Description: The limpet Nacella concinna is a dominant macroinvertebrate along the coastal Antarctic Peninsula with two ecotypes inhabiting intertidal and subtidal areas, respectively. The ecological aim of the study was to understand whether higher stress competence and migratory energy expenses in intertidal Antarctic limpets shorten their lifetime and limit the shell growth rate compared to their sublittoral conspecific. We evaluated shell morphometry, age and internal shell growth bands in a large number of intertidal and subtidal N. concinna shells in Potter Cove, South Shetland Islands. Comparisons of their morphometrics showed that intertidal limpets are relatively shorter and less wide, and have higher shell mass, i.e. at common shell height, intertidal shells are relatively thicker and heavier than those of subtidal specimens. Internal shell growth bands showed alternating wide opaque (faster growth in summer) and thin translucent bands (slow growth in winter). The maximum age read was close to 20-years for both groups. Comparisons of von Bertalanffy growth curves showed for shell length and shell width lower growth rate k in intertidal animals than in subtidal ones associated to a great variability, with no differences in other growth constants. However, when shell height vs. age is considered, no differences were observed for any growth parameter. Curtailed variability of growth rates in the intertidal population reflects either a limitation of the food reserves or feeding time, or an energy gap for shell growth due to the costs for migratory movements and stress defense.

Description: Environmental factors can affect the rate of ageing and shape the lifespan in marine ectotherms. The mechanisms and the degree of - environmental influence on aging can best be studied in species with wide ranging biogeographic distribution. One of the biomarkers of physiological ageing is the fluorescent age pigment lipofuscin, which accumulates over lifetime in tissues of bivalves. We compared lipofuscin accumulation rate in muscles and respiratory tissues of the extremely long lived bivalve Arctica islandica from five geographically distinct populations (Northern Norway, White Sea, Kiel Bay, German Bight and Iceland). Maximum investigated chronological age across different populations in the present study differed from 40 years in Kiel Bay to 192 years at Iceland. An inverse association between lipofuscin deposition rate and recorded maximum age was observed through inter-population comparisons. In most cases lipofuscin accumulated exponentially over age in a tissue specific manner. The age specific lipofuscin content was significantly higher in respiratory than muscles tissues in all populations. Cellular lipofuscin granule area can be used as indicator of aging across A. islandica populations with the variance in granule accumulation depending on the annual variations of salinity in different marine regions, but not on the habitat specific thermal envelope.

Description: Glacial retreat and subglacial bedrock erosion are consequences of rapid regional warming on the West Antarctic peninsula. Sedimentation of fine grained eroded particles can impact the physiology of filter feeding benthic organisms. We investigated the effect of increasing concentrations of sediment on the oxygen consumption of suspension feeding species, the ascidians Molgula pedunculata, Cnemidocarpa verrucosa, Ascidia challengeri, and the pennatulid Malacobelemnon daytoni in Potter Cove (South Shetland Islands, Antarctica). In A. challengeri and C. verrucosa oxygen consumption increased gradually up to a critical sediment concentration (Ccrit) where species oxygen consumption was maximal (Omax in mg O2 g-1 dm d-1) and further addition of sediments decreased respiration. Ccrit was 200 mg L-1 for A. challengeri (Omax of 0.651 ± 0.238) and between 100 and 200 mg L-1 for C. verrucosa (Omax of 0.898 ± 0.582). Oxygen consumption of M. pedunculata increased significantly even at low sediment concentrations (15-50 mg sediment L-1). Contrary to the ascidians, sediment exposure did not affect oxygen consumption of the sea pen. The tiered response to sedimentation in the four species corroborates recent field observations that detected a reduction in abundance of the sensitive ascidian Molgula pedunculata from areas strongly affected by glacial sediment discharge, whereas sea pens are increasing in abundance. Our investigation relates consequences (population shifts in filter feeder communities) to causes (glacial retreat) and is of importance for modelling of climate change effects in Antarctic shallow coastal areas.

Description: Increasing temperatures and glacier-melting at the Western Antarctic Peninsula (WAP) are causing rapid changes in shallow coastal and shelf systems. Climate change related rising water temperatures, enhanced ice scouring as well as coastal sediment run-off in combination with changing feeding conditions and microbial community composition will affect all elements of the nearshore benthic ecosystem, a major component of which is the Antarctic soft shell clam Laternula elliptica. 454 RNA sequencing was carried out on tissues and hemocytes of L. elliptica, resulting in 42.525 contigs of which 48% were assigned putative functions. Changes in the expression of putative stress response genes were then investigated in hemocytes and siphon tissue of young and old animals subjected to starvation- and injury-experiments in order to investigate their response to sedimentation (food dilution, starvation) and iceberg scouring (injury). Analysis of antioxidant defense (Le-SOD, Le-catalase), wound repair (Le-TIMP, Le-chitinase), stress and immune response genes (Le-HSP70, Le-actin, Le-theromacin) revealed that most transcript were more clearly affected by injury rather than starvation. The up-regulation of these genes was particularly high in the hemocytes of young, fed individuals after acute injury. Only minor changes in expression were detected in young starved and old animals. The stress response of L. elliptica thus depends on the nature of the environmental cue and on age. This has consequences for future population predictions as the environmental changes at the WAP will differentially impact L. elliptica age classes and is bound to alter population structure.

Description: The Western Antarctic Peninsula is one of the most rapidly warming regions on earth. It is therefore important to analyze long-term trends and inter-annual patterns of change in major environmental parameters to understand the process underlying climate change in Western Antarctica. Since many polar long-term data series are fragmented and cannot be analysed with common time series analysis tools, we present statistical approaches that can deal with missing values. We applied U-statistics after Pettit and Buishand to detect abrupt changes, dynamic factor analysis to detect functional relationships, and additive modelling to detect patterns in time related to climatic cycles such as the Southern Annular Mode and El Niño Southern Oscillation in a long-term environmental data set from King George Island (WAP), covering 20 years. Our results not only reveal sudden changes for sea surface temperature and salinity, but also clear patterns in all investigated variables (sea surface temperature, salinity, suspended particulate matter and Chlorophyll a) that can directly be related to climatic cycles. Our results complement previous findings on climate related changes in the King George Island Region and provide insight into the environmental conditions and climatic drivers of system change in the study area. Hence, our statistical analyses may prove valuable for other polar environmental data sets and contribute to a better understanding of the regional variability of climate change and its impact on coastal systems.

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: Electron paramagnetic resonance (EPR) uses the resonant microwave radiation absorption of paramagnetic substances to detect highly reactive and, therefore, short-lived oxygen and nitrogen centered radicals. Previously, steady state concentrations of nitric oxide, ascorbyl radical (A•) and the labile iron pool (LIP) were determined in digestive gland of freshly collected animals from the North Sea bivalve Mya arenaria. From these data by By the application of a simple kinetic analysis based on elemental reactions to these data allowed us to estimate the steady state concentrations of superoxide anion, the rate of A• disappearance and the content of unsaturated lipids. This analysis applied to a marine invertebrate opens the possibility of a mechanistic understanding of the complexity of free radical and LIP interactions in a metabolically slow, cold water organism under unstressed conditions. This data can be further used as a basis to assess the cellular response to stress in a simple system as the bivalve M. arenaria that can then be compared to cells of higher organisms.

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.