Alfred Wegener Institute for Polar and Marine Research
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Of sequences and images - diversity and quantity of Arctic epipelagic zooplankton by an integrative approach
Get PDFDue to the high sensitivity of zooplankton to environmental fluctuations, monitoring their taxonomic composition, abundance and biomass is of high priority to identify changes in the ecosystem. Recent advances in imaging and molecular technologies promise to greatly accelerate the processing of samples to determine both the diversity and quantity of the zooplankton community. In our study, we analyzed the diversity and quantity of an epipelagic Arctic zooplankton community using multi-marker metabarcoding and imaging analysis (ZooScan). We identified a total of 11 phyla and 58 species in the northern Barents Sea and the Nansen Basin. Metabarcoding identified more taxa than image analysis, while imaging provided quantitative information on abundance and biomass. Multivariate analyses revealed overall the same significant environmental drivers (temperature and percentage of Polar Surface Water in the sampling depth layer) explaining the similarity and spatial distribution of the zooplankton community. For all approaches, similar spatial patterns of the zooplankton community were found. Abundance, biovolume and biomass decreased with increasing latitude within the analyzed regions. Based on this study, we recommend ZooScan image analysis in combination with COI metabarcoding for future monitoring of Arctic zooplankton diversity and quantification to ensure the detection of changes in both aspects of these communities
Fading of a sulfate-methane transition in deep and hot subseafloor sediments from the Nankai Trough
No full textBiogeochemical processes in subseafloor sediments change significantly over geological timescales due to changing oceanographic, climatic or depositional conditions. Using dynamic reactive transport modeling, we reconstructed the evolution of biogeochemical processes over the past 5.5 million years in ~1.2-km deep and up to 120°C hot sediments from International Ocean Discovery Program Site C0023 in the Nankai Trough, which records a complex depositional and thermal history. A distinctive feature is an inverse sulfate-methane transition (SMT) with a broad overlap zone between sulfate and methane of ~100 m, located in 80° to 85°C hot sediments. This temperature coincides with the known temperature limit of anaerobic methane-oxidizing microbial communities. Based on the reactive transport model, we show that the inverse SMT was established ~2.5 million years ago (Ma) after the onset of biogenic methanogenesis and anaerobic oxidation of methane (AOM) as a consequence of increased organic carbon burial. Depth-integrated AOM rates decreased markedly since the beginning of trench-style deposition and an associated rapid heating of ~50°C across the sediment column ~0.4 Ma. We argue that the activity of anaerobic methane-oxidizing communities at the inverse SMT has already started to cease and that the SMT is in the process of disappearing. This is the first study that documents the successive fading of an SMT and the decrease in the efficiency of this microbial methane sink as a result of sediment temperature increasing beyond the threshold of being suitable for anaerobic methane-oxidizing microbial communities
Time matters: Transcriptomic insights into temporally regulated reproductive and physiological processes in the life cycle of salps
Get PDFDespite the increasing importance of salps and the recognition of their role as important players in food webs and biogeochemical cycles, their life cycle characteristics and physiology remain mysterious. This uncertainty encourages oversimplifying modeling approaches, leading to inaccuracies that may affect population dynamics results. This lack of knowledge is critical, making it difficult to adequately assess their sensitivity to global warming and their impact on ecosystems if their abundance and distribution change with rising seawater temperatures. Therefore, we generated a de novo transcriptome of Salpa fusiformis to further investigate the physiological processes involved in the life cycle of salps. We examined differentially expressed genes between both reproductive forms, blastozooids and oozoids, and detected a general form-specific difference among Salpa. Furthermore, we identified mainly temporally driven processes (energy delivery, cell communication, spermatogenesis) by studying gene expression profiles of different developmental stages of blastozooids of Salpa fusiformis. A life cycle that physiologically prepares blastozooids during the potential reproductive period, regardless of their fertilization status, may favor rapid response to favorable conditions and formation of salp blooms. Understanding the processes involved will contribute to a better assessment of their sensitivity to environmental change and support the implementation of their role in ecosystem models. In addition, the generated transcriptome was used to select and validate a set of potential reference genes for future qPCR applications. This will facilitate molecular studies of tunicates generally and stimulate future physiological studies on salps
Hygroscopic aerosols amplify longwave downward radiation in the Arctic
Get PDFThis study investigates the impact of hygroscopic aerosols, such as sea salt and sulfate, on longwave downward radiation in the Arctic. These aerosols absorb atmospheric water vapor, leading to wet growth, increased size, and enhanced longwave downward radiation emission, defined as the aerosol infrared radiation effect. Observations of aerosols, especially their composition, are challenging during the Arctic winter. We use an emission Fourier transform spectrometer to measure aerosol composition. Observations show that the aerosol infrared radiation effect of dry aerosols is limited to about 1.45±2.00 W m−2. Wet growth significantly increases this effect. During winter, at relative humidity levels between 60 % and 80 %, wet aerosols exhibit effects approximately 7 times greater than dry aerosols. When relative humidity exceeds 80 %, the effect can be up to 20 times higher. Sea salt aerosols in Ny-Ålesund demonstrate high effect values, while non-hygroscopic aerosols like black carbon and dust show consistently low values. Reanalysis data indicate increased water vapor and sea salt aerosol optical depth in Ny-Ålesund after 2000, correlating with significant positive temperature anomalies in this area. Moreover, wet aerosols can remain activated even in dry environments, continuously contributing high effects, thereby expanding the area affected by aerosol-induced warming. This warming effect may exacerbate Arctic warming, acting as a positive feedback mechanism
Morpho-phylogenetic and toxicological characterisation of Pseudo-nitzschia multiseries from the Sea of Marmara (Türkiye)
No full textPseudo-nitzschia multiseries is a diatom known for producing domoic acid (DA), a neurotoxin that can cause Amnesic Shellfish Poisoning (ASP), which poses risks to both marine life and human health. This study reports the first detailed investigation of P. multiseries in the Sea of Marmara, focusing on its morphology, phylogeny, and toxin production. Morphological analysis using light and electron microscopy confirmed key diagnostic features consistent with P. multiseries. Phylogenetic analysis, focusing on ITS and LSU gene sequences, showed a close genetic relationship between the Turkish strain and other strains of P. multiseries. Domoic acid levels, quantified using LC-MS/MS during exponential and stationary growth phases, ranged between 2.46 and 3.24 pg cell−1, with minor amounts of isoDA (A, D and E) also detected. These findings highlight the importance of monitoring P. multiseries in Turkish coastal waters due to its significant potential for DA production. This study provides valuable insights into the morphology, phylogeny, and toxin production of P. multiseries, as well as its potential implications for management of marine resources and public health protection. It offers a comprehensive examination of this potentially toxic diatom species in Turkish coastal waters
Vibrio are a potential source of novel colistin-resistance genes in European coastal environments
Get PDFColistin is a widespread last resort antibiotic for treatment of multidrug-resistant bacteria. The recent worldwide emergence of colistin resistance (Col-R) conferred by mcr-1 in human pathogens has raised concern, but the putative sources and reservoirs of novel mcr genes in the marine environment remain underexplored. We observed a high prevalence of Col-R, particularly in Vibrio isolated from European coastal waters by using the same cohorts of oysters as bioaccumulators in three sites across Europe. The high sequence diversity found in the mcr/eptA gene family was geographically structured, particularly for three novel eptA gene variants, which were restricted to the Mediterranean (France, Spain) and occurred as a dgkA-eptA operon. The RstA/RstB two component system was shown to control both the dgkA-eptA operon and the Col-R phenotype. The analysis of 29 427 Vibrionaceae genomes revealed that this mechanism of intrinsic resistance is prevalent and specific to the Harveyi clade, which includes the human pathogens Vibrio parahaemolyticus and Vibrio alginolyticus. The operon conferred colistin-resistance when transferred to sensitive non-Vibrio strains. In general, eptA gene variants are widespread and evolved with the Vibrio lineage. They occur in clade-specific genomic environments, suggesting that eptA expression responds to distinct environmental signals across the Vibrio phylogeny. However, we also identified mobile eptA paralogues that have been recently transferred between and within Vibrio clades. This highlights Vibrio as a potential source of Col-R mechanisms, emphasizing the need for enhanced surveillance to prevent colistin-resistant infections in coastal areas
Impact of wildfire smoke on Arctic cirrus formation – Part 1: Analysis of MOSAiC 2019–2020 observations
Get PDFThe potential impact of wildfire smoke on Arctic cirrus formation is discussed based on lidar and radar observations during the winter half year of the 1-year MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition. Aerosol and ice cloud observations were performed aboard the icebreaker Polarstern at latitudes > 85° N. Aged Siberian wildfire smoke polluted the tropopause region over the central Arctic during the entire winter half year of 2019-2020. The smoke particle surface area concentration at the tropopause was of the order of 5-15 μm2cm-3 and indicated considerably enhanced levels of aerosol pollution for more than 6 months. Numerous cirrus systems with cloud-top temperatures between -60 and -75 °C developed in the polluted upper troposphere. We analyzed all MOSAiC winter cirrus layers with respect to their geometrical and optical properties and a subgroup of 20 cirrus events with respect to their ice water content (IWC) and ice crystal number concentration (ICNC). In individual ice fallstreaks that are connected to individual ice nucleation events, ICNCs typically ranged from 1 to 10 crystals L-1 but were frequently also as high as 20-50 L-1; however, observations > 100 L-1 were rare. Three observational facts corroborate our hypothesis that smoke significantly influenced Arctic cirrus formation: (1) the occurrence of a long-lasting, persistent smoke pollution layer in the upper troposphere so that favorable conditions for heterogeneous ice nucleation on smoke particles were always given and, at the same time, homogeneous freezing of background aerosol was probably widely suppressed; (2) the high smoke particle surface area concentrations, which were high enough to significantly trigger ice nucleation on smoke particles (as shown in Part 2, the companion paper to this article; ); and (3) the frequently found maximum cirrus ice saturation ratios of 1.3-1.5, which point to the dominance of heterogeneous ice nucleation processes, initiated by inefficient ice-nucleating particles (INPs), as expected when aged smoke particles (i.e., organic aerosol particles) serve as INPs. The studies are continued in the simulation portion of this work (Part 2; Ansmann et al., 2025)
Calm ocean, stormy sea: atmospheric and oceanographic observations of the Atlantic during the Atlantic References and Convection (ARC) ship campaign
Get PDFDuring the Atlantic References and Convection (ARC) ship campaign with the reference MSM114/2, which took place in early 2023, the German research vessel Maria S. Merian travelled from Mindelo, Cape Verde, to Punta Arenas, Chile. One of the main objectives of ARC was to obtain vertically resolved cross sections of the Intertropical Convergence Zone (ITCZ). To this end, we crossed the ITCZ three times in the meridional direction. We present the atmospheric and oceanographic measurements collected during ARC in a standardised way to facilitate working with data from different instruments and to make the data easily accessible. This approach is not limited to ARC but could serve as a prototype for future (and past) ship campaigns. We present data from the integrated ship sensors (DSHIP); a humidity and temperature profiler (HATPRO); a ceilometer; aerosol instruments (DustTrak, Microtops, and Calitoo); radiosondes; uncrewed aircraft vehicles (UAVs); and conductivity, temperature, and depth (CTD) profiles of the upper ocean. We distinguish between temporal continuous data (DSHIP, HATPRO, Ceilometer, and DustTrak) from point measurements (radiosondes, UAVs, CTDs, Calitoo, and Microtops). To illustrate the data sets provided, we present examples of measurements taken during the three crossings of the ITCZ and during a storm in the Roaring Forties in the South Atlantic at the end of the campaign. An overview of all available data sets, including DOIs and download links, can be found in with the DOI 10.1594/PANGAEA.966616. For references to the individual data sets, please refer to the "Data availability"section
