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A novel quinone biosynthetic pathway illuminates the evolution of aerobic metabolism
No full textThe dominant organisms in modern oxic ecosystems rely on respiratory quinones with high redox potential (HPQs) for electron transport in aerobic respiration and photosynthesis. The diversification of quinones, from low redox potential (LPQ) in anaerobes to HPQs in aerobes, is assumed to have followed Earth's surface oxygenation similar to 2.3 billion years ago. However, the evolutionary origins of HPQs remain unresolved. Here, we characterize the structure and biosynthetic pathway of an ancestral HPQ, methylplastoquinone (mPQ), that is unique to bacteria of the phylum Nitrospirota. mPQ is structurally related to the two previously known HPQs, plastoquinone from Cyanobacteriota/chloroplasts and ubiquinone from Pseudomonadota/mitochondria, respectively. We demonstrate a common origin of the three HPQ biosynthetic pathways that predates the emergence of Nitrospirota, Cyanobacteriota, and Pseudomonadota. An ancestral HPQ biosynthetic pathway evolved >= 3.4 billion years ago in an extinct lineage and was laterally transferred to these three phyla similar to 2.5 to 3.2 billion years ago. We show that Cyanobacteriota and Pseudomonadota were ancestrally aerobic and thus propose that aerobic metabolism using HPQs significantly predates Earth's surface oxygenation. Two of the three HPQ pathways were later obtained by eukaryotes through endosymbiosis forming chloroplasts and mitochondria, enabling their rise to dominance in modern oxic ecosystems
Surface area and Ω-aragonite oversaturation as controls of the runaway precipitation process in ocean alkalinity enhancement
No full textOcean alkalinity enhancement (OAE) is a strategy for marine carbon dioxide removal that aims to increase the total alkalinity (TA) of seawater to sequester atmospheric CO2 in the form of dissolved inorganic carbon (DIC). An intense alkalinization of seawater resulting from OAE treatment could trigger a significant runaway carbonate precipitation process, which may lead to a loss of initially added alkalinity, thereby limiting its efficiency. Even under natural background aragonite saturation states, a continuous yet barely detectable loss of alkalinity is theoretically expected to occur in seawater. With the additional increase through OAE, time ranges to initiate an appreciable TA loss process could be reduced significantly. Therefore, predicting the alkalinity stability ranges might be a necessity for application scenarios. The main drivers of the precipitation process are i) the aragonite saturation state of seawater and ii) the available surface area for heterogeneous precipitation.
In this study, we refined the use of logistic functions to describe the temporal evolution of both drivers, with experimental datasets using natural seawater from the Raunefjorden (Bergen, Norway; Temp.: ~11 °C, Sal.: ~32.6). The observed patterns were then used to derive a process-based model for calculating TA-loss rates, focusing on the accelerated precipitation phase of the runaway process while considering saturation levels and available particle surface area. The formation of carbonate phases reduces seawater TA concentrations, inducing a delay or stopping the TA-loss process. In addition, the sinking of precipitated particles decreases the potential for further precipitation by reducing the available surface area in the system. To assess the impact of particle sinking on TA-loss, their shape and size distribution were determined. Under the environmental conditions presented here, TA-loss rates could be reduced by up to 30–40 % due to the sinking of particles, after just one day.
Integrating the proposed concepts into ocean models could enhance the accuracy of predictions regarding the fate of added alkalinity. Gaining insights into the evolution of the identified, seemingly stable TA levels can help prevent accelerated precipitation phases. Additionally, an understanding of particle sinking or dilution processes reducing the available reactive particle surface area is relevant to assess the efficacy and durability of OAE
Formation conditions of coastal palaeolakes and associated abiotic aragonite deposition in the eastern Mediterranean during the upper Pleistocene
No full textHighlights
• The western Saronikos Gulf during the last ∼44.5 kyr BP was twice connected to the Aegean Sea; in between it was a palaeolake.
• During the lacustrine period, the deposition of abiotic aragonite through evaporative processes was predominant.
• The deposition of aragonite was facilitated by the low lake water temperatures, ranging from 5 to 10 °C.
• During the lacustrine period, sedimentation rates were 2-fold or higher than at typical marine conditions.
During the Last Glacial Period (LGP), when sea level was up to ∼130 m lower than today, many of the currently semi-enclosed gulfs in the Eastern Mediterranean were isolated from the open sea, functioning as palaeolakes. This was the case for the western Saronikos Gulf in Greece, which was isolated from the Aegean Sea. The palaeogeographic evolution of this area was investigated by analyzing a 350 cm sediment core for grain size, inorganic geochemistry, mineralogy, and bulk δ13C and δ18O compositions. An age model was developed by combining radiocarbon (14C) and uranium-thorium (U/Th) dating methods. Integrating all available data and accounting for eustatic sea-level fluctuations, the sedimentary units of core SARC-18 cover the last glacial-interglacial cycle, spanning from 44.5 kyr BP to the present. Two marine sedimentation intervals were identified, characterized by clay minerals, biogenic calcite, and light δ13C and δ18O isotopic signatures. These intervals are separated by a lacustrine sedimentation phase, marked by the exclusive deposition of authigenic aragonite and a significant enrichment in δ13C and δ18O. The latter elevated δ13C and δ18O values suggest carbonate mineral formation in an evaporative and saline environment under low temperatures (5–10 °C). Sedimentation rates during the marine intervals range from 5.8 to 6.0 cm kyr⁻1, and are more than double during the lacustrine interval (11.9–14.0 cm kyr⁻1) due to the extensive deposition of authigenic aragonite
ERC Data Management Plan - WHIRLS
No full textThis document describes the Data Management Plan (DMP) of the WHIRLS project in alliance with the project specific Research Data Policy. It aims to describe which data types will be collected and generated during the project and how the compliance to FAIR and open research will be granted. The format of the DMP follows the guidelines suggested for Horizon Europe projects. The DMP is intend to be a living document and will be regularly updated, as a minimum in the context of the periodic evaluation/assessment of the project
Assessing the invasion risk of the cnidaria Blackfordia virginica Mayer, 1910: a threat to the Baltic Sea ecosystem?
No full textThe ecological role, bloom extent and long-term dynamics of jellyfishes are mostly overlooked due to sampling limitations, leading to the lack of continuous long-term datasets. A rise in frequency and magnitude of jellyfish invasion around the world is shedding new light on these organisms. In this study, we estimate the current and future distribution of the introduced jellyfish Blackfordia virginica in the Baltic Sea. We determine the combination of favorable levels of temperature and salinity for this species by analyzing presence/absence data from areas outside the Baltic Sea and project the distribution of suitable habitat in the Baltic Sea across different scenarios with variable climate forcing and eutrophication levels. Our results show that suitability increases with rising temperature and optimal salinity range from 13 to 20 for this species. In addition, a relatively large area of the Baltic Sea represents favorable abiotic conditions for B. virginica, enhancing the concerns on its potential range expansion. Spatial analysis illustrates that the coastal areas of the southern Baltic Sea are particularly at risk for the invasion of the species. The observation of the projection of habitat suitability across time highlights that future Baltic Sea environmental conditions increase suitability levels for B. virginica and suggest a potential expansion of its distribution in the future
Teilweise dünn wie Löschpapier
No full textErschrekende Entwicklung in der Eckernförder Bucht: Dorschbestand bricht zusammen, Plattfische immer schmaler
Diverse lifestyles and adaptive evolution of uncultured UBA5794 actinobacteria, a sister order of “Candidatus actinomarinales”
No full textUncultured UBA5794 actinobacteria are frequently found in marine and inland water environments by using metagenomic approaches. However, knowledge about these actinobacteria is limited, hindering their isolation and cultivation, and they are always confused with "Candidatus Actinomarinales" based on 16S rRNA gene classification. Here, to conduct genomic characterization of them, we obtained three high-quality UBA5794 metagenome-assembled genomes (MAGs) from a hydrothermal sediment on the Carlsberg Ridge (CR) and retrieved 131 high-quality UBA5794 genomes from public datasets. Phylogenomic analysis confirms UBA5794 as an independent order within the class Acidimicrobiia. Genome-based metabolic predictions reveal that flexible metabolism and diversified energy acquisition, as well as heavy metal(loid) detoxification capacity, are crucial for the ability of UBA5794 to thrive in diverse environments. Moreover, there is separation between sponge-associated and free-living UBA5794 groups in phylogeny and functional potential, which can be attributed to the symbiotic nature of the sponge-associated group and the extensive horizontal gene transfer (HGT) events observed in these bacteria. Ancestral state reconstruction suggests that the UBA5794 clade may have originated from a free-living environment and then some members gradually migrated to the sponge host. Overall, our study sheds light on the ecological adaptation and evolutionary history of the ubiquitous but poorly understood UBA5794 actinobacteria
Land conversions not climate effects are the dominant indirect consequence of sun-driven CO2 capture, conversion, and sequestration
No full textRemoving carbon dioxide (CO2) from the atmosphere is required for mitigating climate change. Large-scale direct air capture combined with injecting CO2 into geological formations could retain carbon long-term, but demands a substantial amount of energy, pipeline infrastructure, and suitable sites for gaseous storage. Here, we study Earth system impacts of modular, sun-powered process chains, which combine direct air capture with (electro)chemical conversion of the captured CO2 into liquid or solid sink products and subsequent product storage (sDACCCS). Drawing on a novel explicit representation of CO2 removal in a state-of-the-art Earth system model, we find that these process chains can be renewably powered and have minimal implications for the climate and carbon cycle. However, to stabilize the planetary temperature two degrees above pre-industrial levels, CO2 capturing, conversion, and associated energy harvest demand up to 0.46% of the global land area in a high-efficiency scenario. This global land footprint increases to 2.82% when assuming present-day technology and pushing to the bounds of removal. Mitigating historical emission burdens within individual countries in this high-removal scenario requires converting an area equivalent to 40% of the European Union's agricultural land. Scenarios assuming successful technological development could halve this environmental burden, but it is uncertain to what degree they could materialize. Therefore, ambitious decarbonization is vital to reduce the risk of land use conflicts if efficiencies remain lower than expected
Atmospheric and Oceanic Pathways Drive Separate Modes of Southern Hemisphere Climate in Simulations of Spontaneous Dansgaard‐Oeschger‐Type Oscillations
No full textDansgaard-Oeschger (DO) events are a dominant mode of millennial-scale climate variability during the last glacial period with most pronounced impacts in the North Atlantic region. In Antarctica, they manifest primarily as a muted and phase-shifted temperature signal, but recent studies suggest an additional in-phase component. Here, we analyze the Southern Hemisphere (SH) response to spontaneous DO-type oscillations in a general circulation model. The dominant Antarctic temperature mode is phase-shifted compared to Greenland temperature variations and consistent with the oceanic pathway described by the bipolar seesaw model. However, the leading SH atmospheric circulation mode varies synchronously with Greenland temperatures. A westward-shifted Walker circulation and strengthened Hadley cell during Greenland temperature maxima cause zonally heterogeneous jet stream anomalies differing from the Southern Annular Mode pattern. Comparison of simulated O with speleothems and ice cores indicates a good agreement in the tropics and SH mid-latitudes but deviations in Antarctica warrant further research
Prevalent North Atlantic Deep Water during the Last Glacial Maximum and Heinrich Stadial 1
No full textDeep ocean circulation modulated glacial–interglacial climates through feedbacks to the carbon cycle and energy distribution. Past work has suggested that contraction of well-ventilated North Atlantic Deep Water during glacial times facilitated carbon storage in the deep ocean and drawdown of atmospheric CO2 levels. However, the spatial extent and properties of different water masses remain uncertain, in part due to conflicting palaeoceanographic proxy reconstructions. Here we combine five independent proxies to increase confidence and reconstruct Atlantic deep water distributions during the Last Glacial Maximum (around 21 thousand years ago) and the following Heinrich Stadial 1—a time when massive ice rafting in the North Atlantic interfered with deep water formation and caused global climate shifts. We find that North Atlantic Deep Water remained widespread in both periods, although its properties shifted from a cold, well-ventilated mode to a less-ventilated, possibly warmer, mode. This finding implies a remarkable persistence of deep water formation under these cold boundary conditions, sustained by compensation between the two formation modes. Our constraints provide an important benchmark for evaluating Earth system models, which can enhance confidence in future climate projections