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Covid-19 left many employees with life-altering challenges— deaths or illnesses of loved ones, health problems, and economic upheavals. Even during ordinary years, adverse events affect around 50% ...

Evidence indicates that Antarctic minke whales (AMWs) in the Ross Sea affect the foraging behaviour, especially diet, of sympatric Adélie penguins (ADPEs) by, we hypothesize, influencing the availability of prey they have in common, mainly crystal krill. To further investigate this interaction, we undertook a study in McMurdo Sound during 2012–2013 and 2014–2015 using telemetry and biologging of whales and penguins, shore-based observations and quantification of the preyscape. The 3D distribution and density of prey were assessed using a remotely operated vehicle deployed along and to the interior of the fast-ice edge where AMWs and ADPEs focused their foraging. Acoustic surveys of prey and foraging behaviour of predators indicate that prey remained abundant under the fast ice, becoming successively available to air-breathing predators only as the fast ice retreated. Over both seasons, the ADPE diet included less krill and more Antarctic silverfish once AMWs became abundant, but the penguins' foraging behaviour (i.e. time spent foraging, dive depth, distance from colony) did not change. In addition, over time, krill abundance decreased in the upper water column near the ice edge, consistent with the hypothesis (and previously gathered information) that AMW and ADPE foraging contributed to an alteration of prey availability.

Predators impact preyscapes (3-D distribution of forage species) by consuming prey according to their abilities or by altering prey behavior as they avoid being consumed. We elucidate prey (Antarctic silverfish[Pleuragramma antarctica] and crystal krill[Euphausia chrystallorophias]) responses to predation associated with the marginal ice zone (MIZ) of the McMurdo Sound, Antarctica, polynya. Prey abundance and habitat was sampled across a 30 × 15 km area by remotely-operated vehicle, and included locations that were accessible (ice edge) or inaccessible (solid fast ice) to air-breathing predators. Prey and habitat sampling coincided with bio-logging of Adélie penguins and observations of other air-breathing predators (penguins, seals, and whales), all of which were competing for the same prey. Adélie penguins dived deeper, and more frequently, near the ice edge. Lowered abundance of krill at the ice edge indicated they were depleted or were responding to increased predation and/or higher light levels along the ice edge. Penguin diet shifted increasingly to silverfish from krill during sampling, and was correlated with the arrival of krill-eating whales. Behaviorally-mediated, high trophic transfer characterizes the McMurdo Sound MIZ, and likely other MIZs, warranting more specific consideration in food web models and conservation efforts.

In McMurdo Sound, Antarctica, fine-scale bathymetry is poorly defined, and benthic communities at water depths over 30 m have not been well described. We describe the benthic communities on two previously unknown bathymetric highs, sampled in 2012 and 2014, using scuba divers, a remotely operated vehicle, and a specially designed time-lapse camera system (SeeStar). One site (Mystery Peak) was capped by a dense thicket of the sponge Homaxinella balfourensis, a temporally variable community that likely formed in response to iceberg disturbance. Below the H. balfourensis cap (at 40 m) and at the second site (Tongue Peak, 70 m), the communities conformed to a known ecological pattern driven by food availability from benthic diatoms. Overall, mixed hydroids and bryozoans were the dominant organisms, and at greater depths the sponge Rosella podagrosa also became abundant. Over time, there were only minor changes in these communities on isolated bathymetric highs. Ice is a physical factor that interacts with depth and influences benthic communities through disturbance by icebergs and anchor ice, and through food supply by sea ice coverage. The SeeStar time-lapse camera system performed exceptionally and opens up opportunities for new winter observations in the Antarctic.

Self-interacting dark matter (SIDM) cosmologies admit an enormous diversity of dark matter (DM) halo density profiles, from low-density cores to high-density core-collapsed cusps. The possibility of the growth of high central density in low-mass halos, accelerated if halos are subhalos of larger systems, has intriguing consequences for small-halo searches with substructure lensing. However, following the evolution of $\lesssim 10^8 M_\odot$ subhalos in lens-mass systems ($\sim 10^{13}M_\odot$) is computationally expensive with traditional N-body simulations. In this work, we develop a new hybrid semi-analytical + N-body method to study the evolution of SIDM subhalos with high fidelity, from core formation to core-collapse, in staged simulations. Our method works best for small subhalos ($\lesssim 1/1000$ host mass), for which the error caused by dynamical friction is minimal. We are able to capture the evaporation of subhalo particles by interactions with host halo particles, an effect that has not yet been fully explored in the context of subhalo core-collapse. We find three main processes drive subhalo evolution: subhalo internal heat outflow, host-subhalo evaporation, and tidal effects. The subhalo central density grows only when the heat outflow outweighs the energy gain from evaporation and tidal heating. Thus, evaporation delays or even disrupts subhalo core-collapse. We map out the parameter space for subhalos to core-collapse, finding that it is nearly impossible to drive core-collapse in subhalos in SIDM models with constant cross sections. Any discovery of ultra-compact dark substructures with future substructure lensing observations favors additional degrees of freedom, such as velocity-dependence, in the cross section., 25 pages, 15 figures, 2 animations. Matched published version

Circoviridae is a family of circular single-stranded DNA viruses whose members infect a wide variety of hosts. While well characterized in avian and mammalian hosts, little is known about circoviruses associated with Antarctic animals. From 48 Weddell seal (Leptonychotes weddellii) fecal samples collected on the sea ice in McMurdo between Nov 2014 and Dec 2014, we identified and determined the genomes of novel viruses that fall within two genera of the family Circoviridae, i.e. Circovirus (n = 7) and Cyclovirus (n = 45). We named these viruses as werosea circovirus (WerCV) and werosea cyclovirus (WerCyV). The genomes of WerCV and WerCyV share ~63–64% genome-wide pairwise identity with classified circoviruses and cycloviruses, respectively. Based on the species demarcation threshold of 80% for members of the Circoviridae, the genomes of WerCV and WerCyV represent new species in their respective genera. Evidence indicated recombination in five of the 45 WerCyV genomes identified in this study. These are the first circoviruses found associated with Antarctic pinnipeds, adding to those recently identified associated with Adelie (Pygoscelis adeliae) and chinstrap penguins (P. antarcticus).

Habitats under ice shelves are minimally explored, primarily because of technological limitations. These areas are separated from photosynthetic primary productivity by thick ice and distance to open water. Nevertheless, a diverse macrofaunal benthic community was discovered at 188 m depth, 80 km back from the edge of the McMurdo Ice Shelf. The general habitat was fine sediment with occasional dropstones, and dominant taxa were polychaetes and brittle stars, with alcyonacean soft corals and anemones on hard substrates. Gelatinous animals were abundant near the seafloor, and possibly part of a food web that supports the benthic community.

Fast ice plays important physical and ecological roles: as a barrier to wind, waves and radiation, as both barrier and safe resting place for air-breathing animals, and as substrate for microbial communities. While sea ice has been monitored for decades using satellite imagery, high-resolution imagery sufficient to distinguish fast ice from mobile pack ice extends only back toc.2000. Fast ice trends may differ from previously identified changes in regional sea ice distributions. To investigate effects of climate and human activities on fast ice dynamics in McMurdo Sound, Ross Sea, the sea and fast ice seasonal events (1978–2015), ice thicknesses and temperatures (1986–2014), wind velocities (1973–2015) and dates that an icebreaker annually opens a channel to McMurdo Station (1956–2015) are reported. A significant relationship exists between sea ice concentration and fast ice extent in the Sound. While fast/sea ice retreat dates have not changed, fast/sea ice reaches a minimum later and begins to advance earlier, in partial agreement with changes in Ross Sea regional pack ice dynamics. Fast ice minimum extent within McMurdo Sound is significantly correlated with icebreaker arrival date as well as wind velocity. The potential impacts of changes in fast ice climatology on the local marine ecosystem are discussed.

The ARTEMIS docking system demonstrates autonomous docking capability applicable to robotic exploration of sub-ice oceans and sub-glacial lakes on planetary bodies, as well as here on Earth. In these applications, melted or drilled vertical access shafts restrict vehicle geometry as well as the in-water infrastructure that may be deployed. The ability of the vehicle to return reliably and precisely to the access point is critical for data return, battery charging, and/or vehicle recovery. This paper presents the mechanical, sensor, and software components that make up the ARTEMIS docking system, as well as results from field deployment of the system to McMurdo Sound, Antarctica in the austral spring of 2015. The mechanical design of the system allows the vehicle to approach the dock from any direction and to pitch up after docking for recovery through a vertical access shaft. It uses only a small volume of in-water equipment and may be deployed through a narrow vertical access shaft. The software of the system reduces position estimation error with a hierarchical combination of dead reckoning, acoustic aiding, and machine vision. The system provides critical operational robustness, enabling the vehicle to return autonomously and precisely to the access shaft and latch to the dock with no operator input.

Recombinant adeno-associated virus (rAAV) has been widely used as a viral vector across mammalian biology and has been shown to be safe and effective in human gene therapy. We demonstrate that neural progenitor cells (NPCs) and immature dentate granule cells (DGCs) within the adult murine hippocampus are particularly sensitive to rAAV-induced cell death. Cell loss is dose dependent and nearly complete at experimentally relevant viral titers. rAAV-induced cell death is rapid and persistent, with loss of BrdU-labeled cells within 18 hours post-injection and no evidence of recovery of adult neurogenesis at 3 months post-injection. The remaining mature DGCs appear hyperactive 4 weeks post-injection based on immediate early gene expression, consistent with previous studies investigating the effects of attenuating adult neurogenesis. In vitro application of AAV or electroporation of AAV2 inverted terminal repeats (ITRs) is sufficient to induce cell death. Efficient transduction of the dentate gyrus (DG)—without ablating adult neurogenesis—can be achieved by injection of rAAV2-retro serotyped virus into CA3. rAAV2-retro results in efficient retrograde labeling of mature DGCs and permits in vivo 2-photon calcium imaging of dentate activity while leaving adult neurogenesis intact. These findings expand on recent reports implicating rAAV-linked toxicity in stem cells and other cell types and suggest that future work using rAAV as an experimental tool in the DG and as a gene therapy for diseases of the central nervous system (CNS) should be carefully evaluated.

We observed high diversity (species density) of infaunal invertebrates from the mid-shelf (50 m) to the upper slope (325 m) with high abundance and low dominance along 4 depth transects ranging from 10 to 2000 m. The highest shallow water diversity recorded worldwide was at the shelf-slope break (109–150 m) with a peak of 185 species 0.1 m-2 (449 m-2, this work and Oliver JS, Hammerstrom K, McPhee-Shaw E, Slattery P, Oakden J, Kim S, Hartwell SI, Mar Ecol 32:278–288, 2011). The peak included a large number of species and individuals of small nestling amphipods. The most abundant genera were Photis, Aoroides, and Gammaropsis. The percentages of crustacean species (40%) and individuals (60%) were extremely high as well. A large caprellid amphipod, Tritella tenuissima, was the most abundant animal found in our survey (387 individuals 0.1 m-2), and characterized the mixed gravel bottoms on the upper slope. We discovered a dense tube mat of relatively large ampeliscid amphipods at the upper margin of the oxygen minimum zone (700 m). This was the most distinct community cluster and was dominated by Ampelisca unsocalae and Byblis barbarensis. The percentage of crustacean species (40%) and individuals (67%) were also highest here. This is the only ampeliscid tube mat known from deep water and is ecologically similar to extensive shallow-water ampeliscid mats in the Bering and Chukchi Seas, the primary feeding grounds of gray whales. The diverse and abundant continental margin communities occurred in a dynamic, current-swept upwelling center with complex topography. Diversity decreased below the upper slope and on the wave-swept inner shelf, where there was another dramatic crustacean pattern. These shifting sands were dominated by burrowing amphipods (phoxocephalids and haustoriids) and small ostracods in the 1970s that were rare in the present survey. In total, we collected 938 invertebrate species, including 431 polychaetes, 270 crustaceans, 171 mollusks, and 38 echinoderms in 123 samples. More than any other taxa, the crustaceans characterized the most unique and interesting community patterns along the continental margin of the Monterey Bay area.

Sponges are the most conspicuous component of the Antarctic benthic ecosystem, a system under stress both from climate change and fishing activities. Observations over four decades are compiled and reveal extremely episodic sponge recruitment and growth. Recruitment occurred under different oceanographic conditions on both sides of McMurdo Sound. Most of the sponges appear to have recruited in the late 1990s–2000. Observations from 2000 to 2010 follow thirty years of relative stasis with very little sponge recruitment or growth followed by a general pattern of recruitment by some forty species of sponges. That there was almost no recruitment observed on natural substrata emphasizes the contrast between potential and realized recruitment. This unique data set was derived from a region noted for physical stasis, but the episodic ecological phenomena highlight the importance of rare events. Against a background of intermittent food resources and the low metabolic costs of stasis, understanding the causes of irregular larval supply, dispersal processes, recruitment success and survivorship becomes critical to predicting ecosystem dynamics and resilience in response to increasing environmental change. Our time-series emphasizes that long-term data collection is essential for meaningful forecasts about environmental change in the unique benthic ecosystems of the Antarctic shelf.

Large floods bringing significant sediments into the coastal oceans have not been observed in Antarctica. We report evidence of a large flood event depositing over 50 cm of sediment onto the nearshore benthic habitat at Salmon Bay, Antarctica, between 1990 and 2010. Besides direct observations of the sedimentation, the evidence involves a debris flow covering old tyre tracks from the early 1960s, as well as evidence of a considerable amount of sediment transported onto the Salmon Creek delta. We believe that the flood was sourced from the Salmon Glacier and possibly the smaller Blackwelder Glacier. Such floods will be more common in the future and it is important to better understand their ecological impacts with good monitoring programmes.

International audience; Western Pacific hydrothermal vents will soon be subjected to deep-sea mining and peripheral sites are considered the most practical targets. The limited information on community dynamics and temporal change in these communities makes it difficult to anticipate the impact of mining activities and recovery trajectories. We studied community composition of peripheral communities along a cline in hydrothermal chemistry on the Eastern Lau Spreading Center and Valu Fa Ridge (ELSC-VFR) and also studied patterns of temporal change. Peripheral communities located in the northern vent fields of the ELSC-VFR are significantly different from those in the southern vent fields. Higher abundances of zoanthids and anemones were found in northern peripheral sites and the symbiont-containing mussel Bathymodiolus brevior, brisingid seastars and polynoids were only present in the northern peripheral sites. By contrast, certain faunal groups were seen only in the southern peripheral sites, such as lollipop sponges, pycnogonids and ophiuroids. Taxonomic richness of the peripheral communities was similar to that of active vent communities, due to the presence of non-vent endemic species that balanced the absence of species found in areas of active venting. The communities present at waning active sites resemble those of peripheral sites, indicating that peripheral species can colonize previously active vent sites in addition to settling in the periphery of areas of venting. Growth and mortality were observed in a number of the normally slow-growing cladorhizid stick sponges, indicating that these animals may exhibit life history strategies in the vicinity of vents that differ from those previously recorded. A novel facultative association between polynoids and anemones is proposed based on their correlated distributions.

Polar ecosystems are bellwether indicators of climate change and offer insights into ecological resilience. In this study, we describe contrasting responses to an apparent regime shift of two very different benthic communities in McMurdo Sound, Antarctica. We compared species‐specific patterns of benthic invertebrate abundance and size between the west (low productivity) and east (higher productivity) sides of McMurdo Sound across multiple decades (1960s–2010) to depths of 60 m. We present possible factors associated with the observed changes. A massive and unprecedented shift in sponge recruitment and growth on artificial substrata observed between the 1980s and 2010 contrasts with lack of dramatic sponge settlement and growth on natural substrata, emphasizing poorly understood sponge recruitment biology. We present observations of changes in populations of sponges, bryozoans, bivalves, and deposit‐feeding invertebrates in the natural communities on both sides of the sound. Scientific data for Antarctic benthic ecosystems are scant, but we gather multiple lines of evidence to examine possible processes in regional‐scale oceanography during the eight years in which the sea ice did not clear out of the southern portion of McMurdo Sound. We suggest that large icebergs blocked currents and advected plankton, allowed thicker multi‐year ice, and reduced light to the benthos. This, in addition to a possible increase in iron released from rapidly melting glaciers, fundamentally shifted the quantity and quality of primary production in McMurdo Sound. A hypothesized shift from large to small food particles is consistent with increased recruitment and growth of sponges on artificial substrata, filter‐feeding polychaetes, and some bryozoans, as well as reduced populations of bivalves and crinoids that favor large particles, and echinoderms Sterechinus neumayeri and Odontaster validus that predominantly feed on benthic diatoms and large phytoplankton mats that drape the seafloor after spring blooms. This response of different guilds of filter feeders to a hypothesized shift from large to small phytoplankton points to the enormous need for and potential value of holistic monitoring programs, particularly in pristine ecosystems, that could yield both fundamental ecological insights and knowledge that can be applied to critical conservation concerns as climate change continues.

Background Sepsis is a potentially life-threatening, systemic complication of infection. Rapid intervention is critical to reduce morbidity and mortality; however, early recognition of sepsis is challenging due to a highly variable and nonspecific presentation. Recognition is particularly problematic in ambulatory (walk-in) patients who receive minimal to no medical attention prior to ED presentation. There is limited literature addressing sepsis intervention among the ambulatory population in the ED. Our organization has employed an electronic, nurse-driven sepsis screening tool into the triage process for all ambulatory patients who present to the ED. Methods This was a retrospective, quasi-experimental study conducted from November 2015 to May 2018 in three consecutive timeframes: pre-implementation (12 months), implementation (7 months), and post-implementation (12 months). Adult ambulatory ED patients were included if they had a coded diagnosis of sepsis, septic shock, or an infectious syndrome, had fever or hypothermia and systemic inflammatory response syndrome signs on presentation. The primary outcome measure was hourly time interval to antibiotic administration from time of ED registration. Results A total of 902 patients were included with 286, 208, and 408 patients in the pre-implementation, implementation and post-implementation cohorts, respectively. Baseline characteristics including comorbid conditions and infection source were similar between cohorts. The primary outcome of hourly time interval to antibiotic administration was significantly different (P = 0.044) between the three cohorts with the most substantial increase in administration specifically in the less than 1-hour interval. Between the pre-implementation, implementation, and post-implementation cohorts, significant decreases were observed in mean time to fluids (3.6, 3.0, and 2.5 hours, respectively, P = 0.003) and average length of stay (5.5, 5.8, and 4.2 days, respectively, P < 0.001) and a significant increase was observed in ED sepsis alert activations (26%, 48%, 51%, respectively, P < 0.001). Conclusion A nurse-driven electronic time-of-triage sepsis screening tool improved timely recognition and intervention in ambulatory ED patients with suspected sepsis. Disclosures All authors: No reported disclosures.

Historical persistent organic pollutants (POPs) are banned from Antarctica under international treaty; but contemporary-use POPs can enter as additives within polymer and textile products. Over their useful lives these products may release additives in-situ. Indeed, we observed 226 and 109 ng/g dry weight (dw) of the total concentrations of α-, β- and γ-hexabromocyclododecane (HBCD) in indoor dust from McMurdo Station (U.S.) and Scott Station (New Zealand), respectively. Sewage sludge collected from wastewater treatment facilities at these stations exhibited ∑HBCD of 45 and 69 ng/g dw, respectively. Contaminants originally within the bases may exit to the local outdoor environment via wastewaters. Near McMurdo, maximum ∑HBCD levels in surficial marine sediments and aquatic biota (invertebrates and fish) were 2350 ng/g (total organic carbon basis) and 554 ng/g lipid weight, respectively. Levels declined with distance from McMurdo. Our results illustrate that Antarctic research stations serve as local HBCD sources to the pristine Antarctic environment.

The viruses circulating among Antarctic wildlife remain largely unknown. In an effort to identify viruses associated with Weddell seals (Leptonychotes weddellii) inhabiting the Ross Sea, vaginal and nasal swabs, and faecal samples were collected between November 2014 and February 2015. In addition, a Weddell seal kidney and South Polar skua (Stercorarius maccormicki) faeces were opportunistically sampled. Using high throughput sequencing, we identified and recovered 152 anellovirus genomes that share 63–70% genome-wide identities with other pinniped anelloviruses. Genome-wide pairwise comparisons coupled with phylogenetic analysis revealed two novel anellovirus species, tentatively named torque teno Leptonychotes weddellii virus (TTLwV) -1 and -2. TTLwV-1 (n = 133, genomes encompassing 40 genotypes) is highly recombinant, whereas TTLwV-2 (n = 19, genomes encompassing three genotypes) is relatively less recombinant. This study documents ubiquitous TTLwVs among Weddell seals in Antarctica with frequent co-infection by multiple genotypes, however, the role these anelloviruses play in seal health remains unknown.

A new class of small, hand-deployable underwater vehicles is playing an increasingly important role in oceanographic science. Due to the small nature of these vehicles, traditional incorporation of oceanographic instrumentation into a vehicle's body can result in a device too massive or cumbersome to deployed by hand. In this paper, we present a towed instrument package, FATTI, as an alternative means of sensor integration for small underwater vehicles, specifically for the Remotely Operated Vehicle (ROV) SCINI. The flexibly attached instrument package is comprised of a 120 kHz scientific echosounder and fluorometer, and was deployed in the McMurdo Sound, Antarctica to map the spatial and temporal dynamics of krill, fishes, and phytoplankton. The tow package proved modular and fieldable, and performed over 100 dives during the 2012/13 and 2014/15 Antarctic field seasons.

The Lau back-arc spreading center exhibits gradients in hydrothermal vent habitat characteristics from north to south. Biological zonation within a few meters of vents has been described as temperature driven. We constructed georeferenced photomosaics of the seafloor out to tens of meters beyond vents to describe peripheral zonation and explore correlations between environmental conditions and the biological community. Cluster analysis separated northern sites from southern sites, corresponding to a break in substrate from basalt in the north to andesite in the south. Northern sites were dominated by anemones, and southern by sponges. A previous suggestion that dominants may be dependent on friability of the substrate was not supported; when visually distinguishable, individual species within taxa showed different patterns. Northern sites hosted proportionally more suspension feeding species. Sulfide that can support microbial food sources is at higher concentrations at these sites, though bathymetry that may enhance bottom currents is less rugged. Northern sites had higher diversity that may result from the overall northwards flow, which would generally permit easier dispersal downcurrent, though we observed no difference in dispersal strategies at different sites.

Species density of macrofaunal invertebrates living in marine soft sediments was highest at the shelf-slope break (100‐150 m) in Monterey Bay (449 m )2 ). There were 337 species m )2 in the mid-shelf mud zone (80 m). There were fewer species along the slope: 205 m )2 from the lower slope (950-2000 m) and 335 m )2 on the upper slope (250-750 m). Species density was highest inside the bay (328-446 m )2 ) compared to outside (336-339 m )2 ), when examining samples at selected water depths (60-1000 m). There was little difference in local species density from 1 km of shoreline compared to regional species density along 1000 km of shoreline at both shelf and slope depths. The highest species densities worldwide in the literature are recorded along the Carolina slope in the Atlantic Ocean, where peak species density (436/0.81 m 2 ) at 800 m and values at the largest sample areas are similar to those on the Monterey Bay shelf. We speculate that the highest species densities occur where ocean water exchanges energy with shoaling topography at the continental margin, bringing more food to the benthos ‐ areas such as the very productive waters in the upwelling system of Monterey Bay.

Despite widespread interest in using human induced pluripotent stem cells (hiPSCs) in neurological disease modeling, a suitable model system to study human neuronal connectivity is lacking. Here, we report a comprehensive and efficient differentiation paradigm for hiPSCs that generate multiple CA3 pyramidal neuron subtypes as detected by single-cell RNA sequencing (RNA-seq). This differentiation paradigm exhibits characteristics of neuronal network maturation, and rabies virus tracing revealed synaptic connections between stem cell-derived dentate gyrus (DG) and CA3 neurons in vitro recapitulating the neuronal connectivity within the hippocampus. Because hippocampal dysfunction has been implicated in schizophrenia, we applied DG and CA3 differentiation paradigms to schizophrenia-patient-derived hiPSCs. We detected reduced activity in DG-CA3 co-culture and deficits in spontaneous and evoked activity in CA3 neurons from schizophrenia-patient-derived hiPSCs. Our approach offers critical insights into the network activity aspects of schizophrenia and may serve as a promising tool for modeling diseases with hippocampal vulnerability. VIDEO ABSTRACT.

Synopsis Community structure and diversity are influenced by patterns of disturbance and input of food. In Antarctica, the marine ecosystem undergoes highly seasonal changes in availability of light and in primary production. Near research stations, organic input from human activities can disturb the regular productivity regime with a consistent input of sewage. McMurdo Sound has both high-productivity and low-productivity habitats, thereby providing an ideal test bed for community recovery dynamics under polar conditions. We used experimental manipulations of the subtidal communities to test the hypotheses that (1) benthic communities respond differently to disturbance from organic enrichment versus burial and (2) community response also varies in areas with different natural patterns of food supply. Both in lowand high-food habitats, the strongest community response was to organic enrichment and resulted in dominance of typical organic-enrichment specialists. In habitats with highly seasonal productivity, community response was predictable and recovery was rapid. In habitats with low productivity, community variability was high and caging treatments suggested that inconsistencies were due to patchy impacts by scavengers. In areas normally subject to regular organic enrichment, either from primary production or from further up the food web (defecation by marine mammals), recovery of benthic communities takes only years even in a polar system. However, a low-productivity regime is as common in near shore habitats around the continent; under these conditions, recovery of benthic communities from disturbance is likely to be much slower and follow a variable ecological trajectory.

This study examined the macrofaunal communities of two shallow hydrothermal vent areas, in Bahia Concepcion (12 m depth), Mexico, and White Point (8 m depth), California. We tested whether the infaunal community compositions in these systems were different from the surrounding communities, and if the observed differences were related to pore-water and other habitat variables. A combination of temperature, hydrogen sulfide, salinity, and pH influenced the species composition within zones of venting. The vent communities, with a few exceptions, were a sub-set of the surrounding community, represented by a limited diversity of outside fauna in lower abundance. Examination of infaunal life-histories revealed that tube-dwelling and mobile species represented a relatively higher proportion of the fauna near vents than away. Tubes were proposed as a beneficial life-history strategy to inhabitants of the high temperatures of Bahia Concepcion, but did not predominate in the high sulfide sediments of White Point. Furthermore, there was no evidence for chemosynthetic strategies amongst the shallow vent infauna, unlike fauna at deep-sea hydrothermal vents and cold seeps.

The Antarctic shelf fauna is isolated from other continental shelf faunas both physically by distance, and oceanographically by the Antarctic circumpolar current (ACC). To elucidate the relative importance of these two isolating mechanisms, we used the seastar fauna of the south-Atlantic sub-Antarctic islands to address the hypothesis that the ACC is dominant in controlling the distribution pattern of Antarctic fauna. We expected that seastar faunas from islands on the high latitude side of the ACC would show more similarities to each other than to faunas from islands on the low latitude side. The alternative isolation by distance model predicted that the island furthest from others would have the most unique fauna. For shelf-depth (

We describe in situ observations on nesting by the Scotia Sea (or blackfin) icefish Chaenocephalus aceratus (Lonnberg) that constitute the first substantive evidence of egg brooding and parental care by species of the family Channichthyidae. At Boutetoya Island six fish, all apparently male, were observed guarding egg nests at depths of 141–148 m during an ROV deployment. Eggs were laid as aggregated, round masses (~20–25 cm diameter) in shallow, circular depressions (~1-m diameter, ~20-cm depth) that were probably excavated by the parent(s) to protect the nests. The fish guardians remained tenaciously in contact with the eggs despite disturbances caused by the ROV, reacting to this threat with stress and defense behaviors. Because brooding fishes are more susceptible to the population impacts from trawl fisheries, we argue that this life history should be kept in mind in designing management schemes.

A benthic habitat along the coast of McMurdo Station in the Ross Sea, Antarctica is enriched by sewage from the station and altered by hydrocarbons and heavy metals in an adjacent historic dumpsite. We report on 10 years of change in the benthic communities from 1988 to 1998 and compare enrichment effects at Australia's Casey Station, East Antarctica. Despite being 14 km apart, reference communities upcurrent and downcurrent of McMurdo Station remained closely similar over time, dominated in all years by a tube building polychaete, Spiophanes tcherniae. The community bordering McMurdo Station was generally a third as abundant as communities at the reference sites over the decade of sampling, although diversity was as high or higher, except in the most contaminated areas. In 1992, organic enrichment of the outfall community intensified and within the year, the opportunistic polychaetes Aphelochaeta sp., Ophryotrocha notialis, Capitella perarmata, and Leitoscoloplos kerguelensis became dominant. Since 1996, two of the three enriched communities have increased in resemblance to the reference communities. Given the observed responsiveness of the benthos to the outfall so far, further changes are anticipated within the year following implementation of sewage treatment in 2003. Organic enrichment by McMurdo Station has had a greater impact on benthic community structure than at Australia's Casey Station.

Predicting how communities respond to multiple, potentially interacting chemical stressors is inherently difficult because community structure and dynamics, the chemical properties of contaminants, and biological-chemical interactions vary with environmental conditions. Using a field experiment conducted in Antarctica, we tested whether 3 phyla of benthic soft-sediment marine invertebrates—annelids, arthropods, and echinoderms —respond differently to 2 common forms of contamination, organic enrichment and toxic contamination. Based on life history strategies and physiological tolerances to contaminants, we hypothesized that the principal responses of the 3 phyla would be: (1) enhanced abundance of annelids in organically enrichment sediments and (2) decreased abundance of arthropods and echinoderms in toxic metal contamination. Sediment treatments were established in the field experiment with an orthogonal combination of 3 levels of total organic carbon (TOC; 0, 1, and 2% by weight) and copper (Cu; 0, 100, and 500 µg Cu g -1 sedi- ment), and colonization patterns were observed after 1 yr. Densities of annelids (mainly polychaetes) increased with TOC across all levels of Cu. Arthropods and echinoderms decreased with Cu, but responded variably to TOC, based largely on differences in habitat preferences exhibited by epifau- nal and infaunal species. Small subsurface arthropod species (amphipods, isopods, cumaceans, and ostracods) decreased in high organic loading, due to induction of and exposure to hypoxia and hydro- gen sulfide, but large surface deposit-feeding echinoderms (asteroids and echinoids) responded positively to increased carbon food supply. We present a predictive model based on assessment of benthic community structure conducted at the taxonomic level of phyla that could be used to link cause and effect for multiple chemical stressors in marine ecosystems.

The impacts of two Antarctic stations in different regions, on marine sediment macrofaunal communities were compared: McMurdo, a very large station in the Ross Sea; and Casey, a more typical small station in East Antarctica. Community structure and diversity were compared along a gradient of anthropogenic disturbance from heavily contaminated to uncontaminated locations. We examined some of the inherent problems in comparing data from unrelated studies, such as different sampling methods, spatial and temporal scales of sampling and taxonomic uncertainty. These issues generated specific biases which were taken into account when interpreting patterns. Control sites in the two regions had very different communities but both were dominated by crustaceans. Community responses to anthropogenic disturbance (sediment contamination by metals, oils and sewage) were also different. At McMurdo the proportion of crustaceans decreased in disturbed areas and polychaetes became dominant, whereas at Casey, crustaceans increased in response to disturbance, largely through an increase in amphipods. Despite differing overall community responses there were some common elements. Ostracods, cumaceans and echinoderms were sensitive to disturbance in both regions. Capitellid, dorvelleid and orbiniid polychaetes were indicative of disturbed sites. Amphipods, isopods and tanaids had different responses at each station. Biodiversity and taxonomic distinctness were significantly lower at disturbed locations in both regions. The size of the impact, however, was not related to the level of contamination, with a larger reduction in biodiversity at Casey, the smaller, less polluted station. The impacts of small stations, with low to moderate levels of contamination, can thus be as great as those of large or heavily contaminated stations. Regional broad scale environmental influences may be important in determining the composition of communities and thus their response to disturbance, but there are some generalizations regarding responses which will aid future management of stations.

Distributions of larvae of benthic invertebrates and other planktonic organisms (holoplankton) were determined near hydrothermal vents along the East Pacific Rise (9°50′N) and combined with current meter records to estimate the extent and direction of transport in near-bottom flows. Diurnal tidal currents were strong enough to transport larvae substantial distances (up to 2 km) across the ridge axis during a single 12-h excursion. Potential longerterm transport in mean flows, however, appeared to be relatively slow (typically less than 1 km d -1 ). The proportion of larvae dispersing in near-bottom flows, as opposed to becoming entrained into the buoyant plume (and transported up out of the near-bottom environment) was estimated for a range of vent community sizes and black-smoker buoyancy fluxes, using a buoyant-plume entrainment model. These estimates suggested that larvae were most often transported in near-bottom currents, but that plume-level dispersal dominated for short periods of the tidal cycle (0.5–3 h) when the currents were slower than 1–2 cm s -1 . The plume exit temperature also affects entrainment rate, so the proportion of larvae in each transport pathway (near-bottom flows and buoyant plumes) should vary substantially among vent habitats surrounding different temperature vents. The presence of certain holoplankton groups in diffuse vent flows, and their elevated abundances within the axial ridge valley, raises the possibility that these groups may be specifically associated with vent habitats.

Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.