ALBERT

Description: The sexual cycle of the cuttlefish, Sepia officinalis, from the northern part of the Bay of Biscay was followed over several years (1988 to 1990 and 1992 to 1993). Sucessive maturity stages are reached at the same time regardless of site in the northern part of the Bay. In this area, the majority of cuttlefish reproduce during their second year of life (group II) whereas the remainder reproduce in their first year (group I). The first visible signs of sexual development concern the testis in males and the genital tract in females. Males mature earlier than females: the first spermatophores appear in July (group II) and October (group I) while mature eggs appear from December (group II) and March (group I). The breeding season lasts from about mid-March to late June (3.5 months).

Description: Statolith microstructure was studied in two abundant planktonic cranchiids, Cranchia scabra (56 specimens, 38-127mm mantle lengh, ML) and Liocranchia reinhardti (34 specimens, 99-205mm ML) sampled in epipelagic waters of the western part of the Gulf of Guinea (tropical Atlantic). Growth increments were revealed in ground statoliths of both species. It was possible to distinguish two growth zones in statolith microstructure by their colour in reflected light of the microscope: the translucent postnuclear zone and pale white opaque zone. Assuming that growth increments in statoliths were produced daily, ages of the largest immature C. scabra and L. reinhardti were 166 and 146 days, respectively. Both cranchiids are fast-growing squids with growth rates in length resembling those of juveniles of tropical ommastrephids and Thysanoteuthis rhombus. Liocranchia reinhardti grows faster: its growth rate in ML is approximately twice that of same-aged C. scabra. The life cycle of both cranchiids consists of two phases. During their epipelagic phase, C. scabra and L. reinhardti feed and grow rapidly from paralarvae to immature young in the epipelagic waters, attaining 120-130 and 170-200 mm ML by ages of 4-5 months, respectively. Then they change their life style to a deepwater phase.

Description: Parsimony analysis of 29 finned and finless octopod taxa considered 66 anatomical and morphological characters to discover synapomorphies that unite monophyletic groups. The resultant cladogram (177 equally parsimonious trees at 191 steps, CI 0.429) resolved all relationships except those among the 16 exemplars of the Octopodidae included and those among Tremoctopus, Ocythoe and Argonauta. Bootstrap values of over 90% support the monophyly of the finned and finless octopods, relationships among the finned octopods, the bolitaenids and the monophyly of Haliphron, Tremoctopus, Ocythoe and Argonauta; bootstrap values for other nodes range from 57 to 79%. Among finned octopods, specimens representing Grimpoteuthis are basal, as Voss (1988a) suggested. Specimens of Opisthoteuthis represent a distinct lineage, and are sister taxon, in this analysis, of Cirroteuthis (although specimens of Stauroteuthis could not be included). New definitions of the genera Opisthoteuthis and Grimpoteuthis are provided to reflect their separate evolutionary histories rather than their overt morphological similarity. Among finless octopods, bolitaenids are basal. The monophyletic Octopodidae is the sister taxon to the clade containing the sister taxa Vitreledonella and Amphitretus, and Haliphron, Tremoctopus, Ocythoe and Argonauta. The Ctenoglossa and Heteroglossa, families grouped by shared radular dentition, are diphyletic and paraphyletic, respectively. The cladistic relationships demonstrate that both the Vitrele-donellidae and Idioctopodidae are junior synonyms of the Amphitretidae; despite conspicuous morphological differences separating these taxa, they share a recent evolutionary history.

Description: Length-frequency data on squid (Loligo forbesi) collected during trawling surveys in Scottish waters from 1980 to 1994 were analysed to describe temporal and spatial patterns in abundance and to examine the prospects for using survey abundance to forecast fishery abundance. Loligo was patchily distributed in space and time. Distribution patterns in the North Sea in February appeared to be strongly related to bottom temperature (squid avoided waters 〈7°C) and, to a lesser extent, salinity (more squid in more saline water). For other areas and times, no temperature or salinity data were available, but there were trends for squid on the west coast to be more abundant in westerly areas and higher latitudes, and for squid at Rockall to be more abundant in shallow water. Inter-annual trends in abundance differed between the North Sea, west coast and Rockall, but average survey abundances for the North Sea and west coast tended to be positively correlated. For the North Sea and west coast, survey abundance was positively correlated with fishery abundance for the same month and area, and average abundance for the February North Sea survey was a reasonable predictor of commercial CPUE in the autumn of the same year (the peak of the fishery). Some of the observed trends were consistent with the existence of a stock-recruitment relationship but may indicate that abundance in a given calendar year is linked to climatic factors.

Description: The microstructure, morphology and ontogenetic development of statoliths and age and growth of 405 planktonic paralarvae and 117 juveniles belonging to 10 species of gonatid squids (Cephalopoda, Oegopsida) were studied in the region of the continental slope in the western part of the Bering Sea (57°00′–61°30′N, 163°00′E–179°20′W). The statolith microstructure of all species was characterized by the presence of a large droplet-shaped nucleus and bipartite postnuclear zone divided into two by the first stress check, except for Berryteuthis magister which had only one stress check and an undivided postnuclear zone. In Gonatus spp., completion of development of the postnuclear zone coincided with full development of the central hook on the tentacular club. Daily periodicity of statolith growth increments was validated by maintaining 13 paralarvae of the four most abundant species in captivity. All species might be subdivided into two groups based on statolith microstructure, i.e. species with a central position of the nucleus within the first statolith check (Gonatopsis spp., Egonatus tinro and B.magister) and species with the nucleus shifted to the inner side of the first statolith check (Gonatus spp.). Comparative analysis of statolith morphology showed that paralarval statoliths have species-specific characters that allowed the construction of keys to identify species of gonatid paralarvae based on their statoliths. Analysis of paralarval growth using statoliths revealed that these cold-water planktonic gonatid paralarvae have fast growth rates, attaining a mantle length of 7–10 mm at 15–20 days and 20–25 mm at 35–70 days.

Description: An investigation was carried out on the recently discovered ‘giant’ extra large (XL) form of the squid Sthenoteuthis oualaniensis from the Arabian Sea. The sample consisted of 2 males, which have not been previously described, and 13 females. Diet composition, parasite loading, sucker ring dentition, biolumi-nescence and sexual dimorphism were examined and compared to known parameters of the medium (M) form. Reproductive strategy, potential fecundity, egg size distribution in the ovary and oviducts were examined in mature XL females. Evidence of multiple spawning in the giant form was also investigated. Overall body shape, bioluminescent structures and coloration of the giant form were similar to the M form, though the XL form had a smaller fin angle than the M form. The mature female XL form has a dorsal mantle length about twice that of a mature female M form. Adult females of the XL form have a dorsal mantle length about twice that of adult males of the same form. Differences between males and females were found in arm sucker ring dentition and parasite load, suggesting a difference in diet. This could be linked to size differences between the sexes. A strong correlation between ovary mass and mantle length was found (r2 = 0.64). Poor correlation was found between mantle length and oviduct mass (r2 = 0.128) and potential fecundity (r2 = 0.07). Potential fecundity ranged between 2–5 million eggs and the holding capacity of the oviducts was approximately 300, 000 eggs. This combined with the presence of spermatangia and the presence of food in the stomach suggest that the XL form is a multiple spawner. S. oualaniensis appears to have a plastic phenotype and has adapted to the Arabian Sea conditions by evolving the capacity to grow to a giant size.

Description: Stomach contents of a resident community of bottlenose dolphins (Tursiops truncatus) from the Sarasota Bay area of the westcentral coast of Florida were studied to examine potential factors leading to patterns of habitat use. Composition and size of prey were analyzed and correlated with feeding behavior of individual dolphins of known histories. Examination of stomach contents of 16 stranded dolphins revealed a diet composed exclusively of fish (15 species), most of which were associated with seagrasses in varying degrees. Observational records for 21 years showed that feeding typically occurred in shallow (2–3 m) waters and in the vicinity of seagrasses in 23% of cases. Dolphins usually fed alone or in small groups and on non-obligate schooling prey. The main species of prey were soniferous, an indication that passive listening may be important in detection of prey. The close agreement between species of fishes represented in stomach contents and habitat of prey, as indicated by observations of feeding, suggests that analysis of stomach contents is a reasonable approach for studying prey and feeding patterns of dolphins. Meadows of seagrass are one of the habitats of importance to dolphins in the Sarasota Bay area, and their protection is important for conservation of these animals.

Description: Osmotic adaption by halophilic and halotolerant bacteria is generally achieved by the accumulation or synthesis of several organic solutes. Accumulation by uptake from the medium is preferred over biosynthesis. The chemical nature of the major solute is important in determining the degree of osmotolerance of the organism. Glycine betaine accumulation confers a greater degree of osmotolerance than proline, which in turn confers more osmotolerance than glutamate accumulation. The occurrence and uptake of these solutes in a variety of eubacteria is reviewed.

Description: Age composition and growth rates of the squid Loligo vulgaris (Lamark, 1797) were studied by examination of growth increments within statoliths of 419 specimens (mantle length, ML, ranging from 32 to 400mm). The squid were obtained by monthly sampling from the catches of commercial trawls off southern Portugal between March and September, 1993. The total number of growth increments in the mounted and ground statoliths was counted using a semi-automatic image analysis system. ML was significantly correlated with both the statolith length, TSL and the number of increments, NI. The female statolith was slightly larger than the male statolith for the same mantle size. Growth rates of individuals showed high variability with an average estimated at 34.6mm month-1 for males and 33.5mm month-1 for females. Growth in length between 70 and 280 days was best described by a power function for both sexes. The growth index of the statolith (TSL/NI) decreased with individual growth. The result may be related with the onset of sexual maturation. L. vulgaris hatched throughout the year with two distinct peaks, in spring which is the main breeding period, and in autumn. The life cycle of the L. vulgaris population on the south Portugese shelf was completed in one year.

Description: A study of individual and group growth rates based on a method of growth determination using the gladius was carried out in two populations of the purple-back flying squid (Sthenoteuthis oualaniesis) in the Arabian Sea. The duration of the life cycle in all populations and size groups examined was approximately one year. The growth pattern of linear increase was either slightly S-shaped or almost linear, while growth in weight followed a power-type pattern. Generally, females grew faster than males. Use of the gladius as a recording structure makes it possible to study the real growth of a specimen, rather than the statistical correlation of length/weight versus age, as in the commonly used statolith method. Analysis of individual growth rates in large-sized sawning females revealed growth rhythm with roughly a one-month periodicity in which phases of rapid growth (17-21 days; 1.6-3,6mm per day) alternate with phases of slow growth (12-14 days; 0.4-1.2mm per day). This new method is simple to use and may be applied even on board a vessel during research cruises.

Description: Intense bottom-ice algal blooms, often dominated by diatoms, are an important source of food for grazers, organic matter for export during sea ice melt, and dissolved organic carbon. Sea-ice diatoms have a number of adaptations, including accumulation of compatible solutes, that allows them to inhabit this highly variable environment characterized by extremes in temperature, salinity, and light. In addition to protecting them from extreme conditions, these compounds present a labile, nutrient-rich source of organic matter, and include precursors to climate active compounds (e.g., dimethyl sulfide [DMS]), which are likely regulated with environmental change. Here, intracellular concentrations of 45 metabolites were quantified in three sea-ice diatom species and were compared to two temperate diatom species, with a focus on compatible solutes and free amino acid pools. There was a large diversity of metabolite concentrations between diatoms with no clear pattern identifiable for sea-ice species. Concentrations of some compatible solutes (isethionic acid, homarine) approached 1 M in the sea-ice diatoms, Fragilariopsis cylindrus and Navicula cf. perminuta, but not in the larger sea-ice diatom, Nitzschia lecointei or in the temperate diatom species. The differential use of compatible solutes in sea-ice diatoms suggests different adaptive strategies and highlights which small organic compounds may be important in polar biogeochemical cycles.

Description: Comparable values have been obtained for endogenous fecal calcium in cattle by an “isotope dilution” method and a “comparative balance” method. Both procedures involve the use of labeled calcium, but they are different in principle. The “isotope dilution” method offers advantages in being independent of the availability of the dietary calcium and of the uncertainties of balance determinations.

Description: Endogenous fecal calcium was estimated directly in normal cattle by a method which consisted of 10 daily intravenous injections of radiocalcium, comparison of the specific activities of blood and feces taken on the 4th to 8th day post-injection, and routine determination of calcium balance. The daily endogenous fecal values for three 8-year-old dairy cows averaged 7 gm and for two yearling Hereford steers about 4 gm. The endogenous fecal calcium was not significantly changed when the dietary calcium was varied from normal to a high level. In two animals on a low calcium diet a decrease in endogenous fecal calcium was indicated.

Description: Rayleigh fractionation is an important, open system process that involves the progressive removal of a fractional increment of a trace substance from a larger reservoir. A consistent relationship, such as a distribution coefficient, equilibrium constant, or a fractionation factor, is maintained between the reservoir and each increment at the instant of its formation, but, once formed, each increment is thereafter removed or otherwise isolated from the system. The mathematical constraints of this process include the distribution coefficient along with a statement of material balance in the shrinking system. These constraints may be combined into a single differential equation that may be integrated to a well-known relationship discovered by Rayleigh (1902). Examples of this common process include condensation, distillation, and the formation of crystals from a melt or a solution. As shown in the following, Rayleigh fractionation explains many different characteristics of meteoric waters, and provides a first-order explanation of the MWL

Description: Petrographic, mineralogic, and geochemical data are reported for lavas from two of the major shield volcanoes of the Santorini volcanic complex (Skaros and Micro Profitis Ilias), both of which were active prior to the well-known Minoan eruption with associated caldera collapse. Field work and whole-rock chemical analyses indicate four cycles of eruptive activity within the Skaros sequence and three within the Micro Profitis Ilias (M P1) sequence. SiO2 and LIL-element contents decrease from the base to the top of all cycles except for the uppermost cycle of Skaros. Chemical variations within cycles are interpreted to result from eruption from compositionally and thermally zoned magma chambers. Major oxide data and the results of least-squares, mass balance modeling indicate that fractional crystallization played an important role in the development of the observed chemical variations. However, observed systematic variations in groundmass compositions within each cycle, observed irregular variations in total phenocryst content and the results of density calculations require that generation of the chemical zonation did not involve crystal settling but reflects unstable density stratification, probably resulting from sidewall crystallization. Some of the primitive lavas erupted on Santorini preserve phenocryst and xenocryst evidence for a stage of high-pressure fractional crystallization (involving removal of olivine, clinopyroxene, orthopyroxene, and Cr-spinel). Trace element data combined with petrographic data (i.e. the occurrence of abundant phenocrysts with resorption textures) is taken as evidence that magma mixing was also important in the development of cyclic variations. Most basaltic andesites from Skaros appear to be hybrids derived by mixing of basalt and andesite/dacite. Mineralogic data demonstrate that mixing was also important in the development of zonation in the chambers beneath MPI, but trace element data cannot be explained by combined fractionation and mixing alone. Specifically, incompatible, and compatible element abundances are lower than predicted if fractionation and mixing occurred and it is suggested that the anomalous trace element behaviour of especially LIL elements reflects the simultaneous operation of assimilation, for which there is support from isotopic studies. It is concluded that inter- cyclic chemical variations are explicable in terms of fractionation, mixing and assimilation. The LIL element and highly compatible element concentrations in the most primitive lavas erupted in each cycle of Skaros and MPI increase with time, indicating that mixing became more important with time.

Description: Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the subseafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a 2-D perturbation study. Our workflow enables stable and geologically reliable results for multicomponent and multifrequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous subseafloor conductivity model. Some navigational uncertainties are estimated from variations of direct measurements. Other navigational parameters required for inversion are derived from the measured quantities and their error is calculated by means of error propagation. Some navigational parameters show direct correlation with the measured electric fields. For example, the antenna dip correlates with the vertical electric field and the depth correlates with the horizontal electric field. For the perturbation study each standard deviation is added to the navigational parameters. Forward models are run for each perturbation. Amplitude deviations are summed in quadrature with the stacking error for a total, laterally varying, data error. The error estimation is repeated for a heterogeneous subseafloor model due to the large conductivity range (several orders of magnitude), which affects the forward model. The approach enables us to utilize data from several components (multiple electric fields, frequencies and receivers) in the inversion to constrain the final model and reduce ambiguity. The final model is geologically reasonable, in this case enabling the identification of conductive metal sulphide deposits on the seafloor.

Description: Background: The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea-dwelling species will allow several pending evolutionary questions to be unlocked. Findings: We present a draft genome assembly that includes 200 Gb of Illumina reads, 4 Gb of Moleculo synthetic long reads, and 108 Gb of Chicago libraries, with a final size matching the estimated genome size of 2.7 Gb, and a scaffold N50 of 4.8 Mb. We also present an alternative assembly including 27 Gb raw reads generated using the Pacific Biosciences platform. In addition, we sequenced the proteome of the same individual and RNA from 3 different tissue types from 3 other species of squid (Onychoteuthis banksii, Dosidicus gigas, and Sthenoteuthis oualaniensis) to assist genome annotation. We annotated 33,406 protein-coding genes supported by evidence, and the genome completeness estimated by BUSCO reached 92%. Repetitive regions cover 49.17% of the genome. Conclusions: This annotated draft genome of A. dux provides a critical resource to investigate the unique traits of this species, including its gigantism and key adaptations to deep-sea environments.

Description: Parasites are arguably among the strongest drivers of natural selection, constraining hosts to evolve resistance and tolerance mechanisms. Although, the genetic basis of adaptation to parasite infection has been widely studied, little is known about how epigenetic changes contribute to parasite resistance and eventually, adaptation. Here, we investigated the role of host DNA methylation modifications to respond to parasite infections. In a controlled infection experiment, we used the three-spined stickleback fish, a model species for host-parasite studies, and their nematode parasite Camallanus lacustris. We showed that the levels of DNA methylation are higher in infected fish. Results furthermore suggest correlations between DNA methylation and shifts in key fitness and immune traits between infected and control fish, including respiratory burst and functional trans-generational traits such as the concentration of motile sperm. We revealed that genes associated with metabolic, developmental and regulatory processes (cell death and apoptosis) were differentially methylated between infected and control fish. Interestingly, genes such as the neuropeptide FF receptor 2 and the integrin alpha 1 as well as molecular pathways including the Th1 and Th2 cell differentiation were hypermethylated in infected fish, suggesting parasite-mediated repression mechanisms of immune responses. Altogether, we demonstrate that parasite infection contributes to genome-wide DNA methylation modifications. Our study brings novel insights into the evolution of vertebrate immunity and suggests that epigenetic mechanisms are complementary to genetic responses against parasite-mediated selection.

Description: International Ocean Discovery Program (IODP) Expedition 351 “Izu–Bonin–Mariana (IBM) Arc Origins” drilled Site U1438, situated in the north-western region of the Philippine Sea. Here volcaniclastic sediments and the igneous basement of the proto-IBM volcanic arc were recovered. To gain a better understanding of the magmatic processes and evolution of the proto-IBM arc, we studied melt inclusions hosted in fresh igneous minerals and sampled from 30- to 40-Ma-old deposits, reflecting the maturation of arc volcanism following subduction initiation at 52 Ma. We performed a novel statistical analysis on the major element composition of 237 representative melt inclusions selected from a previously published dataset, covering the full age range between 30 and 40 Ma. In addition, we analysed volatiles (H2O, S, F and Cl) and P2O5 by Secondary Ion Mass Spectrometry (SIMS) for a subset of 47 melt inclusions selected from the dataset. Based on statistical analysis of the major element composition of melt inclusions and by considering their trace and volatile element compositions, we distinguished five main clusters of melt inclusions, which can be further separated into a total of eight subclusters. Among the eight subclusters, we identified three major magma types: (1) enriched medium-K magmas, which form a tholeiitic trend (30–38 Ma); (2) enriched medium-K magmas, which form a calc-alkaline trend (30–39 Ma); and (3) depleted low-K magmas, which form a calc-alkaline trend (35–40 Ma). We demonstrate that (1) the eruption of depleted low-K calc-alkaline magmas occurred prior to 40 Ma and ceased sharply at 35 Ma; (2) the eruption of depleted low-K calc-alkaline magmas, enriched medium-K calc-alkaline magmas and enriched medium-K tholeiitic magmas overlapped between 35 and 38 − 39 Ma; and (3) the eruption of enriched medium-K tholeiitic and enriched medium-K calc-alkaline magmas became predominant thereafter at the proto-IBM arc. Identification of three major magma types are distinct from the previous work, in which enriched medium-K calc-alkaline magmas and depleted low-K calc-alkaline magmas were not identified. This indicates the usefulness of our statistical analysis as a powerful tool to partition a mixture of multivariable geochemical datasets, such as the composition of melt inclusions in this case. Our data suggest that a depleted mantle source had been replaced by an enriched mantle source due to convection beneath the proto-IBM arc from >40 to 35 Ma. Finally, thermodynamic modelling indicates that the overall geochemical variation of melt inclusions assigned to each cluster can be broadly reproduced either by crystallisation differentiation assuming P = 50 MPa (∼2-km deep) and ∼2 wt % H2O (almost saturated H2O content at 50 MPa) or P = 300 MPa (∼15-km deep) and ∼6 wt % H2O (almost saturated H2O content at 300 MPa). Assuming oxygen fugacity (fO2) of log fO2 equal to + 1 relative to nickel-nickel oxide (NNO) buffer best reproduces the overall geochemical variation of melt inclusions, but assuming a more oxidising conditions (log fO2 = +1 to + 2 NNO) likely reproduces the geochemical variation of enriched medium-K and calc-alkaline melt inclusions (30 − 39 Ma).

Description: The present study quantified prey preferences by adult males and females of the mysid Mesopodopsis wooldridgei fed the calanoid copepods Pseudodiaptomus hessei and Paracartia longipatella at varying proportions. Both sexes of M. wooldridgei showed a lack of prey switching and a strong preference for the smaller, less active P. longipatella irrespective of density. Given a lack of low-density prey refuge, this finding may have important implications for the distribution of P. longipatella in estuaries along the eastern seaboard of South Africa. Results of the present study contribute to a growing body of literature that suggests that selective predation may play an important role in structuring plankton prey populations in shallow water ecosystems.

Description: The two toothed jaws of cichlid fishes provide textbook examples of convergent evolution. Tooth phenotypes such as enlarged molar-like teeth used to process hard-shelled molluscs have evolved numerous times independently during cichlid diversification. While the ecological benefit of molar-like teeth to crush prey is known, it is unclear whether the same molecular mechanisms underlie these convergent traits. To identify genes involved in the evolution and development of enlarged cichlid teeth, we performed RNA-seq on the serially homologous toothed oral and pharyngeal jaws as well as the fourth toothless gill arch of Astatoreochromis alluaudi. We identified 27 genes that are highly upregulated on both tooth-bearing jaws compared to the toothless gill arch. Most of these genes have never been reported to play a role in tooth formation. Two of these genes (unk, rpfA) are not found in other vertebrate genomes but are present in all cichlid genomes. They also cluster genomically with two other highly expressed tooth genes (odam, scpp5) that exhibit conserved expression during vertebrate odontogenesis. Unk and rpfA were confirmed via in situ hybridization to be expressed in developing teeth of Astatotilapia burtoni. We then examined expression of the cluster's four genes in six evolutionarily independent and phylogenetically disparate cichlid species pairs each with a large- and a small-toothed species. Odam and unk commonly and scpp5 and rpfA always showed higher expression in larger-toothed cichlid jaws. Convergent trophic adaptations across cichlid diversity are associated with the repeated developmental deployment of this genomic cluster containing conserved and novel cichlid-specific genes.

Description: Background and Aims Dysregulated mineral homeostasis is common in chronic kidney disease (CKD) and associated with bone demineralization and vascular calcification. The balance between bone formation and resorption, which reflect the bone calcium (Ca) balance (BCaB), cannot be determined without bone biopsy which is invasive and not easily repeatable. Recently, we have shown that stable (i.e. non-radioactive) Ca isotopes, 42Ca and 44Ca, can be measured in serum and their ratio (δ44/42Caserum) quantitatively determines net bone gain or loss of Ca. Thus, when bone formation exceeds bone resorption, the net BCaB is positive and δ44/42Caserum is high, and when bone resorption is the predominant process δ44/42Caserum is low compared to age-matched controls. In this study we compared δ44/42Caserum against δ44/42Cabone and arterial biopsy samples (δ44/42Caartery) and the sensitivity of δ44/42Ca in predicting changes in bone histology.

Description: Full waveform inversion (FWI) is a data-fitting technique capable of generating high-resolution velocity models with a resolution down to half the seismic wavelength. FWI is applied typically to densely sampled seismic data. In this study, we applied FWI to 3D wide-angle seismic data acquired using sparsely spaced ocean bottom seismometers (OBSs) from the Deep Galicia Margin west of Iberia. Our dataset samples the S-reflector, a low-angle detachment present in this area. Here we highlight differences between 2D, 2.5D and 3D-FWI performances using a real sparsely spaced dataset. We performed 3D FWI in the time domain and compared the results with 2D and 2.5D FWI results from a profile through the 3D model. When overlaid on multichannel seismic images, the 3D FWI results constrain better the complex faulting within the pre- and syn-rift sediments and crystalline crust compared to the 2D result. Furthermore, we estimate variable serpentinisation of the upper mantle below the S-reflector along the profile using 3D FWI, reaching a maximum of 45 per cent. Differences in the data residuals of the 2D, 2.5D and 3D inversions suggest that 2D inversion can be prone to overfitting when using a sparse dataset. To validate our results, we performed tests to recover the anomalies introduced by the inversions in the final models using synthetic datasets. Based on our comparison of the velocity models, we conclude that the use of 3D data can partially mitigate the problem of receiver sparsity in FWI.

Description: The seismic receiver function (RF) technique is widely used as an economic method to image earth's deep interior in a large number of seismic experiments. P-wave receiver functions (RFs) constrain crustal thickness and average Vp/Vs in the crust by analysis of the Ps phase and multiples (reflected/converted waves) from the Moho. Regional studies often show significant differences between the Moho depth constrained by RF and by reflection/refraction methods. We compare the results from RF and controlled source seismology for the Baikal Rift Zone by calculating 1480 synthetic RFs for a seismic refraction/reflection velocity model and processing them with two common RF techniques [H–κ and Common Conversion Point (CCP) stacking]. We compare the resulting synthetic RF structure with the velocity model, a density model (derived from gravity and the velocity model), and with observed RFs. Our results demonstrate that the use of different frequency filters, the presence of complex phases from sediments and gradual changes in the properties of crustal layers can lead to erroneous interpretation of RFs and incorrect geological interpretations. We suggest that the interpretation of RFs should be combined with other geophysical methods, in particular in complex tectonic regions and that the long-wavelength Bouguer gravity anomaly signal may provide effective calibration for the determination of the correct Moho depth from RF results. We propose and validate a new automated, efficient method for this calibration.

Description: We analyse the consistency of the delay time data in the most recent version of the ISC-EHB bulletin published by the International Seismological Centre covering the years 1964–2018. Considering that the delays are influenced by the lateral heterogeneity in the Earth’s mantle, we construct a tomographic matrix. We use singular value decomposition of the tomographic matrix for 19 707 dense clusters of earthquakes to compute objective estimates of the standard error from data that project into the null space and should be zero if there were no errors. Using a robust initial estimate of the standard deviation of the clustered delay times, we remove a small fraction of outliers before calculating the ultimate errors. We found that the errors depend on the type of body wave, depth of the earthquake (crust or mantle) and the number of decimals with which the arrival time was reported. Using these parameters, we distinguish 45 different classes of delay times for 11 different types of body waves. The errors of each class so divided generally follow a distribution that is approximately normal with a mean that ranges from 0.32 s for PKPbc waves from mantle earthquakes, to 2.82 s for S waves from shallow earthquakes bottoming in the upper mantle. The widths of the distributions of the errors themselves are small enough to serve in formal statistical quantification of the quality of fit in tomographic experiments.

Description: The neritic-oceanic squid Illex argentinus supports one of the largest fisheries in the Southwest Atlantic. It is characterized by extensive migrations across the Patagonian Shelf and complex population structure comprising distinct seasonal spawning groups. To address uncertainty as to the demographic independence of these groups that may compromise sustainable management, a multidisciplinary approach was applied integrating statolith ageing with genome-wide single-nucleotide polymorphism (SNP) analysis. To obtain complete coverage of the spawning groups, sampling was carried out at multiple times during the 2020 fishing season and covered a large proportion of the species' range across the Patagonian Shelf. Statolith and microstructure analysis revealed three distinct seasonal spawning groups of winter-, spring-, and summer-hatched individuals. Subgroups were identified within each seasonal group, with statolith microstructure indicating differences in environmental conditions during ontogeny. Analysis of 〉10 000 SNPs reported no evidence of neutral or non-neutral genetic structure among the various groups. These findings indicate that I. argentinus across the Patagonian Shelf belong to one genetic population and a collaborative management strategy involving international stakeholders is required. The connectivity among spawning groups may represent a "bet-hedging" mechanism important for population resilience.

Description: The dynamics of marine systems at decadal scales are notoriously hard to predict—hence references to this timescale as the “grey zone” for ocean prediction. Nevertheless, decadal-scale prediction is a rapidly developing field with an increasing number of applications to help guide ocean stewardship and sustainable use of marine environments. Such predictions can provide industry and managers with information more suited to support planning and management over strategic timeframes, as compared to seasonal forecasts or long-term (century-scale) predictions. The most significant advances in capability for decadal-scale prediction over recent years have been for ocean physics and biogeochemistry, with some notable advances in ecological prediction skill. In this paper, we argue that the process of “lighting the grey zone” by providing improved predictions at decadal scales should also focus on including human dimensions in prediction systems to better meet the needs and priorities of end users. Our paper reviews information needs for decision-making at decadal scales and assesses current capabilities for meeting these needs. We identify key gaps in current capabilities, including the particular challenge of integrating human elements into decadal prediction systems. We then suggest approaches for overcoming these challenges and gaps, highlighting the important role of co-production of tools and scenarios, to build trust and ensure uptake with end users of decadal prediction systems. We also highlight opportunities for combining narratives and quantitative predictions to better incorporate the human dimension in future efforts to light the grey zone of decadal-scale prediction.

Description: Post-collisional volcanism contains important clues for understanding the processes that prevail in orogenic belts, including those in the mantle and the uplift and collapse of continents. Here we report new geochronological and geochemical data for a suite of post-collisional Miocene to Pleistocene volcanic rocks from northwest Iran. Four groups of volcanic rocks can be distinguished according to their geochemical and isotopic signatures, including: (1) Miocene depleted lavas with high Nd and Hf but low Pb and Sr isotopic ratios, (2) less depleted lavas with quite variable Pb isotopic composition, (3) lavas with non-radiogenic Nd and Hf isotopic values, but highly radiogenic Sr and Pb isotopic composition, and (4) Pleistocene adakitic rocks with depleted isotopic signatures. The isotopic data reveal that the Miocene rocks are derived from asthenospheric and highly heterogeneous sub-continental lithospheric mantle sources. Evidence suggests that the lithospheric mantle contains recycled upper continental material and is isotopically similar to the enriched mantle two (EMII) end-member. Analysis of Sr-Nd-Pb-Hf-O isotopes in both mineral and rock groundmass, in conjunction with energy-constrained assimilation and fractional crystallization (EC-AFC) numerical modeling, demonstrates that the incorporation of continental crust during magma fractionation via AFC had an insignificant impact on the isotopic composition of the Miocene lavas. Moreover, adakites are the youngest rocks and show a geochemical signature consistent with the partial melting of a young and mafic continental lower crust. Both seismological data and geochemical signatures on these Miocene to Pleistocene volcanic rocks indicate the initiation of asthenospheric upwelling and orogen uplift in the Arabia-Eurasia collision zone, which occurred after slab break-off, following the Neotethyan closure.

Description: Probing seismic anisotropy of the lithosphere provides valuable clues on the fabric of rocks. We present a 3-D probabilistic model of shear wave velocity and radial anisotropy of the crust and uppermost mantle of Europe, focusing on the mountain belts of the Alps and Apennines. The model is built from Love and Rayleigh dispersion curves in the period range 5–149 s. Data are extracted from seismic ambient noise recorded at 1521 broad-band stations, including the AlpArray network. The dispersion curves are first combined in a linearized least squares inversion to obtain 2-D maps of group velocity at each period. Love and Rayleigh maps are then jointly inverted at depth for shear wave velocity and radial anisotropy using a Bayesian Monte Carlo scheme that accounts for the trade-off between radial anisotropy and horizontal layering. The isotropic part of our model is consistent with previous studies. However, our anisotropy maps differ from previous large scale studies that suggested the presence of significant radial anisotropy everywhere in the European crust and shallow upper mantle. We observe instead that radial anisotropy is mostly localized beneath the Apennines while most of the remaining European crust and shallow upper mantle is isotropic. We attribute this difference to trade-offs between radial anisotropy and thin (hectometric) layering in previous studies based on least-squares inversions and long period data (〉30 s). In contrast, our approach involves a massive data set of short period measurements and a Bayesian inversion that accounts for thin layering. The positive radial anisotropy (VSH 〉 VSV) observed in the lower crust of the Apennines cannot result from thin layering. We rather attribute it to ductile horizontal flow in response to the recent and present-day extension in the region.

Description: Primary andesitic magmas could be an important component of arc magma genesis and might have played a key role in the advent of continents. Recent studies hypothesized that primary andesitic magmas occur in the oceanic arc, where the crust is thin. The Kermadec arc has the thinnest crust among all the studied oceanic arcs (〈15 km in thickness); however, there are no studies that corroborate the formation of primary andesitic magmas in the arc. The aim of this study is to develop a better understanding of primary andesites in oceanic arcs through the petrology of the Kermadec arc. Here, we present the petrology of volcanic rocks dredged from the Kibblewhite Volcano in the Kermadec arc during the R/V SONNE SO-255 expedition in 2017. Magma types range from andesite to rhyolite at the Kibblewhite Volcano, but basalts dominate at the neighboring cones. This study focuses on magnesian andesites from the northeastern flank of this volcano. The magnesian andesites are nearly aphyric and plagioclase free but contain microphenocrysts of olivine (Fo84–86) and clinopyroxene (Mg# = 81–87). Using olivine addition models, the primary magmas were estimated to contain 55–56 wt % SiO2 and 10–12 wt % MgO, similar to the high-Mg andesites observed in other convergent plate margins, indicating the generation of primary andesitic magma beneath the Kibblewhite Volcano. The trace element and isotopic characteristics of the magnesian andesites are typical of volcanic rocks from the Kermadec arc. This indicates that the subduction of a young plate or melting of a pyroxenitic source is not necessary to produce magnesian andesites. Instead, we propose that the magnesian andesites were produced by the direct melting of the uppermost mantle of the Kermadec arc. The thin crust of the Kermadec arc should yield low-pressure conditions in the uppermost mantle, allowing the sub-arc mantle to generate primary andesitic melts. This study supports the hypothesis that primary andesitic magmas generate in the arc where the crust is thin and provides a new insight into the magma genesis of the Kermadec arc.

Description: Mitochondrial genomes (mitogenomes) of flowering plants are composed of multiple chromosomes. Recombination within and between the mitochondrial chromosomes may generate diverse DNA molecules termed isoforms. The isoform copy number and composition can be dynamic within and among individual plants due to uneven replication and homologous recombination. Nonetheless, despite their functional importance, the level of mitogenome conservation within species remains understudied. Whether the ontogenetic variation translates to evolution of mitogenome composition over generations is currently unknown. Here we show that the mitogenome composition of the seagrass Zostera marina is conserved among worldwide populations that diverged ca. 350,000 years ago. Using long-read sequencing, we characterized the Z. marina mitochondrial genome and inferred the repertoire of recombination-induced configurations. To characterize the mitochondrial genome architecture worldwide and study its evolution, we examined the mitogenome in Z. marina meristematic region sampled in 16 populations from the Pacific and Atlantic oceans. Our results reveal a striking similarity in the isoform relative copy number, indicating a high conservation of the mitogenome composition among distantly related populations and within the plant germline, despite a notable variability during individual ontogenesis. Our study supplies a link between observations of dynamic mitogenomes at the level of plant individuals and long-term mitochondrial evolution.

Description: Marine algae are central to global carbon fixation and their productivity is dictated largely by resource availability. Reduced nutrient availability is predicted for vast oceanic regions as an outcome of climate change, however there is much to learn regarding response mechanisms of the tiny picoplankton that thrive in these environments, especially eukaryotic phytoplankton. Here, we investigate responses of the picoeukaryote Micromonas commoda, a green alga found throughout subtropical and tropical oceans. Under shifting phosphate (P) availability scenarios, transcriptomic analyses revealed altered expression of transfer RNA (tRNA) modification enzymes and biased codon usage of transcripts more abundant during P-limiting versus P-replete conditions, consistent with the role of tRNA modifications in regulating codon recognition. To associate the observed shift in expression of the tRNA modification enzyme complement with the tRNAs encoded by M. commoda, we also determined the tRNA repertoire of this alga revealing potential targets of the modification enzymes. Codon usage bias was particularly pronounced in transcripts encoding proteins with direct roles in managing P-limitation and photosystem-associated proteins that have ill-characterized putative functions in “light stress”. The observed codon usage bias corresponds to a proposed stress response mechanism in which the interplay between stress-induced changes in tRNA modifications and skewed codon usage in certain essential response genes drives preferential translation of the encoded proteins. Collectively, we expose a potential underlying mechanism for achieving growth under enhanced nutrient limitation, that extends beyond the catalog of up- or down-regulated protein-encoding genes, to the cell biological controls that underpin acclimation to changing environmental conditions.

Description: Seismic full waveform inversion (FWI) is a powerful method for estimating quantitative subsurface physical parameters from seismic data. As the full waveform inversion is a non-linear problem, the linearized approach updates model iteratively from an initial model, which can get trapped in local minima. In the presence of a high velocity contrast, such as at Moho, the reflection coefficient and recorded waveforms from wide-aperture seismic acquisition are extremely non-linear around critical angles. The problem at the Moho is further complicated by the interference of lower crustal (Pg) and upper mantle (Pn) turning ray arrivals with the critically reflected Moho arrivals (PmP). In order to determine velocity structure near Moho, a non-linear method should be used. We propose to solve this strong non-linear FWI problem at Moho using a trans-dimensional Markov chain Monte Carlo (MCMC) method, where the earth model between lower crust and upper mantle is idealy parameterized with a 1-D assumption using a variable number of velocity interfaces. Different from common MCMC methods that require determining the number of unknown as a fixed prior before inversion, trans-dimensional MCMC allows the flexibility for an automatic estimation of both the model complexity (e.g. the number of velocity interfaces) and the velocity-depth structure from the data. We first test the algorithm on synthetic data using four representative Moho models and then apply to an ocean bottom seismometer (OBS) data from the Mid-Atlantic Ocean. A 2-D finite-difference solution of an acoustic wave equation is used for data simulation at each iteration of MCMC search, for taking into account the lateral heterogeneities in the upper crust, which is constrained from travel time tomography and is kept unchanged during inversion; the 1-D model parameterization near Moho enables an efficient search of the trans-dimensional model space. Inversion results indicate that, with very little prior and the wide-aperture seismograms, the trans-dimensional FWI method is able to infer the posterior distribution of both the number of velocity interfaces and the velocity-depth model for a strong nonlinear problem, making the inversion a complete data-driven process. The distribution of interface matches the velocity discontinuities. We find that the Moho in the study area is a transition zone of 0.7 km, or a sharp boundary with velocities from around 7 km/s in the lower crust to 8 km/s of the upper mantle; both provide nearly identical waveform match for the field data. The ambiguity comes from the resolution limit of the band-limited seismic data and limited offset range for PmP arrivals.

Description: Omic BON is a thematic Biodiversity Observation Network under the Group on Earth Observations Biodiversity Observation Network (GEO BON), focused on coordinating the observation of biomolecules in organisms and the environment. Our founding partners include representatives from national, regional, and global observing systems; standards organizations; and data and sample management infrastructures. By coordinating observing strategies, methods, and data flows, Omic BON will facilitate the co-creation of a global omics meta-observatory to generate actionable knowledge. Here, we present key elements of Omic BON's founding charter and first activities.

Description: Young grapevines (Vitis vinifera) suffer and eventually can die from the crown gall disease caused by the plant pathogen Allorhizobium vitis (Rhizobiaceae). Virulent members of A. vitis harbor a tumor-inducing plasmid and induce formation of crown galls due to the oncogenes encoded on the transfer DNA. The expression of oncogenes in transformed host cells induces unregulated cell proliferation and metabolic and physiological changes. The crown gall produces opines uncommon to plants, which provide an important nutrient source for A. vitis harboring opine catabolism enzymes. Crown galls host a distinct bacterial community, and the mechanisms establishing a crown gall–specific bacterial community are currently unknown. Thus, we were interested in whether genes homologous to those of the tumor-inducing plasmid coexist in the genomes of the microbial species coexisting in crown galls. We isolated 8 bacterial strains from grapevine crown galls, sequenced their genomes, and tested their virulence and opine utilization ability in bioassays. In addition, the 8 genome sequences were compared with 34 published bacterial genomes, including closely related plant-associated bacteria not from crown galls. Homologous genes for virulence and opine anabolism were only present in the virulent Rhizobiaceae. In contrast, homologs of the opine catabolism genes were present in all strains including the nonvirulent members of the Rhizobiaceae and non-Rhizobiaceae. Gene neighborhood and sequence identity of the opine degradation cluster of virulent and nonvirulent strains together with the results of the opine utilization assay support the important role of opine utilization for cocolonization in crown galls, thereby shaping the crown gall community.

Description: Eutrophication in marine waters is traditionally assessed by checking if nutrients, algal biomass and oxygen are below/above a given threshold. However, increased biomass, nutrient concentrations and oxygen demand do not lead to undesirable environmental effects if the flow of carbon/energy from primary producers toward high trophic levels is consistently preserved. Consequently, traditional indicators might provide a misleading assessment of the eutrophication risk. To avoid this, we propose to evaluate eutrophication by using a new index based on plankton trophic fluxes instead of biogeochemical concentrations. A preliminary, model-based, assessment suggests that this approach might give a substantially different picture of the eutrophication status of our seas, with potential consequences on marine ecosystem management. Given the difficulties to measure trophic fluxes in the field, the use of numerical simulations is recommended although the uncertainty associated with biogeochemical models inevitably affects the reliability of the index. However, given the effort currently in place to develop refined numerical tools describing the marine environment (Ocean Digital Twins), a reliable, model-based, eutrophication index could be operational in the near future.

Description: To constrain seismic anisotropy under and around the Alps in Europe, we study SKS shear wave splitting from the region densely covered by the AlpArray seismic network. We apply a technique based on measuring the splitting intensity, constraining well both the fast orientation and the splitting delay. Four years of teleseismic earthquake data were processed, from 723 temporary and permanent broad-band stations of the AlpArray deployment including ocean-bottom seismometers, providing a spatial coverage that is unprecedented. The technique is applied automatically (without human intervention), and it thus provides a reproducible image of anisotropic structure in and around the Alpine region. As in earlier studies, we observe a coherent rotation of fast axes in the western part of the Alpine chain, and a region of homogeneous fast orientation in the Central Alps. The spatial variation of splitting delay times is particularly interesting though. On one hand, there is a clear positive correlation with Alpine topography, suggesting that part of the seismic anisotropy (deformation) is caused by the Alpine orogeny. On the other hand, anisotropic strength around the mountain chain shows a distinct contrast between the Western and Eastern Alps. This difference is best explained by the more active mantle flow around the Western Alps. The new observational constraints, especially the splitting delay, provide new information on Alpine geodynamics.

Description: Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales is a highly diverse and widely distributed order including species that can serve as ecosystem engineers in intertidal habitats and several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

Description: Biological invasions are a global challenge that has received insufficient attention. Recently available cost syntheses have provided policy- and decision makers with reliable and up-to-date information on the economic impacts of biological invasions, aiming to motivate effective management. The resultant InvaCost database is now publicly and freely accessible and enables rapid extraction of monetary cost information. This has facilitated knowledge sharing, developed a more integrated and multidisciplinary network of researchers, and forged multidisciplinary collaborations among diverse organizations and stakeholders. Over 50 scientific publications so far have used the database and have provided detailed assessments of invasion costs across geographic, taxonomic, and spatiotemporal scales. These studies have provided important information that can guide future policy and legislative decisions on the management of biological invasions while simultaneously attracting public and media attention. We provide an overview of the improved availability, reliability, standardization, and defragmentation of monetary costs; discuss how this has enhanced invasion science as a discipline; and outline directions for future development.

Description: The development and physiology of herring larvae were monitored for individuals reared in control and combined warming-acidification crossed with different food quality treatments. The experiment revealed that warming and acidification triggers a stress response at the molecular level and decrease herring larvae size-at-stage. Global change puts coastal systems under pressure, affecting the ecology and physiology of marine organisms. In particular, fish larvae are sensitive to environmental conditions, and their fitness is an important determinant of fish stock recruitment and fluctuations. To assess the combined effects of warming, acidification and change in food quality, herring larvae were reared in a control scenario (11 & DEG;C*pH 8.0) and a scenario predicted for 2100 (14 & DEG;C*pH 7.6) crossed with two feeding treatments (enriched in phosphorus and docosahexaenoic acid or not). The experiment lasted from hatching to the beginning of the post-flexion stage (i.e. all fins present) corresponding to 47 days post-hatch (dph) at 14 & DEG;C and 60 dph at 11 & DEG;C. Length and stage development were monitored throughout the experiment and the expression of genes involved in growth, metabolic pathways and stress responses were analysed for stage 3 larvae (flexion of the notochord). Although the growth rate was unaffected by acidification and temperature changes, the development was accelerated in the 2100 scenario, where larvae reached the last developmental stage at a smaller size (-8%). We observed no mortality related to treatments and no effect of food quality on the development of herring larvae. However, gene expression analyses revealed that heat shock transcripts expression was higher in the warmer and more acidic treatment. Our findings suggest that the predicted warming and acidification environment are stressful for herring larvae, inducing a decrease in size-at-stage at a precise period of ontogeny. This could either negatively affect survival and recruitment via the extension of the predation window or positively increase the survival by reducing the larval stage duration.

Description: Machine learning covers a large set of algorithms that can be trained to identify patterns in data. Thanks to the increase in the amount of data and computing power available, it has become pervasive across scientific disciplines. We first highlight why machine learning is needed in marine ecology. Then we provide a quick primer on machine learning techniques and vocabulary. We built a database of & SIM;1000 publications that implement such techniques to analyse marine ecology data. For various data types (images, optical spectra, acoustics, omics, geolocations, biogeochemical profiles, and satellite imagery), we present a historical perspective on applications that proved influential, can serve as templates for new work, or represent the diversity of approaches. Then, we illustrate how machine learning can be used to better understand ecological systems, by combining various sources of marine data. Through this coverage of the literature, we demonstrate an increase in the proportion of marine ecology studies that use machine learning, the pervasiveness of images as a data source, the dominance of machine learning for classification-type problems, and a shift towards deep learning for all data types. This overview is meant to guide researchers who wish to apply machine learning methods to their marine datasets.

Description: Volcano seismology is an essential tool for monitoring volcanic processes in the advent and during eruptions. A variety of seismic signals can be recorded at volcanoes, of which some are thought to be related to the migration of fluids which is of primary importance for the anticipation of imminent eruptions. We investigate the volcanic crises at Villarrica volcano in 2015 and report on a newly discovered very-long-period (VLP) signal that accompanies phases of periodic long period (LP) signal burst. Despite their low amplitude emergent character, we can locate the source region of the 1 Hz LP signals to the close vicinity of the volcano using a network-based correlation method. The source of the VLP signal with a period of about 30–100 s appears to locate in the vicinity of two stations a few kilometres from the summit. Both stations record very similar VLP waveforms that are correlated with the envelope of the LP bursts. A shallow magma reservoir was inferred by Contreras from surface deformation as the source of inflation following the eruption in 2015. Cyclic volume changes of 6 m3 in this reservoir at 3 km depth can explain the observed amplitudes of the vertical VLP signal. We propose that the LP signal is generated by the migration of gas or gas-rich magma that is periodically released from the inflating reservoir through a non-linear valve structure which modulates the flux, and thereby causes bursts of flow-related LP signals and pressure changes observed as VLP deformation. Our model predicts that the correlated occurrence of LP bursts and VLP surface motion depends on the intensity of the fluid flux. A weaker flux of fluids may not exceed the opening pressure of valve structure, and higher rates might maintain pressure above the closing pressure. In both cases, the VLP signal vanishes. Our observation provides constrains for models of fluid transport inside volcanoes. At Villarrica the VLP signal, and its relation to the LP activity, reveal additional information about fluxes in the magmatic reservoir that might aide forecasting of volcanic activity.

Description: Compositional variations of amphibole stratigraphically recovered from multiple eruptions at a given volcano have a great potential to archive long-term magmatic processes in its crustal plumbing system. Calcic amphibole is a ubiquitous yet chemically and texturally diverse mineral at Mount St. Helens (MSH), where it occurs in dacites and in co-magmatic enclaves throughout the Spirit Lake stage (last ~4000 years of eruptive history). It forms three populations with distinct geochemical trends in key major and trace elements, which are subdivided into a high-Al (11–14.5 wt% Al2O3), a medium-Al (10–12.5 wt% Al2O3), and a low-Al (7.5–10 wt% Al2O3) amphibole population. The oldest investigated tephra record (Smith Creek period, 3900–3300 years BP) yields a bimodal amphibole distribution in which lower-crustal, high-Al amphibole cores (crystallized dominantly from basaltic andesite to andesite melts) and upper-crustal, low-Al amphibole rims (crystallized from rhyolitic melt) document occasional recharge of a shallow silicic mush by a more mafic melt from a lower-crustal reservoir. The sudden appearance of medium-Al amphiboles enriched in incompatible trace elements in eruptive periods younger than 2900 years BP is associated with a change in reservoir conditions toward hotter and drier magmas, which indicates recharge of the shallow silicic reservoir by basaltic melt enriched in incompatible elements. Deep-crystallizing, high-Al amphibole, however, appears mostly unaffected by such incompatible-element-enriched basaltic recharge, suggesting that these basalts bypass the lower crustal reservoir. This could be the result of the eastward offset position of the lower crustal reservoir relative to the upper crustal storage zone underneath the MSH edifice. Amphibole has proven to be a sensitive geochemical archive for uncovering storage conditions of magmas at MSH. In agreement with geophysical observations, storage and differentiation have occurred in two main zones: an upper crustal and lower crustal reservoir (the lower one being chemically less evolved). The upper crustal silicic reservoir, offset to the west of the lower crustal reservoir, has captured compositionally unusual mafic recharge (drier, hotter, and enriched in incompatible trace elements in comparison to the typical parental magmas in the region), resulting in an increased chemical diversity of amphiboles and their carrier intermediate magmas, in the last ~3000 years of MSH’s volcanic record.

Description: Current global warming results in rising sea-water temperatures, and the loss of sea ice in arctic and subarctic oceans impacts the community composition of primary producers with cascading effects on the food web and potentially on carbon export rates. This study analyzes metagenomic shotgun and diatom rbcL amplicon-sequencing data from sedimentary ancient DNA (sedaDNA) of the subarctic western Bering Sea that records phyto- and zooplankton community changes over the last glacial–interglacial cycle, including the last interglacial period (Eemian). Our data show that interglacial and glacial plankton communities differ, with distinct Eemian and Holocene plankton communities. The generally warm Holocene period is dominated by pico-sized cyanobacteria and bacteria-feeding heterotrophic protists, while the Eemian period is dominated by eukaryotic pico-sized chlorophytes and Triparmaceae. In contrast, the glacial period is characterized by micro-sized phototrophic protists, including sea-ice associated diatoms in the family Bacillariaceae and co-occurring diatom-feeding crustaceous zooplankton. Our deep-time record of plankton community changes reveals a long-term decrease in phytoplankton cell size coeval with increasing temperatures, and resembling community changes in the currently warming Bering Sea. The phytoplankton community in the warmer-than-present Eemian period is distinct from modern communities and limits the use of the Eemian as an analog for future climate scenarios. However, under enhanced future warming, the expected shift towards the dominance of small-sized phytoplankton and heterotrophic protists might result in an increased productivity, whereas the community’s potential of carbon export will be decreased, thereby weakening the subarctic Bering Sea’s function as an effective carbon sink.

Description: Neomphaloidean gastropods are endemic to chemosynthesis-based ecosystems ranging from hot vents to organic falls, and their diversity and evolutionary history remain poorly understood. In the southwestern Pacific, deep-sea hydrothermal vents on back-arc basins and volcanic arcs are found in three geographically secluded regions: a western region around Manus Basin, an eastern region around North Fiji and Lau Basins, and the intermediate Woodlark Basin where active venting was confirmed only recently, on the 2019 R/V L’Atalante CHUBACARC expedition. Although various lineages of neomphaloidean snails have been detected, typically restricted to one of the three regions, some of these have remained without names. Here, we use integrative taxonomy to describe three of these species: the neomphalid Symmetromphalus mithril sp. nov. from Woodlark Basin and the peltospirids Symmetriapelta becki sp. nov. from the eastern region and Symmetriapelta radiata sp. nov. from Woodlark Basin. A combination of shell sculpture and radular characters allow the morphological separation of these new species from their described congeners. A molecular phylogeny reconstructed from 570 bp of the mitochondrial cytochrome c oxidase subunit I gene confirmed the placement of the three new species in their respective genera and the superfamily Neomphaloidea. The finding of these new gastropods, particularly the ones from the Woodlark Basin, provides insights and implications on the historical role of Woodlark as a dispersing centre, in addition to highlighting the uniqueness of the Woodlark faunal community.

Description: Several species from various zooplankton taxa perform seasonal vertical migrations (SVM) of typically several hundred meters between the surface layer and overwintering depths, particularly in high-latitude regions. We use OPtimality-based PLAnkton (OPPLA) ecosystem model) to simulate SVM behavior in zooplankton in the Labrador Sea. Zooplankton in OPPLA is a generic functional group without life cycle, which facilitates analyzing SVM evolutionary stability and interactions between SVM and the plankton ecosystem. A sensitivity analysis of SVM-related parameters reveals that SVM can amplify the seasonal variations of phytoplankton and zooplankton and enhance the reduction of summer surface nutrient concentrations. SVM is often explained as a strategy to reduce exposure to visual predators during winter. We find that species doing SVM can persist and even dominate the summer-time zooplankton community, even in the presence of Stayers, which have the same traits as the migrators, but do not perform SVM. The advantage of SVM depends strongly on the timing of the seasonal migrations, particularly the day of ascent. The presence of higher (visual) predators tends to suppress the Stayers in our simulations, whereas the SVM strategy can persist in the presence of non-migrating species even without higher predators.