Description: Seasonal variations in primary production (PP) in the Kara Sea are underresearched. Previous studies only collected data during autumn or in late summer. However, the middle of summer is close to the beginning of the growing season, when PP can contribute significantly to annual water column integrated primary production (IPP). In addition, differences can be expected in the spatial and vertical distribution of phytoplankton communities in this period. This gap in midsummer data was addressed within the framework of a multidisciplinary research cruise by the R/V “Akademik Mstislav Keldysh” (from 15 July to 18 August 2016). High values of IPP (〉 200 mgC m −2  day −1 ) and surface chlorophyll a (Chl  a ) concentration (Chl 0  〉 1 mg m −3 ) were associated with the Ob–Yenisey river plume, located in the central part of the Kara Sea. Beyond the influence of the plume, in the western and southwestern regions of the Kara Sea, well-pronounced subsurface chlorophyll maxima (SCM) were observed. In some cases, the Chl  a concentration in SCM exceeded Chl 0 by two orders of magnitude. SCM were often accompanied by subsurface PP maxima (SPM). At stations where SCM was pronounced, IPP values reached 500–800 mgC m −2  day −1 , and 〉 30 % of IPP was accounted for by SPM-integrated PP. Thus, in the middle of summer in the Kara Sea, IPP was linked with the chlorophyll-specific phytoplankton biomass and depended on the strength of the SCM.

Description: The Southern Ocean is a very sensitive ecosystem, with the Antarctic Peninsula being one of the most rapidly warming regions on Earth. Accordingly, studies of its biodiversity are of urgent interest. In this context, taxonomical surveys of Antarctic tanaidacean species become relevant, since it is one of the lesser-known Antarctic macrofaunal groups. The present study aims to elucidate the species composition as well as spatial and vertical distribution of tanaidaceans in the shallow sublittoral zone of Admiralty Bay, one of the Antarctic Specially Managed Areas. Sediment samples were taken in the years 2005 and 2010 from 20 and 50 m depth zones at two sites in each of five chosen stations. Three replicate box-corer samples were taken at each site, and the retained sediment was stratified (0–2, 2–6, and 6–10 cm sediment layers). Nine Tanaidacean species (superfamily Paratanaoidea) were identified, with two new species records for Admiralty Bay: Arhaphuroides parabreviremis and Parakanthophoreus antarcticus . In general, Nototanais antarcticus was the dominant species. Significant abundance differences were found among stations, except at 20 m depth in 2005. The Ullmann Point station stood out by the absence of tanaidaceans. No significant differences were found between depths, although 20 m depth sites exhibited higher abundance than 50 m depth ones, which in turn presented higher species richness. Tanaidaceans were concentrated in the first six cm of sediment. Data suggest that the Tanaidacea assemblages in Admiralty Bay have very heterogeneous spatial distribution, reflecting the variety of habitats present in this region.

Description: Marine bivalves are well known for their impressive lifespans. Like trees, bivalves grow by accretion and record age and size throughout ontogeny in their shell. Bivalves, however, can form growth increments at several different periodicities depending on their local environment. Thus, establishing lifespans and growth rates of marine bivalves requires a proper identification of annual growth increments. Here, we use isotope sclerochronology to decipher the accretionary growth record of modern Astarte borealis from the White Sea, Russia (N 67°05.70′; E 32°40.85′). Unlike winter growth increments observed in many other cold-temperate and boreal bivalve and limpet species, prominent growth increments in A. borealis corresponded to the most negative values in the oxygen isotope (δ 18 O) time series indicating that they formed during summer. Furthermore, summer growth increments do not coincide with the external concentric ridges on the shell making the latter feature an unreliable indicator of age. Similar to many other polar bivalves, A. borealis shows slow growth and long life. The von Bertalanffy growth equation for our sample is H t  = 29.39*(1 −  e (− 0.11( t −(− 1.86)) ). Lifespans of individuals examined here ( n  = 18) range from 16 to 48 years. Given its impressive longevity and widespread polar distribution, A. borealis may be a potentially valuable skeletal archive for monitoring environmental conditions in the Arctic Ocean and boreal seas in the face of changing climate.

Description: Persistent organic pollutant (POP) contamination of Polar Regions continues to present a major ecological challenge and an environmental stressor to local biota. Antarctic krill (Euphausia superba) are a keystone species of the Antarctic sea ice ecosystem. Krill have repeatedly been found to accumulate a diverse array of POPs and thereby serve as vectors of these to the remainder of the Antarctic food web. p , p ′-Dichlorodiphenyldichloroethylene ( p , p ′-DDE) is a dominant POP compound accumulating in Antarctic krill and higher trophic level predators. Recently, p , p ′-DDE uptake dynamics, associated behavioural and developmental toxicity were evaluated in this species. The present study investigated the response of enzymes with known roles in detoxification (glutathione S -transferase, GST and cytochrome P450 2B, CYP2B), neurotoxicity (acetylcholinesterase, AChE) and oxidative stress (glutathione peroxidase GPx) in Antarctic krill exposed to p , p ′-DDE. CYP2B was not detectable in Antarctic krill. No strong concentration responses resulted from the exposure to p , p ′-DDE. These findings do not provide evidence for an activated detoxification response to this compound via the tested biochemical pathways in Antarctic krill. This is the first time that GST, AChE and GPx have been characterised in this species following pollutant exposure. Further research with additional pollutants and compound mixtures is necessary to assess the practical role of these enzymes as biomarkers of pollutant exposure in Antarctic krill. These first exploratory findings present a valuable contribution to a critical knowledge gap in polar ecotoxicology, namely the comparative sensitivity of polar organisms relative to temperate and tropical counterparts.

Description: The Arctic Ocean is a region particularly prone to ongoing ocean acidification (OA) and climate-driven changes. The influence of these changes on Arctic phytoplankton assemblages, however, remains poorly understood. In order to understand how OA and enhanced irradiances (e.g., resulting from sea–ice retreat) will alter the species composition, primary production, and eco-physiology of Arctic phytoplankton, we conducted an incubation experiment with an assemblage from Baffin Bay (71°N, 68°W) under different carbonate chemistry and irradiance regimes. Seawater was collected from just below the deep Chl a maximum, and the resident phytoplankton were exposed to 380 and 1000 µatm pCO 2 at both 15 and 35% incident irradiance. On-deck incubations, in which temperatures were 6 °C above in situ conditions, were monitored for phytoplankton growth, biomass stoichiometry, net primary production, photo-physiology, and taxonomic composition. During the 8-day experiment, taxonomic diversity decreased and the diatom Chaetoceros socialis became increasingly dominant irrespective of light or CO 2 levels. We found no statistically significant effects from either higher CO 2 or light on physiological properties of phytoplankton during the experiment. We did, however, observe an initial 2-day stress response in all treatments, and slight photo-physiological responses to higher CO 2 and light during the first five days of the incubation. Our results thus indicate high resistance of Arctic phytoplankton to OA and enhanced irradiance levels, challenging the commonly predicted stimulatory effects of enhanced CO 2 and light availability for primary production.

Description: Soil microbes play important roles in global carbon and nutrient cycling. Soil microfungi are generally amongst the most important contributors. They produce various extracellular hydrolase enzymes that break down the complex organic molecules in the soil into simpler form. In this study, we investigated patterns of amylase and cellulase (which are responsible for breaking down starch and cellulose, respectively) relative activity (RA) on solid media at different culture temperatures in fungal strains from Arctic, Antarctic and tropical soils. Fungal isolates from all three regions were inoculated onto R2A media supplemented with starch for amylase and carboxymethylcellulose and trypan blue for cellulase screening. The isolates were then incubated at 4, 10, 15, 20, 25, 30, 35 and 40 °C and examined for activity after 5 and 10 days, for tropical and polar isolates, respectively. The data obtained indicate that the polar fungal strains exhibited similar patterns of amylase and cellulase RA. Both Arctic and Antarctic fungi showed highest RA for amylase and cellulase at 35 °C, while colony growth was maximised at 15 °C. Colony growth and RA of the polar isolates were negatively correlated suggesting that, as temperatures increase, the cells become stressed and have fewer resources available to invest in growth. Unlike polar isolates, tropical isolates did not exhibit any trend of colony growth with temperature, rather having idiosyncratic patterns in each isolate. The low enzyme production and RA levels in the tropical strains may suggest both a low ability to respond to temperature variation in their natural thermally stable tropical habitats, as well as a level of thermal stress limiting their enzyme production ability.

Description: Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill ( Euphausia superba ), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

Description: Sedimentary organic matter (OM) represents the energy supply for the shelf benthos at the Antarctic Ocean, and has yet to be properly characterized in terms of sources and composition for the Potter Cove region, King George/25 de Mayo Island. This energy input occurs mainly during the brief summer and provides the majority of available energy for the year, in a region with high endemism and limited source variety of sedimentary OM. Thus, the aim of this study is to identify the OM origin and degradation degree based on the spatial distribution and type of organic biomarkers. Twelve surficial sediment samples were collected and analyzed for the presence of n -alkanols and sterols. The different spatial patterns between the analyzed compounds indicated distinct OM sources and degradation degrees. First, relatively fresh phytoplankton organic matter and an enhanced bacterial activity were associated with the occurrence of seaweeds detritus and represent the source of n -alkanols. Second, relatively fresh material mainly associated with seaweeds debris were identified as the source of macroalgae sterols. Our results shed some light into the base of the Potter Cove trophic benthic chain and increase our understanding on the region’s biogeochemical processes relating to OM recycling. It also provides a baseline for assessing future changes in the structure of the benthic food web in this environment, which is subject to noticeable glaciers retreat.

Description: Invasive species present a risk to Antarctic ecosystems by altering community structure and function. Reports of non-native invertebrates are increasing at Antarctic sites subject to tourism industry and national operator activity. Furthermore, dispersal of existing non-native species to other Antarctic sites may greatly expand their distributions and increase the spatial scale of potential impacts. Consequently, non-native species occurring near logistical hubs present an enhanced risk. The non-native Collembolon, Hypogastrura viatica , was introduced to Léonie Island, Ryder Bay, near the logistical hub of Rothera Research Station, Rothera Point, Adelaide Island, at some point before 1993, but no attempt had been made to assess the extent of its distribution in the local area. In this study, we surveyed the regularly frequented islands of Ryder Bay and Rothera Point to attempt to assess the continued presence and distribution of this species. Hypogastrura viatica was not identified amongst the 36,796 Collembola specimens extracted from 138 samples taken from the islands and Rothera Point. With no evidence of the continued presence of this non-native Collembolon in the local area, either H. viatica has become extinct or has such a restricted spatial distribution that our monitoring programme failed to detect it. In light of these results, existing local biosecurity measures will be maintained as a precautionary measure to reduce the risk of further anthropogenic dispersal of this potentially invasive Collembolon as well as of any other species imported unintentionally in future.