The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Yoav Waisel - One of the best experts on this subject based on the ideXlab platform.
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Competitive relationships between two water plant species: Najas marina L. and Myriophyllum spicatum L.
Hydrobiologia, 2002Co-Authors: Moshe Agami, Yoav WaiselAbstract:The interrelationships between two submerged macrophytes, Najas marina and Myriophyllum spicatum, were investigated. Double-reciprocal analysis was used to distinguish between the possible types of negative relationships. Results have demonstrated that interspecific inhibition was more severe than the intraspecific one. The intensity of inhibition was negatively correlated with the density of the examined species. The mutual inhibitory effect and the pattern of the obtained results suggest that competitive relationships exist between Najas marina and Myriophyllum spicatum.
Sidinei Magela Thomaz - One of the best experts on this subject based on the ideXlab platform.
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the invasive submerged macrophyte hydrilla verticillata as a foraging habitat for small sized fish
Natureza & Conservacao, 2014Co-Authors: Natalia Carniatto, Rosemara Fugi, Sidinei Magela Thomaz, Eduardo Ribeiro CunhaAbstract:Several species of aquatic macrophytes have invaded ecosystems outside their ranges, producing a variety of impacts on native biota. In this study, we tested the role of the invasive macrophyte Hydrilla verticillata as a foraging habitat for small fish species. To achieve this goal, we assessed the feeding activity and diet composition of fish captured in patches of the invasive H. verticillata and of a similar native macrophyte (Egeria Najas). Feeding activity did not differ significantly between H. verticillata and E. Najas, indicating that foraging activity was not affected. However, differences in diet composition were significant in three out of five fish species and marginally significant in one species, suggesting that the invasive and native macrophytes provide different types of food resources for fish. Thus, although H. verticillata does not affect the foraging activity, it has the potential to affect the assemblages of small-sized fish through changes in the proportions of food resources.
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response of native egeria Najas planch and invasive hydrilla verticillata l f royle to altered hydroecological regime in a subtropical river
Aquatic Botany, 2010Co-Authors: Wilson Treger Zydowicz Sousa, Sidinei Magela Thomaz, Kevin MurphyAbstract:Abstract Egeria Najas Planch. is the dominant native submersed macrophyte of the Upper Parana River in Brazil, while Hydrilla verticillata (L.f.) Royle has recently invaded this area. From January 2006 to December 2007, comprising two annual flood cycles, we conducted monthly surveys at two river stations and two lakes connected to the river within this stretch of the Parana River, aiming to understand how the hydrological regime influences the distribution and abundance of these native and invasive Hydrocharitaceae species. Hydrilla did not develop in the lakes, possibly due to the elevated proportion of organic matter in the sediment (∼10% DW). However, the exotic species dominated the river sites apparently suppressing E. Najas . In the lakes E. Najas reached a maximum biomass of 628 ± 82 g DW m −2 but did not surpass 333 ± 83 g DW m −2 in the river, where H. verticillata peaked at 1415 ± 255 g DW m −2 . Macrophyte biomass development was greatest during low-water periods, with transparent water and high temperatures. Floods probably affected submersed macrophytes (especially in 2007, when an extreme flood caused by an El Nino Southern Oscillation (ENSO) event occurred) via sediment movement and plant scouring (uprooting) effects, coupled with reduced water transparency. Macrophyte recovery started soon after the (less intense) 2006 flood but was delayed in 2007. In the river recovery started five months after the major flood, but in the lakes no significant plant regeneration was found even nine months after the disturbance. E. Najas and H. verticillata started regeneration practically at the same time but H. verticillata had much higher rates of biomass increase.
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Limnological effects of Egeria Najas Planchon (Hydrocharitaceae) in the arms of Itaipu Reservoir (Brazil, Paraguay)
Limnology, 2009Co-Authors: Luis Mauricio Bini, Sidinei Magela Thomaz, Priscilla CarvalhoAbstract:The limnological effects resulting from the metabolism of Egeria Najas Planchon (Hydrocharitaceae) were evaluated in the arms of the Itaipu Reservoir (Brazil). Due to local population decline in biomass and coverage, decomposition was the main process that accounted for the observed limnological changes. Thus, total Kjeldahl nitrogen and total phosphorus in littoral regions were significantly higher during periods of E. Najas occurrence. After plant stands disappeared, concentrations decreased in all arms. The nutrient pump effect explains these results, and E. Najas stands probably act as sources of nutrients, especially nitrogen. However, low concentrations measured after aboveground biomass disappearance indicate that the internal loading effect is ephemeral and restricted to the littoral regions subjected to the action of naturally senescing populations. The underwater light regime was negatively affected by E. Najas occurrence. Overall, these results and the small areas colonized by E. Najas in the arms of the Itaipu Reservoir indicate that ecological problems (e.g., reduction of biodiversity) derived from E. Najas metabolism are unlikely.
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effects of phosphorus and nitrogen amendments on the growth of egeria Najas
Aquatic Botany, 2007Co-Authors: Sidinei Magela Thomaz, Sandra Andrea Pierini, Patricia A Chambers, Gabrielli PereiraAbstract:Abstract The effect of nutrient addition on the growth of E. Najas was evaluated in a dose response experiment using sand amended with phosphorus (P) and nitrogen (N), and in enrichment trials with N and P amendments to natural sediments. Plants, water and sediment came from lagoons of the Upper Parana River Floodplain and from Itaipu Reservoir (Brazil). Relative growth rates (RGRs) of E. Najas shoots, based on dry mass (DM), varied from 0.03 to 0.060 d−1 for both nutrients. Root:shoot biomass ratios were related to sediment exchangeable P (r = −0.419; P = 0.03) and N (r = −0.54; P = 0.006), however root RGR was not related to sediment nutrient concentrations. When natural sediments were amended with N and P, neither shoot nor root RGRs differed among treatments for substrata from either the reservoir or the floodplain lagoons (P > 0.05). Comparison of nutrient concentrations measured in natural sediments collected from several sites in both the Upper Parana River Floodplain (range 49–213 μg P g−1 DM; 36–373 μg N g−1 DM) and Itaipu Reservoir (range 43–402 μg P g−1 DM; 7.9–238 μg N g−1 DM) showed that sediment N and P from these systems usually exceeded minimum requirements necessary for E. Najas growth, as measured in the dose response experiment. Together, these results indicate that E. Najas, at least in early stages of development, responds to sediment nutrient amendments and relies upon bottom sediments to meet its N and P requirements and that for at least two Brazilian ecosystems, growth of this species is not limited by insufficient sediment N or P. Thus, reducing N and P in water is not enough to control E. Najas growth in short time periods in these ecosystems.
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prediction of egeria Najas and egeria densa occurrence in a large subtropical reservoir itaipu reservoir brazil paraguay
Aquatic Botany, 2005Co-Authors: Luis Mauricio Bini, Sidinei Magela ThomazAbstract:Abstract Incidence data of two native submerged aquatic macrophytes ( Egeria Najas Planch. and Egeria densa Planch.) were obtained in eight arms of a large (1350 km 2 ) subtropical reservoir (Itaipu Binacional Reservoir, Brazil-Paraguay). Environmental variables were measured simultaneously. Two large-scale surveys in the same localities identified by a global positioning system were carried out in April 1999 ( n = 235) and January 2001 ( n = 230). Logistic regressions were used to test the effect of environmental variables on the likelihood of E. Najas and E. densa presence or absence. The two species were found under different environmental conditions: conductivity, light attenuation coefficient ( k ) and fetch were, in this order, the most important environmental variables in predicting the probability of occurrence of E. Najas , whereas light attenuation coefficient was the main predictor of the probability of occurrence of E. densa . Thus, both species were negatively affected by the light attenuation coefficient. However, this effect was stronger in E. densa . The small area occupied by these species may be accounted for by the permanent high turbidity of Itaipu Reservoir. Additionally, the dominance of E. Najas over of E. densa can be explained by the probably higher light requirements of E. densa . In other reservoirs worldwide, with higher water transparency, the opposite is frequently true. Between 1999 and 2001, an episodic water-level drawdown (5 m) caused the disappearance of submerged vegetation. After water-level normalization, previous vegetation presence (in 1999) was an important predictor of the probability of occurrence of E. Najas in 2001.
Moshe Agami - One of the best experts on this subject based on the ideXlab platform.
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Competitive relationships between two water plant species: Najas marina L. and Myriophyllum spicatum L.
Hydrobiologia, 2002Co-Authors: Moshe Agami, Yoav WaiselAbstract:The interrelationships between two submerged macrophytes, Najas marina and Myriophyllum spicatum, were investigated. Double-reciprocal analysis was used to distinguish between the possible types of negative relationships. Results have demonstrated that interspecific inhibition was more severe than the intraspecific one. The intensity of inhibition was negatively correlated with the density of the examined species. The mutual inhibitory effect and the pattern of the obtained results suggest that competitive relationships exist between Najas marina and Myriophyllum spicatum.
Ping Ning - One of the best experts on this subject based on the ideXlab platform.
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fe iii modified egeria Najas driven biochar for highly improved reduction and adsorption performance of cr vi
Powder Technology, 2021Co-Authors: Xiangyu Wang, Ping NingAbstract:Abstract A novel Egeria Najas driven-biochar was activated by loading ferric chloride onto surface (FeCl3@EN-BC). The synthesized composite was evaluated for its physicochemical properties and Cr(VI) adsorption behavior and mechanism. The result of SEM showed that the modified biochar is less porous than raw Egeria Najas biochar, but loaded with γ-Fe2O3 and Fe3O4 crystals. In addition, the results of FTIR, XRD and XPS also confirmed that Fe was successfully loaded on the Egeria Najas biochar. Cr(VI) was efficiently removed by FeCl3@EN-BC within the pH range from 2.5–8.5. The thermodynamics parameters suggested that the adsorption processes of Cr(VI) were all spontaneous and endothermic. The overall removal mechanism was regarded as adsorption, surface complex formation, reduction and ion exchange reaction. Therefore, this modified biochar derived from Egeria Najas has a potential of practical application in the removal of Cr(VI) from wastewater.
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an efficient egeria Najas derived biochar supported nzvi composite for cr vi removal characterization and mechanism investigation based on visual minteq model
Environmental Research, 2020Co-Authors: Xiangyu Wang, Ping NingAbstract:Abstract Egeria Najas is a submerged aquatic plant, and the literatures on resourcification of submerged aquatic plant biochar remain limited. Until now, there has been no study on submerged aquatic plant biochar supported nZVI that is widely applied for removal of diversified contaminants in solution. In this study, an efficient approach to the preparation of Egeria Najas-derived biochar supported nZVI composite is first developed for Cr(VI) removal in wastewater. The adsorption behavior and mechanism of Cr(VI) removal on the as-prepared Egeria Najas-derived biochar/nZVI (EN@nZVI) composite were investigated. The results of FTIR and XPS indicate that the EN@nZVI surface had many functional groups such as R-COOH, R-OH, R-NH2 and R-C-O-C, etc, which could provide active sites during the adsorption process. The BET results showed that the EN@nZVI had large specific surface area and average pore, which were 142.49 m2/g and 9.85 nm, respectively. EN@nZVI demonstrated high reactivity for Cr(VI) removal. Compared with nZVI, Cr(VI) removal efficiency by EN@nZVI is 50% higher than that of nZVI within 0.5 h. Furthermore, the maximum adsorption capacity of Cr (VI) was 56.79 mg/g and the energy of activation (Ea) was 31.30 kJ/mol. The adsorption process was well described by the pseudo-second order model and Sips adsorption isotherm model. The reaction mechanism of Cr(VI) removal was a multi-step removal mechanism, involving adsorption, surface complex formation, reduction and ion exchange reaction.
Enikö Iványi - One of the best experts on this subject based on the ideXlab platform.
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Allelopathic activity of Ceratophyllum demersum L. and Najas marina ssp. intermedia (Wolfgang) Casper
Hydrobiologia, 2003Co-Authors: Elisabeth M. Gross, Daniela Erhard, Enikö IványiAbstract:We investigated the allelopathic activity of two submersed macrophytes with different growth forms and nutrient uptake modes, Ceratophyllum demersum and Najas marina ssp. intermedia. A bioassay-directed method development revealed optimal extraction solvents for allelochemicals from both macrophytes. For Najas, 50% methanol and for Ceratophyllum 50% acetone yielded the strongest inhibition in the agar-diffusion assay with various filamentous or chroococcal cyanobacteria as target species. Further fractionation by liquid–liquid extraction (LLE) and solid phase extraction (SPE) procedures showed that both aquatic plants appear to have more than one active fraction, one being hydrophilic and one moderately lipophilic. The water-soluble allelochemicals may inhibit phytoplankton whereas the lipophilic allelochemicals may act through direct cell–cell contact, e.g., against epiphytes. Both macrophytes also exuded allelopathically active compounds into the surrounding medium as shown by SPE of their incubation water.
