ALBERT

Description: Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation1). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum—marked in the drill core by continuous deposition of lacustrine sediments—appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.

Description: Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages — primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria — dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms.

Description: Owing to the turbulent nature of the ocean, mesoscale eddies are omnipresent. The impact of these transitory and approximately circular sea surface temperature fronts on the overlying atmosphere is not well known. Stationary fronts such as the Gulf Stream have been reported to lead to pronounced atmospheric changes1, 2. However, the impact of transient ocean eddies on the atmosphere has not been determined systematically, except on winds and to some extent clouds3, 4, 5, 6. Here, we examine the atmospheric conditions associated with over 600,000 individual eddies in the Southern Ocean, using satellite data. We show that ocean eddies locally affect near-surface wind, cloud properties and rainfall. The observed pattern of atmospheric change is consistent with a mechanism in which sea surface temperature anomalies associated with the oceanic eddies modify turbulence in the atmospheric boundary layer. In the case of cyclonic eddies, this modification triggers a slackening of near-surface winds, a decline in cloud fraction and water content, and a reduction in rainfall. We conclude that transient mesoscale ocean structures can significantly affect much larger atmospheric low-pressure systems that swiftly pass by at the latitudes investigated.

Description: Mud diapirism has recently been recognized in several modern accretionary wedges. It provides an important means of dewatering accretionary wedges and should be regarded as an important process for producing the melanges found in both modern and ancient accretionary terranes. Mud diapirism affects a large area of the Barbados Ridge Accretionary Complex. The distribution of the mud diapirs appears to be primarily controlled by the presence of underconsolidated terrigenous submarine fan deposits that are being accreted to the complex. The frequency of diapir occurrence decreases northward as the fan becomes thinner. Mud diapirs are absent from the very eastern most part of the complex formed from sediments accreted at its toe, with the exception of a few mud volcanoes on the ocean floor in front of the complex. The initiation of diapirism appears to be spatially coincident with the onset of subcretion, or underplating, of sediment to the base of the complex at a ramp between two levels of decollement. It is proposed that the release of mud and pore water from the subcreted sediments is a direct or indirect cause of most of the mud diapirism in the accretionary complex. There is a range of diapiric form dependent on the viscosity of the mud, from mud volcanoes fed by low viscosity mud, to higher viscosity mud ridges. The diapirs in the eastern areas of the complex are generally mud volcanoes with narrow conduits feeding a surface mound. Mud ridges are prominent in the western parts of the complex. This is interpreted as reflecting a general westward decrease in the fluid content of the accretionary complex. Bottom-simulating seismic reflectors formed by gas hydrate are commonly developed in the areas of mud volcano occurrences. The presence of the hydrate indicates that large volumes of methane are being generated at depth in these regions. The generation of methane may be contributing to zones of overpressuring in the wedge. Methane may also be partly responsible for driving the diapiric material to the surface to form mud volcanoes. Ridges in the subducting oceanic crust beneath the accretionary complex locally enhance diapirism above their crests and southern flanks. Faults formed later in the development of the complex are more commonly associated with diapirism than those resulting from accretion at the toe of the wedge. These later faults play an important role in controlling the sites of individual mud volcanoes, chains of mud volcanoes, and mud ridges.

Description: The cuttlefish ingests much skeleton from the crustaceans and fish it preys upon. The skeletal pieces are relatively large and their dimensions bear a close relationship to the length of the buccal mass and diameter of the oesophagus. The structures of the buccal mass are instrumental in the breakdown of prey and orientation of long pieces of skeleton to ensure their entry into the oesophagus. Many pieces of skeletal material present in the stomach contents still have attached muscles, showing that there is little, or no, external digestion. Skeletal material may be important for long-term maintenance of young Sepia in captivity.

Description: The cartilaginous tubercles of the mantle of the squid Cranchia scabra have been examined with the scanning electron microscope. Some tubercles are small, simple nodules whereas others are large with a complex Maltese cross form. The varying shapes and sizes probably represent a developmental sequence. The possible role of the tubercles is discussed.

Description: An influence of solar irradiance variations on Earth’s surface climate has been repeatedly suggested, based on correlations between solar variability and meteorological variables1. Specifically, weaker westerly winds have been observed in winters with a less active sun, for example at the minimum phase of the 11-year sunspot cycle2, 3, 4. With some possible exceptions5, 6, it has proved difficult for climate models to consistently reproduce this signal7, 8. Spectral Irradiance Monitor satellite measurements indicate that variations in solar ultraviolet irradiance may be larger than previously thought9. Here we drive an ocean–atmosphere climate model with ultraviolet irradiance variations based on these observations. We find that the model responds to the solar minimum with patterns in surface pressure and temperature that resemble the negative phase of the North Atlantic or Arctic Oscillation, of similar magnitude to observations. In our model, the anomalies descend through the depth of the extratropical winter atmosphere. If the updated measurements of solar ultraviolet irradiance are correct, low solar activity, as observed during recent years, drives cold winters in northern Europe and the United States, and mild winters over southern Europe and Canada, with little direct change in globally averaged temperature. Given the quasiregularity of the 11-year solar cycle, our findings may help improve decadal climate predictions for highly populated extratropical regions

Description: Three specimens of the rare giant squid (genus Architeuthis, 18 nominal species) are described from the waters around southern Africa. Consideration of their internal and external morphology, including beaks, radula, statocyst and statolith give no reason to suppose that the three specimens do not pertain to the same species. A standardized data collection form and a summary of existing morphometric data are presented for the first time and the morphology and systematics of the genus are discussed. The value of various systematic characters is examined and certain guidelines are proposed, with an appeal for a more scientific approach to Architeuthis studies. Features of the internal anatomy, including the female reproductive tract, are described and illustrated and the beak dimensions are used to evaluate existing regression formulae for beak and body parameters. The statocyst and statolith are described and illustrated in full, the statolith for the first time, and are compared with those of other squids. The value of recent data from trawl-caught specimens, as well as indirect evidence, is cited to replace speculation in discussions on distribution and habitat. Our specimens suggest that the waters off the south-western coast of Africa may be one of the natural habitats of Architeurhis, during both feeding and spawning periods of the life cycle.

Description: Investigations indicate that the Iceland Ice Sheet was reduced in size during MIS 3 but readvanced to the shelf break at the LGM. Retreat occurred very rapidly around 15 k–16 k cal. yr BP. By contrast, the margin of the ice sheet on the East Greenland shelf, north of the Denmark Strait, was at or close to the shelf break during MIS 3 and 2 and retreat starting ∼17 k cal. yr BP. Quantitative X-ray diffraction analysis of the 〈2 mm sediment fraction was undertaken on 161 samples from Iceland and East Greenland diamictons, and from cores on the slopes and margins of the Denmark Strait. Weight% mineralogical data are used in a principal component analysis to differentiate sediments derived from the two margins. The first two PC axes explain 52% of the variance. These associations are used to characterise sediments as being affiliated with (a) Iceland, (b) East Greenland or (c) mixed. The contribution from Iceland becomes prominent during MIS 2. The extensive outcrop of early Tertiary basalts on East Greenland between 68° and 71° N is an alternative source for basaltic clasts and North Atlantic sediments with εNd(0) values close to ±0.

Description: The anaerobic oxidation of methane (AOM) with sulphate, an area currently generating great interest in microbiology, is accomplished by consortia of methanotrophic archaea (ANME) and sulphate-reducing bacteria1, 2. The enzyme activating methane in methanotrophic archaea has tentatively been identified as a homologue of methyl-coenzyme M reductase (MCR) that catalyses the methane-forming step in methanogenic archaea3, 4. Here we report an X-ray structure of the 280 kDa heterohexameric ANME-1 MCR complex. It was crystallized uniquely from a protein ensemble purified from consortia of microorganisms collected with a submersible from a Black Sea mat catalysing AOM with sulphate4. Crystals grown from the heterogeneous sample diffract to 2.1 Å resolution and consist of a single ANME-1 MCR population, demonstrating the strong selective power of crystallization. The structure revealed ANME-1 MCR in complex with coenzyme M and coenzyme B, indicating the same substrates for MCR from methanotrophic and methanogenic archaea. Differences between the highly similar structures of ANME-1 MCR and methanogenic MCR include a F430 modification, a cysteine-rich patch and an altered post-translational amino acid modification pattern, which may tune the enzymes for their functions in different biological contexts.

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: The living coelacanth Latimeria chalumnae has a unique position in world biodiversity which raises important questions about conservation and ethics. Some relevant details of coelacanth biology are summarized, including those obtained by direct observation from submersibles. The importance of the coelacanth for evolutionary theory and palaeontology is shown to be paralleled in cultural, literary and artistic areas of human heritage. Threats to the Comoran coelacanths from artisanal fishing are described and conservation measures discussed in relation to local customs and economies as well as the promotion of tourism to spread a new awareness and concern for coelacanths worldwide.

Description: Iron limits phytoplankton growth and hence the biological carbon pump in the Southern Ocean1. Models assessing the impacts of iron on the global carbon cycle generally rely on dust input and sediment resuspension as the predominant sources2, 3. Although it was previously thought that most iron from deep-ocean hydrothermal activity was inaccessible to phytoplankton because of the formation of particulates4, it has been suggested that iron from hydrothermal activity5, 6, 7 may be an important source of oceanic dissolved iron8, 9, 10, 11, 12, 13. Here we use a global ocean model to assess the impacts of an annual dissolved iron flux of approximately 9×108 mol, as estimated from regional observations of hydrothermal activity11, 12, on the dissolved iron inventory of the world’s oceans. We find the response to the input of hydrothermal dissolved iron is greatest in the Southern Hemisphere oceans. In particular, observations of the distribution of dissolved iron in the Southern Ocean3 (Chever et al., manuscript in preparation; Bowie et al., manuscript in preparation) can be replicated in our simulations only when our estimated iron flux from hydrothermal sources is included. As the hydrothermal flux of iron is relatively constant over millennial timescales14, we propose that hydrothermal activity can buffer the oceanic dissolved iron inventory against shorter-term fluctuations in dust deposition.

Description: Biological N2 fixation is an important part of the marine nitrogen cycle as it provides a source of new nitrogen that can support biological carbon export and sequestration. Research in the past decade has focused on determining the patterns of distribution and abundance of diazotrophs, defining the environmental features leading to these patterns and characterizing the factors that constrain marine N2 fixation overall. In this Review, we describe how variations in the deposition of iron from dust to different ocean basins affects the limiting nutrient for N2 fixation and the distribution of different diazotrophic species. However, many questions remain about marine N2 fixation, including the role of temperature, fixed nitrogen species, CO2 and physical forcing in controlling N2 fixation, as well as the potential for heterotrophic N2 fixation.

Description: Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present-day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked-eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under-saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma-Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight 14C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.

Description: To enable quality control of measurement procedures for determinations of Mg isotope amount ratios, expressed as δ26Mg and δ25Mg values, in Earth-surface studies, the δ26Mg and δ25Mg values of eight reference materials (RMs) were determined by inter-laboratory comparison between five laboratories and considering published data, if available. These matrix RMs, including river water SLRS-5, spring water NIST SRM 1640a, Dead Sea brine DSW-1, dolomites JDo-1 and CRM 512, limestone CRM 513, soil NIST SRM 2709a and vegetation NIST SRM 1515 apple leaves, are representative for a wide range of Earth-surface materials from low-temperature environments. The inter-laboratory variability, 2s (twice the standard deviation), of all eight RMs ranges from 0.05 to 0.17‰ in δ26Mg. Thus, it is suggested that all these materials are suitable for validation of δ26Mg and δ25Mg determinations of Earth-surface geochemical studies.

Description: The relationship between the biomass of reproductively mature individuals (spawning stock) and the resulting offspring added to the population (recruitment), the stock–recruitment relationship, is a fundamental and challenging problem in all of population biology. The steepness of this relationship is commonly defined as the fraction of recruitment from an unfished population obtained when the spawning stock biomass is 20% of its unfished level. Since its introduction about 20 years ago, steepness has become widely used in fishery management, where it is usually treated as a statistical quantity. Here, we investigate the reproductive ecology of steepness, using both unstructured and age‐structured models. We show that if one has sufficient information to construct a density‐independent population model (maximum per capita productivity and natural mortality for the unstructured case or maximum per capita productivity, natural mortality and schedules of size and maturity at age for the structured model) then one can construct a point estimate for steepness. Thus, steepness cannot be chosen arbitrarily. If one assumes that the survival of recruited individuals fluctuates within populations, it is possible, by considering the early life history, to construct a prior distribution for steepness from this same demographic information. We develop the ideas for both compensatory (Beverton–Holt) and over‐compensatory (Ricker) stock–recruitment relationships. We illustrate our ideas with an example concerning bluefin tuna (Thunnus thynnus/orientalis, Scombridae). We show that assuming that steepness is unity when recruitment is considered to be environmentally driven is not biologically consistent, is inconsistent with a precautionary approach, and leads to the wrong scientific inference (which also applies for assigning steepness any other single value).

Description: This paper presents a temperature reconstruction of the past 1000 years for Central Europe, based on chronological records. The advantages and limitations of this hermeneutic, text-based approach are discussed and the statistic methodology is introduced. Historical documents represent direct observation of weather and atmospheric conditions with highest temporal resolution available and precise dating. A major advantage of these extensive data is that they allow the reconstruction of large numbers of variables such as winter temperature, precipitation, pressure patterns or climate extremes as well as floods or storms. Within this hermeneutic climatological research approach, even human impacts and social dimensions of climate development can be examined. In order to quantify the historical information, statistical methods are applied, based on an index approach.

Description: Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993–2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System.

Description: Although rising global sea levels will affect the shape of coastlines over the coming decades1, 2, the most severe and catastrophic shoreline changes occur as a consequence of local and regional-scale processes. Changes in sediment supply3 and deltaic subsidence4, 5, both natural or anthropogenic, and the occurrences of tropical cyclones4, 5 and tsunamis6 have been shown to be the leading controls on coastal erosion. Here, we use satellite images of South American mangrove-colonized mud banks collected over the past twenty years to reconstruct changes in the extent of the shoreline between the Amazon and Orinoco rivers. The observed timing of the redistribution of sediment and migration of the mud banks along the 1,500 km muddy coast suggests the dominant control of ocean forcing by the 18.6 year nodal tidal cycle7. Other factors affecting sea level such as global warming or El Niño and La Niña events show only secondary influences on the recorded changes. In the coming decade, the 18.6 year cycle will result in an increase of mean high water levels of 6 cm along the coast of French Guiana, which will lead to a 90 m shoreline retreat.

Description: Some of the basic assumptions implied in the theory of limiting similarity of coexisting competitors were investigated experimentally in the case of three congeneric, deposit feeding snails. The species show character displacement with respect to size when coexisting. In experimental containers with a natural substrate, interspecific, exploitative competition between snails of the same size range is as intense as intraspecific competition. Diatoms of a given size range, which constitute the most important food, show a "logistic" growth response to grazing, and individual growth of the snails is linearly related to diatom density. The previous observation that the snails show size dependent selection for ingested particle sizes is extended to show that this mechanism leads to a real resource partitioning between snails of different sizes. Size frequency distribution of diatoms in the sediment is a function of the sizes of grazing snails. Size selection of ingested sand grains may also be significant for resource partitioning since the migration rate of the attached microflora between sand grains seems to be slow relative to its growth on the individual sand grains.

Description: The total length, the dorsal mantle length and the weight of the lens of Octopus vulgaris Lamarck have been related to the live body weight. The effect of fixation on the body weight and dorsal mantle length has been tested on six small octopuses.

Description: THE rare deep-sea octopod Cirrothauma murrayi Chun 1910 was first described from a single specimen caught during the Michael Sars Expedition of 1910 (ref. 1). Until now it has been caught only four more times2. We describe here three specimens of this species that were recently caught during biological cruises of RRS Discovery (Fig. 1). All of these animals, including the Discovery ones, have been caught at depths of more than 1,500 m, except one that was dip-netted through the ice of the Arctic Ocean3.

Description: The dry weight and the crest length of the upper and lower beak, the length of the radula ribbon, the average width of the base of the six proximal and distal rachidian teeth as well as the total number of these teeth have all been related to the live body weight of octopuses between 1.1 and 4440 g. From any one of these parameters it is possible to estimate the size and approximate age of the animal.

Description: Naturally produced polybrominated diphenyl ethers (PBDEs) pervade the marine environment and structurally resemble toxic man-made brominated flame retardants. PBDEs bioaccumulate in marine animals and are likely transferred to the human food chain. However, the biogenic basis for PBDE production in one of their most prolific sources, marine sponges of the order Dysideidae, remains unidentified. Here, we report the discovery of PBDE biosynthetic gene clusters within sponge-microbiome-associated cyanobacterial endosymbionts through the use of an unbiased metagenome-mining approach. Using expression of PBDE biosynthetic genes in heterologous cyanobacterial hosts, we correlate the structural diversity of naturally produced PBDEs to modifications within PBDE biosynthetic gene clusters in multiple sponge holobionts. Our results establish the genetic and molecular foundation for the production of PBDEs in one of the most abundant natural sources of these molecules, further setting the stage for a metagenomic-based inventory of other PBDE sources in the marine environment.

Description: Features of the brain of this oceanic squid have been investigated and related, as far as possible, to its habits and mode of life. The body and arms are much vacuolated for buoyancy and the animal probably lives with the head upwards. The very long whip-like tentacles are not vacuolated and perhaps hang downwards. They are covered by numerous minute pedunculated suckers, perhaps providing a sticky surface. A special nerve running outside the brain carries signals from the arms and tentacles to the magnocellular lobe, which is very large and of complex structure. However, there are no giant cells and the mantle is weak. Propulsion is mainly by the large fins, which are controlled from the magnocellular lobe, presumably using the information from the arms and tentacles.

Description: Benthoctopus piscatorum appears to be a multiple spawner. In the ovary of one specimen about 50 eggs were found at various stages of development.

Description: The Pacific sector of Antarctica, including both the Antarctic Peninsula and continental West Antarctica, has experienced substantial warming in the past 30 years. An increase in the circumpolar westerlies, owing in part to the decline in stratospheric ozone concentrations since the late 1970s, may account for warming trends in the peninsula region in austral summer and autumn. The more widespread warming in continental West Antarctica (Ellsworth Land and Marie Byrd Land) occurs primarily in austral winter and spring, and remains unexplained. Here we use observations of Antarctic surface temperature and global sea surface temperature, and atmospheric circulation data to show that recent warming in continental West Antarctica is linked to sea surface temperature changes in the tropical Pacific. Over the past 30 years, anomalous sea surface temperatures in the central tropical Pacific have generated an atmospheric Rossby wave response that influences atmospheric circulation over the Amundsen Sea, causing increased advection of warm air to the Antarctic continent. General circulation model experiments show that the central tropical Pacific is a critical region for producing the observed high latitude response. We conclude that, by affecting the atmospheric circulation at high southern latitudes, increasing tropical sea surface temperatures may account for West Antarctic warming through most of the twentieth century.

Description: Meiobenthos densities and higher taxon composition were studied in an active gas seepage area at depths from 182 to 252 m in the submarine Dnieper Canyon located in the northwestern part of the Black Sea. The meiobenthos was represented by Ciliata, Foraminifera, Nematoda, Polychaeta, Bivalvia, Gastropoda, Amphipoda, and Acarina. Also present in the sediment samples were juvenile stages of Copepoda and Cladocera which may be of planktonic origin. Nematoda and Foraminifera were the dominant groups. The abundance of the meiobenthos varied between 2397 and 52,593 ind.·m−2. Maximum densities of Nematoda and Foraminifera were recorded in the upper sediment layer of a permanent H2S zone at depths from 220 to 250 m. This dense concentration of meiobenthos was found in an area where intense methane seeps were covered by methane-oxidizing microbial mats. Results suggest that methane and its microbial oxidation products are the factors responsible for the presence of a highly sulfidic and biologically productive zone characterized by specially adapted benthic groups. At the same time, an inverse correlation was found between meiofauna densities and methane concentrations in the uppermost sediment layers. The hypothesis is that the concentration of Nematoda and Foraminifera within the areas enriched with methane is an ecological compromise between the food requirements of these organisms and their adaptations to the toxic H2S.

Description: Zircon is a common mineral in continental crustal rocks. As it is not easily altered in processes such as erosion or transport, this mineral is often used in the reconstruction of geological processes such as the formation and evolution of the continents. Zircon can also survive under conditions of the Earth’s mantle, and rare cases of zircons crystallizing in the mantle significantly before their entrainment into magma and eruption to the surface have been reported1,2,3. Here we analyse the isotopic and trace element compositions of large zircons of gem quality from the Eger rift, Bohemian massif, and find that they are derived from the mantle. (U–Th)/He analyses suggest that the zircons as well as their host basalts erupted between 29 and 24 million years ago, but fragments from the same xenocrysts reveal U–Pb ages between 51 and 83 million years. We note a lack of older volcanism and of fragments from the lower crust, which suggests that crustal residence time before eruption is negligible and that most rock fragments found in similar basalts from adjacent volcanic fields equilibrated under mantle conditions. We conclude that a specific chemical environment in this part of the Earth’s upper mantle allowed the zircons to remain intact for about 20–60 million years.

Description: Two discontinuous tephra layers were discovered at Burney Spring Mountain, northern California. Stratigraphic relationships suggest that they are two distinct primary fall tephras. The geochemistries of these tephras from electron probe microanalysis were compared with those of known layers found in the area to test for potential correlations, using clustering analysis on geochemistry. In most cases, geochemical data from a tephra layer can be assigned to a single cluster, but in some cases the analyses are spread over several clusters. This spreading is a direct result of mixing and reworking of several tephra layers. The mixing, in turn, appears to be related to the influence of wind in a marshy environment.

Description: Four primary glass populations, well defined by their Sr, Ba and Y concentrations, occur in the Youngest Toba Tuff (YTT), which was deposited during a Supereruption of the Toba caldera complex in northern Sumatra 75 ka. Average concentrations of major and trace elements indicate a coherent, systematic Variation of glass composition across populations. No clear pattern in the areal distribution of these four glass groups can be discerned. The multiple glass populations of the YTT easily distinguish it from the single homogeneous glass population of the Middle Toba Tuff (~500 ka), as represented by its basal vitrophyre, and that of the Oldest Toba Tuff (~800 ka), as represented by ash Layer D at the Ocean Drilling Program site 758 in the Indian Ocean.

Description: The synthetic production of monodisperse single magnetic domain nanoparticles at ambient temperature is challenging. In nature, magnetosomes--membrane-bound magnetic nanocrystals with unprecedented magnetic properties--can be biomineralized by magnetotactic bacteria. However, these microbes are difficult to handle. Expression of the underlying biosynthetic pathway from these fastidious microorganisms within other organisms could therefore greatly expand their nanotechnological and biomedical applications. So far, this has been hindered by the structural and genetic complexity of the magnetosome organelle and insufficient knowledge of the biosynthetic functions involved. Here, we show that the ability to biomineralize highly ordered magnetic nanostructures can be transferred to a foreign recipient. Expression of a minimal set of genes from the magnetotactic bacterium Magnetospirillum gryphiswaldense resulted in magnetosome biosynthesis within the photosynthetic model organism Rhodospirillum rubrum. Our findings will enable the sustainable production of tailored magnetic nanostructures in biotechnologically relevant hosts and represent a step towards the endogenous magnetization of various organisms by synthetic biology.

Description: THE Sierra Leone Rise, located in the east equatorial Atlantic, forms a discontinuous chain of seamounts as shallow as 2 km extending with a general NE–SW trend from near the Sierra Leone coast of Africa, to the St Paul fracture zone near the Mid-Atlantic Ridge (Fig. 1). The origin of this feature has remained a topic of discussion. Sheridan et al.1 have hypothesised that the Sierra Leone Rise is a volcanic structure formed at the beginning of the opening of the Atlantic in the early Cretaceous period. The twin features of the Sierra Leone and the Ceara Rises are probably of oceanic origin and were created 80 Myr ago or later in their present-day position with respect to Africa and South America2. The Atlantic ocean exhibits several similar aseismic structures which appear symmetrically oriented with respect to the mid-oceanic ridge, such as the Walvis–Rio Grande Rise and the Iceland Faeroes–Iceland Greenland Ridges. These structures are volcanic edifices having a composition similar to that found in their associated islands3–7. Deep sea drilling of the Ceara Rise8,9 penetrated a basaltic basement of the upper Cretaceous period (Maestrichtian) (Leg 39, Site 354). Similarly, a DSDP hole (Leg 41, Site 366) on the Sierra Leone Rise, penetrated sediments of the same period, without reaching basement10. We report here the discovery of alkali-rich volcanics in an area of the Sierra Leone Rise. The sediment overlying the rock fragments is aged ∼45 Myr.

Description: Fisheries advice is based on demographic calculations, which assume that density-dependent processes regulating recruitment occur only in early life. This assumption is challenged by laboratory and lake studies and some recent indications from marine systems that demonstrate density-dependent regulation late in life. By accounting for spatial dynamics of a population, something that has previously been ignored in models of fish, we show that density-dependent regulation is determined by the size of the habitat: in small habitats, for example small lakes, regulation occurs late in life, while it can occur early in large habitats. When regulation happens late in life, fisheries yield is maximized by exploitation of mainly juvenile fish, while exploiting mature fish maximizes yield if regulation happens early. We review and interpret observations of density dependence in the light of the theory. Our results challenge the current assumption that density dependence always occurs early in life and highlights the need for an increased understanding of density-dependent processes. This can only come about by a change of focus from determining stock-recruitment relationships towards understanding when and how density-dependent regulation occurs in nature.

Description: Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages — primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria — dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms.

Description: RECENT advances in 40Ar/39Ar dating1,2 have made it possible to date individual K-feldspar grains from Pleistocene tephra, a capability that greatly improves the reliability and temporal resolving power of the method. Here we apply these new techniques to the dating of a phonolite tephra from the East Eifel volcanic field in West Germany, which is sandwiched between loess and palaeosol (alfisol) deposits, and which was therefore erupted during the transition from a glacial to an interglacial period. Our age estimate for this transition is 215±4 kyr (1 σ), which has important implications for the marine δ18O timescale and for models of global climate change during the Pleistocene. The results show that single-grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits. This technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine δ18O timescale for more rigorous Fourier analysis testing of the Milankovitch hypothesis.

Description: The relationship between the biomass of reproductively mature individuals (spawning stock) and the resulting offspring added to the population (recruitment), the stock–recruitment relationship, is a fundamental and challenging problem in all of population biology. The steepness of this relationship is commonly defined as the fraction of recruitment from an unfished population obtained when the spawning stock biomass is 20% of its unfished level. Since its introduction about 20 years ago, steepness has become widely used in fishery management, where it is usually treated as a statistical quantity. Here, we investigate the reproductive ecology of steepness, using both unstructured and age‐structured models. We show that if one has sufficient information to construct a density‐independent population model (maximum per capita productivity and natural mortality for the unstructured case or maximum per capita productivity, natural mortality and schedules of size and maturity at age for the structured model) then one can construct a point estimate for steepness. Thus, steepness cannot be chosen arbitrarily. If one assumes that the survival of recruited individuals fluctuates within populations, it is possible, by considering the early life history, to construct a prior distribution for steepness from this same demographic information. We develop the ideas for both compensatory (Beverton–Holt) and over‐compensatory (Ricker) stock–recruitment relationships. We illustrate our ideas with an example concerning bluefin tuna (Thunnus thynnus/orientalis, Scombridae). We show that assuming that steepness is unity when recruitment is considered to be environmentally driven is not biologically consistent, is inconsistent with a precautionary approach, and leads to the wrong scientific inference (which also applies for assigning steepness any other single value).

Description: Stock‐based and ecosystem‐based indicators are used to provide a new diagnosis of the fishing impact and environmental status of European seas. In the seven European marine ecosystems covering the Baltic and the North‐east Atlantic, (i) trends in landings since 1950 were examined; (ii) syntheses of the status and trends in fish stocks were consolidated at the ecosystem level; and (iii) trends in ecosystem indicators based on landings and surveys were analysed. We show that yields began to decrease everywhere (except in the Baltic) from the mid‐1970s, as a result of the over‐exploitation of some major stocks. Fishermen adapted by increasing fishing effort and exploiting a wider part of the ecosystems. This was insufficient to compensate for the decrease in abundance of many stocks, and total landings have halved over the last 30 years. The highest fishing impact took place in the late 1990s, with a clear decrease in stock‐based and ecosystem indicators. In particular, trophic‐based indicators exhibited a continuous decreasing trend in almost all ecosystems. Over the past decade, a decrease in fishing pressure has been observed, the mean fishing mortality rate of assessed stocks being almost halved in all the considered ecosystems, but no clear recovery in the biomass and ecosystem indicators is yet apparent. In addition, the mean recruitment index was shown to decrease by around 50% in all ecosystems (except the Baltic). We conclude that building this kind of diagnosis is a key step on the path to implementing an ecosystem approach to fisheries management.

Description: Teleost fish grow continuously throughout their lifespan, and this growth includes visual system components: eyes, optic nerves, and brain. As fish grow, the optic nerve lengthens and neural signals must travel increasing distances from the eye to the optic tectum along thousands of retinal ganglion cell (RGC) axons. Larger fish have better vision that enhances their ability to capture prey, but they are faced with the potential computational problem of changes in the relative timing of visual information arriving at the brain. Optic nerve conduction delays depend on RGC axon conduction velocities, and velocity is primarily determined by axon diameters. If axon diameters do not increase in proportion to body length, then absolute and relative conduction delays will vary with fish size. We have measured optic nerve lengths and axon diameter distributions in different sized zebrafish (Danio rerio) and goldfish (Carassius auratus) and find that, as both species of fish grow, axon diameters increase to reduce average conduction delays by about half and to keep relative delays constant. This invariance of relative conduction delays simplifies computational problems faced by the optic tectum.

Description: The spatial structure of species is important for their dynamics and evolution, but also for management and conservation. There are numerous ways of inferring spatial structures, and information from multiple methods is becoming more common to examine how different processes shape the spatial structures of species to improve fish management. Here, we investigate the spatial structure of a suite of Baltic Sea fish species based on the following: (i) spatial (presumably neutral) genetic differentiation, reviewed from the literature, and (ii) spatial synchrony in abundance changes from time series of fishery‐independent surveys, which we currently find to be underused given the amount of data available. For each of these two methods, species were classified as having a distinct, continuous or no/weak spatial structure. In addition, based on each source of information, we estimated the spatial scale of management units for species. The results show that only among species confined to the coastal zone the two sources of information yielded a congruence of the spatial structure (displaying a continuous spatial structure). In contrast, offshore species show weak spatial genetic structure but stronger spatial structure of synchrony in abundance. Based on this, we suggest that population genetic structure and synchrony in abundance should be used as complementary information as they reflect different spatial processes and suggest that management actions should differ with respect to scale depending on the management targets applied. We propose similar analysis should be applied to areas outside the Baltic Sea, and other stock identification methods, to improve management of fish resources.

Description: As sessile filter feeders, sponges rely on a highly efficient fluid transport system. Their physiology depends on efficient water exchange, which is performed by the aquiferous system. This prominent poriferan anatomical character represents a dense network of incurrent and excurrent canals on which we lack detailed 3D models. To overcome this, we investigated the complex leucon‐type architecture in the demosponge Tethya wilhelma using corrosion casting, microtomography, and 3D reconstructions. Our integrative qualitative and quantitative approach allowed us to create, for the first time, high‐resolution 3D representations of entire canal systems which were used for detailed geometric and morphometric measurements. Canal diameters lack distinct size classes, and bifurcations are non‐uniformly ramified. A relatively high number of bifurcations show previously unknown and atypical cross‐sectional area ratios. Scaling properties and topological patterns of the canals indicate a more complex overall architecture than previously assumed. As a consequence, it might be more convenient to group canals into functional units rather than hierarchical clusters. Our data qualify the leucon canal system architecture of T. wilhelma as a highly efficient fluid transport system adapted toward minimal flow resistance. Our results and approach are relevant for a better understanding of sponge biology and cultivation techniques.

Description: We report U–Pb zircon ages of c. 700–550 Ma, 262–220 Ma, 47–38 Ma and 15–14 Ma from amphibolites on Naxos Island in the Aegean extensional province of Greece. The zircon has complex internal structures. Based on cathodoluminescence response, zoning and crosscutting relationships a minimum of four zircon growth stages are identified: inherited core, magmatic core, inner metamorphic (?) rim and an outer metamorphic rim. Trace element compositions of the amphibolites suggest igneous differentiation and crustal assimilation. Zircon solubility as a function of saturation temperatures, Zr content and melt composition indicates that the zircon did not originally crystallize in the mafic bodies but was inherited from felsic precursor rocks, and subsequently assimilated into the mafic intrusives during emplacement. Zircon inheritance is corroborated by the complex, xenocrystic nature of the zircon in one sample. Ages of c. 700–550 Ma and 262–220 Ma are assigned to inherited zircon. Available geochemical data suggest that the 15–14 Ma metamorphic rims grew in situ in the amphibolites, corresponding to a high-grade metamorphic event at this time. However, the geochemical data cannot conclusively establish if the c. 40 Ma zircon rims also grew in situ, or whether they were inherited along with the xenocrystic cores. Two scenarios for emplacement of the mafic intrusives are discussed: (i) Intrusion during late-Triassic to Jurassic ocean basin development of the Aegean realm, in which case the 40 Ma zircon rims would have grown in situ, and (ii) emplacement in the Miocene as a result mafic underplating during large-scale extension. In this case, only the 15–14 Ma metamorphic outer rims would have formed in situ in the amphibolitic host rocks.

Description: The diet of King Penguins Aptenodytes patagonica at Possession Island was studied in February 1989 by analysis of 20 stomach contents collected from adult birds, just before they fed their single chicks. The mean mass of the samples was 1.84 kg, equivalent to 15% of the unladen adult body-mass. Fish accounted for 99.8% and squids for 0.2% by mass. The main prey were mesopelagic myctophid fish which live in dense shoals and perform a daily vertical migration. Subadults/adults of Electrona carlsbergi and juveniles and subadults/adults of Krefftichthys anderssoni represented 73.7 and 13.4% of the diet by mass, respectively. No difference was found in the diet of male and female King Penguins. Comparison of individual samples suggests that these birds catch a large quantity of fish from only a limited number of shoals. The mean caloric content of the food was 7 kJ/g wet mass. The total energy requirement of each chick during its initial period of growth was estimated to amount to 328,000 kJ, equivalent to 55 kg of food. The rate at which energy was delivered to the chick was calculated to be 50 W during this period.

Description: In Loligo forbesi Steenstrup, the female reproductive system consists of the ovary and accessory reproductive organs which include the oviducal gland, the nidamental gland, the accessory nidamental gland and seminal receptacle. Histological studies were made on the accessory reproductive organs of female L. forbesi. The various changes observed during maturation are described and the functional significance discussed. The secretions produced by the oviducal gland and nidamental gland apparently form the egg coats. The seminal receptacle serves to store spermatozoa after mating. The function of the accessory nidamental gland is unknown.

Description: Vertebrates have evolved a sophisticated adaptive immune system that relies on an almost infinite diversity of antigen receptors that are clonally expressed by specialized immune cells that roam the circulatory system. These immune cells provide vertebrates with extraordinary antigen-specific immune capacity and memory, while minimizing self-reactivity. Plants, however, lack specialized mobile immune cells. Instead, every plant cell is thought to be capable of launching an effective immune response. So how do plants achieve specific, self-tolerant immunity and establish immune memory? Recent developments point towards a multilayered plant innate immune system comprised of self-surveillance, systemic signalling and chromosomal changes that together establish effective immunity.

Description: An automatic food dispenser was designed for use with Octopus vulgaris Lamarck. One live crab was delivered each time the octopus pulled a white shape attached to the dispenser. The apparatus provided a continuous record of the time and frequency of feeding over periods of up to 15 days.

Description: To survey hepatitis B virus (HBV) integration in liver cancer genomes, we conducted massively parallel sequencing of 81 HBV-positive and 7 HBV-negative hepatocellular carcinomas (HCCs) and adjacent normal tissues. We found that HBV integration is observed more frequently in the tumors (86.4%) than in adjacent liver tissues (30.7%). Copy-number variations (CNVs) were significantly increased at HBV breakpoint locations where chromosomal instability was likely induced. Approximately 40% of HBV breakpoints within the HBV genome were located within a 1,800-bp region where the viral enhancer, X gene and core gene are located. We also identified recurrent HBV integration events (in ≥4 HCCs) that were validated by RNA sequencing (RNA-seq) and Sanger sequencing at the known and putative cancer-related TERT, MLL4 and CCNE1 genes, which showed upregulated gene expression in tumor versus normal tissue. We also report evidence that suggests that the number of HBV integrations is associated with patient survival.

Description: WHILE ammonites and all other ectocochleate cephalopods became extinct, nautiloids survived relatively unchanged from the Ordovician, suggesting that they are unusually well adapted to their niche. Here we obtain high-resolution tracks of Nautilus positions and depths, combined with telemetered jet pressures, which clarify both its lifestyle and economics. Nautilus is more active in nature than in captivity1, but its energy costs are lower than projected2,3. Viewing Nautilus as 'vertic', rather than benthic, resolves this contradiction. Records show that the cost of transport is the same in any direction within a vertical plane. Living on a reef face swept by a lateral current means that vertical movements4,5 sample large areas for chemical trails. A detected trail can be followed upcurrent in the slow-moving boundary layer, but no effort is wasted on horizontal movement without good prospects for food; long-range movements are downcurrent and made by drifting. Once fed, a Nautilus can reduce its energy costs by moving to deeper, cooler waters, where a single meal can last for months.

Description: Whether the study of external morphology can increase our knowledge of shallow-water octopuses and their biology is tested by multivariate morphometric analyses. The extent of morphological variation among 20 species from the Atlantic and eastern tropical Pacific Oceans is explored, and four hypotheses are addressed: (1) that octopuses show secondary sexual dimorphism; (2) that remote, ostensibly conspecific populations are morphologically distinct; (3) that morphometric characters contribute to resource partitioning among sympatric species; and (4) that morphology is predictably associated with habitat. Results of principal components analysis show most species to be very similar in shape. Arm length contributes most shape variation; other characters contribute little. Principal components and size-free discriminant analyses refute each of the hypotheses considered. The morphological similarity of isolated Atlantic populations may be a symplesiomorphy, but information on the planktonic phase of the octopus lire cycle supports the possibility of dispersal across the Atlantic Ocean. Size, not directly treated here, may significantly affect some aspects of octopus biology. Increased female size may evolve due to selection for increased fecundity and intraspecific niche partitioning. Size may also indicate interaction within and among species. Characters of shape, deemed essential to species descriptions, do not appear to be able to identify most specimens, nor to increase our understanding of octopus biology.

Description: The tephrostratigraphy of lake sediments in the Endinger Bruch provides the first robust age model for the Lateglacial palynological records of Vorpommern (north-east Germany). Cryptotephra investigations revealed six tephra layers within sediments spanning from Open vegetation phase I (∼Bølling, ∼15 ka) to the Early Holocene Betula/Pinus forest phase (∼Pre-boreal, ∼10.5 ka). Four of these layers have been correlated with previously described tephra layers found in sites across Europe. The Laacher See Tephra (Eifel Volcanic Field) is present in very high concentrations within sediments of the Lateglacial Betula (/Pinus) forest phase (∼Allerød). The Vedde Ash (Iceland) lies midway through Open vegetation phase III (∼Younger Dryas). The Hässeldalen and the Askja tephras (Iceland) lie in the Early Holocene Betula/Pinus forest phase (∼Preboreal). These tephra layers have independently derived age estimates, which have been imported into the Endinger Bruch record. Furthermore, the layers facilitate direct correlation of the regional vegetation record with other palaeoenvironmental archives, which contain one or more of the same tephra layers, from Greenland to Southern Europe. In doing this, localized variations are confirmed in some aspects of the pollen stratigraphy; however, transitions between the main vegetation phases appear to occur synchronously (within centennial errors) with the equivalent environmental transitions observed in sites across the European continent.

Description: Climate warming at the end of the last glaciation caused ice caps on Icelandic volcanoes to retreat. Removal of surface ice load is thought to have decreased pressures in the underlying mantle, triggering decompression melting, enhanced magma generation and increased volcanic activity1–3. Present-day climate change could have the same effect, although there may be a time lag of hundreds of years between magma generation and eruption4,5. However, in addition to increased magma generation, pressure changes associated with ice retreat should also alter the capacity for storing magma within the crust. Here we use a numerical model to evaluate the effect of the current decrease in ice load on magma storage in the crust at the Kverkfjöll volcanic system, located partially beneath Iceland’s largest ice cap. We compare the model results with radar and global positioning system measurements of surface displacement and changes in crustal stress between 2007 and 2008, during the intrusion of a deep dyke at Upptyppingar. We find that although the main component of stress recorded during dyke intrusion relates to plate extension, another component of stress is consistent with the stress field caused by the retreating ice cap. We conclude that the retreating ice cap led to enhanced capture of magma within the crust. We suggest that ice-cap retreat can promote magma storage, rather than eruption, at least in the short term.

Description: Here we present a tephrostratigraphic record (core Co1202) recovered from the northeastern part of Lake Ohrid (Republics of Macedonia and Albania) reaching back to Marine Isotope Stage (MIS) 6. Overall ten horizons (OT0702-1 to OT0702-10) containing volcanic tephra have been recognised throughout the 14.94m long sediment succession. Four tephra layers were visible at macroscopic inspection (OT0702-4, OT0702-6, OT0702-8 and OT0702-9), while the remaining six are cryptotephras (OT0702-1, OT0702-2, OT0702-3, OT0702-5, OT0702-7 and OT0702-10) identified from peaks in K, Zr and Sr intensities, magnetic susceptibility measurements, and washing and sieving of the sediments. Glass shards of tephra layers and cryptotephras were analysed with respect to their major element composition, and correlated to explosive eruptions of Italian volcanoes. The stratigraphy and the major element composition of tephra layers and cryptotephras allowed the correlation of OT0702-1 to AD 472 or AD 512 eruptions of Somma-Vesuvius, OT0702-2 to the FL eruption of Mount Etna, OT0702-3 to the Mercato from Somma-Vesuvius, OT0702-4 to SMP1-e/Y-3 eruption from the Campi Flegrei caldera, OT0702-5 to the Codola eruption (Somma-Vesuvius or Campi Flegrei), OT0702-6 to the Campanian Ignimbrite/Y-5 from the Campi Flegrei caldera, OT0702-7 to the Green Tuff/Y-6 eruption from Pantelleria Island, OT0702-8 to the X-5 eruption probably originating from the Campi Flegrei caldera, OT0702-9 to the X-6 eruption of generic Campanian origin, and OT0702-10 to the P-11 eruption from Pantelleria Island. The fairly well-known ages of these tephra layers and parent eruptions provide new data on the dispersal and deposition of these tephras and, furthermore, allow the establishment of a chronological framework for core Co1202 for a first interpretation of major sedimentological changes.

Description: The elemental stoichiometry of sea water and particulate organic matter is remarkably similar. This observation led Redfield to hypothesize that the oceanic ratio of nitrate to phosphate is controlled by the remineralization of phytoplankton biomass1. The Redfield ratio is used universally to quantitatively link the marine nitrogen and phosphorus cycles in numerous biogeochemical applications2,3,4. Yet, empirical and theoretical studies show that the ratio of nitrogen to phosphorus in phytoplankton varies greatly with taxa5,6 and growth conditions7,8,9. Here we present a dynamic five-box ecosystem model showing that non-Redfield utilization of dissolved nitrogen and phosphorus by non-nitrogen-fixing phytoplankton controls the magnitude and distribution of nitrogen fixation. In our simulations, systems dominated by rapidly growing phytoplankton with low nitrogen to phosphorus uptake ratios reduce the phosphorus available for nitrogen fixation. In contrast, in systems dominated by slow-growing phytoplankton with high nitrogen to phosphorus uptake ratios nitrogen deficits are enhanced, and nitrogen fixation is promoted. We show that estimates of nitrogen fixation are up to fourfold too high when non-Redfield uptake stoichiometries are ignored. We suggest that the relative abundance of fast- and slow-growing phytoplankton controls the amount of new nitrogen added to the ocean.

Description: Microorganisms produce a wealth of structurally diverse specialized metabolites with a remarkable range of biological activities and a wide variety of applications in medicine and agriculture, such as the treatment of infectious diseases and cancer, and the prevention of crop damage. Genomics has revealed that many microorganisms have far greater potential to produce specialized metabolites than was thought from classic bioactivity screens; however, realizing this potential has been hampered by the fact that many specialized metabolite biosynthetic gene clusters (BGCs) are not expressed in laboratory cultures. In this Review, we discuss the strategies that have been developed in bacteria and fungi to identify and induce the expression of such silent BGCs, and we briefly summarize methods for the isolation and structural characterization of their metabolic products.

Description: This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake-level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial–early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north-central Italy). On the basis of an age–depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas–Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700–11 650 cal. yr BP. Four sub-millennial scale cooling phases were recognised from pollen data at ca. 14 300–14 200, 13 900–13 700, 13 400–13 100 and 11 350–11 150 cal. yr BP. The last three may be Mediterranean equivalents to the Older Dryas (GI-1d), Intra-Allerød (GI-1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice-core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra-Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake-level record shows that the sub-millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2 ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd.

Description: Populations of fishes provide valuable services for billions of people, but face diverse and interacting threats that jeopardize their sustainability. Human population growth and intensifying resource use for food, water, energy and goods are compromising fish populations through a variety of mechanisms, including overfishing, habitat degradation and declines in water quality. The important challenges raised by these issues have been recognized and have led to considerable advances over past decades in managing and mitigating threats to fishes worldwide. In this review, we identify the major threats faced by fish populations alongside recent advances that are helping to address these issues. There are very significant efforts worldwide directed towards ensuring a sustainable future for the world's fishes and fisheries and those who rely on them. Although considerable challenges remain, by drawing attention to successful mitigation of threats to fish and fisheries we hope to provide the encouragement and direction that will allow these challenges to be overcome in the future.

Description: The onset of the Palaeocene/Eocene thermal maximum (about 55 Myr ago) was marked by global surface temperatures warming by 5–7 °C over approximately 30,000 yr (ref. 1), probably because of enhanced mantle outgassing2, 3 and the pulsed release of approx1,500 gigatonnes of methane carbon from decomposing gas-hydrate reservoirs4, 5, 6, 7. The aftermath of this rapid, intense and global warming event may be the best example in the geological record of the response of the Earth to high atmospheric carbon dioxide concentrations and high temperatures. This response has been suggested to include an intensified flux of organic carbon from the ocean surface to the deep ocean and its subsequent burial through biogeochemical feedback mechanisms8. Here we present firm evidence for this view from two ocean drilling cores, which record the largest accumulation rates of biogenic barium—indicative of export palaeoproductivity—at times of maximum global temperatures and peak excursion values of delta13C. The unusually rapid return of delta13C to values similar to those before the methane release7 and the apparent coupling of the accumulation rates of biogenic barium to temperature, suggests that the enhanced deposition of organic matter to the deep sea may have efficiently cooled this greenhouse climate by the rapid removal of excess carbon dioxide from the atmosphere.

Description: The stomach contents of 1522 adult seals (Arctocephalus pusillus pusillus) and 673 pups, which were collected around the West and South Coasts of Southern Africa, were examined and cephalopod prey identified. About 20 cephalopod species (some identifications were uncertain) were found in the stomachs, of which only six were significant: Loligo vulgaris reynaudii. Sepia spp., Octopus sp., Todaropsis eblanae, Todarodes angolensis and Ocythoe tuberculata. This list suggests that A. pusillus feeds exclusively on the continental shelf, frequently on or near the bottom. Among adults, cephalopod prey varied in importance around the coast. It was most important on the South Coast of South Africa where it comprised 35.0% of the weight of all prey, of which L. v. veynaudii constituted about 88%. On the West Coast cephalopods comprised about 26.6% by weight of all prey, and Octopus sp. predominated, whereas in Namibian waters cephalopods were least important, constituting only 3.4% by weight of all prey, with Todarodes angolensis and Octopus sp. being most significant. Among pups (aged 8–10 months) in the Lüderitz (Namibia) area, cephalopods were about 16.9% of prey by weight, of which Ocythoe tuberculata, small Sepia spp. and Octopoda were most important.

Description: The movements of the isolated buccal mass of Octopus vulgaris have been investigated. The beaks undergo rhythmic cycles of activity in the absence of applied stimulation and after electrical stimulation of the inter-buccal connective. Initial opening, closing, retraction and re-opening phases of movement are described. This cycle of movements is taken to resemble those in the intact animal. Anatomical and electrical evidence identifies the superior mandibular muscle as being partly responsible for the closing and retraction phases of movement. The inferior buccal ganglion determines the sequence of these buccal movements, but modification by sensory feed-back from the musculature is also implied. The preparation will allow a closer comparison of the control of movement in cephalopods and gastropods.

Description: The structure of the reproductive systems of mature males and females of the nektonic, oceanic squid Thysanoteuthis rhombus are described. The main peculiarities of the female system are relatively low capacity oviducts, set in a tight spiral, and hypertrophically developed oviducal glands with a very large second section. The male reproductive system is characterized by a long, narrow Needham's sac containing 10–15 large spermatophores 80–100 mm in length. The mesentery supporting the gonad, and protruding into it dorsally, is a characteristic feature in both sexes. The hectocotylus structure differs markedly from that in other squids and resembles that of sepiids. The reproductive system of T. rhombus possesses primitive features (pattern of gonad attachment and hectocotylus) but mostly secondary characters (small oviducts, very large oviducal glands and ovary). The complex morpho-ecological adaptations of T. rhombus are reflected in the distinctive features of the reproductive system.

Description: Seasonal variation in the diet of common seals (Phoca vitulina) in the Moray Firth, north-east Scotland, was determined from analysis of faecal samples collected at haul-out sites during each month of 1988. Data on diet of common seals in 1987 are also presented. Limitations of the methods available for quantification of diet are discussed. Although some of the observed variation in diet from month to month may reflect changes in the sampling regime, a clear seasonal pattern was apparent, with clupeids predominating in the winter and sandeels in the summer. The trends observed are consistent with opportunistic feeding on the most abundant Prey.

Description: The cephalopod fauna collected during six surveys carried out in the bathyal basin of the north-western Mediterranean is discussed. Samples were taken at depths mainly between 1000 and 2000 m. Ten species were identified. Bathypolypus sponsalis and Neorossia caroli were the commonest species. Small individuals of both these species occurred at greater depths than did larger individuals, suggesting up-slope ontogenetic migration. The depth ranges recorded for all species collected are discussed and compared to the results of previous studies found in the literature.

Description: Taonius megalops is a neutrally buoyant oceanic squid, very different in form when young and old. The young, has a round, sac-like mantle and relatively long tentacles, while the adult has an elongated cone-like mantle and relatively short tentacles. The transition in shape and form is gradual and has been followed in animals of between 3 and 180 mm dorsal mantle length. Statistical tests on various parameters investigated, both external and internal, revealed good correlation with the dorsal mantle length and confirmed the descriptions of the development of the chromatophores and subocular light organs with growth. It was concluded that these animals, captured in the Atlantic Ocean, all belonged to the species T. megalops Prosch 1849. This study has permitted us to suggest a tentative outline of the life cycle, although no adults were present in the material available.

Description: A crab which has been captured and paralysed by an octopus but retrieved 1 1/2 min later cannot at first be pulled apart by the experimenter: 27 min later it can be dismembered easily. This demonstrates that there is external digestion when Octopus vulgaris feeds upon crabs. However, it is strictly limited at this stage to the arthrodial membrane and the musculo-skeletal attachment mechanisms as the exoskeleton separates at the joints allowing the muscles to be drawn out of the appendages. And yet, two hours after capture, pieces of crab meat are still recognizable in the octopus's stomach. The process of paralysing and cleaning a crab was noticeably slowed after the surgical removal of the radula, salivary papilla or the lateral buccal palps.

Description: The changes in body weight of 12 octopuses, fed on fish or crabs, were followed under laboratory conditions for periods of 1 to 7 1/2 months. The food intake was estimated and compared with the changes in body weight of the octopuses; 25 to 55% of the total intake of food appeared to be incorporated. The range of the average increase in weight over the whole observation period of each of the animals was 1.9 to 7.7g per day (1 to 7 1/2 months); the mean value was 4.8g per day. The effect of changing the diet of small octopuses (fish or crab)was followed for four weeks but there was no evidence that alteration of the diet affected the rate of changes in body weight of animals of more than 47g initial body weight.

Description: Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens ( Lichina confinis and L. pygmaea ; from intertidal and subtidal zones) and one littoral lichen ( Roccella fuciformis ; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria.

Description: Scattered groups of these ancient fish may all stem from a single remote population. Coelacanths were discovered in the Comoros archipelago to the northwest of Madagascar in 1952. Since then, these rare, ancient fish have been found to the south off Mozambique, Madagascar and South Africa, and to the north off Kenya and Tanzania — but it was unclear whether these are separate populations or even subspecies. Here we show that the genetic variation between individuals from these different locations is unexpectedly low. Combined with earlier results from submersible and oceanographic observations1, 2, our findings indicate that a separate African metapopulation is unlikely to have existed and that locations distant from the Comoros were probably inhabited relatively recently by either dead-end drifters or founders that originated in the Comoros.

Description: Hundreds of Sepia officinalis were hatched and cultured through the life cycle in each of 13 populations. Two genetic lines were maintained: one for an unprecedented seven generations and another presently in its fourth. All generations—save one—produced animals in excess of 1·0 kg body weight. Seven of eight generations with adequate data records had mean weights of 1–2 kg, and the largest cuttlefish reared were a male 2·6 kg and a female 2·9 kg. Fecundity levels were high, but there was a trend towards decreased fertility in later generations, with fertilization rates dropping below 10%. In the 7th generation, most mature animals failed to engage in agonistic courtship and mating behaviour. Almost no normal eggs were laid and none was fertile, thus ending the lineage. Most culture took place at 20–24°C and temperature generally explained variations in life span duration: being of shorter length at higher temperatures. Life spans were consistently longer at 20°C and sizes were greater than predicted from previously published literature. In both lines there was a trend towards larger individuals and longer life spans in subsequent generations. Survival of hatchlings typically exceeded 90% for two months post-hatching, and survival averaged 50% or higher to sexual maturity when corrected for animals removed from the populations for experimental use.

Description: Japanese flounder, Paralichthys olivaceus, is an economically important marine fish species in Asia. A suite of 18 microsatellite markers chosen from published genetic linkage maps was used to carry out parentage assignments of 188 hatchery-reared juveniles from a small number of breeders. The probabilities of exclusion for the 18 microsatellite markers were 0.604–0.913, and the effectiveness of combined probability of exclusion reached 100% when using the eight microsatellite markers with higher Excl 1 probabilities. The cultured and wild stocks (WSs) were differentiated in a release-recapture population based on these markers. Of the 321 recaptured offspring, 28.34% were assigned to their parental pairs in our broodstock, whereas the remaining offspring could not be traced back to a possible sire or dam. Significant reduction in genetic diversity of the cultured stock (CS) had not been found compared with that of the WS. The results suggest that CSs released into the wild will not adversely affect the genetic structure of natural populations. Our results demonstrate that these markers provide an efficient tool for parentage assignments and genetic analysis of Japanese flounder.

Description: Living coelacanths (Latimeria chalumnae) are normally found only in the western Indian Ocean, where they inhabit submarine caves in the Comores Islands. Two specimens have since been caught off the island of Manado Tua, north Sulawesi, Indonesia, some 10,000 kilometres away. We sought to determine the ecological and geographic distribution of Indonesian coelacanth populations with a view to drawing up conservation measures for this extremely rare fish. During our explorations, we discovered two living Indonesian coelacanths 360 km southwest of Manado Tua.

Description: The exponentially increasing number of sequenced genomes necessitates fast, accurate, universally applicable and automated approaches for the delineation of prokaryotic species. We developed specI (species identification tool; http://www.bork.embl.de/software/specI/), a method to group organisms into species clusters based on 40 universal, single-copy phylogenetic marker genes. Applied to 3,496 prokaryotic genomes, specI identified 1,753 species clusters. Of 314 discrepancies with a widely used taxonomic classification, 〉62% were resolved by literature support.

Description: There have been decades, such as 2000–2009, when the observed globally averaged surface-temperature time series shows little increase or even a slightly negative trend1 (a hiatus period). However, the observed energy imbalance at the top-of-atmosphere for this recent decade indicates that a net energy flux into the climate system of about 1 W m−2 (refs 2, 3) should be producing warming somewhere in the system4,5. Here we analyse twenty-first-century climate-model simulations that maintain a consistent radiative imbalance at the top-of-atmosphere of about 1 W m−2 as observed for the past decade. Eight decades with a slightly negative global mean surface-temperature trend show that the ocean above 300 m takes up significantly less heat whereas the ocean below 300 m takes up significantly more, compared with non-hiatus decades. The model provides a plausible depiction of processes in the climate system causing the hiatus periods, and indicates that a hiatus period is a relatively common climate phenomenon and may be linked to La Niña-like conditions.

Description: Managing fisheries presents trade-offs between objectives, for example yields, profits, minimizing ecosystem impact, that have to be weighed against one another. These trade-offs are compounded by interacting species and fisheries at the ecosystem level. Weighing objectives becomes increasingly challenging when managers have to consider opposing objectives from different stakeholders. An alternative to weighing incomparable and conflicting objectives is to focus on win–wins until Pareto efficiency is achieved: a state from which it is impossible to improve with respect to any objective without regressing at least one other. We investigate the ecosystem-level efficiency of fisheries in five large marine ecosystems (LMEs) with respect to yield and an aggregate measure of ecosystem impact using a novel calibration of size-based ecosystem models. We estimate that fishing patterns in three LMEs (North Sea, Barents Sea and Benguela Current) are nearly efficient with respect to long-term yield and ecosystem impact and that efficiency has improved over the last 30 years. In two LMEs (Baltic Sea and North East US Continental Shelf), fishing is inefficient and win–wins remain available. We additionally examine the efficiency of North Sea and Baltic Sea fisheries with respect to economic rent and ecosystem impact, finding both to be inefficient but steadily improving. Our results suggest the following: (i) a broad and encouraging trend towards ecosystem-level efficiency of fisheries; (ii) that ecosystem-scale win–wins, especially with respect to conservation and profits, may still be common; and (iii) single-species assessment approaches may overestimate the availability of win–wins by failing to account for trade-offs across interacting species.

Description: Mass fractions of Sn and In were determined in sixteen geological reference materials including basaltic/mafic (BCR‐2, BE‐N, BHVO‐1, BHVO‐2, BIR‐1, OKUM, W‐2, WS‐E), ultramafic (DTS‐2b, MUH‐1, PCC‐1, UB‐N) and felsic/sedimentary reference materials (AGV‐2, JA‐1, SdAR‐M2, SdAR‐H1). Extensive digestion and ion exchange separation tests were carried out in order to provide high yields (〉 90% for Sn, 〉 85% for In), low total procedural blanks (~ 1 ng for Sn, 〈 3 pg for In) and low analytical uncertainties for the elements of interest in a variety of silicate sample matrices. Replicate analyses (n = 2–13) of Sn‐In mass fractions give a combined measurement uncertainty of 2u that are generally 〈 3% and in agreement with literature data, where available. We present the first high precision In data for reference materials OKUM (32.1 ± 1.5 ng g−1), DTS‐2b (2.03 ± 0.25 ng g−1), MUH‐1 (6.44 ± 0.30 ng g−1), and PCC‐1 (3.55 ± 0.35 ng g−1) as well as the first Sn data for MUH‐1 (0.057 ± 0.010 μg g−1) and DTS‐2b (0.623 ± 0.018 μg g−1).

Description: As the complex interplay of forces in the ocean responds to climate change, the dynamics of global ocean circulation are shifting.

Description: Conceptual models predict a unimodal effect of consumer abundance on prey diversity with the highest diversity at intermediate consumer abundance (intermediate disturbance hypothesis). Consumer selectivity and prey productivity are assumed to be further important determinants. Preferential grazing on dominant prey species favoured by high nutrient supply is supposed to increase prey diversity, whereas the effect of consumers on prey diversity may be negative under low nutrient conditions (grazer reversal hypothesis). We tested the effect of four common consumers the isopod Idotea baltica, the amphipod Gammarus oceanicus, and the gastropods Littorina littorea and Rissoa membranacea on diversity and composition of epiphytes growing on eelgrass Zostera marina. Consumer density was manipulated (four levels: grazer free control, low, medium, high) based on abundances observed in eelgrass systems. Additionally, we manipulated nutrient supply (three levels) and the presence of Idotea in a factorial experiment. The impact of consumer abundance on epiphyte diversity varied depending on consumer identity and epiphyte evenness was affected rather than species number in this short-term experiment. Idotea reduced epiphyte diversity (Shannon-Wiener index H') and Gammarus increased epiphyte diversity. Littorina had no effect at low and medium abundance, but a negative effect in the high density treatment. Only Rissoa supported the conceptual models as it caused the proposed unimodal pattern in epiphyte diversity. The varying species-specific selectivity of the studied consumers is likely to explain their diverse impact on epiphyte diversity. Nutrients enhanced epiphyte diversity at medium enrichment, whereas higher nutrient supply reduced epiphyte diversity. The effect of Idotea changed from negative at low nutrient concentration to positive at higher nutrient supply, supporting the grazer reversal hypothesis. This study implies that consumer species identity and nutrient concentrations are important in controlling prey diversity and composition. Different consumer selectivity and changes in selectivity with growing consumer abundance and nutrient concentration are the causal factors for this effect.

Description: The fields of immunology, microbiology, nutrition and metabolism are rapidly converging. Here we expand on a diet-microbiota model as the basis for the greater incidence of asthma and autoimmunity in developed countries.

Description: To the Editor: We congratulate Halsey et al. for their important discussion of the random nature of P values in an earlier issue of this journal1. P values from identical experiments can differ greatly in a way that is surprising to many2, 3, 4, 5, 6. The failure to appreciate this…

Description: The mammalian gastrointestinal tract, the site of digestion and nutrient absorption, harbors trillions of beneficial commensal microbes from all three domains of life. Commensal bacteria, in particular, are key participants in the digestion of food, and are responsible for the extraction and synthesis of nutrients and other metabolites that are essential for the maintenance of mammalian health. Many of these nutrients and metabolites derived from commensal bacteria have been implicated in the development, homeostasis and function of the immune system, suggesting that commensal bacteria may influence host immunity via nutrient- and metabolite-dependent mechanisms. Here we review the current knowledge of how commensal bacteria regulate the production and bioavailability of immunomodulatory, diet-dependent nutrients and metabolites and discuss how these commensal bacteria–derived products may regulate the development and function of the mammalian immune system.

Description: To the Editor: Mass spectrometry–based proteomics has become an important component of biological research. Numerous proteomics methods have been developed to identify and quantify the proteins in biological and clinical samples1, identify pathways affected by endogenous and exogenous perturbations2 and characterize protein complexes3. Despite successes, the interpretation of vast proteomics data…

Description: Marine Upper Jurassic sediments have recently been reported from South Africa (Knysna Outlier, Cape Province) for the first time1. They occur as shallow water, sandy clays (Brenton Beds) in association with terrestrial/fluviatile conglomerates and sandstones, which were deposited in an approximately east-west elongate intermontane basin between the Cape Fold mountains (formed of Lower Palaeozoic sediments). Post-Cretaceous erosion has reduced the original deposits to a series of small, isolated outliers, only two of which have been reported to contain marine sediments (Knysna, lower Upper Jurassic; Algoa, Valanginian2) (Fig. 1). Extensive Neocomian-Maas-trichtian outcrops are known from the continental shelf off to the south of South Africa3, and a complete mid-Jurassic to Upper Cretaceous marine succession is suspected on the Agulhas Bank infilling and overlying east-west striking, fault bounded folds of Lower Palaeozoic Cape Supergroup rocks as shown in Fig. 1 (R. V. D., in preparation and refs. 1 and 4).

Description: A SIMPLE model for continental basement structures at rifted continental margins comprises large fault blocks which trend approximately parallel to, and step down towards, the continental–ocean boundary (for example, see ref. 1). These blocks may be cut by faults which strike across the margin, and, in many theoretical discussions, are shown as being separated from the true oceanic crust by an intermediate zone (see transitional crust of Fig. 3, ref. 2). On many rifted margins these features are deeply buried by young sediments and cannot be stutied in detail. On Goban Spur (Fig. 1), a marginal plateau south-west of Ireland, the young sediment cover is abnormally thin, however, and we have been able to map in detail a 150 km wide continental basement fracture pattern of horsts and grabens using a simple seismic reflection system (160 inch3 air-gun and two-channel hydrophone array). We also suggest a location for the continent–ocean boundary between the Spur and Porcupine Abyssal Plain. There are few previously published data from Goban Spur relevant to our study, although valuable sampling3 and geophysical3–5 results have been obtained north and south of the area.

Description: In bacteria, foreign nucleic acids are silenced by clustered, regularly interspaced, short palindromic repeats (CRISPR)--CRISPR-associated (Cas) systems. Bacterial type II CRISPR systems have been adapted to create guide RNAs that direct site-specific DNA cleavage by the Cas9 endonuclease in cultured cells. Here we show that the CRISPR-Cas system functions in vivo to induce targeted genetic modifications in zebrafish embryos with efficiencies similar to those obtained using zinc finger nucleases and transcription activator-like effector nucleases.

Description: Hurricanes and other strong storms can cause important decreases in sea surface temperature by means of vertical mixing within the upper ocean, and by air–sea heat exchange. Here we use satellite-derived infrared images of the western North Atlantic to study sea surface cooling caused by hurricane Gloria (1985). Significant regional variations in sea surface cooling are well correlated with hydrographic conditions. The greatest cooling (up to 5°C) occurred in slope waters north of the Gulf Stream where the seasonal thermocline is shallowest and most compressed; moderate cooling (up to 3 °C) occurred in the open Sargasso Sea where the thermocline is deeper and more diffused; little or no cooling occurred in shallow coastal waters (bottom depth less than 20 m) which were isothermal before the passage of hurricane Gloria. There is a pronounced right-side asymmetry of sea surface cooling with stronger (by a factor of 4) and more extensive (by a factor of 3) cooling found on the right side of the hurricane track. These qualitative results are consistent with the notion that vertical mixing within the upper ocean is the dominant sea surface cooling mechanism of hurricanes.

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.