Alfred Wegener Institute for Polar and Marine Research
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The social science of offshore aquaculture: uncertainties, challenges and solution-oriented governance needs
Get PDFAquaculture technology is on the move, enabling production in more open and exposed ocean environments around the world. These new systems offer solutions to environmental challenges facing conventional aquaculture, yet new technologies also create new social challenges while potentially exacerbating, or at minimum recreating, others. Offshore aquaculture research and governance are still in early stages, as is our understanding of the social repercussions and challenges associated with development. This paper provides an evaluation and reflection on offshore aquaculture from a social science perspective and is based on findings from a modified World Café group discussion method including the thoughts and experiences of social science experts. Key challenges and uncertainties including a lack of an appropriate regulatory framework, societal perceptions of offshore aquaculture, and offshore aquaculture’s contribution to society were identified. The governance implications of these challenges are discussed as well as the need for social sciences to address these challenges through transformative and transdisciplinary approaches that bridge science and society.</jats:p
West African Monsoon System’s Responses to Global Ocean–Regional Atmosphere Coupling
Get PDFThis study explores the added value (AV) of a regional Earth system model (ESM) compared to an atmosphere-only regional climate model (RCM) in simulating West African monsoon (WAM) rainfall. The primary goals are to foster discussions on the suitability of coupled RCMs for WAM projections and deepen our understanding of ocean–atmosphere coupling’s influence on the WAM system. The study employs results from dynamical downscaling of the ERA-Interim reanalysis and Max Plank Institute ESM, low resolution (MPI-ESM-LR), by two RCMs, atmosphere only (REMO) and REMO coupled with Max Planck Institute Ocean Model (MPIOM) (ROM), at ~25-km horizontal resolution. Results show that in regions distant from coupling domain boundaries such as West Africa (WA), constraint conditions from ERA-Interim are more beneficial than coupling effects. REMO, reliant on oceanic sea surface temperatures (SSTs) from observations and influenced by ERA-Interim, is biased under coupling conditions, although coupling offers potential advantages in representing heat and mass fluxes. Contrastingly, as intended, coupling improves SSTs and monsoon fluxes’ relationships under ESM-forced conditions. In this latter case, the coupling features a dipole-like spatial structure of AV, improving precipitation over the Guinea Coast but degrading precipitation over half of the Sahel. Our extensive examination of physical processes and mechanisms underpinning the WAM system supports the plausibility of AV. Additionally, we found that the monsoonal dynamics over the ocean respond to convective activity, with the Sahara–Sahel surface temperature gradient serving as the maintenance mechanism. While further efforts are needed to enhance the coupled RCM, we advocate for its use in the context of WAM rainfall forecasts and projections
The effect of irradiance versus light dose on the antioxidant activity of two strains of Ulva lacinulata
Get PDFThe genus Ulva, described as a good source of antioxidants known for its antibacterial properties and associated with the capacity to adapt to different environments and high growth rates, has justified the increasing interest in its large-scale production. While extensive research has been done on optimizing the extraction of Ulva’s bioactive compounds, few studies were conducted on increasing or optimizing antioxidant activity (AA) of Ulva spp. during cultivation. Our study aimed to investigate an optimization method of Ulva lacinulata by testing the impact of light dose and irradiance on its AA. Two geographically different strains (NE-Atlantic and Mediterranean) were observed for 5 days under two irradiances (70 or 185 µmol photons m−2 s−1) with the same light dose (4 mol photons m−2 d−1). Samples were collected at different times (0, 3, 24, 48 and 120 h) to evaluate their antioxidant activity (with 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical decolorization assay) and photosynthetic performance (with Pulse Amplitude Modulated fluorometer). A strain-dependent response was observed in the NE-Atlantic strain which had significantly higher AA after 5 days (89 %) under the photosynthetic saturating irradiance, while the Mediterranean strain was not impacted, suggesting that light dose may significantly affect AA in certain Ulva spp
Bile acid fitness determinants of a Bacteroides fragilis isolate from a human pouchitis patient
Get PDFBacteroides fragilis comprises 1% 5% of the gut microbiota in healthy humans but can expand to >50% of the population in ulcerative colitis (UC) patients experiencing inflammation.The mechanisms underlying such microbial blooms are poorly understood, but the gut of UC patients has physicochemical features that differfrom healthy patients and likely impact microbial physiology. For example, levels of the secondary bile acid deoxycholate (DC) are highly reduced in the ileoanal J-pouch of UC colectomy patients. We isolated a B. fragilis strain from a UC patient with pouch inflammation(i.e., pouchitis) and developed it as a genetic model system to identify genes and pathways that are regulated by DC and that impact B. fragilis fitnessin DC and crude bile. Treatment of B. fragilis with a physiologically relevant concentration of DC reduced cell growth and remodeled transcription of one-quarter of the genome. DC strongly induced expression of chaperones and select transcriptional regulators and effluxsystems, and down-regulated protein synthesis genes. Using a barcoded collection of ∼50,000 unique insertional mutants, we further definedB. fragilis genes that contribute to fitnessin media containing DC or crude bile. Genes impacting cell envelope functions including cardiolipin synthesis, cell surface glycosylation, and systems implicated in sodium-dependent bioenergetics were major bile acid fitnessfactors. As expected, there was limited overlap between transcriptionally regulated genes and genes that impacted fitnessin bile when disrupted. Our study provides a genome-scale view of a B. fragilis bile response and genetic determinants of its fitnessin DC and crude bile. IMPORTANCE The Gram-negative bacterium Bacteroides fragilis is a common member of the human gut microbiota that colonizes multiple host niches and can influencehuman physiology through a variety of mechanisms. Identificationof genes that enable B. fragilis to grow across a range of host environments has been impeded in part by the relatively limited genetic tractability of this species. We have developed a high-Throughput genetic resource for a B. fragilis strain isolated from a UC pouchitis patient. Bile acids limit microbial growth and are altered in abundance in UC pouches, where B. fragilis often blooms. Using this resource, we uncovered pathways and processes that impact B. fragilis fitnessin bile and that may contribute to population expansions during bouts of gut inflammation
Potential to recover a record of Holocene climate and sea ice from Müller Ice Cap, Canada
Get PDFAbstract
Müller Ice Cap sits on Umingmat Nunaat (Axel Heiberg Island), Nunavut, Canada, ~ 80°N. Its high latitude and elevation suggest it experiences relatively little melt and preserves an undisturbed paleoclimate record. Here, we present a suite of field measurements, complemented by remote sensing, that constrain the ice thickness, accumulation rate, temperature, ice-flow velocity, and surface-elevation change of Müller Ice Cap. These measurements show that some areas near the top of the ice cap are more than 600 m thick, have nearly stable surface elevation, and flow slowly, making them good candidates for an ice core. The current mean annual surface temperature is −19.6 °C, which combined with modeling of the temperature profile indicates that the ice is frozen to the bed. Modeling of the depth-age scale indicates that Pleistocene ice is likely to exist with measurable resolution (300–1000 yr m−1) 20–90 m from the bed, assuming that Müller Ice Cap survived the Holocene Climatic Optimum with substantial ice thickness (~400 m or more). These conditions suggest that an undisturbed Holocene climate record could likely be recovered from Müller Ice Cap. We suggest 91.795°W, 79.874°N as the most promising drill site.</jats:p
Diversity, toxicity, and distribution of potentially toxic diatoms in Antarctic waters––With description of Pseudo-nitzschia meridionalis sp. nov. and P. glacialis sp. nov.
Get PDFDiatoms of the genus Pseudo-nitzschia, known for their potential toxicity, are integral to the phytoplankton community of the Southern Ocean, which surrounds Antarctica. Despite their ecological importance, the diversity and toxicity of Pseudo-nitzschia in this region remain underexplored. Globally, these diatoms are notorious for forming harmful algal blooms in temperate and tropical waters, causing significant impacts on marine life, ecosystems, and coastal economies. However, detailed information on the diversity, morphology, and toxicity of Pseudo-nitzschia species in Antarctic waters is limited, with molecular characterizations of these species being particularly scarce. During three research expeditions to the Southern Ocean, monoclonal strains of Pseudo-nitzschia were isolated and cultivated. Stored samples from a fourth expedition, the Brategg expedition, were used to complete the description of particularly P. turgidula. Through electron microscopy and molecular analysis, two novel species were identified—Pseudo-nitzschia meridionalis sp. nov. and Pseudo-nitzschia glacialis sp. nov.—alongside the previously described species P. subcurvata, P. turgiduloides, and P. turgidula. Toxin assays revealed no detectable levels of domoic acid in P. turgiduloides, P. turgidula, P. meridionalis sp. nov. and P. glacialis sp. nov. Conversely, P. subcurvata was reported in a related study to produce domoic acid and its isomer, isodomoic acid C. These findings emphasize the need for comprehensive research on the phytoplankton of Antarctic waters, which is currently a largely uncharted domain. With the looming threat of climate change, understanding the dynamics of potentially harmful algal populations in this region is becoming increasingly critical
Considerable Uncertainty of Simulated Arctic Temperature Change in the Mid‐Holocene Due To Initial Ocean Perturbation
Get PDFArctic temperature is one of the most uncertain aspects of mid-Holocene (MH) climate change modeling, usually attributed to the different responses of different models to external forcing. However, in this study, we find that significant discrepancies (i.e., the noise is close to the signal in term of climate change) in the MH Arctic temperature changes can occur within the same model and for identical external forcing due to initial ocean condition perturbations. It is shown that initial ocean perturbations can affect the surface energy budget change through the uncertain cloud effect on shortwave radiation in boreal summer. The resulted uncertain change in summer surface heat flux alters the subsequent autumn and winter sea ice and contributes to significant differences in Arctic temperature via sea ice-albedo feedback. This study suggests that internal uncertainty of an individual model is a non-negligible source of overall uncertainty in simulating the MH Arctic temperature change
A comprehensive Earth system model (AWI-ESM2.1) with interactive icebergs: effects on surface and deep-ocean characteristics
Get PDFThe explicit representation of cryospheric components in Earth system models has become more and more important over the last years. However, there are few advanced coupled Earth system models that employ interactive icebergs, and most iceberg model studies focus on iceberg trajectories or ocean surface conditions. Here, we present multi-centennial simulations with a fully coupled Earth system model including interactive icebergs to assess the effects of heat and freshwater fluxes by iceberg melting on deep-ocean characteristics. The icebergs are modeled as Lagrangian point particles and exchange heat and freshwater fluxes with the ocean. They are seeded in the Southern Ocean, following a realistic present-day size distribution. Total calving fluxes and the locations of discharge are derived from an ice sheet model output which allows for implementation in coupled climate-ice sheet models. The simulations show a cooling of up to 0.2ĝ€¯K of deep-ocean water masses in all ocean basins that propagates from the southern high latitudes northward. We also find enhanced deep-water formation in the continental shelf area of the Ross Sea, a process commonly underestimated by current climate models. The vertical stratification is weakened by enhanced sea ice formation and duration due to the cooling effect of iceberg melting, leading to a 10ĝ€¯% reduction of the buoyancy frequency in the Ross Sea. The deep-water formation in this region is increased by up to 10ĝ€¯%. By assessing the effects of heat and freshwater fluxes individually, we find latent heat flux to be the main driver of these water mass changes. The altered freshwater distribution by freshwater fluxes and synergetic effects play only a minor role. Our results emphasize the importance of realistically representing both heat and freshwater fluxes in the high southern latitudes
Mapping Potential Timing of Ice Algal Blooms From Satellite
Get PDFAs Arctic sea ice and its overlying snow cover thin, more light penetrates into the ice and upper ocean, shifting the phenology of algal growth within the bottom of sea ice, with cascading impacts on higher trophic levels of the Arctic marine ecosystem. While field data or autonomous observatories provide direct measurements of the coupled sea ice-algal system, they are limited in space and time. Satellite observations of key sea ice variables that control the amount of light penetrating through sea ice offer the possibility to map the under-ice light field across the entire Arctic basin. This study provides the first satellite-based estimates of potential sea ice-associated algal bloom onset dates since the launch of CryoSat-2 and explores how a changing snowpack may have shifted bloom onset timings over the last four decades
Bioregionalization of the subarctic Pacific based on phytoplankton phenology and composition
Get PDFThe subarctic Pacific is generally perceived as relatively homogeneous since the North Pacific Subpolar Gyre
dominates the water circulation in the area. However, previous research showed significant spatial differences in
phytoplankton abundance and community structure. This study aimed to identify regions associated with distinct
phytoplankton phenology and composition to comprehensively describe the main phytoplankton variability
patterns across the subarctic Pacific. To this end, satellite GlobColour time series observations and an extensive in
situ phytoplankton pigment dataset were used in the analysis. Five bioregions were identified, based on the Self-
Organized Mapping technique, using a greater than 20-year satellite data series. The bioregions in the open
Pacific waters were dominated by green algae, haptophytes, and pelagophytes and were divided into the areas
affected by the North Pacific Transition Zone and beyond. The other bioregions were defined around the Pacific
basin margins where the diatom contribution was generally higher, with a particular distinction of waters surrounding
the Kuril and the Aleutian Islands. Our bioregion designations allow for future evaluation of the
processes controlling the physical and biological dynamics within each bioregion, which has direct implications
for foraging conditions available to higher trophic levels, including potential food resource competition