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Prey dynamics as a buffer: Enhancing copepod resilience to Ocean Alkalinity Enhancement
No full textOcean alkalinity enhancement (OAE) aims to counteract climate change by increasing the ocean's carbon storage capacity through the addition of alkaline substances into seawater. However, this process alters seawater chemistry, increasing total alkalinity (TA) and pH, which can directly influence marine organisms’ metabolic activities or indirectly impact them through changes in prey availability and quality. This study disentangled the OAE-driven factors that might influence zooplankton physiology. We assessed the direct effect of altered chemistry on the copepod, Temora longicornis, and the indirect effect through changes in the phytoplankton prey, Rhodomonas salina. We cultured the prey in OAE conditions and used it to feed copepods to investigate the indirect effect. We found that OAE negatively impacted prey growth but improved its nutritional quality, offsetting the direct negative impact of OAE on the copepod. These findings regarding OAE’s impact on prey-predator dynamics contribute to a deeper understanding of how OAE might influence zooplankton communities
Mass accumulation rates decreased in the Skagerrak basin over the last 100 years
No full textHighlights:
• Reconstruction of mass accumulation rates in the Skagerrak
• Mass accumulation rates decreased over the last 100 years
• Decrease is more pronounced when bioturbation is considered in the reconstructions
• Findings of the Skagerrak indicate environmental shifts in the North Sea region
Abstract
Since the 19th century, the North Sea sediment system has been subject to a dynamic hydrographic regime and intense human alteration. The Skagerrak serves as the largest depocenter for suspended sediment originating from the North Sea. Thus, deposits in the Skagerrak provide a historical record of potential shifts in the sediment cycle of the North Sea. Despite the availability of mass accumulation rate (MAR) data in the Skagerrak, previous studies focused on steady-state reconstructions and little is known about how these rates may have changed over time. To address this knowledge gap, we present age-depth models based on the natural radionuclide 210Pb and the anthropogenic time markers 137Cs, fraction modern 14C (F14C) and mercury (Hg) to determine the MAR before and after the year 1963 at six stations in the deep Skagerrak basin between 434 and 677 meters water depth. We applied 1963 as the boundary since this year is constrained by 137Cs and F14C peaks in the sediment cores due to atomic weapons testing and changes in sedimentary Hg contents. Our primary result reveals that the MAR in the deep Skagerrak basin decreased from 0.17 to 0.14 g cm-2 yr-1 averaged across the stations. We further simulate the effect of bioturbation on the solid phase profiles by applying a reaction transport model to the data, revealing that the decline in MAR is more pronounced when bioturbation is considered (from 0.17 to 0.09 g cm-2 yr-1). Decreasing MARs in the Skagerrak basin indicate that the sediment system of the North Sea substantially changed over time. Possible reasons include a shift in the North Sea circulation pattern, enhanced sediment trapping in the Wadden Sea and reduced sediment inputs due to river damming, deepening of harbor channels and coastal protection. However, we stress that our data do not allow for a quantitative analysis of the major driving factors behind the temporal variability of sediment cycling. Hence, we recommend combining our results with information on the provenance of the Skagerrak deposits and integrating the Skagerrak data into larger-scale physical models that consider non-steady state particle transport in the North Sea
Dynamic land-plant carbon sources in marine sediments inferred from ancient DNA
No full textTerrigenous organic matter in marine sediments is considered a significant long-term carbon sink, yet our knowledge regarding its source taxa is severely limited. Here, we leverage land-plant ancient DNA from six globally distributed marine sediment cores covering the Last Glacial–Holocene transition as a proxy for the share, burial rate, preservation, and composition of terrigenous organic matter. We show that the spatial and temporal plant composition as revealed by sedimentary ancient DNA records reflects mainly the vegetation dynamics of nearby continents as revealed by comparison with pollen from land archives. However, we also find indications of a global north-to-south translocation of sedimentary ancient DNA. We also find that plant sedimentary ancient DNA has a higher burial rate in samples from the Late Glacial, which is characterized by high runoff and mineral load. This study provides an approach to understanding the global linkages between the terrestrial and marine carbon cycle, highlighting the need for further research to quantify the processes of DNA preservation and dispersal in marine sediments
Rapid rise in atmospheric CO2 marked the end of the Late Palaeozoic Ice Age
No full textAtmospheric CO 2 is thought to play a fundamental role in Earth’s climate regulation. Yet, for much of Earth’s geological past, atmospheric CO 2 has been poorly constrained, hindering our understanding of transitions between cool and warm climates. Beginning ~370 million years ago in the Late Devonian and ending ~260 million years ago in the Permian, the Late Palaeozoic Ice Age was the last major glaciation preceding the current Late Cenozoic Ice Age and possibly the most intense glaciation witnessed by complex lifeforms. From the onset of the main phase of the Late Palaeozoic Ice Age in the mid-Mississippian ~330 million years ago, the Earth is thought to have sustained glacial conditions, with continental ice accumulating in high to mid-latitudes. Here we present an 80-million-year-long boron isotope record within a proxy framework for robust quantification of CO 2 . Our record reveals that the main phase of the Late Palaeozoic Ice Age glaciation was maintained by prolonged low CO 2 , unprecedented in Earth’s history. About 294 million years ago, atmospheric CO 2 rose abruptly (4-fold), releasing the Earth from its penultimate ice age and transforming the Early Permian into a warmer world
Kohlendioxid-Speicherung im tiefen Untergrund der deutschen Nordsee - Version 5
No full textFactsheet:
Die Speicherung von Kohlendioxid im tiefen Untergrund der Nordsee ist technisch machbar und wird bereits seit Jahrzehnten unter norwegischen Gewässern praktiziert. Unter der deutschen Nordsee existieren ebenfalls Gesteinsformationen, in denen sich vermutlich große Mengen Kohlendioxid speichern ließen. Dennoch bleiben wichtige Fragen offen, die in der Forschungsmission CDRmare adressiert und beantwortet werden sollen – mit dem Ziel, ein Demonstrationsprojekt zur Kohlendioxid-Speicherung im geologischen Untergrund der deutschen Nordsee zu ermöglichen
2. Wochenbericht M207
No full text04.01.-11.02.2025
Belém – Mindelo
2. Wochenbericht 06.01.-12.01.202
Enhanced benthic weathering as a CO2 removal strategy in seasonal hypoxic coastal waters of the Baltic Sea is influenced by cable bacteria activity after re-ventilation of bottom waters
No full textSponge species from New Zealand may transform and degrade dissolved organic matter
No full textHighlights
• Sponges had δ13 org. C/ δ15N values from -17.9 ‰/5.39 ‰ to -19.7 ‰/ 20.9 ‰.
• Sponges released or took up DOC/ TDN, but the fluxes were mostly insignificant.
• FDOM pool contained 4 fluorophores (tryptophan-/ protein-like, humic-like, tyrosine-like).
Sponges are an important component of shallow- and deep-water ecosystems enhancing eukaryotic biodiversity via diverse endo- and epibiota and by providing three dimensional habitats for benthic invertebrates and fishes. Sponge biodiversity is particularly high in the waters around New Zealand (Southwest Pacific), where we collected two shallow- and two deep-water sponge species (Tedania sp., Suberea meandrina, Farrea raoulensis, Artemisina sp.) for ex-situ incubation experiments to measure processing of dissolved organic matter (DOM). Several sponge species take up DOM and make it available to other fauna as detritus or as sponge biomass, a process known as sponge loop. However, it is unknown whether the selected sponge species are able to consume dissolved organic carbon (DOC) and/or total dissolved nitrogen (TDN). We measured DOC and TDN fluxes and linked it to the bacterial communities of the sponge holobiont to address research hypothesis 1. It stated that high-microbial abundance (HMA) sponges consume more DOM than low-microbial abundance (LMA) sponges. Changes in fluorescent dissolved organic matter (FDOM) over time were investigated to address research hypothesis 2. It proposed that the fluorescence intensity Fmax of fluorophores decreased in incubations that showed a significant loss in DOM. We assessed the biochemical and phospholipid-derived fatty acids (PLFAs) composition of sponge tissue to address hypothesis 3. It suggested that the PLFLA composition of sponges differs between sponge classes. Finally, we tried to better understand the role of these sponges in nutrient cycling around New Zealand by combining data from all analyses. Based on the community composition of the sponge-associated bacteria, we classified Tedania sp., S. meandrina, and Artemisina sp. as HMA sponges and F. raoulensis as LMA sponge. We did not measure a significant DOC flux and only the release of TDN by Tedania sp. was significantly different from 0 μmol TDN g org. C-1 d-1. The presence of four fluorophores were detected in the FDOM pool: 2 tryptophan- and protein-like fluorophores (C1, C2), 1 humic-like fluorophore (C3), and 1 tyrosine-like fluorophore (C4). However, we could not validate hypothesis 2, because Fmax of C1 decreased significantly in S. meandrina incubations, whereas Fmax of C2 grew in the same incubations. Fmax of C3 increased in Tedania sp. incubations, in which Fmax of C4 decreased. In comparison, Fmax of C4 in S. meandrina rose. The PLFA composition of sponge tissue was dominated by long-chain fatty acids, saturated fatty acids, and monosaturated fatty acids, and most PLFAs were sponge- and bacteria-specific. We could not confirmed hypothesis 3, either, because the PLFA composition of the hexactinellid sponge included seven identified PLFAs, whereas the PLFA composition of the demosponges ranged from three to 29 identified PLFAs
Food fight: Gammarus tigrinus demonstrate competitive advantage over native G. duebeni
No full textIntroductions of non-native species (NNS) are major drivers of biodiversity loss. Gammarids (Crustacea, Gammaroidea) have been particularly successful in establishing and spreading in their non-native range, especially in Europe. While their impacts are wide-ranging, interference competition with native species has received limited study to date. Here, we assessed the competitive abilities of the successful North American NNS Gammarus tigrinus relative to the European native Gammarus duebeni, over a chironomid larva as a single food resource. We staged four types of dyadic contest encounters, with individuals of the native or NNS added to the experimental arena containing the food resource, and inter- or intraspecific competitor individuals added upon the first individual taking possession of the resource, or after 20 minutes. Gammarus tigrinus were more likely to take hold of the bloodworm in the opening 20 minutes, and did so more quickly than G. duebeni. During this period, they were also less thigmotactic than the native, being more explorative and spending a smaller proportion of time in the outer zone of the arena. They exhibited more aggressive interactions and activity with increasing size and mass, whereas larger G. duebeni were shown to be less aggressive and less active. Gammarus tigrinus were found to be significantly less likely to lose possession to G. duebeni than they were to conspecifics, whereas G. duebeni were similarly likely to lose possession to G. tigrinus as to conspecifics. Overall, our findings indicate that the behaviour and competitive ability of G. tigrinus demonstrated here add to a list of traits that facilitate its invasion success. In addition, our method offers potential as an effective, standardisable means of assessing the competitive abilities of gammarid NNS. We encourage future studies to develop it further, incorporating alternative resources, such as habitat, and to assess the role of ecologically relevant abiotic stressors in determining contest outcomes
Strong potassium uptake in surface sediments of the Changjiang River Estuary and the East China Sea: Implications for authigenic processes and the marine potassium budget
No full textPotassium (K) is a major cation in seawater, but its budget remains not well understood mainly because of the poor constraint on the authigenic clay formation at the seafloor. Marine authigenic phases are assumed to have played a substantial role in balancing the long-term equilibrium of seawater chemistry and regulating Earth's climate. However, the global importance of K-rich authigenic clay minerals for the marine K budget remains poorly quantified. In this study, we report the K content and its spatial variation along the Changjiang (Yangtze) River-Estuary-East China Sea transect, aiming to reveal the influence of authigenic uptake processes on the marine K budget. By combining our new data on the K composition of various sediment and porewater samples with previously published data, we found that the K/Al ratio of the marine particulate matter is substantially higher than that of the riverine endmember, with the averages of 0.31 ± 0.04 and 0.25 ± 0.02, respectively. Based on the observation of decreasing K concentration with depth in porewater and an increasing abundance of green grains (mostly glauconite-like) towards the shelf, we propose that these geochemical changes are caused by the authigenic uptake of K from seawater. Our preliminary calculation suggests that when upscaled to all the river-dominated ocean margins, the global uptake flux of K is approximately 81 ± 62 Tg yr−1, which is comparable in magnitude with the dissolved flux coming from global rivers. Our findings highlight the role of authigenic mineral formation in modifying the geochemistry of seawater and marine sediments