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AbstractA trade‐off between current and future fitness potentially explains variation in life‐history strategies. A proposed mechanism behind this is parasite‐mediated reproductive costs: individuals that allocate more resources to reproduction have fewer to allocate to defence against parasites, reducing future fitness. We examined how reproduction influenced faecal egg counts (FEC) of strongyle nematodes using data collected between 1989 and 2008 from a wild population of Soay sheep in the St. Kilda archipelago, Scotland (741 individuals). Increased reproduction was associated with increased FEC during the lambing season: females that gave birth, and particularly those that weaned a lamb, had higher FEC than females that failed to reproduce. Structural equation modelling revealed future reproductive costs: a positive effect of reproduction on spring FEC and a negative effect on summer body weight were negatively associated with overwinter survival. Overall, we provide evidence that parasite resistance and body weight are important mediators of survival costs of reproduction.

Sediment-hosted marine sulfur cycling has played a significant role in regulating Earth's surface chemistry over our planet's history. Microbially-mediated reactions involving sulfur are often accompanied by sulfur isotope fractionation that, in turn, is captured by sulfate and sulfide minerals, providing the opportunity to track changes in the microbial utilization of sulfur and thus the marine sulfur cycle. Studying sulfur diagenesis within the Bornholm Basin, Baltic Sea, we explore the interplay between carbon, sulfur and iron, focusing on the fate of sulfur and the dynamics of the sulfur and oxygen isotopic response as a function of the varying thickness of the organic carbon-rich Holocene Mud Layer (HML) across the basin. Using a one-dimensional reaction-transport model, porewater sulfate and sulfide profiles were used to calculate net sulfate reduction rates (SRR) and net sulfide production rates, respectively. These calculations suggest a positive relationship between the thickness of the HML and net rates of sulfate reduction and sulfide production. Given that ascending sulfide is enriched in 34S relative to that produced in-situ, a heightened sulfide flux promotes spatially variable precipitation of 34S-enriched pyrite (δ34S ≈ −10‰) close to the sediment–water interface. Modeling results indicate that this isotopically “heavy” sulfide is formed as a consequence of mixing between ascending sulfide (up to +6.3‰) and that produced in-situ (ca. −40‰). Further, we show that the sulfur and oxygen isotopic composition of porewater sulfate is controlled by the net SRR: when the net SRR is high (i.e., in sulfide-replete settings) the downcore increase in δ18OSO4 is dampened relative to increase in δ34SSO4, whereas when net SRR is low (i.e., in iron-rich parts of the basin) downcore δ18OSO4 values increase while δ34SSO4 values remain invariant. We conclude that sedimentation rates and open system diffusion strongly influence the distribution of sulfur species and their sulfur isotopic composition, as well as the oxygen isotopic composition of sulfate, through the interaction between iron, sulfur and methane. This work highlights the importance of considering diffusion to better understand open system diagenesis and the δ34S signatures of sulfate and sulfide in both modern settings and ancient rocks.

Abstract Glaciated watersheds are regions of intense physical and chemical weathering. In order to gain new insight on subglacial weathering processes, we measured uranium and radium isotopes from a proglacial river draining the Greenland Ice Sheet (GrIS). Time series samples were collected from the spring to mid-summer, a time period during which subglacial drainage pathways are thought to transition from slow-inefficient (distributed) to fast-efficient (channelized) systems. The 228Ra/226Ra activity ratio of the dissolved load varied from 5.2 ± 0.9–16.9 ± 3.6, which was significantly higher than the 228Ra/226Ra ratio of a suspended sediment load sample of 2.1 ± 0.07 and crustal values of ~1. The high 228Ra/226Ra in the dissolved load relative to the source rock material is indicative of mineral surface weathering induced by rapid and continuous flushing of the subglacial drainage network during the course of the melt season and those prior. The 234U/238U ratio (δ234U) varied between 33 and 106‰ with a discharge-weighted mean of 67‰; the seasonal evolution of δ234U did not correlate to geochemical indicators of subglacial meltwater storage time. An experiment designed to measure changes in δ234U with increasing meltwater storage times found that δ234U in the dissolved phase decreased rapidly with increasing storage time. Similarly, samples collected along a transect moving downstream from the ice sheet terminus had decreasing δ234U values from 63 to 15‰ further indicating that with increased weathering, the δ234U of meltwater decreases. Coupled with the relatively low δ234U and high 228Ra/226Ra, U appears to be impacted by rapid chemical weathering of subglacial and suspended sediments. The Leverett River discharge weighted U concentration was 0.13 nM; if this system is considered representative of the broader GrIS, then the total dissolved U flux from the GrIS would be on the order of 6.4 × 104 mol/y. Using a similar set of assumptions, the dissolved 228Ra and 226Ra flux from the GrIS was ~1.1 × 1014 dpm/y and ~ 5.5 × 1013 dpm/y, respectively. These estimates suggest that the 226Ra flux to the ocean from the GrIS is globally significant and that the 228Ra flux in particular is larger than most river inputs.

A detailed record of late Pleistocene deglaciation followed by mid-Holocene ice shelf breakup and late Holocene re-growth is contained in continental shelf sediments in the northern Larsen area, northeast Antarctic Peninsula. The zero age of core tops is confirmed by new and published 210Pb profiles, and 70 accelerator mass spectrometer (AMS) 14C dates on bulk organic carbon define sedimentation rates of 7.6–92 cm/ka. The varied geology in the local ice drainage basins facilitates the use of ice-rafted debris (IRD) provenance in determining the presence or absence of ice shelves. All inshore cores contain an interval of non-local IRD in the post-glacial section, demonstrating widespread ice shelf breakup in the mid-Holocene. Both breakup and re-growth may have taken centuries and there are no widespread debris layers associated with breakup. Cores beyond and up to 30 km inside the historical ice shelf limit exhibit a varied IRD provenance throughout the Holocene, suggesting the maximum ice shelf limit may date only from the Little Ice Age. Benthic foraminiferal assemblages are related to water masses and position on the continental shelf and have been modified by taphonomic processes. Nevertheless we discern a deglaciation signal in Prince Gustav Channel of a calcareous spike in predominantly agglutinated assemblages, and this is repeated at the time of mid-Holocene ice shelf breakup. The inferred mid-Holocene warm period occurred later in the northern Larsen area than on the west coast of the Antarctic Peninsula.

Semi-continuous, linear accumulations of poorly-sorted debris are present on the surface of the remnant Larsen-A Ice Shelf, Antarctic Peninsula. These accumulations form a complex of debris bands extending parallel to the front of the ice shelf for several kilometres. Landsat imagery shows that the debris bands originated as lateral moraines along the Nordenskjöld Coast. Almost 80% of clasts sampled from these debris accumulations have shape/roundness characteristics consistent with glacier transport in the zone of basal traction. Angular and very angular clasts account for 15% and 22% of clasts in the pebble- and cobble/boulder-sized fractions, respectively, and originated by rockfall from valley/nunatak sides, with subsequent passive glacier transportation. Lithological analysis indicates that the debris is derived locally from the Nordenskjöld Coast, Cape Fairweather region and interior of the Antarctic Peninsula. Episodic melt-out and resedimentation of this debris from the front of the ice shelf would deliver pulses of coarse-grained sediment to the sea floor. Therefore, coarse-grained debris can also be released along the calving margin of small polar ice shelves fringing mountainous terrain, and could potentially be confused with sediment deposited at the grounding line of Antarctic ice-shelves. Sedimentological criteria to differentiate between these environments are proposed in this paper.

Abstract Thematic maps are important for a range of disciplines including spatial planning and ecosystem status assessments. Despite an increasing focus on accuracy assessment methods to ensure maps are fit for purpose, the adoption of these recommendations has not been widespread. We present a methodology which utilises bootstrap aggregation and adheres to recommended practices for accuracy assessments. Furthermore, additional information is extracted from the model outputs to produce spatial maps of confidence also supporting map interpretation. The methodology has been applied to two study sites using both pixel-based and object-based units of analyses. Accuracy assessments for both study sites identified the classes that were responsible for most of the map error. In addition, spatially explicit confidence maps supported our understanding of the sources of error. This paper provides a useful methodology to improve accuracy assessment and reporting and is well suited to studies where groundtruth data are limited.

Primary funding for the SOCAL-BRS project was initially provided by the U.S. Navy’s Chief of Naval Operations Environmental Readiness Division and subsequently by the U.S. Navy's Living Marine Resources Program. This study measured the degree of behavioral responses in blue whales (Balaenoptera musculus) to controlled noise exposure off the southern California coast. High-resolution movement and passive acoustic data were obtained from non-invasive archival tags (n=42) whereas surface positions were obtained with visual focal follows. Controlled exposure experiments (CEEs) were used to obtain direct behavioral measurements before, during and after simulated and operational military mid-frequency active sonar (MFAS), pseudorandom noise (PRN) and controls (no noise exposure). For a subset of deep-feeding animals (n=21), active acoustic measurements of prey were obtained and used as contextual covariates in response analyses. To investigate potential behavioral changes within individuals as a function of controlled noise exposure conditions, two parallel analyses of time-series data for selected behavioral parameters (e.g. diving, horizontal movement and feeding) were conducted. This included expert scoring of responses according to a specified behavioral severity rating paradigm and quantitative change-point analyses using Mahalanobis distance statistics. Both methods identified clear changes in some conditions. More than 50% of blue whales in deep-feeding states responded during CEEs, whereas no changes in behavior were identified in shallow-feeding blue whales. Overall, responses were generally brief, of low to moderate severity, and highly dependent on exposure context such as behavioral state, source-to-whale horizontal range and prey availability. Response probability did not follow a simple exposure–response model based on received exposure level. These results, in combination with additional analytical methods to investigate different aspects of potential responses within and among individuals, provide a comprehensive evaluation of how free-ranging blue whales responded to mid-frequency military sonar. Postprint Peer reviewed

Diatoms exist in almost every aquatic regime; they are responsible for ∼20% of global carbon fixation and ∼25% of global primary production, and are regarded as a key food for copepods, which are subsequently consumed by larger predators such as fish and marine mammals. A decreasing abundance and a vulnerability to climatic change in the North Atlantic Ocean have been reported in the literature. In the present work, a data matrix composed of concurrent satellite remote sensing and Continuous Plankton Recorder (CPR) in situ measurements was collated for the same spatial and temporal coverage in the Northeast Atlantic. Artificial neural networks (ANNs) were applied to recognize and learn the complex non-monotonic and non-linear relationships between diatom abundance and spatiotemporal environmental factors. Because of their ability to mimic non-linear systems, ANNs proved far more effective in modelling the diatom distribution in the marine ecosystem. The results of this study reveal that diatoms have a regular seasonal cycle, with their abundance most strongly influenced by sea surface temperature (SST) and light intensity. The models indicate that extreme positive SSTs decrease diatom abundances regardless of other climatic conditions. These results provide information on the ecology of diatoms that may advance our understanding of the potential response of diatoms to climatic change.

Bats and birds are key providers of ecosystem services in forests. How climate and habitat jointly shape their communities is well studied, but whether biotic predictors from other trophic levels may improve bird and bat diversity models is less known, especially across large bioclimatic gradients. Here, we achieved multi-taxa surveys in 209 mature forests replicated in six European countries from Spain to Finland, to investigate the importance of biotic predictors (i.e. the abundance or activity of defoliating insects, spiders, earthworms and wild ungulates) for bat and bird taxonomic and functional diversity. We found that nine out of 12 bird and bat diversity metrics were best explained when biotic factors were added to models including climate and habitat variables, with a mean gain in explained variance of 38% for birds and 15% for bats. Tree functional diversity was the most important habitat predictor for birds, while bats responded more to understorey structure. The best biotic predictors for birds were spider abundance and defoliating insect activity, while only bat functional evenness responded positively to insect herbivory. Accounting for potential biotic interactions between bats, birds and other taxa of lower trophic levels will help to understand how environmental changes along large biogeographical gradients affect higher-level predator diversity in forest ecosystems.

Hydroxyl airglow temperatures measured over Davis station, Antarctica (68°S, 78°E) in 2002 are compared to an 8‐year climatological mean. The 2002 winter average temperature was 5.1 ± 0.8K warmer than the climatological mean. This anomaly is a factor of two larger than what can be attributed to solar flux increases. Of the 210 nightly averages obtained, 72 (34%) exceeded the climatological maximum, primarily in two unusually warm intervals in late‐May to early‐June and in mid‐July. An unusually cold interval (10 nights below the climatological minimum) coincided with a climatological dip in mid‐August. Temperature oscillations of 15–20 K amplitude, extending over 4 cycles across the Sep–Oct stratospheric warming correlate with Rothera temperatures and Davis mesospheric winds and are consistent with a 14‐day westward propagating zonal planetary wave number 1.