Alfred Wegener Institute for Polar and Marine Research
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Simulating Plankton – getting it right in the era of Digital Twins of The Ocean; building and challenging perceptions
Get PDFAir-born investigation of Sediment-rIch Glacial Meltwater plumes and sediment delivery from the shoreline of recently deglaciated coasts at Maxwell Bay, King Georg Island, Antarctica (SIGMA-I)
Get PDFThe campaign ANT-Land-SIGMA-I (12/2022 – 03/2023) focused on the marine/terrestrial transition zone at Westantarctic Peninsula (WAP) coasts and to gain detailed insides in the distribution and character of habitats influenced by sediment-loaded meltwater runoff in front of 7 glaciers at King George Island. From the Antarctic scientific stations Carlini, Escudero and Arctowski, we used a multispectral camera on a DJI P4 multispectral to baseline the processes involved in transforming a highly disturbed, glacially influenced to more stable and diverse landscape. Unmanned Aerial Vehicles (UAVs) can fly under clouds at preferred times, capturing data at cm resolution, filling a significant gap between existing in situ, airborne and satellite remote sensing capabilities. The campaign aimed for (i) georeferenced mapping of marine glacial outflow areas (plumes) of in front of seven glaciers, (ii) analyzing the relationships between air- (multispectral) and water-born (salinity, temperature, turbidity, SPM, TOC, geochemistry, phytoplankton) data for calibration purposes, (iii) surveying erosional processes such as periglacial creeks at unglaciated coasts, which are directly linked to changes in the marine ecosystem (provision and delivery of sediment and solutes from the shore) by SPM, TOC, discharge volume measurements, and (iv) mapping implications for sediment and landscape stability by opportunistic vegetation succession in deglaciated areas.
ANT-Land-SIGMA-I contributes to PoF IV subtopic 4.2 and was funded by AWI and the EU project CoastCarb (Marie Curie Action RISE, Research and Innovation Staff Exchange, H2020-MCSA-RISE 872690). The expedition has been logistically supported by the Argentinean Antarctic Institute (IAA), Chilean Antarctic Institute (INACH), and Institute of Biochemistry and Biophysics, Polish Academy of Sciences (IBB-PAS) for research stays at the Antarctic scientific stations Carlini, Escudero and Arctowski
Impact of climate change on the kelp Laminaria digitata - Simulated Arctic winter warming
Get PDFThe Arctic is seasonally exposed to long periods of low temperatures and complete darkness. Consequently, perennial primary producers have to apply strategies to maximize energy efficiency. Global warming is occurring in the Arctic faster than the rest of the globe. The highest amplitude of temperature rise occurs during Polar Night. To determine the stress resistance of the ecosystemengineering kelp Laminaria digitata against Arctic winter warming, nonmeristematic discs of adult sporophytes from Porsangerfjorden (Finnmark, Norway) were kept in total darkness at 0°C and 5°C over a period of three months. Physiological variables, namely maximum quantum yield of photosynthesis (Fv/Fm) and dry weight, as well as underlying biochemical variables including pigments, storage carbohydrates, total carbon and total
nitrogen were monitored throughout the experiment. Although all samples remained in generally good condition with Fv/Fm values above 0.6, L. digitata performed better at 0°C than at 5°C. Depletion of metabolic products resulted in a constant decrease of dry weight over time. A strong decrease in mannitol and laminarin was observed, with greater reductions at 5°C than at 0°C. However, the
total carbon content did not change, indicating that the sporophytes were not suffering from “starvation stress” during the long period of darkness. A decline was also observed in the accessory pigments and the pool of xanthophyll cycle pigments, particularly at 5°C. Our results indicate that L. digitata has a more active metabolism, but a lower physiological and biochemical performance at higher temperatures in the Arctic winter. Obviously, L. digitata is well adapted to Arctic Polar Night conditions, regardless of having its distributional center at lower
latitudes. Despite a reduced vitality at higher temperatures, a serious decline in Arctic populations of L. digitata due to winter warming is not expected for the near future
Antarctic benthic species distribution models and compositional analysis in a coastal ecosystem under glacier retreat
Get PDFIn the face of global climate change, the West Antarctic Peninsula has been identified as highly vulnerable due to rising temperatures and increased anthropogenic carbon emissions impacting its biodiversity. Species distribution models are useful tools for assessing habitat suit-ability and forecasting responses in a changing environment. At Potter Cove, glacier retreat has opened new ice-free areas for colonization while altering the environment through meltwater input and sediment run-off. This fjord serves as a case study to identify environmental predictors driving Antarctic zoobenthos distribution in a changing coastal ecosystem and to analyze the potential benthic colonization in areas strongly affected by glacier retreat. About 60% of the study area, equivalent to 5.45 km2, was estimated to be suitable for zoobenthic occurrence. Potential spatial co-occurrence was identified in highly glacier-influenced areas. The interpretation of binary transfor-mation thresholds emphasizes taxa-specific environmental requirements responding to glaciologi-cal, oceanographic, and sedimentological predictors, inferring particularities depending on their feeding strategies. A lower threshold value estimated a wider habitat extension. This study enhances our understanding of benthic responses to ongoing environmental shifts due to climate change in the Antarctic coastal ecosystem, emphasizing long-term research to increase our current predictive capacities and improve conservation and management strategies
First release of the Pelagic Size Structure database: global datasets of marine size spectra obtained from plankton imaging devices
Get PDFIn marine ecosystems, most physiological, ecological, or physical processes are size dependent. These include metabolic rates, the uptake of carbon and other nutrients, swimming and sinking velocities, and trophic interactions, which eventually determine the stocks of commercial species, as well as biogeochemical cycles and carbon sequestration. As such, broad-scale observations of plankton size distribution are important indicators of the general functioning and state of pelagic ecosystems under anthropogenic pressures. Here, we present the first global datasets of the Pelagic Size Structure database (PSSdb), generated from plankton imaging devices. This release includes the bulk particle normalized biovolume size spectrum (NBSS) and the bulk particle size distribution (PSD), along with their related parameters (slope, intercept, and R2) measured within the epipelagic layer (0–200 m) by three imaging sensors: the Imaging FlowCytobot (IFCB), the Underwater Vision Profiler (UVP), and benchtop scanners. Collectively, these instruments effectively image organisms and detrital material in the 7–10 000 µm size range. A total of 92 472 IFCB samples, 3068 UVP profiles, and 2411 scans passed our quality control and were standardized to produce consistent instrument-specific size spectra averaged to 1° × 1° latitude and longitude and by year and month. Our instrument-specific datasets span most major ocean basins, except for the IFCB datasets we have ingested, which were exclusively collected in northern latitudes, and cover decadal time periods (2013–2022 for IFCB, 2008–2021 for UVP, and 1996–2022 for scanners), allowing for a further assessment of the pelagic size spectrum in space and time. The datasets that constitute PSSdb’s first release are available at https://doi.org/10.5281/zenodo.11050013 (Dugenne et al., 2024b). In addition, future updates to these data products can be accessed at https://doi.org/10.5281/zenodo.7998799
Race to the poles: the thermal response of the transcriptome of two range-expanding pelagic amphipod species
Get PDFIntroduction: Hyperiid amphipods of the genus Themisto are a key polar zooplankton group in terms of biomass and play an important role as prey for higher trophic levels. They are prone to undergo changes in abundance and distribution in the course of the ongoing environmental changes. In the Southern Ocean, Themisto gaudichaudii is predicted to expand its distribution poleward. In the Arctic, the boreal-Atlantic T. abyssorum increases in abundance, resulting in an increased competition with a genuine polar congener. It is not known, however, whether T. gaudichaudii and T. abyssorum have the potential to efficiently adapt to changing water temperatures at their current distribution range or whether they will be shifting their ranges poleward.
Methods: We exposed the two Themisto species from different geographic populations to temperature-change experiments, a cold treatment and a heat-shock treatment. After that, we carried out transcriptome sequencing to compare gene expression patterns in the different treatments and species.
Results: We show that under similar heat conditions, T. gaudichaudii differentially expressed more genes (26-fold change) than T. abyssorum. Furthermore, we observed qualitative differences between genetic clusters in T. gaudichaudii.
Discussion: The differences observed between genetic clusters in T. gaudichaudii suggest that evolutionary divergence can be linked to changes in the regulatory pathways involved in temperature stress. These could influence the capacity of each genetic cluster to cope differently with temperature changes. In contrast to its congeneric species, T. abyssorum showed a pronounced adaptive flexibility to thermal stress; it appears to have the ability to continue its poleward expansion but may also cope with increasing temperatures in its current environments. Our findings contribute to understand the response of two range-shifting Themisto species to thermal stress in view of the environmental gradients they encounter throughout their current or future distribution ranges
Heterogeneous Basal Thermal Conditions Underpinning the Adélie‐George V Coast, East Antarctica
Get PDFAdélie-George V Land in East Antarctica, encompassing the vast Wilkes Subglacial Basin, has a configuration that could be prone to ice sheet instability: the basin's retrograde bed slope could make its marine terminating glaciers vulnerable to warm seawater intrusion and irreversible retreat under predicted climate forcing. However, future projections are uncertain, due in part to limited subglacial observations near the grounding zone. Here, we develop a novel statistical approach to characterize subglacial conditions from radar sounding observations. Our method reveals intermixed frozen and thawed bed within 100 km of the grounding-zone near the Wilkes Subglacial Basin outflow, and enables comparisons to ice sheet model-inferred thermal states. The signs of intermixed or near thawed conditions raises the possibility that changes in basal thermal state could impact the stability of Adélie-George V Land, adding to the region's potentially vulnerable topographic configuration and sensitivity to ocean forcing driven grounding line retreat
Microplastics and low tide warming: Metabolic disorders in intertidal Pacific oysters (Crassostrea gigas)
Get PDFToxic effects of the emerging Alexandrium pseudogonyaulax (Dinophyceae) on multiple trophic levels of the pelagic food web
Get PDFOn the importance to consider the cloud dependence in parameterizing the albedo of snow on sea ice
Get PDFThe impact of a slightly modified broadband snow surface albedo parameterization, which explicitly considers the cloud dependence of the snow albedo, is evaluated in simulations of a coupled regional climate model of the Arctic. The cloud dependence of the snow albedo leads to a more realistic simulation of the variability of the surface albedo during the snowmelt period in late May and June. In particular, the reproduction of lower albedo values under cloud-free/broken-cloud conditions during the snowmelt period represents an improvement and results in an earlier disappearance of the snow cover and an earlier onset of sea-ice melt. In this way, the consideration of the cloud dependence of the snow albedo results in an amplification of the two-stage snow/ice albedo feedback in the model. This finds expression in considerably increased sea-ice melt during the summer months and ends up in a new quasi-stationary equilibrium in sea ice with statistically significant lower sea-ice volume and statistically significant lower summer sea-ice area