Alfred Wegener Institute for Polar and Marine Research
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Evolutionary Adaptation of Protein Turnover in White Muscle of Stenothermal Antarctic Fish: Elevated Cold Compensation at Reduced Thermal Responsiveness
Get PDFProtein turnover is highly energy consuming and overall relates to an organism’s growth performance varying largely between species, e.g., due to pre-adaptation to environmental characteristics such as temperature. Here, we determined protein synthesis rates and capacity of protein degradation in white muscle of the cold stenothermal Antarctic eelpout (Pachycara brachycephalum) and its closely related temperate counterpart, the eurythermal common eelpout (Zoarces viviparus). Both species were exposed to acute warming (P. brachycephalum, 0 °C + 2 °C day−1; Z. viviparus, 4 °C + 3 °C day−1). The in vivo protein synthesis rate (Ks) was monitored after injection of 13C-phenylalanine, and protein degradation capacity was quantified by measuring the activity of cathepsin D in vitro. Untargeted metabolic profiling by nuclear magnetic resonance (NMR) spectroscopy was used to identify the metabolic processes involved. Independent of temperature, the protein synthesis rate was higher in P. brachycephalum (Ks = 0.38–0.614 % day−1) than in Z. viviparus (Ks= 0.148–0.379% day−1). Whereas protein synthesis remained unaffected by temperature in the Antarctic species, protein synthesis in Z. viviparus increased to near the thermal optimum (16 °C) and tended to fall at higher temperatures. Most strikingly, capacities for protein degradation were about ten times higher in the Antarctic compared to the temperate species. These differences are mirrored in the metabolic profiles, with significantly higher levels of complex and essential amino acids in the free cytosolic pool of the Antarctic congener. Together, the results clearly indicate a highly cold-compensated protein turnover in the Antarctic eelpout compared to its temperate confamilial. Constant versus variable environments are mirrored in rigid versus plastic functional responses of the protein synthesis machinery
Review article: A European perspective on wind and storm damage – from the meteorological background to index-based approaches to assess impacts
Get PDFWind and windstorms cause severe damage to natural and human-made environments. Thus, wind-related risk assessment is vital for the preparation and mitigation of calamities. However, the cascade of events leading to damage depends on many factors that are environment-specific and the available methods to address wind-related damage often require sophisticated analysis and specialization. Fortunately, simple indices and thresholds are as effective as complex mechanistic models for many applications. Nonetheless, the multitude of indices and thresholds available requires a careful selection process according to the target sector. Here, we first provide a basic background on wind and storm formation and characteristics, followed by a comprehensive collection of both indices and thresholds that can be used to predict the occurrence and magnitude of wind and storm damage. We focused on five key sectors: forests, urban areas, transport, agriculture and wind-based energy production. For each sector we described indices and thresholds relating to physical properties such as topography and land cover but also to economic aspects (e.g. disruptions in transportation or energy production). In the face of increased climatic variability, the promotion of more effective analysis of wind and storm damage could reduce the impact on society and the environment
Drivers of change in Arctic fjord socio-ecological systems: Examples from the European Arctic
Get PDFFjord systems are transition zones between land and sea, resulting in complex and dynamic
environments. They are of particular interest in theArctic as they harbour ecosystems inhabited by
a rich range of species and provide many societal benefits. The key drivers of change in the
European Arctic (i.e., Greenland, Svalbard, and Northern Norway) fjord socio-ecological systems
are reviewed here, structured into five categories: cryosphere (sea ice, glacier mass balance, and
glacial and riverine discharge), physics (seawater temperature, salinity, and light), chemistry
(carbonate system, nutrients), biology (primary production, biomass, and species richness), and
social (governance, tourism, and fisheries). The data available for the past and present state of these
drivers, aswell as futuremodel projections, are analysed in a companion paper. Changes to the two
drivers at the base of most interactions within fjords, seawater temperature and glacier mass
balance, will have the most significant and profound consequences on the future of European
Arctic fjords. This is because even though governance may be effective at mitigating/adapting to
local disruptions caused by the changing climate, there is possibly nothing that can be done to halt
the melting of glaciers, the warming of fjord waters, and all of the downstream consequences that
these two changes will have. This review provides the first transdisciplinary synthesis of the
interactions between the drivers of changewithinArctic fjord socio-ecological systems.Knowledge
of what these drivers of change are, and how they interact with one another, should provide more
expedient focus for future research on the needs of adapting to the changing Arctic
Evolution of the microstructure and reflectance of the surface scattering layer on melting, level Arctic sea ice
Get PDFThe microstructure of the uppermost portions of a melting Arctic sea ice cover has a disproportionately large
influence on how incident sunlight is reflected and absorbed in the ice/ocean system. The surface scattering
layer (SSL) effectively backscatters solar radiation and keeps the surface albedo of melting ice relatively high
compared to ice with the SSL manually removed. Measurements of albedo provide information on how incoming
shortwave radiation is partitioned by the SSL and have been pivotal to improving climate model
parameterizations. However, the relationship between the physical and optical properties of the SSL is still
poorly constrained. Until now, radiative transfer models have been the only way to infer the microstructure of
the SSL. During the MOSAiC expedition of 2019–2020, we took samples and, for the first time, directly
measured the microstructure of the SSL on bare sea ice using X-ray micro-computed tomography. We show
that the SSL has a highly anisotropic, coarse, and porous structure, with a small optical diameter and density
at the surface, increasing with depth. As the melting surface ablates, the SSL regenerates, maintaining some
aspects of its microstructure throughout the melt season. We used the microstructure measurements with
a radiative transfer model to improve our understanding of the relationship between physical properties and
optical properties at 850 nm wavelength. When the microstructure is used as model input, we see a 10–15%
overestimation of the reflectance at 850 nm.This comparison suggests that either a) spatial variability at the
meter scale is important for the two in situ optical measurements and therefore a larger sample size is needed
to represent the microstructure or b) future work should investigate either i) using a ray-tracing approach
instead of explicitly solving the radiative transfer equation or ii) using a more appropriate radiative transfer
model
(258–260) Proposals to eliminate contradiction between Articles 11.7 and 11.8 and to equate non‐fossil with fossil names of dinophytes for purposes of priority
No full textUpper-ocean temperature characteristics in the subantarctic southeastern Pacific based on biomarker reconstructions
Get PDFAs remnants of living organisms, alkenones and isoprenoid glycerol dialkyl glycerol tetraether lipids (isoGDGTs) are widely used biomarkers for determining ocean water temperatures from the past. The organisms that these proxy carriers stem from are influenced by a number of environmental parameters, such as water depth, nutrient availability, light conditions, or seasonality, which all may significantly bias the calibration to ambient water temperatures. Reliable temperature determinations thus remain challenging, especially in higher latitudes and for undersampled regions. We analyzed 33 sediment surface samples from the southern Chilean continental margin and the Drake Passage for alkenones and isoGDGTs and compared the results with gridded instrumental reference data from the World Ocean Atlas 2005 (WOA05) and previously published data from an extended study area covering the central and western South Pacific towards the Aotearoa / New Zealand continental margin. We show that for alkenone-derived sea surface temperatures (SSTs), the widely used global core-top calibration of Müller et al. (1998) yields the smallest deviation of the WOA05-based SSTs. On the contrary, the calibration of Sikes et al. (1997), determined for higher latitudes and summer SSTs, overestimates modern WOA05-based SSTs in both the annual mean and summer. Our alkenone SSTs show a slight seasonal shift of ∼ 1 °C at the southern Chilean margin and up to ∼ 2 °C in the Drake Passage towards austral summer SSTs. Samples in the central South Pacific, on the other hand, reflect an annual mean signal. We show that for isoGDGT-based temperatures, the subsurface calibration of Kim et al. (2012a) best reflects temperatures from the WOA05 in areas north of the Subantarctic Front (SAF). Temperatures south of the SAF are, in contrast, significantly overestimated by up to 14 °C, irrespective of the applied calibration. In addition, we used the GDGT [2]/[3] ratios, which give an indication of the production depth of the isoGDGTs and/or potential influences from land. Our samples reflect a subsurface (0-200 m water depth) rather than a surface (0-50 m water depth) signal in the entire study area and show a correlation with the monthly dust distribution in the South Pacific, indicating terrigenous influences. The overestimation of isoGDGT surface and subsurface temperatures south of the SAF highlights the need for a reassessment of existing calibrations in the polar Southern Ocean. Therefore, we suggest a modified Southern Ocean tetraether index (TEX86)-based calibration for surface and subsurface temperatures, which shows a lower temperature sensitivity and yields principally lower absolute temperatures, which align more closely with WOA05-derived values and also OH-isoGDGT-derived temperatures
Strong host phylogenetic and ecological effects on host competency for avian influenza in Australian wild birds
Get PDFHost susceptibility to parasites is mediated by intrinsic and external factors such as genetics, ecology, age and season. While waterfowl are considered central to the reservoir community for low pathogenic avian influenza A viruses (LPAIV), the role of host phylogeny has received limited formal attention. Herein, we analysed 12 339 oropharyngeal and cloacal swabs and 10 826 serum samples collected over 11 years from wild birds in Australia. As well as describing age and species-level differences in prevalence and seroprevalence, we reveal that host phylogeny is a key driver in host range. Seasonality effects appear less pronounced than in the Northern Hemisphere, while annual variations are potentially linked to El Niño-Southern Oscillation. Our study provides a uniquely detailed insight into the evolutionary ecology of LPAIV in its avian reservoir community, defining distinctive processes on the continent of Australia and expanding our understanding of LPAIV globally
Miles down for lunch: deep-sea in-situ observations of Arctic finned octopods Cirroteuthis muelleri suggest pelagic–benthic feeding migration
Get PDFDeep-sea cephalopods are diverse, abundant, and poorly understood. The Cirrata are gelatinous finned octopods and among the deepest-living cephalopods ever recorded. Their natural feeding behaviour remains undocumented. During deep-sea surveys in the Arctic, we observed Cirroteuthis muelleri. Octopods were encountered with their web spread wide, motionless and drifting in the water column 500–2600 m from the seafloor. Individuals of C. muelleri were also repeatedly observed on the seafloor where they exhibited a repeated, behavioural sequence interpreted as feeding. The sequence (11–21 s) consisted of arm web spreading, enveloping and retreating. Prey capture happened during the enveloping phase and lasted 5–49 s. Numerous traces of feeding activity were also observed on the seafloor. The utilization of the water column for drifting and the deep seafloor for feeding is a novel migration behaviour for cephalopods, but known from gelatinous fishes and holothurians. By benthic feeding, the octopods benefit from the enhanced nutrient availability on the seafloor. Drifting in the water column may be an energetically efficient way of transportation while simultaneously avoiding seafloor-associated predators. In-situ observations are indispensable to discover the behaviour of abundant megafauna, and the energetic coupling between the pelagic and benthic deep sea
An evaluation of long-term physical and hydrochemical measurements at the Sylt Roads Marine Observatory (1973–2019), Wadden Sea, North Sea
Get PDFThe Sylt Roads pelagic time series covers physical and hydrochemical parameters at five neighboring stations in the Sylt-Rømø bight, Wadden Sea, North Sea. Since the beginning of the time series in 1973, sea surface temperature (SST), salinity, ammonium, nitrite, nitrate, and soluble reactive phosphorus (SRP) have been measured twice a week. The other parameters were introduced later (dissolved silicate (Si) since 1974, pH since 1979, dissolved organic nitrogen (DON) since 1996, dissolved organic phosphorus (DOP) since 2001, chlorophyll a since 1979, and suspended particulate matter (SPM) since 1975), and in the case of dissolved oxygen, were already discontinued (1979-1983). In the years 1977, 1978, and 1983, no sampling took place. Since the start of the continuous sampling in 1984, the sea surface temperature in the bight has risen by +1.11gC, with the highest increases during the autumn months, while the pH and salinity decreased by 0.23 and 0.33 units, respectively. Summer and autumn salinities are generally significantly elevated compared to spring and winter conditions. Dissolved nutrients (ammonium, nitrite, nitrate, and SRP) have displayed periods of intense eutrophication (1973-1998) and de-eutrophication since 1999. Silicate has shown significantly higher winter levels since 1999. Interestingly, phytoplankton parameters did not mirror these large changes in nutrient concentrations, as a seasonal comparison of the two eutrophication periods showed no significant differences with regard to chlorophyll a. This phenomenon might be triggered by an important switch in nutrient limitation during the time series. With regard to nutrients, the phytoplankton was probably primarily limited by silicate until 1998, while, since 1999, the SRP limitation has become increasingly important. All data are available in Rick et al. (2017b-e, 2020a-o) from 10.1594/PANGAEA.150032, 10.1594/PANGAEA.873549, 10.1594/PANGAEA.873545, 10.1594/PANGAEA.873547, 10.1594/PANGAEA.918018, 10.1594/PANGAEA.918032, 10.1594/PANGAEA.918027, 10.1594/PANGAEA.918023, 10.1594/PANGAEA.918033, 10.1594/PANGAEA.918028, 10.1594/PANGAEA.918024, 10.1594/PANGAEA.918034, 10.1594/PANGAEA.918029, 10.1594/PANGAEA.918025, 10.1594/PANGAEA.918035, 10.1594/PANGAEA.918030, 10.1594/PANGAEA.918026, 10.1594/PANGAEA.918036, and 10.1594/PANGAEA.918031
Species-specific responses of marine bacteria to environmental perturbation
Get PDFAbstract
Environmental perturbations shape the structure and function of microbial communities. Oil spills are a major perturbation and resolving spills often requires active measures like dispersant application that can exacerbate the initial disturbance. Species-specific responses of microorganisms to oil and dispersant exposure during such perturbations remain largely unknown. We merged metatranscriptomic libraries with pangenomes to generate Core-Accessory Metatranscriptomes (CA-Metatranscriptomes) for two microbial hydrocarbon degraders that played important roles in the aftermath of the Deepwater Horizon oil spill. The Colwellia CA-Metatranscriptome illustrated pronounced dispersant-driven acceleration of core (~41%) and accessory gene (~59%) transcription, suggesting an opportunistic strategy. Marinobacter responded to oil exposure by expressing mainly accessory genes (~93%), suggesting an effective hydrocarbon-degrading lifestyle. The CA-Metatranscriptome approach offers a robust way to identify the underlying mechanisms of key microbial functions and highlights differences of specialist-vs-opportunistic responses to environmental disturbance.</jats:p