Abstract: The potential for biological colonization of Antarctic shores is an increasingly important topic in the context of anthropogenic warming. Successful Antarctic invasions to date have been recorded exclusively from terrestrial habitats. While non-native marine species such as crabs, mussels and tunicates have already been reported from Antarctic coasts, none have as yet established there. Among the potential marine invaders of Antarctic shallow waters is Halicarcinus planatus (Fabricius, 1775), a crab with a circum-Subantarctic distribution and substantial larval dispersal capacity. An ovigerous female of this species was found in shallow waters of Deception Island, South Shetland Islands in 2010. A combination of physiological experiments and ecological modelling was used to assess the potential niche of H. planatus and estimate its future southward boundaries under climate change scenarios. We show that H. planatus has a minimum thermal limit of 1°C, and that its current distribution (assessed by sampling and niche modelling) is physiologically restricted to the Subantarctic region. While this species is presently unable to survive in Antarctica, future warming under both ‘strong mitigation’ and ‘no mitigation’ greenhouse gas emission scenarios will favour its niche expansion to the Western Antarctic Peninsula (WAP) by 2100. Future human activity also has potential to increase the probability of anthropogenic translocation of this species into Antarctic ecosystems.

Abstract: Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current transports properties across ocean basins through both advection and mixing. Recent tracking studies have indicated the existence of two large-scale, open ocean habitats in the Southern Ocean used by grey petrels (Procellaria cinerea) from two populations (i.e., Kerguelen and Antipodes islands) during their nonbreeding season for extended periods during austral summer (i.e., October to February). In this work, we use a novel combination of large-scale oceanographic observations, surface drifter data, satellite-derived primary productivity, numerical adjoint sensitivity experiments, and output from a biogeochemical state estimate to examine local and remote influences on these grey petrel habitats. Our aim is to understand the oceanographic features that control these isolated foraging areas and to evaluate their ecological value as oligotrophic open ocean habitats. We estimate the minimum local primary productivity required to support these populations to be much <1% of the estimated local primary productivity. The region in the southeast Indian Ocean used by the birds from Kerguelen is connected by circulation to the productive Kerguelen shelf. In contrast, the region in the south-central Pacific Ocean used by seabirds from the Antipodes is relatively isolated suggesting it is more influenced by local factors or the cumulative effects of many seasonal cycles. This work exemplifies the potential use of predator distributions and oceanographic data to highlight areas of the open ocean that may be more dynamic and productive than previously thought. Our results highlight the need to consider advective connections between ecosystems in the Southern Ocean and to re-evaluate the ecological relevance of oligotrophic Southern Ocean regions from a conservation perspective.

Abstract: Fishers aim to optimise cost–benefit ratios of their behaviour when exploiting resources. Avoidance of interactions with marine predators (i.e. their feeding on catches in fishing gear, known as depredation) has recently become an important component of their decisions. How fishers minimise these interactions whilst maximising fishing success is poorly understood. This issue is addressed in a sub-Antarctic, long-line fishery confronted with extensive depredation by sperm whales Physeter macrocephalus and killer whales Orcinus orca by examining a 15-year data set. Whereas a broad range of behaviours was identified from spatio-temporal and operational descriptors, none combined high fishing success with low frequency of interactions. With experience, fishers favoured exploitation of productive patches with high frequencies of interactions over avoidance behaviours. Such decisions, although potentially optimal in the short term, are likely to intensify pressures on fish stocks and impact depredating whales. Therefore, the present study provides additional evidence to inform management decisions pertaining to the coexistence between fisheries and marine predators.

Abstract: The role of deposition fluxes on the mercury cycle at Concordia station, on the high Antarctic plateau have been investigated over the Austral summer between December 2017 to January 2018. Wet/frozen deposition was collected daily from specially sited tables, simultaneously with the collection of surface (0–3 cm) and subsurface (3–6 cm) snow and the analysis of Hg0 in the ambient air. Over the course of the experiment the atmospheric Hg0 concentrations ranged from 0.58 ± 0.19 to 1.00 ± 0.33 ng m−3, surface snow Hg concentrations varied between (0–3 cm) 0.006 ± 0.003 to 0.001 ± 0.001 ng cm−3 and subsurface snow (3–6 cm) concentrations varied between 0.001 ± 0.001 to 0.003 ± 0.002 ng cm−3. The maximum daily wet deposition flux was found to be 23 ng m−2 d−1. Despite the low temporal resolution of our measurements combined with their potential errors, the linear regression of the Hg deposition fluxes against the snow accumulation rates allowed us to estimate the mean dry deposition rate from the intercept of the graph as −0.005 +- 0.008 ng m−2 d−1. From this analysis, we conclude that wet deposition accounts for the vast majority of the Hg deposition fluxes at Concordia Station. The number of snow events, together with the continuous GEM measurements have allowed us to make a first estimation of the mean snow scavenging factor at Dome C. Using the slope of the regression of mercury flux on snow accumulation we obtained a snow scavenging factor that ranges from 0.21 to 0.22 ± 0.02 (ngHg/g snow)/(ngHg/m3 air). Our data indicate that the boundary layer height and local meteorological effects influence Hg0 reemission from the top of (0–3 cm) the snowpack into the atmosphere and into the deeper snowpack layer (3–6 cm). These data will help constrain numerical models on the behaviour of mercury in Antarctica.

Abstract: The ever-increasing number of introduced species profoundly threatens global biodiversity. While the ecological and evolutionary consequences of invasive alien species are receiving increasing attention, their economic impacts have largely remained understudied, especially in France. Here, we aimed at providing a general overview of the monetary losses (damages caused by) and expenditures (management of) associated with invasive alien species in France. This country has a long history of alien species presence, partly due to its long-standing global trade activities, highly developed tourism, and presence of overseas territories in different regions of the globe, resulting in a conservative minimum of 2,750 introduced and invasive alien species. By synthesizing for the first time the monetary losses and expenditures incurred by invasive alien species in Metropolitan France and French overseas territories, we obtained 1,583 cost records for 98 invasive alien species. We found that they caused a conservative total amount ranging between US$ 1,280 million and 11,535 million in costs over the period 1993–2018. We extrapolated costs for species invading France, for which costs were reported in other countries but not in France, which yielded an additional cost ranging from US$ 151 to 3,030 millions. Damage costs were nearly eight times higher than management expenditure. Insects, and in particular the Asian tiger mosquito Aedes albopictus and the yellow fever mosquito Ae. aegypti, totalled very high economic costs, followed by non-graminoid terrestrial flowering and aquatic plants (Ambrosia artemisiifolia, Ludwigia sp. and Lagarosiphon major). Over 90% of alien species currently recorded in France had no costs reported in the literature, resulting in high biases in taxonomic, regional and activity sector coverages. To conclude, we report alarming costs and even more alarming knowledge gaps. Our results should raise awareness of the importance of biosecurity and biosurveillance in France, and beyond, as well as the crucial need for better reporting and documentation of cost data.