Chlormequat inhibits Vallisneria natans growth and shapes the epiphytic biofilm microbial community.

Submerged macrophytes can overgrow and negatively affect freshwater ecosystems. This study aimed to investigate the use of chlormequat (CQ) to regulate submerged Vallisneria natans growth as well as its impact on the microbial community of epiphytic biofilms. V. natans height under CQ dosages of 20, 100, and 200 mg/L decreased within 21 days by 12.57%, 30.07%, and 44.62%, respectively, while chlorophyll content increased by 1.94%, 20.39%, and 38.83%. At 100 mg/L, CQ reduced the diversity of bacteria in the biofilm attached to V. natans leaves but increased the diversity of the eukaryotic microbial community. CQ strongly inhibited Cyanobacteria; compared with the control group, the treatment group experienced a significant reduction from 36.54% to 2.61%. Treatment significantly inhibited Gastrotricha and Rotifera, two dominant phyla of eukaryotes in the leaf biofilm, reducing their relative abundances by 17.41% and 6.48%, respectively. CQ significantly changed the leaf biofilm microbial community correlation network. The treatment group exhibited lower modularity (2.012) compared with the control group (2.249); however, the central network of the treated group contained a higher number of microbial genera (13) than the control group (4), highlighting the significance of eukaryotic genera in the network. The results obtained from this study provide invaluable scientific context and technical understanding pertinent to the restoration of submerged macrophytes within aquatic ecosystems. PRACTITIONER POINTS: Chlormequat reduced the plant height but increased leaf chlorophyll content. Chlormequat reduced biofilm bacterial diversity but increased eukaryotic diversity. Chlormequat affected the bacterial-fungal association networks in biofilms.

A preliminary study of carbon dioxide and methane emissions from patchy tropical seagrass meadows in Thailand.

Background: Seagrass meadows are a significant blue carbon sink due to their ability to store large amounts of carbon within sediment. However, the knowledge of global greenhouse gas (GHG) emissions from seagrass meadows is limited, especially from meadows in the tropical region. Therefore, in this study, CO2 and CH4 emissions and carbon metabolism were studied at a tropical seagrass meadow under various conditions. Methods: CO2 and CH4 emissions and carbon metabolism were measured using benthic chambers deployed for 18 h at Koh Mook, off the southwest coast of Thailand. The samples were collected from areas of patchy Enhalus acoroides, Thalassia hemprichii, and bare sand three times within 18 h periods of incubation: at low tide at 6 pm (t0), at low tide at 6 am (t1), and at high tide at noon (t2). Results: Seagrass meadows at Koh Mook exhibited varying CO2 and CH4 emissions across different sampling areas. CO2 emissions were higher in patchy E. acoroides compared to patchy T. hemprichii and bare sand areas. CH4 emissions were only detected in vegetated areas (patchy E. acoroides and T. hemprichii) and were absent in bare sand. Furthermore, there were no significant differences in net community production across sampling areas, although seagrass meadows were generally considered autotrophic. Koh Mook seagrass meadows contribute only slightly to GHG emissions. The results suggested that the low GHG emissions from Koh Mook seagrass meadows do not outweigh their role as significant carbon sinks, with a value 320 t CO2 -eq. This study provided baseline information for estimating GHG emissions in seagrass meadows in Thailand.

Sediment contamination alters the submersed macrophyte Vallisneria natans and root-associated microbiome profiles during phytoremediation.

The submerged plant Vallisneria natans plays an important role in the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated sediments. In this study, V. natans and sediments were collected from different V. natans natural vegetation zones, and sediment mesocosms were set up for phytoremediation tests. In addition, commercial-grade V. natans were obtained from the Fish-Bird-Flower market for comparison with phytoremediation. Phytoremediation using V. natans from natural growth significantly increased the degradation of PAHs in Dashui Harbor (0.0148±0.0015 d-1) and Taihu Lake bay sediments (0.0082±0.0010 d-1) but not in commercial-grade V. natans. Transplanted V. natans from natural growth had a significant (p=0.002) effect on PAH degradation, especially in highly PAH-contaminated sedimentary environments. The distinct bacterial communities were strongly affected by sediment type and V. natans type, which contributed to different phytoremediation patterns. Less complex but more stable microbial co-occurrence networks play key roles in improving PAH phytoremediation potential. In addition, V. natans from natural growth in highly PAH-contaminated sediment could adapt to PAH stress by exuding tryptophan metabolites to assemble health-promoting microbiomes. This study provides novel evidence that initial microbial and physicochemical characteristics of sediment and submerged plant types should be considered in the use of bioremediation management strategies for organic pollutant-contaminated sediments.

Nutrient-loaded seagrass litter experiences accelerated recalcitrant organic matter decay.

High coastal nutrient loading can cause changes in seagrass chemistry traits that may lead to variability in seagrass litter decomposition processes. Such changes in decomposition have the potential to alter the carbon (C) sequestration capacity within seagrass meadows ('blue carbon'). However, the external and internal factors that drive the variability in decomposition rates of the different organic matter (OM) types of seagrass are poorly understood, especially recalcitrant OM (i.e. cellulose-associated OM and lignin-associated OM), thereby limiting our ability to evaluate the C sequestration potential. It was conducted a laboratory incubation to compare differences in the decomposition of Halophila beccarii litter collected from seagrass meadows with contrasting nutrient loading histories. The exponential decay constants of seagrass litter mass, cellulose-associated OM and lignin-associated OM were 0.009-0.032, 0.014-0.054 and 0.009-0.033 d-1, respectively. The seagrass litter collected from meadows with high nutrient loading exhibited greater losses of mass (25.0-41.2 %), cellulose-associated OM (2.8-18.5 %) and lignin-associated OM (9.6-31.2 %) than litter from relatively low nutrient loading meadows. The initial and temporal changes of the litter nitrogen (N) and phosphorus (P) concentrations, stoichiometric ratios of lignin/N, C/N, and C/P, and cellulose-associated OM content, were strongly correlated with the losses of litter mass and different types of OM. Further, temporal changes of litter C and OM types, particularly the OM and labile OM concentrations, were identified as the main driving factors for the loss of litter mass and loss of different OM types. These results indicated that nutrient-loaded seagrass litter, characterized by elevated nutrient levels and diminished amounts of recalcitrant OM, exhibits an accelerated decay rate for the recalcitrant OM. These differences in litter quality would lead to a reduced contribution of seagrass litter to long-term C stocks in eutrophic meadows, thereby weakening the stability of C sequestration. Considering the expected changes in seagrass litter chemistry traits and decay rates due to long-term nutrient loading, this study provides useful information for improving C sequestration capabilities through effective pollution management.

Glufosinate-ammonium increased nitrogen and phosphorus content in water and shaped microbial community in epiphytic biofilm of Hydrilla verticillata.

Glufosinate-ammonium (GLAM) can be released into adjacent water bodies with rainfall runoff and return water from farmland irrigation. However, impacts of GLAM on aquatic organisms remain unclear. In this study, changes in water quality, plant physiological parameters and epiphytic microbial community were investigated in wetlands with Hydrilla verticillata exposed to GLAM for 24 days. We found GLAM addition damaged cell and reduced chlorophyll a content in Hydrilla verticillata leaves, and increased ammonium and phosphorus in water (p < 0.001). The α-diversity increased in bacterial community but decreased in eukaryotic community with GLAM exposure. Neutral community models explained 62.3 % and 55.0 % of the variance in bacterial and eukaryotic communities, respectively. Many GLAM micro-biomarkers were obtained, including some clades from Proteobacteria, Bacteroidete, Actinobacteriota, Phragmoplastophyta, Annelida and Arthropoda. Redundancy analysis revealed that GLAM concentration was positively correlated to Flavobacterium, Gomphonema and Closterium but negatively to Methyloglobulus and Methylocystis. Network analysis revealed that 15 mg/L GLAM disturbed the interactions among phytoplankton, protozoa, metazoan and bacteria and reduced the stability of the microbial communities compared to 8 mg/L GLAM. GLAM shaped the nitrogen and phosphorus cycle related bacterial genes. This study highlights that herbicides are non-neglectable factors affecting the efficiency of aquatic ecological restoration in agricultural areas to control agricultural non-point source pollution.

Pulsed sounds caused by internal oxygen transport during photosynthesis in the seagrass Halophila ovalis.

Oxygen bubbles that leak from seagrass blades during photosynthesis have been hypothesized to cause cavitation sounds in aquatic plants. Here we investigate low-amplitude sounds with regular pulse rates produced during photosynthesis in seagrass beds of Halophila ovalis (Qitou Bay, Penghu islands and Cigu Lagoon, Taiwan). Sound pulses appear in the morning when illumination exceeds 10,000 Lux, peak at midday and decrease in midafternoon on a sunny day. Frequencies peak between 1 to 4 kHz, durations range between ca. 1.8 to 4.8 ms, and sound pressure level 1 cm from the bed is 105.4 ± 0.5 dB re 1 µPa (1100 h on a cloudy day). Sounds attenuate rapidly with distance, disappearing beyond 15 cm. Blocking sunlight or administering herbicide stops ongoing sounds. Gas bubbles are not typically seen during sound production ruling out cavitation, and external force (scissor cutting or plant pressed against the substrate) applied to the patch, leaves, petioles, or rhizomes generally increases pulse rate. We suggest sound emission is caused by internal oxygen transport through pores in diaphragms (a whistle mechanism) at the leaf base and nodes of the rhizome.

Impact of manganese mining on potentially toxic elements pollution and bioaccumulation in Spirogyra varians and Hydrilla verticillata in the Xiaojiang River.

Potentially toxic elements (PTEs) pose a significant threat to aquatic ecosystems. This study investigated the content and potential sources of PTEs (Cr, Mn, Ni, Cu, Zn, Cd, Pb) in water, sediment, and dominant aquatic plants (Hydrilla verticillata and Spirogyra varians) in the Xiaojiang River, located near the Zhaiying manganese mine in Guizhou Province, China. Correlation analysis, principal component analysis (PCA), and cluster analysis were employed to assess PTE distribution and potential sources. Water PTE concentrations complied with the Class II standard (GB3838-2002), indicating no water pollution. However, sediment PTE levels exceeded background values, particularly Mn, which exhibited moderate to strong contamination. Cd also showed moderate contamination, posing a considerable ecological risk. Cd was the main potential pollutant with the highest contribution rate. Mn and Cd were therefore identified as priority pollutants requiring targeted abatement strategies. Mining activities likely represent the primary source, but combined pollution from vehicle traffic and agriculture might also contribute. Hydrilla verticillata demonstrated a higher capacity for PTE enrichment from sediment compared to Spirogyra varians, suggesting its potential for sediment remediation (except for Cu). A significant correlation existed between both plant species and sediment PTE content. PCA supported the association between S. varians and sediment PTEs. Linear regression analyses revealed better correlations between S. varians and sediment Mn, Ni, Cu, and Zn (0.77, 0.68, 0.82, and 0.79, respectively). Taken together, these findings suggest that S. varians serves as an effective bioindicator for monitoring sediment contamination with PTEs.

Unravelling the mechanisms of PFAS toxicity to submerged macrophytes and epiphytic biofilms at metabolic and molecular levels.

Per- and poly-fluoroalkyl substances (PFAS) are an emerging class of persistent organic pollutants that are widespread in aquatic ecosystems and pose a serious threat to aquatic organisms. It is thus crucial to explore the toxicity mechanisms of PFAS to submerged macrophytes and biofilms. In this study, Vallisneria natans (V. natans) was exposed to environmentally relevant concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS). Results showed that PFAS induced the excessive production of reactive oxygen species, triggering antioxidant responses. V. natans exhibited an improved stress tolerance by altering the biosynthesis of several plant secondary metabolites and the histidine, arginine, proline pathways in response to PFAS exposure. Moreover, PIP1-1, PIP2-2, SLAH1 and SLAH2 genes were upregulated, indicating the activation of aquaporins and slow-type anion channels. The uptake of PFOA and PFOS by V. natans was 41.74 % and 52.31 %, respectively. Notably, PFAS bound to functional proteins (GSTF10), promoting the detoxification of plants. Exposure to PFAS also altered the structure of biofilms by inducing the synthesis of large amounts of polysaccharides and proteins. The diversity and richness of the microbial community within periphytic biofilms changed significantly. These results provide a comprehensive description of the responses of aquatic plants and periphytic biofilms to PFAS and the removal mechanism of PFAS, contributing to the environmental risk assessments and removal of PFAS in aquatic ecosystems.

Cumulative effects of fish disturbance and vegetative propagules reduce the growth advantage of Vallisneria natans.

Benthivorous fish disturbance and density-dependent competition from adjacent macrophytes are two important biotic factors that significantly impact the growth of submerged macrophyte pioneer species, which is crucial for the success of eutrophication lake restoration. We conducted an outdoor mesocosm experiment to explore the individual and combined effects of these two factors on water quality and the growth of Vallisneria natans. The experiment involved two levels of fish (Misgurnus anguillicaudatus) disturbance crossed with two levels of Hydrilla verticillata vegetative propagule (shoot) intensity. The results showed that fish disturbance significantly increased the water column total nitrogen (TN), ammonia nitrogen (N-NH4), total phosphorus (TP), and phosphate­phosphorus (P-PO4). V. natans exhibited restricted plant height elongation and decreased soluble carbohydrate (SC) and starch concentration in fish treatments. Fish disturbance inhibited the growth advantage of V. natans by increasing the extinction coefficient of the water column. There was no statistical significance in total biomass between the two macrophytes in increased vegetative propagule and fish treatments. H. verticillata exhibited a higher relative growth rate (RGR) and summed dominance ratio (SDR3) than V. natans in four treatments and the treatment with three shoots of H. verticillata and one M anguillicaudatus, respectively. Fish disturbance and vegetative propagules showed cumulative effects that negatively affected the RGR_V.H (V. natans relative to H. verticillata). Our findings indicated that benthivorous fish disturbance and vegetative propagules could individually and cumulatively reduce the growth advantage of the pioneer species, V. natans. Our study sheds light on the accumulated effects of multiple disturbances that simultaneously occur in lakes, which holds theoretical and practical importance for lake restoration efforts.

The metabolic network response and tolerance mechanism of Thalassia hemprichii under high sulfide based on widely targeted metabolome and transcriptome.

Costal eutrophication leads to increased sulfide levels in sediments, which has been identified as a major cause of the global decline in seagrass beds. The seagrass Thalassia hemprichii, a dominant tropical species in the Indo-Pacific, is facing a potential threat from sulfide, which can be easily reduced from sulfate in porewater under the influence of global climate change and eutrophication. However, its metabolic response and tolerance mechanisms to high sulfide remain unclear. Thus, the current study investigated the physiological responses and programmed metabolic networks of T. hemprichii through a three-week mesocosm experiment, integrating physiology, stable isotope, widely targeted metabolomics, transcriptomics, and microbial diversity assessments. High sulfide reduced the sediment microbial diversity, while increased sediment sulfate reduced bacterial abundance and δ34S. The exposure to sulfide enhanced root δ34S while decreased leaf δ34S in T. hemprichii. High sulfide was shown to inhibit photosynthesis via damaging PSII, which further reduced ATP production. In response, abundant up-regulated differentially expressed genes in energy metabolism, especially in oxidative phosphorylation, were activated to compensate high energy requirement. High sulfide also promoted autophagy by overexpressing the genes related to phagocytosis and phagolysosome. Meanwhile, metabolomic profiling revealed that the contents of many primary metabolites, such as carbohydrates and amino acids, were reduced in both leaves and roots, likely to provide more energy and synthesize stress-responsive secondary metabolites. Genes related to nitrate reduction and transportation were up-regulated to promote N uptake for sulfide detoxification. High sulfide levels specifically enhanced thiamine in roots, while increased jasmonic acid and flavonoid levels in leaves. The distinct differences in metabolism between roots and leaves might be related to sulfide levels and the growth-defense trade-off. Collectively, our work highlights the specific mechanisms underlying the response and tolerance of T. hemprichii to high sulfide, providing new insights into seagrass strategies for resisting sulfide.

Anthropogenic microparticles accumulation in small-bodied seagrass meadows: The case of tropical estuarine species in Brazil.

Seagrass meadows have recently been highlighted as potential hotspots for microplastic and anthropogenic microparticles (APs). This study assessed AP accumulation in shallow sediments vegetated by small-bodied seagrass species (Halodule wrightii, Halophila decipiens, and H. baillonii) and in the adjacent unvegetated area in a tropical estuary on the East Coast of South America, Brazil, over the seasonal cycle. Anthropogenic microparticles were detected in 80 % of the samples, with a mean abundance of 142 ± 140 particles kg-1 dw (N = 80). Particles were predominantly blue (51 %), fiber (73 %), and smaller than 1 mm (80 %). We observed that seagrass sediments retained APs, although no significant variation was observed between seagrass and the unvegetated area, nor between the dry and rainy seasons. A positive correlation was found between sediment grain size and AP abundance. This study represents the first record of AP contamination in seagrasses from the Tropical Southwestern Atlantic bioregion.

Shifts in biodiversity and physical structure of seagrass beds across 5 decades at Carriacou, Grenadines.

Caribbean seagrass beds are facing increasing anthropogenic stress, yet comprehensive ground-level monitoring programs that capture the structure of seagrass communities before the 1980s are rare. We measured the distribution of seagrass beds and species composition and abundance of seagrass and associated macroalgae and macroinvertebrates in 3 years over a 47-year period (1969, 1994, 2016) at Carriacou, Granada, an area not heavily impacted by local human activity. Seagrass cover and physical parameters of fringing beds were measured in transects at high (HWE) and low wave energy (LWE) sites; frequency of occurrence of all species, and biomass and morphology of seagrasses, were measured at 100 m2 stations around the island. Losses in nearshore seagrass cover occurred at HWE but not LWE sites between 1969 and 2016 and were associated with increases in the seagrass-free inshore zone (SFI) and erosional scarps within beds. Total biomass did not vary across years although there were progressive changes in seagrass composition: a decline in the dominant Thalassia testudinum and concomitant increase in Syringodium filiforme, and establishment of invasive Halophila stipulacea in 2016 at LWE sites. Species richness and diversity of the seagrass community were highest in 1994, when 94% of macroalgae (excluding Caulerpa) were most abundant, and sea urchins were least abundant, compared to 1969 and 2016. Multivariate statistical analyses showed differences in community composition across the 3 years that were consistent with trends in urchin abundance. Increases in SFI and scarp number in seagrass beds at HWE sites occurred mainly after 1994 and likely were related to increased wave forcing following degradation of offshore coral reefs between 1994 and 2016. Our observations suggest that landward migration of seagrass beds with rapidly rising sea level in future will not be realized in reef-protected seagrass beds at Carriacou barring reversal in the processes that have caused reef flattening.

[Response of Water-Vallisneria natans-Sediment System to Polyethylene Microplastics].

The microplastics in aquatic ecosystems pose a serious threat to ecological security and environmental health, which have received widespread attention. To reveal the response of a water-Vallisneria natans-sediment system to microplastics exposure, the V. natans was exposed to polyethylene microplastics （PE-MPs） with different mass fractions （1%-5%, sediment wet mass fraction）, and the effects of PE-MPs on the physiochemical indicators of water quality, morphological characteristics of submerged plants, physiological characters, antioxidant system, and microbial community structure in sediments were studied respectively. The results showed that the physiochemical properties of the water body were not significantly changed in the PE-MPs treatment group, whereas the plant height, oxidative stress index, and antioxidant system were significantly inhibited. For the plant height, the 1% PE-MPs treatment group height was only 47.44% of that in the control group. Chlorophyll a content was 81.04% of that in the control group, and the activities of catalase （CAT）, malondialdehyde （MDA）, and peroxidase （POD） increased by 233.70%, 117.82%, and 61.62%, respectively. Different mass fractions of PE-MPs had a certain impact on microbial community structure in sediments. The above results are helpful to improve the evaluation system of PE-MPs ecological risk in the water-submerged plant-sediment system.

Coupled effects of redox-active substances and microbial communities on reactive oxygen species in rhizosphere sediments of submerged macrophytes.

Reactive oxygen species (ROS) play crucial roles in element cycling and pollutant dynamics, but their variations and mechanisms in the rhizosphere of submerged macrophytes are poorly investigated. This study investigated the light-dark cycle fluctuations and periodic variations in ROS, redox-active substances, and microbial communities in the rhizosphere of Vallisneria natans. The results showed sustained production and significant diurnal fluctuations in the O2•- and •OH from 27.6 ± 3.7 to 61.7 ± 3.0 µmol/kg FW and 131.0 ± 6.8 to 195.4 ± 8.7 µmol/kg FW, respectively, which simultaneously fluctuated with the redox-active substances. The ROS contents in the rhizosphere were higher than those observed in non-rhizosphere sediments over the V. natans growth period, exhibiting increasing-decreasing trends. According to the redundancy analysis results, water-soluble phenols, fungi, and bacteria were the main factors influencing ROS production in the rhizosphere, showing contribution rates of 74.0, 17.3, and 4.4 %, respectively. The results of partial least squares path modeling highlighted the coupled effects of redox-active substances and microbial metabolism. Our findings also demonstrated the degradation effect of ROS in rhizosphere sediments of submerged macrophytes. This study provides experimental evidence of ROS-related rhizosphere effects and further insights into submerged macrophytes-based ecological restoration.

Halophila stipulacea: A Comprehensive Review of Its Phytochemical Composition and Pharmacological Activities.

Halophila stipulacea (Forsskål and Niebuhr) Ascherson is a small marine seagrass that belongs to the Hydrocharitaceae family. It is native to the Red Sea, Persian Gulf, and Indian Ocean and has successfully invaded the Mediterranean and Caribbean Seas. This article summarizes the pharmacological activities and phytochemical content of H. stipulacea, along with its botanical and ecological characteristics. Studies have shown that H. stipulacea is rich in polyphenols and terpenoids. Additionally, it is rich in proteins, lipids, and carbohydrates, contributing to its nutritional value. Several biological activities are reported by this plant, including antimicrobial, antioxidant, anticancer, anti-inflammatory, anti-metabolic disorders, and anti-osteoclastogenic activities. Further research is needed to validate the efficacy and safety of this plant and to investigate the mechanisms of action underlying the observed effects.

Combining effects of submerged macrophytes and lanthanum-modified bentonite on sediment enzyme activity: Evidence from mesocosm study.

Lanthanum-modified bentonite (LMB) combined with submerged macrophytes (SM) has been a conventional means of eutrophication management in lakes in recent years, and is one of the most important methods for P removal. However, trends in nutrients and sediment enzymes at the water-sediment interface during this process have not been systematically assessed, and there are still some gaps in how abiotic properties drive changes in enzyme activity. Here, we show changes in aquatic environmental conditions under the action of different ratios of modified bentonite (0, 10%, 20%, and 30%) in combination with SM (Vallisneria natans, Potamogeton lucens, and Hydrilla verticillate) and quantify their effects on sediment enzyme activities. The results showed that the nutrient cycling at the water-sediment interface was facilitated by the combined effect of SM and LMB, which effectively reduced the overlying water nutrient concentration, increased the sediment enzyme activity and enhanced the N cycling process. Partial least squares structural equation model (PLS-SEM) showed that sediment parameters strongly influenced changes in enzyme activity, with NO3-N as the main controlling factors. Our study fills in the process of changing environmental conditions in lake water under geoengineered materials combined with macrophyte measures, especially the changes in biological properties enzyme activities, which contributes to a clearer understanding of nutrient fluxes during the management of eutrophication in lakes.

Turning waste into resources: A comprehensive review on the valorisation of Elodea nuttallii biomass.

This review focuses on the alternative uses of Elodea nuttallii (Planch.) H.St.John biomass. Elodea nuttallii is as an aquatic invasive alien species classified in the EU as a Species of Union Concern. Its dense monospecific stands affect both aquatic ecosystems and human activities, thereby requiring specific monitoring and management measures. The handling of E. nuttallii has a high economic cost, and the biomass removed from natural environments is considered a mere waste product. The need to implement circular economy, reducing waste and preserving natural capital, has led to the research for the reuse and valorisation of waterweed biomasses, such as E. nuttallii. This review critically assesses the feasibility and potential applications of E. nuttallii biomass in various sectors, including bioenergy production, extraction of metabolites, and fertilization. Out of more than 200 articles from 1965 to 2023, only 16 were found to deal with the use of harvested biomass, all within the last 12 years. This review highlights that the valorisation of E. nuttallii biomass is an underrepresented topic in scientific literature, and therefore in industrial sectors. Studies on biogas production are the most represented and have shown that E. nuttallii chemical composition is suitable for energy production, but is better suited as an additional feedstock to other biomasses already used for this purpose. New more cost-effective applications, such as animal feed and biosorbent, should be further addressed. By investigating alternative uses for E. nuttallii biomass, this review contributes to the development of sustainable practices that would turn a costly waste into a valuable resource.

Whole-genome sequencing of 13 Arctic plants and draft genomes of Oxyria digyna and Cochlearia groenlandica.

To understand the genomic characteristics of Arctic plants, we generated 28-44 Gb of short-read sequencing data from 13 Arctic plants collected from the High Arctic Svalbard. We successfully estimated the genome sizes of eight species by using the k-mer-based method (180-894 Mb). Among these plants, the mountain sorrel (Oxyria digyna) and Greenland scurvy grass (Cochlearia groenlandica) had relatively small genome sizes and chromosome numbers. We obtained 45 × and 121 × high-fidelity long-read sequencing data. We assembled their reads into high-quality draft genomes (genome size: 561 and 250 Mb; contig N50 length: 36.9 and 14.8 Mb, respectively), and correspondingly annotated 43,105 and 29,675 genes using ~46 and ~85 million RNA sequencing reads. We identified 765,012 and 88,959 single-nucleotide variants, and 18,082 and 7,698 structural variants (variant size ≥ 50 bp). This study provided high-quality genome assemblies of O. digyna and C. groenlandica, which are valuable resources for the population and molecular genetic studies of these plants.

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 colonized in 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 them, the community composition of epiphytic predators were more prone to change. Secondly, environmental filtering effects played a more important role in driving the community assembly of epiphytic predators than that of prey. Furthermore, the generality and intraguild predation of epiphytic predators were significantly improved within ecological restoration regions, which increased the stability of 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 regions. Overall, this study focused 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.

The native submerged plant, Hydrilla verticillata outperforms its exotic confamilial with exposure to polyamide microplastic pollution: Implication for wetland revegetation and potential driving mechanism.

Microplastic pollution and biological invasion, as two by-products of human civilization, interfere the ecological function of aquatic ecosystem. The restoration of aquatic vegetation has been considered a practical approach to offset the deterioration of aquatic ecosystem. However, a lack of knowledge still lies in the species selection in the revegetation when confronting the interference from microplastic pollution and exotic counterpart. The present study subjected the native submerged species, Hydrilla verticillata and its exotic confamilial, Elodea nuttallii to the current and future scenarios of polyamide microplastic pollution. The plant performance proxies including biomass and ramet number were measured. We found that the native H. verticillata maintained its performance while the exotic E. nuttallii showed decreases in biomass and ramet number under severest pollution conditions. The restoration of native submerged plant such as H. verticillata appeared to be more effective in stabilizing aquatic vegetation in the scenario of accelerating microplastic pollution. In order to explore the underlying driving mechanism of performance differentiation, stress tolerance indicators for plants, sediment enzymatic activity and sediment fungal microbiome were investigated. We found that polyamide microplastic had weak effects on stress tolerance indicators for plants, sediment enzymatic activity and sediment fungal diversity, reflecting the decoupling between these indicators and plant performance. However, the relative abundance of sediment arbuscular mycorrhizal fungi for H. verticillata significantly increased while E. nuttallii gathered "useless" ectomycorrhizal fungi at the presence of severest polyamide microplastic pollution. We speculate that the arbuscular mycorrhizal fungi assisted the stabilization of plant performance for H. verticillata with exposure to the severest polyamide microplastic pollution.