Alfred Wegener Institute for Polar and Marine Research
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A machine learning model and biometric transformations to facilitate European oyster monitoring
Get PDFAbstract Ecosystem monitoring, especially in the context of marine conservation and management requires abundance and biomass metrics, condition indices, and measures of ecosystem services of key species, all of which can be calculated using biometric transformation factors. Following ecosystem restoration measures in the North Sea and north-east Atlantic waters, European oyster (Ostrea edulis) restoration and its monitoring have substantially increased over the past decade. Restoration activities are implemented by diverse approaches and practitioners ranging from governmental conservation agencies, research institutions and non-governmental institutions to regional groups, including citizen science projects. Thus, tools for facilitating data acquisition and estimation with non-destructive techniques can support monitoring quantitatively and qualitatively. Weight-to-weight transformation factors for calculating dry weight of O. edulis from wet weight measurements are presented. Another important tool is the estimation of weight only from size measurements. The classical approach to achieve these transformation factors is the construction of allometric models, which, however, can greatly vary among regions and between years, making them extremely location/season specific. Alternative and more flexible models constructed using random forests are proposed. This algorithm is a machine learning technique that is increasingly used in ecology, and has been proven to outperform other predictive models. From biometric variable measurements of 1,401 O. edulis individuals, allometric models were used to estimate total, shell and body wet weights, and compare them with 15 random forest models. In general, the random forest models outperformed the allometric ones, with lower error when estimating weight. The developed random forest models can thus provide a tool for facilitating oyster restoration monitoring by increasing data acquisition without the need of sacrificing European oyster individuals. Their improvement can imply its implementation in other regions and support European oyster restoration and monitoring efforts throughout Europe
Valorization of reverse osmosis concentrate in the production of Litopenaeus vannamei and New Zealand spinach in an aquaponic system with biofloc
Get PDFThe process of desalination through filtering membranes leads to the issue of generating a residue with a high concentration of salts, called concentrate. This residue is an environmental pollutant, especially when desalination is carried out far away from the sea (i.g., desalination in northeastern Brazil). In this context, the objective of the present research was to study the valorization of desalination concentrate through an aquaponic system. The feed water (brackish water) was desalinated, generating the concentrate, which was used for the operation of the experimental aquaponic pilot system in the cultivation of Litopenaeus vannamei (known as Pacific white shrimp) and New Zealand spinach (Tetragonia tetragonioides) in microbial biofloc. The initial average weight of the shrimp was 1.5 g and the stocking density used in the culture was 250 shrimp m−3. The experiment was carried out for 74 days, and the final weight was 14.57 g and survival was 18 %. The low survival may be due to the high concentration of nitrite in the culture water 11.75 mg/L, which can be toxic to shrimp, and also due to the ionic balance of the system that was not close to seawater. Therefore, it is recommended to start the experiment when the biofloco system is in the chemoautotrophic stage, with the nitrification process established, or work with higher salinity. The spinach experiment was carried out for 49 days, with an initial biomass of 29.38 g and a final biomass of 519.41 g. Iron deficit was observed in the spinach leaves, thus, adding iron into the system is recommended. The results obtained could encourage the use of technology that is simple to apply and brings benefits to the community. Thus, the valorization of the waste produced in the desalination of water by reverse osmosis membranes reduces its inherent impact on the deposition of concentrate in natural environments
On the linkage between future Arctic sea ice retreat, Euro-Atlantic circulation regimes and temperature extremes over Europe
Get PDFThe question to what extent Arctic sea ice loss is able to affect atmospheric dynamics and climate extremes over mid-latitudes still remains a highly debated topic. In this study we investigate model experiments from the Polar Amplification Model Intercomparison Project (PAMIP) and compare experiments with future sea ice loss prescribed over the entire Arctic, as well as only locally over the Barents and Kara seas, with a present-day reference experiment. The first step is to perform a regime analysis and analyze the change in occurrence frequencies of five computed Euro-Atlantic winter circulation regimes. Forced by future Arctic sea ice conditions, most models show more frequent occurrences of a Scandinavian blocking pattern in at least 1 winter month, whereas there is an overall disagreement between individual models on the sign of frequency changes of two regimes that, respectively, resemble the negative and positive phase of the North Atlantic Oscillation. Focusing on the ECHAM6 PAMIP experiments, we subsequently employ a framework of conditional extreme-event attribution. It demonstrates how detected regime frequency changes can be used to decompose sea-ice-induced frequency changes of European temperature extremes into two different contributions: one "changed-regime"term that is related to dynamical changes in regime occurrence frequencies and another more thermodynamically motivated "fixed-regime"contribution that is related to increased surface temperatures during a specific circulation regime. We show how the overall fixed-regime warming effect and also an increased Scandinavian blocking pattern frequency under future sea ice reductions can equally contribute to and shape the overall response signal of European cold extremes in midwinter. We also demonstrate how a decreased occurrence frequency of an anticyclonic regime over the eastern Atlantic dynamically counteracts the fixed-regime warming response and results in no significant changes in overall January warm-extreme occurrences. However, when compared to other characteristics of future climate change, such as the thermodynamical impact of globally increased sea surface temperatures, the effects of Arctic sea ice loss on European temperature extremes are of secondary relevance
The extremely hot and dry 2018 summer in central and northern Europe from a multi-faceted weather and climate perspective
Get PDFThe summer of 2018 was an extraordinary season in climatological terms for northern and central Europe, bringing simultaneous, widespread, and concurrent heat and drought extremes in large parts of the continent with extensive impacts on agriculture, forests, water supply, and the socio-economic sector. Here, we present a comprehensive, multi-faceted analysis of the 2018 extreme summer in terms of heat and drought in central and northern Europe, with a particular focus on Germany. The heatwave first affected Scandinavia in mid-July and shifted towards central Europe in late July, while Iberia was primarily affected in early August. The atmospheric circulation was characterized by strongly positive blocking anomalies over Europe, in combination with a positive summer North Atlantic Oscillation and a double jet stream configuration before the initiation of the heatwave. In terms of possible precursors common to previous European heatwaves, the Eurasian double-jet structure and a tripolar sea surface temperature anomaly over the North Atlantic were already identified in spring. While in the early stages over Scandinavia the air masses at mid and upper levels were often of a remote, maritime origin, at later stages over Iberia the air masses primarily had a local-to-regional origin. The drought affected Germany the most, starting with warmer than average conditions in spring, associated with enhanced latent heat release that initiated a severe depletion of soil moisture. During summer, a continued precipitation deficit exacerbated the problem, leading to hydrological and agricultural drought. A probabilistic attribution assessment of the heatwave in Germany showed that such events of prolonged heat have become more likely due to anthropogenic global warming. Regarding future projections, an extreme summer such as that of 2018 is expected to occur every 2 out of 3 years in Europe in a +1.5°C warmer world and virtually every single year in a +2°C warmer world. With such large-scale and impactful extreme events becoming more frequent and intense under anthropogenic climate change, comprehensive and multi-faceted studies like the one presented here quantify the multitude of their effects and provide valuable information as a basis for adaptation and mitigation strategies
Effects and perception of marine introduced species by stakeholders in the Wadden Sea—an exploratory approach
No full textAs a result of globalization of markets and increasing marine traffic, more than 130 introduced species have so far been recorded in the Wadden Sea. This unique coastal area constitutes an ecosystem of global importance and is recognized by UNESCO as a Natural World Heritage site. Efforts are made to monitor introduced species and to study their ecological effects on native species and biodiversity, ecosystem processes, and functioning. Social aspects that relate introduced species specifically to people and human society, however, are less studied. To explore this rather new field of research, qualitative interviews were conducted with stakeholders of the Wadden Sea, asking (1) How do introduced species affect people’s lives and (2) How do people perceive introduced species? The interviews were evaluated with a qualitative content analysis. As one first result of this exploratory study it turned out that immaterial aspects of the Wadden Sea, such as recreational potential and cultural identity, appear to be largely affected by introduced species. Moreover, the mere fact of change was mostly regarded with skepticism or aversion, regardless of actual effects. Based on the stakeholder interviews, a conceptual framework with the factors identified as influencing perception was developed. It is suggested that a better understanding of the social component is essential for an integrated management and sustainable solutions
Deglacial and Holocene sea-ice and climate dynamics in the Bransfield Strait, northern Antarctic Peninsula
Get PDFThe reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice-ocean-Atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-Term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO25, a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13ĝ€¯800-13ĝ€¯000 years before present (13.8-13ĝ€¯ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3ĝ€¯ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively
Cirrus clouds in the tropical tropopause layer observed at Koror, Palau (7.34°N, 134.47°E)
Get PDFA Compact Cloud and Aerosol LIDAR (ComCAL) is operated in Koror, Palau (7.34&#176;N, 134.47&#176;E) since 2018. Palau is located in the Pacific warm pool, which plays an important role in global stratosphere-troposphere exchange in the upper troposphere and the lower stratosphere (UTLS). ComCAL is operated during nighttime, carried out observations of atmospheric profiles of aerosols and clouds, and the lidar profile extends from 8 km to 30 km. Cirrus clouds were detected with very high occurrence in the upper troposphere (above 12 km). The subvisible clouds (with an optical thickness of less than 0.3) often occur in the higher region of the tropical tropopause layer (TTL) above about 16 km which is close to the cold point. The transport of air in this layer with thin cirrus and subvisible clouds was investigated by the TRACZILLA Lagrangian model, a variation of FLEXPART. The back-trajectory analysis gives insight into the origins of cirrus clouds in the TTL whether it is related to the convection or the in situ uplifting of the air masses.</jats:p
Ground-based remote sensing of aerosol properties using high-resolution infrared emission and lidar observations in the High Arctic
Get PDFArctic amplification, the phenomenon that the Arctic is warming faster than the global mean, is still not fully understood. The Transregional Collaborative Research Centre "TRR 172: ArctiC Amplification: Climate Relevant Atmospheric and SurfaCe Processes, and Feedback Mechanisms (AC)3"program, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), contributes towards this research topic. For the purpose of measuring aerosol components, a Fourier transform infrared spectrometer (FTIR), for measuring downwelling emission (in operation since 2019), and a Raman lidar are operated at the joint Alfred Wegener Institute for Polar and Marine Research and Paul Emile Victor Institute (AWIPEV) research base in Ny-Ålesund, Spitsbergen (79N, 12E). To carry out aerosol retrieval using measurements from the FTS, the LBLDIS retrieval algorithm, based on a combination of the Line-by-Line Radiative Transfer Model (LBLRTM) and the DIScrete Ordinate Radiative Transfer (DISORT) algorithm, is modified for different aerosol types (dust, sea salt, black carbon, and sulfate), aerosol optical depth (AOD), and effective radius (Reff). Using lidar measurement, an aerosol and cloud classification method is developed to provide basic information about the distribution of aerosols or clouds in the atmosphere and is used as an indicator to perform aerosol or cloud retrievals with the FTS. Therefore, a two-instrument joint-observation scheme is designed and subsequently used on the data measured from 2019 to the present. In order to introduce this measurement technique in detail, an aerosol-only case study is presented using data from 10 June 2020. In the aerosol-only case, the retrieval results show that sulfate is the dominant aerosol throughout the day (τ900cm-1Combining double low line0.007±0.0027), followed by dust (τ900cm-1Combining double low line0.0039±0.0029) and black carbon (τ900cm-1Combining double low line0.0017±0.0007). Sea salt (τ900cm-1Combining double low line0.0012±0.0002), which has the weakest emission ability in the infrared wave band, shows the lowest AOD value. Such proportions of sulfate, dust, and BC also show good agreement with Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) reanalysis data. Additionally, comparison with a Sun photometer (AErosol RObotic NETwork - AERONET) shows the daily variation in the AOD retrieved from FTS to be similar to that retrieved by Sun photometer. Using this method, long-term observations (from April to August 2020) are retrieved and presented. We find that sulfate is often present in the Arctic; it is higher in spring and lower in summer. Similarly, BC is also frequently observed in the Arctic, with less obvious seasonal variation than sulfate. A BC outburst event is observed each spring and summer. In spring, sulfate and BC are dominant, whereas sea salt and dust are relatively low. In addition, a sea salt enhancement event is observed in summertime, which might be due to the melting of sea ice and emissions from nearby open water. From the retrieved results over a long time period, no clear correlations are found; thus, the aforementioned species can be retrieved independently of one another
(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 textMorphological and Phylogenetic Characterisation of Prorocentrum spinulentum, sp. nov. (Prorocentrales, Dinophyceae), a Small Spiny Species from the North Atlantic
Get PDFProrocentrum comprises dinophytes with several unique traits, including the presence of two large thecal plates and apical insertion of flagella. Species delimitation for many small and similar planktonic species is challenging, as SEM analyses and DNA sequence information of type material are rarely available. Based on a strain from the North Atlantic Prorocentrum spinulentum, sp. nov. is described here. Cells were small (9.0–12.8 m long, 8.5–11.9 m deep), oval to almost round in lateral view and moderately compressed. The ovoid nucleus was in median or slightly sub-median
position on the cells ventral side. The plate surface appeared spiny in light microscopy with thecal pores visible in empty thecae. Electron microscopy revealed plates densely covered by relatively long spines and two size classes of thecal pores. The periflagellar area consisted of 8 platelets, and there was a prominent wing (ca. 1 mwide and long) on platelet 1. The new species is distinct in DNA trees and embedded in the Prorocentrum shikokuense species group. It differs from the protologues of other small species of Prorocentrum by the unique combination of cell size and shape, the presence of long spines on the thecal plate surface and scattered thecal pores. The thorough morphological description of this species, representing a previously uncharacterised lineage within Prorocentrum, increases and improves our knowledge of the diversity within this important group of planktonic organisms