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Emulating long-term CMIP6 projections of sterodynamic sea-level change using a three-layer energy balance model
No full textMulti-century projections of sea-level change are crucial for understanding long-term climate impacts. However, projecting ocean dynamic processes affecting sea-level change faces two main challenges: (1) the ocean’s thermal inertia and dynamics can lead to substantial nonlinearities both on a global (thermal expansion) and regional scale (dynamic sea level); and (2) simulating ocean dynamic sea-level change over multiple centuries with global climate models is computationally intensive. To address these challenges, we use an energy balance model (EBM) to emulate the thermal responses of models participating in the Coupled Model Intercomparison Project 6 (CMIP6) and evaluate its optimal layer configuration for reproducing both thermal expansion and dynamic sea-level change. We compare results between a two and a three-layer EBM configuration, as fitting more than three layers can lead to EBM parameter overfitting. We find that both configurations perform similarly when emulating thermal expansion, with performance being highly dependent on accurate EBM forcing. To emulate dynamic sea level, we couple the EBM to a multivariate pattern scaling approach that relates the response of layer temperatures to regional changes in dynamic sea level. The latter demonstrates clear advantages of a three-layer configuration under high-emission scenarios, leading to an 18% reduction in emulator error at 2300 while capturing nonlinearities more effectively. Coupling the regional emulator with a simple climate model to propagate climate uncertainties further highlights the advantage of using a three-layer approach, leading to more stable parameter fitting and reducing uncertainty in probabilistic projection by up to one global mean standard deviation. Our findings suggest that multi-layer EBMs can more accurately mimic long-term (up to 2300) CMIP6 projections of sterodynamic sea-level changes while limiting computational burden and reducing uncertainty in emulators due to statistical fitting.</span
The importance of inland water CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>O for summertime greenhouse gas exchange with the atmosphere in Arctic tundra lowlands
No full textInland waters in Arctic landscapes act as conduits of terrestrial organic material, transporting and processing organic material into the greenhouse gases (GHGs) carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and subsequently exchanging these gases with the atmosphere. To assess the role of inland water emissions in the Arctic GHG budget, it is necessary to quantify their emissions in relation to the terrestrial sink capacity. We present measurements of dissolved CO2, CH4, and N2O from lake, pond, and low-order fluvial systems across two summers (2016–2017) in the Arctic Siberian Indigirka River tundra lowlands. During May–July 2017, the region experienced large-scale flooding, of which we captured the tail end. Using remote sensing images to upscale inland water emissions to an area of approximately 18 km2, we calculated combined carbon (C) emissions, CO2-C, and diffusive CH4-C under nonflood and flooded scenarios. These ranged from 7.03 ± 1.30 Mg C d−1 (nonflood; mean ± SD) to 9.63 ± 1.24 Mg C d−1 (flooded). Integrating these values into the total C landscape exchange offset the terrestrial C sink by ∼9–∼13%. When N2O emissions were calculated as CO2 equivalents, these emissions were negligible relative to CO2 and CH4. Our study shows that in the northeast Siberian Arctic tundra, summertime CO2 and CH4 emissions from inland waters are a potentially important component of landscape C exchange with the atmosphere, offsetting the terrestrial sink capacity, and this may be an important consideration for constraining future Arctic responses to climate warming.</span
Using photorealistic 3D visualization to convey ecosystem restoration to the public
No full textThe success of climate adaptation and nature conservation measures depends significantly on public support. Although the value of protecting iconic species is often easy to communicate to non-expert audiences, conveying the broader importance of ecosystem restoration and conservation for climate resilience is more challenging. To address this, we developed a method that combines spatially explicit models of complex, self-organizing ecosystems with state-of-the-art visualization techniques. This approach creates immersive, three-dimensional panoramic views of natural landscapes, illustrating how people live in and interact with these ecosystems. Our method showcases the inherent complexity of ecosystems, highlighting features such as spatial patterning and the dynamic processes that shape them, as well as the critical role of this complexity in supporting biodiversity. Additionally, it demonstrates the potential of restored or even constructed ecosystems as nature-based solutions to future climate challenges. Adaptable to various ecosystems and locations, with the optional addition of audio or text explanations, this visualization tool can be used in diverse contexts, from museum exhibits to on-site virtual experiences, effectively reaching broad audiences. We present our visualization approach through two case studies that bring to life past climate-adaptive ecosystems and envision future developments. The first case depicts a historic medieval village, now located within a low-lying polder, which was once founded on an expansive, climate-resilient marsh that naturally rose with sea levels due to continuous sediment deposition. The second case explores a planned nature restoration project in Biesbosch National Park, where an embanked meadow is planned to be converted into a tidal wetland
Natronomicrosphaera hydrolytica, gen. nov., sp. nov., a first representative of the phylum Planctomycetota from soda lakes
No full textDespite intensive microbiological characterization of soda lake microbial communities, no culturable representatives from the phylum Planctomycetota have been isolated from these haloalkaline habitats. In the context of studying polysaccharide utilization by soda lake microbial communities, we used polysaccharide hyaluronic acid as enrichment substrate at aerobic, moderate haloalkaline conditions (1 M total Na+, pH 9.5). This resulted in a selective enrichment and isolation in pure culture of a bacterial strain AB-hyl4 belonging to Planctomycetota. The cells are tiny motile cocci growing in large aggregates, with the Gram-negative type of ultrastructure and producing a yellow pigment. This obligate aerobic saccharolytic heterotroph has an extremely narrow growth substrate range including, besides hyaluronic acid, melezitose and glycerol. The membrane lipids consist of phosphatidylcholine and two types of neutral lipids, including hopanoids and monounsaturated C17 and C19 hydrocarbons. Phylogenomic analysis placed the isolate into the family Phycisphaeraceae, class Phycisphaerae, as a new genus-level lineage. Its genome contained a gene encoding a polysaccharide lyase from the PL8 family which is probably responsible for the degradation of hyaluronic acid to a dimer, followed by its transport and hydrolysis into monomers in periplasm and final glycolytic degradation in cytoplasm. On the basis of distinct phenotypic and genomic properties, strain AB-hyl4T (DSM 117794 = UQM 41914) is proposed to be classified as Natronomicrosphaera hydrolytica gen. nov., sp. nov.</span
Open or closed: pH modulation and calcification by foraminifera
No full textMarine calcifying organisms precipitate their shells either in equilibrium with seawater or under strict biological control. Here, we show that these two options represent two ends of a spectrum. In species with a more “closed” system, rates of H+ removal and Ca2+ uptake are high and exceed the amount of ions required for calcification. This explains the relatively low Mg/Ca of the calcite of this species by dilution of the [Mg2+] in the calcifying fluid. Conversely, in species with a more open system, the H+ and Ca2+ fluxes are lower, with more seawater exchanged between the environment and calcifying fluid, explaining the relatively high Mg/Ca in these foraminifera. In either of these species, mitochondria were found to be located at the site where the Ca2+/H+ exchange takes place and the mitochondrial density aligned with the rate of pumping. These findings highlight the crucial role of transmembrane transporters and mitochondria in foraminifera calcification and explain the species-specific elemental signatures.</span
Seasonal coastal residency and large-scale migration of two grey mullet species in temperate European waters
No full textGrey mullets (family Mugilidae) are widespread across coastal, brackish, and freshwater habitats, and have supported fisheries for millennia. Despite their global distribution and commercial value, little is known about their movement ecology and its role in the co-existence of sympatric mullet species. Gaps in knowledge about migratory behaviour, seasonal occurrence, and movement scales have also impeded effective management, highlighting the need for further research. This study aimed to identify key habitats and timing of grey mullet presence across the Dutch Wadden Sea, North Sea, and freshwater areas, and to explore potential behavioral differences between two grey mullet species: thicklip mullet (Chelon labrosus) and thinlip mullet (Chelon ramada). Using acoustic telemetry, we tracked 86 tagged grey mullet over three years (thicklip mullet, N = 74; thinlip mullet, N = 12), combining data from 100 local acoustic receivers and the European Tracking Network. Both species were detected in the Wadden Sea from April to November, however, thinlip mullet arrived in the Wadden Sea earlier than thicklip mullet (median date = May 16 vs. June 7). Individual residency in the Wadden Sea lasted a median 97 days for thicklip mullet and 94 days for thinlip mullet. Thinlip mullet were also detected by more receivers and over a larger area than thicklip mullet, indicating differences in movement behaviour. Both species showed an affinity for receivers near major harbours, with thinlip mullet more often detected near fresh water outflows. Seasonal migrations between coastal and offshore waters were also observed, with one thinlip mullet returning to freshwater across consecutive years. North Sea detections spanned ten months, with a gap during the presumed spawning period (Jan–Feb). Our data suggest that thinlip mullet show a preference for deeper gullies while thicklip mullet may spend more time in shallow areas and flooded tidal flats. These findings highlight the importance of the Wadden Sea as a seasonal foraging ground and provide insights into the migratory patterns of grey mullets
High-resolution sedimentary record in the eastern Mediterranean shelf shows reduced Nile-derived mud after the Little Ice Age (1830 CE)
No full textChemical, sedimentological and micropaleontological records were used to track recent climatic and ecological events recorded in eastern Mediterranean shelf sediments. By studying a high-resolution record of well-dated sediment from the Israeli shelf, natural and anthropogenic influence during the past 270 years were differentiated and pinpointed to major events.The most prominent changes occurred in sediment source at the end of the Little Ice Age (LIA), in 1830–1840 CE. Coarse, quartzose sand comprised only 5% of the sediment during the LIA, and increased significantly after the LIA to levels of up to 15%. There was a further increase in the coarse, quartzose content to >20% following the damming of the Nile River (Aswan High Dam, in 1964), continuing the earlier post-LIA increase.The geochemical data suggests a shift in the composition of the finer-grained sediments at the end of the LIA. During the LIA, clay-rich sediments were found to have lower levels of K2O and higher levels of Ni compared to sediments post-LIA. These likely indicate a change in the source of sediments to the eastern Mediterranean shelf, shifting from a dominance of Nile-derived sediments and Nile Delta soils during the LIA, to more Saharan-derived, fine-grained dust and coarse-grained quartzose sands in the post-LIA period. The prevalence of Nile-derived sediments during the LIA suggests wetter conditions in coastal East Africa during that time period, as opposed to post-LIA.The foraminiferal data also indicate a shift at the end of the LIA, mainly in group composition and abundance. A major increase in miliolid shell-type abundances after the LIA, aligns with a transition to warmer temperatures post-LIA. An additional increase is detected in species richness and abundance after the damming of the Nile River. However, this is superimposed on the ongoing increase since the LIA termination
Validation of mollies and gilthead seabreams as new model organisms for the study of anisakids: Experimental infection and histological analysis of the infective process in sailfin molly
No full textThis study aims to propose new fish model organisms for experimental studies on anisakis and other fish pathogens as alternatives to the commonly used fish model Danio rerio (Hamilton, 1822). For this purpose, the sailfin molly (Poecilia latipinna (Lesueur, 1821)) and the gilthead seabream (Sparus aurata Linnaeus, 1758) were tested by experimental infections with Anisakis simplex s.l. larvae. Preliminary susceptibility challenges on mollies showed successful infections, with larvae observed up to 384 h post-infection (hpi). Histological analysis showed encapsulation of larvae and mild tissue damage in the infected fish, providing insight into the infection process. Two infection methods, oral ingestion and orogastric inoculation, were tested in both fish species. The results indicate successful infections with both methods, with higher prevalence and recovery rates observed with orogastric inoculation (especially in gilthead seabream). In addition, the study examined the chronology of the infective process, histological changes, and encapsulation patterns in infected fish. This comprehensive study highlights the suitability of sailfin molly as a model organism for experimental studies on anisakid infections and provides valuable insights into infection dynamics and host-parasite interactions. Further research in this area could contribute to the development of effective prevention and control measures for anisakid infections, and thus reduce the health risks associated with fish consumption.</span
Plant species, inundation, and sediment grain size control the development of sediment stability in tidal marshes
No full textTidal marshes can contribute to nature-based shoreline protection by reducing the wave load onto the shore and reducing the erosion of the sediment bed. To implement such nature-based shoreline erosion protection requires the ability to quickly restore or create highly stable and erosion-resistant tidal marshes at places where they currently do not yet occur. Therefore, we aim to identify the drivers controlling the rate by which sediment stability builds up in young pioneer marshes. Sediment stability proxies were measured over age gradients spanning 18 years in six tidal marsh sites in the Western Scheldt estuary (SW Netherlands): Three were dominated by Spartina anglica, a densely growing pioneer species, and three by Scirpus maritimus, a less densely growing pioneer species. Our results showed that the presence of densely growing Spartina anglica increased sediment shear strength compared to the unvegetated tidal flat, while less densely growing Scirpus maritimus did not. This difference may be related to the contrasting clonal expansion strategies and related root densities of these two pioneer species. Sediment stability did not increase further beyond 6 years of coverage by Spartina anglica, implying that the observed effect of Spartina anglica on sediment stability occurs fast (<6 years). Furthermore, sediment stability often increased with decreasing inundation duration and sediment water content. This study shows that in order to create erosion-resistant sediment beds in future marsh restoration projects, the aim should be to create densely vegetated tidal marshes with well-draining, cohesive sediments at relatively high intertidal elevation. Although the development of erosion resistance takes time, our study demonstrates that in the case of densely growing Spartina anglica marshes, increased sediment bed stability can already be reached after 6 years. The ability of Spartina anglica marshes to increase sediment bed stability within 6 years, in combination with wave attenuation and sediment accretion, offers promising perspectives to implement marsh restoration projects as a nature-based shoreline protection strategy that can start to deliver its protective service within a reasonable amount of time.</span