Release characteristics of arsenic from sediments and its source or sink competition with phosphorus: A case of a great lake with grass-algae alternation.

The arsenic (As) release from sediments in great lakes is affected by various factors. In this study, the characteristics of As release from sediments was investigated, and the As sources and sinks with the strengths in sediments from different areas (grass-type, algae-type, and grass-algae alternation areas) in great shallow lakes (Taihu Lake, China) were analyzed, and the influence of P competition in the process of As release was also studied. The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes (0 to 28.12 µg/L), and the sediments from algae-type areas had the higher values. The sediments from western lake and northwest lake bay were a strong As and a weak P source, and the north lake bay had the opposite trend of these two regions. Intense P source competition with As from the sediments occurred in algae-type areas. The grass-type areas had strong As and P retention capacities, indicating a sink role of sediment with high As and P sorption capacities. The degree of As and P saturation had similar trend in sediments, and the grass-type areas had the higher values, 18.3%-21.4% and 15.31%-20.34%, respectively. Contribution analysis results showed that most of As release contribution was from the bottom (30-50 cm) sediments, and the surface (0-10 cm) sediments from algae-type areas contributed more to the overlying water than other region.

Significant spatiotemporal pattern of nitrous oxide emission and its influencing factors from a shallow eutropic lake in Inner Mongolia, China.

Eutrophic shallow lakes are generally considered as a contributor to the emission of nitrous oxide (N2O), while regional and global estimates have remained imprecise. This due to a lack of data and insufficient understanding of the multiple contributing factors. This study characterized the spatiotemporal variability in N2O concentrations and N2O diffusive fluxes and the contributing factors in Lake Wuliangsuhai, a typical shallow eutrophic and seasonally frozen lake in Inner Mongolia with cold and arid climate. Dissolved N2O concentrations of the lake exhibited a range of 4.5 to 101.2 nmol/L, displaying significant spatiotemporal variations. The lowest and highest concentrations were measured in summer and winter, respectively. The spatial distribution of N2O flux was consistent with that of N2O concentrations. Additionally, the hotspots of N2O emissions were detected within close to the main inflow of lake. The wide spatial and temporal variation in N2O emissions indicate the complexity and its relative importance of factors influencing emissions. N2O emissions in different lake zones and seasons were regulated by diverse factors. Factors influencing the spatial and temporal distribution of N2O concentrations and fluxes were identified as WT, WD, DO, Chl-a, SD and COD. Interestingly, the same factor demonstrated opposing effects on N2O emission in various seasons or zones. This research improves our understanding of N2O emissions in shallow eutrophic lakes in cold and arid areas.

Exploring the diversity of dissolved organic matter (DOM) properties and sources in different functional areas of a typical macrophyte - derived lake combined with optical spectroscopy and FT-ICR MS analysis.

Lake Baiyangdian is one of China's largest macrophyte - derived lakes, facing severe challenges related to water quality maintenance and eutrophication prevention. Dissolved organic matter (DOM) was a huge carbon pool and its abundance, property, and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems. In this study, Lake Baiyangdian was divided into four distinct areas: Unartificial Area (UA), Village Area (VA), Tourism Area (TA), and Breeding Area (BA). We examined the diversity of DOM properties and sources across these functional areas. Our findings reveal that DOM in this lake is predominantly composed of protein - like substances, as determined by excitation - emission matrix and parallel factor analysis (EEM - PARAFAC). Notably, the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA. Ultrahigh - resolution mass spectrometry (FT - ICR MS) unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds, suggesting that macrophytes significantly influence the material structure of DOM. DOM properties exhibited specific associations with water quality indicators in various functional areas, as indicated by the Mantel test. The connections between DOM properties and NO3N and NH3N were more pronounced in VA and BA than in UA and TA. Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.

Drivers and mechanisms of harmful algal blooms across hydrologic extremes in hypereutrophic grand lake st marys (Ohio).

Grand Lake St. Marys (GLSM) is a large, shallow, hypereutrophic lake situated in an agricultural watershed with high-nutrient, non-point source runoff. The resulting harmful algal blooms (HABs) are typically dominated by Planktothrix, which can produce microcystin, a potent cyanobacterial toxin that has varied in concentration over the past decade. Some drivers of bloom biomass and toxicity in GLSM are described, but recent years (2019-2022) have exhibited anomalous combinations of winter ice cover and spring runoff, suggesting that additional factors contribute to variability in HAB severity and toxicity. 2020 and 2022 were typical water years, with normal tributary runoff volumes occurring primarily in late winter and spring after either little to no ice cover (2019-2020) or heavy/prolonged ice cover (2021-2022). However, 2021 exhibited prolonged winter ice and low winter/spring runoff. 2020 and 2022 were typical bloom years, with near monoculture, Planktothrix-dominated biomass (11 to 405 µg/L total chlorophyll) and high total concentrations of microcystins (<0.3 to 65 µg/L). However, the first half of 2021 exhibited lower biomass (18 to 65 µg/L chlorophyll a) and toxin concentrations (0.4 to 2.0 µg/L). While biomass returned to bloom levels when external tributary loading increased, ammonium uptake and regeneration rates and microcystin concentrations remained low throughout 2021 (in contrast to other years). Overall, potential ammonium uptake rates strongly correlated with chlorophyll and microcystin concentrations (Bayesian R2 = 0.59; 95% CI = 0.44 to 0.65). Phytoplankton diversity was higher in 2021 than other years, especially in spring/early summer, with increased dinoflagellates and diatoms in spring, followed by a mixed cyanobacterial assemblage in summer. These results suggest that lower external nutrient loads can drive immediate positive impacts on water quality, such as reduced HAB biomass and toxicity and higher phytoplankton diversity, even in hypereutrophic, shallow lakes.

A novel strategy of bloom forming cyanobacteria Microcystis sp. in response to phosphorus deficiency: Using non-phosphorus lipids substitute phospholipids.

Despite significant reductions in phosphorus (P) loads, lakes still experience cyanobacterial blooms. Little is known regarding cellular P regulation in response to P deficiency in widely distributed bloom causing species such as Microcystis. In this study, we investigated changes in P containing and non-P lipids contents and their ratios concomitantly with the determinations of expression levels of genes encoding these lipids in cultural and field Microcystis samples. In the culture, the content of phosphatidylglycerol (PG) decreased from 2.1 µg g-1 in P replete control to 1.2 µg g-1 in P-deficient treatment, while non-P lipids, like sulfoquinovosyldiacylglycerol (SQDG) and monogalactosyldiacylglycerol (MGDG), increased dramatically from 13.6 µg g-1 to 142.3 µg g-1, and from 0.9 µg g-1 to 16.74 µg g-1, respectively. The expression of the MGDG synthesis gene, mgdE, also increased under low P conditions. Significant positive relationships between soluble reactive phosphorus (SRP) and ratios of P-containing lipids (PG) to non-P lipids, including SQDG, MGDG and digalactosyldiacylglycerol (DGDG) (P < 0.05) were observed in the field investigations. Both cultural and field data indicated that Microcystis sp. might increase non-P lipids proportion to lower P demand when suffering from P deficiency. Furthermore, despite lipid remodeling, photosynthetic activity remained stable, as indicated by comparable chlorophyll fluorescence and Fv/Fm ratios among cultural treatments. These findings suggested that Microcystis sp. may dominate in P-limited environments by substituting glycolipids and sulfolipids for phospholipids to reduce P demand without compromising the photosynthetic activity. This effective strategy in response to P deficiency meant a stricter P reduction threshold is needed in terms of Microcystis bloom control.

Spatiotemporal dynamics of 2-methylisoborneol produced by filamentous cyanobacteria and associated driving factors in Lake Taihu, China.

The proliferation of filamentous cyanobacteria in lakes can result in the generation of odor-causing compounds, predominantly 2-methylisoborneol (2-MIB), which pose odor-related challenges. In an effort to elucidate the spatiotemporal dynamics of 2-MIB and related influencing factors in East Lake Taihu, monthly investigations were undertaken from April 2022 to March 2023. In addition to the monthly survey, a whole-lake survey was conducted during the high-temperature period from July to September. The monthly survey revealed a distinct unimodal fluctuation in the concentration of 2-MIB in East Lake Taihu, with an average concentration at 297.0 ng/L during the high-temperature period. During the high-temperature period, the filamentous cyanobacterial communities detected in East Lake Taihu consisted primarily of species belonging to genera Leptolyngbya, Oscillatoria, Planktothricoides, and Pseudanabaena. However, no significant correlations were found between their densities and 2-MIB concentration. In addition, the mic gene was predominantly detected in genera Pseudanabaena and Planktothricoides, with the latter being the primary contributor to 2-MIB production. Furthermore, a succession of cyanobacteria capable of producing 2-MIB was detected, with water temperature and radiation intensity being identified as the primary driving factors. The temporal variation of 2-MIB concentration within East Lake Taihu during the whole year was primarily modulated by factors such as water temperature, water transparency, dissolved oxygen, and chlorophyll-a. During the high-temperature period, the 2-MIB concentration in the alga-dominated zone of East Lake Taihu was approximately 1.7 times greater than that in the macrophyte-dominated zone, with nutrient and transparency being identified as the main influencing factors. Consequently, our findings are of great significance for monitoring the sources and variation of 2-MIB in shallow lakes, providing a scientific foundation and theoretical guidance for odor management.

Risk assessment of toxic cyanobacterial blooms in recreational waters: A comparative study of monitoring methods.

Toxic cyanobacterial blooms impose a health risk to recreational users, and monitoring of cyanobacteria and associated toxins is required to assess this risk. Traditionally, monitoring for risk assessment is based on cyanobacterial biomass, which assumes that all cyanobacteria potentially produce toxins. While these methods may be cost effective, relatively fast, and more widely accessible, they often lead to an overestimation of the health risk induced by cyanotoxins. Monitoring methods that more directly target toxins, or toxin producing genes, may provide a better risk assessment, yet these methods may be more costly, usually take longer, or are not widely accessible. In this study, we compared six monitoring methods (fluorometry, microscopy, qPCR of 16S and mcyE, ELISA assays, and LC-MS/MS), of which the last three focussed on the most abundant cyanotoxin microcystins, across 11 lakes in the Netherlands during the bathing water season (May-October) of 2019. Results of all monitoring methods significantly correlated with LC-MS/MS obtained microcystin levels (the assumed 'golden standard'), with stronger correlations for methods targeting microcystins (ELISA) and microcystin genes (mcyE). The estimated risk levels differed substantially between methods, with 78 % and 56 % of alert level exceedances in the total number of collected samples for fluorometry and microscopy-based methods, respectively, while this was only 16 % and 6 % when the risk assessment was based on ELISA and LC-MS/MS obtained toxin concentrations, respectively. Integrating our results with earlier findings confirmed a strong association between microcystin concentration and the biovolume of potential microcystin-producing genera. Moreover, using an extended database consisting of 4265 observations from 461 locations across the Netherlands in the bathing water seasons of 2015 - 2019, we showed a strong association between fluorescence and the biovolume of potentially toxin-producing genera. Our results indicate that a two-tiered approach may be an effective risk assessment strategy, with first a biomass-based method (fluorometry, biovolume) until the first alert level is exceeded, after which the risk level can be confirmed or adjusted based on follow-up toxin or toxin gene analyses.

Study on the applicability of FAI linear fitting model in the extraction of cyanobacterial blooms.

Currently, more and more lakes around the world are experiencing outbreaks of cyanobacterial blooms, and high-precision and rapid monitoring of the spatial distribution of algae in water bodies is an important task. Remote sensing technology is one of the effective means for monitoring algae in water bodies. Studies have shown that the Floating Algae Index (FAI) is superior to methods such as the Standardized Differential Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) in monitoring cyanobacterial blooms. However, compared to the NDVI method, the FAI method has difficulty in determining the threshold, and how to choose the threshold with the highest classification accuracy is challenging. In this study, FAI linear fitting model (FAI-L) is selected to solve the problem that FAI threshold is difficult to determine. Innovatively combine FAI index and NDVI index, and use NDVI index to find the threshold of FAI index. In order to analyze the applicability of FAI-L to extract cyanobacterial blooms, this paper selected multi-temporal Landsat8, HJ-1B, and Sentinel-2 remote sensing images as data sources, and took Chaohu Lake and Taihu Lake in China as research areas to extract cyanobacterial blooms. The results show that (1) the accuracy of extracting cyanobacterial bloom by FAI-L method is generally higher than that by NDVI and FAI. Under different data sources and different research areas, the average accuracy of extracting cyanobacterial blooms by FAI-L method is 95.13%, which is 6.98% and 18.43% higher than that by NDVI and FAI respectively. (2) The average accuracy of FAI-L method for extracting cyanobacterial blooms varies from 84.09 to 99.03%, with a standard deviation of 4.04, which is highly stable and applicable. (3) For simultaneous multi-source image data, the FAI-L method has the highest average accuracy in extracting cyanobacterial blooms, at 95.93%, which is 6.77% and 13.26% higher than NDVI and FAI methods, respectively. In this paper, it is found that FAI-L method shows high accuracy and stability in extracting cyanobacterial blooms, and it can extract the spatial distribution of cyanobacterial blooms well, which can provide a new method for monitoring cyanobacterial blooms.

Assessment of Water Quality Parameters in Lake Hayq, Northeastern Ethiopia.

Lake Hayq is one of the highland lakes of Ethiopia that furnishes very important ecosystem services, fishing, tourism, transportation, drinking water, livestock watering, and irrigation. However, the lake ecosystem is being degraded by pollution, siltation, and excessive growth of macrophytes, buffer zone degradation, overfishing, and climate variability. Therefore, this study was conducted to assess the physicochemical, heavy metals, and biological water quality parameters of Lake Hayq. Physiochemical (pH, water temperature, conductivity, TDS, total alkalinity, dissolved oxygen, Ca2+, Mg2+, Na+, K+, NH4+, NH3, NO2 -, NO3 -, CO3 -, HCO3 -, SO4 2-, PO4 3-, SiO2, and total phosphorus), heavy metals (Pb, Fe, Zn, Cr, Cu2+, Mn2+, and Ni), and biological (BOD5 and total coliforms) water quality parameters were analyzed both in situ and ex situ. The physicochemical parameters were measured using portable water quality measuring multimeters, the heavy metal analysis was done using the Atomic Absorption Spectrometer, the BOD5 was measured using a BOD5 meter, and the total coliform analysis was done using the spread plate technique. The collected data were analyzed using multivariate, two-way ANOVA to see the mean difference among sampling sites and seasons through the application of SPSS 16. Most of the water quality parameters of Lake Hayq have met the WHO standards for recreation, aquatic life, and drinking water quality. However, some parameters, such as Pb, BOD5, and total coliforms, were above WHO water quality permissible limits. Therefore, ecohydrological (nature-based) waste treatment methods such as macrophyte restoration in buffer zones and ecofriendly farming activities should be practiced to minimize the contamination of the lake.

Pre-vaccination Schistosoma mansoni and hookworm infections are associated with altered vaccine immune responses: a longitudinal analysis among adolescents living in helminth-endemic islands of Lake Victoria, Uganda.

Background: Variations in vaccine responses have been observed between populations. A role for helminth infections has been proposed due to their immunomodulatory properties. In a secondary analysis of data from a randomised trial assessing effects of anthelminthic treatment on vaccine responses, we examined associations between helminth infections at baseline prior to vaccine administration, and vaccine responses among adolescents (9-17 years) in Koome Islands, Lake Victoria, Uganda. Methods: Participants received BCG [week 0], yellow fever (YF-17D), oral typhoid (Ty21a), HPV-prime [week 4], and HPV-boost, tetanus/diphtheria [week 28]. Outcomes were BCG-specific interferon-γ ELISpot responses and antibody responses to yellow-fever-, typhoid-, HPV-, tetanus- and diphtheria-specific antigens measured at two time points post vaccination. S. mansoni infection was determined as positive if either the plasma Circulating Anodic Antigen (CAA) assay or stool PCR were positive. Hookworm and Strongyloides were determined by stool PCR. Linear mixed effects regression was used to assess associations. Results: Among 478 adolescents, 70% were Schistosoma mansoni (Sm) infected and 23% hookworm infected at baseline. Sm was associated with lower Salmonella Typhi O:LPS-specific IgG responses (adjusted geometric mean ratio (aGMR) 0.69 (0.57-0.83)), and hookworm with higher diphtheria-specific IgG (aGMR 1.16 (1.02, 1.31)) and lower HPV-16-specific IgG (aGMR 0.70 (0.55, 0.90)) post-vaccination. High Sm intensity was associated with lower BCG-specific interferon-γ and S. Typhi O:LPS-specific IgG. Conclusions: We found inverse associations between Sm and responses to two live vaccines, whereas hookworm was positively associated with diphtheria-specific IgG. These findings support the hypothesis that helminth infections can modulate vaccine responses, while also highlighting potential heterogeneity in the direction of these effects.

Yunchengibacter salinarum gen. nov., sp. nov., a novel bacterium of the family Kordiimonadaceae isolated from sediment in Yuncheng salt lake.

A Gram-stain-negative, aerobic, motile and rod-shaped bacterium, the color of the bacterial colony ranges from light yellow to yellow, designated YC-2023-2T, was isolated from sediment sample of Yuncheng salt lake. Growth occurred at 15-45℃ (optimum 37℃), pH 6.0-9.0 (optimum pH 7.0-8.0) and with 0-8.0% NaCl (w/v, optimum 2.0%). The phylogenetic analysis based on 16S rRNA gene sequences showed that strain YC-2023-2T belonged to the family Kordiimonadaceae. The closely related members were Gimibacter soli 6D33T (92.38%), Kordiimonas lipolytica M41T (91.88%), Eilatimonas milleporae DSM 25217T (91.88%) and Kordiimonas gwangyangensis JCM 12864T (91.84%). The genome of strain YC-2023-2T was 2957513 bp, and the genomic DNA G+C content was 63.91%. The main respiratory quinone was Q-10 and the major fatty acids (>10%) were iso-C15:0, C16:0, C19:0 cyclo ω8c, Summed Feature 8 (C18:1 ω6c or C18:1 ω7c) and Summed Feature 9 (iso-C17:1 ω9c or C16:0 10-methyl). The major polar lipids consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, unidentified glycolipid, unidentified lipid, and two unidentified aminolipids. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, strain YC-2023-2T is proposed to represent a novel species of a novel genus named Yunchengibacter salinarum gen. nov., sp. nov., within the family Kordiimonadaceae. The type strain is YC-2023-2T (= GDMCC 1.4502T = KCTC 8546T).

Hydrogeochemical processes controlling surface water quality for irrigation in a Mediterranean wetland ecosystem, Northeast Algeria.

Fetzara Lake, considered one of the most important wetlands in northeastern Algeria, was designated a Ramsar site in 2002. The waters in its watershed are affected by salinity, which influences their suitability for irrigation. To identify the factors influencing the quality of these surface waters, geochemical and statistical analyses were carried out on the basis of the results of chemical analyses of 51 samples collected, during two monitoring campaigns, from all the tributaries in the watershed. The findings show the dominance of three hydrochemical facies over the two campaigns: Na-Cl facies (55.17% and 22.73%) characterizes the waters water from Fetzara Lake outlet (drainage channel and wadi Meboudja), in relation to the influx of saliferous elements due to water evaporation in the lake. Ca-Mg-Cl (27.59% and 40.91%) and Ca-Mg-HCO3 (13.79%. and 13.79%) facies characterize the waters of the remaining tributaries, reflecting the dissolution of carbonate formations and the alteration of the Edough metamorphic basement. Multivariate statistical analysis, using principal component analysis (PCA), shows three water types: highly mineralized (EC > 3000 µS/cm), moderately mineralized (1000 < EC < 3000 µS/cm), and weakly mineralized (EC < 1000 µS/cm). Evaporation and silicate weathering are the main mechanisms controlling water mineralization according to the different bivariate plots. Furthermore, cation exchange indices (CAI-I and CAI-II) reveal that these reactions involve the adsorption of Na+ and K+ onto clay minerals, as well as the simultaneous release of Ca2+ and Mg2+ ions. Finally, the various quality indices (SAR, %Na, RSC and KR) revealed that the water in 36% of tributaries is unsuitable for irrigation. These findings will provide important information on surface water quality in the study area, particularly for irrigation purposes, and will contribute to the thoughtful and sustainable management of this resource.

Microplastic evidence assessment from water and sediment sampling in a shallow tropical lake.

Microplastics (MPs) severely threaten inland waterbodies due to the direct impact of human activities. In the present study, spatial and temporal patterns of MPs in a shallow tropical lake were assessed, describing their size, morphology, and polymer types. Water and sediment samples were collected from Lake Chapala during three seasons, and MPs were quantified with a stereomicroscope. The structure, elemental composition, and polymeric composition were determined via environmental scanning electron microscopy and Fourier transform infrared spectroscopy. The highest average concentration of microplastics in Lake Chapala was detected during the low-water period in April 2022 (2.35 items/L), exceeding the July 2022 rainy season concentration (1.8 items/L) by 0.25 items/L, and sediment concentrations were also higher in April 2022 (219 items/kg) compared to July 2022 (210 items/kg). This study highlights the significant pollution of Lake Chapala with microplastics, emphasizing the need for urgent measures to manage plastic waste and mitigate its environmental impact on aquatic ecosystems. PRACTITIONER POINTS: Microplastic contamination was evaluated in Lake Chapala. The distribution profiles of microplastics were different in each area. Heavy metals osmium, tellurium, and rhodium were found associated with the PMs. Polymers were found in this study.

Temporal trends (1972-2017) and spatial differences of persistent halogenated aromatic hydrocarbons in osprey eggs in Finland.

Time trends and regional differences of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), DDTs, polybrominated biphenyls (PBBs) and polybrominated diphenylethers (BDEs) were studied in unhatched osprey eggs collected by bird ringers in 1972-2017 from four areas in Finland. Two study areas were from Baltic Sea, Northern Quark and Finnish Archipelago Sea, while the two others were inland lake areas, eutrophicated Lake Vanajanselkä affected by industrial emissions, and Pristine SW Lake Area. The highest concentrations of most compound groups were in Lake Vanajanselkä consistent with high emissions, the predominance of bream as a prey, and higher concentrations in bream compared to other prey fish. Concentrations of all chlorinated compounds decreased significantly in all study areas. Average annual decreases were ∑PCDD/F 2.3-4.9%, ∑PCB 2.2-4.2%, ∑PCN 2.6-7.0% and ∑DDT 7.1-9.5%, primarily in line with decreased levels in prey fish. From 1972 PBBs and BDEs increased significantly until 1990s declining rapidly thereafter. PCDD/F congener profile was dominated by 2,3,4,7,8-PeCDF, except in Lake Vanajanselkä by 1,2,3,6,7,8-HxCDD. PCB congener profile was dominated by PCB 153 in all study areas, followed by PCB 180 and PCB 138. Among dioxin-like compounds PCBs contributed 82%, PCDDs 14% and PCDFs 4% to toxic equivalent quantity (∑TEQ). PCB 126 contributed most to ∑TEQ, followed by 1,2,3,7,8-PeCDD. BDE 47 being the dominant BDE congener, followed by BDE 100. ∑DDT concentrations were relatively similar across all study areas, with DDE contributing about 90%. Productivity of chicks per active nest was significantly decreased in Lake Vanajanselkä, and the likely explanation is embryotoxicity of dioxin-like compounds. It is plausible that dioxin-like compounds influenced embryonic survival among highly exposed ospreys prior to 2010, especially in Lake Vanajanselkä and Northern Quark. However, decreased survival due to DDE-induced eggshell thinning seems unlikely after 1985, and BDE levels were below those potentially causing adverse effects.

Bat consumption by holostean fishes in the Eocene Lake Messel: insights into the trophic adaptability of extinct gars and bowfins.

Direct evidence of trophic interactions between extinct species is rarely available in the fossil record. Here, we describe fish-mammal associations from the middle Eocene of Messel (Germany), consisting of three specimens of holosteans (one Atractosteus messelensis (Lepisosteidae) and two Cyclurus kehreri (Amiidae)) each preserved with a bat specimen (Palaeochiropteryx tupaiodon) lying in close contact with its jaws. This suggests that these fishes probably died after failed swallowing attempts, with the bat wing membrane entangled in their jaws resulting in a fatal handicap. Based on data from modern gars and bowfins, A. messelensis and C. kehreri may have opportunistically attacked drowning and dying individuals or scavenged on floating/sinking carcasses. This hypothesis is also supported by the unusually high number of bat specimens preserved in the deposits of the Eocene Lake Messel, suggesting that this group of small mammals may have represented a substantial food source for generalist feeders. This is the earliest case of chiropterophagy and the first known evidence of bat consumption by lepisosteid and amiid fishes, emphasizing the high trophic variability and adaptability of these groups throughout their evolutionary histories. The newly described associations provide important information for reconstructing the Eocene Lake Messel palaeoecosystem and its trophic web.

Mitigating thermal stratification in lakes/reservoirs through wind-powered air diffusers.

Thermal stratification can cause various water quality issues in large water bodies. To address this, a new wind-powered artificial mixing system is designed and experimentally tested for various Savonius rotor combinations (three-stage and four-stage rotors). These turbines directly utilize wind energy to draw air into the water column for aeration, bypassing the need for electrical conversion. The rotor performances were tested in terms of power and torque coefficients. Additionally, these rotors were tested for artificial mixing efficiencies in a specially designed water tank that can mimic thermal stratification typically observed in an actual water supply reservoir. Among the rotors, the three-stage rotor with a 60° phase shift was found to exhibit superior power and torque coefficients, achieving a power efficiency value of 0.14. As for the mixing efficiency, the four-stage rotor with a 45° phase shift excelled in mixing efficiency, reaching 95%. PRACTITIONER POINTS: A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. While keeping the total rotor height constant, the three-stage Savonius rotor class shows superior performance against the four-stage Savonius rotor class in terms of power and torque efficiency. Apart from the rotor performance results, the four-stage Savonius rotors show greater artificial mixing efficiency than the three-stage Savonius rotors. Single-pump/diffuser artificial destratification system exhibits better mixing efficiency than multiple-pump/diffuser systems.

Histopathology based study of Nile tilapia fish (Oreochromis niloticus) as a biomarker for water pollution evaluation in the southern gulf of Lake Tana, Ethiopia.

In the past decade, the increasing distribution of pollutants in the aquatic environment has been observed, causing integrative effects on fish. Likewise, due to anthropogenic activities, the southern gulf of Lake Tana is an impacted region, and the production of Nile tilapia fish is reduced. For this reason, the aim of this study was to conduct a histopathological-based study of 48 Nile tilapia fishes' health status at the southern gulf of Lake Tana and aquaculture using a cross-sectional study from February 2023 to May 2023. The study evaluated the histopathology of the gill, liver, gonads, and spleen organs using descriptive statistics accompanied by a 2 × 2 contingency table and t-test analysis. During the study, different histological alterations were detected, and the numbers of fish affected by a specific histological alteration were presented as percentage prevalence; hence, from the total fish examined, hyperplasia (54.15%), followed by pigment deposits (52%), hemorrhage (50%), and immune cell infiltration (50%), respectively, were the most frequently detected alterations. However, Nile tilapias from the southern gulf of Lake Tana were 1.4 (odds ratio) times more likely to show histopathological alterations than those from aquaculture, although statistically, was not significant (p > 0.05). In addition, the study found the mean value of the fish index (95.3) and regressive indices of the gill (13.6), liver (14.8), and gonad (12.3); moreover, the inflammatory indices of the spleen organ (11.3) and mean severity grade value of the gill (2.35) and gonad (1.7) organs, respectively, were obtained from the southern gulf of Lake Tana, and all those values were significantly higher (p < 0.05) from this site as compared to the aquaculture. In general, it has been found that tilapias from the southern gulf of Lake Tana showed higher pathological severity as compared with aquaculture. Among the four target organs evaluated, liver organs were observed to be the most damaged, while gonads were the least impacted organs. Therefore, it has been concluded that tilapia fish are living in abnormal conditions, so to ensure a sustainable fishery, water pollutant sources from Bahirdar city must receive proper attention, and future studies should consider age differences, seasonal variation, and the detection of specific pollutants.

A whole-body micro-CT scan library that captures the skeletal diversity of Lake Malawi cichlid fishes.

Here we describe a dataset of freely available, readily processed, whole-body µCT-scans of 56 species (116 specimens) of Lake Malawi cichlid fishes that captures a considerable majority of the morphological variation present in this remarkable adaptive radiation. We contextualise the scanned specimens within a discussion of their respective ecomorphological groupings and suggest possible macroevolutionary studies that could be conducted with these data. In addition, we describe a methodology to efficiently µCT-scan (on average) 23 specimens per hour, limiting scanning time and alleviating the financial cost whilst maintaining high resolution. We demonstrate the utility of this method by reconstructing 3D models of multiple bones from multiple specimens within the dataset. We hope this dataset will enable further morphological study of this fascinating system and permit wider-scale comparisons with other cichlid adaptive radiations.

Anthropogenic and climatic impacts on historic sediment, carbon, and phosphorus accumulation rates using 210Pbex and 137Cs in a sub-watershed linked to Zarivar Lake, Iran.

To estimate a watershed's response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m-2 year-1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m-2 year-1 respectively. During this period, the watershed underwent extensive deforestation (12%) on steep slopes, coinciding with higher mean annual precipitations (more than double). Conversely, after 2009, when check dams were installed in the sub-watershed, the sediment load to the lake became negligible. The results of this research indicate that anthropogenic activities had a pronounced effect on MAR, OCAR, and PPAR, causing them to fluctuate from negligible amounts to values twice the averages over the last century, amplified by climatic factors. These results imply that implementing climate-smart watershed management strategies, such as constructing additional check dams and terraces, reinforcing restrictions on deforestation, and minimum tillage practices, can facilitate protection of lacustrine ecosystems under accelerating climate change conditions.

Coassembly and binning of a twenty-year metagenomic time-series from Lake Mendota.

The North Temperate Lakes Long-Term Ecological Research (NTL-LTER) program has been extensively used to improve understanding of how aquatic ecosystems respond to environmental stressors, climate fluctuations, and human activities. Here, we report on the metagenomes of samples collected between 2000 and 2019 from Lake Mendota, a freshwater eutrophic lake within the NTL-LTER site. We utilized the distributed metagenome assembler MetaHipMer to coassemble over 10 terabases (Tbp) of data from 471 individual Illumina-sequenced metagenomes. A total of 95,523,664 contigs were assembled and binned to generate 1,894 non-redundant metagenome-assembled genomes (MAGs) with ≥50% completeness and ≤10% contamination. Phylogenomic analysis revealed that the MAGs were nearly exclusively bacterial, dominated by Pseudomonadota (Proteobacteria, N = 623) and Bacteroidota (N = 321). Nine eukaryotic MAGs were identified by eukCC with six assigned to the phylum Chlorophyta. Additionally, 6,350 high-quality viral sequences were identified by geNomad with the majority classified in the phylum Uroviricota. This expansive coassembled metagenomic dataset provides an unprecedented foundation to advance understanding of microbial communities in freshwater ecosystems and explore temporal ecosystem dynamics.