Search Results (17)

An aqueous leaf extract of Egeria densa was used to green-synthesize iron (II) and iron (III) oxide nanoparticles from ferrous sulphate and ferric chloride, respectively. The successful green synthesis of the nanoparticles was confirmed through UV–visible spectroscopy, and the colour of the mixtures changed from light-yellow to green-black and reddish-brown for FeO–NPs and Fe₂O₃–NPs, respectively. The morphological characteristics of the nanoparticles were determined using an X-ray diffractometer (XRD), a Fourier transform infrared spectrophotometer (FTIR), a transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDX). The UV–Vis spectrum of the FeO–NPs showed a sharp peak at 290 nm due to the surface plasmon resonance, while that of the Fe₂O₃–NPs showed a sharp peak at 300 nm. TEM analysis revealed that the FeO–NPs were oval to hexagonal in shape and were clustered together with an average size of 18.49 nm, while the Fe₂O₃-NPs were also oval to hexagonal in shape, but some were irregularly shaped, and they clustered together with an average size of 27.96 nm. EDX analysis showed the presence of elemental iron and oxygen in both types of nanoparticles, indicating that these nanoparticles were essentially present in oxide form. The XRD patterns of both the FeO–NPs and Fe₂O₃–NPs depicted that the nanoparticles produced were crystalline in nature and exhibited the rhombohedral crystal structure of hematite. The FT-IR spectra revealed that phenolic compounds were present on the surface of the nanoparticles and were responsible for reducing the iron salts into FeO–NPs and Fe₂O₃–NPs. Conclusively, this work demonstrated for the first time the ability of Elodea aqueous extract to synthesize iron-based nanoparticles from both iron (II) and iron (III) salts, highlighting its versatility as a green reducing and stabilizing agent. The dual-path synthesis approach provides new insights into the influence of the precursor oxidation state on nanoparticle formation, thereby expanding our understanding of plant-mediated nanoparticle production and offering a sustainable route for the fabrication of diverse iron oxide nanostructures. Furthermore, it provides a simple, cost-effective, and environmentally friendly method for the synthesis of the FeO–NPs and Fe₂O₃–NPs using Egeria densa. Full article

Coastal wetlands provide critical ecological services but are threatened by the human, climatic, and hydrological changes impacting these ecosystems. Several key ecosystem services and functions rely on aquatic macrophyte plant species. We integrate 10 years of seasonal monitoring data (2014–2024) and climatic and hydrological datasets to assess how environmental variability influences two dominant aquatic macrophytes—the invasive and non-indigenous Elodea densa Planch. Casp. (Hydrocharitaceae) and the native Schoenoplectus californicus (C.A.Mey.) Soják—in Chile’s first Ramsar site, Carlos Anwandter, and a Nature Sanctuary. We modeled suitable habitat areas using MaxEnt software with Landsat 8 spectral bands and indices as predictive layers. We found significant recent decreases in temperature, river flow, and water level, with a nonsignificant shift in precipitation. We also observed marked spatial and temporal fluctuations in areas with suitable habitat areas for both macrophytes. Stepwise regression analyses indicated that Elodea densa expanded with increasing temperature over time but declined with water level variability. Schoenoplectus californicus showed contrasting effects, declining with rising temperature and water levels but expanding with higher precipitation. These findings emphasize the complexity of coastal wetland ecosystems under environmental stress and climate change and the need for further research for the conservation and management of coastal wetlands along migratory flyways such as the Southeastern Pacific Flyway. Full article

This study investigates the potential of macrophytes as biostimulants in agricultural applications through a two-stage experimental approach. In the first stage, a screening experiment evaluated 12 macrophyte species using ethanolic and potassium chloride extracts at two doses (1 and 5 kg fresh biomass/ha) applied to bioindicator species Cucumis sativus (C3) and Urochloa decumbens (C4). Controlled greenhouse conditions and randomized block designs ensured reliability. Dry biomass was measured 21 days after treatment (DAT), revealing varied macrophyte effects. Ethanolic extracts of Typha domingensis and Egeria densa demonstrated significant biomass increases, particularly for U. decumbens, while potassium chloride extracts often reduced biomass. E. densa was selected for further analysis due to its promising results and ease of selective harvesting. In the second stage, a dose–response experiment assessed the impact of E. densa ethanolic extracts on Phaseolus vulgaris at six doses (0.25 to 4 kg fresh biomass/ha). Optimal results were observed at 1–2 kg/ha, yielding 15% increases in plant height and dry biomass. Higher doses showed diminishing returns. These findings highlight the potential of E. densa as a sustainable biostimulant and a solution for macrophyte overabundance in Brazilian reservoirs, supporting agricultural and environmental objectives. Full article

Communities with high native species diversity tend to be less susceptible to the establishment of invasive species, especially in studies that test their local impact. This study investigated the impact of competition between native submerged aquatic macrophytes (SAMs) (Egeria najas and Egeria densa) and the exotic Hydrilla verticillata, recognized for its invasive potential in aquatic ecosystems, through a mesocosm experiment conducted over six months. Two treatments were evaluated: the intraspecific competition of H. verticillata and an interspecific competition involving all three species. The plants were cultivated under controlled conditions, with the foliar and subterranean biomass being monitored to analyze resource allocation patterns. The results showed that, under interspecific competition, the mean foliar biomass of H. verticillata was significantly higher compared to the intraspecific treatment, while the subterranean biomass was reduced in the presence of native species. We conclude that native species alter the biomass allocation pattern of the invader, favoring foliar structures over subterranean ones. Among the mechanisms of invasiveness, differential resource allocation represents an important strategy for the adaptation and competitiveness of invasive species influenced by environmental factors and resource competition. These findings contribute to the understanding of competitive interactions in aquatic ecosystems and have implications for the management and control of invasive species, highlighting the importance of promoting native diversity to mitigate invasibility. Future studies should investigate the impacts of reduced subterranean structures on the persistence and spread of submerged invasive species. Full article

The development of aquatic plant beds can obstruct boat traffic, hinder the practice of water activities, and impact the functioning of freshwaters. In order to mitigate their effects, mechanical removal is often the preferred management solution. The objective of this study was to test, in mesocosms, the effect of frequency (none, one, and two cuts) and cutting dates (May and/or July) on the regeneration and colonization capabilities of the aquatic plant Egeria densa, an invasive alien species in France. The cutting date had no effect on the capabilities of E. densa, but the two cuts significantly reduced the plant’s biomass. Removal produced numerous fragments, which exhibited very high survival and anchoring rates. However, summer removal produced fragments with lower regeneration and colonization abilities compared to fragments from spring cutting. Mechanical removal only temporarily reduced the biomass of the aquatic plant beds and could promote the formation of new beds from the fragments generated by management and dispersed by water flow. Full article

This study aimed to investigate the allelopathic effect of live Egeria densa Planch. and its aqueous extracts in inhibiting the cyanobacterium Microcystis aeruginosa (Kützing) Lemmermann through a possible growth inhibition pathway. Under coexistence, the presence of live E. densa reduced the growth of M. aeruginosa by 48% compared to when M. aeruginosa was alone. Consequently, we prepared two separate aqueous extracts with distilled water: one from E. densa plants collected from monocultures, and the other from E. densa plants collected from co-cultivation with M. aeruginosa. At a concentration of 0.5 g/L, both extracts successfully suppressed the growth of M. aeruginosa throughout the 5-day exposure period. The extracts obtained from E. densa plants grown in a combined culture with M. aeruginosa showed significant growth-inhibiting capabilities compared to the extracts obtained from E. densa monoculture (p < 0.05). They showed 22% more growth inhibition compared to cultures exposed to monoculture extracts at day 5, indicating that the production of allelochemicals in E. densa was induced during co-existence with cyanobacteria. However, the higher concentrations (2 and 4 g/L) of both extracts did not effectively exhibit a successful inhibitive ability, possibly due to the presence of high nutrient concentrations, specifically PO₄³⁻, which may be potentially suppressing the activity of allelochemicals. Further studies are recommended in identifying the specific allelochemicals and exploring their practical implementation in the field. Full article

Macrophytes have demonstrated excellent potential for the removal of pharmaceuticals from water. However, there is a lack of studies on the ecotoxicity of water after phytoremediation. In this study, we evaluated the toxicity of ciprofloxacin (Cipro) on the microalgae cells of Desmodesmus subspicatus exposed to water contaminated with Cipro and previously treated by Salvinia molesta or Egeria densa for 96 h. Microalgae exposed to Cipro (1, 10, and 100 µg L⁻¹) in untreated water showed decreased rates of growth, respiration, and photosynthesis, and increased oxidative status (hydrogen peroxide concentration) and oxidative damages (lipid peroxidation). S. molesta exhibited a greater phytoremediation capacity than E. densa, reducing Cipro concentrations in water to below its toxic threshold to D. subspicatus (2.44 µg L⁻¹), even when the antimicrobial was present at a concentration of 10 µg L⁻¹. During the water treatment, neither S. molesta nor E. densa released compounds that had a toxic effect on D. subspicatus. This work demonstrates the novelty of using S. molesta and E. densa as a nature-based solution to remove Cipro from contaminated water. For the first time, we provide evidence of the ecotoxicological safety of this approach, as it prevents the deleterious effects of Cipro on photosynthetic microorganisms and helps to avoid the development of antimicrobial resistance. Full article

Submerged macrophytes promote water clarity in shallow lakes in temperate regions via zooplankton refuge, allelopathy, and nutrient competition with phytoplankton, thereby increasing zooplankton grazing. However, in high-altitude Andean ecosystems, these interactions in shallow lakes have received far less attention. To understand the role of submerged plants in a relatively cold ecosystem (typical for the Andean region), two 100 L experiments were conducted in Yahuarcocha Lake, which has a permanent cyanobacterial bloom. In our first experiment, we evaluated the response of the cyanobacteria bloom to different concentrations of Egeria densa (15%, 35%, and 45% PVI). In the second experiment, we investigated the interactions between E. densa (35% PVI), zooplankton, and the small-sized fish Poecilia reticulata as well as their impacts on phytoplankton. We found a strong reduction in cyanobacteria in the presence of E. densa, whereas P. reticulata promoted cyanobacteria dominance and zooplankton had a null effect on phytoplankton. Remarkably, the combination of E. densa, fish, and zooplankton substantially reduced the algae. Our findings showed that the cyanobacteria bloom decreased in the presence of E. densa, thereby increasing the water clarity in the high-elevation eutrophic ecosystem in the Andes. This effect depended on the plant volume inhabited and the small-sized fish biomass. Full article

Invasive plants efficiently colonize non-native territories, suggesting a great production of bioactive metabolites which could be effective antibiofilm weapons. Our study aimed to look for original molecules able to inhibit bispecies biofilm formed by S. aureus and C. albicans. Extracts from five invasive macrophytes (Ludwigia peploides, Ludwigia grandiflora, Myriophyllum aquaticum, Lagarosiphon major and Egeria densa) were prepared and tested in vitro against 24 h old bispecies biofilms using a crystal violet staining (CVS) assay. The activities of the extracts reducing the biofilm total biomass by 50% or more were comparatively analyzed against each microbial species forming the biofilm by flow cytometry (FCM) and scanning electron microscopy. Extracts active against both species were fractionated. Obtained fractions were analyzed by UHPLC-MS/MS and evaluated by the CVS assay. Chemical and biological data were combined into a bioactivity-based molecular networking (BBMN) to identify active compounds. The aerial stem extract of L. grandiflora showed the highest antibiofilm activity (>50% inhibition at 50 µg∙mL⁻¹). The biological, chemical and BBMN investigations of its fractions highlighted nine ions correlated with the antibiofilm activity. The most correlated compound, identified as betulinic acid (BA), inhibited bispecies biofilms regardless of the three tested couples of strains (ATCC strains: >40% inhibition, clinical isolates: ≈27% inhibition), confirming its antibiofilm interest. Full article

The aquaculture industry in Brazil has grown immensely resulting in the production of inefficiently discarded wastewater, which causes adverse effects on the aquatic ecosystem. The efficient treatment of aquaculture wastewater is vital in reaching a sustainable and ecological way of fish farming. Bioremediation in the form of the Green Liver System employing macrophytes was considered as wastewater treatment for a tilapia farm, COOPVALE, in Itacuruba, Brazil, based on previously demonstrated success. A large-scale system was constructed, and the macrophytes Azolla caroliniana, Egeria densa, Myriophyllum aquaticum, and Eichhornia crassipes were selected for phytoremediation. As cyanobacterial blooms persisted in the eutrophic wastewater, two microcystin congeners (MC-LR and -RR) were used as indicator contaminants for system efficiency and monitored by liquid-chromatography–tandem-mass-spectrometry. Two trial studies were conducted to decide on the final macrophyte selection and layout of the Green Liver System. In the first trial, 58% MC-LR and 66% MC-RR were removed and up to 32% MC-LR and 100% MC-RR were removed in the second trial. Additional risks that were overcome included animals grazing on the macrophytes and tilapia were spilling over from the hatchery. The implementation of the Green Liver System significantly contributed to the bioremediation of contaminants from the fish farm. Full article

Cylindrospermopsin (CYN) is being detected in surface waters more commonly and frequently worldwide. This stable, extracellular cyanotoxin causes protein synthesis inhibition, thus posing a risk to aquatic biota, including macrophytes, which serve as primary producers. Nevertheless, data regarding the effects caused by environmental concentrations of CYN is still limited. In the presented study, the uptake of CYN at environmental concentrations by the submerged macrophyte Egeria densa was investigated. Bioaccumulation, changes in the plant biomass, as well as shoot-length were assessed as responses. Variations in the cellular H₂O₂ levels, antioxidative enzyme activities, as well as concentrations and ratios of the photosynthetic pigments were also measured. E. densa removed 54% of CYN within 24 h and up to 68% after 336 h; however, CYN was not bioaccumulated. The antioxidative enzyme system was activated by CYN exposure. Pigment concentrations decreased with exposure but normalized after 168 h. The chlorophyll a to b ratio increased but normalized quickly thereafter. Carotenoids and the ratio of carotenoids to total chlorophylls increased after 96 h suggesting participation in the antioxidative system. Growth stimulation was observed. The ability to remove CYN and resistance to CYN toxicity within 14 days proved E. densa as suitable for phytoremediation; nonetheless, prolonged exposure (32 days) resulted in adverse effects related to CYN uptake, which needs to be studied further. Full article

Biofuels are seen as a potential option for mitigating the effects of fossil fuel use. On the other hand, nutrient pollution is accelerating eutrophication rates in rivers, lakes, and coastal waters. Harvesting aquatic plants to produce biofuels could mitigate this problem, though it is important to attack the problem at source, mainly as regards the contribution of nutrients. For the first time, solid biofuels were obtained in the forms of carbon and pellets from the aquatic plants Egeria densa, which is classed as an invasive plant under the Spanish Catalogue of Exotic Invasive Species, and Lemna minor, both of which can be found in the Umia River in north-west Spain. The essential oils and macro- and microelements present in both these plants were also extracted and analyzed. The higher heating values (HHVs) of the carbon products obtained ranged from 14.28 to 17.25 MJ/kg. The ash content ranged from 22.69% to 49.57%. The maximum yield obtained for biochar for Egeria densa at 200 °C was 66.89%. Temperature significantly affects solid hydrochar yield. The HHVs of the pellets obtained ranged from 11.38 to 13.49 MJ/kg. The use of these species to obtain biofuels through hydrothermal carbonization (HTC) and pellets is a novel and effective approach that will facilitate the removal of nutrients that cause eutrophication in the Umia River. The elements extracted show that harvesting these plants will help to remove excessive nutrients from the ecosystem. Full article

Due to global warming, a reduction in available water will occur in many watersheds and conflicts concerning water use will take place. This situation is already typical in semi-arid areas, where many reservoirs have been constructed for water storage. Increased energy demands and climate change have led to severe and increasing pressure on aquatic systems. Today, the environmental policies of many countries, such as Brazil, give priority to constructing new reservoirs for hydropower use, and an adopted reservoir and river basin management plan must minimize environmental impacts. Moreover, the production of energy plants will promote more requirements for new dam projects. The Itaparica reservoir is 30 years old, located in the São Francisco river in Northeast Brazil, and is the focus of an environmental study. The article focus of investigations is on the environmental and social impacts after the construction of Itaparica reservoir, governance difficulties, and adopted actions to minimize those impacts. Significant environmental impacts are recognizable, such as increased sedimentation in the inflow area, damage to the lakeshore zone by operational water level variation, water losses by evaporation and infiltration, and degradation of inundated vegetation. Furthermore, a trophic upsurge has been registered with severe eutrophication processes, such as the occurrence of cyanobacteria, oxygen deficit in the hypolimnion, and mass development of macrophytes (Egeria densa). With the creation of the dam there was compulsory displacement of the population of the municipalities around Itaparica reservoir with consequent difficulties of adaptation in the new spaces. Furthermore, there was de-structuring of social relation networks, loss of arable land and improvements, and small and insufficient indemnities for land. In this context, concepts for an advanced reservoir management under consideration of water scarcity are presented and discussed. This study aims to contribute to sustainable reservoir management Full article

Nitrogen loading from agricultural landscapes can trigger a cascade of detrimental effects on aquatic ecosystems. Recently, the spread of aquatic weed infestations (Eichhornia crassipes, Egeria densa, Ludwigia spp., and Onagraceae) in the Sacramento-San Joaquin Delta of northern California has raised concerns, and nitrogen loading from California’s intensive farming regions is considered as one of the major contributors. In this study, we employed the Soil and Water Assessment Tool (SWAT) to simulate nitrogen exports from the agriculturally intensive San Joaquin River watershed to the Delta. The alternate tile drainage routine in SWAT was tested against monitoring data in the tile-drained area of the watershed to examine the suitability of the new routine for a tile nitrate simulation. We found that the physically based Hooghoudt and Kirkham tile drain routine improved model performance in representing tile nitrate runoff, which contributed to 40% of the nitrate loading to the San Joaquin River. Calibration results show that the simulated riverine nitrate loads matched the observed data fairly well. According to model simulation, the San Joaquin River plays a critical role in exporting nitrogen to the Delta by exporting 3135 tons of nitrate-nitrogen annually, which has a strong ecological implication in supporting the growth of aquatic weeds, which has impeded water flow, impairs commercial navigation and recreational activities, and degrades water quality in Bay-Delta waterways. Since nitrate loadings contributed by upstream runoff are an important nutrient to facilitate weed development, our study results should be seen as a prerequisite to evaluate the potential growth impact of aquatic weeds and scientific evidence for area-wide weed control decisions. Full article

Three densities of the sex-reversed male Nile tilapia, Oreochromis niloticus (20, 25, 50 fish/m³) were cultivated in an integrated multi-trophic recirculating aquaculture system (IMRAS) that involves the ecological relationship between several living organisms, i.e., phytoplankton, zooplankton, and aquatic plants. The results indicated that, by providing proper interdependency between various species of living organisms, the concentrations of ammonia, nitrite, nitrate, and phosphate in the system were maintained below dangerous levels for Nile tilapia throughout the cultivation period. The highest wet weight productivity of Nile tilapia of 11 ± 1 kg was achieved at a fish density of 50 fish/m³. The aquatic plants in the treatment tank could effectively uptake the unwanted nitrogen (N) and phosphorus (P) compounds with the highest removal efficiencies of 9.52% and 11.4%, respectively. The uptake rates of nitrogen and phosphorus by aquatic plants could be ranked from high to low as: Egeria densa > Ceratophyllum demersum > Vallisneria spiralis and Vallisneria americana > Hygrophila difformis. The remaining N was further degraded through nitrification process, whereas the remaining P could well precipitate in the soil sediment in the treatment tank. Full article