The evolutionary origins of the Southern Ocean philobryid bivalves: hidden biodiversity, ancient persistence

Philobryids (Bivalvia: Arcoida) are one of the most speciose marine bivalve families in the Southern Ocean and are common throughout the Southern Hemisphere. Considering this diversity and their brooding reproductive mode (limiting long-distance dispersal), this family may have been present in the Southern Ocean since its inception. However Philobrya and Adacnarca appear only in the Quaternary fossil record of the Antarctic, suggesting a much more recent incursion. Molecular dating provides an independent means of measuring the time of origin and radiation of this poorly known group. Here we present the first combined molecular and morphological investigation of the Philobryidae in the Southern Ocean. Two nuclear loci (18S and 28S) were amplified from 35 Southern Ocean Adacnarca and Philobrya specimens, with a combined sequence length of 2,282 base pairs (bp). Adacnarca specimens (A. nitens and A. limopsoides) were resolved as a strongly supported monophyletic group. Genus Philobrya fell into two strongly supported groups (‘sublaevis’ and ‘magellanica/wandelensis’), paraphyletic with Adacnarca. The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering. Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea. Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current

On the ecological relevance of landscape mapping and its application in the spatial planning of very large marine protected areas

In recent years very large marine protected areas (VLMPAs) have become the dominant form of spatial protection in the marine environment. Whilst seen as a holistic and geopolitically achievable approach to conservation, there is currently a mismatch between the size of VLMPAs, and the data available to underpin their establishment and inform on their management. Habitat mapping has increasingly been adopted as a means of addressing paucity in biological data, through use of environmental proxies to estimate species and community distribution. Small-scale studies have demonstrated environmental-biological links in marine systems. Such links, however, are rarely demonstrated across larger spatial scales in the benthic environment. As such, the utility of habitat mapping as an effective approach to the ecosystem-based management of VLMPAs remains, thus far, largely undetermined. The aim of this study was to assess the ecological relevance of broadscale landscape mapping. Specifically we test the relationship between broad-scale marine landscapes and the structure of their benthic faunal communities. We focussed our work at the sub-Antarctic island of South Georgia, site of one of the largest MPAs in the world. We demonstrate a statistically significant relationship between environmentally derived landscape mapping clusters, and the composition of presence-only species data from the region. To demonstrate this relationship required specific re-sampling of historical species occurrence data to balance biological rarity, biological cosmopolitism, range-restricted sampling and fine-scale heterogeneity between sampling stations. The relationship reveals a distinct biological signature in the faunal composition of individual landscapes, attributing ecological relevance to South Georgia's environmentally derived marine landscape map. We argue therefore, that landscape mapping represents an effective framework for ensuring representative protection of habitats in management plans. Such scientific underpinning of marine spatial planning is critical in balancing the needs of multiple stakeholders whilst maximising conservation payoff

Microplastics in the Antarctic marine system: An emerging area of research

It was thought that the Southern Ocean was relatively free of microplastic contamination; however, recent studies and citizen science projects in the Southern Ocean have reported microplastics in deep-sea sediments and surface waters. Here we reviewed available information on microplastics (including macroplastics as a source of microplastics) in the Southern Ocean. We estimated primary microplastic concentrations from personal care products and laundry, and identified potential sources and routes of transmission into the region. Estimates showed the levels of microplastic pollution released into the region from ships and scientific research stations were likely to be negligible at the scale of the Southern Ocean, but may be significant on a local scale. This was demonstrated by the detection of the first microplastics in shallow benthic sediments close to a number of research stations on King George Island. Furthermore, our predictions of primary microplastic concentrations from local sources were five orders of magnitude lower than levels reported in published sampling surveys (assuming an even dispersal at the ocean surface). Sea surface transfer from lower latitudes may contribute, at an as yet unknown level, to Southern Ocean plastic concentrations. Acknowledging the lack of data describing microplastic origins, concentrations, distribution and impacts in the Southern Ocean, we highlight the urgent need for research, and call for routine, standardised monitoring in the Antarctic marine system

More losers than winners in a century of future Southern Ocean seafloor warming

The waters of the Southern Ocean are projected to warm over the coming century, with potential adverse consequences for native cold-adapted organisms. Warming waters have caused temperate marine species to shift their ranges poleward. The seafloor animals of the Southern Ocean shelf have long been isolated by the deep ocean surrounding Antarctica and the Antarctic Circumpolar Current, with little scope for southward migration. How these largely endemic species will react to future projected warming is unknown. By considering 963 invertebrate species, we show that within the current century, warming temperatures alone are unlikely to result in wholesale extinction or invasion affecting Antarctic seafloor life. However, 79% of Antarctica’s endemic species do face a significant reduction in suitable temperature habitat (an average 12% reduction). Our findings highlight the species and regions most likely to respond significantly (negatively and positively) to warming and have important implications for future management of the region

Benthic ecosystem cascade effects in Antarctica using Bayesian network inference

Funder: British Antarctic Survey Polar Science for Planet Earth Programme.Abstract: Antarctic sea-floor communities are unique, and more closely resemble those of the Palaeozoic than equivalent contemporary habitats. However, comparatively little is known about the processes that structure these communities or how they might respond to anthropogenic change. In order to investigate likely consequences of a decline or removal of key taxa on community dynamics we use Bayesian network inference to reconstruct ecological networks and infer changes of taxon removal. Here we show that sponges have the greatest influence on the dynamics of the Antarctic benthos. When we removed sponges from the network, the abundances of all major taxa reduced by a mean of 42%, significantly more than changes of substrate. To our knowledge, this study is the first to demonstrate the cascade effects of removing key ecosystem structuring organisms from statistical analyses of Antarctica data and demonstrates the importance of considering the community dynamics when planning ecosystem management

Data distribution: Patterns and implications

info:eu-repo/semantics/publishe

Macrobenthic mollusca of the Prince Gustav Channel, eastern Antarctic Peninsula: An area undergoing colonisation

In 2018 RRS James Clark Ross investigated the marine benthic biodiversity of the Prince Gustav Channel area which separates the eastern coast of the Antarctic Peninsula from James Ross Island. The southern end of this channel had been covered by the Prince Gustav Ice Shelf until its collapse in 1995. Benthic samples were collected by an epibenthic sledge at six stations (200–1,200 m depth) in the channel and adjacent Duse Bay. In total 20,307 live collected mollusc specimens belonging to 50 species and 4 classes (Solenogastres, Bivalvia, Gastropoda, and Scaphopoda) were identified. The area may be characterised by it’s low species richness (ranging from 7 to 39 species per station) but high abundances (specifically of the Scaphopods with 11,331 specimens). The functional traits of the community were dominated by motile development and mobility type. Assemblage analyses of the molluscan species abundances within the Prince Gustav Channel stations sit distinct, with no pattern by depth or location. However, when bivalve assemblages were analysed with reference to the wider Weddell Gyre region (15 stations from 300 to 2,000 m depth), the Prince Gustav Channel sits distinct from the other Weddell Gyre stations with a higher dissimilarity between the deeper or more geographically distant areas. The Prince Gustav Channel is undergoing colonisation following the recent ice shelf collapse. With many Antarctic ice shelves threatened under climate warming, this area, with future monitoring, may serve as a case study of benthic faunal succession

Understanding the surface condition of silicone rubber nanocomposite due to corona ageing using afm imaging and libs spectroscopy

Silicone rubber insulators undergo degradation when they are exposed to corona discharges. The present study explores the surface degradation behavior of silicone rubber alumina nanocomposites due to corona ageing using high-frequency AC voltage. The electric field distribution on the sample surface during corona ageing is simulated using COMSOL. The change in silicone rubber functional group is studied using Fourier transform infrared spectroscopy (FTIR) analysis. The influence of corona ageing time on the surface roughness recovery of silicone rubber nano alumina composites is studied using an atomic force microscope (AFM). The elemental distribution behavior and change in the emission spectra persistence time are analyzed during recovery period of corona-aged silicone rubber nanocomposites using Laser-Induced Breakdown Spectroscopy (LIBS) technique. The addition of alumina nanofiller to the silicone rubber improves the resistance to ageing due to corona discharge. Loss and recovery of hydrophobic property of silicone rubber due to corona aging were determined using static contact angle measurement. The results show a direct correlation between the contact angle and the surface roughness recovery characteristics. They indicate that the nanocomposite having a 5 wt% alumina content exhibits the highest resistance to corona discharge with least surface damage. Furthermore, fast recovery was observed in the first few hours after corona ageing, and most samples eventually regained their properties after about 8 hours of recovery time

Food falls in the deep northwestern Weddell Sea

When pelagic organisms die and fall onto the deep-sea floor they create food falls, parcels of organic enrichment that subsidize deep benthic scavenging communities. The diversity and quantities of food falls remains unstudied for many ocean regions, since they are stochastically deposited and rapidly scavenged. The Southern Ocean habitat supports large populations of megafauna but few food falls have been documented. To investigate the diversity and quantity of food falls in the northwestern Weddell Sea we analyzed 8476 deep-sea floor images that were captured during the expedition PS118 on RV Polarstern in 2019 by the camera system OFOBS (Ocean Floor Observation and Bathymetry System). OFOBS was towed 1.5 m above the seafloor along five transects (400 to 2200 m seafloor depth) east of the Antarctic Peninsula. We observed the carcasses of one baleen whale, one penguin, and four fish at depths of 647 m, 613 m, 647 m, 2136 m, 2165 m, and 2112 m, respectively, as well as associated scavenging fauna. To the best of our knowledge, we describe here the first in situ observations of deep-sea food falls for penguins and fish in the Southern Ocean. While the whale carcass seemed in an intermediate successional stage, both the penguin and the fish were likely recently deposited and three of the fish potentially resulted from fishery discards. Our relatively small data set suggests that a diverse array of food falls provide nutrients to the slopes of the Powell Basin