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Assessing the potential physiological impacts of urban development around lemon shark (Negaprion brevirostris) nurseries: effects on neonate and juvenile health
No full textHighlights:
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Urbanization threatens critical lemon shark nurseries in The Bahamas.
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Degraded nurseries show elevated stress markers in neonate and juvenile sharks.
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Community-based conservation is vital to preserve mangroves and nursery habitats.
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Strengthened legal frameworks are needed to mitigate urbanization impacts.
Urbanization driven by population growth, development and tourism increasingly threatens even remote areas, potentially impacting biodiversity. This is particularly concerning given the ecological and economic importance of biodiversity, especially for island nations, where ecotourism plays a crucial role in the economy. This study examines urban-driven degradation effects on the nurseries of lemon sharks, a predator with strong site fidelity to its birthing and nursery areas. Six sites in South Eleuthera, The Bahamas, were assessed, analyzing proxies indicative of body condition (triglycerides/cholesterol ratio, body condition index) and energetic stress markers (glucose, β-hydroxybutyrate, triglycerides, total cholesterol) in neonates and juveniles compared across nurseries relative to degradation scores. While TAG/CHOL and BCI were not significantly different between nurseries, energetic markers were overall higher in more degraded nurseries. Moreover, total urban score was a significant predictor for glucose, β-hydroxybutyrate, and triglyceride ciruclating concentrations. These findings, coupled with prior studies carried out in Bimini, suggest that urban development around lemon shark nurseries in The Bahamas may negatively impact shark health. Cooperative monitoring, community initiatives for mangrove preservation, and stronger urbanization laws are required to mitigate these impacts. As urbanization and environmental degradation are universal threats to mangroves worldwide, this approach can be adapted to study urbanization impacts on other species in regions such as Southeast Asia, the Caribbean, the Pacific Islands, and the coasts of Africa and South America, which face similar urban encroachment, habitat degradation, and biodiversity loss challenges
Variability of the Western Boundary Circulation and AMOC in the tropical Atlantic: Insights from in-situ observations
No full textEnhanced deglacial carbon transport by Pacific southern-sourced intermediate and mode water
No full textSouthern-sourced Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) are currently major sinks of atmospheric CO2. During the last deglaciation, atmospheric CO2 levels increased significantly during two specific time periods, Heinrich Stadial 1 (H1) ~18–14.6 ka BP (thousand years ago before present) and the Younger Dryas (YD) ~12.8–11.5 ka BP. Model simulation and proxy data studies suggest that AAIW/SAMW was crucial in explaining these changes during H1 and YD, but its variability and properties in the Southeast Pacific Ocean are still largely unknown. Here, we present records of benthic foraminiferal carbon isotopes, Mg/Ca-based water temperatures, paleosalinity reconstructions, and sortable silt mean grain size variations over the last 30 thousand years from Ocean Drilling Program (ODP) Site 1233, in the Southeast Pacific Ocean, which is bathed in AAIW/SAMW. Our proxy data suggest an increased northward circulation of high pCO2/ nutrient-enriched AAIW/SAMW during H1 and YD. Our data provides support for AAIW/SAMW as one of the important conduits for deglacial oceanic outgassing in the eastern equatorial Pacific upwelling. © The Author(s) 2025
Environmental changes reflected by sedimentary records of detrital minerals in the eastern Laptev Sea over the past 12 kyrs
No full textHighlights:
• Sedimentary setting of river, permafrost, and sea-ice in the eastern Laptev Sea were reconstructed since the Holocene.
• Warm climate (10.4–8.2 ka) and high organic input promoted widespread authigenic mineral formation.
• Volcanic glass increase (8.2–5.0 ka) indicates major glacial and snowmelt freshwater input from Siberian rivers.
• Decreased river input and increased anchor-ice transport on the western shelf occurred since the last 2 ka.
Abstract
The Siberian Arctic shelf is important for sediment transport and deposition, shaped by complex interactions among river input, permafrost erosion, and sea ice processes. Despite advances in understanding these systems, the sedimentary evolution of the eastern Laptev Sea shelf over the Late Pleistocene, and its response to sea-level and climate changes, remains unclear. Here, we analysed light and heavy minerals, coarse components and sediment smear slide estimations from a sediment core collected on the paleo-floodplain of the Yana and Lena rivers, compared them with surface sediments. The results reveal four distinct sedimentary periods: (1) a river floodplain phase (∼12–10.4 ka BP), characterized by fluvial deposits rich in micas, limonite, quartz, and plagioclase; (2) a fine-grained, organic-rich phase linked to permafrost erosion and/or island flattening under warmer climate conditions and rapid sea level rising (∼10.4–8.2 ka BP), with abundant authigenic barite, pyrite, and siderite; (3) a peak fluvial input phase during continuous sea level rise (∼8.2–5.0 ka BP), marked by increased volcanic glass and initially intensified sea ice; (4) the modern sedimentary regime (∼5.0–0 ka BP), with decreased fluvial input and strengthened sea ice transport. Since ∼2 ka BP, increased silt content indicates that more sediment originates from anchor ice on the shelf. Variations in detrital minerals, such as hypersthene, suggest sediment contributions from the western Laptev Sea, Lena, Khatanga, and Anabar Rivers, and even the Taymyr Peninsula and Kara Sea, indicating an eastward shift in the Transpolar Drift System
Thermal Selection Shifts Genetic Diversity and Performance in Blue Mussel Juveniles
No full textExploring evolutionary and physiological responses to environmental stress is crucial for assessing the effects of climate change on wild populations. Mussels, key inhabitants of the benthos with high ecological and economic value, are a particularly vulnerable species that may be pushed to their ecological limits as warming threatens their survival and population stability. Species within the Mytilus edulis complex are commonly found in temperate regions globally; in the Baltic Sea, populations are formed by M. edulis and M. trossulus hybrids with low levels of M. galloprovincialis introgression. This study investigates the mechanisms through which resilience towards global warming may be fast-tracked in Baltic mussels (Kiel, Germany). For this, we studied two cohorts of juvenile mussels (recently settled animals), one exposed to an extreme heat event early in life and one na & iuml;ve to this stressor. Both cohorts were later exposed to experimental temperatures ranging from 21 degrees C to 26 degrees C, with animal performance measured after 25 days. Impacts of thermal stress on the genetic composition of each cohort was then assessed by genotyping 50 individuals using a blue mussel 60 K SNP-array. We observed a significant increase in M. edulis genotypes together with a decrease in M. trossulus in the challenged cohort, compared to naive juveniles. We also found exposure to high temperature affected performance of mussel cohorts, reducing dry tissue weight of selected individuals. Results from this study provide insights on how selection through thermal stress impacts performance and genetic composition of key globally distributed intertidal species, with important implications for understanding and managing mussel populations under future warming scenarios
Uncovering the Nanozostera japonica species complex suggests cryptic speciation and underestimated seagrass diversity
No full textSummary:
The importance of marine angiosperms, or seagrasses, as foundation species for marine coastal ecosystems is in marked contrast to their low species number of only 70 described taxa. Seagrass species tend to have very similar overall morphologies dictated by hydrodynamic forces of the ocean environment. Moreover, they have inconspicuous and simple flowers, probably due to the absence of flower–pollinator interactions in the sea. We hypothesized that the seagrass species Nanozostera japonica, distributed from tropical to temperate latitudes in the North-Western Pacific, contains cryptic species.
To test this, we assembled two chromosome-level reference genomes and conducted whole-genome resequencing at 17 locations throughout its native distribution.
We identified two genetically divergent clades in the north and south of its range (hereafter Nj_N and Nj_S) that diverged some 4.16 million years ago. Hybrid individuals at a contact zone were either diploid F1-crosses or featured triploidy, indicating reproductive isolation. A large (42 Mb) reciprocally fixed chromosomal inversion between Nj_N and Nj_S possibly contributed to the formation of the reproductive isolation.
We conclude that the N. japonica species complex is actually consisting of two different species. Further population genomic studies may reveal additional cryptic species, solving the conundrum why there are so few described seagrass species today
Geophysical characterization of a transform fault, TRANSFORMERS III, Cruise No. M204, 27.09.2024 - 20.10.2024, Bridgetown (Barbados) - Las Palmas, Canary Islands (Spain)
No full textOceanic transform faults (OTF) are one of three major types of plate boundaries of plate tectonics. Yet, plate tectonics predicted a rather simple geometry for OTFs and consequently their structure and mode of deformation attracted reasonable little attention. However, recent evidence suggests that the traditional concept of transform faults as being conservative (non-accretionary) plate boundary faults might be wrong. Instead, numerical modelling results suggest that transform faults seem to suffer from extensional tectonics below their strike-slip surface fault zone in the vicinity for the ridge-transform intersection, forming the wide transform valleys. During the survey M024, we went forward to test the hypothesis at the Oceanographer OTF to the south of the Azores by (i) revealing the displacement of the strike-slip fault using seafloor geodesy (direct path ranging) and (ii) studying the micro-seismicity and its relation to tectonic elements of the OTF (transform valley, strike-slip fault trace, bounding walls) with a network of long-term ocean-bottom-seismometers (OBS) and a seafloor geodetic network deployed in fall of 2023 with the RV MARIA S. MERIAN during its cruise MSM122. All stations were recovered during M204. In addition, we used the transit into the working area to map the axis of the Mid-Atlantic Ridge between the Atlantis and the Oceanographer transform fault; during the transit to port, we use the opportunity to map parts of the Great Meteor Seamount
Distribution patterns of nitrous oxide during the summer season in the Prydz Bay, eastern Southern Ocean
No full textThe global ocean is a major source of the climate-relevant atmospheric trace gas nitrous oxide (N2O). However, an accurate assessment of the global oceanic emissions of N2O is hampered by missing data on dissolved N2O from large regions such as the Southern Ocean. To address this deficit, N2O was measured in the Prydz Bay in February 2015 during the 31st Chinese National Antarctic Research Expedition. N2O concentrations (saturation) in the surface layer were generally low (undersaturation with respect to atmospheric equilibrium) and ranged from 13.3 nmol/L to 16.1 nmol/L (83%–102%) at the time of sampling. A comparison of our observations with archived data revealed that no discernible trend in N2O concentrations in the surface waters of Prydz Bay could be detected for the period between 2006 and 2015. Temperature and salinity changes driven by meltwater input were the predominant controls on N2O concentrations in surface waters. At depth, the distribution of N2O concentrations was dominated by production via nitrification in offshore deep waters and vertical convection in the shelf waters, where concentrations were lower and gradients were less steep. Our results suggest a rather unusual pattern of N2O distribution in the Prydz Bay (low N2O in shelf waters compared with the open ocean), providing important insights into the coastal dynamics of N2O in highlatitude polar regions
Settling Velocities of Tire and Road Wear Particles: Analyzing Finely Graded Density Fractions of Samples from a Road Simulator and a Highway Tunnel
No full textThe terminal settling velocity is considered the most critical parameter determining the transport of tire and road wear particles (TRWP) in aquatic environments. Nonetheless, no respective empirical data has been reported so far. In this study, particle samples from a road simulator and a highway tunnel were investigated with a validated imaging method. Different density and size fractions of both samples were measured separately, acquiring sizes and settling velocities of more than 30,000 individual particles. In addition, tire marker polymers were analyzed for each fraction via thermal extraction desorption-gas chromatography/mass spectrometry. Finally, the acquired particle data was combined according to the fractions' estimated tire contents in order to deduce detailed probability distributions of particle size and settling velocity for the actual TRWP from both samples. Weighted by TRWP-incorporated tire mass, median diameters of 54 and 44 mu m as well as median settling velocities of 0.65 and 0.22 mm/s were found for TRWP from the road simulator and highway tunnel, respectively. This study thus provides the first ever empirical data on TRWP settling velocities in water, which can be highly valuable input for modeling the environmental transport of TRWP and for dimensioning TRWP retention systems
Unraveling the mystery of recent shortened response time of ENSO to Atlantic forcing
No full textThe El Niño-Southern Oscillation (ENSO) is known to respond to tropical Atlantic (TA) sea surface temperature (SST) forcing. However, the response time of ENSO to the TA SST forcing is not stationary but varies over decades, the reasons for which remain poorly understood. Here we show that decadal changes in ENSO’s response time to TA SST forcing are primarily influenced by the south-north shift of the dominant mode of TA SST variability itself. Before the mid-1980s, the southward-shifted TA mode prolongs the response time to ~20 months through an eastward-propagating mid-latitude teleconnection. In contrast, when the TA mode shifts northward after the mid-1980s, the response time decreases to 6–9 months via a faster westward-propagating subtropical teleconnection. Our findings underscore the importance of considering the meridional shift of the TA mode when understanding the impacts of the TA SST variability on ENSO, which has profound implications for ENSO forecasting. © The Author(s) 2025