Alfred Wegener Institute for Polar and Marine Research
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Long-term changes in deep-sea megafauna community structure in the eastern Fram Strait (Arctic Ocean)
No full textA major challenge in ecology is understanding whether observed changes are the result of short-term cycles or long-term environmental changes. This study leverages data collected over a 20 yr period from the Long-Term Ecological Research observatory HAUSGARTEN (Stn HG-I; 79°N, 6°E, 1300 m deep) to disentangle dynamics in epibenthic megafauna. We compared community composition to environmental factors using linear models and redundancy analyses. In all cases, combinations of factors associated with cycles and long-term changes were included in best-fit models. Faunal density and species richness increased and then decreased over the study period. Community structure made a partial return to the 2002 state in 2022, suggesting cyclicality. There was turnover in species composition over the study period, likely reflecting long-term environmental change. The North Atlantic seastar Pontaster tenuispinus was first observed in 2018, and the Arctic eelpout fish Lycodonus flagellicauda was not observed after 2012. Our study demonstrates that complex interactions of environmental factors influence community structure in the Arctic deep sea. The 20 yr study period was not sufficient to capture a full cycle in epibenthic megafauna community composition, which may have a period of >20 yr. Overlaid on this pattern are the long-term impacts of rising ocean temperatures and a changing food supply regime. Continued monitoring will likely show further non-linear responses to environmental change
Into the Blue: An ERC Synergy Grant Resolving Past Arctic Greenhouse Climate States
Get PDFThe Arctic Ocean is turning blue. Abrupt Arctic warming and amplification is driving rapid sea ice decline and irreversible deglaciation of Greenland. The already emerging, substantial consequences for the planet and society are intensifying and yet, model-based projections lack validatory consensus. To date, we cannot anticipate how a blue Arctic will respond to and amplify an increasingly warmer future climate, nor how it will impact the wider planet and society. Climate projections are inconclusive as we critically lack key Arctic geological archives that preserved the answers. This “Arctic Challenge” of global significance can only be addressed by investigating the processes, consequences, and impacts of past “greenhouse” (warmer-than-present) climate states. To address this challenge, the ERC Synergy Grant project Into the Blue (i2B) is undertaking a program of research focused on retrieving new Arctic geological archives of past warmth and key breakthroughs in climate model performance to deliver a ground-breaking, synergistic framework to answer the central question: “Why and what were the global ramifications of a “blue” (ice-free) Arctic during past warmer-than-present climates?” Here, we present the proposed research plan that will be conducted as part of this program. Into the Blue will quantify cryosphere (sea ice and land ice) change in a warmer world that will form the scientific basis for understanding the dynamics of Arctic cryosphere and ocean changes to enable the quantitative assessment of the impact of Arctic change on ocean biosphere, climate extremes, and society that will underpin future cryosphere-inclusive IPCC assessments
Effects of Lateglacial and Holocene climate change on southern Baltic environments: a plant sedaDNA and diatom sediment record
Get PDFWe combined multiproxy analyses of plant sedaDNA, diatom, and lithological data from two sediment cores to develop an uninterrupted Lateglacial and Holocene record from the Dūkštelis palaeolake, eastern Lithuania, and compared our findings to published pollen records. SedaDNA provides localised and taxonomically detailed insights into vegetation, surpassing the resolution of pollen data; however, its composition is strongly influenced by aquatic plants, a fact which limits the representation of terrestrial flora to some extent. Macrophyte sedaDNA and diatom data record shifts in lake productivity and water levels, while pollen data reflect a broader regional vegetation context, highlighting the complementarity of these methods. Subalpine and lowland vegetation colonised the region during the Lateglacial. The presence of shrub taxa, like Arctostaphylos uva-ursi and Arctous alpina with colder-adapted species, like Dryadoideae and Pyrola, and herbs characteristic of lowlands in modern environments, like Trifoliaceae, Mentheae, Ranunculaceae, and Plantago, suggests an open but heterogenous environment with diverse microhabitats created under quickly changing geomorphological conditions. A gradual shift to a forested landscape began with the advent of riparian species like Alnus (∼11300 cal yr BP), Viburnum (∼10300–9200 cal yr BP), and deciduous trees including Ulmaceae, Tilia, and Fagaceae from ∼11150, 10000, and 9900 cal yr BP, respectively. Early to Middle Holocene diatom and macrophyte data show that by ∼10000 cal yr BP, the lake had shifted from a shallow mesotrophic-eutrophic state to a deeper eutrophic system. During the Middle to Late Holocene, sedaDNA data suggest a decline in forest vegetation as the lake evolved into a shallow wetland. At this stage, sedaDNA overrepresents species growing directly in and around the lake, and therefore potentially skewing the broader regional picture. In contrast, pollen data suggest a pronounced forest decline from ∼3300 cal yr BP, likely linked to human activities such as forest clearance, which would increasingly shape the landscape from the Middle Holocene. Notable agricultural and pastoral impacts are indicated by the presence of species such as Avena, Brassicaceae, Plantago, and Trifolium starting ∼3700 cal yr BP
Shallow coastal zones are key mediators in Arctic land-ocean carbon fluxes
Get PDFRapid Arctic warming accelerates the erosion of permafrost coasts rich in terrestrial organic carbon (terrOC). Once released into the ocean, terrOC can degrade or get buried in shelf sediments, yet its transport pathways and fate remain poorly understood. We collected permafrost material, sediment and surface water along the Canadian Beaufort Sea coast, fractionating samples by density (cut-off 1.8 g/cm3) and size (38, 63 and 200 µm) before performing geochemical and microscopic analysis. Our results show that ~43% of terrOC is trapped in low-density fractions, mainly as vascular plant debris. Surprisingly, this material is trapped within shallow (0-5 m) waters where waterlogging and large particle size increase its density and settling velocity. Less than 10% is transported to deeper waters (30-55 m), indicating that the shallow coastal zone acts as a trap and biogeochemical reactor. These findings challenge the source-to-sink paradigm and highlight the overlooked and undersampled (< 6% of pan-arctic shelf data) nearshore zone
Occurrence of toxic microalgae and associated toxins in the western Black Sea: insights from the PHYCOB cruise in September 2021
Get PDFHarmful Algal Blooms (HABs) represent a significant global challenge to human health, economies, and ecosystems, including those of the Black Sea. Despite previous reports of potentially toxic microalgae and phycotoxins in the basin, the taxonomy and occurrence of toxigenic species and their associated toxins remain poorly resolved. During the PHYCOB cruise in September 2021, the diversity and distribution of toxigenic microalgae and phycotoxins were investigated across 23 stations in the western Black Sea, covering Bulgarian and Romanian waters. Numerous potentially toxic microalgal taxa were identified using complementary morphological (light microscopy and scanning electron microscopy) and molecular (DNA metabarcoding) methods. The genus Pseudo-nitzschia was the only representative of potentially toxic diatoms, but no domoic acid was found. Among toxic dinoflagellates, Dinophysis spp., Protoceratium reticulatum, Lingulaulax polyedra, and Gonyaulax spp. were frequently observed, along with the related pectenotoxins and yessotoxins. Species distribution modelling indicated that the western Black Sea provides favorable conditions for Dinophysis spp., L. polyedra, and P. reticulatum. Additionally, several Alexandrium species were identified, including the first record of A. fragae in the basin, along with the detection of the associated phycotoxins (GTX-2/3 and GDA). This study provides the first integrated assessment combining light and scanning electron microscopy, DNA metabarcoding, and chemical analyses of toxigenic microalgae in field samples from the western Black Sea, contributing to an improved understanding of their region-specific profiles
Topographic and geologic controls on the Northeast Greenland Ice Stream
Get PDFThe Northeast Greenland Ice Stream (NEGIS) is an elongated feature extending ∼600 km into the interior of the Greenland Ice Sheet. Here, we investigate detailed subglacial topography along the length of the NEGIS to ascertain the characteristics of the ice stream bed. We use topographic analysis (hypsometry, spatial roughness and valley morphometry) to describe and demarcate three geomorphologically distinct regions. The upstream region, near the NEGIS onset, exhibits low roughness and a lack of valleys, indicating the likely presence of subglacial sediments. Downstream, roughness abruptly increases, with two wide subglacial troughs present in the middle region. In the downstream region, the topography displays smaller alpine-like valleys. We propose that these differences are attributable to changing geological provinces, which are poorly constrained in this area. The topography also has a distinct impact on ice stream geometry, as ice flow is generally preferentially steered through a trough. Whilst the upstream regime appears to have little effect on the location of the ice stream onset and shear margins, its low friction enables fast flow that propagates longitudinally upstream from the troughs. On the basis of our data, we argue that the NEGIS is more strongly influenced by basal topography than has been previously suggested
Dissolved and Particulate Organic Carbon Characteristics in Summer and Winter Waters of the Lena Delta
Get PDFRapid Arctic warming accelerates permafrost thaw, altering water flow and organic matter transport to aquatic ecosystems. To identify sources and seasonality of OC at the mouth of the Lena River, we measured summer and winter concentrations and C isotopes (∆14C and δ13C) of DOC and POC along a 140-km transect of the Lena Delta. Despite low water flow during winter, DOC concentrations in the Lena Delta were higher than those measured at the end of the summer (6.31 ± 0.60 and 5.54 ± 0.17 mg L−1, respectively). We found pronounced differences in the DOC isotopic composition of waters between seasons (winter: mean = −16‰ ± 16‰ ranging between −14‰ and 46‰ and summer: mean = 41‰ ± 26‰ in the range between −47‰ and 79‰). ∆14C of winter DOC suggested higher relative contributions of older carbon compared to summer DOC, which is enriched in 14C. POC in winter was lower (0.13 ± 0.06 and 0.40 ± 0.10 mgC L−1, respectively) and enriched in δ13C (−29.7 ± 2.2 and −32.4‰ ± 0.8‰, respectively) compared to summer, while no difference was found for ∆14C. This study with its unique dataset on the largest Arctic delta will help to assess the ongoing changes with climate warming at this frontier between the land and the ocean realm. Explicitly, the inclusion of winter sampling and isotopic analysis makes this study very valuable for assessing the biogeochemical response of the Arctic's biggest delta, as well as beyond
Meta-analysis of stage-specific Calanus finmarchicus vertical distribution in relation to hydrography and chlorophyll in the North Atlantic
Get PDFCalanus finmarchicus is an important, extensively studied zooplankton species in the North Atlantic. Many studies have explored its abundance and life cycle, but basin-wide relationships between its vertical distribution and environment during the feeding season remain poorly known. We conducted a meta-analysis of stage-specific vertical distribution and its relationships with environmental variables (temperature, salinity, irradiance, chlorophyll-a) in the epipelagic layer (0-200 m) of the North Atlantic during spring and summer (21 March to 21 September). Fitting a GAM model, we analyzed data from 47 years (1971-2018) with the aim to discern common, stage-specific responses to environment across the area. Highest abundances were observed in the upper 50 m in spring (at 5°C) and summer (at 7.5°C). The timing of the phytoplankton bloom emerged as a key driver determining vertical distribution, with all stages found shallower during the seasonal surface Chl.-a maximum. Contrary to reports of mismatch with global warming, the data indicated a region-wide match of spring bloom and Calanus. In the coldest areas of its habitat (< 1°C), the copepods stayed closer to surface, potentially to fulfill development, while in warmest areas (>10°C), early stages stayed deeper likely to avoid warm surface waters
Policy brief
Get PDFThis policy brief is one within a series focused on examining the wording within articles of the Chair’s draft text (version published on December 1, 2024) for the Intergovernmental Negotiating Committee to develop an international legally binding instrument on plastic pollution, including in the marine environment. This brief has been published ahead of the INC-5.2 meeting taking place on August 5-14, 2025.
It was developed by members of the Scientists’ Coalition for an Effective Plastics Treaty