Alfred Wegener Institute for Polar and Marine Research
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Long-Term Effects of Nutrient Shifts and Warming on Chlorophyll-a in a Temperate Coastal Environment
Full text linkAbstract
Anthropogenically driven nutrient shifts and warming are key stressors affecting phytoplankton in marine coastal environments. The German Bight, a coastal region in the North Sea, has undergone substantial nutrient reductions and rising sea surface temperature (SST) over recent decades. Despite extensive research, the combined long-term effects of nutrient shifts and warming, particularly in the river-influenced coastal area, remain unclear. Here, we aimed to evaluate trends and explore the partial and interactive effects of winter nutrient alterations and seasonal warming on spring chlorophyll-
a
(Chl-
a
) levels. For this purpose, we compiled a comprehensive spatiotemporal dataset (1980–2019) and applied generalized linear mixed models. Results showed that spring Chl-
a
concentrations peaked in the 1980s and 1990s, with values surpassing 30 µg L
−1
in the Elbe estuary. Concentrations declined to < 15 µg L
−1
in the following decades, although values > 15 µg L
−1
persisted in the southern inner coastal waters. Decreasing winter dissolved inorganic nitrogen (DIN) emerged as the primary driver of declining spring Chl-
a
in coastal waters (estimate = 0.40,
p
< 0.01), while winter phosphorus and nitrogen-to-phosphorus ratios were not significant predictors. Spring SST had a weak positive effect on Chl-
a
(estimate = 0.09,
p
= 0.03), suggesting that warming during spring may enhance phytoplankton growth. Together, winter DIN and spring SST explained 30% of the variance in spring Chl-
a
. Additional factors, such as light availability and grazing, likely contribute to unexplained variability. This study provides evidence that nutrient reductions have successfully lowered chlorophyll levels, but persistent hotspots in the inner coastal waters highlight the need for targeted management under continued warming.
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Noisy waters affect feeding and metabolic enzyme activities of amphipod mesograzers
Full text linkThe consequences of the progressive intrusion of anthropogenic noise into natural oceanic soundscapes are largely unknown despite the fact that most metazoans utilize sound or vibration for intra- and interspecific interactions as well as orientation. Coastal ecosystems in particular can be characterized by a high level of human activity and thus anthropogenic noise sources. Here, we studied the impact of such noise on marine mesograzers, small invertebrates that play crucial ecological roles by controlling macrophyte growth while serving as key food sources for higher trophic levels in algae-dominated coastal ecosystems. The effect of added continuous low-frequency noise on the habitat choice, feeding rate, and metabolic enzyme activities of the amphipod mesograzer Marinogammarus marinus was tested in a controlled laboratory setting. While habitat choice appeared unaffected by the added noise, exposed animals exhibited reduced feeding performance as well as altered metabolic enzyme activities. If sustained, the physiological homeostasis of M. marinus and their role in the ecosystem may be jeopardized. The ever-rising sound levels in the oceans may thus have consequences for algae-dominated animal communities in coastal areas
Permafrost soils as a Pollutant Barrier – are Organic Contaminants released from failing Drilling Mud Sumps in the Mackenzie Delta?
Full text linkThe toxic properties and bioaccumulation tendencies of numerous organic chemicals pose significant threats to environmental and human health. Even within the Arctic, there is evidence of banned persistent organic pollutants (POPs) and further pollutants classified as chemicals of emerging Arctic concern (CEACs). Their presence in permafrost-affected soils is due both to their partitioning from the atmosphere to liquid or solid phases, promoted by the cold temperatures prevailing in the Arctic, and direct input from the few local sources in these sparsely populated areas. The Mackenzie Delta Region, for instance, experienced extensive oil and gas exploration activities from the 1960s to the early 2000s. During this time, drill cuttings and drill fluids were disposed of in large sumps typically excavated adjacent to the well-head, often under inappropriate construction and abandonment practices.
As the polar regions are now warming twice the global rate, contaminant distribution pathways to and within the Arctic are changing. Permafrost thaw - one of the most significant processes upon warming - may have profound effects on the inherent pollutant sink, including the 233 documented drilling mud sumps in the Mackenzie Delta region. More than half of the constructed sumps, encapsulating significant amounts of drilling fluids, now show major signs of structural failure. With sump cap subsidence and collapse, there is growing concern that organic pollutants such as oil and drilling fluid additives may be released to the environment.
In this study, we analyze soils on and downstream of four selected drilling mud sumps along the Inuvik-Tuktoyaktuk Highway. Through detailed non-target screenings of extractable organic compounds, we will investigate the potential presence of various organic contaminants and assess their concentration levels above and below the permafrost table. This research aims to provide a first assessment of potential contaminant dispersion and degradation in permafrost-affected soils related to the legacy gas exploration in the region
Water in a heated world
Full text linkThe report 'Water in a heated World' comes to the conclusion that national and international water policy must adapt to ongoing, accelerated changes in the global water cycle and respond to them quickly and comprehensively. The effects of climate change, the overexploitation of water resources, the unequal distribution of water, the loss of ecosystem services, and related health risks are increasingly leading to water emergencies. Recent examples include the declaration of a water emergency in Bogotá (Columbia) and Mexico-City due to water shortages, large-scale catastrophic flooding events in Central Asia, or the increasing pollution of water resources in many parts of Africa. The WBGU expects such regional water emergencies to occur more and more frequently, so we can now speak of a global pattern. We see this as a threat with a global dimension. In extreme cases, situations arise that are beyond the limits of controllability. They can lead to the destabilization of political, societal and ecological systems. Climate-change mitigation, the protection of ecosystems and a climate-resilient, socially balanced water management are the most important measures for preventing water emergencies. Water needs to be placed higher on the international political agenda
Testing the reliability of global surface temperature reconstructions of the Last Glacial Cycle with pseudo-proxy experiments
Full text linkAbstract. Reconstructions of past variations in the global mean surface temperature (GMST) are used to characterise the Earth system response to perturbations and to validate Earth system simulations. Beyond the instrumental period, reconstructions rely on local proxy temperature records and algorithms aggregating these records. Here, we propose to establish standards for evaluating the performance of such reconstruction algorithms. Our framework relies on pseudo-proxy experiments (PPEs). That is, we test the ability of an algorithm to reconstruct a simulated GMST, using artificially generated proxy data created from the same simulation. We apply the framework to an adapted version of the GMST reconstruction algorithm used in Snyder (2016) and the metadata of the synthesis of marine proxy records for the temperature of the last 130 kyr from Jonkers et al. (2020). We use an ensemble of four transient simulations of the Last Glacial Cycle (LGC) or the last 25 kyr for the pseudo-proxy experiments. Given the dataset and the algorithm, we find that the reconstruction is reliable for timescales longer than 4 kyr during the last 25 kyr. However, beyond 40 kyr BP, age uncertainty limits the reconstruction reliability to timescales longer than 15 kyr. For the long timescales, uncertainty on temperature anomalies is caused by a factor that re-scales near-global-mean sea surface temperatures to GMST, the proxy measurements, the specific set of record locations, and potential seasonal biases. Increasing the number of records significantly reduces all sources of uncertainty but the scaling. We also show that a trade-off exists between the inclusion of many records, which reduces the uncertainty on long timescales, and of only records with low age uncertainty, high accumulation rate, and high resolution, which improves the reconstruction of the short timescales. Finally, the method and the quantitative results presented here can serve as a basis for future evaluations of reconstructions. We also suggest future avenues to improve reconstruction algorithms and discuss the key limitations arising from the proxy data properties.
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Post‐Glacial Vegetation Trajectories on the Eastern Tibetan Plateau Reflect Millennial‐Scale Migration Lags in Complex Mountain Terrain Based on Sedimentary Ancient DNA and Dynamic Dispersal Modeling
Full text linkMountains with complex terrain and steep environmental gradients are biodiversity hotspots such as the eastern Tibetan Plateau (TP). However, it is generally assumed that mountain terrain plays a secondary role in plant species assembly on a millennial time-scale compared to climate change. Here, we investigate plant richness and community changes during the last 18,000 years at two sites: Lake Naleng and Lake Ximen on the eastern TP with similar elevation and climatic conditions but contrasting terrain. We applied plant DNA metabarcoding to lake sediments leveraging a new regional reference database for taxa identification. Furthermore, we developed a simplified species dispersal model named SMARC. This was used to simulate species migration along river valleys in response to past climate change at the taxonomic resolution of the sedimentary ancient DNA (sedaDNA) approach. Statistical analyses, including ordination-based ecological trajectory analysis, yielded a significant match between sedaDNA and simulated results at single taxon and community levels including certain site-specific differences. Steep terrain downstream of Lake Naleng enhances connectivity to glacial lowland refugia during postglacial warming. In contrast, gentle terrain over long distances implies weak connectivity to the lowland and thus resulted in a strong migration lag at Lake Ximen. Likewise, terrain differences among our sites defined the different connectivity to alpine refugia during late-Holocene cooling. Our consistent proxy- and model-based results, for the first time, indicate that dispersal related migration lags in complex mountain terrain lead to uneven vegetation trajectories at sites with similar climatic conditions mainly because of differences in connectivity to refugia. Ultimately our results indicate that connectivity to refugia is a first-order factor for species migration in addition to elevation-related climatic conditions shaping the postglacial vegetation trajectory in mountainous terrain. This has hitherto largely been ignored when forecasting mountain vegetation responses to climate change and related risk assessment
Prokaryotic microbiota outperform eukaryotic microbiota in differentiating between infection states of iconic diseases of two commercial oyster species
Full text linkThe changing nature of future Arctic marine heatwaves and its potential impacts on the ecosystem
Full text linkAbstractMarine heatwaves (MHWs), defined as extreme ocean warming episodes, have strengthened over the past decades. High-resolution climate models improve understanding of MHWs under global warming, but such events in the future Arctic are currently overlooked. In a high-resolution climate model, we find Arctic MHWs intensify on orders of magnitude during the warming twenty-first century, following sea ice retreat. However, with little sea ice coverage, strong interannual variability emerges, which could surpass the amplitude of former intensification. Furthermore, the enhancement of MHWs correlates with an order of magnitude increase in the rate of change in the temperature anomaly. Additionally, MHWs are found to be accompanied by stratification enhancement, which could surpass interannual variability of future stratification. Such extreme temperature fluctuations combined with stratification enhancement suggest major challenges for Arctic ecosystems, and may negatively impact food webs through direct physiological temperature effects, as well as indirectly through nutrient supply and taxonomic shifts.</jats:p
Lena River biogeochemistry captured by a 4.5-year high-frequency sampling program
Full text linkThe Siberian Arctic is warming rapidly, causing permafrost to thaw and altering the biogeochemistry of aquatic environments, with cascading effects on the coastal and shelf ecosystems of the Arctic Ocean. The Lena River, one of the largest Arctic rivers, drains a catchment dominated by permafrost. Baseline discharge biogeochemistry data are necessary to understand present and future changes in land-to-ocean fluxes. Here, we present a high-frequency 4.5-year-long dataset from a sampling program of the Lena River's biogeochemistry, spanning April 2018 to August 2022. The dataset comprises 587 sampling events and measurements of various parameters, including water temperature, electrical conductivity, stable oxygen and hydrogen isotopes, dissolved organic carbon concentration and 14C, colored and fluorescent dissolved organic matter, dissolved inorganic and total nutrients, and dissolved elemental and ion concentrations. Sampling consistency and continuity and data quality were ensured through simple sampling protocols, real-time communication, and collaboration with local and international partners. The data are available as a collection of datasets separated by parameter groups and periods at https://doi.org/10.1594/PANGAEA.913197 (Juhls et al., 2020b). To our knowledge, this dataset provides an unprecedented temporal resolution of an Arctic river's biogeochemistry. This makes it a unique baseline on which future environmental changes, including changes in river hydrology, at temporal scales from precipitation event to seasonal to interannual can be detected
Close Correlation Between Vertically Integrated Tropospheric Water Vapor and the Downward, Broadband Thermal‐Infrared Irradiance at the Ground: Observations in the Central Arctic During MOSAiC
Full text linkThe impact of the vertical distribution of tropospheric water vapor on the cloud‐free downward,
broadband thermal‐infrared irradiance (FTIR) was quantified using observations in the Central Arctic, north of
85°N, collected during the Arctic winter. The water vapor profiles were measured with a temporal resolution of
30 s using a Raman lidar. The observations revealed maximum values of integrated water vapor (IWV) contents
of 3.6 kg m^-2. Seven measurement cases of several‐hour durations of slowly changing air masses were
examined. Furthermore, 53 rather short‐term (10 min) measurement cases were studied. The temporal evolution
of the slowly changing air masses revealed a linear relationship between FTIR and IWV with slopes between 7.17 and 12.95 W kg^-1 and a coefficient of determination larger than 0.95 for most of the selected cases. The slopes
and the ordinate intercepts showed a dependence on the water vapor‐weighted mean temperature (representative
temperature of the water vapor distribution). The temperature determined with the Stefan‐Boltzmann law from FTIR correlated with the representative temperature with a coefficient of determination of 0.92. The analysis of
53 independent short‐term observations of different air masses confirmed the linear relationship between FTIR
and IWV at wintertime cloud‐free conditions in the Arctic (coefficient of determination of 0.75, slope of
19.95 W kg^-1 , and ordinate intercept of 107.22 W m^-2)