledge, these are the first field experiments in which the effects of mixing depth on phytoplankton and its resources have been investigated systematically along a large gradient.

Description: 1. The aim of this study was to estimate patchiness in biomass and in the internal nutrient status of benthic algae on hard substrata (epilithon) in Lake Erken, Sweden, over different levels of distance, depth and time. Knowledge of the sources and scale of patchiness should enable more precise estimation of epilithic biomass and nutrient status for the entire lake. We focused on the horizontal scale, about which little is known. 2. We sampled epilithon by SCUBA diving and used a hierarchical sampling design with different horizontal scales (cm, dm, 10 m, km) which were nested in two temporal scales (within and between seasons). We also compared two successive years and three sampling depths (0, 1 and 4 m). Biomass was measured as particulate carbon and chlorophyll a (Chl a) and internal nutrient status as carbon : nitrogen : phosphorus (C : N : P) ratios and as specific alkaline phosphatase activity (APA). 3. Horizontal variation accounted for 60–80 and 7–70% of the total variation in biomass and in nutrient status, respectively, at all depths and during both years. Both small and large scales accounted for significant variation. We also found variation with time and depth. Biomass increased in autumn after a summer minimum, and the within-season variation was very high. The lowest biomass was found at 0 m depth. Both N and P limitation occurred, being higher in 1996 than in 1997 and decreased with depth. 4. As a consequence, any sampling design must address variation with distance, depth and time when estimating biomass or nutrient limitation of benthic algae for an entire lake. Based on this analysis, we calculated an optimal sampling design for detecting change in the epilithic biomass of Lake Erken between different sampling days. It is important to repeat the sampling as often as possible, but also the large scales (10 m and km) and the dm scale should be replicated. Using our calculations as an example, and after a pilot study, an optimal sampling design can be computed for various objectives and for any lake. 5. Short-term impact of the wind, light and nutrient limitation, and grazing, might be important in regulating the biomass and nutrient status of epilithic algae in Lake Erken. Patchiness in the nutrient status of algae was not coupled to the patchiness of biomass, indicating that internal nutrients and biomass were regulated by different factors.

Description: Climate variations over the Northern Hemisphere are to a substantial proportion associated with the North Atlantic Oscillation (NAO). Recently, many studies revealed the impacts of the NAO on the dynamics of organisms in different ecosystems but the results in the single studies were inconsistent. Here, we used meta‐analysis techniques for a quantitative synthesis of results. We tested the influence of the NAO on the timing of life history events, on biomass of organisms, and on biomass of different trophic levels. We found a clear NAO signature in freshwater, marine, and terrestrial ecosystems. The response of life history events to the NAO was similar in all environments but less pronounced at higher latitudes. The magnitude of the biomass response was significantly related to the NAO, either positively in aquatic or negatively in terrestrial ecosystems. The response depended on longitude, the effect being less pronounced in Eastern Europe. The results stressed that a meta‐analysis is a valuable tool in the field of climate‐driven ecosystem responses and can identify more general ecological responses than single studies. We recommend the inclusion of nonsignificant results in order to archive an objective view of the strength of NAO and climate impacts in general.

Description: Modern models for the development and evolution of the geochemical heterogeneity in the Earth's mantle and the genesis of mantle magmas attach much importance to the processes of interaction between deepseated rocks and metasomatic fluids, which are able, when occurring under mantle conditions, to dissolve significant amounts of major and trace elements (see, for example, [1]). Fluorine is one of the major anions of natural fluids and also one of the principal complex-forming ligands of several metals. To evaluate the possible role of fluorine in the processes of mantle magma genesis and to identify the source of this element in natural magmas in various geodynamic environments, it is necessary to know the fluorine concentration in primitive mantle melts. These data are still relatively scarce, particularly for low alkaline magmas [2-4]. The fluorine concentrations in magmas from suprasubduction zones, whose genesis is largely controlled by the interaction between mantle rocks and fluids, remain poorly known and need further refinement. Data presented in this paper are among the first to characterize the concentrations of fluorine in primitive magmas of suprasubduction zones. These data were obtained by secondary ion mass spectrometry of chill glasses from the lava complex of the Troodos ophiolites in Cyprus. Along with information on the concentrations of major and trace elements, H2O, and Cl in the glasses, our results make it possible to utilize the example of the Troodos ophiolites to characterize the main regularities in the geochemistry of fluorine during the origin of magmas above subduction zones and to assay the contributions of various components that participated in the processes of mantle melting. These data are among the first to demonstrate that subduction-related melts became enriched in F relative to LREE.

Description: The circulation of water masses in the northeastern North Atlantic Ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes1. But the ocean circulation at depths below the reach of satellite observations is difficult to measure, and only recently have comprehensive, direct observations of whole ocean basins been possible2, 3, 4. Here we present quantitative maps of the absolute velocities at two levels in the northeastern North Atlantic as obtained from acoustically tracked floats. We find that most of the mean flow transported northward by the Gulf Stream system at the thermocline level (about 600 m depth) remains within the subpolar region, and only relatively little enters the Rockall trough or the Nordic seas. Contrary to previous work5, 6, our data indicate that warm, saline water from the Mediterranean Sea reaches the high latitudes through a combination of narrow slope currents and mixing processes. At both depths under investigation, currents cross the Mid-Atlantic Ridge preferentially over deep gaps in the ridge, demonstrating that sea-floor topography can constrain even upper-ocean circulation patterns.

Description: In this study, the water vapour transport is investigated together with cyclone tracks across the North Atlantic Ocean and their relation to the North Atlantic Oscillation, NAO. During high NAO winters, the maximum of the water vapour transport across 10°W (defined as transport towards Europe) is observed between 50° and 55°N, during low NAO winters, the maximum reduces from 160 kg/m·s to 120 kg/m·s and shifts to about 44°N. In order to understand this change the NCEP/NCAR reanalysis data (1958-1998) are used and a composite is performed of the cyclone's water vapour transport relative to the cyclone centre. The transport is strongest in the south-east sector of a cyclone. Its maximum increases with decreasing central pressure of the cyclone. Thus, deep cyclones transport more water vapour than shallow ones. During high NAO winters, deep cyclones are more frequent than in low NAO winters. Additionally, cyclone tracks are concentrated north of 55°N during high NAO winters and are rather equally distributed in meridional direction over the North Atlantic in low NAO winters. Since the water vapour content of the atmosphere over the North Atlantic increases towards the tropics, we found that during low NAO winters, the cyclones south of 55°N transport 60% more water vapour than those north of 55°N. This fact and the relation between cyclone properties and NAO can explain the shift of the maximum water vapour transport towards Europe from 55°N during high NAO winters to 44°N during low NAO winters.

Description: In late 1999, seismic and seismological investigations were carried out on the Continental margin of Costa Rica. Besides conventional wide angle refraction profiles, airgun shots were fired on a sub circular profile around Osa Peninsula into Golfo Dulce and were recorded by 20 ocean bottom hydrophones deployed along the crest of Cocos Ridge and by 13 Seismometers across the ridge. The resulting uneven distribution of shots and receivers does not allow for a full 3Dtomographic inversion. However, for selected parts detailed velocity information can be obtained providing constraints on the structure of the subsurface. Preliminary results indicate that Cocos Ridge has a bowl-shaped crustal root with a thickness of nearly 20 km in its center and only small changes along strike within the first 50 km seaward of the Middle America trench.

Description: In this modelling study the effects of cloud inhomogeneities on the observations of the passive microwave radiometer SSM/I (Special Sensor Microwave/Imager) are investigated. Brightness temperatures in the radiometer's field-of-view are calculated by using the results of a numerical cloud model as input for a 3-dimensional radiative transfer model. These brightness temperatures are compared with those obtained by the assumption of a plane parallel homogeneous cloud with the equivalent mean liquid water path (LWP). Differences between the two temperatures (the so-called 'beam-filling effect') are related to the mean LWP and to cloud inhomogeneity. It was found that not only the strength of the beam-filling effect but also its dependencies on mean LWP and its inhomogeneity are different for the different microwave frequencies. For 19 and 22 GHz the beam-filling effect increases monotonically with the mean LWP and inhomogeneity, while the beam-filling effect decreases with increased LWP at 37 and 85 GHz at large LWP. In general the beam-filling effect is more pronounced in the horizontal polarisation. Its maximum is found for 37 GHz with differences up to -60 Kelvin compared to the homogeneous case. The effect of the lowered brightness temperatures of inhomogeneous clouds in a LWP algorithm (WENG and GRODY, 1994) is analysed. The largest effect arises from decreased 37 GHz brightness temperature. The mean underestimation of LWP is 0.0179 kg/m2 and the maximum amounts to 0.7 kg/m2. In einer Modellstudie werden die Effekte von Wolkeninhomogenitäten auf die Helligkeitstemperaturen, die das passive Mikrowellenradiometer SSM/I (Special Sensor Microwave/Imager) misst, untersucht. Die Helligkeitstemperaturen im Radiometerblickwinkel werden dazu mit einem dreidimensionalen Strahlungstransportmodell für die Wolken eines numerischen Wolkenmodells berechnet. Sie werden verglichen mit Helligkeitstemperaturen plan-parallel homogener Wolken mit äquivalentem mittlerem Flüssigwasserpfad (LWP). Die Differenz dieser beiden Helligkeitstemperaturen, der sogenannte ,,Beam-Filling“ Effekt, wird untersucht bezüglich seiner Abhängigkeit vom mittleren LWP und der Wolkeninhomogenität. Dabei ergibt sich, dass nicht nur die Größe des Beam-Filling Effektes frequenzabhängig ist, sondern auch dessen Abhängigkeit von mittlerem LWP und Wolkeninhomogenität: Für 19 und 22 GHz steigt der Beam-Filling Effekt monoton mit zunehmendem LWP und Inhomogenität, wohingegen bei 37 und 85 GHz der Beam-Filling Effekt bei hohen mittleren Flüssigwassergehalten abnimmt. Insgesamt ist der Beam-Filling Effekt in der horizontalen Polarisationsebene ausgeprägter und ist maximal für 37 GHz mit einer Differenz von -60 Kelvin verglichen mit einer homogenen Wolke. Anhand eines vielfach angewendeten Algorithmus (WENG und GRODY, 1994) werden Auswirkungen von Wolkeninhomogenität auf den abgeleiteten LWP gezeigt. Dabei spiegeln sich die erniedrigten Helligkeitstemperaturen im 37 GHz Kanal besonders deutlich wider und führen zu einer mittleren Unterschätzung des LWPs von 0,0179 kg/m2 und einer maximalen Unterschätzung von 0,7 kg/m2.

Description: A backfiring weapon: The release of H2O2 by an amino acid oxidase is the early defensive reaction of the red alga Chondrus crispus against the endophytic green algal pathogen Acrochaete operculata (see scheme). This reaction can be induced by L-asparagine, which is released by the attacker when it recognises host cell-wall κ-carrageenan oligosaccharides. The induced signal of the attacker thus serves directly as the substrate for the production of the defensive metabolite.