STUDIES ON ION BEAM APPLICATION TO IMPROVE AQUATIC MACROPHYTE REMEDIATION CAPACITY IN EUTROPHIC WATERS

Using ion beam biotechnology in combination with soil-less plant cultivation on artificial substratum (floating beds), the experiments were conducted with Ipomoea aquatica Forsk. Plants were attached to floating-beds which were placed on the surface of artificially nutrient-enriched tank water, in order to study the purification and remediation efficiency of ion beam-treated I. aquatica cultivars. The results show that N + ion beams with 25keV energy and dosages of 0, 2.6, 3.9, 5.2, 6.5, 7.8, 9.1×10 13N +(ions)/cm 2 affected I. aquatica dry seeds differently, with the dose of 3.9×10 13N + (ions)/cm 2 improving effectively the performance as expressed by various biological indices. After ion beam application, I. aquatica cultivars grew well in nutrient-enriched water bodies, increasing the growth of leaves and stem, number of leaves, length and area of roots, plant height, and weight more remarkably than observed in the control. The net removing rates of TN, TP were as high as 75% and 82%, respectively. Especially under the dose of 3.9×10 13N +(ions)/cm 2, the net removing rates of TN, TP were highest, for 77% and 85%, respectively. It was proved that ion beam application improves phytoremediation and may be used to purify nutrient rich water bodies.

Removal of Heavy Metals by Two Free Floating Aquatic Macrophytes

A concentration-dependent decrease in biomass, protein, RNA, DNA, and nutrient (NO3- and PO43-) uptake of Lemna minor and Azolla pinnata by Cr, Ni, and Zn was detected. Cr was found to exert maximum toxicity followed by Ni and Zn. Metal uptake was dependent on time and concentration of metal in the external rnedium. Both the macrophytes, however, showed preference for Zn followed by Ni and Cr. The uptake kinetics also revealed a low Vmax and high Km for Cr. L. minor was more effcient in accumulating Zn and Cr than A. pinnata in Ni. Compared to immobilized algae and bacterial capsules the test macrophytes showed a greater efficiency for metal removal

Contribution to the Study of Aquatic Macrophytes from Musura Bay （Danube Delta, Romania）

Danube Delta--a unique, young and continuing growing region, is a favorable place for developing a unique flora and fauna with many rare and protected species in Europe. Even though the terrestrial environment is present in the area, the predominance of the aquatic environment led to the existence of a particular macrophytic flora. At the contact point of the sea-water and freshwater, physical, chemical and biological processes occur. As a consequence, researchers consider these coastal waters special ecosystem, in which Musura bay is the most representative one. The purpose of this paper is to contribute to the study of aquatic submerged and floating macrophytes. The present study took place over two years （2013-2014）. In each year, a number of expeditions were made in different seasons in order to observe the diverse flora and flora associations. This due to seasonal variation in water quality, and might be a significantly seasonality of the vegetation also. The importance of the studies regarding flora of the Danube Delta, consist in the fact that the plants in this area are of social and economical importance, but also very important for environmental conservation.

Green Liver Systems for Water Purification:Using the Phytoremediation Potential of Aquatic Macrophytes for the Removal of Different Cyanobacterial Toxins from Water

The protection and reasonable use of freshwater is one of the main goals for our future, as water is most important for all organisms on earth including humans. Due to pollution, not only with xenobiotics, but also with nutrients, the status of our water bodies has changed drastically. Excess nutrient load induces eutrophication processes and, as a result, massive cyanobacterial blooms during the summer times. As cyanobacteria are known to produce several toxic secondary metabolites, the so-called cyanotoxins, exhibiting hepato-, neuro- and cell-toxicity, a potential risk is given, when using this water. There is an urgent need to have a water purification system, which is able to cope with these natural toxins. Using aquatic plants as a Green Liver, the Green Liver System?, was developed, able to remove these natural pollutants. To test the ability of the Green Liver System?, several cyanobacterial toxins including artificial and natural mixtures were tested in a small-scale laboratory system. The results showed that within 7 - 14 days a combination of different aquatic macrophytes was able to remove a given toxin amount (10 μg·L-1) by 100%. The phytoremediation technology behind the Green Liver Systems? uses the simple ability of submerged aquatic plants to uptake, detoxify and store the toxins, without formation and release of further metabolites to the surrounding water.

Enrichment and toxic effects of triclosan on aquatic macrophytes Eichhornia crassipes and Hydrilla verticillata exposed to triclosan in sediments

Background Clarifying the enrichment and response processes of triclosan(TCS)in hydrophytes is crucial for assessing the ecological risk of TCS in aquatic environments.This study delves into the chronic toxic effects of TCS in floating plant Eichhornia crassipes(Mart.)Solms and submerged plant Hydrilla verticillata(L.f.)Royle exposed to TCS sediments through hydroponic experiments.Results The absorption abilities of hydrophytes to TCS were species-dependent.The concentration of TCS in the roots of E.crassipes was significantly higher than that in its leaves,while the absorption capacities of the leaves of H.verticillata to TCS were stronger than that in its roots.Furthermore,the physiological indexes,including chlorophyll concentration,soluble protein concentration,and antioxidant enzyme activities,showed a significant decrease with the exposure concentration and time of TCS.Although the chlorophyll and soluble protein concentrations and the antioxidant enzyme activities in the leaves were initially increased at a low concentration of TCS(at 7 days of exposure),they decreased significantly over time.Compared to the leaves,the physiological indexes of the roots were more sensitive to the ecotoxicological effects of TCS.The inhibition effects of TCS on H.verticillata were signifi-cantly higher than those on E.crassipes,which may be associated with the absorbing abilities of TCS and the growth characteristics of the plants.Pearson’s correlation analysis found a significant negative correlation between the TCS concentrations and the antioxidant enzyme activities in the plants.Conclusions This study highlighted the differences in the uptake and enrichment process and toxic effects of TCS by different aquatic plants.Compared with E.crassipes,H.verticillata is more sensitive to TCS toxicity.

Algal-bloom control by allelopathy of aquatic macrophytes—A review

Algal-bloom control is an important issue for water environment protection as it induces several negative impacts on the lives of aquatic organisms,aquaculture,landscaping,and human health.The development of an environment-friendly,cost-effective,and convenient alternative for controlling algal bloom has gained much concern.Using the allelopathy of aquatic macrophytes as a novel and safe method for algal-bloom control is a promising alternative.This paper reviews the development and potential application about allelopathy of aquatic plants on algae,including the allelopathic research history,the potential research problems,the research methodology,and the reported aquatic macrophytes and their inhibitory allelochemicals.Potential modes of inhibition action of allelochemicals on algae,possible ways for application,and future development directions of research on algal-bloom control by aquatic macrophytes were also presented.

The Bowati in Kordofan, Sudan: Unique Aquatic Ecosystems of a Non-Nilotic In-Land Delta

This paper describes the unique in-land, non-Nilotic delta of Wadi El Galla, a seasonal water course which originates in the Nuba Mountains of Kordofan region and terminates in a chain of small ponds each known locally as a Bouta (pl Bowati). The Bowati are inhabited by a community of aquatic plants forming a wide spectrum ranging from small true (Euophytes) to large woody trees. The euophytes encountered were grouped into six categories. The free-floating species were represented by the small Lemna purpusilla Torr. and the larger Pistia stratiotes L. while only one submerged species was found: Ottelia alismoides (Planch.) Welp. One suspended species was found, Utricularia stellaris L. F. Three species of the floating-leaved plants were encountered namely, Nymphaea lotus L., N. micrantha Guill. & Perrott and Nymphoides nilotica (Kotschy & Peyr.) Léonard. The emergent Limnophyton obtusifolium (L.) Miq. was very prominent in all the Bowat constituting with N. lotus the two dominant species. Trailing from the Bouta edge and forming thick mats on the open water is Neptunia oleracea Lour., a member of the Fabaceae family. Within these euophytes and towering to over ten meters is the woody tree Mitragyna inermis Kuntze. Some of herbaceous plants are a source of food for the local community such as the bulbils of Nymphaea micrantha. These meagrely studied ecosystems are under threat from natural and anthropogenic factors. The former are the recurrent drought, climate change, and the latter are due to urbanization, overexploitation and oil activities. There is an urgent need for delineating and mapping the geomorphology, drainage patterns of Al Muglad in-land delta as well as the number and sites of the Bowati. The taxonomy of the aquatic species, their nutritive and medicinal values are other areas of research. Within such a context, a concerted national and international endeavour is called for to conserve these unique ecosystems and conceivably, declaring them as protected sites.

Photosynthesis of Submerged and Surface Leaves of the Dwarf Water Lily(Nymphoides aquatica)Using PAM Fluorometry

Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt) and POER_(max) are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2) s^(-1),PPFD;POER_(max)≈4.95µmol O_(2) g^(-1) Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈38.1µmol O_(2) g^(-1) Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈76.1µmol O_(2) g^(-1) Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2) d^(-1) in full sun and as much as 1.4 gC m^(-2) d^(-1) in shaded submerged leaves.There is midday inhibition of photosynthesis.

DIATOM COMMUNITY SUCCESSION AND NUTRIENT EVOLUTION RECORDED FROM A SEDIMENT CORE OF THE LONGGAN LAKE, A LARGE SHALLOW LAKE IN EAST CHINA

The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) and chlorophyll-a (Chl-a) concentration were quantitatively reconstructed for the past 2000 years, based on the diatom-TP and diatom-Chla transfer functions. The shifts of diatom assemblages also mirrored the developments of aquatic plant, reflecting the characters of aquatic ecosystem evolution. The inferred epilimnetic TP concentration fluctuated within a small range of 36 to 62μg/L, indicating the lake remained a relative stable mesotrophic status in the long historical period. The periodical variations of the diatom assemblage and trophic status suggest a mitigating function of shallow macrophyte-dominated lakes to nutrient input. The changes of lakes’ trophic status don’t linearly respond to the human disturbance in the catchment. The dynamics mechanism of phosphorus in macrophyte-dominated lakes, as inferred from diatoms, will provide a scientific foundation for the prediction of trophic status change in a shallow lake, as well as the lake ecological restoration and management decisions.

Variation and potential influence factors of foliar pH in land-water ecozones of three small plateau lakes

Aims Foliar pH of terrestrial plants,a trait tightly associated with plant physiology and nutrient utilization,varies with plant functional types(PFTs)and environmental changes.However,it is yet unclear about the variation in foliar pH of aquatic plants,and the difference between aquatic and terrestrial plants.Methods Foliar pH,leaf carbon,nitrogen content of plants along the lakeshore zones and the environmental conditions(water or soil pH,water status)of the corresponding vegetation of three small plateau lakes were investigated,to determine the variation and potential influence factors of foliar pH at both PFT and community levels.Important Findings Foliar pH varied largely among aquatic plants,and across aquatic,helophytic and terrestrial plants.Floating-leaved macrophytes had more acidic foliage(pH=4.21±0.05)than emergent(5.71±0.07)and submerged macrophytes(5.82±0.06).Foliar pH of aquatic herbs(5.43±0.10)was lower than that of helophytic(6.12±0.07)and terrestrial herbs(5.74±0.05).Terrestrial herbs had significantly higher foliar pH than woody plants.The variation in foliar pH across PFTs may be mainly ascribed to leaf structure,light utilization and nutrient characteristics.Consistent with the pattern on PFT level,aquatic communities had more acidic foliage than terrestrial communities,which was mainly shaped by species composition,water status and environmental pH.This study documented the first-time foliar pH of aquatic plants,and comparison of foliar pH among various plant types at a landscape scale.Our results provide bases for further exploration of the underlying mechanism and its ecological significance for wetland ecosystems.