Diel Research Articles

Deep-Pelagic Fishes Are Anything But Similar: A Global Synthesis.

Deep-pelagic fishes are among the most abundant vertebrates on Earth. They play a critical role in sequestering carbon, providing prey for harvestable fishing stocks and linking oceanic layers and trophic levels. However, knowledge of these fishes is scarce and fragmented, hampering the ability of both the scientific community and stakeholders to address them effectively. While modelling approaches incorporating these organisms have advanced, they often oversimplify their functional and ecological diversity, potentially leading to misconceptions. To address these gaps, this synthesis examines the biodiversity and ecology of global deep-pelagic fishes. We review pelagic ecosystem classifications and propose a new semantic framework for deep-pelagic fishes. We evaluate different sampling methods, detailing their strengths, limitations and complementarities. We provide an assessment of the world's deep-pelagic fishes comprising 1554 species, highlighting major groups and discussing regional variability. By describing their morphological, behavioural and ecological diversity, we show that these organisms are far from homogeneous. Building on this, we call for a more realistic approach to the ecology of deep-pelagic fishes transitioning between very different ecological niches during diel vertical migrations. To facilitate this, we introduce the concept of 'diel-modulated realised niche' and propose a conceptual model synthesising the multiple drivers responsible for such transitions.

Changes of vertical distribution of Microcystis colonies driven by short-term rainfall: Disappearance and reformation of surface bloom

Global climate warming and human activities have increased the magnitude and frequency of Microcystis surface blooms, posing significant threats to freshwater ecosystems and human health over recent decades. Heavy rainfall events have been reported to cause the disappearance of these blooms. Although some studies have employed turbulence models to analyze the movement characteristics of Microcystis colonies, the impact of rainfall is complex, comprehensive investigations on their vertical migration induced by short-term rainfall are still necessary. Utilizing monitoring data from eutrophic ponds and controlled simulation experiments, this study examines the short-term impacts of rainfall on the vertical distribution of Microcystis in the water column. Our findings indicate that rainfall contributes to the disappearance of Microcystis blooms by reducing the quantity of small to medium-sized colonies (0–100 μm) at the surface, subsequently decreasing the overall Microcystis biomass. As rainfall intensity increases, larger colonies migrate deeper into the water column. At a rainfall threshold of 666 mm, the difference in the median volume diameter (DV50) of Microcystis colonies between the surface and bottom reaches a minimal value of 3.09%. Post-rainfall, these colonies rapidly ascend, aggregate into larger formations, and re-establish surface blooms. The greater the rainfall, the smaller the resultant Microcystis biomass, albeit with larger aggregated colony sizes. When rainfall exceeds 222 mm, the recovery rate of surface Microcystis biomass remains below 100%, decreasing to 19.48% at 666 mm of rainfall, while the median volume diameter (DV50) of the colonies increases to 139.07% of its pre-rainfall level. Furthermore, compared to pre-rainfall conditions, the photosynthetic activity of the surface Microcystis colonies was enhanced and the secretion of EPS was increased under heavy rainfall conditions. Our results identify a critical response time of 30 min for Microcystis colonies to rainfall, after which the response ceases to intensify. These insights are crucial for predicting post-rain Microcystis bloom dynamics and aiding management authorities in timely interventions.

Unveiling vertical migration patterns of the mesopelagic fish Ceratoscopelus warmingii in cold seep ecosystems: A trophic niche perspective

Ceratoscopelus warmingii, a common mesopelagic fish in cold seep ecosystems, plays a crucial role in transferring energy and materials between different water layers, thereby influencing deep-sea carbon cycling and storage. In August 2023, we collected samples from four depths (75 m, 400 m, 500 m, and 600 m) in cold seep waters to analyze the trophic niche characteristics of C. warmingii using stable isotope techniques. The results indicated significant differences in δ13C and δ15N values among the water layers, with mean δ13C and δ15N values of −19.85 ‰±0.33 ‰ and 8.41 ‰±0.62 ‰, respectively. Indicators of trophic structure showed distinct vertical differentiation, with the width of the trophic niche decreasing as depth increased. At 75 m and 400 m, the consistency of CR and NR indicators and high trophic niche overlap indicated similar food sources, confirming vertical migration behavior. In contrast, at 500 m, the MNND and SDNND values suggested a more stable trophic structure, while at 600 m, changes in feeding sources pointed to a distinct population. The Standard Ellipse Area of Overlap (SEAc) was highest between 75 m and 400 m, while the divergence of trophic ecological niches at 600 m, with different food sources, suggests that cold seep ecosystems at this depth provide a relatively stable trophic structure for C. warmingii and support the formation of an independent population. In cold seep ecosystems, C. warmingii employs adaptive trophic strategies to optimize survival under varying habitat conditions at different depths. This vertical trophic differentiation reduces intraspecific competition and enhances population stability in deep-sea habitats. This study enhances our understanding of the trophic niche and vertical migration of C. warmingii in cold seep ecosystems, significantly contributing to our knowledge of biodiversity, energy flow, and material cycling in these unique environments.

Modelling the complete life cycle of an arctic copepod reveals complex trade-offs between concurrent life cycle strategies

Calanus hyperboreus is a large-bodied, biomass dominant species that performs a crucial ecosystem energy transfer by converting the spring phytoplankton bloom into lipid reserves that fuel the higher trophic levels of the Gulf of St. Lawrence (GSL) pelagic ecosystem, including the critically endangered North Atlantic right whale (Eubalena glacialis). Given that the GSL, the southernmost core habitat of C. hyperboreus, is undergoing rapid warming, developing a population model allows us to synthesize existing knowledge of the species, and to examine the species response to environmental conditions. To simulate the multi-year life cycle in the northwest GSL, model equations are implemented for ingestion, assimilation, respiration, egg production, stage development, mortality, and vertical migration behaviors including dormancy entry and exit. The 1-D particle-based model predicts the evolution of individual stage, structural mass, lipid, age, sex, abundance, and egg production, as well as the seasonal evolution of the population structure in the northwest GSL. Individual lipid-based thresholds inform the timing of ontogenetic vertical migration. Life cycle targets defined from a literature review are used to guide model parameterization and assess its performance. The simulated population structure, phenology, and size at stage are generally consistent with observations. Under 10 years of repeat year forcing, the model simulates a quasi-stable overwintering population composed of late stages CIV, CV and CVI. Observations suggest that stage CIV is the first overwintering stage in the GSL, and point to the occurrence of iteroparous females. Using the model, the relative success of diverse dormancy and reproductive phenotypes are explored. Second reproduction females reproduce earlier in winter than first reproduction females, with implications for the ability of the new generation to match the spring bloom and accumulate sufficient lipid to overwinter as stage CIV. Without iteroparity, the time window of reproduction contracts and the population is reduced, underscoring the role of a flexible multi-year life cycle in population success.

Geochemical Characteristics and Origin of Natural Gas in the Middle of Shuntuoguole Low Uplift, Tarim Basin: Evidence from Natural Gas Composition and Isotopes

Multiple types of reservoirs, including volatile oil reservoirs, condensate gas reservoirs, and dry gas reservoirs, have been discovered in ultra-deep layers buried at depths greater than 7500 m. Understanding the genetic types of natural gas is of utmost importance in evaluating oil and gas exploration potential. The cumulative proved reserves of the super deep layer in the Shuntuoguole low uplift area of the Tarim Basin exceed 1 × 108 t (oil equivalent). The origin, source, and accumulation characteristics of natural gas still remain a subject of controversy. By analyzing the composition and carbon isotope of natural gas, a detailed investigation was conducted to examine the unique geochemical and reservoir formation characteristics of the Ordovician ultra-deep natural gas within different fault zones in the middle region of the Shuntuoguole low uplift. It was determined that most of the natural gas in this area is displaying a characteristic of wet gas with a drying coefficient ranging from 0.41 to 0.99. The carbon isotope composition of methane in the gas reservoir shows relatively light values, ranging from −49.4‰ to −42‰. The carbon and hydrogen isotopes of the components are distributed in a positive order. The natural gas is oil type gas, which is derived from marine sapropelic organic matter and has a good correspondence with the lower Yuertusi formation. The maturity of natural gas in Shunbei No. 1 and No. 5 fault zones is about 1.0%, which is the associated gas of normal crude oil, while the maturity of No. 4 and No. 8 fault zones is higher than 1.0%, which is the mixture of kerogen pyrolysis gas and crude oil pyrolysis gas. The variations in the drying coefficient and carbon isotope composition of the natural gas provide evidence for the migration patterns within the Shuntuoguole low uplift central region. It indicates that the Shunbei No. 5 and No. 8 fault zones have likely migrated from south to north, while the No. 4 fault zone has migrated from the middle to both the north and south sides. These migration patterns are primarily controlled by high and steep strike-slip faults, which facilitate the vertical migration of natural gas along fault planes. Consequently, the gas accumulates in fractured and vuggy reservoirs within the Ordovician formation.

First telemetry insights into the movements and vertical habitat use of megamouth shark (Megachasma pelagios) in the northwest Pacific

The megamouth shark (Megachasma pelagios) is one of the ocean's largest and most enigmatic elasmobranchs, with only a few hundred individuals ever recorded. Most of what is known about the species comes from rare fishery bycatch, stranding, or sighting events, precluding an in-depth understanding of its movement ecology. Here, we report the results from three megamouth sharks outfitted with pop-up satellite archival transmitting tags to assess the species' horizontal and vertical movement patterns. Deployments of 12, 58, and 244 d in duration provided the first direct evidence of multi-month fidelity to the waters east of Taiwan and seasonal movement out of the region. Depth and temperature data revealed a pattern of normal diel vertical migration, with the majority of the day spent in the mesopelagic zone and night in the epipelagic. Vertical habitat use suggests potential behavioral thermoregulation and was consistent with tracking of migrating mesopelagic prey across diel periods. We discuss the specialized analytical methods needed to reconstruct the spatial habitat use of deep-diving megamouth shark from tag sensor measurements of the magnetic field, as well as avenues for future research on this understudied megaplanktivore.

Migration of depleted uranium from a corroded penetrator in soil vadose zone in Bosnia and Herzegovina

Depleted uranium (DU) from corroded armor penetrators can migrate through the soil vadose zone and cause environmental problems, yet studies on such migration at former theatres of war are scarce. Here, we investigated vertical DU migration in a soil profile due to a penetrator (3–8 cm beneath the soil surface) corroded over 7 years in Bosnia and Herzegovina. The highest concentration of DU was ∼45,300 mg/kg at 6–10 cm, with the concentration decreasing markedly with increasing depth. The majority of the DU accumulated within the top 20 cm and the DU front reached ∼42 cm beneath the penetrator. In addition, particles with varying U concentrations (3–65 wt%) were observed at 0–15 cm, with U primarily co-located with O, Si, Al, maghemite, and hematite. Particularly, metaschoepite was identified at 6–10 cm. Finally, X-ray absorption spectroscopy analysis found U was hexavalent in the soil profile. These findings suggest that the downward migration of DU was likely present as a soluble form adsorbed on clay minerals and Fe oxides. Overall, we show that the rate of DU migration within the vadose zone is comparatively slow, although if the penetrator is left in the soil for decades, it could pose a serious long-term risk. Environmental ImplicationsOver 90 % of the depleted uranium (DU) penetrators fired in previous conflicts missed their armored targets and were left in the soil to corrode. The corroded penetrators can not only contaminate soil but also pose a risk to groundwater. The present study examined the migration of DU in a soil profile that included a DU penetrator that had been corroding for over 7 years. Studying the dynamics of DU migration is essential to develop effective remediation strategies to mitigate long-term environmental risks and safeguard ecosystems and human health from DU contamination.

Identification of Individuals of Two Takin Subspecies Using Biological and Ecological Criteria in Eastern Himalayas of China.

Limited background data are available on the Mishmi takin (Budorcas taxicolor taxicolor) and Bhutan takin (Budorcas taxicolor whitei) subspecies in the Eastern Himalayas of China because of the lack of systematic field investigations and research. Therefore, mature-animal ecological methods were used to evaluate these takin subspecies' phenotypic characteristics, distribution range, activity rhythm, and population size. From 2013 to 2022, 214 camera traps were installed for wild ungulate monitoring and investigation in all human-accessible areas of the Eastern Himalayas, resulting in 4837 distinguishable takin photographs. The external morphological characteristics were described and compared using visual data. Artificial image correction and related technologies were used to establish physical image models based on the differences between subspecies. MaxEnt niche and random encounter models obtained distribution ranges and population densities. Mishmi takins have a distribution area of 17,314 km2, population density of 0.1729 ± 0.0134 takins/km2, and population size of 2995 ± 232. Bhutan takins have a distribution area of 25,006 km2, population density of 0.1359 ± 0.0264 takins/km2, and population size of 3398 ± 660. Long-term monitoring data confirmed that the vertical migration within the mountain ecosystems is influenced by climate. Mishmi takins are active at 500-4500 m, whereas Bhutan takins are active at 1500-4500 m. The two subspecies were active at >3500 m from May to October yearly (rainy season). In addition, surveying combined with model simulation shows that the Yarlung Zangbo River is not an obstacle to migration. This study provides basic data that contribute to animal diversity knowledge in biodiversity hotspots of the Eastern Himalayas and detailed information and references for species identification, distribution range, and population characteristics.

Different sensitivity of postglacial vegetation to climate and human disturbance between Tibetan Plateau and its surrounding regions

Characterizing the ecosystems' response to environmental changes on Tibetan Plateau (TP), as well as elucidating the regional disparities of these changes across the plateau's surface and its neighboring regions, holds significance for safeguarding the ecological security of Asia. Here, an improved pollen-based biomization procedure, incorporating weighted taxa, was conducted to illustrate the spatial and temporal differences of vegetation changes in TP, Xinjiang and southwestern China over the past 21,000 years. Results showed that the vegetation changes in TP and Xinjiang were characterized by alternations among herbaceous biomes, while the southwestern China were featured by changes among various woody biomes. Asynchronous vegetation change rates (ROCs) were discovered among TP, Xinjiang and southwestern China. The ROCs in TP were generally low during the Last Glacial Maximum but rose abruptly and peaked in the late deglacial period, whereas Xinjiang and southwestern China had high and increasing ROCs during Holocene. Those trajectories might relate to different sensitivities of vegetation to climate change and human disturbances. Habitat limitation on TP should be pretty intense during glacial period, leading to rapid vegetation establishment after glacier retreat. While in Xinjiang, water availability was the most obvious limitation, making the vegetation change sensitive to moisture and atmospheric CO2 variations. The forest in Yunnan behaved the most stability but was characterized by vertical migration responding to deglacial warming. Holocene acceleration of ROCs aligned with intensified human activities in Xinjiang and southwestern China. To sum up, environmental conditions have been always important in determining post glacial vegetation changes in west China, but the ROCs were asynchronous due to different sensitivities of vegetation to climate change and human activity. Although the plateau's vegetation was quite stable during Holocene, the plateau terrestrial ecosystem may subject to increasing risk under accelerating global warming and intensifying human activities.

Distribution patterns of micronektonic crustaceans (Decapoda, Euphausiacea, and Lophogastrida) in the tropical and subtropical Atlantic Ocean

Large pelagic crustaceans are a main component of the micronekton community in the deep-sea having an important role in the food webs and the biological carbon pump. However, they are scarcely studied in comparison to other groups such as mesopelagic fish. Here, we analyse day/night and bathymetric variability in taxonomic composition, abundance, and biomass across a latitudinal transect in the Atlantic Ocean from off Brazil (15°S) to the Canary Islands (25°N). A total of 95 species were identified belonging to 9 different families, of which Euphausiidae was the most abundant family and Acanthephyridae the family contributing the most to the total biomass. We found distinct assemblages associated with Atlantic ecoregions related to the environmental variables. Diel vertical migrations were detected along the entire transect, even crossing the oxygen minimum zone, likely due to the metabolic adaptations of these organisms.

The integration of diel vertical migration and hydrodynamic process influences the transport of swimming crab zoea (Portunus trituberculatus)

AbstractVertical migration and dispersal processes during the marine crab larval stage markedly affect transport, habitat selection, population connectivity, and resource replenishment success rates. However, not much is known of the reproductive ecology of swimming crabs in the nearshore waters of the northwest Pacific shelf. Here, we investigated the diel vertical migration (DVM) characteristics and transport patterns of the swimming crab zoea (Portunus trituberculatus) in this area. A Lagrangian particle‐tracking algorithm coupled with a hydrodynamic model, incorporating a DVM pattern of zoeae based on observations from a field survey of the diurnal distribution of swimming crab zoea, was used to simulate the transport of zoeae, and the impact of zoeal transport on population connectivity was explored. The results revealed that particles were predominantly transported in a nearshore direction from the particle release point, with short dispersal distances during the zoeal stages. In nearshore waters on the continental shelf, the swimming crab zoeae are exposed to shoreward‐moving currents with the aid of prolonged daytime locations in the lower water column, whereas larvae migrate upward to the middle and upper layers of the water column at night rather than the most superficial layer, potentially avoiding surface offshore‐moving currents that may be responsible for the retention and shoreward transport of larvae. Most zoeae are transported to shallow waters, and the contribution of transport to population connectivity during the zoeal stages is relatively limited. The findings here have considerable implications for understanding the mechanisms governing the early recruitment dynamics of this species, as well as for fisheries management and conservation of marine biodiversity.

Pollution characteristics of microplastics in greenhouse soil profiles with the long-term application of organic compost

Organic composts are significant sources of microplastic (MP) pollution in soils, and their input is much higher in greenhouse agriculture than open-field agriculture. However, how long-term compost application affects MPs pollution in greenhouse soil profiles remains unclear. This study examined MPs characteristics in chicken manure compost and earthworms, exploring the long-term impacts of compost application on MPs accumulation and vertical migration in 0–100 cm soil depth through a 15-year greenhouse experiment. Microplastics abundance was 3965 items kg−1 in compost, 191–248 items kg−1 in compost-amended soils, and 2.73–4.52 items individual−1 in earthworms from compost-amended soils; the latter two increased significantly with compost application and were significantly higher than unamended soils. Soil MPs accumulation from long-term compost amendment contributed 45.4% of the total. The proportion of MPs <2 mm in compost (49.7%) was less than in compost-amended soils (65.5%) and earthworms (65.4%). Microplastics size and abundance decreased with increasing soil depth. Microplastics polymer types and shapes in composts, compost-amended soils, and earthworms exhibited similarities, mainly including polyethylene and polypropylene fragments and fibers. Compost-derived MPs in soils exhibited complex weathering morphology and adhered to mineral colloids. Therefore, soil MPs originating from compost gradually weathered and degraded into smaller particles and migrated to deeper soil, maybe resulting in more serious ecological issues.

Research on Residual Gas Adsorption on Surface of Hexagonal Boron Nitride-Based Memristor.

As a promising nonvolatile memory device with two ends, the memristor has received extensive attention for its industrial manufacture. Density functional theory was used to analyze the adsorption properties of residual gas on hexagonal boron nitride (h-BN)-based memristor model surfaces with Stone-Wales-5577 grain boundary defects [h-BN(SW)]. First, by calculating the adsorption energy, geometric parameters, and charge transfer, we identified the most stable adsorption sites for hydrogen atoms (H-TB1) and H2 molecules (H2-TN2). We observed a tendency toward chemisorption for hydrogen atoms and physical adsorption for H2 molecules at these sites. Furthermore, two coadsorption configurations were formed by introducing H2 molecules and hydrogen atoms into single adsorption configurations: namely H-TB1_H2-TN1TN2 and H2-TN2_H-TB1TN1TN3. In the case of hydrogen-based configuration, there is weak dissociation of the H2 molecule, which does not facilitate hydrogen atom adsorption. However, adjacent hydrogen atoms tend to form stable dimers, while excess hydrogen atoms have a tendency to weakly chemisorb in the case of H2-based configuration. The pristine h-BN surface is more favorable for hydrogen atom migration compared to the h-BN(SW) surface due to its higher adsorption energy. On the h-BN(SW) surface, hydrogen atoms tend to migrate inward from the center of adjacent heptagonal boron nitride rings while coadsorption has a minimal impact on their vertical migration as well as that of H2 molecules. This work provides theoretical insights into the H/H2 trace gas interaction during h-BN wafer-level fabrication for memristor devices.

Persistent Organochlorine Pollutants in High-Moor Peats of the Arkhangelsk Region

The results of a study of the contamination of a peat deposit of a representative oligotrophic bog complex (Primorsky district of the Arkhangelsk region) with persistent organic pollutants of polychlorobenzenes and pentachlorophenol are presented. Data on the quantitative content, composition and depth distribution of organochlorine pollutants have been obtained. The maximum amounts of polychlorobenzenes, pentachlorophenol and other chlorinated phenols in the upper 40-centimeter aerated layer of the peat deposit, the formation of which coincides with the period of “chlorine chemistry”, have been established. In addition, the presence of polychlorobenzenes and pentachlorophenol was revealed in all horizons of the upper meter layer of the peat deposit, which indicates their vertical migration in the peat body.

Diel vertical migration and seamount stepping stones promote species connectivity from coastal to offshore insular systems in the Tropical Southwestern Atlantic

AbstractThe recruitment of marine species in isolated oceanic island systems can be challenged by prevailing currents, as exemplified by the Tropical Southwestern Atlantic. In this region, the Fernando de Noronha ridge hosts several seamounts, the Rocas Atoll and the Fernando de Noronha Archipelago, which are home to great marine biodiversity. However, along the ridge, the central branch of the South Equatorial Current (cSEC), flowing westward, poses a challenge to the recruitment of organisms toward Fernando de Noronha. To unveil critical insights into the intricate processes shaping biodiversity in these insular ecosystems, we use a dispersal Lagrangian tool to explore the role of diel vertical migration (DVM) to depth strata influenced by the South Equatorial Undercurrent (SEUC), which flows eastward bellow the cSEC, in shaping species dispersal and metacommunity dynamics. Our results show that while not a direct journey, the DVM into SEUC‐influenced strata increases the possibility that the seamounts and the Rocas Atoll act as stepping stones between the continental shelf and Fernando de Noronha. Propagules of organisms originating primarily from the continental shelf are transported to the western seamounts of the ridge. Upon reaching the western seamounts, organisms can find suitable habitats to recruit. The progeny of these communities that migrate to SEUC‐influenced strata have the opportunity to reach suitable habitats at the Rocas Atoll and the Eastern seamounts, ultimately connecting to the Fernando de Noronha archipelago. These results provide scientific fundaments for the development of a functional network of marine protected areas in the Tropical Southwestern Atlantic.

Analysis of nitrogen migration and transformation in the typical deep and large reservoir of the Lancang River — Evidence from nitrogen and oxygen isotopes

The environmental effect resulting from dam construction and the formation of large reservoirs has long been a topic of significant concern. While current research at a macro scale provides a well understanding regarding the evolution of nitrogen nutrient status in river-reservoir ecosystems, the vertical migration and transformation characteristics of nitrogen in reservoirs under changing runoff remain less defined. This study centers on a typical deep reservoir along the Lancang River-Nuozhadu (NZD) Reservoir in April and December. The monitoring reveals a distinct vertical stratification phenomenon in the NZD Reservoir in the vertical profile in April, which can be categorized into a mixed layer (ML) (0–5 m), a thermocline layer (TL) (5–40 m), and an isothermal layer (IL) (>40 m) based on the water temperature. However, little stratification in the profile is occurred in December. The results of nitrogen and oxygen isotopes in April indicate that the biochemical process of nitrogen in the NZD Reservoir is predominantly driven by nitrification. However, different nitrogen biochemical processes are coupled in various stratified regions in the vertical direction. In the ML, simultaneous assimilation of ammonia nitrogen by phytoplankton occurs. In the TL, there is a process of oxidation and decomposition of particulate organic nitrogen due to a significant stratification effect and an extended hydraulic retention time. In the region of minimal dissolved oxygen (30–40 m), simultaneous denitrification may take place. In December, the main process is nitrogen assimilation in reservoir surface (ML). Statistical analysis of environmental factors highlights water temperature (T) and dissolved oxygen (DO) as crucial environmental factors influencing nitrogen migration and transformation within the reservoir. This study suggests that in deep reservoirs experiencing vertical thermal stratification, the characteristics of DO and nitrogen migration and transformation exhibit significant vertical spatial heterogeneity. This phenomenon may lead to diverse ecological environmental effects. Future efforts should focus on enhancing the fine monitoring of stratified water bodies in deep and large reservoirs and analyzing the ecological environmental effects of material cycling in greater detail.

Quantifying microplastics in sediments of Jinzhou Bay, China: Characterization and ecological risk with a focus on small sizes

Small-sized microplastics (MPs) pose greater ecological toxicity due to their larger surface area, which makes them more likely to act as carriers for other pollutants and to be ingested by aquatic organisms. However, traditional visual analysis often neglects small-sized MPs and their associated ecological risk. This study utilized Laser Direct Infrared (LDIR) spectroscopy and traditional visual analysis to examine MPs in 31 sediment samples from Jinzhou Bay, a typical semi-enclosed bay located at the economic center of Dalian, China. The results showed significant heterogeneity in MP distribution, with averages of 1192 and 2361 items/kg dry weight reported by visual analysis and LDIR spectroscopy, respectively. LDIR spectroscopy identified MPs as small as 10 μm, with the majority of MPs (89.21 %) within the 10–250 μm range, and a significant proportion (46.45 %) between 10 and 50 μm among them. However, visual analysis was limited to detecting MPs >50 μm, and significant portions were identified between 50 and 100 μm (49.36 %) and 100–250 μm (31.01 %), missing a substantial fraction of smaller MPs. The predominant polymers identified were polyamide (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and acrylonitrile butadiene styrene (ABS). LDIR spectroscopy demonstrated a strong positive correlation between MP abundance and clay content, a relationship not observed with traditional visual analysis. The Potential Ecological Risk Index (PERI) indicated that over 87 % of sites posed an extremely high risk according to LDIR spectroscopy, compared to 51 % by traditional visual analysis. These discrepancy underscores the underestimation of ecological risks by traditional methods, particularly for small-sized MPs. High-risk polymers such as polyvinyl chloride (PVC), ABS, and polyurethane (PUR) significantly influenced PERI values. These findings highlight the critical need for precise identification and thorough risk assessment of small-sized MPs in environmental studies and offer insights for understanding of MP vertical migration in aquatic environments, particularly in the context of co-settlement with sediments.

Resolving abrupt frontal gradients in zooplankton community composition and marine snow fields with an autonomous Zooglider

AbstractAn autonomous Zooglider navigated across the California Current Front into low salinity, minty waters characteristic of the California Current proper in both summers of 2019 and 2021. Diving to 400 m depth, Zooglider transited another near‐surface frontal gradient somewhat inshore. These frontal gradients were generally associated with changes in intensity, size composition, and Diel Vertical Migration responses of acoustic backscatterers. They were also associated with pronounced changes in zooplankton community composition, as assessed by a shadowgraph imaging Zoocam. Zoocam detected a decline in concentrations of copepods, appendicularians, and marine snow in the offshore direction, and an overall shift in community structure to a higher proportion of carnivorous taxa (and, in 2019, of planktonic rhizaria). No taxon was consistently elevated at all the peak frontal gradients, but appendicularians, copepods, and rhizarians sometimes showed front‐related increases in concentration. Such frontal gradient regions represent relatively abrupt transitions to different communities of planktonic organisms and suspended marine snow particles, with consequences for predator–prey relationships and the dominant vectors of particle export into subsurface waters.

Quantifying the mineral magnetic signature of petroleum systems and their source rocks: a study on the Inner Moray Firth, UK North Sea

SUMMARY This study aims to expand on existing connections between magnetic minerals and hydrocarbons within petroleum systems. Previous studies have focussed on single-source petroleum systems whereas this study, for the first time, analyses a multi-source petroleum system to investigate potential correlations between different kerogen type source rocks and magnetic minerals. To do this, the study investigates the magnetic mineral characteristics of the Inner Moray Firth (IMF), UK North Sea, through room-, low- and high-temperature techniques, and correlates this to published basin and petroleum systems modelling results that show a three-source hydrocarbon mix. Magnetic mineral analysis identifies extensive evidence for magnetite, goethite and siderite, alongside more minor lepidocrocite and iron sulphides. Although we find that magnetite is ubiquitous within the IMF, its abundance is relatively low, and, in contrast, the relatively magnetically weak goethite is more likely the most abundant magnetic mineral throughout the IMF. In agreement with previous studies, we find magnetic enhancement at oil-water contacts (OWCs); however, here, we identify two different magnetic enhancement processes at OWCs in wells, which are dependent on the amount of sulphur available in the local environment. Wells with low levels of sulphur have increasing levels of magnetite towards the OWC, with the magnetic enhancement occurring at the top of the water-saturated section. Sulphur-rich environments display an increase in iron sulphides near the OWC at the bottom of the oil-saturated sediments. Additionally, we confirm the presence of siderite as indicator of upward vertical migration. Combining with petroleum system model predictions, we find direct links between iron hydroxide presence and Type I and II–III kerogen source rocks, and iron sulphide presence with Type II kerogen source rocks. This study shows the potential for further utilization of magnetic mineral analysis within hydrocarbon exploration and petroleum system definition.

Construction of dual driving force in carbon nitride for highly efficient hydrogen evolution: Simultaneously manipulating carriers transport in intra- and interlayer

Photocatalytic hydrogen evolution is widely recognized as an environmentally friendly approach to address future energy crises and environmental issues. However, rapid recombination of photo-induced charges over carbon nitride in lateral and vertical direction hinder this process. Herein, we proposed an effective strategy involving the embedding of benzene rings and the intercalation of platinum atoms on carbon nitride for a controlled intralayer and interlayer charges flow. Modified carbon nitride exhibits a significant higher hydrogen evolution rate (6288.5 μmol/g/h), which is 42 times greater than that of pristine carbon nitride. Both experiments and simulations collectively indicate that the improved photocatalytic activities can be attributed to the adjustment of the highly symmetric structure of carbon nitride, achieved by embedding benzene rings to induce the formation of an intralayer build-in electric field and intercalating Pt atoms to enhance interlayer polarization, which simultaneously accelerate lateral and vertical charges migration. This dual-direction charges separation mechanism in carbon nitride provides valuable insights for the development of highly active photocatalysis.