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Maternal, temperature, and seasonal effects on yolk-sac larvae of Atlantic herring Clupea harengus in the western Baltic Sea
No full textIn marine fishes that spawn at specific times of the year, maternal effects interact with seasonal abiotic factors to influence offspring phenotypes that can affect growth, development, and survival of the early life stages. The relative importance of maternal versus abiotic processes throughout ontogeny is unclear. We incubated the progeny of 22 Atlantic herring Clupea harengus females from either early-, mid-, or late-spring spawning periods at both early- (7 °C) and late-season (13 °C) in situ temperatures. After yolk-sac larvae had hatched, changes in yolk sac area, notochord length, body depth, somatic body area, and cases of deformities were tracked until the point-of-no-return (beyond which starvation is irreversible), also allowing somatic growth rate and yolk utilization efficiency to be estimated. We then quantified the contributions of maternal effects, incubation temperature, and seasonal effects on offspring traits. Among newly-hatched larvae, the variance in body area was explained by temperature (18 %) and seasonal (12 %) but not maternal effects. As yolk-sac larvae reached maximum size, egg size and individual females together accounted for more than two-thirds (77 %) of the variance in body area, while seasonal and temperature effects did not explain additional variance. The maternal effects were, however, unrelated to female size (total length of 26.0–31.3 cm). As a result, size classes of females matched poorly (14–36 %) with those of egg and yolk-sac larval stages, while size classes of eggs matched well with those of maximum-sized larvae (59 %) and less with those of newly-hatched larvae (36 %). Furthermore, yolk-sac larvae from later in the season or from the 13 °C treatment had a relatively longer post-hatch, free-swimming yolk-sac larval stage with respect to the whole yolk period. Yolk utilization efficiency was similar and deformity percentage was low (<5.3 %) across seasonal timing and temperature treatments. In conclusion, our study revealed that the seasonal effects on offspring size at the transition period from endo- to exogenous feeding were attributed to differences in egg size, with herring females spawning earlier in the season producing larger eggs. </ul
The combined role of near-bed currents and sub-seafloor processes in the transport and pervasive burial of microplastics in submarine canyons
No full textSubmarine canyons are important conduits for microplastic transport to the deep sea, but the processes involved in that transport and how faithfully seafloor deposits record trends in pollution remain unclear. We use sediment push cores for microplastic and sediment grain-size analysis from two transects across the Whittard Canyon, UK, to investigate the roles of near-bed flows and sub-seafloor processes in the transport and burial of microplastics and semi-synthetic microfibres. Microplastic and microfibre pollution is pervasive across the canyon at both transects, from the thalweg and from 500 m higher on the flanks, despite turbidity currents being confined to the canyon thalweg. We calculate sediment accumulation rates from 210Pb dating and show that microplastic concentrations remain similar at sediment depths down to 10 cm. Throughout the Whittard Canyon there is an observed uniformity in the gradual decline in microfibre concentration with sediment depth, despite the variable sample locations and marked variations in sediment accumulation rates. Furthermore, the huge global increase in plastic production rates over time is not recorded, and microplastics are present in sediments that predate the mass production of plastic. The interaction of turbidity currents, deep tidally driven currents and sub-seafloor processes affects microfibre burial processes in the deep sea and shreds any potential signal that microplastics may provide as indicators of historical plastic production rates; complicating the use of microplastics as fully reliable markers of Anthropocene onset.</span
Emerging priorities in terrestrial herbivory research in the Arctic
No full textHerbivores are an integral part of Arctic terrestrial ecosystems, driving ecosystem functioning and sustaining local livelihoods. In the context of accelerated climate warming and land use changes, understanding how herbivores contribute to the resilience of Arctic socio-ecological systems is essential to guide sound decision-making and mitigation strategies. While research on Arctic herbivory has a long tradition, recent literature syntheses highlight important geographical, taxonomic, and environmental knowledge gaps on the impacts of herbivores across the region. At the same time, climate change and limited resources impose an urgent need to prioritize research and management efforts. We conducted a horizon scan within the Arctic herbivory research community to identify emerging scientific and management priorities for the next decade. From 288 responses received from 85 participants in two online surveys and an in-person workshop, we identified 8 scientific and 8 management priorities centred on (a) understanding and integrating fundamental ecological processes across multiple scales from individual herbivore–plant interactions up to regional and decadal scale vegetation and animal population effects; (b) evaluating climate change feedbacks; and (c) developing new research methods. Our analysis provides a strategic framework for broad, inclusive, interdisciplinary collaborations to optimise terrestrial herbivory research and sustainable management practices in a rapidly changing Arctic.</span
A marine and salt marsh sediment organic carbon database for European regional seas (EURO-CARBON)
No full textMarine and salt marsh sediments contain large amounts of organic carbon (OC) and are therefore important in the global carbon cycle. Here, we collated previously published and unpublished measurements of sediment OC in marine and salt marsh sediments in European regional seas (EURO-CARBON; available at https://doi.org/10.5281/zenodo.14905489). To the extent possible the OC data were complemented by variables such as sediment porosity and dry bulk density. The EURO-CARBON dataset holds 61306 individual data entries of sediment OC content from different regions of European regional seas. Around three quarters (76%) were collected in coastal and deep sea bare sediments, 18% from salt marshes, 7% from seagrass habitats, and 0.03% from macroalgal habitats. For all habitats and sediment depth layers the OC content varied between <0.1 and 41.56 % (avg.: 2.47 ± 3.37 %; median: 1.39 %), with the content generally decreasing in the following sequence: salt marsh (5.01 ± 5.96 %; 3.03 %) > seagrass (2.37 ± 5.96 %; 3.03 %) > bare sediment (1.88 ± 2.03 %; 1.20 %). The EURO-CARBON dataset will serve as a basis for future work, and it will be an important resource for researchers, managers, and policymakers working towards protecting sediment OC pools.</span
Investigating viable residential uses of old urban wells in Middelburg
No full textThis study assesses the feasibility of utilizing well water in historic Middelburg, Zeeland, the Netherlands, as a source of drinking or graywater for residential purposes. Wells are prevalent in century old Middelburg houses when these were dug to access otherwise scarce freshwater. These wells became obsolete as modern amenities made freshwater available in all houses. However, many of these wells remain and some still discharge water, to the extent that it has to be pumped out and wasted. Given the specific challenges faced in this delta, of increasingly dry summers and saltwater intrusion in aquifers, freshwater can become even more scarce and costly. It is essential to explore every potential freshwater source, including this neglected well water. Therefore, seven wells in Middelburg were tested for common water quality parameters over a period of 6 months, including pH, temperature, dissolved oxygen, conductivity, phosphate, lead, copper, and E. coli. The conductivity confirmed the water to be freshwater, pointing to rainwater as a source, which finds its way underground and flows on remnants of sandy tidal creek beds. Dissolved oxygen levels were low in all wells except one. E. coli was not found, but unidentified coliform bacteria were present. All other parameters tested were within a normal range for drinking water. Despite these yet unknown coliform bacteria, the water in some of the wells is still useable as graywater. As most of the water is now pumped out, the residents can use the results of this study to find useful applications for their water as water stress in the area is increasing. By investigating new freshwater sources, this study contributes to the ongoing search for solutions to mitigate the ever-growing pressures on global freshwater resources.</span
Detecting polystyrene nanoparticles in environmental samples: a comprehensive quantitative approach based on TD-PTR-MS and multivariate standard addition
No full textSubmicrometer-sized plastic particles (nanoplastic; NP) have been detected in a large variety of different ecosystems. They occur in small quantities within a complex organic matrix comprising a plethora of compounds. A robust quantification of the NP concentration thus requires the development of a comprehensive analytical workflow to handle potential interferents. Thermal desorption–proton-transfer reaction–mass spectrometry (TD-PTR-MS) creates the necessary chemical selectivity to distinguish NP signals from the organic matrix. Nevertheless, the recorded raw mass spectra are too complex for direct interpretation, and further signal clustering/scoring is required for a more in-depth analysis. Here, we resolved this problem in a novel workflow, which combines non-negative matrix factorization (NMF) and multivariate standard addition (MSA). This allows us to mathematically separate the NP’s signature from the mixture, as showcased for polystyrene nanoparticles. The method produces an unequivocal and matrix-corrected NP fingerprint for identification and quantification. MSA and NMF enabled us to quantify polystyrene NP in different environmental samples in the lower nanogram range. The mass concentration of polystyrene NP in Waal River water sampled close to Nijmegen, the Netherlands, was 4.7 ± 0.65 ng/mL and 39 ± 0.70 ng/g in sand samples from the river’s shore. A sand sample from a local playground in Nijmegen exhibited a higher concentration of 129 ± 1.1 ng/g.</span
The Eocene–Oligocene Transition in the Paratethys: boreal water ingression and its paleoceanographic implications
No full textThe Eocene–Oligocene Transition (EOT) represents a pivotal period in Earth\u27s climatic history, marked by the onset of Antarctic glaciation and global cooling. While deep-sea records have extensively documented this transition, its impacts on marginal and epicontinental seas remain less understood. This study investigates the impacts of the EOT in the Karaburun composite section, located in the Eastern Paratethys. Using a multidisciplinary approach that integrates biostratigraphy, geochemistry, geochronology, and sequence stratigraphy, a robust chronostratigraphic framework for the latest Eocene to early Oligocene was established. The stable isotopic shifts observed in benthic and planktic foraminifera δ18O and δ13C records at Karaburun align with global patterns but also reveal regional effects, such as freshwater influx and basin restriction, specific to the semi-restricted Paratethys. The abrupt negative δ18O shift across the Eocene–Oligocene Boundary (EOB) in the Paratethys reflects boreal water ingressions driven by the onset of anti-estuarine circulation between the Nordic Seas and the Atlantic and the closure of the Arctic–Atlantic gateway, which redirected cold, low-salinity boreal waters through interconnected basins towards the Paratethys. These findings highlight the interplay between global climate drivers and regional hydrological dynamics, providing critical insights into the evolution of marginal marine environments during the EOT. Our results underscore the significance of the Paratethys as a unique archive for studying the onset of global icehouse climate conditions and regional responses.</span
The joint effects of planetary B, topography and friction on baroclinic instability in a two-layer quasi-geostrophic model
No full textThe quasi-geostrophic two-layer model is a widely used tool to study baroclinic instability in the ocean. One instability criterion for the inviscid two-layer model is that the potential vorticity (PV) gradient must change sign between the layers. This has a well-known implication if the model includes a linear bottom slope: for sufficiently steep retrograde slopes, instability is suppressed for a flow parallel to the isobaths. This changes in the presence of bottom friction as well as when the PV gradients in the layers are not aligned. We derive the generalised instability condition for the two-layer model with non-zero friction and arbitrary mean flow orientation. This condition involves neither the friction coefficient nor the bottom slope; even infinitesimally weak bottom friction destabilises the system regardless of the bottom slope. We then examine the instability characteristics as a function of varying slope orientation and magnitude. The system is stable across all wavenumbers only if friction is absent and if the planetary, topographic and stretching PV gradients are aligned. Strong bottom friction decreases the growth rates but also alters the dependence on bottom slope. In conclusion, the often mentioned stabilisation by steep bottom slopes in the two-layer model holds only in very specific circumstances, thus probably plays only a limited role in the ocean.</span
The hanging gardens of Blanes Canyon, Northwestern Mediterranean Sea
No full textSubmarine canyons are ubiquitous geomorphic features found intercepting the continental margins. As such, they provide environmental conditions suitable for many suspension feeding organisms, as they settle on steep rocky canyon walls, whilst taking advantage of increased currents that bring suspended organic matter and food. Additionally, demersal fishing grounds can be found surrounding submarine canyons where it can negatively affect species inhabiting these environments, including vulnerable ecosystems such as cold-water corals (CWCs). In order to understand the impacts of demersal fisheries in CWC communities, we first need to understand their distribution, species composition and vulnerability. Blanes Canyon is an example of a submarine canyon surrounded by demersal fishing grounds, where baseline knowledge on CWCs currently lacks. This study contributes to filling these knowledge gaps by using a dense grid of ROV transects along the canyon, high resolution bathymetry data and CTD surveys, which altogether provide a quantitative description of megabenthic assemblages. Blanes Canyon hosts at least 12 CWC species within 450–1300 m depth range, mainly inhabiting the steep canyon walls. Different assemblages of CWC species were found. Desmophyllum dianthus was the most abundant species, found throughout the entire canyon. Colonial scleractinian species (Desmophyllum pertusum and Madrepora oculata) were found in the canyon head but were lacking in the eastern canyon branch, where octocorals (Muriceides lepida) and black corals (Leiopathes glaberrima) were prevailing. Detailed CTD survey indicated that nepheloid layers (bottom and intermediate) were found at the same depth range as the megabenthic communities, since they provide suspension feeders with particulate organic matter (POM). Overall, this study confirms Blanes Canyon as a CWC habitat, providing densities and spatial distribution of different megabenthic species, along with information of their environmental niches.</span
Impact of terrestrial organic matter input on distributions of hydroxylated isoprenoidal GDGTs in marine sediments: Implications for OH-isoGDGT-based temperature proxies
No full textIsoprenoidal glycerol dialkyl glycerol tetraethers (isoGDGTs) and hydroxylated isoGDGTs (OH-isoGDGTs) are widespread in marine, lacustrine, and terrestrial environments and serve as paleoenvironmental proxies. Several indices based on their distributions, such as (based on isoGDGTs), , (both based on OH-isoGDGTs), and (both based on isoGDGTs and OH-isoGDGTs), have been utilized as sea water temperature proxies. Although terrestrial organic matter (OM) input of isoGDGTs may affect the in coastal marine settings, relatively little is known on its consequences for OH-isoGDGT distributions and related proxies. Here, we studied the distributions of OH-isoGDGTs in soils, rivers, and coastal marine settings at three locations: the Kara Sea, the Iberian margin, and the northern Gulf of Mexico, receiving terrestrial OM through the Yenisei, the Tagus and the Mississippi Rivers, respectively. In general, we observe higher relative abundances of OH-isoGDGTs () in coastal marine environments compared to soils and rivers from the same area. Comparison of OH-isoGDGT distributions shows that, in particular, the abundance of OH-isoGDGT with one cyclopentane moiety relative to total OH-isoGDGTs was lower in terrestrial settings. In general, the was higher in terrestrial settings, while such a consistent offset was not observed for . The index, exhibits a distinct difference between terrestrial and marine settings, similar to the pattern observed for the . This similarity is primarily attributed to the relatively minor influence of terrestrial OH-isoGDGTs compared to regular isoGDGTs in the index. Despite these differences, only the coastal sediments of the Kara Sea showed indications of a potential bias of OH-isoGDGTs-based proxies caused by terrestrial OM input. However, these distributional variations may also be caused by the large salinity gradient in the Kara Sea, since it has been established that salinity has an effect on the distributions of OH-isoGDGTs. Our results show that caution should be exercised when interpreting temperature estimates based on OH-isoGDGT proxies in marine settings affected by large river outflows resulting in a substantial terrestrial OM input and/or have a strong salinity gradient.</span