Evaluation of heavy metal accumulation and tolerance in oxalic acid-treated Phragmites australis wetlands for textile effluent remediation.

Water contamination with metals poses significant environmental challenges. The occurrence of heavy metals (HMs) prompts modifications in plant structures, emphasizing the necessity of employing focused safeguarding measures. Cadmium (Cd), lead (Pb), and chromium (Cr) emerge as particularly menacing toxins due to their high accumulation potential. Increasing the availability of organic acids is crucial for optimizing toxic metal removal via phytoremediation. This constructed wetland system (CWs) was used to determine how oxalic acid (OA) treatments of textile wastewater (WW) effluents affected morpho-physiological characteristics, antioxidant enzyme activity, oxidative stress, and HM concentrations in Phragmites australis. Multiple treatments, comprising the application of OA at a concentration of 10 mM and WW at different dilutions (25%, 50%, 75%, and 100%), were employed, with three replications of each treatment. WW stress decreased chlorophyll and carotenoid content, and concurrently enhanced HMs adsorption and antioxidant enzyme activities. Furthermore, the application of WW was found to elevate oxidative stress levels, whereas the presence of OA concurrently mitigated this oxidative stress. Similarly, WW negatively affected soil-plant analysis development (SPAD) and the total soluble proteins (SP) in both roots and shoots. Conversely, these parameters showed improvement with OA treatments. P. australis showed the potential to enhance HM accumulation under 100% WW stress. Specifically, there is an increase in root SP ranging from 9% to 39%, an increase in shoot SP from 6% to 91%, and an elevation in SPAD values from 4% to 64% compared to their respective treatments lacking OA inclusion. The OA addition resulted in decreased EL contents in the root and shoot by 10%-19% and 13%-15%, MDA by 9%-14% and 9%-20%, and H2O2 by 14%-21% and 9%-17%, in comparison to the respective treatments without OA. Interestingly, the findings further revealed that the augmentation of OA also contributed to an increased accumulation of Cr, Cd, and Pb. Specifically, at 100% WW with OA (10 mM), the concentrations of Cr, Pb, and Cd in leaves rose by 164%, 447%, and 350%, in stems by 213%, 247%, and 219%, and in roots by 155%, 238%, and 195%, respectively. The chelating agent oxalic acid effectively alleviated plant toxicity induced by toxins. Overall, our findings demonstrate the remarkable tolerance of P. australis to elevated concentrations of WW stress, positioning it as an eco-friendly candidate for industrial effluent remediation. This plant exhibits efficacy in restoring contaminants present in textile effluents, and notably, oxalic acid emerges as a promising agent for the phytoextraction of HMs.

HMs stress decreased the physiology and morphology of Phragmites australis L.OA improved the photosynthetic pigments and antioxidant enzymesHMs accumulation and bioavailability increased under OAPhragmites australis L. showed higher efficacy for textile effluent treatment under OA.

Chloroplast DNA methylation in the kelp Saccharina latissima is determined by origin and possibly influenced by cultivation.

DNA cytosine methylation is an important epigenetic mechanism in genomic DNA. In most land plants, it is absent in the chloroplast DNA. We detected methylation in the chloroplast DNA of the kelp Saccharina latissima, a non-model macroalgal species of high ecological and economic importance. Since the functional role of the chloroplast methylome is yet largely unknown, this fundamental research assessed the chloroplast DNA cytosine methylation in wild and laboratory raised kelp from different climatic origins (High-Arctic at 79° N, and temperate at 54° N), and in laboratory samples from these origins raised at different temperatures (5, 10 and 15°C). Results suggest genome-wide differences in methylated sites and methylation level between the origins, while rearing temperature had only weak effects on the chloroplast methylome. Our findings point at the importance of matching conditions to origin in restoration and cultivation processes to be valid even on plastid level.

Ecological restoration enhanced the stability of epiphytic microbial food webs of submerged macrophytes: Insights from predation characteristics of epiphytic predators.

The application of various submerged macrophytes for ecological restoration has gained increasing attention in urban lake ecosystems. The multitrophic microbial communities that colonize various submerged macrophytes constitute microbial food webs through trophic cascade effects, which affect the biogeochemical cycles of the lake ecosystem and directly determine the effects of ecological restoration. Therefore, it is essential to reveal the diversity, composition, assembly processes, and stability of the microbial communities within epiphytic food webs of diverse submerged macrophytes under eutrophication and ecological restoration scenarios. In this study, we explored the epiphytic microbial food webs of Vallisneria natans and Hydrilla verticillata in both eutrophic and ecological restoration regions. The obtained results indicated that the two regions with different nutrient levels remarkably affected the diversity and composition of epiphytic multitrophic microbial communities of submerged macrophytes, among which, epiphytic predators were more prone to changes in community composition. Secondly, environmental filtering effects were more dominant in the community assembly of epiphytic predators than of prey. Furthermore, the generality and intraguild predation of epiphytic predators were significantly improved within ecological restoration regions, which increased the stability of the epiphytic microbial food webs. Additionally, compared with Hydrilla verticillata, the epiphytic microbial food webs of Vallisneria natans exhibited higher multitrophic diversity and higher network stability regardless of the regions. Overall, this study focuses on the role of the epiphytic microbial food webs of submerged macrophytes in ecological restoration and uncovered the potential of epiphytic predators to enhance the stability of microbial food webs, which may provide new insights into the development of ecological restoration strategies.

Are recyclable plastics eco-friendly? Recycled PVC microplastics show higher toxicity than pristine PVC on Vallisneria natans, regardless of Cadmium.

As environmental awareness increases, the use of recyclable plastics has risen. However, it is currently unclear whether recycled microplastics (MPs) pose a lesser or greater environmental risk than pristine MPs. Cadmium (Cd), known for its toxicity to most organisms, can bind with MPs and accumulate in sediments. Few studies have explored the environmental risks posed by the coexistence of recycled MPs and pristine MPs with Cd to rooted macrophytes. We investigated the effects of recycled PVC MPs (R-PVC-MPs) and pristine PVC MPs (PVC-MPs) on Vallisneria natans in the presence and absence of Cd. Results showed that at moderate and high Cd levels, R-PVC-MPs reduced plant Cd enrichment. Despite this, the fresh weight of V. natans exposed to R-PVC-MPs was significantly lower than those exposed to PVC-MPs. Furthermore, R-PVC-MPs had more negative impacts on the physiological traits of V. natans than PVC-MPs, as chlorophyll was significantly reduced across all Cd levels. At high Cd levels, both R-PVC-MPs and PVC-MPs caused significantly high oxidative stress, with no significant differences observed. The PCoA plot showed that different MPs cause noticeable variations within the same Cd concentration. The trait network diagrams illustrated strong interactions among traits, with R-PVC-MPs showing the highest complexity. Lower average degree and decreased edge density indicate that traits of plants with R-PVC-MPs addition are more independent of each other. Our findings suggest that recycled PVC MPs pose a greater environmental risk than pristine PVC MPs, offering reference for assessing the risks of recycled plastics in freshwater ecosystems.

Macrophyte assisted phytoremediation and toxicological profiling of metal(loid)s polluted water is influenced by hydraulic retention time.

The present study reports findings related to the treatment of polluted groundwater using macrophyte-assisted phytoremediation. The potential of three macrophyte species (Phragmites australis, Scirpus holoschoenus, and Typha angustifolia) to tolerate exposure to multi-metal(loid) polluted groundwater was first evaluated in mesocosms for 7- and 14-day batch testing. In the 7-day batch test, the polluted water was completely replaced and renewed after 7 days, while for 14 days exposure, the same polluted water, added in the first week, was maintained. The initial biochemical screening results of macrophytes indicated that the selected plants were more tolerant to the provided conditions with 14 days of exposure. Based on these findings, the plants were exposed to HRT regimes of 15 and 30 days. The results showed that P. australis and S. holoschoenus performed better than T. angustifolia, in terms of metal(loid) accumulation and removal, biomass production, and toxicity reduction. In addition, the translocation and compartmentalization of metal(loid)s were dose-dependent. At the 30-day loading rate (higher HRT), below-ground phytostabilization was greater than phytoaccumulation, whereas at the 15-day loading rate (lower HRT), below- and above-ground phytoaccumulation was the dominant metal(loid) removal mechanism. However, higher levels of toxicity were noted in the water at the 15-day loading rate. Overall, this study provides valuable insights for macrophyte-assisted phytoremediation of polluted (ground)water streams that can help to improve the design and implementation of phytoremediation systems.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes.

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Exploring the ecotoxicological impact of meropenem on Lemna minor: Growth, photosynthetic activity, and oxidative stress.

Meropenem is a potent carbapenem antibiotic frequently used in medical settings. Several studies have confirmed the pervasive presence of these antibiotics in wastewater treatment plants and aquatic environments. However, the effects of these substances on non-target organisms, such as plants, have not been adequately monitored. Thus, this study aimed to assess the short-term impact of meropenem on the growth, photosynthesis, chlorophyll content, and enzyme activity of the macrophyte plant Lemna minor. The methods involved exposing the plant to meropenem under controlled conditions and assessing physiological and biochemical parameters to determine the impact on photosynthetic activity and oxidative stress. These analyses included growth rate, antioxidant enzyme activity, and photosynthetic capacity. The findings suggest that the growth rate of Lemna minor remained unaffected by meropenem at concentrations <200000 µgL-1. However, plants exposed to concentrations >20 µgL-1showed physiological alterations, such as decreased net photosynthesis rate (17%) and chlorophyll concentration (57%), compared to the control group. For acute toxicity assays, the calculated EC50 7-day and EC20 7-day were 1135 µgL-1and 33 µgL-1, respectively. In addition, in most treatments tested, meropenem caused an increase in the superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity as a defense mechanism against oxidative stress. Our results suggest that meropenem affects photosynthetic processes and induces oxidative stress in the macrophyte plant Lemna minor. Further studies are needed to assess the physiological and metabolic interactions between antibiotics and primary producers at different long-term trophic levels.

Genome-wide identification of the Q-type C2H2 zinc finger protein gene family and expression analysis under abiotic stress in lotus (Nelumbo nucifera G.).

BACKGROUND: Lotus (Nelumbo nucifera G.) is an important aquatic plant with high ornamental, economic, cultural and ecological values, but abiotic stresses seriously affect its growth and distribution. Q-type C2H2 zinc finger proteins (ZFPs) play an important role in plant growth development and environmental stress responses. Although the Q-type C2H2 gene family has been identified in some plants, limited reports has been carried out it in lotus. RESULTS: In this study, we identified 45 Q-type NnZFP members in lotus. Based on the phylogenetic tree, these Q-type NnZFP gene family members were divided into 4 groups, including C1-1i, C1-2i, C1-3i and C1-4i. Promoter cis-acting elements analysis indicated that most Q-type NnZFP gene family members in lotus were associated with response to abiotic stresses. Through collinearity analyses, no tandem duplication gene pairs and 14 segmental duplication gene pairs were identified, which showed that duplication events might play a key role in the expansion of the Q-type NnZFP gene family. The synteny results suggested that 54 and 28 Q-type NnZFP genes were orthologous to Arabidopsis and rice, respectively. The expression patterns of these Q-type NnZFP genes revealed that 30 Q-type NnZFP genes were expressed in at least one lotus tissue. Nn5g30550 showed relatively higher expression levels in all tested tissues. 12 genes were randomly selected with at least one gene from each phylogenetic clade, and the expression of these selected genes were confirmed by qRT-PCR (quantitative real-time polymerase chain reaction). The results indicated that Q-type NnZFP genes were extensively involved in cadmium, drought, salt and cold stresses responses. Among them, 11 genes responded to at least three different stress treatments, especially Nn2g12894, which induced by all four treatments. CONCLUSIONS: These results could increase our understanding of the characterization of the Q-type NnZFP gene family and provide relevant information for further functional analysis of Q-type NnZFP genes in plant development, and abiotic stress tolerance in lotus.

The characteristics and environmental significance of BVOCs released by aquatic macrophytes.

Biogenic volatile organic compounds (BVOCs) emitted by plants serve crucial biological functions and potentially impact atmospheric environment and global carbon cycling. Despite their significance, BVOC emissions from aquatic macrophytes have been relatively understudied. In this study, for the first time we identified there were 68 major BVOCs released from 34 common aquatic macrophytes, and these compounds referred to alcohols, aldehydes, alkanes, alkenes, arenes, ethers, furans, ketones, phenol. For type of BVOC emissions from different life form and phylogenetic group of aquatic macrophytes, 34 of the 68 BVOCs from emergent and submerged macrophytes are classified into alkene and alcohol compounds, over 50% BVOCs from dicotyledon and monocotyledon belong to alcohol and arene compounds. Charophyte and pteridophyte emitted significantly fewer BVOCs than dicotyledon and monocotyledon, and each of them only released 12 BVOCs. These BVOCs may be of great importance for the growth and development of macrophytes, because many BVOCs, such as azulene, (E)-ß-farnesene, and dimethyl sulfide are proved to play vital roles in plant growth, defense, and information transmission. Our results confirmed that both life form and phylogenetic group of aquatic macrophytes had significantly affected the BVOC emissions form macrophytes, and suggested that the intricate interplay of internal and external factors that shape BVOC emissions from aquatic macrophytes. Thus, further studies are urgently needed to investigate the influence factors and ecological function of BVOCs released by macrophytes within aquatic ecosystem.

Insight into the binding characteristics of dissolved organic matter(DOM)and Fe(â ¡)/Mn(â ¡): Based on the spectroscopic and dialysis equilibrium analysis.

Dissolved organic matter (DOM) plays an important role in metal migration and transformation within inland surface waters. In our study, spectroscopic and dialysis equilibrium analysis were combined to characterize the binding properties between DOM and Fe(II)/Mn(II). Four different type of DOM including two commercial DOM: humic acid、fulvic acid, and two natural dissolved organic matter collected from macrophyte-dominant region (MDR) and algae-dominated region (ADR) of Taihu Lake. Steady state/time resolved fluorescence spectroscopy indicated that the fluorescence intensity of DOM was quenched by Fe(II)/Mn(II) through a static quenching process. The adsorption isotherm shows that the adsorption capacity of DOM from Taihu Lake for metal ions is significantly higher than that of commercial humic acid. Simultaneously, the combination of MDR and Fe(II) has the highest adsorption capacity at 110.950 mg/g among all combinations. Furthermore, the Pseudo-second-order kinetic model and Elovich model were found to be superior in describing the adsorption process, with chemical adsorption controlling the rate of the adsorption reaction. The results of this study show that potentially toxic elements (PETs) pollution in eutrophic shallow lakes may become more serious due to the excessive expansion of algae dominant regions and the reduction of macrophyte dominant regions. In addition, risk analysis and assessment of PETs should consider the contribution of metal binding capabilities.

Does invasive submerged macrophyte diversity affect dissimilatory nitrate reduction processes in sediments with varying microplastics?

Nitrogen removal is essential for restoring eutrophic lakes. Microorganisms and aquatic plants in lakes are both crucial for removing excess nitrogen. However, microplastic (MP) pollution and the invasion of exotic aquatic plants have become increasingly serious in lake ecosystems due to human activity and plant-dominant traits. This field mesocosm study explored how the diversity of invasive submerged macrophytes affects denitrification (DNF), anammox (ANA), and dissimilatory nitrate reduction to ammonium (DNRA) in lake sediments with varying MPs. Results showed that invasive macrophytes suppressed DNF rates, but DNRA and ANA were less sensitive than DNF to the diversity of invasive species. Sediment MPs increased the biomass of invasive species more than native species, but did not affect microbial processes. The effects of MPs on nitrate dissimilatory reduction were process-specific. MPs increased DNF rates and the competitive advantage of DNF over DNRA by changing the sediment environment. The decoupling of DNF and ANA was also observed, with increased DNF rates and decreased ANA rates. The study findings suggested new insights into how the invasion of exotic submerged macrophytes affects the sediment nitrogen cycle complex environments.

Causes of macrophyte mass development and management recommendations.

Aquatic plants (macrophytes) are important for ecosystem structure and function. Macrophyte mass developments are, however, often perceived as a nuisance and are commonly managed by mechanical removal. This is costly and often ineffective due to macrophyte regrowth. There is insufficient understanding about what causes macrophyte mass development, what people who use water bodies consider to be a nuisance, or the potential negative effects of macrophyte removal on the structure and function of ecosystems. To address these gaps, we performed a standardized set of in situ experiments and questionnaires at six sites (lakes, reservoirs, and rivers) on three continents where macrophyte mass developments occur. We then derived monetary values of ecosystem services for different scenarios of macrophyte management ("do nothing", "current practice", "maximum removal"), and developed a decision support system for the management of water courses experiencing macrophyte mass developments. We found that (a) macrophyte mass developments often occur in ecosystems which (unintentionally) became perfect habitats for aquatic plants, that (b) reduced ecosystem disturbance can cause macrophyte mass developments even if nutrient concentrations are low, that (c) macrophyte mass developments are indeed perceived negatively, but visitors tend to regard them as less of a nuisance than residents do, that (d) macrophyte removal lowers the water level of streams and adjacent groundwater, but this may have positive or negative overall societal effects, and that (e) the effects of macrophyte removal on water quality, greenhouse gas emissions, and biodiversity vary, and likely depend on ecosystem characteristics and macrophyte life form. Overall, we found that aquatic plant management often does not greatly affect the overall societal value of the ecosystem, and we suggest that the "do nothing" option should not be easily discarded in the management of perceived nuisance mass developments of aquatic plants.

Phosphorus accumulation during the ice-on season in macrophyte-dominated eutrophic lakes and its implications.

Macrophyte overgrowth in eutrophic lakes can hasten the decline of shallow water bodies, yet the impact of macrophyte deposition on sediment phosphorus (P) accumulation in the ice-on season remains unclear. Comparative analyses of P variations among 13 semi-connected sub-lakes in Wuliangsu Lake in China, a typical MDE lake, considered external flow and macrophyte decomposition as driving forces. Sediment P fractions and water total phosphorus (TP) were analyzed at 35 sampling points across three ice-on season stages, along with macrophyte TP content to assess debris contributions. Our findings reveal that phosphorus accumulation occurs during the ice-on season in the MDE lake, with an average TP content increase of 16 mg/kg. However, we observed a surprisingly small sediment nutrient accumulation ratio (ΔTP/ΔTN=0.006) compared to macrophyte nutrient levels before decomposition. Further analysis of the dominant species, Potamogeton pectinatus, indicates that a significant portion (55%) of macrophyte phosphorus is released before the ice-on season. This highlights the critical importance of timing macrophyte harvesting to precede the phosphorus leaching process, which has implications for lake management and ecosystem restoration efforts. Additionally, our research demonstrates similar transformations among different sediment fractions as previously reported. Macrophyte debris decomposition likely serves as the primary source of Residual P (Res-P) or TP accumulation. In addition, Ca-bound P (Ca-P) generally showed a decrease, which mainly caused by its transformation to Fe/Al-bound P (Fe/Al-P), Exchange-P (Ex-P), and sometimes to Res-P. However, we emphasize the significant impacts of flow dynamics on Ca-P transport and transformations. Its hydrodynamic action increases water dissolved oxygen, which accelerates the transformation of Ca-P to more easily released Fe/Al-P and Ex-P. Furthermore, hydrodynamic transport also leads to upstream Ca-P transport to downstream. This underscores the necessity of considering flow dynamics when estimating phosphorus variations and formulating phosphorus restoration strategies.

Floating treatment wetlands with Canna indica for the removal of Cr(III) and Cr(VI) from water: A comprehensive study.

The efficiency in Cr (III) and Cr (VI) removal by Floating Treatment Wetlands (FTWs) vegetated with Canna indica, metal accumulation in sediment and plants were determined. Plant tolerance and its morphological response to metal were studied. Treatments were 5 and 10 mg L-1 of Cr(III) (5Cr(III) and 10Cr(III), respectively), and 5 and 10 mg L-1 of Cr(VI) (5Cr(VI) and 10Cr(VI), respectively), with and without FTWs, and a biological control (BC: with FTW without Cr addition). After 35 days, Total-Cr removals in treatments with FTW were 99.6 %, 96.9 %, 96.9 % and 81.7 % in 5Cr(III), 10Cr(III), 5Cr(VI) and 10Cr(VI), respectively. In Cr (III) treatments, the sediment from the reactors without FTW accumulated significantly more metal than the sediments with FTW, while the opposite occurred in the Cr(VI) treatments. Chromium in sediment was accumulated mainly bound to organic matter in all treatments (38-64 %). Roots of C. indica were the main Cr accumulator organ in all treatments (76-88 %). In 10Cr(VI) treatment, Cr was translocated to aerial parts resulting in a decrease in plant biomass and Chlorophyll a concentration. C. indica modified its internal and external root morphology as a mechanism to tolerate Cr toxicity, without affecting removal efficiencies. FTWs vegetated with C. indica were efficient in the remediation of water bodies contaminated with Cr. In addition, these systems have an aesthetic value because they use an ornamental species.

Fate and removal of fluoroquinolone antibiotics in mesocosmic wetlands: Impact on wetland performance, resistance genes and microbial communities.

The fate of fluoroquinolone antibiotics norfloxacin and ofloxacin were investigated in mesocosmic wetlands, along with their effects on nutrients removal, antibiotic resistance genes (ARGs) and epiphytic microbial communities on Hydrilla verticillate using bionic plants as control groups. Approximately 99% of norfloxacin and ofloxacin were removed from overlaying water, and H. verticillate inhibited fluoroquinolones accumulation in surface sediments compared to bionic plants. Partial least squares path modeling showed that antibiotics significantly inhibited the nutrient removal capacity (0.55) but had no direct effect on plant physiology. Ofloxacin impaired wetland performance more strongly than norfloxacin and more impacted the primary microbial phyla, whereas substrates played the most decisive role on microbial diversities. High antibiotics concentration shifted the most dominant phyla from Proteobacteria to Bacteroidetes and inhibited the Xenobiotics biodegradation function, contributing to the aggravation in wetland performance. Dechloromonas and Pseudomonas were regarded as the key microorganisms for antibiotics degradation. Co-occurrence network analysis excavated that microorganisms degrade antibiotics mainly through co-metabolism, and more complexity and facilitation/reciprocity between microbes attached to submerged plants compared to bionic plants. Furthermore, environmental factors influenced ARGs mainly by altering the community dynamics of differential bacteria. This study offers new insights into antibiotic removal and regulation of ARGs accumulation in wetlands with submerged macrophyte.

Improving species distribution forecasts by measuring and communicating uncertainty: An invasive species case study.

Forecasting invasion risk under future climate conditions is critical for the effective management of invasive species, and species distribution models (SDMs) are key tools for doing so. However, SDM-based forecasts are uncertain, especially when correlative statistical models extrapolate to nonanalog environmental domains, such as future climate conditions. Different assumptions about the functional form of the temperature-suitability relationship can impact predicted habitat suitability under novel conditions. Hence, methods to understand the sources of uncertainty are critical when applying SDMs. Here, we use high-resolution predictions of lake water temperatures to project changes in habitat suitability under future climate conditions for an invasive macrophyte (Myriophyllym spicatum). Future suitability was predicted using five global circulation models and three statistical models that assumed different species-temperature functional responses. The suitability of lakes for M. spicatum was overall predicted to increase under future climate conditions, but the magnitude and direction of change in suitability varied greatly among lakes. Variability was most pronounced for lakes under nonanalog temperature conditions, indicating that predictions for these lakes remained highly uncertain. Integrating predictions from SDMs that differ in their species-environment response function, while explicitly quantifying uncertainty across analog and nonanalog domains, can provide a more robust and useful approach to forecasting invasive species distribution under climate change.

The response of structure and nitrogen removal function of the biofilm on submerged macrophytes to high ammonium in constructed wetlands.

The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands (CWs). The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies. In this paper, the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V. natans plants were measured at different initial ammonium concentrations. The results demonstrated that the total chlorophyll and soluble sugar synthesis of V. natans plants decreased by 51.45% and 57.16%, respectively, and malondialdehyde content increased threefold after 8 days if the initial NH4+-N concentration was more than 5 mg/L. Algal density, bacterial quantity, dissolved oxygen, and pH increased with high ammonium shocks. The average removal efficiencies of total nitrogen and NH4+-N reached 73.26% and 83.94%, respectively. The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria, Cyanobacteria, and Bacteroidetes increased. The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification (HNAD) bacteria expanded in biofilms. In particular, HNAD bacteria of Flavobacterium, Hydrogenophaga, Acidovorax, Acinetobacter, Pseudomonas, Aeromonas, and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V. natans plants. The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway. Thus, the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.

Seasonal dynamics of the standard test species Lemna sp. in outdoor microcosms.

Lemna L. sp. is a free-floating aquatic macrophyte that plays a key role as a standard test species in aquatic risk assessment for herbicides and other contaminants. Population modeling can be used to extrapolate from laboratory to field conditions. However, there are insufficient data on longer-term seasonal dynamics of this species to evaluate such models. Therefore, several long-term growth experiments were conducted in outdoor microcosms (surface area 0.174 m2). Monitoring parameters included biomass, frond numbers, water parameters, and weather data. Three different datasets were generated: frond numbers and biomass from weekly to monthly destructively sampled microcosms; a year-round dataset of frond numbers from five continuously monitored microcosms; and seasonal growth rates without the effect of density dependence over 1-2 weeks in freshly inoculated microcosms. Lemna sp. reached a maximum of approximately 500 000 fronds m-2 and 190 g dry weight m-2. During the first winter, the microcosms were covered by ice for approximately four weeks, and Lemna sp. populations collapsed. The second winter was warmer, without any ice cover, and Lemna sp. populations maintained high abundance throughout the winter. Dry weight per frond was not constant throughout the year but was highest in autumn and winter. Growth rates without density dependence under outdoor environmental conditions reached 0.29 day-1 for frond number, 0.43 day-1 for fresh weight, and 0.39 day-1 for dry weight. In linear regressions, these growth rates were best explained by water temperature. For the populations continuously monitored throughout a year, the nitrogen-to-phosphorus ratio best explained the growth rate of frond numbers. This study yielded a relevant dataset for testing and refining Lemna population models used in chemical risk assessment as well as for managing ecosystems and combating the effects of eutrophication. Integr Environ Assess Manag 2024;00:1-14. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Responses of Vallisneria natans and Pistia stratiotes to Cu2+ and Mn2+ stress: Occurrence of caffeic acid and its degradation kinetics during chlorination.

Macrophytes are crucial in maintaining the equilibrium of aquatic ecosystems. However, the pattern of macrophyte-derived caffeic acid (CA) release under heavy metal stress is yet to be fully understood. More importantly, due to its functional groups, CA may be a precursor to the formation of disinfection by-products, posing threats to water ecology and even safety of human drinking water. This study analyzed the responses of CA released by Vallisneria natans (V. natans) and Pistia stratiotes (P. Stratiotes) when exposed to Cu2+ and Mn2+ stress. Additionally, the CA levels in two constructed wetland ponds were detected and the degradation kinetics of CA during chlorination were investigated. Results indicated that CA occurred in two constructed wetland ponds with the concentrations of 44.727 µg/L (planted with V. natans) and 61.607 µg/L (planted with P. Stratiotes). Notably, heavy metal stress could significantly affect CA release from V. natans and P. Stratiotes. In general, under Cu2+ stress, V. natans secreted far more CA than under Mn2+ stress, the level could reach up to 435.303 µg/L. However, compared to V. natans, P. Stratiotes was less affected by Cu2+ and Mn2+ stress, releasing a maximum CA content of 55.582 µg/L under 5 mg/L Mn2+ stress. Aquatic macrophytes secreted more CA in response to heavy metal stresses and protected macrophytes from harmful heavy metals. CA degradation followed the pseudo first-order kinetics model, and the chlorination of CA conformed to a second-order reaction. The reaction rate significantly accelerated as NaClO, pH, temperature and Br- concentration increased. A new pathway for CA degradation and a new DBP 2, 2, 3, 3-tetrachloropropanal were observed. These findings pointed at a new direction into the adverse effect of CA, potentially paving the way for new strategies to solve drinking water safety problems.