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: Respiration rate of meiofauna is difficult to measure, and the response to variations in the environmental oxygen concentrations has so far been mainly addressed through behavioral investigation. We investigated the effect of different oxygen concentrations on the physiology of the marine platyhelminth Macrostomum lignano. Respiration was measured using batches of 20 animals in a glass microtiter plate equipped with optical oxygen sensor spots. At higher oxygen saturations (〉60%), animals showed a clear oxyconforming behavior. However, below this values, the flatworms kept respiration rates constant at 0.064 ± 0.001 nmol O2•l-1•h-1•ind-1 down to 3 kPa po2, evidencing a highly developed metabolic regulating capacity. Physiological changes related to tissue oxygenation were assessed using live imaging techniques with different fluorophores in animals maintained in normoxic (21 kPa), hyperoxic (40 kPa), near anoxic (≈0 kPa) conditions and subjected to anoxia/re-oxygenation. Ageladine-A and BCECF both indicated that pHi under near anoxia increases by about 0.07 to 0.10 units. Mitochondrial membrane potential, Δψm, was less polarized higher in anoxic and hyperoxic compared to normoxic conditions (JC1). Staining with ROS sensitive dyes, DHE for detection of superoxide anion (O2•-) formation and C-H2DFFDA for other ROS species aside from O2•- (H2O2, HOO• and ONOO-)for H2O2 formation, both showed increased ROS formation following anoxia reoxygenation treatment. Animals exposed to hyperoxic, normoxic and anoxic treatments displayed no significant differences in superoxide O2•- formation, whereas mitochondrial H2O2 ROS formation (as detected by C-H2DFFDA) was higher after hyperoxic exposure and lowest under near anoxia compared to the normoxic control group. M. lignano seems to be a species tolerant to a wide range of oxygen concentrations (being able to maintain aerobic metabolism from extremely low po2 and up to hyperoxic conditions) which is an essential prerequisite for successfully dealing with the drastic environmental oxygen variations that occur within intertidal sediments.

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.