Mind the gap: the delayed recovery of a population of the biological control agent Megamelus scutellaris Berg. (Hemiptera: Delphacidae) on water hyacinth after winter.

Cold winter temperatures significantly affect the biological control effort against water hyacinth, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), in more temperate regions around the world. The population dynamics of the planthopper Megamelus scutellaris Berg. (Hemiptera: Delphacidae), a newly released biological control agent of water hyacinth, were recorded on the Kubusi River in the Eastern Cape Province (South Africa) over 15 months to determine the population recovery post-winter. Megamelus scutellaris incurred a severe population decline at the onset of winter when the water hyacinth plants became frost damaged. The combined effect of a population bottleneck and low minimum winter temperatures (6.12°C) below the agent's lower developmental threshold (11.46°C) caused a post-winter lag in agent density increase. Subsequently, the maximum agent population density was only reached at the end of the following summer growing season which allowed the water hyacinth population to recover in the absence of any significant biological control immediately post-winter. Supplementary releases of agents from mass-reared cultures at the beginning of the growing season (spring) is suggested as a potential method of reducing the lag-period in field populations in colder areas where natural population recovery of agents is slower.

Eichhornia crassipes (Mart.) Solms: Uses, Challenges, Threats, and Prospects.

Water hyacinths pose serious challenges to humanity and the environment. Considering the enormity of the menace associated with the growth and spread of the plant and the difficulty in achieving a single, generally acceptable control method, it is becoming increasingly imperative to explore the potentials of the plant. New water hyacinth-related articles are regularly being published. Recently published articles about the plant were accessed, and the information in these articles is presented in the context of the pros and cons of the plant. Some of the benefits that can be derived from the plant include biogas and biofuel production, medicinal functions, vermicomposting, compost production, and bioremediation. However, clogging of waterways, obstruction of water transportation, and fishing activities; breeding grounds for pests and diseases; and reduction of water quality, loss of biodiversity, and economic downturn in areas invaded by the plant are problems associated with it. The peculiarity in the invasiveness of each situation should determine whether or not the growth of the plant is a problem, especially if the opportunity to harness the potentials of the plant exists. There are three major methods for controlling the plants when control becomes inevitable: mechanical, chemical, and biological. To achieve the best control, integrating two or more control methods is advised.

Phytoremediation of Industrial Sewage Sludge with Eichhornia crassipes, Salvinia molesta and Pistia stratiotes in Batch Fed Free Water Flow Constructed Wetlands.

Phytoremediation of industrial sewage sludge with Eichhornia crassipes, Salvinia molesta and Pistia stratiotes in pilot scale batch fed free water flow constructed wetlands was done in order to assess the suitability of remediated sludge as fertilizer. S. molesta showed the greatest decreases of Zn (36.0%), Fe (26.6%), Cu (32.6%), Cr (58.6%) and Ni, (26.9%) while P. startiotes and E. crassipes, respectively, showed the greatest Cd (27.1%) and Pb (42.4%) decreases. Metals, nutrients (total N and P) and fecal coliform in remediated sludge complied with regulatory standards and P. startiotes showed the greatest electrical conductivity (EC) (65.6%) decrease. The phytotoxicity assay on Lactuca sativa and Brassica oleraceae exhibited more than 50% of germination index from the sludge remediated with S. molesta. The results demonstrate that phytoremediation with hyper accumulators followed by phytotoxicity assay could be used to support decisions for the appropriate use of land disposed industrial sewage sludge.

Trait convergence and niche differentiation of two exotic invasive free-floating plant species in China under shifted water nutrient stoichiometric regimes.

The effects of eutrophication on the growth and phenotypic performance of macrophytes have been widely studied. Experimental evidence suggests that an increase in the water nutrient level would promote the performance of several invasive free-floating macrophytes. However, few studies have focused on how a shift in water nutrient (nitrogen and phosphorus) stoichiometric regimes may influence the performance of invasive free-floating macrophytes. In the present study, two exotic invasive plant species, free-floating Eichhornia crassipes and Pistia stratiotes, were subjected to different water nutrient stoichiometric regimes, and their phenotypic performance was studied. We found that the two species converged in several resource use traits and diverged in lateral root length. This implied that their similarities in fitness-correlated traits and their underwater niche differentiation probably contribute to their stable coexistence in the field. Additionally, the eutrophic conditions in the different N:P regimes scarcely altered the performance of both species compared to their performance in the oligotrophic condition. Based on previous studies, we predicted that moderate eutrophication with slight overloading of nitrogen and phosphorus would not improve the performance of several invasive free-floating plants and thus would scarcely alter the invasive status of these species. However, moderate eutrophication may cause other problems, such as the growth of phytoplankton and algae and increased pollution in the water.

Ecotoxicological effects and accumulation of ciprofloxacin in Eichhornia crassipes under hydroponic conditions.

Antibiotic residues pose a threat to the health of aquatic organisms. The effects and accumulation of antibiotic ciprofloxacin (CIP) in a floating macrophyte (Eichhornia crassipes) under hydroponic conditions were investigated. It was found that E. crassipes exposure to CIP (< 1000 µg L-1) could maintain a stable photosynthesis efficiency. In response to CIP stress, catalase and peroxidase activities of leaves were 7.24-37.51 nmol min-1 g-1 and 98.46-173.16 U g-1, respectively. The presence of CIP did not inhibit the growth of the plant. After 14 days of exposure, tender leaves became white and withered, ascribed to the decline of chlorophyll content and chlorophyll fluorescence parameters. The CIP concentrations, absorbed by E. crassipes, were highest in the roots, followed by white aerial parts and green aerial parts at CIP concentrations of 100 and 1000 µg L-1. These findings demonstrated that E. crassipes could absorb and tolerate CIP in a limited time-scale and imply an alternative solution for phytoremediation in water bodies contaminated with antibiotics.

Effects and Removal of the Antibiotic Sulfadiazine by Eichhornia crassipes: Potential Use for Phytoremediation.

The antibiotic sulfadiazine (SDZ) is a challenging threat to the health of aquatic organisms, as it frequently occurs in aquatic ecosystems. Tolerance mechanisms and accumulation of SDZ in a floating macrophyte (Eichhornia crassipes) under hydroponic conditions were investigated in this study to provide more insight into the SDZ removal process. Results show that the presence of 1 mg L-1 SDZ decreased the quickest and ranged from 669.45 to 165.34 µg L-1 from days 5 to 25. Exposing E. crassipes to SDZ ( < 1 mg L-1) maintained stable leaf photosynthetic efficiency. The overall increase in superoxide dismutase and peroxidase activities with SDZ treatments indicated that leaves were resistant. SDZ was absorbed by E. crassipes, following the sequence of root > aerial parts under all treatments. These findings suggest that E. crassipes has the ability to phytoremediation SDZ contaminated water.

Assessment of pollutant removal processes and kinetic modelling in vertical flow constructed wetlands at elevated pollutant loading.

Constructed wetland (CW), an ecological wastewater treatment technology, is low cost and easily to operate. Vertical flow constructed wetland (VF-CW) systems have been used to treat various wastewaters across the world. The present work exhibits the detail study of five type's multi-layered vertically constructed wetlands operated at 24 h hydraulic retention time under semi-continuous vertical flow mode. Except N-NO3-, all the pollutants were sufficient removal in iron scraps constructed wetland (ISs-CW). The highest average pollutant removal efficiency achieved in ISs-CW was 85.04%, 77.57%, 85.99%, 62.01% and 88.91% for N-NH4+, N-NO2+, total nitrogen, total phosphate and sulphate respectively. The present CWs planted with Eichhornia crassipes is a promising system for municipal wastewater treatment. The first-order kinetic modelling was best suited for the removal rate since it presents higher R2, rate constant (k) and B values.

Phosphorus removal from the hyper-eutrophic Lake Caohai (China) with large-scale water hyacinth cultivation.

A phytoremediation project involving the large-scale cultivation of water hyacinths (Eichhornia crassipes (Mart.) Solms) was conducted in Lake Caohai (China) from May to November during 2011-2013 to remove pollutants and decrease eutrophication. Water hyacinths were cultivated in two areas of Lake Caohai, Neicaohai, and Waicaohai, which are connected and function as a relatively independent water body. The areas for macrophyte growth varied in size from 4.30 km2 in 2011 to 0.85 km2 (2012) and 1.15 km2 (2013). Compared with historical data from 2007, the concentrations of total phosphorus decreased significantly, while dissolved oxygen concentrations increased slightly. After plant cultivation in 2011, the average concentrations of total phosphorus, total dissolved phosphorus, and phosphate anions decreased from 0.54, 0.35, and 0.23 mg L-1 upstream (river estuaries) to 0.15, 0.13, and 0.08 mg L-1 downstream (Xiyuan Channel), respectively. The amount of phosphorus assimilated by the macrophytes (44.31 t) was more than 100% of the total removed phosphorus (40.93 t) from lake water when water hyacinths covered 40.9% of the area, which could indicate sedimentary phosphorus release. Our study showed the great potential of utilizing water hyacinth phytoremediation to remove phosphorus in eutrophic waters.

Contrasting impact of elevated atmospheric CO2 on nitrogen cycle in eutrophic water with or without Eichhornia crassipes (Mart.) Solms.

The elevation of atmospheric CO2 is an inevitable trend that would lead to significant impact on the interrelated carbon and nitrogen cycles through microbial activities in the aquatic ecosystem. Eutrophication has become a common trophic state of inland waters throughout the world, but how the elevated CO2 affects N cycles in such eutrophic water with algal bloom, and how vegetative restoration helps to mitigate N2O emission remains unknown. We conducted the experiments to investigate the effects of ambient and elevated atmospheric CO2 (a[CO2], e[CO2]; 400, 800 µmol﹒mol-1) with and without the floating aquatic plant, Eichhornia crassipes (Mart.) Solms, on N-transformation in eutrophic water using the 15N tracer method. The nitrification could be slightly inhibited by e[CO2], due mainly to the competition for dissolved inorganic carbon between algae and nitrifiers. The e[CO2] promoted denitrification and N2O emissions from eutrophic water without growth of plants, leading to aggravation of greenhouse effect and forming a vicious cycle. However, growth of the aquatic plant, Eichhornia crassipes, slightly promoted nitrification, but reduced N2O emissions from eutrophic water under e[CO2] conditions, thereby attenuating the negative effect of e[CO2] on N2O emissions. In the experiment, the N transformation was influenced by many factors such as pH, DO and algae density, except e[CO2] and plant presence. The pH could be regulated through diurnal photosynthesis and respiration of algae and mitigated the acidification of water caused by e[CO2], leading to an appropriate pH range for both nitrifying and denitrifying microbes. Algal respiration at night could consume DO and enhance abundance of denitrifying functional genes (nirK, nosZ) in water, which was also supposed to be a critical factor affecting denitrification and N2O emissions. This study clarifies how the greenhouse effect caused by e[CO2] mediates N biogeochemical cycle in the aquatic ecosystem, and how vegetative restoration mitigates greenhouse gas emission.

Kinetics of arsenic absorption by the species Eichhornia crassipes and Lemna valdiviana under optimized conditions.

This work aimed to study the kinetics of arsenic absorption by Eichhornia crassipes and Lemna valdiviana under pre-established conditions of pH phosphate and nitrate in the nutrient solution. Additional aims were to evaluate the conversion kinetics between As(III) and As(V), and the effect of arsenic concentrations on development of the species. The plants were cultivated in nutrient solutions containing different arsenic concentrations: 0, 0.56, 0.89 and 1.38 mg L-1 for the water-hyacinth, and 0, 0.13, 0.48, 0.99 and 1.4 mg L-1 for Lemna. Monitoring of arsenic removal by the plants was performed by sampling at intervals of 0, 4, 8, 16, 24, 48, 96, 144, 192 and 240 h for the water hyacinth, and 0, 4, 8, 16, 24, 48, 96, 144 and 168 h for Lemna. The samples were submitted to analysis of total arsenic, As(III), As(V) and phosphorus. The first-order kinetics was fit to the arsenic removal kinetics by the plants, and it was observed that the decay coefficient (k) decreased with the increase of its initial concentration in the nutrient solution. For the, absorption was observed after 96 h of culture, the time coinciding with the greatest As(V) concentrations. For Lemna, the metal was only absorbed by the plant after decay of the phosphate levels of the medium, which occurred at 48 h. Concentrations above 1 mg L-1 implied deleterious effects in both plant species and in the phytoremediation process, and the bioaccumulation factor decreased for concentration above this for both E. crassipes and L. valdiviana.

Industrial wastewater treatment in internal circulation bioreactor followed by wetlands containing emergent plants and algae.

Wastewater treatment based on ecological principles is a low cost and highly desirable solution for the developing countries like Pakistan. The present study evaluated the effectiveness of biological treatment systems including Internal Circulation (IC) anaerobic bioreactor and constructed wetlands (CWs) containing macrophytes and mixed algal cultures for industrial wastewater treatment. The IC bioreactor reduced COD (52%), turbidity (89%), EC (24%) of the industrial wastewater. However, the effluents of IC bioreactor did not comply with National Environmental Quality Standards (NEQS) of Pakistan. Post-treatment of IC bioreactor effluents was accomplished in CW containing macrophytes (Arundo donax and Eichhornia crassipes) and mixed algal culture. The CWs planted with macrophytes lowered the concentrations of COD (89%) and turbidity (99%). CWs with algal biomass were not effective in further polishing the effluent. Inhibition of algal biomass growth was observed due to physicochemical characteristics of wastewater. The integrated treatment system consisting of IC bioreactor and macrophytes was found more suitable option for industrial wastewater treatment.

Synergistic phytoremediation of wastewater by two aquatic plants (Typha angustifolia and Eichhornia crassipes) and potential as biomass fuel.

The ability of a mixture of Typha angustifolia and Eichhornia crassipes to remove organics, nutrients, and heavy metals from wastewater from a Thailand fresh market was studied. Changes in physicochemical properties of the wastewater including pH, temperature, chemical oxygen demand, dissolved oxygen, biochemical oxygen demand (BOD), total P, TOC, conductivity, total Kjeldahl nitrogen, NO3--N, NH3-N, and metal (Pb, Cd, and Zn) concentrations were monitored. In the aquatic plant (AP) treatment, 100% survival of both species was observed. Dry biomass production and growth rate of T. angustifolia were approximately 3.3× and 2.7× of those for E. crassipes, respectively. The extensive root system of the plants improved water quality as determined by a marked decrease in turbidity in the AP treatment after 7 days. BOD content served as a useful indicator of water quality; BOD declined by 91% over 21 days. Both T. angustifolia and E. crassipes accumulated similar quantities of metals in both roots and shoots. Accumulation of metals was as follows: Zn > Cd > Pb. A study of calorific value and biomass composition revealed that T. angustifolia and E. crassipes possessed similar carbon content (~ 35%), hydrogen content (~ 6%), and gross calorific value. E. crassipes contained up to 16.9% ash and 65.4% moisture. Both species are considered invasive in Thailand; however, they may nonetheless provide practical benefits: In addition to their combined abilities to treat wastewater, T. angustifolia holds potential as an alternative energy source due to its high biomass production.

Macrophytes as potential biomonitors in peri-urban wetlands of the Middle Parana River (Argentina).

The aims of this study were to measure the concentrations of nutrients and pollutants in peri-urban wetlands, to analyze the plant morphology of the most representative macrophyte species, and to determine their potential use as biomonitors. Four wetlands in the Middle Paraná River floodplain evidencing contamination or anthropogenic impact were studied. The studied species were Typha domingensis Pers., Eichhornia crassipes (Mart.) Solms., Alternanthera philoxeroides (Mart.) Griseb., and Pistia stratiotes L. Besides, the same plant species from an uncontaminated wetland considered as control were studied. A. philoxeroides showed the highest total phosphorus (TP) concentration in leaves throughout the study, while the other species showed a higher TP concentration in roots than in leaves. Since metal concentration in A. philoxeroides tissues was always higher than in sediment, further studies focused on its phytoremediation capacity should be carried out. T. domingensis exhibited the highest Zn concentrations in roots followed by Pb, and E. crassipes presented the highest values of Pb concentrations in roots. The aerial part height of the plants from peri-urban wetlands was significantly higher than that of the plants from the control, while the root length was significantly lower. The root length of P. stratiotes showed a negative correlation with soluble reactive phosphorus (SRP) concentration in water. All the root anatomical parameters of T. domingensis and E. crassipes showed a positive correlation with nitrate and ammonium concentrations in water. The studied macrophytes evidenced a high tolerance, enabling them to grow and survive in peri-urban wetlands that receive pollution from different sources. The use of aquatic and wetland plants as contaminant bioindicators and bioaccumulators in the Middle Paraná River floodplain is completely feasible.

On-site phytoremediation applicability assessment in Alur Ilmu, Universiti Kebangsaan Malaysia based on spatial and pollution removal analyses.

The present paper aims to assess the phytoremediation performance based on pollution removal efficiency of the highly polluted region of Alur Ilmu urban river for its applicability of on-site treatment. Thirteen stations along Alur Ilmu were selected to produce thematic maps through spatial distribution analysis based on six water quality parameters of Malaysia's Water Quality Index (WQI) for dry and raining seasons. The maps generated were used to identify the highly polluted region for phytoremediation applicability assessment. Four free-floating plants were tested in treating water samples from the highly polluted region under three different conditions, namely controlled, aerated and normal treatments. The selected free-floating plants were water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), rose water lettuce (Pistia sp.) and pennywort (Centella asiatica). The results showed that Alur Ilmu was more polluted during dry season compared to raining season based on the water quality analysis. During dry season, four parameters were marked as polluted along Alur Ilmu, namely dissolve oxygen (DO), 4.72 mg/L (class III); ammoniacal nitrogen (NH3-N), 0.85 mg/L (class IV); total suspended solid (TSS), 402 mg/L (class V) and biological oxygen demand (BOD), 3.89 mg/L (class III), whereas, two parameters were classed as polluted during raining season, namely total suspended solid (TSS), 571 mg/L (class V) and biological oxygen demand (BOD), 4.01 mg/L (class III). The thematic maps generated from spatial distribution analysis using Kriging gridding method showed that the highly polluted region was recorded at station AL 5. Hence, water samples were taken from this station for pollution removal analysis. All the free-floating plants were able to reduce TSS and COD in less than 14 days. However, water hyacinth showed the least detrimental effect from the phytoremediation process compared to other free-floating plants, thus made it a suitable free-floating plants to be used for on-site treatment.

Water hyacinth a potential source for value addition: An overview.

Water hyacinth a fresh water aquatic plant is considered as a noxious weed in many parts of the world since it grows very fast and depletes nutrients and oxygen from water bodies adversely affecting the growth of both plants and animals. Hence conversion of this problematic weed to value added chemicals and fuels helps in the self-sustainability especially for developing countries. The present review discusses the various value added products and fuels which can be produced from water hyacinth, the recent research and developmental activities on the bioconversion of water hyacinth for the production of fuels and value added products as well as its possibilities and challenges in commercialization.

Morphometry and retention time as forcing functions to establishment and maintenance of aquatic macrophytes in a tropical reservoir / Morfometria e tempo de residência como fatores determinantes no estabelecimento e manutenção de macrófitas aquáticas em um reservatório tropical

Abstract Macrophytes may constitute an important resource for several chemical, physical and biological processes within aquatic ecosystems. This study considers that in tropical reservoirs with low retention time and with low values of shoreline development (DL), the expansion and persistence of aquatic macrophytes are mainly reported to local conditions (e.g., hydrodynamic and wind exposure) rather than trophic status and depth of the euphotic zone. In this context, this study aimed at describing and comparing the incidence of aquatic macrophytes in a throughflowing, non-dendritic tropical reservoir. During February 2006 to November 2007, eight limnological surveys were performed quarterly within the Ourinhos Reservoir, and in the mouth areas of its tributaries. At the six sampling stations 30 variables were measured. The number of sites with plants varied between 21 and 38 and at the end of the 1st year the total richness was found. The sampling survey outcome the recognition of 18 species of aquatic macrophytes; Cyperaceae (2 genera and 1 species), Pontederiaceae (3 species) and Onarograceae (3 genera) were the families with higher diversity. Seven species (Typha domingensis Pers., Myriophyllum aquaticum (Vell.) Verdec, Salvinia auriculata Aubl., Eichhornia azurea (Sw.) Kunth, Eleocharis sp1, Eichhornia crassipes (Mart.) Solms, Oxycaryum cubense (Poepp. & Kunth) Lye) always were present and were more frequent in the sites. The occurrence of emergent species predominated (45.9%), followed by submersed rooted (24.5%), free floating (19.5%), floating rooted (9.7%) and free submersed (0.3%). Although limnological variables and the distribution of macrophytes have discriminated the same sampling points, the stepwise multiple linear regressions did not pointed out strong correspondences (or coherence) among the most constant and distributed macrophyte species and the selected limnological variables, as well the trophic statuses. Seeing the low relationship among limnological variables and macrophytes distribution, in the case of Ourinhos Reservoir, the results pointed out that the water turbulence, low DL and wind exposure are the main driving forces that determine its aquatic plant distribution, life forms and species composition.

Resumo As macrófitas podem constituir um recurso importante para vários processos físicos, químicos e biológicos dos ecossistemas aquáticos. Esse estudo considera que nos reservatórios tropicais com baixo tempo de retenção e com baixos valores do grau de desenvolvimento das margens (DL), a expansão e manutenção das macrófitas aquáticas são referidas principalmente às condições locais (e.g., hidrodinâmica e exposição ao vento), ao invés do estado trófico e da profundidade de zona eufótica. Nesse contexto, o presente estudo teve como objetivo descrever e comparar a incidência de macrófitas aquáticas em um reservatório tropical de fluxo rápido e não dendrítico. De fevereiro de 2006 a novembro de 2007, oito avaliações limnológicas foram realizadas trimestralmente no reservatório Ourinhos e nas regiões de desembocadura de seus afluentes. Nas seis estações de amostragem 30 variáveis foram determinadas. O número de locais com plantas variou entre 21 e 38 e no final do primeiro ano o número total de espécies foi encontrado. Foram relacionadas 18 espécies de macrófitas aquáticas; Cyperaceae (2 gêneros e espécies), Pontederiaceae (3 espécies) e Onarograceae (3 gêneros) foram as famílias com mais diversidade. Sete espécies (Typha domingensis Pers., Myriophyllum aquaticum (Vell.) Verdec, Salvinia auriculata Aubl., Eichhornia azurea (Sw.) Kunth, Eleocharis sp1, Eichhornia crassipes (Mart.) Solms, Oxycaryum cubense (Poepp. & Kunth) Lye) sempre estiveram presentes e foram as mais frequentes. As ocorrências de espécies emergentes predominaram (45,9%), seguidas das submersas enraizadas (24,5%), flutuantes livres (19,5%), flutuantes enraizadas (9,7%) e submersas livres (0,3%). Embora as variáveis limnológicas e as distribuições de macrófitas tenham discriminado os mesmo pontos de coleta, regressões lineares múltiplas stepwise não apontaram correspondências fortes (ou coerentes) entre as espécies de macrófitas mais constantes e distribuídas e as variáveis limnológicas, assim como os estados tróficos. No reservatório Ourinhos, a baixa relação entre as variáveis limnológicas e a distribuição das macrófitas aponta que a turbulência da água, o baixo valor de DL e a exposição ao vento sejam as principais forças que determinam a distribuição das plantas aquáticas, as suas formas de vida e a composição das espécies.

Sequestration of precious and pollutant metals in biomass of cultured water hyacinth (Eichhornia crassipes).

The aim of this study was to investigate the overall root/shoot allocation of metal contaminants, the amount of metal removal by absorption and adsorption within or on the external root surfaces, the dose-response of water hyacinth metal uptake, and phytotoxicity. This was examined in a single-metal tub trial, using arsenic (As), gold (Au), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), uranium (U), and zinc (Zn). Iron and Mn were also used in low-, medium-, and high-concentration treatments to test their dose effect on water hyacinth's metal uptake. Water hyacinth was generally tolerant to metallotoxicity, except for Cu and Hg. Over 80 % of the total amount of metals removed was accumulated in the roots, of which 30-52 % was adsorbed onto the root surfaces. Furthermore, 73-98 % of the total metal assimilation by water hyacinth was located in the roots. The bioconcentration factor (BCF) of Cu, Hg, Au, and Zn exceeded the recommended index of 1000, which is used in selection of phytoremediating plants, but those of U, As, and Mn did not. Nevertheless, the BCF for Mn increased with the increase of Mn concentration in water. This suggests that the use of BCF index alone, without the consideration of plant biomass and metal concentration in water, is inadequate to determine the potential of plants for phytoremediation accurately. Thus, this study confirms that water hyacinth holds potential for a broad spectrum of phytoremediation roles. However, knowing whether these metals are adsorbed on or assimilated within the plant tissues as well as knowing their allocation between roots and shoots will inform decisions how to re-treat biomass for metal recovery, or the mode of biomass reduction for safe disposal after phytoremediation.

Fenced cultivation of water hyacinth for cyanobacterial bloom control.

To achieve the goals of harmful cyanobacterial bloom control and nutrient removal, an eco-engineering project with water hyacinth planted in large-scale enclosures was conducted based on meteorological and hydrographical conditions in Lake Dianchi. Water quality, cyanobacteria distribution, and nutrient (TN, TP) bioaccumulation were investigated. Elevated concentrations of N and P and low Secchi depth (SD) were relevant to large amount of cyanobacteria trapped in regions with water hyacinth, where biomass of the dominant cyanobacteria Microcystis (4.95 × 10(10) cells L(-1)) was more than 30-fold compared with values of the control. A dramatic increase of TN and TP contents in the plants was found throughout the sampling period. Results from the present study confirmed the great potential to use water hyacinth for cyanobacterial bloom control and nutrient removal in algal lakes such as Lake Dianchi.

Morphometry and retention time as forcing functions to establishment and maintenance of aquatic macrophytes in a tropical reservoir.

Macrophytes may constitute an important resource for several chemical, physical and biological processes within aquatic ecosystems. This study considers that in tropical reservoirs with low retention time and with low values of shoreline development (DL), the expansion and persistence of aquatic macrophytes are mainly reported to local conditions (e.g., hydrodynamic and wind exposure) rather than trophic status and depth of the euphotic zone. In this context, this study aimed at describing and comparing the incidence of aquatic macrophytes in a throughflowing, non-dendritic tropical reservoir. During February 2006 to November 2007, eight limnological surveys were performed quarterly within the Ourinhos Reservoir, and in the mouth areas of its tributaries. At the six sampling stations 30 variables were measured. The number of sites with plants varied between 21 and 38 and at the end of the 1st year the total richness was found. The sampling survey outcome the recognition of 18 species of aquatic macrophytes; Cyperaceae (2 genera and 1 species), Pontederiaceae (3 species) and Onarograceae (3 genera) were the families with higher diversity. Seven species (Typha domingensis Pers., Myriophyllum aquaticum (Vell.) Verdec, Salvinia auriculata Aubl., Eichhornia azurea (Sw.) Kunth, Eleocharis sp1, Eichhornia crassipes (Mart.) Solms, Oxycaryum cubense (Poepp. & Kunth) Lye) always were present and were more frequent in the sites. The occurrence of emergent species predominated (45.9%), followed by submersed rooted (24.5%), free floating (19.5%), floating rooted (9.7%) and free submersed (0.3%). Although limnological variables and the distribution of macrophytes have discriminated the same sampling points, the stepwise multiple linear regressions did not pointed out strong correspondences (or coherence) among the most constant and distributed macrophyte species and the selected limnological variables, as well the trophic statuses. Seeing the low relationship among limnological variables and macrophytes distribution, in the case of Ourinhos Reservoir, the results pointed out that the water turbulence, low DL and wind exposure are the main driving forces that determine its aquatic plant distribution, life forms and species composition.

Effects of engineered application of Eichhornia crassipes on the benthic macroinvertebrate diversity in Lake Dianchi, an ultra-eutrophic lake in China.

An ecological engineering project with confined growth of 1.5 km(2) of Eichhornia crassipes was implemented to remove pollutants in Lake Dianchi. To assess the ecological effects of this project on benthic macroinvertebrate assemblages, a 1-year investigation at the areas inside and outside E. crassipes mats was conducted from May 2013 to May 2014. All the 10 sampling sites in the areas were grouped into two statistically significant clusters mainly corresponding to inside and outside E. crassipes mat areas (EMAs), by clustering analysis. E. crassipes reduced the densities of pollution indicator taxa (e.g., Oligochaeta and Chironomidae larvae); thus, the total densities of benthic macroinvertebrates at the area inside EMAs (mean 328.2 ind./m(2)) were slightly lower than that at the area outside EMAs (mean 505.6 ind./m(2)). Four functional feeding groups including 38 species of benthic macroinvertebrates were collected at the area inside EMAs, while only three functional feeding groups containing 17 species were collected at the area outside EMAs. The biodiversity indices (Shannon-Weiner, Margalef, Simpson, and Peilou indices) and K-dominance curves also showed higher diversity of benthic macroinvertebrates at the area inside EMAs than at the area outside EMAs. These results suggested that a certain scale of engineering application of E. crassipes was beneficial to benthic macroinvertebrate communities in the ultra-eutrophic Lake Dianchi and it could be used as a pioneer species in ultra-eutrophic lake for pollutant removal.