Lake plastisphere as a new biotope in the Anthropocene: Potential pathogen colonization and distinct microbial functionality.

The not-homogenous microplastics (MPs) distribution in freshwaters results in distinct microbial communities. Yet knowledge regarding plastisphere in metabolic pathways and element cycling behaviors remains limited. In this study, we collected MPs from 15 sampling sites in the Taihu Lake in China, and found that MPs were widely distributed in this freshwater lake, and dominantly composed of fibrous polyethylene terephthalate. Based on the metagenomic analysis, we found that MPs were colonized by Bacteroidia, Alpha-Proteobacteria, and Bacilli as a filter, but depleted in Verrucomicrobiae. Potential pathogens of plant eudicots and monocots were significantly enriched in plastisphere. Predicted functional profiles involved in the metabolism of other amino acids, biosynthesis of other secondary metabolites, and glycan biosynthesis and metabolism were overrepresented in plastisphere. Regarding elemental cycling, functional genes related to nitrogen fixation and nitrification showed 39.6% and 67.5% decline in plastisphere, whereas the genes involved in denitrification and nitrate reduction were significantly enriched. For sulfur cycles, the plastisphere exhibited higher sulfate reduction and sulfur oxidation system activities. Additionally, the taxonomic compositions and predicted functions in the plastispheres were mainly driven by the stochastic processes, while the deterministic processes were more important for the planktonic communities. The distinctions in the microbial composition, the predicted functionality, and the underly mechanisms between plastisphere and planktonic communities illustrated the unique ecology of the new anthropogenic-related plastisphere ecosystems.

Identifying the drivers of chlorophyll-a dynamics in a landscape lake recharged by reclaimed water using interpretable machine learning.

The water quality of lakes recharged by reclaimed water is affected by both the fluctuation of reclaimed water quality and the biochemical processes in the lakes, and therefore the main controlling factors of algal blooms are difficult to identify. Taking a typical landscape lake recharged by reclaimed water as an example and using the spatiotemporal distribution characteristics and correlation analysis of water quality indexes, we propose an interpretable machine learning framework based on random forest to predict chlorophyll-a (Chl-a). The model considered nutrient difference indexes between reclaimed water and lake water, and further used feature importance ranking and partial dependence plot to identify nutrient drivers. Results show that the NO3--N input from reclaimed water is the dominant nutrient driver for algal bloom especially at high temperatures, and the negative correlation between NO3--N and Chl-a in the lake water is the consequence of algal bloom rather than the cause. Our study provides new insights into the identification of eutrophication factors for lakes recharged by reclaimed water.

The apoptosis of Chlorella vulgaris and the release of intracellular organic matter under metalimnetic oxygen minimum conditions.

Metalimnetic oxygen minimum (MOM) is a frequent occurrence in lakes and reservoirs, and its formation is related to the blooming and apoptosis of algae. In this study, the apoptosis mechanism of Chlorella vulgaris (C. vulgaris) and the release of intracellular organic matter (IOM) under different MOM conditions were analyzed by changing the dissolved oxygen (DO) (7.0 mg/L, 3.0 mg/L, and 0.3 mg/L) and water pressure (0.3 MPa and normal pressure). The integrity and auto-fluorescence of algae cells decreased rapidly in the first 8 days, and then stabilized gradually during the development of MOM. Compared with that of water pressures, DO had a significant effect on the activity of algal cells, and higher initial DO levels (3.0 mg/L and 7.0 mg/L) accelerated the lysis of algal cells. The integrity of algae cells decreased to 28.8 %, 31.8 % and 56.6 % at the initial DO of 7 mg/L, 3 mg/L and 0.3 mg/L under 0.3 MPa, respectively. Meanwhile, the concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) continued to increase and reached their maximum at 8 or 12 days, respectively, due to the IOM release caused by algal cell rupture, and then gradually decreased due to microbial degradation. Consistent with the results of membrane integrity, the highest DOC and DON concentrations were found at higher initial DO conditions. By parallel factor analysis, the change in total organic matter fluorescence intensity was consistent with DOC, once again increasing in the first 8 days and then gradually decreasing. The increased humic-like component, which is related to higher aromaticity, led to the monotonic increase of HAAFPs and THMFPs. However, the released IOM of C. vulgaris had lower N-DBPFPs, with TCNMFP predominating primarily. In summary, these results shed new lights on exploring the apoptosis of algae and the release of IOM during the development of MOM.

Combining physical-based model and machine learning to forecast chlorophyll-a concentration in freshwater lakes.

Increasing algal blooms in freshwater lakes have become a serious challenge facing the world. Short-term forecast of chlorophyll-a concentration (Chla) is essential for providing early warnings and taking action to mitigate the risks of algal blooms in freshwater lakes. At present, a variety of data-driven models and physical-based models have been developed for Chla forecast, yet how to effectively combine multiple models for improving the forecast accuracy remains largely unknown. Here we developed an effective model by combining a physical-based model and machine learning algorithms (long short-term memory, LSTM; random forest, RF; support vector machine, SVM) to forecast the Chla in a freshwater lake, and a Bayesian model averaging (BMA) ensemble forecasting method was further proposed to improve the accuracy and reliability of the forecast results. We found that, with the increase of time steps of advance forecast from 1-day to 7-day, the forecast accuracy as measured by R2 of the machine learning algorithms is decreased from 0.95 to 0.68. The combination of physical-based modeling with LSTM had great capability in short-term forecast of Chla, owing to the fact that the physical-based model can provide high-frequency Chla data and LSTM is skilled at forecasting in the sequence. This is also evidenced by the weights in the BMA method. The proposed BMA short-term ensemble forecasting results had the robust performance when compared to each individual machine learning forecast model for the 7-day advance forecast, with the largest R2 (0.834) and the smallest RMSE (0.267 µg/L). In particular, the uncertainty of a single machine learning model can be effectively reduced by the BMA method.

Testing countermeasures to reduce 90Sr content in fish products.

Activity concentrations of 90Sr in fish in lakes located within the Chornobyl Exclusion Zone (ChEZ) reach 100 kBq kg-1, which is several thousand times higher than the permissible level in Ukraine (35 Bq kg-1). This study was conducted in the natural conditions of the ChEZ to determine the effectiveness of keeping radioactively contaminated fish in "clean" water to reduce the 90Sr content of their muscle tissue, as previously shown in short-term laboratory experiments. It was found that transferring tench (Tinca tinca (Linnaeus, 1758)) from Lake Glubokoye one of the most contaminated lakes in the ChEZ, to a cage in the "clean" Lake Starukha for 45 days did not lead to a significant decrease in 90Sr content in both bone and muscle tissues. Establishing permissible levels of 90Sr concentration only in fish fillet, and not in the whole fish body (with bone tissue), is appropriate for human radiation protection, since the retention factors of 90Sr treatment for boiled bone tissue of crucian carp from the Chornobyl exclusion zone are less than 0.01, and up to 97% of strontium is contained in bone tissue.

Seasonal variations in spatial distribution, mobilization kinetic and toxicity risk of arsenic in sediments of Lake Taihu, China.

This study investigated seasonal variations in spatial distribution, mobilization kinetic and toxicity risk of arsenic (As) in sediments of three representative ecological lakes in Lake Taihu. Results suggested that the bioavailability and mobility of As in sediments depended on the lake ecological types and seasonal changes. At the algal-type zones and macrophyte-type zones, elevated As concentrations were observed in April and July, while these occurred at the transition areas in July and October. The diffusion flux of soluble As ranged from 0.03 to 3.03 ng/cm2/d, indicating sediments acted as a source of As. Reductive dissolution of As-bearing iron/manganese-oxides was the key driver of sediment As remobilization. However, labile S(-II) caused by the degradations of algae and macrophytes buffered sediment As release at the algal-type and macrophyte-type zones. Furthermore, the resupply ratio was less than 1 at three ecological lakes, indicating the resupply As capacity of sediment solid phase was partially sustained case. The risk quotient values were higher than 1 at the algal-type zones and transition areas in July, thereby, the adverse effects of As should not be ignored. This suggested that it is urgently need to be specifically monitored and managed for As contamination in sediments across multi-ecological lakes.

Enhanced nutrient control efficiency in sediments using modified clay inactivation coupled with aquatic vegetation in the confluence area of a eutrophic lake.

Developing a long-term method for controlling sediment N and P release is important for enabling lake restoration. In this study, inactivation methods using lanthanum-modified clay, modified zeolite, or planting aquatic vegetation and their combinations were used in the control internal sediment loading (pore water N and P concentrations and their fluxes), and the efficacies of the methods were analyzed. The results indicated that compared to the control sediment, the addition of P sorbent, which was La and Al co-modified attapulgite (ACLA), and N sorbent, which was NaCl-modified zeolite (modified zeolite), planting of aquatic vegetation Vallisneria spiralis (V. spiralis), and a combination of sorbents and plants effectively reduced the porewater nutrient content and its fluxes across the sediment-water interface. However, the reduction in pore water nutrients and flux were superior when using a combination of clay inactivation and aquatic planting. The poorest sediment N and P control was achieved by planting V. spiralis alone. The addition of La and Al co-modified attapulgite (ACLA) and modified zeolite efficiently reduced N and P in the sediment, but the N and P sorbents did not achieve long-lasting nutrient release control. The high efficiency obtained by the combination of modified clay-based inactivation and V. spiralis was likely due to the strong chemical sorption capacity of clay and oxygenation by the rhizosphere of aquatic vegetation. These results show that a combination of chemical and ecological methods would be the most effective approach to remediate polluted sediments in the long term.

Determining the spatiotemporal variation, sources, and ecological processes of antibiotic resistance genes in a typical lake of the middle reaches of the Yangtze River.

Antibiotic resistance genes (ARGs) are emerging environmental pollutants, influenced by complex regulatory factors. River-lake systems act as natural reservoirs for ARGs and provide an ideal model for studying their regulatory mechanisms. This study employed high-throughput quantitative PCR, high-throughput sequencing, correlation analyses, and model predictions to investigate the dynamics of ARGs and their influencing factors in Liangzi Lake, located in the mid-reaches of the Yangtze River. The research specifically centered on three environmental components: lake water, sediment, and river water. Results indicated that the ARGs from eight major antibiotic classes, displaying distinct seasonal distribution patterns. In comparison to the sediment, the water phase demonstrated a higher diversity of ARGs, with the highest level of ARGs sharing observed between lake and river waters (approximately 83.7 %). Furthermore, seasonal variations significantly influenced the distributions of both ARGs and bacterial communities. The diversity of ARGs was highest during the summer and autumn, and specific bacterial species exhibited robust correlations with ARGs (including matA/mel, aac (6')-Ib-03, and blaROB). It is worth noting that environmental attributes and bacterial diversity had the most substantial impact on the dynamic changes in ARGs. Lastly, source tracking analysis pinpointed that sediment as the primary source of ARGs in lake water, constituting 45 % to 48 % of the total ARGs. Our study provides a comprehensive analysis of ARGs and their influencing factors in the river-lake system of the middle reaches of the Yangtze River, with Liangzi Lake as a representative case.

Spatial trends and ecotoxic risk assessment of selected pharmaceuticals in sediments from Lake Victoria, Uganda, East Africa.

Pharmaceutical residues in the aquatic environment are an emerging issue of global concern because of their effects on ecosystems including; antibacterial resistance development and endocrine disruption. Lake Victoria is the largest freshwater lake in Africa, and the second largest lake in the world. It is also the main source of the White Nile River, arguably the longest river in the world, flowing through South Sudan, Sudan, Ethiopia and Egypt, discharging into the Mediterranean Sea. However, its ecology is threatened by rapid industrialisation, urbanization, and increased agricultural activities, which have led to increased pollution via polluted runoffs. In this study, the occurrence of twenty-five pharmaceutical compounds (14 antibiotics, four anti-epileptic and antidepressant drugs, three analgesic and anti-inflammatory drugs, three beta-blockers, and one lipid regulator) was studied in 55 sediment samples obtained from the Ugandan sector of Lake Victoria, and their ecotoxic risk assessed. All the target compounds were quantifiable with levofloxacin (2-120 ng g-1 dm; dry mass), ciprofloxacin (3-130 ng g-1 dm) enoxacin (9-75 ng g-1 dm), ibuprofen (6-50 ng g-1 dm), metoprolol (1-92 ng g-1 dm) and propranolol (1-52 ng g-1 dm) being predominant. Murchison Bay, being the chief recipient of sewage effluents, municipal and industrial waste from Kampala city and its suburbs, had the highest levels. Ecotoxic risk assessment revealed that ciprofloxacin, levofloxacin, sulfamethoxazole, sulfamethazine, oxytetracycline, tetracycline, erythromycin, norfloxacin, ibuprofen, diclofenac, carbamazepine, atenolol, and metoprolol posed high toxic risks to sediment-dwelling organisms (risk quotients, RQ >1). This is the first study reporting concentrations and ecotoxic risks of pharmaceuticals in sediments of Lake Victoria, Uganda, and the whole of East Africa. Detection, identification and quantification of pharmaceuticals in Lake Victoria sediments is essential for gaining knowledge on their occurrence and fate which can ultimately be used to assist in constructing relevant policy and management recommendations.

Systematic loss in biotic heterogeneity but not biodiversity across multiple trophic levels in Erhai lake, China.

Anthropogenic disturbances and climate change have significantly altered the biotic composition across many ecosystems, leading to changes in biodiversity and even ecological collapse. An ecosystem comprises multiple trophic levels, and the issue how these disturbances affect their assembly processes remains unclear. Ecological stability of assemblages was maintained by their structure, and thus, revealing structure changes across trophic levels could improve our understanding of how ecosystems response to disturbances as a whole. In this study, we combined methods from palaeolimnology, ecology and network analysis, and observed the changes of biodiversity and network structure of two trophic levels (algae - diatoms and zoobenthos - chironomids) in Erhai lake, Southwest China over the last century. Results showed nutrient enrichment induced shifts in diatom and chironomid assemblages at ∼2001 CE, suggesting that the shift in Erhai lake may have occurred at multiple trophic levels. We found biodiversity exhibit different trends across trophic levels as it decreased in diatoms but increased in chironomids. However, network skewness declined in both trophic levels, indicating the common loss of biotic heterogeneity. The consistent decline of skewness among trophic levels long before the compositional shift is a potential parameter to warn of the shifts in lake ecosystems.

Modelling micropollutant cycle in Lake Como in a winter scenario: Implications for water use and reuse, ecosystem services, and the EU zero pollution action plan.

The fate and effects of 42 pharmaceuticals was studied in Lake Como (Italy), in wastewater treatment plants delivering water to the lake, in two rivers and in potable water obtained from lake water. Lake Como is one of the deepest and largest lakes in Northern Italy, serving important ecosystem services (i.e., drinking water, recreational, industrial, irrigation uses), some of which are currently at risk giving the current water scarcity and climate change scenarios. The highest concentrations measured in lake water were those of diclofenac, followed by carbamazepine, its metabolite, and clarithromycin. The data measured allowed to calibrate and run a fugacity-based lake model, which showed that the most important chemical load generally comes from the advective water from the north of the lake, rather than from the direct wastewater treatment plant (WWTP) discharges. This indicates that only an important reduction of chemical discharge (reduced use or extensive treatment) at a drainage basin level could significantly reduce concentrations in water. This has strong implications on how to implement the EU zero pollution action plan to significantly improve water ecosystem and human health protection.

Interaction between temperature and nutrients: How does the phytoplankton community cope with climate change?

Climate change and increasing nutrient concentrations are two major threats to lake ecosystems. Furthermore, warming is exacerbating the symptoms of eutrophication in freshwaters. Facing both environmental challenges simultaneously is more urgent than ever to preserve and recover water quality and protect the remaining biodiversity. Here, we used long-term observational data to investigate the phytoplankton response to the interaction between temperature and nutrient variations in a deep mesotrophic subalpine lake (L. Iseo, Italy). Despite the existing management programs, we observed a deterioration of the physicochemical status of the lake between 1993 and 2021 in the water column. The average rate of temperature increase was 0.02 °C y-1 across the studied period and accelerated after the last complete mixing events (2005 and 2006), particularly during the last decade (0.08 °C y-1). Water warming caused severe impacts on nutrient cycling, reflected by the overall increase in nutrient concentrations. The direct effect of warming was of great importance for phytoplankton, leading to an increase in total biovolume and a loss of diversity and promoting the dominance of Cyanobacteria. Nutrient variations, especially TN and the DSi:TP ratio, considerably structured the community composition. The modification of physicochemical parameters caused by the last complete mixing events led to a remarkable, long-term taxonomical and functional reorganization of the phytoplankton community. This study illustrates that phytoplankton in deep subalpine lakes will experience severe changes in the upcoming years, and that complete mixing events may constitute a threshold for community transformation. Our results stress the importance of using powerful interpretative models with multifaceted long-term datasets to disentangle the pathways by which temperature and nutrients could regulate the phytoplankton community. Our conclusions will help to integrate climate change into mitigation strategies to preserve ecosystem structure and functions.

Response mechanism of sediment endogenous phosphorus release to functional microorganisms and its cyanobacterial growth and disappearance effects.

Endogenous phosphorus (P) release from lake sediments is an important factor in the eutrophication of overlying waters, as P is the limiting nutrient salt affecting cyanobacterial growth. Microorganisms are also key to the evolution of cyanobacterial growth and disappearance, as they can influence the release of endogenous P. Meanwhile, endogenous phosphorus can also have an impact on microbial structure. However, there is a lack of studies on the response mechanisms between endogenous P release and microorganisms, as well as the exploration of endogenous P release on the whole cyanobacterial growth and disappearance evolution process. In this study, metagenome sequencing was used to characterize the microbial community structure at different times and to explain the P cycle from the perspective of functional genes. The results showed that the number of sediment microorganisms (genes) gradually increased with the P release capacity, and the outbreak with the strongest P release capacity possessed the most abundant microorganisms (genes). Proteobacteria with P solubilizing functions were consistently the most abundant phylum in all four periods and were positively correlated with P release potential assessment factors EPC0, EPC0F, and NAP. Functional genes affect the P cycle by acting primarily on inorganic P solubilization, organic P mineralization, and P transport. These P-functional genes are mainly found in Proteobacteria, Acidobacteria, Chloroflexi, and Actinobacteria microorganisms. In addition, the P form in the sediments was dominated by IP, with the highest concentration (704.86 mg/kg) occurring during the dormant period. Sediments from this period acted as a strong P "sink", creating a precondition for cyanobacterial recovery and outbreaks to provide a source of P. The results of this study can provide a theoretical basis for controlling endogenous P release at the microscopic level of cyanobacterial growth and disappearance.

The decomposition of algae has a greater impact on heavy metal transformation in freshwater lake sediments than that of macrophytes.

Heavy metal (HM) pollution is a major concern in freshwater ecosystem management. The different types of endogenous organic matter and the way their decomposition affects HM transformation in freshwater lakes is not well understood. An ex situ mesocosm study was conducted to compare HM transformation in sediments during anaerobic decomposition of cyanobacterial bloom biomass (CBB) and submerged cyanobacterial vegetation in Lake Taihu, known as Potamogeton malaianus (PM). Microbial community structures were examined through Illumina sequencing of 16S rDNA. Results indicate that Zn had a remarkably higher amount of potential mobile fraction than other heavy metals (Cr, Pb, Cu, Ni, and Cd) detected in sediments, especially in sediments collected from CBB-dominated areas (approximately 150 mg kg-1). CBB decomposition has caused a significant increase in exchangeable Zn content in sediments and a decrease in reducible Zn that was three times greater than PM decomposition. Additionally, oxidizable Zn content declined during CBB decomposition but increased during PM decomposition. Furthermore, the relative abundance of the main fermentative bacteria and some sulfate-reducing bacteria genera (e.g., Desulfomicrobium) were significantly associated with the HM content of exchangeable and reducible fractions during CBB decomposition. Overall, the findings indicate that Zn is more susceptible to endogenous organic matter decomposition than other metals in freshwater lakes, and the impacts of CBB decomposition on the transformation of heavy metals in sediment are greater than that of submerged macrophyte decomposition.

Visualization of microcystin-LR and sulfides in plateau lakes.

In eutrophic water bodies, sulfides are closely related to the growth of cyanobacteria and the production of microcystin-LR (MC-LR). To date, the underlying interaction mechanism between a sulfides and MC-LR remains controversial. Thus, visually presenting the distribution characteristics of sulfides and MC-LR in contaminated water is crucial. Here, we propose a novel and expeditious practical approach, utilizing fluorescence probe technology, to assess the distribution characteristics of MC-LR and sulfur in natural lakes. We have developed novel probes, pib2, to detect HSO3- and HS-, and pib18, to simultaneously identify MC-LR and sulfides. Through correlation analysis of fluorescence data and physicochemical indicators at sampling points, it is found that fluorescence data has good correlation with sulfides and MC-LR, and speculated that pib2 and pib18 may be able to detect sulfides and MC-LR in lakes. Using this method, we rapidly obtained the distribution of MC-LR and sulfur in Qilu and Erhai Lakes. Notably, for the first time, we rapidly displayed the distributions of sulfides and MC-LR across lakes by the fluorescent probe technology.

Fate of glyphosate in lakes with varying trophic levels and its modification by root exudates of submerged macrophytes.

Accelerated eutrophication in lakes reduces the number of submerged macrophytes and alters the residues of glyphosate and its degradation products. However, the effects of submerged macrophytes on the fate of glyphosate remain unclear. We investigated eight lakes with varying trophic levels along the middle and lower reaches of the Yangtze River in China, of which five lakes contained either glyphosate or aminomethylphosphate (AMPA). Glyphosate and AMPA residues were significantly positively correlated with the trophic levels of lakes (P < 0.01). In lakes, glyphosate is degraded through the AMPA and sarcosine pathways. Eight shared glyphosate-degrading enzymes and genes were observed in different lake sediments, corresponding to 44 degrading microorganisms. Glyphosate concentrations in sediments were significantly higher in lakes with lower abundances of soxA (sarcosine oxidase) and soxB (sarcosine oxidase) (P < 0.05). In the presence of submerged macrophytes, oxalic and malonic acids secreted by the roots of submerged macrophytes increased the abundance of glyphosate-degrading microorganisms containing soxA or soxB (P < 0.05). These results revealed that a decrease in the number of submerged macrophytes in eutrophic lakes may inhibit glyphosate degradation via the sarcosine pathway, leading to a decrease in glyphosate degradation and an increase in glyphosate residues.

Inhibition of algal blooms by residual antibiotics in aquatic environments: Design, screening, and validation of antibiotic alternatives.

Water blooms frequently appear in the aquatic environment with global warming. However, traditional methods for treating water bloom usually require the addition of algaecides, which may lead to secondary environmental pollution problems in the water environment. To solve this problem, researchers have initiated efforts to harness pre-existing chemical substances within aquatic environments to regulate algal blooms, thereby pioneering novel avenues for water body management. Therefore, an integrated approach involving molecular docking, molecular dynamics simulations, three-dimensional quantitative structure-activity relationship (3D-QSAR), and toxicokinetics methods were utilized for the molecular modification of fluoroquinolone antibiotics, to design and screen fluoroquinolone substitutes with improved toxicity of cyanobacteria and green algae, functionality, and environmental friendliness. A total of 143 fluoroquinolone alternatives were designed in this study, and lomefloxacin-6 (LOM6) was found as the optimum alternative to lomefloxacin (LOM), with increased toxicity to cyanobacteria and green algae by 31 % and 72 %. Molecular docking of LOM before and after modification with seven other cyanobacterial and green algal photosynthetic proteins revealed that LOM6 exhibited varying degrees of increased toxicity towards 6 of these photosynthetic proteins, of which 2J96 protein increased the most (136.25 %). It shows that the residual LOM6 in the water environment has a certain inhibitory effect on the algae bloom. In addition, results showed that LOM6 had synergistic toxic effects on cyanobacteria and green algae with other pollutants residual in the aqueous environment, such as trichloroethyl phosphate, triethyl phosphate, perfluorononanoic acid, perfluorooctanoic acid. This indicates that LOM6 has better algal removal effectiveness in aqueous environments where organophosphate flame retardants and perfluorinated compounds exist together. In this paper, a novel method was developed to remove cyanobacteria and green algae in water environment and reduce the secondary pollution through theoretical simulation, which provides theoretical support for the control of water blooms.

The Secchi disk depth to water depth ratio affects morphological traits of submerged macrophytes: Development patterns and ecological implications.

Water clarity, represented by Secchi disk depth (SD), and water depth (WD) alter bottom light availability, and SD/WD is critical for morphological trait development of submerged macrophytes in freshwater ecosystems. However, the underlying mechanism and trait development patterns of submerged macrophytes to a decreasing SD/WD gradient remains largely unknown. Here, we performed a 42-day mesocosm experiment with the erect type submerged macrophyte, Hydrilla verticillata, along a decreasing SD/WD gradient to study the relationship of morphological trait development with light availability, to determine the critical SD/WD at which changes in the development of morphological traits occur, and to gain insights into the potential mechanism involved. The results indicate that most of the morphological traits, including biomass, relative growth rate, number of clonal propagules, and the root/shoot ratio decreased with a decrease in the SD/WD ratio. Conversely, plant height and shoot increment rate increased with a decrease in the SD/WD ratio. Principal component analysis indicated that the SD/WD ratio is critical in determining the growth, stability, and reproduction of H. verticillata, and that only SD/WD ratios ≥ 0.45 and ≥0.55 ensured growth ability and stability, respectively. Possible development patterns of functional traits in relation to SD/WD reduction were investigated, and patterns of key traits of H. verticillata were distinct from those of Vallisneria natans, indicating different strategies for the adaptation to conditions of decreasing light availability. These results highlight the role of adaptive changes in morphology, resource allocation and life strategies for the maintenance of growth, stability and resilience of submerged macrophytes in low light conditions. Our present study provides a basis from which we could enhance our understanding of the critical transition mechanisms involved in morphological trait development in response to bottom light availability.

Differential gene expression and developmental pathologies associated with persistent organic pollutants in sentinel fish in Troutman Lake, Sivuqaq, Alaska.

Persistent organic pollutants (POPs) are lipophilic compounds that bioaccumulate in animals and biomagnify within food webs. Many POPs are endocrine disrupting compounds that impact vertebrate development. POPs accumulate in the Arctic via global distillation and thereby impact high trophic level vertebrates as well as people who live a subsistence lifestyle. The Arctic also contains thousands of point sources of pollution, such as formerly used defense (FUD) sites. Sivuqaq (St. Lawrence Island), Alaska was used by the U.S. military during the Cold War and FUD sites on the island remain point sources of POP contamination. We examined the effects of POP exposure on ninespine stickleback (Pungitius pungitius) collected from Troutman Lake in the village of Gambell as a model for human exposure and disease. During the Cold War, Troutman Lake was used as a dump site by the U.S. military. We found that PCB concentrations in stickleback exceeded the U.S. Environmental Protection Agency's guideline for unlimited consumption despite these fish being low trophic level organisms. We examined effects at three levels of biological organization: gene expression, endocrinology, and histomorphology. We found that ninespine stickleback from Troutman Lake exhibited suppressed gonadal development compared to threespine stickleback (Gasterosteus aculeatus) studied elsewhere. Troutman Lake stickleback also displayed two distinct hepatic phenotypes, one with lipid accumulation and one with glycogen-type vacuolation. We compared the transcriptomic profiles of these liver phenotypes using RNA sequencing and found significant upregulation of genes involved in ribosomal and metabolic pathways in the lipid accumulation group. Additionally, stickleback displaying liver lipid accumulation had significantly fewer thyroid follicles than the vacuolated phenotype. Our study and previous work highlight health concerns for people and wildlife due to pollution hotspots in the Arctic, and the need for health-protective remediation.

Measuring biodiversity vulnerability in French lakes - The IVCLA index.

Assessing the vulnerability of ecosystems to biodiversity loss has become increasingly crucial in conservation and ecology research. This study proposed a methodology for measuring lake vulnerability to biodiversity loss employing an established framework that combines three components. For this, we measured the resilience (functional redundancy) and sensitivity (an index considering three characteristics of rarity) components for fish and phytoplankton communities. We also measured the exposure component of the main stressors in lakes. We then combined the three components and calculated the vulnerability index (IVCLA) using data from 255 French lakes. We found that all lakes exhibited low levels of resilience, elevated sensitivity regarding average values for fish and phytoplankton groups, and medium exposure to stressors associated with human activities. In addition, there were some discrepancies in resilience and sensitivity patterns between fish and phytoplankton groups, emphasizing the importance of considering information from multiple biological groups when assessing ecosystem vulnerability. Hydrological alterations and low water quality were key stressors related to higher lake vulnerability. Most French lakes have been classified as exhibiting moderate vulnerability. It is crucial to emphasize the potential increase in exposure risks, which could lead to even higher vulnerability levels and, subsequently, biodiversity loss in the future. The IVCLA index offers several advantages, including integrating multiple taxa groups and stressors. We recommend incorporating additional data, such as the resilience and sensitivity of the entire food web, and considering temporal responses to stressors to improve accuracy and predictive power. The IVCLA was developed with the purpose of serving as an effective tool for guiding environmental managers in designing conservation strategies and making informed decisions for lake ecosystems.