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Mercury is a hazardous pollutant of global concern. While advances have been made in identifying the detrimental effects caused by Hg species in phytoplankton, knowledge gaps remain regarding the metabolomic perturbations induced by inorganic mercury (Hg(II)) and monomethylmercury (MeHg) in these organisms. Diatoms represent a major phytoplankton group essential in various global biogeochemical cycles. The current study combined targeted metabolomics, bioaccumulation, and physiological response assays to investigate metabolic perturbations in diatom Cyclotella meneghiniana exposed for 2 h to nanomolar concentrations of Hg(II) and MeHg. Our findings highlight that such exposures induce reprogramming of the metabolism of amino acids, nucleotides, fatty acids, carboxylic acids and antioxidants. These alterations were primarily mercury-species dependent. MeHg exposure induced more pronounced reprogramming of the metabolism of diatoms than Hg(II), which led to less pronounced effects on ROS generation, membrane permeability and chlorophyll concentrations. Hg(II) treatments presented distinct physiological responses, with more robust metabolic perturbations at higher exposures. The present study provides first-time insights into the main metabolic alterations in diatom C. meneghiniana during short-term exposure to Hg species, deepening our understanding of the molecular basis of these perturbations.

Drier and hotter conditions linked with anthropogenic climate change can increase wildfire frequency and severity, influencing terrestrial and aquatic carbon cycles at broad spatial and temporal scales. The impacts of wildfire are complex and dependent on several factors that may increase terrestrial deposition and the influx of dissolved organic matter (DOM) from plants into nearby aquatic systems, resulting in the darkening of water color. We tested the effects of plant biomass quantity and its interaction with fire (burned vs. unburned plant biomass) on dissolved organic carbon (DOC) concentration and degradation (biological vs. photochemical) and DOM composition in 400 L freshwater ponds using a gradient experimental design. DOC concentration increased nonlinearly with plant biomass loading in both treatments, with overall higher concentrations (>56 mg/L) in the unburned treatment shortly after plant addition. We also observed nonlinear trends in fluorescence and UV-visible absorbance spectroscopic indices as a function of fire treatment and plant biomass, such as greater humification and specific UV absorbance at 254 nm (a proxy for aromatic DOM) over time. DOM humification occurred gradually over time with less humification in the burned treatment compared to the unburned treatment. Both burned and unburned biomass released noncolored, low molecular weight carbon compounds that were rapidly consumed by microbes. DOC decomposition exhibited a unimodal relationship with plant biomass, with microbes contributing more to DOC loss than photodegradation at intermediate biomass levels (100-300 g). Our findings demonstrate that the quantity of plant biomass leads to nonlinear responses in the dynamics and composition of DOM in experimental ponds that are altered by fire, indicating how disturbances interactively affect DOM processing and its role in aquatic environments.

Humans increasingly dominate Earth's natural freshwater ecosystems, but biomass production of modified ecosystems is rarely studied. We estimate potential fish total standing stock in USA reservoirs is 3.4 billion (B) kg, and approximate annual secondary production is 4.5 B kg y-1. We also observe varied and non-linear trends in reservoir fish biomass over time, thus previous assertions that reservoir fisheries decline over time are not universal. Reservoirs are globally relevant pools of freshwater fisheries, in part due to their immense limnetic footprint and spatial extent. This study further shows that reservoir ecosystems play major roles in food security and fisheries conservation. We encourage additional effort be expended to effectively manage reservoir environments for the good of humanity, biodiversity, and fish conservation.

Our objective was to assess the effects of interactions between the native Percichthys trucha and both Salmo trutta and Oncorhynchus mykiss during the juvenile period. We conducted single and multipredator (conspecific and heterospecific) functional response (FR) experiments with Meridialaris chiloeensis as native prey and estimated the functional response ratio as a predator impact metric. Our results showed that all species have type II FR, with salmonids having a greater impact on prey than native fish. In multipredator experiments, O. mykiss had a greater negative impact on P. trucha than S. trutta. The individual feeding performance of P. trucha was better under conspecific than heterospecific conditions. This study shows that the vulnerability of juvenile P. trucha to salmonid competition could be a real threat in Patagonian lotic environments. [ABSTRACT FROM AUTHOR]

\nHighlightsIn this paper, we used the polyphasic approach combining 16S rRNA gene phylogenies, identity (p-distance), 16S-23S ITS secondary structures, and morphological and habitat analyses to describe two new genera of Leptolyngbyaceae, Pseudoleptolynbgya G.S. Hentschke gen. nov. (based on LEGE 16533 and LEGE 16651) and Leptolyngbyopsis G.S. Hentschke gen. nov. (based on LEGE 16524). These strains were sampled from freshwater environments at Figueira da Foz, Monchique and Coimbra, Portugal. Both genera are morphologically and ecologically identical to Leptolyngbya and can only be distinguished from it by molecular analyses. Based on morphological and ITS secondary structure analyses we describe two species of Pseudoleptolyngbya, P. figueirensis and P. monchiquensis. P. figueirensis differs from P. monchiquensis by the denser arrangement of the trichomes, the presence of firm sheaths, the common formation of shorter trichomes (up to 30 cells), and the olive or yellowish-green cell content, which is darker in P. monchiquensis. Moreover, the macroscopic appearance of P. figueirensis is a dense brownish mat, while P. monchiquensis is less dense and reddish. 16S rRNA gene sequences of Arthronema africanum CCALA020 are > 99% identical to Leptolyngbya boryana PCC6306, so we transfer A. africanum to Leptolyngbya, as L. africanoidea. Pseudoleptolyngbya gen. nov. and Leptolyngbyopsis gen. nov. are described.Arthronema is placed in synonymy with Leptolyngbya.Pseudoleptolyngbya gen. nov. and Leptolyngbyopsis gen. nov. are described.Arthronema is placed in synonymy with Leptolyngbya. [ABSTRACT FROM AUTHOR]

The Trebouxiophyceae is a widespread and species-rich green algal class encompassing mostly coccoid algae with a simple spherical, ovoid or ellipsoidal outline. However, some poorly sampled lineages have evolved more elaborate shapes or even complex thalli, adding to the morphological diversity of the class. By investigating new and previously established strains, this study expands the range of morphologies exhibited by the class members by uncovering a clade of croissant-like trebouxiophytes. Phylogenetic analyses inferred from nuclear 18S rDNA and chloroplast rbcL sequences confirmed the monophyly of the 'microcroissant' clade, which we propose to be classified as a new family, Ragelichloridaceae. This family includes two novel genera, Ragelichloris and Navichloris, and the previously described Thorsmoerkia. The position of Ragelichloridaceae within Trebouxiophyceae stayed unresolved but chloroplast phylogenomics showed that the family belongs to the broader incertae sedis group that also includes Xylochloris and Leptosira. In addition, our study showed that the similar morphotype-bearing genus Chlorolobion, previously classified within Chlorophyceae, is a genuine trebouxiophyte, potentially related to Ragelichloridaceae. Highlights: A new family-level clade uncovered within the Trebouxiophyceae. Two new genera, Ragelichloris and Navichloris, are described. The genus Chlorolobion is shown to be a trebouxiophyte. [ABSTRACT FROM AUTHOR]

Karst freshwater ecosystems are considered biodiversity hotspots, highlighting their sensitivity and vulnerability to environmental change. However, our understanding of the distribution and ecology of macroinvertebrates in lotic karst habitats is still incomplete. Therefore, to fill the knowledge gaps, the current study was conducted in the Dinaric and Carpathian–Balkan Mountains in Serbia, Southeastern Europe. We studied aquatic macroinvertebrates and their relationship with environmental parameters at 25 sampling sites in three habitat types (springs, the upper reaches, and tufa barriers) in 12 rivers and streams in Serbia, seasonally, between 2019 and 2022. We recorded 85,072 individuals within 206 taxa. Most environmental variables were comparable among the three habitat types, which most probably resulted in comparable abundance and diversity of benthic macroinvertebrates. However, taxa richness was lower in springs compared to upper reaches and tufa barriers. Environmental parameters had a greater impact than spatial effects on shaping the macroinvertebrate community. Moreover, IndVal analysis revealed a list of 30 indicator taxa associated with specific habitat types. We emphasized that highly specialized species support vulnerable functions in high-diversity karst freshwater ecosystems. Therefore, this study establishes a scientific foundation for implementing effective management strategies for these unique aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems have been severely disturbed in recent years. However, our understanding of the ecosystem-level changes within freshwater food webs under complex disturbances is still limited. To address this knowledge gap, we took Dongting Lake as a case study, which has undergone significant environmental changes. We established Ecopath models for Dongting Lake in 1997, 2013, and 2021, and validated them using stable isotope-determined trophic levels. Our focus was on describing the structure and maturity of the ecosystem, identifying key species, and quantifying energy flows. The verification result showed that the models were acceptable. The model outputs revealed a significant decline in the average energy transfer efficiency of Dongting Lake. The food web maturity of Dongting Lake decreased and subsequently increased in these three representative periods. Simultaneously, the food web structure was successively simplified over time. Moreover, the identification of keystone species revealed the significance of Zooplankton, Other fish, Silurus asotus, and Molluscs within the ecosystem. Overall, our results offer a scientific underpinning for the effective management and conservation of freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Diapause is a survival strategy for freshwater crustaceans in the genus Daphnia that involves a genetically encoded inhibition of organism growth, development and reproduction. While the environmental triggers for Daphnia to produce diapause‐destined embryos and those that induce hatching are well documented, the influence of environmental challenges during different diapause sub‐phases remains unexplored.In this study, we exposed diapause‐destined embryos of Daphnia magna to different temperatures and light conditions during designated diapause sub‐phases.Our results underscore the importance of the maternal environment for the embryos that are in preparation for diapause. Moreover, we demonstrate a period of obligate developmental arrest during which reinitiation of development cannot be triggered. Additionally, we illustrate the embryos' ability to adjust hatching in response to environmental changes during the hatching process.This study reveals the inherent developmental pattern in Daphnia embryos as they progress through diapause and their adaptability to environmental changes. [ABSTRACT FROM AUTHOR]

Climate variability on centennial timescales has often been linked to internal variability of the Atlantic Meridional Overturning Circulation (AMOC). However, due to the scarceness of suitable paleoclimate proxies and long climate model simulations, large uncertainties remain on the magnitude and physical mechanisms driving centennial‐scale AMOC variability. For these reasons, we perform a systematic multi‐model comparison of centennial‐scale AMOC variability in pre‐industrial control simulations of state‐of‐the‐art global climate models. Six out of nine models in this study exhibit a statistically significant mode of centennial‐scale AMOC variability. Our results show that freshwater exchanges between the Arctic Ocean and the North Atlantic provide a plausible driving mechanism in a subset of models, and that AMOC variability can be amplified by ocean–sea ice feedbacks in the Labrador Sea. The amplifying mechanism is linked to sea ice cover biases, which could provide an observational constraint for centennial‐scale AMOC variability. Plain Language Summary: Changes in ocean circulation are often proposed as drivers of natural variations of the Earth's climate on timescales of centuries. However, it is unclear how strong these natural variations of the circulation strength, called internal variability, are in the real world, because reconstructions from the past climate are sparse and climate models are expensive to run for these long timescales. Here, we compare how the latest generation of climate models simulate internal variability of the Atlantic Meridional Overturning Circulation (AMOC)—the ocean circulation that is often thought to be responsible for Europe's comparatively mild climate—on timescales of 100–250 years. We find that many models have stronger variability on these timescales than what would be expected simply from random noise. In several models, AMOC variability appears to be driven by the release of fresh water from the Arctic Ocean and amplified by intermittent sea ice cover in the North Atlantic. However, this amplification only occurs if a model simulates a too extensive sea ice cover in winter. This mechanism shows that sea ice cover—which is easily observable—could be used to constrain variability of the AMOC on timescales longer than the observational record. Key Points: We present a robust multi‐model comparison of internal centennial‐scale AMOC variability in state‐of‐the‐art climate modelsA robust mechanism of Arctic–North Atlantic freshwater exchange is identified only in models that use the NEMO ocean componentSea ice cover biases in convective regions of the North Atlantic amplify AMOC variability and could provide an observational constraint [ABSTRACT FROM AUTHOR]

Prey can use several information sources (cues) to assess predation risk and avoid predation with a variety of behavioural responses (e.g., changes in activity, foraging, vigilance, social behaviour, space use, and reproductive behaviour). Direct cues produced by predators and indirect cues from environmental features or conspecific and heterospecific prey generally provide different types of information about predation risk. Despite widespread interest in understanding behavioural antipredator responses to direct and indirect cues, a clear general pattern of relative response strength across taxa and environments has yet to emerge. We conducted a meta‐analysis of studies (N = 113 articles and 999 effect sizes taken from a search of over 7500 articles) testing behavioural responses to direct and indirect cues of predation risk, and their combination, across terrestrial and aquatic ecosystems. We further contrasted if effects were moderated by ecosystem type (terrestrial, marine, or freshwater), cue source (predator, conspecific, heterospecific, or environmental feature), or sensory modality (visual, auditory, or chemosensory). Overall, there were strong effects of risk cues on prey behaviour. We found that prey responded more strongly when both types of cues were presented together compared with either cue in isolation, which was driven by changes in prey activity levels but not other behaviours. There was no general pattern in response strength to direct compared with indirect cues. Responses to these cues were moderated by interactions between environment, cue source, and cue sensory modality (e.g., visual cues elicited stronger responses than other modalities, and responses to conspecific chemosensory cues were stronger than those to predator chemosensory cues in aquatic systems). These results suggest that rather than a broad framework of direct and indirect cues, the specific context of the system should be considered in tests and predictions of how prey respond to risk to elucidate general patterns of antipredator responses. [ABSTRACT FROM AUTHOR]

ABSTRACT Motivation Main Types of Variables Contained Spatial Location and Grain Major Taxa and Level of Measurement Freshwater ecosystems have been heavily impacted by land‐use changes, but data syntheses on these impacts are still limited. Here, we compiled a global database encompassing 241 studies with species abundance data (from multiple biological groups and geographic locations) across sites with different land‐use categories. This compilation will be useful for addressing questions regarding land‐use change and its impact on freshwater biodiversity.The database includes metadata of each study, sites location, sample methods, sample time, land‐use category and abundance of each taxon.The database contains data from across the globe, with 85% of the sites having well‐defined geographical coordinates.The database covers all major freshwater biological groups including algae, macrophytes, zooplankton, macroinvertebrates, fish and amphibians. [ABSTRACT FROM AUTHOR]

Nitrite is a ubiquitous compound found across aquatic systems and an intermediate in both the oxidative and reductive metabolisms transforming fixed nitrogen in the environment. Yet, the abiotic cycling of nitrite is often overlooked in favor of biologically mediated reactions. Here we quantify the apparent acid dissociation constant (pKa) between nitrous acid and its conjugate base nitrite in both freshwater and seawater systems across a range of environmentally relevant temperatures (5–35°C) using potentiometric‐based titration. In freshwater, we measured a pKa,NBS of 3.14 at 25°C and a pKa,T of 2.87 for seawater at the same temperature. We quantify substantial effects of both salinity and temperature on the pKa, with colder and fresher water manifesting higher values and thus a greater proportion of protonated nitrite at any given pH. Because nitrous acid is unstable and decomposes to nitric oxide, the implications for the nitrous acid dissociation constant on ecosystem function are broad. [ABSTRACT FROM AUTHOR]

Atlantic salmon Salmo salar typically enter fresh water several months prior to spawning and just as pools can provide areas of refuge in river systems, lakes may also provide important refuge habitat during the spawning migration. Using acoustic telemetry we examined the spatial and temporal movements of wild and a ranched strain of Atlantic salmon in a freshwater lake where the main spawning areas were located upstream of the lake. Over the study period (2011–2014), returning adult wild salmon spent an average of 228 days in fresh water and 90% of that time in the lake. On entering the lake, most wild salmon moved quickly to the northern part of the lake, close to the main inflow, spending an average 76% of the time in this location. The average number of days wild fish were absent from the lake during the main spawning period varied between years, ranging from 10 to 26 days for females and 32 to 35 days for males. Seventy four per cent (17/23) of salmon spawners returned to the lake and two salmon subsequently died in the lake post‐spawning. Atypically, two salmon were resident in the lake for the whole period in 2013/14. During the study, wild salmon were detected at depths within the top 5 m for 73% of the time. Median depths post‐spawning were greater than in the pre‐spawning period, when salmon were found to spend extensive periods at depths in excess of 10 m. In July 2013, when the lake was stratified, thermal regulation behaviour was observed in wild salmon, whereby salmon moved to cooler deeper water when water temperatures at 1 m exceeded 20°C. In contrast to wild salmon, the majority of ranch salmon returned to the traps downstream of the lake prior to the spawning period, which would be expected as they were released as smolts below the freshwater lake. Ranch fish spent an average 80% of the time in the vicinity of receivers in the south of the lake and an average 98% of the time within the top 5 m. However, two ranch females were resident in the lake until the following spring and one ranch female moved upstream into the river during the spawning period. Clearly, in this catchment the lake provides an important habitat for migrating adult salmon. In the context of climate change, where thermal and hydrological regimes in rivers are expected to change in response to changes in air temperature and precipitation patterns, the availability of deep lakes that stratify in the summer and cool water refuges in river systems is likely to play a key role in the sustenance and conservation of salmonid species. Information about the migration patterns of Atlantic salmon in undisturbed freshwater systems may also assist in resolving issues associated with fish passage in impacted rivers and inform management decisions. [ABSTRACT FROM AUTHOR]

Many primary consumers in freshwater, marine and terrestrial systems are ectotherms (e.g. zooplankton and insects), whose metabolisms, and therefore nutritional demands, are modulated by temperature. Further, nutrient availability largely influences the quality of resources consumed by these organisms, and hence affects whether nutritional demands of consumers are fulfilled. From these considerations, a crucial question arises: how do temperature and nutrient availability together modulate trophodynamics at the basis of food webs? Addressing this question for zooplankton and insects is essential since these consumers are the most abundant metazoans on Earth, and they link primary production to higher trophic levels. Here, we synthesize the existing literature and offer avenues to guide future scientific endeavours. We highlight that the vast majority of studies on the combined influence of temperature and nutrient availability published to date focus on at least one of the following research topics: 1) metabolic requirements of ectotherms; 2) feeding behaviour; 3) eco‐evolutionary processes; and 4) trophodynamics. We pose that further advances in this field of research may provide a robust understanding of how modulations of consumer metabolic requirements and resource quality define consumer–producer interactions across marine, freshwater and terrestrial ecosystems. This research effort would enable to combine the fields of Ecological stoichiometry and of Metabolic theory of ecology, and create an integrated approach, which we propose to call Nutritional thermal ecology. [ABSTRACT FROM AUTHOR]

To evaluate the effect of glyphosate, 2,4-D, and their combination on daily dissolved oxygen saturation percentage (DO%) in freshwater, two separate outdoor mesocosm experiments were performed. The experiments were conducted under contrasting conditions: one in clear mesotrophic status lasting 23 days, and the other in organic turbid eutrophic conditions lasting 21 days. Single concentrations were applied as commercial formulations at two levels. Samples of phytoplankton (micro + nano, picoeukaryotes, picocyanobacteria), mixotrophic algae, and heterotrophic bacteria were analyzed at four sampling dates. Increases in DO levels were consistently observed in both clear and turbid systems treated with glyphosate, either alone or in combination with 2,4-D, suggesting that DO is a sensitive indicator. DO increased in all glyphosate treatments. DO increases reflected different changes in phytoplankton communities, increasing with micro + nano phytoplankton abundance in the clear experiment but with increased picocyanobacteria in the turbid. In contrast, 2,4-D reduced DO levels, but only in the turbid system, where micro + nano phytoplankton abundance decreased. The clear system showed greater resilience by restoring DO levels before the turbid one. Mainly additive effects of the herbicide mixture were observed on dissolved oxygen levels (DO%), but a distinct synergistic decrease was detected within turbid systems, underscoring the importance of considering turbidity as a contributing factor in the freshwater impacts of herbicides. [ABSTRACT FROM AUTHOR]

Shallow lakes and ponds play a crucial role in the processing of carbon and other nutrients. However, many lakes and ponds worldwide are affected by climate change and nutrient pollution. How these pressures affect the emission of the greenhouse gas nitrous oxide (N2O) is unclear. Warming and eutrophication are expected to increase the production and emission of N2O in lakes and ponds, but changes in ecological structure and function may complicate these seemingly straightforward relationships. In this study, we used the world's longest running, mesocosm‐based, freshwater climate change experiment to disentangle the effect of nutrient enrichment and warming on N2O emissions. We gathered a large dataset on N2O concentrations and ancillary variables, comprising three sampling campaigns between 2011 and 2020 and a total of 687 individual mesocosm measurements. Our results demonstrated that nutrient enrichment increased N2O emissions, while warming (+2.5–4.0°C and +3.75–6.0°C) had no discernable effect. Our study indicates that curtailing nitrogen influxes into lakes and ponds is the most effective strategy to minimize N2O emissions, and while warming may influence N2O emissions, it does not appear to be a direct driver. These findings underscore the importance of prioritizing nitrogen mitigation efforts to curb N2O emissions from shallow lakes and ponds. [ABSTRACT FROM AUTHOR]

In a time of growing climate crisis, and despite the global warming trend, Israeli citizens routinely enjoy a regular constant supply of clean fresh water thanks to local desalination plants. Establishment of the desalination plants has become a model of water management for many countries in an era of growing climate crisis. At the same time, Israel's water sector is faced with challenges and threats related to earthquakes, various states of warfare, and security confrontations. In such times of emergency, Israel's water sector is particularly vulnerable to disruptions of the water infrastructure and its adequate operation by both contamination of the water sources and damage to the desalination plants. This study examines the challenges of the Israeli water sector that require it to contend with these emergency situations in an era of reliance on desalination plants. The research findings lead to the conclusion that public policy on managing the water sector, manifested in the development and establishment of water desalination plants, has resolved Israel's water crisis, put an end to its dependency on the amount of precipitation and on natural water sources, and allowed for an increase in water production to match the rise in consumption. Nonetheless, as successful as this public policy may be, it does not consider the possibility of extreme scenarios and does not develop the entire range of steps necessary to confront them, and thus it undermines the ability of the Israeli water sector to provide its citizens with water in times of emergency. [ABSTRACT FROM AUTHOR]

Gobioid fishes (Teleostei) are renowned for their remarkable species diversity in marine and freshwater environments, making their evolutionary history a fascinating study subject. Among their oldest known fossils is the small-sized freshwater goby ‘Gobius’ gracilis from the Lower Oligocene of Central Europe, which has not undergone a detailed investigation since its first description. Here, we present a comprehensive re-analysis of ‘G.’ gracilis using type specimens and new material from museum collections. We show that this species possesses a unique combination of traits, leading to the establishment of a new genus, †Laubeichthys gen. nov. Phylogenetic analyses using Bayesian Inference (BI) recover †Laubeichthys gen. nov. as a stem member of the extinct family †Pirskeniidae and suggest a sister relationship between the family Thalasseleotrididae (ocean sleepers) and †Laubeichthys gen. nov. + †Pirskeniidae. Maximum parsimony analyses do not contradict such a relationship, but the trees are less resolved. Today, the Thalasseleotrididae includes four marine species that are restricted to the Southwest Pacific. In contrast, †Pirskeniidae and †Laubeichthys gen. nov. inhabited freshwater environments in Central Europe. Our findings provide new insights into the evolutionary history and historical biogeography of gobioid fishes and highlight the dynamic nature of their past diversity and distribution. [ABSTRACT FROM AUTHOR]

Predicting the response of aquatic species to environmental contaminants is challenging, in part because of the diverse biological traits within communities that influence their uptake and transfer of contaminants. Nanoplastics are a contaminant of growing concern, and previous research has documented their uptake and transfer in aquatic food webs. Employing an established method of nanoplastic tracking using metal-doped plastics, we studied the influence of biological traits on the uptake of nanoplastic from water and diet in freshwater predators through two exposure assays. We focused on backswimmers (Anisops wakefieldi) and damselfly larvae (Xanthocnemis zealandica) - two freshwater macroinvertebrates with contrasting physiological and morphological traits related to feeding and respiration strategies. Our findings reveal striking differences in nanoplastic transfer dynamics: damselfly larvae accumulated nanoplastics from water and diet and then efficiently eliminated 92% of nanoplastic after five days of depuration. In contrast, backswimmers did not accumulate nanoplastic from either source. Differences in nanoplastic transfer dynamics may be explained by the contrasting physiological and morphological traits of these organisms. Overall, our results highlight the importance and potential of considering biological traits in predicting transfer of nanoplastics through aquatic food webs. [ABSTRACT FROM AUTHOR]

Coilia nasus are an important fish resource in the Yangtze River, and the Yangtze River Estuary is a crucial migration pathway for them. In this study, we used otolith microchemistry to analyze the strontium/calcium (Sr/Ca) ratios and Sr contents in the sagitta otolith of C. nasus from the south branch (SB) and north branch (NB) of the Yangtze River Estuary and obtained the diversity of migration patterns and spawning ground distribution for C. nasus. The results indicate that C. nasus from both branches include two types of habitat history: freshwater (F)–brackish water (B) (Type I) and F-B seawater (S) (Type II), with Type I being dominant at 62.50% in both branches. The C. nasus from the SB comprise six migration patterns, while that from the NB has seven migration patterns. The C. nasus from both branches hatch in F habitats. At the time of capture, the C. nasus from the SB predominantly remain in F, accounting for 62.5%, while C. nasus from the NB primarily stay in B, accounting for 87.5%. Throughout the migration process, C. nasus from both branches switch between different habitats, with C. nasus from the NB exhibiting more frequent transitions between F and B, showing a greater reliance on the estuarine brackish habitat. The radius of the first blue region near the core (Lf) and freshwater coefficient (Fc) of the otolith for C. nasus from both branches are divided into three groups: long-distance freshwater dependence (LD), medium-distance freshwater dependence (MD), and short-distance freshwater dependence (SD), with the LD only appearing in the SB, while the NB is primarily represented by MD. There is a correlation between the differences in Lf among different groups of C. nasus and the differences in the distance from the spawning grounds of C. nasus in different sections of the Yangtze River to the estuary (DYRE), reflecting the distribution pattern of C. nasus spawning grounds in different sections of the Yangtze River. This study provides theoretical guidance for the protection of migration pathways and maintenance of spawning grounds for C. nasus, which have significant practical value in the precise management of C. nasus resources in the Yangtze River Estuary. [ABSTRACT FROM AUTHOR]

Our study focused on freshwater fungal diversity, an important aspect in assessing the ecology of aquatic ecosystems. We carefully explored the diversity and influencing factors of culturable fungi across Dianchi Lake, Fuxian Lake, Xingyun Lake, and Yangzonghai Lake in Yunnan Province, China. Through fungi culture, morphological characterization, and ITS sequence analysis, we identified a total of 565 isolates belonging to 405 species across 133 genera. The diversity indices viz. H′, D, and J were evaluated for fungal diversity across the lakes. Interestingly, although diversity indices were highest during summer and at Yangzonghai Lake, no significant differences in fungal community diversity were observed between seasons and regions. Water variables were analyzed and indicated that changes with rapid fluctuations in temperature, pH, and dissolved oxygen likely influence fungal diversity. These findings significantly contribute to our understanding of fungal communities within plateau lake ecosystems, thereby aiding in managing and conserving vital aquatic resources. [ABSTRACT FROM AUTHOR]

Using the method of gravimetric and electrochemical measurements, the corrosion rate of St3 steel in the water basins of the Takhtakerpi and Shemkirchay hydroelectric power stations has been determined. To establish the expected corrosivity of water, the chemical composition and some physicochemical parameters of the above waters have been determined. As a result of long-term measurements carried out over one year, it has established that steel in the water basins of the Takhtakerpi and Shemkirchay hydroelectric power stations corrodes at a rate of 0.04 g/m² h and (0.07÷0.08) g/m² h, respectively. And in the atmosphere of these hydroelectric power plants, steel corrodes at a low rate, approximately an order of magnitude lower. Analysis of water taken from these hydroelectric power stations showed a very low content of corrosive ions, the concentration of which, especially in the Shemkirchay reservoir, corresponds to spring water. By taking polarization curves it has been established that the rate of steel corrosion is controlled by the concentration of dissolved oxygen in water. [ABSTRACT FROM AUTHOR]

Native to Central and Eastern Europe, the euryhaline pikeperch Sander lucioperca can acclimatize to elevated salinity levels (e.g., up to 30‰), but it remains unknown whether their invasive populations use this ability to inhabit and/or disperse through brackish waters, such as estuaries and inshore areas. To test whether invasive pikeperch show a propensity to move into areas of relatively high salinity, their spatial use and movement patterns (e.g., home range, distances moved, and movement rates) were assessed using acoustic telemetry in the upper River Thames estuary, southeast England. Analyses revealed that individual pikeperch were capable of moving relatively long distances in a short time (e.g., speeds up to 70 m min−1), with movement patterns associated more with tidal state and elevation at the water surface (both assumed to relate to changes in salinity) than diurnal changes. There were no recorded movements of any pikeperch into the more saline, downstream waters of the estuary where salinity levels were recorded to over 40‰, with the mean salinity in the most downstream area where pikeperch were detected being 1.39‰ (range of logger: 1.22–1.71). The results suggest that these pikeperch did not use high salinity waters when less saline waters were available, and thus the risk that they will use to move through high salinity areas to expand their invasive range appears low. Accordingly, efforts to minimize risks of the further dispersal of invasive pikeperch populations can focus on control and containment programmes within fresh waters. [ABSTRACT FROM AUTHOR]

State Wildlife Action Plans (SWAPs), including lists of Species of Greatest Conservation Need (SGCN), outline state strategies for protecting species and habitats in the United States. In developing the current, second revision SWAPs, states are increasingly pursuing coordinated landscape conservation approaches. Analyzing SGCN lists in the first revision SWAPs, we found evidence that they already support multistate conservation. Most states address a common set of vertebrate and invertebrate groups, include most of the imperiled species from these groups, do not prioritize endemics over non‐endemics, and often include most imperiled species that are shared with neighboring states. Also, a regional SGCN coordination effort was successful. Although 65% of animals on each SGCN list were assessed as at elevated risk of extirpation by state authorities, only 43% of the combined national list were at elevated risk of global extinction. Over 40% of the combined animal SGCNs are considered globally apparently secure. Plants, snails, freshwater shrimps, and freshwater insects were poorly represented in SGCN lists. For the current SWAP revisions, we recommend improving foundational data on taxonomy, range‐wide distribution, and conservation status; expanded taxonomic coverage in SGCN lists; supporting existing and establishing new interstate initiatives; and diversifying funding mechanisms that target regional cooperation. [ABSTRACT FROM AUTHOR]

Fish recruitment is interannually variable and challenging to predict. Annual recruitment is often regionally synchronized among populations and identifying drivers of such synchrony may help shed light on recruitment dynamics. We investigated interannual variation of alewife Alosa pseudoharengus recruitment by estimating year-class strength for populations from three of the Laurentian Great Lakes (lakes Huron, Michigan, and Ontario) using annual assessment survey data from 1968 to 2022. We first determined the age when year-class strength was set for each dataset. We then used a mixed-modeling approach incorporating age, year-class, and sampling year to estimate year-class strength for each study lake. Thereafter, we evaluated regional synchrony in year-class strength across the three lakes and evaluated potential climatic drivers of synchrony. Our results suggest that alewife year-class strength is set by age-1. Our model-derived indices of alewife year-class strength were synchronized among the three lakes, and we identified spring-summer degree-days as a potential regional driver of synchrony. This analysis highlights the potential for strong influence of climatic conditions on fish recruitment in large freshwater systems. [ABSTRACT FROM AUTHOR]

The study investigates the impact of two different wind forcings on the surface ocean conditions of the Arabian Sea (AS) using the Regional Ocean Modelling System (ROMS) simulations. The wind forcings used in the ROMS simulations are the climatological Comprehensive Ocean-Atmosphere Data Set (COADS) winds and the Quik Scatterometer (QuikSCAT) satellite sea-winds. These two wind forcings are implemented and evaluated individually to assess their respective influences on the surface ocean conditions such as temperature, salinity, currents, heat fluxes, fresh water flux and diffusivity over the AS. The QuikSCAT winds are seen stronger (up to 2 m/s) over the AS and the wind stress curl is higher (up to 1.5 × 10− 7 N/m2) in the equatorial region as compared to the COADS winds. Both the simulations have replicated the overall pattern of the surface ocean conditions very well. The stronger QuikSCAT winds simulation has shown higher surface salinity (~ 2 psu) and freshwater fluxes compared to the weaker COADS winds simulation. Again, the strong winds from QuikSCAT have also increased the surface current (up to 0.2 m/s) and horizontal diffusivity in the southern and western boundary of the AS. The implementation of wind forcing provides valuable insights into the dynamics of the regional ocean system and its response to atmospheric conditions. Therefore, the implementation of COADS and QuikSCAT winds in the ROMS simulations will enhance our ability to accurately simulate and predict the behaviour of the surface ocean conditions of the AS. [ABSTRACT FROM AUTHOR]

The interconnectedness of adjacent freshwater and terrestrial ecosystems results in ‘tangled‐webs’, where the cross‐boundary exchange of materials results in energy flows that provide critical resources for ecosystem productivity. However, these energy flows can be disrupted by anthropogenic activities, resulting in modified ecosystem functioning. A ubiquitous anthropogenic activity in fresh waters is recreational angling. Five major angling activities can disrupt the structure of the ‘tangled‐web’ to produce an ‘angled‐web’ (a tangled food web that is modified by angling activities). (1) Fish stocking increases the number and species available to exploit, but the increased fish abundances can have strong top‐down effects and disrupt reciprocal prey subsidies. Following capture, fish are either (2) harvested or (3) released alive (‘catch‐and‐release0’); both can both drive eco‐evolutionary changes that can modify food‐web structure. Where fish are exploited using baited hooks, (4) the release of ‘ground‐bait’ is used as a fish attractant; its composition of novel protein and carbohydrate sources form novel trophic links in the food web and can accelerate eutrophication. Some angling styles also require (5) riparian and in‐stream vegetation to be cleared to minimise gear fouling, potentially modifying fish spawning and nursery areas. We suggest that each of these angling impacts (and their interactions) can contribute to transforming the ‘tangled web’ into an ‘angled‐web’, with the strength and direction of the transformation dependent on angling pressure, prevailing fishery practices, regulations and management, and the extent of the interaction effects of the activities. These interactions and their impacts will vary globally given angling methods, practices and regulations differ across the world. We argue that, in this era of substantial environmental change driven by climate change, habitat loss and nutrient enrichment of fresh waters, the extent to which angling impacts food webs should not be overlooked and underappreciated. We emphasise that when freshwater angling activities are poorly managed and/or unregulated, they can strongly modify the interconnectedness between terrestrial and freshwater food webs. [ABSTRACT FROM AUTHOR]

Severe problems of rising groundwater and secondary soil salinization demand holistic agricultural water management in canal command areas. Drip irrigation with alternate use of fresh and saline waters is an excellent irrigation approach to mitigate salinity stress caused by highly saline ground water and also to avoid soil sodicity hazards from canal water. Therefore, a study on cyclic mode conjunctive use of good quality surface water (SW) and highly saline ground water (GW) having average electric conductivity 0.3 and 7.6 dS m−1, respectively was carried out in wheat with five treatments of drip viz. 1SW1GW (1:1 :: SW:GW), 1SW2GW (1:2 :: SW:GW), 2SW1GW (2:1 :: SW:GW), SW (all SW), GW (all GW), and one treatment of conventional border -irrigation method (BI). Highest grain yield was observed in SW (2.99 t ha−1) in 2017–2018 and BI (3.83 t ha−1) in 2018–2019 season. However, yield of SW and BI were statistically at par in both seasons. Grain yield of 1SW1GW, in which only 50% freshwater was used was found statistically at par with SW and BI. Physical Water Productivity was highest for SW, amounting 9.34 and 14.13 kg ha−1.mm−1 during 2017–2018 and 2018–2019, respectively. Soil salinity build up was highest for GW and lowest for SW, whereas it was almost similar for BI and 1SW1GW. Thus, 1SW1GW showed added benefits as its grain yield was statistically at par with SW and BI along with 50% fresh water saving over SW and higher water productivity than BI for similar salinity levels. [ABSTRACT FROM AUTHOR]

Urbanisation poses numerous challenges to fresh water biodiversity, and installation of above-ground rainwater tanks on private properties is one important tool for addressing these challenges. In this paper, we used an online survey targeting a representative sample of 1291 urban residents to investigate their underlying capabilities, opportunities, and motivations for installation of above-ground rainwater tanks on their properties. Only 221 (17%) of the 1,291 respondents already had an above-ground rainwater tank installed on their property. By segmenting on behavioural variables, we found that those urban residents who currently did not have a water tank on their property were not homogeneous. We identified three audience segments, 'Supportive' (19%), 'Receptive' (59%) and 'Reluctant' (22%), each with their own unique driver and barrier combination to rainwater tank installation. Suitable leverage points and behaviour change tools (e.g. education, enablement, incentivisation) and message framing (environmental, community, or functional benefits) are identified for each segment. [ABSTRACT FROM AUTHOR]

This paper provides first information about possible occurrence of the myxosporean genus Kudoa in fish of the World Ocean and, in some cases, in associated freshwater bodies at different depths. An analysis of the theoretically assumed site preference by Kudoa of different habitat depths of their fish hosts in the World Fauna is made for the first time. It is revealed that all species of the myxosporean genus Kudoa can be found in coastal shelf zones, of which 90 species (70.8% of the total) occur exclusively in the shelf zone, and the hosts of 50 Kudoa species (39.4%) live in its shallowest part (down to 50 m). 16 species (12.6%) and 14 species (11%) of this genus can be found at depths from the shelf to 500 meters and 1000 meters, respectively. From 1 to 3 species of Kudoa can be encountered theoretically at 1500 m to 3000 m, which is from 0.8 to 2.4% of all known representatives of these parasites. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are among the most important in the world and provide essential functions and services to humans. In this study, we examine the roles of environmental and historical factors in explaining contemporary patterns of species richness. We investigated spatial patterns of species richness of freshwater crabs by compiling geographic distribution maps for 1271 species. We employed six environmental variables slightly correlated and non-collinear to test environmental hypotheses. At a global scale, we identified three regions characterized by particularly high species richness: in northern South America (Neotropical biogeographic realm), in the Western Ghats and Sri Lanka (Oriental), and southwestern China (Oriental). The best-fitting model that explained global richness variation included environmental hypotheses: Temperature-Speciation, ResourceAvailability, HabitatHeterogeneity and AnthropicImpact. We also observed a historical influence on the pattern of richness, with distinct sets of environmental predictors of richness across taxa and biogeographic realms. Our models suggest that freshwater crab richness is associated with by varying processes occurring within specific environmental and historical scenarios. In general, we documented a concentration of freshwater crab richness in areas heavily impacted by human activities. These findings hold implications for the conservation of this taxonomic group. [ABSTRACT FROM AUTHOR]

Background: The family Proalidae Harring & Myers, 1924, includes four genera and 53 species, distributed across all eight biogeographic realms and inhabiting various environments, including freshwater, saltwater and terrestrial environments. The genus Proales, the largest within Proalidae, encompasses 41 species characterised by diverse morphological traits. In Korea, the presence of Proalidae has been documented with five known species: Bryceella perpusilla Wilts, Martínez Arbizu & Ahlrichs, 2010, B. stylata (Milne, 1886), B. tenella (Bryce, 1897), Proales fallaciosa Wulfert, 1937 and Proalinopsis caudatus (Collins, 1872). New information: A new species, Proales amplus sp. nov., is the 42nd species within the genus Proales. This species exhibits unique morphological characteristics in the trophi, particularly in the epipharynx, which are distinctive enough to prevent misidentification with other Proales species. The habitus of the new species bears some resemblance to P. phaeopis Myers, 1933, sharing features, such as an elongated and fusiform body, two eyespots, a single foot pseudosegment, two short toes and the absence of a dorsal papilla between the toes. However, the epipharynx of the two species is markedly different. The unique epipharynx characteristic of this new species is unparalleled within the genus Proales. [ABSTRACT FROM AUTHOR]

Submarine groundwater discharge (SGD) plays a crucial role in nutrient budgets of coastal systems, encompassing both submarine fresh groundwater discharge (SFGD) and recirculated saline groundwater discharge (RSGD). Despite its significance, the specific importance of these components in mariculture bays has not been thoroughly assessed. Here, utilizing Ra isotopes and water‐salt mass balance model, we show that SFGD flux (1.1 ± 0.4 cm d−1) represented only 17% of the SGD in the Zhenzhu Bay, a typical mariculture bay along the South China Sea. Interestingly, the nutrient contribution from SFGD surpassed that from RSGD, accounting for 82% of the dissolved inorganic nitrogen (DIN) flux within the SGD. Analysis of the monthly satellite Chlorophyll‐a (Chl‐a) data confirmed that the decline in phytoplankton biomass can be linked to the limited dissolved silicate (DSi) transported by SFGD. Additionally, the elevated nitrogen to phosphorus ratio (241:1) and reduced silicon to nitrogen ratio (0.5:1) in SFGD compared to the Redfield ratio suggested that SFGD characterized by nitrogen excess and silica deficient, which likely played a role in transitioning from biogenic element constraints in coastal water. This shift may impact the proportions and functionality of the phytoplankton community, potentially mitigating water eutrophication. These findings underscore the significant influence of SGD on nutrient dynamics and the ecological environment in the Zhenzhu Bay. Plain Language Summary: Submarine groundwater discharge (SGD) is a significant process in coastal regions worldwide. Nutrients by SGD can disrupt the ecological balance of bays, altering nutrient structures and primary productivity in coastal ecosystems. However, this nutrient influx may exacerbate issues such as eutrophication and hypoxia in these waters. Although SGD acts as a significant nutrient source in the Zhenzhu Bay, there remains a scarcity of knowledge in distinguishing between submarine fresh groundwater discharge (SFGD) and recirculated saline groundwater discharge (RSGD), potentially resulting in overestimations of SGD. By utilizing Ra isotopes and a water‐salt mass balance model, we quantified the various components of SGD along with their nutrient fluxes. The study revealed that the persistent discharge of nitrogen‐contaminated fresh groundwater could eventually shift coastal waters from a nitrogen‐limited state to a phosphorus‐limited state. Moreover, the SFGD component under silicon‐limited conditions may restrict primary productivity particularly among freshwater diatom species. These findings contribute to enhancing our comprehension of how nutrients delivered by different SGD components impact marine ecosystems, but long‐term monitoring of SFGD and RSGD components is recommended to evaluate potential hazards and their influence on the ecological environment. Key Points: Nutrient fluxes from submarine fresh groundwater exceeded river by a factor of at least 3 timesSubmarine fresh groundwater discharge (SFGD) contributed more dissolved inorganic nitrogen than recirculated saline groundwater dischargeThe decline in phytoplankton biomass can be linked to the scarcity dissolved silicates in SFGD [ABSTRACT FROM AUTHOR]

As the only oceanic connection between the Pacific and Arctic‐Atlantic Oceans, Bering Strait throughflow carries a climatological northward transport of about 1 Sv, contributing to the Atlantic Meridional Overturning Circulation (AMOC). Here, Lagrangian analysis quantifies the global distributions of volume transport, transit‐times, thermohaline properties, diapycnal transformation, heat and freshwater transports associated with Bering Strait throughflow. Virtual Lagrangian parcels, released at Bering Strait, are advected by the velocity of Estimating the Circulation and Climate of the Ocean, backward and forward in time. Backward trajectories reveal that Bering Strait throughflow enters the Pacific basin on the southeast side, as part of fresh Antarctic Intermediate Water, then follows the wind‐driven circulation to Bering Strait. Median transit time from 30° $30{}^{\circ}$S in Indo‐Pacific to Bering Strait is 175 years. Sixty‐four percent of Bering Strait throughflow enters the North Atlantic through the Labrador Sea. The remaining 36% flows through the Greenland Sea, warmed and salinified by the northward flowing Atlantic waters. Deep water formation of water flowing through Bering Strait occurs predominantly in the Labrador Sea. Subsequently, this water joins the lower branch of AMOC, flowing southward in the deep western boundary current as North Atlantic Deep Water. Median transit time from Bering Strait to 30° $30{}^{\circ}$S in South Atlantic is 160 years. The net heat transport of Bering Strait throughflow is northward everywhere, and net freshwater transport by Bering Strait throughflow is mostly northward. The freshwater transport is largest in the subpolar region of basin sectors: northward in the Pacific and Arctic and southward in the Atlantic. Plain Language Summary: The only oceanic connection between the North Pacific and the Arctic and North Atlantic is through Bering Strait. This small passage allows transport of mass, heat and salt. The contribution of the Bering Strait throughflow to the global overturning circulation is isolated using computer‐generated floats that follow for 1,500 years the waters passing through Bering Strait in their global journey. These virtual‐float trajectories start in the southeast Pacific above 1,000 m and flow northward, getting shallower, fresher and colder. After entering the Arctic through Bering Strait, parcels access the North Atlantic primarily from the Labrador Sea (64%) and Greenland Sea (36%). In these regions they get denser and enter the lower, southward branch of the Atlantic Meridional Overturning Circulation, taking about 350 years to reach the South Atlantic at 30° $30{}^{\circ}$ S from the same latitude in the South Pacific. The Bering Strait throughflow contributes to the global mid‐depth overturning with its upper, northward branch in the Pacific and the lower, southward branch in the Atlantic. This cell carries heat everywhere northward because it flows northward at higher temperatures and fresher waters in the Pacific than the southward flow in the Atlantic. Key Points: Bering Strait throughflow is part of the mid‐depth overturning with the upper branch in the Pacific and the lower branch in the AtlanticBering Strait throughflow carries heat northward everywhereBering Strait throughflow carries freshwater northward in the Pacific but southward in the Atlantic, enhancing the salt‐advection feedback [ABSTRACT FROM AUTHOR]

This study assesses the settling dynamics of suspended sediments along the hyper‐turbid Gironde Garonne fluvial‐estuarine system, with an innovative optical SCAF instrument (System of Characterization of Aggregates and Flocs). Two fields campaigns were carried out to determine the settling velocity and properties of suspended sediments during a semi‐diurnal tidal cycle, as well as hydrodynamic conditions and water properties. The two sampling stations were representative of two regions: a tidal river dominated by fresh water and an estuary affected by salty or brackish waters. A high spatial variability of the settling velocity was observed along the fluvial‐estuarine system and vertically along the water column. Settling velocities ranged from 0.02 to 0.4 mm/s. This study confirms that in hyper‐turbid systems, the suspended sediment concentration (SSC) is predominantly driving the settling dynamics of suspended sediment. Threshold concentrations have been defined for the flocculation and hindered regimes where the settling velocity may vary by one order of magnitude. Although in natural environments it is difficult to distinguish between the effects of SSC and turbulence (as they are correlated), in the Gironde‐Garonne system the turbulent shear G seems to affect the settling of suspended sediment to a lower extent. Settling velocity variations cannot be directly correlated to salinity or organic matter content. Despite differences in hydrodynamic and environmental conditions in fluvial and estuarine regions, a common prediction law has been found to estimate settling velocity of suspended sediment as a function of suspended sediment concentration. Plain Language Summary: Estuaries and rivers are biotically rich environments strongly impacted by human activities. Mud trapping capacity of such systems has a major influence on water quality by reducing light availability, promoting oxygen depletion and by trapping adsorbed contaminants, bacteria and nutrients. A key dynamical parameter impacting the trapping of mud is the sediment settling velocity. Sediment settling is influenced by a wide range of environmental factors such as salinity, sediment concentration, turbulence of the flow and organic matter. This manuscript presents sediment settling data from field surveys carried out along the Garonne River—Gironde Estuary system (France), where large quantities of mud are trapped during the dry season. It highlights the driving role of sediment concentration on the settling dynamics along the entire system, despite the hydrodynamics and water properties of riverine waters differing from the estuarine waters. The turbulence of the flow appeared to be of secondary importance. An unique empirical prediction law has been established for the whole system contrary to other systems around the world. An improved understanding of sediment fluxes contributes to effective waterways management and the preservation of essential ecological environments. Key Points: In such hyper‐turbid system, the suspended sediment concentration predominantly drives the settling dynamics of suspended sedimentThe turbulent shear appeared to be a control parameter of secondary importanceA common prediction law can be found for the whole system [ABSTRACT FROM AUTHOR]

Fronts in the Bay of Bengal (BoB) are active and can potentially impact the regional dynamics such as temperature variability, salinity distribution and oceanic circulation. Based on the high resolution model output (LLC4320), this study investigates the characteristics of submesoscale fronts in the northern BoB and associated compensation/reinforcement effects. At sea surface, horizontal gradients of salinity and density are remarkable in the northern BoB, and they are nearly 3 times larger than temperature gradients. As the depth deepens, temperature gradients increase and become comparable to salinity gradients, while density gradients decrease a lot due to the increasing effects of compensation at subsurface. Statistical results show the dominance of salinity‐controlled fronts over temperature‐controlled fronts, and compensated fronts over reinforced fronts. The surface cooling/heating results in significant temporal variation of compensation at surface, but this variation is limited at subsurface by the blocking of the mixed layer base. The submesoscale‐selective feature of compensation is much more pronounced at subsurface layer than surface layer. From statistical analysis and idealized numerical model, we found the slump of salinity‐controlled compensated fronts are important in generating temperature inversion and maintaining barrier layer. This study validates the compensation theories originating from observations, and further illustrates the importance of subsurface compensated fronts using spatially continuous, regionally extended and longer‐term model output. The subsurface‐intensified submesoscale‐selective compensation is proved for the first time in this study. Plain Language Summary: With cold, fresh water on the one side and warm, salty water on the other side, roles of temperature and salinity in changing density are opposed across fronts, and they are referred to as compensated fronts. Otherwise, the fronts are reinforced by temperature and salinity. The strength of compensated fronts are thwarted to some extent compared to reinforced fronts, thus the existence of compensation effects are not favorable for forming a sharp front and associated instability processes. The statistics of submesoscale compensated/reinforced fronts in the northern BoB are comprehensively analyzed in this study. Concerning the amount of freshwater input, fronts are dominated by salinity gradients instead of temperature gradients over the northern BoB, and compensated fronts are more likely to form during winter with the existence of both large salinity gradients and heat losses. Both statistical analysis and idealized model simulation suggest that when the salinity front compensated by temperature collapses, a reversed vertical temperature gradient (temperature inversion) is favored to form. Key Points: The submesoscale salinity (temperature) fronts are pronounced at surface (subsurface), and they tend to be compensatedSubsurface layer is featured with more compensation than surface layer, and this subsurface compensation is more submesoscale‐selectiveThe slump of salinity‐controlled compensated fronts leads to temperature inversion and the retention of barrier layer [ABSTRACT FROM AUTHOR]

For millennia, springs have provided water for drinking, domestic use, balneological treatment, liminality rites as well as tourist attractions. Amidst these uses, anthropogenic activities, especially urbanization and agriculture, continue to impair the functionality of springs. With the looming decadal climate change, freshwater springs could be a sustainable source of clean water for the realisation of Sustainable Development Goal 6. This paper presents the results of the sanitary inspection and assessment of limnochemical characteristics and quality of water samples (n = 64) from four freshwater springs (coded SPR1, SPR2, SPR3, and SPR4) in Kansanga, a flash flood-prone area in the African Great Lakes region of Uganda. Each sample was analysed for 17 parameters (temperature, pH, electrical conductivity, turbidity, fluorides, sulphates, chlorides, nitrates, orthophosphates, total dissolved solids, dissolved oxygen, total alkalinity, potassium, sodium, total, magnesium and calcium hardness) following the standard methods. Water quality index (WQI) was calculated to establish the quality of the water samples based on the physicochemical parameters measured. Based on the sanitary risk assessment results, the springs had medium- to high-risk scores, but most water parameters were within the WHO guidelines for potable water, except for nitrates (in SPR1 and SPR2), hardness levels (in SPR2), and dissolved oxygen (in all the samples). Sampling season and location had significant effects on the limnochemistry of the freshwater springs (p < 0.05). The water quality indices calculated indicated that the water from the springs was of good quality (WQI = 50–57), but there was a reduction in water quality during the wet season. The best water quality was recorded in samples from SPR4, followed by those for SPR3, SPR1, and SPR2. These results provide insights into the contribution of floods and poor sanitation facilities to the deterioration of spring water quality in Kansanga, and the need to leverage additional conservation strategies to support vulnerable communities in the area. Further studies are required to establish the risk posed by trace metals and microbes that may contaminate freshwater in the studied springs, especially following flood events. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Geology & Oilfield Development in Daqing is the property of Editorial Department of Petroleum Geology & Oilfield Development in Daqing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bonefishes and other elopomorphs have a unique, transparent leptocephalus larval stage that is challenging to study due to its cryptic nature. Understanding life history is important especially considering adult bonefishes in Hawaiʻi are highly sought gamefish valued for their tenacious fight on rod-and-reel and delicate taste. In this study light traps were used to capture leptocephali at three nearshore locations around Oʻahu, Hawaiʻi. Across 130 + h of trapping, 59 larvae were captured, most during 2000–2100 h on rising tides. Lengths ranged from 54 to 66 mm, indicating late stage I larvae. Otolith analyses (N = 26) revealed ages from 28 to 72 days with an average age of about 48 days. Genetic species identification on a subset of the larvae showed that one of 28 total specimens was Albula virgata, which is endemic to Hawaiʻi, and the remaining were the Indo-Pacific A. glossodonta. Along with calm inshore waters, estuarine habitat appears to be a critical element for leptocephali recruitment success. Reducing impacts to these estuarine habitats and protecting and restoring freshwater input may have positive impacts on leptocephali recruitment, the essential starting point for thriving bonefish fisheries in Hawaiʻi. [ABSTRACT FROM AUTHOR]

The southern Gabès aquifer in southeastern Tunisia faces significant stress due to unsustainable groundwater extraction. This study employs a SEAWAT model to evaluate groundwater losses, salinization mechanisms, and the interaction between the confined aquifer and the Mediterranean Sea. The model, incorporating well pumping rates, regional freshwater inflows from the Matmata Mountain Range, and the Mediterranean Sea boundary, demonstrated high accuracy in simulating hydraulic heads. Findings reveal that regional inflow is only half of the current pumping rate, indicating unsustainable groundwater use. The study also assessed salinity dynamics by modeling the Mediterranean Sea as a constant head and salinity boundary. Results suggest limited exchange between the aquifer and the sea, challenging previous assumptions. While the immediate risks of salinization are low, continued over-extraction could compromise the aquifer's long-term sustainability. This research highlights the need for stricter local groundwater management, offers insights into regional coastal aquifer interactions, and contributes to global discussions on managing stressed aquifer systems. [ABSTRACT FROM AUTHOR]

Nitrification rate measurements provide critical information on the performance of an environmental process central to the N cycle and are best studied using isotope labeling techniques. However, combining the high sensitivity of isotope labeling techniques with selected inhibition of nitrifiers as a whole or of specific nitrifier guilds has not been established in limnology. This can be achieved with different concentrations of the commonly used nitrification inhibitor allylthiourea (ATU). In the 15N‐ammonium oxidation technique, the converted isotope label is typically captured in an excess pool of 14N‐nitrite. Here, we assessed how different storage conditions affect the stability of the nitrite pool in freshwater samples treated with ATU. When stored frozen, the nitrite pool was rapidly destabilized to 25–31% after 7 d of storage and even to less than 5% after storage exceeding 90 d for samples treated with ATU, thus making them unusable for rate determinations in these cost and labor‐intensive experiments. In comparison, this was not the case in marine samples or freshwater samples not treated with ATU, where the nitrite pool remained stable. Building on these results, we tested two options to stabilize nitrite during the storage of freshwater samples. The nitrite pool was stable if samples were stored at 4°C instead of freezing. We recommend this option for short‐term storage. For long‐term storage, samples should be supplemented with 0.5 mmol L−1 NaCl to increase salinity before freezing. As in marine samples, this stabilized the nitrite pool. Our results provide important guidance for the storage of non‐saline samples used for nitrification rate measurements in freshwater environments. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microplastic (MP) release into the terrestrial environment has occurred since humans started manufacturing and using plastics. These tiny plastic particles can be found in various media, including the atmosphere, soil, freshwater, sediments, and organisms. MPs migrate through terrestrial environmental media due to wind, water, gravity, and biological processes. Although the variables that affect the migration process have been investigated in various settings, the mechanisms of MP migration in terrestrial environments have yet to be systematically characterized. This study classifies the migration mechanisms of MPs as physical, chemical and biological manners, and discusses the factors affecting migration mechanisms in dynamic factors, environmental factors and MP characteristics. Examining the action mechanisms of migration can establish a foundation for understanding the migration processes of MPs and provide a theoretical framework for modeling MP movement in environmental. Future research challenges include understanding the effect of MP characteristics in the migration process and simulating the migration of MPs in the environment in the long-term. Exploring the MP migration on various spatial and temporal scales, considering the life cycle of MPs is a worthy research direction. [ABSTRACT FROM AUTHOR]

Organisms have adapted to dynamic river flows as part of the natural flow regime. However, climate change and humans' use of fresh water are associated with decreases in the quality and quantity of surface waters. In addition, river impoundments and water withdrawals for human use regulate and dampen the dynamism of flow in many rivers. These changes to the natural flow regime can impact the spawning migrations of lampreys (Petromyzontiformes). Here, our goal is to review the ecology of lamprey spawning migrations associated with river flows, with considerations for controlling invasive sea lamprey (Petromyzon marinus) and conserving native lampreys (including native, anadromous sea lamprey). We identify five common themes: (1) natural flow regimes provide a competitive edge to native fishes over non‐native fishes; (2) high flows (up to a threshold) attract adult lamprey and large streams attract large numbers of lamprey; (3) larval lamprey pheromones attract adult lampreys; (4) behavioral responses by adult lamprey to flow (including localized hydraulics) can inform dam passage and trapping methods; and (5) changes to rivers induced by climate change have been implicated in changing the phenology of run timing and spawning location. Controlling invasive sea lamprey and conserving native lampreys can be done with pheromones and flow management. Pheromones may be of more use under focused management efforts to control invasive sea lamprey, whereas flow management can provide a foundation for conservation of native lampreys. [ABSTRACT FROM AUTHOR]

IRRIGATION water quality is a crucial parameter for crop production, which was reported to be deteriorated due to its closer to the coast of Mediterranean sea. Six profiles were selected as a clay texture in the current study. Profiles 1 and 2 represent soil irrigated with a good quality water, while profiles 3, and 4 refer to soil irrigated partially with lower quality of irrigation water, whereas the last two profiles 5, and 6 represent the irrigated soil with the lowest water quality. Soil samples comprise all soil profiles for different required analyses and also water samples were collected from different locations related to soil profiles. The main purpose of the study is to inquire and evaluate the effect of irrigation water quality and its impacts on soil physical and chemical properties. As a consequence, profiles 5 and 6 have the highest values of soil salinity and exchangeable cations as a sequence of using the lowest quality of irrigation water. Water salinity of irrigation resources for profiles 5, and 6 were 0.87 dS/m and 0.83 dS/m, which reflected in salt content of profiles 5 and 6 to be 1.6 and 0.99 dS/m, respectively. ESP has also the highest values in profiles 5 and 6, which reached 23.4 % for each. On the contrary, profile 2 has the highest value of exchangeable calcium (27.6 meq/100g soil). Total water stable aggregates (> 0.25 mm ) has a high negative correlation with salinity of irrigation water and ESP. The correlation was found to be -0.683** for ECiw and -0.547** for ESP. Structure Coefficient revealed a similar negative correlations to be (-0.544**), (-0.411*) and (-0.502*) for ECiw, SAR and soluble Sodium of irrigation water, respectively. On the contrary, ECaP has a positive correlation with each of optimum size of aggregates to be (0.458*) and water stable aggregates (1- 0.5mm) to be (0.543*). ECiw as well as soluble magnesium and soluble sodium has a negative effect on soil bulk density due to increased salts. It is concluded that low quality of irrigation water affect negatively the most of structure parameters, i.e. aggregates criteria and other soil physical properties. Therefore, sustainable soil conservation especially at North Nile Delta depend on irrigation water quality, which is needed to maintain its potentiality and productivity. [ABSTRACT FROM AUTHOR]

This article presents a new method for extracting lithium from brine, which is an important component of lithium-based energy storage systems. The method involves using a decoupled membrane-free electrochemical cell that cycles lithium ions between iron-phosphate electrodes. The cell design allows for the extraction of lithium from brines with high magnesium/lithium ratios and low lithium concentrations, resulting in the production of battery-grade lithium carbonate. The process also has the potential to harvest osmotic energy from the brines, leading to energy savings. A pilot-scale cell was used to successfully extract lithium from Dead Sea brine with a recovery rate of 84.0%. The article discusses the extraction performance, osmotic energy contribution, durability, and scalability of the process, showing that it is superior to other elements, durable, and can be scaled up successfully. The energy consumption and material costs of the process are also analyzed, demonstrating its competitiveness and potential for further optimization. The article concludes by highlighting the simplicity and scalability of the cell design and its potential for broader applications. [Extracted from the article]