Eutrophication of Aquatic Ecosystems： A Viewpoint on the Environmental Impact of Climate Change

Environmental concerns associated with nutrient-oriented eutrophication phenomenon have become a serious issue and a major cause of water quality deficiency nowadays. This necessitated eutrophication to occupy a front seat in research accompanied with climate change. Climate change has revealed to be a key player and a main contributor in the occurrence of such phenomenon. This paper discusses the ever-growing concern about eutrophication as a cause of climate change. Climate change affects storms intensity, changing the precipitation regime and increasing temperature. These effects increase the nutrient loading diffusion and cause excessive nutrients accompanied with storm water runoff, domestic wastewaters, and agricultural discharges to pour into water bodies. Eutrophication conversely contributes in the global wanning by releasing greenhouse gases from deoxygenated waters and sediments. Some control and mitigation measures are needed to fight climate change and achieve desired water quality goals. These measures include mitigation of climate change causes, enhancement of natural ecohydrological processes, application of proper integrated water resource management and participation of communities and governments.

Effects of Aquatic Plants on the Feature of Sediment Resuspension in Lake Taihu

[Objective] The aim was to study effects of aquatic plants on resuspen- sion of sediment in Lake Taihu. [Method] New resuspension simulator was used in the research. Elodea nuttalli, submerged plant, and Phragmites australis, emergent aquatic plant, were grown in substrate sludge with varied planting density set. Study of simulation experiment on the feature of sediment resuspension was carried on under shearing stress of 0.2-0.5 N/m2 and agitation of 1-30 min. [Result] Aquatic plant growing would effectively reduce seston concentration in water. Concentrations of final Suspended Particulate Matter （SPM） in experimental groups and control groups were as follows： water without plant〉coverage of 30% of Elodea nuttalli〉cov- erage of 60% of Elodea nuttalli〉Phragmites australis with concentration of 50 stock/m2〉 coverage of 90% of Elodea nuttalli〉Phragmites australis with concentration of 80 stock/m2〉Phragmites australis with concentration of 150 stock/m2; SPM concentration showed a tendency from increasing to stable with change of stirring time under dif- ferent shearing stresses： SPM concentration was of severe change at early stage in barrel without aquatic plant while change of SPM concentration in barrel with aquatic plant was quite mild and grew smaller with concentration increasing; SPM concentration was reduced much more if Phragmites australis planted compared with that of Elodea nuttalli; under different shearing stresses, reduction of SPM concen- tration by increase of Phragmites australis area was much more than by increase of Elodea nuttalli area. [Conclusion] It would provide powerful scientific reference for control on aquatic environment through comprehensive research on the feature of sediment resuspension.

Mechanism of microcystin removal from eutrophicated source water by aquatic vegetable bed

For purifying raw water for tap water treatment, the aquatic vegetable bed （AVB） experiment has been carded out in a hypertrophic waterfront of Taihu Lake, China. The average removal rates of total microcystin-RR and microcystin-LR are 63.0% and 66. 7%, respectively. Experiments indicate that lpomoea aquatica can absorb microcystin by using enzyme-linked immunosorbent assay （ELISA）, and the roots absorb more toxins than leaves and stems. Fluorescence in situ hybridization （FISH） is used to analyze the density of microcystin degrading bacteria in the AVB sediment. Two species of microcystin degrading bacteria are detected, which indicate that microcystin bio-degradation process happened in the AVB. Protozoa and metazoa are abundant in root spheres. Aspidisca sp., Vorticella sp., Philodina sp., and Lecane sp. are dominant species. The predation functions of protozoa and metazoa have a positive effect on the removal of cyanobacteria and microcystin.

Water Quality Purifying Effect of Five Kinds of Aquatic Plants in Winter

[Objective] The aim was to compare the water quality purifying effect of five kinds of aquatic plants.[Method] Model of surface flow wetlands was constructed in the river bank of Jialu River in Zhengzhou City,and five kinds of aquatic plants which could grow normally in winter were selected and introduced for screening experiment of aquatic plants.[Result] Five kinds of plants were growing well,and they showed strong cold resistance.However,there were some differences on water quality purifying ability among five kinds of aquatic plants,in which Oenanthe javanica and Elodea canadensis performed better on removing the TN,the removal rate was 44% and 41% respectively; Iris sibirica and O.javanica showed better performance on the removal of TP,the removal rate was 41% and 37% respectively; there was little difference on the removal effect on NH4^＋-N among five kinds of plants,in which E.Canadensis performed best with the removal rate of 73%,followed by O.javanica （the removal rate was 71%）,and the removal rate of I.sibirica,Rumex acetosa and Potamogeton crispus were 70%; there was no significant purification effect of five kinds of plants on CODCr,in which I.sibirica and R.acetosa performed better,and the removal rate was 14% and 13% respectively.[Conclusion] The emerging plants and submerged plants hydrophytes could be used to construct floating aquatic macrophyte-based treatment system （FAMS） in wetland vegetation allocation to improve the purification effect of wetlands of North China in winter.

Periphyton Biomass Response to Phosphorus Additions in an Aquatic Ecosystem Dominated by Submersed Plants

An experiment was conducted to investigate the response of periphyton biomass to addition of phosphorus (P) in an aquatic ecosystem dominated by submersed plants. Aquatic ecosystems dominated by Hydrilla verticillata (L.f.) Royle and Vallisneria natans (Lour.) Hara were constructed in mesocosm aquaria. Mesocosms were dosed weekly with different P loads (0 μg/L/Week and 100 μg/L/Week) for 17 weeks. Total P (TP), total soluble P (TSP), and soluble reactive P (SRP) concentrations in the waters of mesocosms added with P were significantly higher as opposed to the unenriched control mesocosms. The biomass of the attached periphyton and the cover of floating periphyton remained abundant in P-unenriched control mesocosms throughout the test period with a TP, TSP, and SRP concentration ranging of 0.021 - 0.049 mg/L, 0.004 - 0.024 mg/L, and 0.003 - 0.018 mg/L, respectively. P addition caused the decline of attached periphyton biomass to a low level and loss of floating periphyton. Results indicate that P enrichment in an aquatic ecosystem dominated by submersed plants could reduce attached periphyton biomass and eliminate floating periphyton. The research would be useful to maintain periphyton by reducing excessive P in aquatic ecosystem dominated by submersed plants.

Evaluation of Potential Extracts Antioxydant (Aqueous, Hydro-Ethanolic and Ethanolic) of an Aquatic Plant from the River Djoue (<i>Ledermanniella schlechteri</i>)

The aim for this present study was to evaluate the antioxidant potential of aqueous extracts (AE), hydro-ethanolic extracts (HE) and ethanolic extracts (EE) obtained from an aquatic plant (L. schlechteri) using a simple and fast method that is the CCM. This method revealed the presence of phenolics and flavonoids at different levels but with higher antioxidant activity in EE compared to AE. Among the two families of antioxidants evaluated, the phenolic compounds were found to be higher on the EE (5.85 mgEAG/MS) followed by the HE (5.06 mgEAG/MS) and less and less important on the AE (3.661 mgEAG/MS). While the less significantly elevated flavonoids showed values of 1.146 mgECa/MS for EE, 0.406 mgECa/MS for HE et 0.181 mgECa/MS for AE. However, the anti-free radical activity was also evaluated. Unlike the antioxidant activity, the ant-free radical activity with a greater IC50 was observed on AE with a rate of 66.66 mg/mL, then less on the hydro-ethanolic and ethanolic extracts, respectively at levels of 26.15 mg/mL et 19.18 mg/mL.

Periphyton response to nitrogen and phosphorus enrichment in a eutrophic shallow aquatic ecosystem

We examined changes in biomass and species dominance of periphyton in response to nitrogen (N) and phosphorus (P) enrichment in 12 mesocosms representing eutrophic aquatic ecosystems. The 100-L mesocosms consisted of lake water and pond sediment, and N and P were applied weekly. Periphyton samples were taken to assess the biomass (as estimated by the concentration of chlorophyll a (chl a)) and to determine which species were dominant. The mean periphyton biomass (chl a) in the P-enriched treatment did not differ from that in the control group, but increased with N enrichment. Compared with that in the control group, the chl a concentration increased with N+P enrichment in the early stages of the experiment, but decreased in the later stages. The decline in periphyton biomass at the later stages of the experiment was due to limited light availability, which resulted from the increased phytoplankton density in the experiment. The nutrient enrichment treatments resulted in changes in the dominant algal species in the periphyton, suggesting that various algal species showed different responses to different nutrients. The results of this study have implications for nutrient management in aquatic ecosystems.

Impact of Land Use and Aquatic Plants on the Water Quality of the Sub-Tropical Alpine Wetlands in India: A Case Study Using Neuro-Genetic Models

The suspended and dissolved waste in the incoming storm water of wetlands largely depends on the adjacent land use which can influence the quality of the water body. The micro- and macro-floral population of a wetland can absorb, convert, transform and release different organic or inorganic elements, which can also change or impact the overall quality of the wetland water. The present study investigates the influence of the land use and the plant species in the waterbed on the water quality of a high-altitude, sub-tropical wetland in India. The estimation capabilities of neuro-genetic models were utilized to identify the inherent relationships between the Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), chlorine (Cl) and Chemical Oxygen Demand (COD) with the land use and wetland zoology. A thematic map of the quality parameters was also generated based on the identified relationship to observe the influence that the morphological and biological diversity in and around the study area has on the quality parameters of the wetland. According to the results, the BOD, COD and Cl were found to vary with differences in land use and the presence of different plant species, whereas the DO was found to be largely invariant with changes in these parameters. The reasons may be contributed to the impact of uncontrolled eco-tourism activities around the wetland.

Native Aquatic Plant Establishment Efforts in a High-Herbivore, Central Texas Reservoir

Maintaining beneficial, native plant structure and diversity while reducing invasive, nuisance species dominance is an important management domain for natural resource managers. One such vegetation component in North American lakes and reservoirs is submerged aquatic vegetation—a valuable aquatic resource which serves as productive habitat for fish, aquatic macroinvertebrates, and other wildlife. Reservoirs in the southern parts of the United States have experienced varying aquatic plant dominance dynamics due to historical water resource management actions, including drawdowns and introduction of herbivorous fish for the purpose of controlling invasive aquatic vegetation. Some of these management options have also been detrimental to native submerged aquatic vegetation. This paper explores an adaptive management research effort by installing herbivore-protected, fenced-pen submerged aquatic vegetation sites in a high-herbivore reservoir to determine effectiveness of protecting habitat and serving as founder colony sources for propagule spread. Four experimental sites with three management treatments each were planted with American eelgrass. Each site utilized one un-fenced treatment and two treatments with varying mesh sizes for protective fencing-pens. Site integrity, species survival and spread, and grazing were documented. One additional site was installed and planted with other native submerged aquatic vegetation species for nominal species performance descriptions. No plants survived unprotected in the high-herbivore system and plants, in general, performed consistently better within the smaller mesh size. These test planting results were ultimately used to inform adaptive management decision making for plant installation and expansion designs for managing reservoirs invested with Hydrilla, considered one of the most serious invasive aquatic plants in the United States.

Water Purification Capacity of Four Kinds of Aquatic Plants in the Upper Reaches of Luanhe River

Under artificially simulated conditions, the water purification effects of Lythrum salicaria, Typha minima, Scirpus validus, Iris wilsonii and their configurations were studied. The results showed that various aquatic plants and their configurations showed purification effects for total nitrogen(TN), nitrate nitrogen(NO_3^-), total phosphorus(TP), orthophosphate(PO_4^(3-)) and chemical oxygen demand(COD) in water body, and the purification effects of aquatic plant configurations were better than those of single ones. Regression analysis was conducted for dynamics of various water quality indicators. The removal rates of TN and COD within 50 d by the combination of L. salicaria and I. wilsonii were 73.83% and 77.4%, respectively, with the best purification effect; the removal rate of NO_3^- within 20 d by the combination of S. validus and I. wilsonii was 89.41%; and the combination of S. validus and I. wilsonii showed the best removal effect for TP and PO43-, of which the 50-d removal rates were 88.98% and 92.39%, respectively. Reasonable choice of local aquatic plants and their optimal combinations can be applied in the improvement of water quality of rivers.

Effects of Eichhornia crassipes Growth on Aquatic Plants in Dianchi Lake

[Objective] The aim was to study the effects of Eichhornia crassipes as an invasive plant on aquatic plants in Dianchi Lake. [Method] Based on the determination of chlorophyll content of phytoplankton and submerged plant (Potamogeton pectinatus) in Dianchi Lake in different months, the effects of E. crassipes on aquatic plants in Dianchi Lake were studied, and the allelopathy effect of root culture solution of E. crassipes on Microcystis aquaticum was discussed. [Result] The growth of E. crassipes in Dianchi Lake reduced the chlorophyll content of phytoplankton and submerged plant (P. pectinatus), and it showed that E. crassipes had certain inhibitory effect on their growth; the culture solution of E. crassipes root inhibited M. aeruginosa growth obviously. [Conclusion] The study could provide scientific references for the prevention and control of ecological safety of E. crassipes.

Convergent relationships between flower economics and hydraulic traits across aquatic and terrestrial herbaceous plants

Maintaining open flowers is critical for successful pollination and depends on long-term water and carbon balance.Yet the relationship between how flower hydraulic traits are coordinated in different habitats is poorly understood.Here,we hypothesize that the coordination and trade-offs between floral hydraulics and economics traits are independent of environmental conditions.To test this hypothesis,we investigated a total of 27 flower economics and hydraulic traits in six aquatic and six terrestrial herbaceous species grown in a tropical botanical garden.We found that although there were a few significant differences,most flower hydraulics and economics traits did not differ significantly between aquatic and terrestrial herbaceous plants.Both flower mass per area and floral longevity were significantly positively correlated with the time required for drying full-hydrated flowers to 70%relative water content.Flower dry matter content was strongly and positively related to drought tolerance of the flowers as indicated by flower water potential at the turgor loss point.In addition,there was a trade-off between hydraulic efficiency and the construction cost of a flower across species.Our results show that flowers of aquatic and terrestrial plants follow the same economics spectrum pattern.These results suggest a convergent flower economics design across terrestrial and aquatic plants,providing new insights into the mechanisms by which floral organs adapt to aquatic and terrestrial habitats.

The Ability of Some Aquatic and Terrestrial Plants to Purify Domestic Wastewater

The study aimed to evaluate the ability of some terrestrial and aquatic plants for wastewater purification.Aquatic plants can remove pollutants from wastewater by consuming and accumulating various contaminants in different parts of plants.Different aquatic and terrestrial plants(Rosa sinensis,Typha latifolia,Ocimm bacilicum,Azolla pinnata,and Salvinia molesta)which have the ability to decrease water pollution were utilized in this study.The capability offive different species of plants was investigated by measuring chemical oxygen demand(COD),biological oxygen demand(BOD),electrical conductivity(EC),total dissolved solids(TDS),and pH of the medium.In this research,some aquatic and terrestrial plants were transplanted in wastewater plastic pots containing domestic wastewater with different ratios of 50%and 100%.Then,after 30 days,the physiological and biochemical parameters of plants were calculated to observe the effect of wastewater on plants.Results revealed higher chlorophyll and carotenoids in typha plants treated with 100%wastewater.The highest percentage of elimination in BOD(65%),COD(27%),TDS(72%),EC(83%),and pH(6.8%)was noted with the use of typha and azolla.Intriguingly,total soluble sugars,total free amino acids,and total proteins were found maximum in the hibiscus plant as compared to the other plants under 100%and 50%domestic wastewater treatment,while typha and ocimum showed lower values of these parameters irrespective of wastewater treatments.Moreover,the COD,BOD,TDS,EC,and pH trend was higher in 100%wastewater as compared to 50%wastewater.Taking into account the accumulation capacity of the tested plants especially typha can be efficiently used for the treatment of domestic wastewater.

Investigation and Configuration Analysis of Aquatic Plants in Chengdu Wetland Parks

To find out the current situation and configuration of aquatic plants in landscape water of Chengdu wetland parks,sample-plot survey of aquatic plants in landscape water in the built wetland parks of Chengdu and urban parks was conducted.The results showed that there are 41 kinds of aquatic plants in the research region,belonging to 23 families.They are mainly hygrophyte and emergent plants,while floating and submerged plants are rarely used.Configuration of aquatic plants is mainly composed of emergent plants,supplemented by floating-leaved and submerged plants,and water landscape is rich.Then,configuration of aquatic plants in wetland parks was analyzed from the ecological function,landscape construction and other aspects,to provide the reference for plant configuration of urban wetland parks.

The Experiment Study of the Influence on Plant Seeds and Aquatic Biological Survival in High Altitude Environment

There is A certain foundation in this experiment. It was the second time we did this experiment. The purposes are three parts, first, explore the 30000~40000 meters high sky with two cameras recording the scene. The Second, find out whether the high sky condition(temperature, air pressure, cosmic ray) make influence on plants seeds. The third, text whether normal aquatic animal is able to survive in high sky. The conclusions are also three parts. It is important to set a deadline for my group member to finish the assignment, and also check their process, or they might delay their own part of work or they are not in charge of the work. As the leader, I should be thoughtful. Not only about members’ assignment, but also the details of their work, previously. Discuss about each task with group to ensure the correctness. Last but not least, every part of the experiment needs to be tested carefully. Only if we try our best to prevent accidents that might happen, then the experiment is able to success.

Study on the Changes of Physiological Indexes of Water Spinach in Eutrophication Water

[Objective] Effect of hypoxic water culture on physiological characteristic of water spinach and its hypoxia tolerance were studied.[Method] Water spinach was planted in soil and eutrophication water by means of floating bed,respectively,and the change of physiological indexes including chlorophyll,proline（Pro）,malondialdehyde（MDA）,soluble sugar and soluble protein in water spinach leaves at mature stage was researched,while the hypoxia tolerance of water spinach and the effect of plant density on water spinach growth were discussed in our paper.[Result] In the hypoxic eutrophication water,the content of total chlorophyll,malondialdehyde,soluble sugar and soluble protein in water spinach leaves was lower than that of soil culture,with higher proline content,which showed that water spinach had better tolerance to hypoxic eutrophication water;the higher the plant density,the lower the chlorophyll content in water spinach leaves,and there was no significant effect of plant density on proline and malondialdehyde content,while soluble protein content was higher under high plant density.[Conclusion] The best plant density of water spinach was 66 plants per floating bed with the area of 2 m2,which could provide theoretical basis for the application of water spinach in floating bed.

Experimental Research on the Application of Water Hyacinths to the Ecological Restoration of Water Bodies with Eutrophication

[Objective] The study aims to discuss the application of water hyacinths to the ecological restoration of water bodies with eutrophication through simulation experiments. [Method] In this study, water hyacinths were used to restore the simulated eutrophic water with green algae as the dominant algae species, and then the restoration effect of the simulated eutrophic water by water hyacinths was analyzed. [Result] In the simulation test without sediment, the peak chlorophyll concentration was 434.6 mg/m3 in the tank without water hyacinths, which decreased to 285 and 119 mg/m3 respectively in the tanks with 1 and 4 water hyacinths. In the experiment with sediment, compared with the control tank without water hyacinths, a 58% reduction in chlorophyll concentration could be observed in the tank with 4 water hyacinths planted (with a coverage of 51%). The results showed that water hyacinths could inhibit alga growth notably, but there was likely a density threshold (51% coverage), and no significant eco-restoration effect was observed in the simulated eutrophic water with too few water hyacinths planted. [Conclusion] The research could provide scientific references for the ecological restoration of eutrophic water bodies.

Migration of silver nanoparticles in an aquatic system with Eichhornia crassipes

The migration and dissolution of AgNPs in an aquatic system with plants was investigated.By using a hydroponic system with Eichhornia crassipes,the absorption and transportation processes of silver nanoparticles were investigated.The results show that AgNPs concentrations in the water phase declined with the increase in time,and the reduction degree was dependent on the initial concentrations of AgNPs.The silver concentrations in the roots(r=0.98,p<0.05),stems and leaves(r=1,p<0.001)were significantly positively correlated with the initial concentrations of AgNPs.Silver nanoparticles accumulated in plant roots more than stems and leaves.Compared with the addition of AgNO 3 at identical concentrations,lower removal rates of silver and plant uptake were observed in the AgNPs stress systems.A significant positive correlation was also found between the initial AgNPs concentrations and the removed amount of silver(r=0.99,p<0.001).For AgNPs,the primary removal mechanisms in these aquatic systems were agglomeration and sedimentation,while the absorption by plants had a relatively weak contribution.

Analysis of Plant Diversity Characteristics in Jiangxia Wetland

[Objectives]This study was conducted to explore the characteristics of plant diversity of Jiangxia Wetland in Lhasa River basin.[Methods]Based on the survey data of 37 plant community in three types of sample plots of Jiangxia Wetland in the Lhasa River basin,this study analyzed the diversity of plant community in different habitats of Jiangxia Wetland from Pielou evenness,Margalef richness,Simpson and Shannon Wiener diversity indexes of different types and levels.[Results]The Pielou index,Shannon-Wiener index and Simpson diversity index of dry land was higher than those of other plots,while the Margalef species richness index of the ecotone of seasonally flooded and dry land was higher than that of other plots.The Pielou index,Shannon-Wiener index,Simpson diversity index and Margalef species richness index of composite plants were higher than those of other herbaceous plants.The Shannon-Wiener index,Simpson diversity index and Margalef species richness index of hygrophytes were higher than those of other plants,while the Pielou index evenness index of aquatic plants was higher than that of other plants.Annual or perennial herbaceous plants occupied the primary position in the study area,and shrub plants occupied a secondary position,and floating plants took the lowest position.[Conclusions]The results of this study can provide theoretical support or reference basis for the scientific management of comprehensive wetland systems such as wetland ecosystem restoration and plant diversity protection in Jiangxia Wetland.

不同水生植物组合对污染水体净化能力比较

模拟水体富营养化条件下,随机选取本土植物东方藨草(Scirpus orientalis)、水葱(Scirpus Validus)、香蒲(Typha orientalis)、菰(Zizania latifolia)、菖蒲(Acorus calamus)、欧菱(Trapa natans)和荇菜(Nymphoides peltata)中2种挺水植物+1种浮叶植物组成的群落对水体中氮磷污染物的去除作用进行比较研究。研究结果表明,东方藨草+香蒲+荇菜对水体中总氮、铵态氮和硝态氮的去除效果最佳,且其茎叶部和根部的氮含量增加最高;而菖蒲+水葱+欧菱对水体中的总磷去除效果最佳,且其茎叶部的磷含量增加最高。因此,东方藨草+香蒲+荇菜、菖蒲+水葱+欧菱可作为污染水体净化的备选组合,为植物组合对水体污染修复提供科学依据。