Description: Euphausiids constitute a major biomass component in shelf ecosystems and play a fundamental role in the rapid vertical transport of carbon from the ocean surface to the deeper layers during their daily vertical migration (DVM). DVM depth and migration patterns depend on oceanographic conditions with respect to temperature, light and oxygen availability at depth, factors that are highly dependent on season in most marine regions. Here we introduce a global krill respiration ANN (artificial neural network) model including the effect of latitude (LAT), the day of the year (DoY), and the number of daylight hours (DLh), in addition to the basal variables that determine ectothermal oxygen consumption (temperature, body mass and depth). The newly implemented parameters link space and time in terms of season and photoperiod to krill respiration. The ANN model showed a better fit (r2 = 0.780) when DLh and LAT were included, indicating a decrease in respiration with increasing LAT and decreasing DLh. We therefore propose DLh as a potential variable to consider when building physiological models for both hemispheres. For single Euphausiid species investigated in a large range of DLh and DoY, we also tested the standard respiration rate for seasonality with Multiple Linear Regression (MLR) and General Additive model (GAM). GAM successfully integrated DLh (r2 = 0.563) and DoY (r2 = 0.572) effects on respiration rates of the Antarctic krill, Euphausia superba, yielding the minimum metabolic activity in mid-June and the maximum at the end of December. We could not detect DLh or DoY effects in the North Pacific krill Euphausia pacifica, and our findings for the North Atlantic krill Meganyctiphanes norvegica remained inconclusive because of insufficient seasonal data coverage. We strongly encourage comparative respiration measurements of worldwide Euphausiid key species at different seasons to improve accuracy in ecosystem modeling.

Description: Euphausiids constitute a major biomass component in shelf ecosystems and play a fundamental role in the rapid vertical transport of carbon from the ocean surface to the deeper layers during their daily vertical migration (DVM). DVM depth and migration patterns depend on oceanographic conditions with respect to temperature, light and oxygen availability at depth, factors that are highly dependent on season in most marine regions. Here we introduce a global krill respiration ANN (Artificial Neural Network) model including the effect of latitude (LAT), the day of the year (DoY), and the number of daylight hours (DLh), in addition to the basal variables that determine ectothermal oxygen consumption (temperature, body mass and depth). The newly implemented parameters link space and time in terms of season and photoperiod to krill respiration. The ANN model showed a better fit (r2=0.780) when DLh and LAT were included, indicating a decrease in respiration with increasing LAT and decreasing DLh. We therefore propose DLh as a potential variable to consider when building physiological models for both hemispheres. For single Euphausiid species investigated in a large range of DLh and DoY, we also tested the standard respiration rate for seasonality with Multiple Linear Regression (MLR) and General Additive model (GAM). GAM successfully integrated DLh (r2= 0.563) and DoY (r2= 0.572) effects on respiration rates of the Antarctic krill, Euphausia superba, yielding the minimum metabolic activity in mid-June and the maximum at the end of December. We could not detect DLh or DoY effects in the North Pacific krill Euphausia pacifica, and our findings for the North Atlantic krill Meganyctiphanes norvegica remained inconclusive because of insufficient seasonal data coverage. We strongly encourage comparative respiration measurements of worldwide Euphausiid key species at different seasons to improve accuracy in ecosystem modelling.

Description: Molecular technologies are more frequently applied in Antarctic ecosystem research and the growing amount of sequence-based information available in databases adds a new dimension to understanding the response of Antarctic organisms and communities to environmental change. We apply molecular techniques, including fingerprinting, and amplicon and metagenome sequencing, to understand biodiversity and phylogeography to resolve adaptive processes in an Antarctic coastal ecosystem from microbial to macrobenthic organisms and communities. Interpretation of the molecular data is not only achieved by their combination with classical methods (pigment analyses or microscopy), but furthermore by combining molecular with environmental data (e.g., sediment characteristics, biogeochemistry or oceanography) in space and over time. The studies form part of a long-term ecosystem investigation in Potter Cove on King-George Island, Antarctica, in which we follow the effects of rapid retreat of the local glacier on the cove ecosystem. We formulate and encourage new approaches to integrate molecular tools into Antarctic ecosystem research, environmental conservation actions, and polar ocean observatories.

Description: Arctica islandica is known as the longest-lived non-colonial metazoan species on earth and is therefore increasingly being investigated as a new model in aging research. As the mitochondrial genome is associated with the process of aging in many species and bivalves are known to possess a peculiar mechanism of mitochondrial genome inheritance including doubly uniparental inheritance (DUI), we aimed to assess the genomic variability of the A. islandica mitochondrial DNA (mtDNA). We sequenced the complete mitochondrial genomes of A. islandica specimens from three different sites in the Western Palaearctic (Iceland, North Sea, Baltic Sea). We found the A. islandica mtDNA to fall within the normal size range (18 kb) and exhibit similar coding capacity as other animal mtDNAs. The concatenated protein sequences of all currently known Veneroidea mtDNAs were used to robustly place A. islandica in a phylogenetic framework. Analysis of the observed single nucleotide polymorphism (SNP) patterns on further specimen revealed two prevailing haplotypes. Populations in the Baltic and the North Sea are very homogenous, whereas the Icelandic population, from which exceptionally old individuals have been collected, is the most diverse one. Homogeneity in Baltic and North Sea populations point to either stronger environmental constraints or more recent colonization of the habitat. We also detected potential signs of recombination between these two haplotypes. Our analysis lays the foundation for further studies on A. islandica population structures, age research with this organism, and for phylogenetic studies. Accessions for the mitochondrial genome sequences: KC197241Iceland KF363951Baltic Sea KF363952North Sea

Description: Fish gills are target organs for waterborne metal ions and this work aimed to investigate the effects of waterborne Ni2+ (10, 25 and 50 mg L−1) on goldfish gills. A special focus was on the relationship between Ni uptake and the homeostasis of reactive oxygen species (ROS) in the gills, the tissue, in direct contact with the metal pollutant. Ni-accumulation in the gills occurred as a function of exposure concentrations (R2 = 0.98). The main indices of oxidative stress, namely carbonyl proteins (CP) and lipid peroxides (LOOH), decreased by 21-33% and 21-24%, as well as the activities of principal antioxidant enzymes superoxide dismutase and glutathione-dependent peroxidase, by 29-47% and 41-46%, respectively, in gills of Ni-exposed fish. One of the main players in the antioxidant defense of gills seems to be catalase, which increased by 23-53% in Ni-treated fish, and low molecular mass thiol-containing compounds (L-SH), exceeding untreated controls by 73-105% after fish exposure to 10-50 mg L−1 of Ni2+. The increased level of L-SH, mainly represented by reduced glutathione, was supported by enhanced activities of glutathione reductase (by 27-38%), glutathione-S-transferase (56-141%) and glucose-6-phosphate dehydrogenase (by 96-117%) and demonstrates the ability of the antioxidant system of gills to resist Ni-induced oxidative stress.

Description: The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and best-understood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better-define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a co-ordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future.

Description: A diesel spill occurring at Carlini Station (King-George Island, South Shetlands) in 2009 initiated investigations of the fate of the hydrocarbons and their effect on the bacterial communities of the Potter Cove ecosystem. Soils and sediments were sampled across the 200-meter long diesel plume towards Potter Cove four and 15 months after the spill. The sampling revealed a second fuel leakage from an underground pipeline at the spill site. The hydrocarbon fraction spilt over frozen and snow-covered ground, reached the sea, and dispersed with the currents. Contray diesel that infiltrated unfrozen soil remained detectable for years and was seeping with ground water towards coastal marine sediments. Structural changes of the bacterial communities as well as hydrocarbon, carbon and nitrogen contents were investigated in sediments in front of the station, two affected terrestrial sites, and a terrestrial non-contaminated reference site. Bacterial communities (16S rRNA gene clone libraries) changed over time in contaminated soils and sediments. At the underground seepage site of highest contamination (5812 to 366 µg g-1dw hydrocarbons from surface to 90-cm depth), communities were dominated by Actinobacteria (18%) and a betaproteobacterium closely related to Polaromonas napthalenivorans (40%). At one of the spill sites affected exclusively at the surface, contamination disappeared within one year. The same bacterial groups were enriched at both contaminated sites. This response at community level suggests that the cold-adapted indigenous microbiota in soils of the West Antarctic Peninsula have a high potential for bioremediation and can support soil cleaning actions in the ecosystem. Intensive monitoring of pollution and site assessment after episodic fuel spills is required for decision-making towards remediation strategies.

Description: The free radical nitric oxide (NO) is a powerful metabolic regulator in vertebrates and invertebrates. At cellular concentrations in the nanomolar range, and simultaneously reduced internal oxygen partial pressures (pO2), NO completely inhibits cytochrome-c-oxidase (CytOx) activity and hence mitochondrial- and whole-tissue respiration. The infaunal clam Arctica islandica regulates pO2 of hemolymph and mantle cavity water to mean values of 〈5 kPa, even in a completely oxygen-saturated environment of 21 kPa. These low internal pO2 values support a longer NO lifespan and NO accumulation in the body fluids and can thus trigger a depression of metabolic rate in the clams. Measurable amounts of NO formation were detected in hemocyte cells (~110 pmol NO 100−1 hemocytes h-1 at 6 kPa), which was not prevented in the presence of the NO synthase inhibitor L-NAME, and in the gill filaments of A. islandica. Adding a NO donor to intact gills and tissue homogenate significantly inhibited gill respiration and CytOx activity below 10 kPa. Meanwhile, the addition of the NO-oxidation product nitrite did not affect metabolic rates. The high nitrite levels found in the hemolymph of experimental mussels under anoxia do not indicate cellular NO production, but could be an indication of nitrate reduction by facultative anaerobic bacteria associated with tissue and/or hemolymph biofilms. Our results suggest that NO plays an important role in the initiation of metabolic depression during self-induced burrowing and shell closure of A. islandica. Furthermore, NO appears to reduce mitochondrial oxygen radical formation during surfacing and cellular reoxygenation after prolonged periods of hypoxia and anoxia.

Description: Iron stable isotope signatures (δ56Fe) in hemolymph (bivalve blood) of the Antarctic bivalve Laternula elliptica were analyzed by Multiple Collector - Inductively Coupled Plasma - Mass Spectrometry (MC-ICP-MS) to test whether the isotopic fingerprint can be tracked back to the predominant sources of the assimilated Fe. An earlier investigation of Fe concentrations in L. elliptica hemolymph suggested that an assimilation of reactive and bioavailable Fe (oxyhydr)oxide particles (i.e. ferrihydrite), precipitated from pore water Fe around the benthic boundary, is responsible for the high Fe concentration in L. elliptica (Poigner et al., 2013b). At two stations in Potter Cove (King George Island, Antarctica) bivalve hemolymph showed mean δ56Fe values of −1.19 ± 0.34‰ and -1.04 ± 0.39‰, respectively, which is between 0.5‰ and 0.85‰ lighter than the pool of easily reducible Fe (oxyhydr)oxides of the surface sediments (−0.3‰ to −0.6‰). This is in agreement with the enrichment of lighter Fe isotopes at higher trophic levels, resulting from the preferential assimilation of light isotopes from nutrition. Nevertheless, δ56Fe hemolymph values from both stations showed a high variability, ranging between −0.21‰ (value close to unaltered/primary Fe(oxyhydr)oxide minerals) and −1.91‰ (typical for pore water Fe or diagenetic Fe precipitates), which we interpret as a “mixed” δ56Fe signature caused by Fe assimilation from different sources with varying Fe contents and δ56Fe values. Furthermore, mass dependent Fe fractionation related to physiological processes within the bivalve cannot be ruled out. This is the first study addressing the potential of Fe isotopes for tracing back food sources of bivalves.