Alfred Wegener Institute for Polar and Marine Research
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Mobility census for monitoring rapid urban development
Get PDFMonitoring urban structure and development requires high-quality data at high spatio-temporal resolution. While traditional censuses have provided foundational insights into demographic and socio-economic aspects of urban life, their pace may not always align with the pace of urban development. To complement these traditional methods, we explore the potential of analysing alternative big-data sources, such as human mobility data. However, these often noisy and unstructured big data pose new challenges. Here, we propose a method to extract meaningful explanatory variables and classifications from such data. Using movement data from Beijing, which are produced as a by-product of mobile communication, we show that meaningful features can be extracted, revealing, for example, the emergence and absorption of subcentres. This method allows the analysis of urban dynamics at a high-spatial resolution (here 500 m) and near real-time frequency, and high computational efficiency, which is especially suitable for tracing event-driven mobility changes and their impact on urban structures
Modern microbiology: Embracing complexity through integration across scales
Get PDFMicrobes were the only form of life on Earth for most of its history, and they still account for the vast majority of life's diversity. They convert rocks to soil, produce much of the oxygen we breathe, remediate our sewage, and sustain agriculture. Microbes are vital to planetary health as they maintain biogeochemical cycles that produce and consume major greenhouse gases and support large food webs. Modern microbiologists analyze nucleic acids, proteins, and metabolites; leverage sophisticated genetic tools, software, and bioinformatic algorithms; and process and integrate complex and heterogeneous datasets so that microbial systems may be harnessed to address contemporary challenges in health, the environment, and basic science. Here, we consider an inevitably incomplete list of emergent themes in our discipline and highlight those that we recognize as the archetypes of its modern era that aim to address the most pressing problems of the 21st century
Metatranscriptomic response of deep ocean microbial populations to infusions of oil and/or synthetic chemical dispersant
Get PDFOil spills are a frequent perturbation to the marine environment that has rapid and significant impacts on the local microbiome. Previous studies have shown that exposure to synthetic dispersant alone did not enhance heterotrophic microbial activity or oxidation rates of specific hydrocarbon components but increased the abundance of some taxa (e.g., Colwellia). In contrast, exposure to oil, but not dispersants, increased the abundance of other taxa (e.g., Marinobacter) and stimulated hydrocarbon oxidation rates. Here, we advance these findings by interpreting metatranscriptomic data from this experiment to explore how and why specific components of the microbial community responded to distinct organic carbon exposure regimes. Dispersant alone was selected for a unique community and for dominant organisms that reflected treatment- and time-dependent responses. Dispersant amendment also led to diverging functional profiles among the different treatments. Similarly, oil alone was selected for a community that was distinct from treatments amended with dispersants. The presence of oil and dispersants with added nutrients led to substantial differences in microbial responses, likely suggesting increased fitness driven by the presence of additional inorganic nutrients. The oil-only additions led to a marked increase in the expression of phages, prophages, transposable elements, and plasmids (PPTEPs), suggesting that aspects of microbial community response to oil are driven by the “mobilome,” potentially through viral-associated regulation of metabolic pathways in ciliates and flagellates that would otherwise throttle the microbial community through grazing
Ocean Alkalinity Enhancement in Deep Water Formation Regions Under Low and High Emission Pathways
Get PDFOcean Alkalinity Enhancement (OAE) is an ocean‐based Carbon Dioxide Removal (CDR) method to mitigate climate change. Studies to characterize regional differences in OAE efficiencies and biogeochemical effects are still sparse. As subduction regions play a pivotal role for anthropogenic carbon uptake and centennial storage, we here evaluate OAE efficiencies in the subduction regions of the Southern Ocean, the Northwest Atlantic, and the Norwegian‐Barents Sea region. Using the ocean biogeochemistry model FESOM2.1‐REcoM3, we simulate continuous OAE globally and in the subduction regions under high (SSP3‐ 7.0) and low (SSP1‐2.6) emission scenarios. The OAE efficiency calculated by two different metrics is higher (by 8%–30%) for SSP3‐7.0 than for SSP1‐2.6 due to a lower buffer factor in a high‐CO2 world. All subduction regions show a CDR potential (0.23–0.31; PgC CO2 uptake per Pg alkaline material) consistent with global OAE for both emission scenarios. Calculating the efficiency as the ratio of excess dissolved inorganic carbon (DIC) to excess alkalinity shows that the Southern Ocean and the Northwest Atlantic are as efficient as the global ocean (0.79–0.85), while the Norwegian‐Barents Sea region has a lower efficiency (0.65–0.75). The subduction regions store a fraction of excess carbon below 1 km that is 1.9 times higher than the global ocean. The excess surface alkalinity and thus CO2 uptake and storage follow the mixed‐layer depth seasonality, with the majority of the excess CO2 flux occurring in summer at shallow mixed layer depths. This study therefore highlights that subduction regions can be efficient for OAE if optimal deployment strategies are developed
Sea ice mass balance during the MOSAiC drift experiment: Results from manual ice and snow thickness gauges
Get PDFPrecise measurements of Arctic sea ice mass balance are necessary to understand the rapidly changing sea ice cover and its representation in climate models. During the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, we made repeat point measurements of snow and ice thickness on primarily level first- and second-year ice (FYI, SYI) using ablation stakes and ice thickness gauges. This technique enabled us to distinguish surface and bottom (basal) melt and characterize the importance of oceanic versus atmospheric forcing. We also evaluated the time series of ice growth and melt in the context of other MOSAiC observations and historical mass balance observations from the Surface Heat Budget of the Arctic (SHEBA) campaign and the North Pole Environmental Observatory (NPEO). Despite similar freezing degree days, average ice growth at MOSAiC was greater on FYI (1.67 m) and SYI (1.23 m) than at SHEBA (1.45 m, 0.53 m), due in part to initially thinner ice and snow conditions on MOSAiC. Our estimates of effective snow thermal conductivity, which agree with SHEBA results and other MOSAiC observations, are unlikely to explain the difference. On MOSAiC, FYI grew more and faster than SYI, demonstrating a feedback loop that acts to increase ice production after multi-year ice loss. Surface melt on MOSAiC (mean of 0.50 m) was greater than at NPEO (0.18 m), with considerable spatial variability that correlated with surface albedo variability. Basal melt was relatively small (mean of 0.12 m), and higher than NPEO observations (0.07 m). Finally, we present observations showing that false bottoms reduced basal melt rates in some FYI cases, in agreement with other observations at MOSAiC. These detailed mass balance observations will allow further investigation into connections between the carefully observed surface energy budget, ocean heat fluxes, sea ice, and ecosystem at MOSAiC and during other campaigns
The Impact of Recent Climate Change on the Global Ocean Carbon Sink
Get PDFIn recent decades, the ocean CO2 uptake has increased in response to rising atmospheric CO2. Yet, physical climate change also affects the ocean CO2 uptake, but magnitude and driving processes are poorly understood. Using a global ocean biogeochemistry model, we find that without climate change, the mean carbon uptake 2000–2019 would have been 13% higher and the trend 1958–2019 would have been 27% higher. Changes in wind are the dominant driver of the climate effect on CO2 uptake as they affect advective carbon transport and mixing, but the effect of warming increases over time. Roughly half of the globally integrated wind-driven trend stems from the subpolar Southern Ocean and polar oceans in both hemispheres. Warming reduces the solubility of CO2 and acts rather homogeneously over the world oceans. However, the warming effect on pCO2 is dampened by limited exchange of surface and deep waters
Long-term changes in spatiotemporal distribution of Noctiluca scintillans in the southern North Sea
Get PDFTo assess the spatiotemporal evolution of the heterotrophic dinoflagellate Noctiluca scintillans in the North Sea, the Helgoland Roads time series and Continuous Plankton Recorder survey were analysed using generalized additive models. Over the last decades, blooms of N. scintillans have occurred more frequently and intensively in many regions. This harmful algal bloom forming species can alter food webs, reduce ecosystem productivity, and lead to economic losses while causing lower aquacultural yields. After the 1990s, N. scintillans abundances have significantly increased by 1.65-fold and a significant prolongation of the bloom window was found (from 27.5 to 98 days in recent decades) off the island of Helgoland, Germany. Significant correlations were found between bloom initiation and nutrients, as well as light availability since these factors lead to increased prey availability. Highest abundances of N. scintillans were associated with water temperatures around 17 °C and wind speed below 6 ms−1 causing dense surface accumulations. Solar radiation of more than 200 Wm−2 was identified as a main driver for post-bloom conditions as it can deteriorate the cells and lead to the decline of N. scintillans abundances. In the southern North Sea, N. scintillans occurrences have intensified and spread since the 1980s with hotspots identified as the coastal waters adjacent to the estuaries of the Elbe and Rhine rivers
Constraining the trend in the ocean CO2 sink during 2000–2022
Get PDFThe ocean will ultimately store most of the CO2 emitted to the atmosphere by human activities. Despite its importance, estimates of the 2000−2022 trend in the ocean CO2 sink differ by a factor of two between observation-based products and process-based models. Here we address this discrepancy using a hybrid approach that preserves the consistency of known processes but constrains the outcome using observations. We show that the hybrid approach reproduces the stagnation of the ocean CO2 sink in the 1990s and its reinvigoration in the 2000s suggested by observation-based products and matches their amplitude. It suggests that process-based models underestimate the amplitude of the decadal variability in the ocean CO2 sink, but that observation-based products on average overestimate the decadal trend in the 2010s. The hybrid approach constrains the 2000−2022 trend in the ocean CO2 sink to 0.42 ± 0.06 Pg C yr−1 decade−1, and by inference the total land CO2 sink to 0.28 ± 0.13 Pg C yr−1 decade−1
Population and clonal structure of Acropora cf. hyacinthus to inform coral restoration practices on the Great Barrier Reef
No full textAbstractA key goal of coral restoration is to re-establish self-sustaining coral populations and ensure resilience to future stressors, which requires that genetic diversity is maximised. However, coral genetic and genotypic (clonal) diversity is variable across reef sites via success of sexual recruitment, and cryptic species diversity can complicate breeding efforts. Assessing genotypic and genetic diversity of colonies to be used in restoration is therefore critical to avoid founder, inbreeding or outbreeding effects. Considering recent efforts to upscale coral propagation on the Great Barrier Reef (GBR), we examined species, population and clonal structure of a commonly out-planted tabular Acropora species—Acropora hyacinthus (Dana, 1864). A total of 189 colonies were sampled from six reef systems throughout the northern-central GBR and genotyped using an Acropora-specific Affymetrix microarray, which resulted in 1387 variant sites that passed quality control. Cryptic species were readily resolved and all sampled A. hyacinthus colonies represented unique genotypes within sites at three reefs. At reefs that contained multi-ramet genets (clonal genotypes), the mean and maximum between-ramet distances were 0.68 and 1.99 m, respectively. Therefore, sampling colonies > 2 m apart increases the likelihood these colonies represent distinct genets. Such a sampling design therefore maximises genotypic diversity when sourcing colonies for propagation and out-planting. Based on these variant sites, we found no between-reef genetic divergence based on locality. Furthermore, through unintentional sampling of non-target tabular Acroporid species, we show how this genotyping method may be used for resolving taxonomic uncertainty as well as population dynamics.</jats:p