Decades of species composition changes can lead to the eutrophication-driven loss of submerged macrophytes in shallow lakes.Investigating the mechanisms of these nature-and human driven changes is crucial for the rest...Decades of species composition changes can lead to the eutrophication-driven loss of submerged macrophytes in shallow lakes.Investigating the mechanisms of these nature-and human driven changes is crucial for the restoration and management of such lakes.To investigate the changes in aquatic macrophyte communities over the past two centuries,we analyzed macrofossils in sediments from a^(210)Pb-dated core obtained in Dongping Lake in the lower Huanghe(Yellow)River Basin,eastern China.Multiple factor analysis(MFA)revealed an association between macrophyte shifts and changes in various environmental stressors(invertebrates,grain size,geochemistry,and documented records),indicating that macrophyte community changes before 1960 were predominately driven by flood disturbances.Ever since,anthropogenic pollution and the construction of water conservancy projects have caused variations in hydrology and nutrients,leading to significant changes in the composition of macrophyte communities.Macrofossil data reveal a decline in diversity and pollution-intolerant species during the late 1980 s and the early 2000 s,which is indicative of eutrophication.We also found that the current environment of Dongping Lake exhibits a clear degeneration in emergent plants and a proliferation of macrophyte species associated with eutrophic conditions,which could be attributed to water level fluctuation and nutrient input due to the water supply from the eastern route of the South-to-North Water Diversion Project as well as climate warming.Our results provide valuable insights for assessing ecosystem health and the restoration and management of Dongping Lake and similar lakes in the Huanghe River region and elsewhere.展开更多
The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphyti...The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.展开更多
The presence,abundance,and distribution of aquatic macrophytes and their growth forms in the river Krka in Slovenia were studied.The studied slow-flowing lowland River Krka is also called a»green river«since...The presence,abundance,and distribution of aquatic macrophytes and their growth forms in the river Krka in Slovenia were studied.The studied slow-flowing lowland River Krka is also called a»green river«since it is overgrown with macrophytes from its source to its outflow to the river Sava.The environmental parameters of the river ecosystem were also assessed using the modified version of the RCE(Riparian,Channel,and Environmental Inventory)method.Within 24 sections reaching from 100 to 250 m,23 taxa of macrophytes were found.Sections were distributed noncontinuously from the source to the outflow more or less equally along the river course.The invasive alien species Elodea canadensis reached the highest relative abundance,followed by Ranunculus trichophyllus,Potamogeton crispus,Myriophyllum spicatum,Ceratophyllum demersum,and Potamogeton nodosus.Potamogeton crispus was present in most of the studied sections followed by Nasturtium officinale and M.spicatum.The river offers suitable conditions for the high diversity of macrophytes regarding the type of substrate,low flow velocity,heterogeneity of habitats,and relatively high concentrations of nutrients.In comparison to the survey performed in 2003,when the river Krka was surveyed continuously from the source to the outflow,we found that seven of the submerged and natant macrophytes were not detected in 2020.Macrophytes,growing in the river Krka,indicated meso-to eutrophic conditions.Five species recorded in the river Krka are listed on the Red list of endangered species in Slovenia,indicating the need to conserve the river ecosystem.展开更多
Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships bet...Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships between submerged macrophyte presence and the ratio of Secchi disk depth(SDD) to water depth, i.e. SDD/depth, nutrients and wind, we conducted an extensive sampling campaign in a macrophyte-dominated area of the eastern region( n = 36) in 2016 in Lake Taihu, China, and combined the data gathered with results from extensive physico-chemical monitoring data from the entire lake. We confirmed that SDD/Depth is the primary factor controlling the community composition of macrophytes and showed that plant abundance increased with increasing SDD/Depth ratio( p < 0.01), but that only SDD/Depth > 0.4 ensured growth of submerged macrophytes. Total phosphorus and total nitrogen also influenced the growth and community composition of macrophytes( p < 0.01), while Chl a was an indirectly affecting factor by reducing underwater light penetration. Wave height significantly influenced plant abundance( p < 0.01), whereas it had little effect on the biomass( p > 0.05). The key to restore the macrophyte beds in the lake is to reduce the nutrient loading. A decrease of the water level may contribute as well in the shallow bays but will not bring plants back in the main part of the lake. As the tolerance of shade and nutrients varied among the species studied, this should be taken into account in the restoration of lakes by addition of plants.展开更多
Leaves of terrestrial and aquatic plants are home to a wide diversity of bacterial species. However, the diversity and variability of epiphytic bacteria on their submerged plant hosts remains poorly understood. We inv...Leaves of terrestrial and aquatic plants are home to a wide diversity of bacterial species. However, the diversity and variability of epiphytic bacteria on their submerged plant hosts remains poorly understood. We investigated the diversity and composition of epiphytic bacteria from two common submerged macrophytes: Vallisneria natans and Hydrilla verticillata in Taihu Lake, Jiangsu, China, using methods of terminal restriction fragment length polymorphisms (T-RFLP) and clone library analyses targeted at bacterial 16S rRNA genes. The results show that: (1) the libraries of the two waterweeds contain wide phylogenetic distribution of bacteria, and that the sequences of the two libraries can be separated into 93 OTUs (at 97% similar value); (2) Betaproteobacteria, including Burkholderiales, was the most abundant bacterial group on both plants. Cyanobacteria and Gammaproteobacteria were the second largest groups on V. natans and H. verticillata, respectively. Both clone libraries included some sequences related to those of methanotrophs and nitrogen-fixing bacteria; (3) Cluster analysis of the T-RFLP profiles showed two distinct clusters corresponding to the two plant populations. Both ANOSIM of the T-RFLP data and Libshuff analysis of the two clone libraries indicated a significant difference in epiphytic bacterial communities between the two plants. Therefore, the epiphytic bacterial communities on submerged macrophytes appear to be diverse and host-specific, which may aid in understanding the ecological functions of submerged macrophytes in general.展开更多
In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were ...In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. vertieillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length ofplantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. vertieillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.展开更多
Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings:macrophyte-dominated and phytoplankton-dominated water regimes.An ecosystem regime shift from macrophytes to phy...Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings:macrophyte-dominated and phytoplankton-dominated water regimes.An ecosystem regime shift from macrophytes to phytoplankton blooming typically reduces the number of species of invertebrates and fishes and results in the homogenization of communities in freshwater lakes.We investigated how microbial biodiversity has responded to a shift of the ecosystem regime in Dianchi Lake,which was previously fully covered with submerged macrophytes but currently harbors both ecological states.We observed marked divergence in the diversity and community composition of bacterioplankton between the two regimes.Although species richness,estimated as the number of operational taxonomic units and phylogenetic diversity(PD),was higher in the phytoplankton dominated ecosystem after this shift,the dissimilarity of bacterioplankton community across space decreased.This decrease in beta diversity was accompanied by loss of planktonic bacteria unique to the macrophyte-dominated ecosystem.Mantel tests between bacterioplankton community distances and Euclidian distance of environmental parameters indicated that this reduced bacterial community differentiation primarily reflected the loss of environmental niches,particularly in the macrophyte regime.The loss of this small-scale heterogeneity in bacterial communities should be considered when assessing long-term biodiversity changes in response to ecosystem regime conversions in freshwater lakes.展开更多
In a 10-day aquarium experiment, this investigation examines macrophyte restoration in eutrophic Lake Taihu, the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concent...In a 10-day aquarium experiment, this investigation examines macrophyte restoration in eutrophic Lake Taihu, the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte, Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase （SOD） activity of the plant＇s leaves and induced the catalase （CAT） and peroxidase （POD） activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations, whereas the malonaldehyde （MDA） increased significantly at chlorophyll a （Chl a） concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 〉109 μg/L. Additionally, high biomass of V. asiatica （2 222 g FW/m^2） can inhibit the reproduction of cyanobacteria more significantly than low biomass （1 111 g FW/m^2）. High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L, as expressed by the increased MDA in leaves, compared with low biomass of K asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu.展开更多
Three species of aquatic plants (Scirpus validus, Phragmites australis and Acorus calamus) were used as experimental materials to study their capacity to purify contaminated water and their effects on water pH and dis...Three species of aquatic plants (Scirpus validus, Phragmites australis and Acorus calamus) were used as experimental materials to study their capacity to purify contaminated water and their effects on water pH and dissolved oxygen (DO). The water was contaminated with different concentrations of nitrate (5 mg/L, 15 mg/L and 25 mg/L). The results indicated that the concentration of nitrate, species of aquatic plant and their interaction significantly impacted denitrification (P = 0.00). Under the same concentrations, the three species of aquatic plants provided varying degrees of purification. Acorus calamus provided effective purification under all three concentrations of nitrate wastewater, with removal percentages of 87.73%, 83.80% and 86.72% for nitrate concentrations of 5 mg/L, 15 mg/L and 25 mg/L, respectively. In terms of the purification ability by unit fresh weight, Acorus calamus exhibited the worst purification capacity, whereas the capacities of Scirpus validus and Phragmites australis were higher. The purification capacity of Scirpus validus for the three concentrations was as follows: 0.08 mg/(L·g FW), 0.29 mg/(L·g FW), and 0.51 mg/(L·g FW). The capacity of Phragmites australis was 0.07 mg/(L·g FW), 0.25 mg/(L·g FW), and 0.53 mg/(L·g FW). The capacity of Acorus calamus was 0.04 mg/(L·g FW), 0.12 mg/(L·g FW), and 0.21 mg/(L·g FW). Under increased concentrations of nitrate, the three species of aquatic plants exhibited various degrees of increased purification capacity. Under the different concentrations of nitrate, the three species exhibited the same trends with respect to water pH and DO, increasing first and then falling. The pH remained at approximately 7.5, and the DO fell to 4.0 mg/L. A comprehensive analysis reveals that Acorus calamus provides excellent nitrate purification, although by unit fresh weight, both Scirpus validus and Phragmites australis provide superior purification capacity.展开更多
Denitrifying bacteria in epiphytic biofilms play a crucial role in nitrogen cycle in aquatic habitats.However,little is known about the connection between algae and denitrifying bacteria and their assembly processes i...Denitrifying bacteria in epiphytic biofilms play a crucial role in nitrogen cycle in aquatic habitats.However,little is known about the connection between algae and denitrifying bacteria and their assembly processes in epiphytic biofilms.Epiphytic biofilms were collected from submerged macrophytes(Patamogeton lucens and Najas marina L.)in the Caohai Lake,Guizhou,SW China,from July to November 2020 to:(1)investigate the impact of abiotic and biotic variables on denitrifying bacterial communities;(2)investigate the temporal variation of the algae-denitrifying bacteria co-occurrence networks;and(3)determine the contribution of deterministic and stochastic processes to the formation of denitrifying bacterial communities.Abiotic and biotic factors influenced the variation in the denitrifying bacterial community,as shown in the Mantel test.The co-occurrence network analysis unveiled intricate interactions among algae to denitrifying bacteria.Denitrifying bacterial community co-occurrence network complexity(larger average degrees representing stronger network complexity)increased continuously from July to September and decreased in October before increasing in November.The co-occurrence network complexity of the algae and nirS-encoding denitrifying bacteria tended to increase from July to November.The co-occurrence network complexity of the algal and denitrifying bacterial communities was modified by ammonia nitrogen(NH_(4)^(+)-N)and total phosphorus(TP),pH,and water temperature(WT),according to the ordinary least-squares(OLS)model.The modified stochasticity ratio(MST)results reveal that deterministic selection dominated the assembly of denitrifying bacterial communities.The influence of environmental variables to denitrifying bacterial communities,as well as characteristics of algal-bacterial co-occurrence networks and the assembly process of denitrifying bacterial communities,were discovered in epiphytic biofilms in this study.The findings could aid in the appropriate understanding and use of epiphytic biofilms denitrification function,as well as the enhancement of water quality.展开更多
Antioxidant systems are vital in life activities of macrophytes.Species with diff erent life forms need to cope with distinct environments by modifying physiological characters,especially antioxidant systems.In order ...Antioxidant systems are vital in life activities of macrophytes.Species with diff erent life forms need to cope with distinct environments by modifying physiological characters,especially antioxidant systems.In order to find diff erences among life forms and consequence of lake eutrophication,we studied three antioxidant enzymes activity(superoxide dismutase(SOD),ascorbate oxidase(APX)and catalase(CAT))and total soluble phenolics(TP)content in leaves of 26 macrophyte species in September 2013 in Lake Erhai,China.We found that antioxidation varied accordingly with life forms.The activities of SOD and APX in emergent macrophytes(EM)and floating-leaved macrophytes(FM)were much lower than those of submerged macrophytes(SM).On the contrary,TP content was much higher in EM and FM species.There was a negative correlation between TP and antioxidant enzyme activities(CAT and APX).The results suggested that EM and FM species rely on phenolics might to adapt to adverse environments(higher herbivores predation pressure and UV radiation intensity),while SM species more rely on antioxidant enzymes possibly due to lower demand for antioxidation and/or lack of light and inorganic C availability for phenolics synthesis.We also found FM species represent highest fitness in term of antioxidant system,which would lead to overgrowth of FM species and littoral zone bogginess during lake eutrophication.Finally,it is necessary to carry out the verification experiment under the control condition in the later stage,especially for the dominant ones in eutrophic lakes,to understand the exact adaptive mechanisms of them.展开更多
A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth tre...A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition（N, NH4Cl100, 200, 400 mg/kg, respectively） were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4^＋may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.展开更多
Macrophytes play critical ecological role in inland water bodies, especially in shallow systems. Water hyacinth (Eichhornia crassipes) is an invasive plant species introduced to Ethiopian water bodies around the mid 2...Macrophytes play critical ecological role in inland water bodies, especially in shallow systems. Water hyacinth (Eichhornia crassipes) is an invasive plant species introduced to Ethiopian water bodies around the mid 20th century with recently exacerbated devastating ecological and economic consequences. Here we report the impact of the invasive plant species on macrophyte species assemblage and biodiversity in Lake Abaya, southwestern Ethiopia. We compared four sites in Lake Abaya, two hyacinth infested and two non-infested, each site consisting of 15 plots. Our results showed that water hyacinth affects the macrophyte community composition, abundance and diversity negatively. Even though some macrophyte species from the Poaceae and Cyperaceae families appear to coexist with the alien plant, the invasive species has reduced macrophyte abundance and diversity at the infested sites, and in some cases changed the community to nearly monotypic flora. Our data affirm that water hyacinth has the potential to alter macrophyte composition, abundance and diversity in the wider Ethiopian aquatic ecosystems. A broad & closer, systematic and comprehensive look at the short and long term consequences of its expanding invasion within the framework of specific local environmental, ecological and societal conditions is long-overdue.展开更多
Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional an...Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional and existing species of different growth forms,particularly under the low light and high nutrient conditions of eutrophic lakes.We measured the functional traits of mature Vallisneria natans(Lour.)Hara plants and Potamogeton crispus L.shoots in monoculture and mosaic patterns under different light and nutrient conditions.The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients,but the reverse was true for P.crispus biomass allocation.Moreover,interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species.Specifically,the interaction of P.crispus to V.natans was biased towards competition,while the interaction of V.natans to P.crispus was converted from facilitation to competition by eutrophication,particularly in the homogenous mosaic growth pattern.This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system.In addition,we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation,even if their growth forms and growing seasons are different.These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.展开更多
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 ...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.展开更多
Investigations in 1991 to 1993 showed that a perennial submerged plant, Potamogeton maackianus A.Benn., which always dominates the submerged vegetation in the shallow lakes in the middle and lower basins of the Changj...Investigations in 1991 to 1993 showed that a perennial submerged plant, Potamogeton maackianus A.Benn., which always dominates the submerged vegetation in the shallow lakes in the middle and lower basins of the Changjiang River, had been extinct from Donghu Lake of Wuhan, and that some other submerged plants sensitive to water contamination had also dissappeared or declined in the lake. The r-selected species, Najas marina L., Myriophyllum spicatum L. and Vallisneria sp. had superseded the K-selected one, P. maackianus, to co-dominate the submerged vegetation. Several hypereutrophic or eutrophic subregions had switched from macrophyte dominance to phytoplankton dominance, while the shrinkage of macrophytes and the deterioration of water quality had also become more and more severe in the other subregions. The emergent macrophytes were poorly developed and the share of leaf-floating plants hed increased in the lake. It was found that the existing vegetation fluctuated drastically from year to year. Macrophyte restoration experiments carried out in large enclosures at 3 subregions of different trophic state, suggested that the aquatic vegetation of less polluted sublakes,such as Niuchao, Tanglin and Houhu Lakes, could recover spontaneously after stocking of herbivorous fish stopped, that K-selected plants should be introduced into these sublakes to enhance the stability of aquatic vegetation,that a prerequisite for the recovery of macrophytes in the severely polluted basins is the reduction of external and internal nutrient loadingr coupled with feasible management measures; and that r-selected submerged species should be used as pioneer plants for the macrophyte recovery.The recently introduced exotic submerged plant, Elodea canadensis,transplanted into the Houhu Enclosure could survive but failed to surive summer in the enclosures located in the hypereutrophic Shuiguohu Bay.展开更多
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 ...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展开更多
In this study, we estimated the growth area of aquatic macrophytes that have expanded spontaneously in Lake Shinji, located in eastern Shimane Prefecture, Japan, using Terra satellite Advanced Spaceborne Thermal Emiss...In this study, we estimated the growth area of aquatic macrophytes that have expanded spontaneously in Lake Shinji, located in eastern Shimane Prefecture, Japan, using Terra satellite Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Visible and near infrared ASTER data from April, August, and September 2012 were used. The water depth at which ASTER can detect submersed aquatic macrophytes using in situ spectral reflectance of aquatic macrophytes and a bio-optical model was also examined. As a result, when the threshold value of a normalized difference vegetation index (NDVI) was set to 0, only aquatic macrophytes up to a depth of approximately 10 cm could be detected. The growth area of aquatic macrophytes detected by NDVI from ASTER data was in relatively good agreement with the growth area as observed by aerial photography.展开更多
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 pres...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.展开更多
Phytoremediation is a cheap and environmentally friendly technique in which green plants in situ are used to clean the soil, sediments and water of heavy metals. This study investigated the phytoremediation potential ...Phytoremediation is a cheap and environmentally friendly technique in which green plants in situ are used to clean the soil, sediments and water of heavy metals. This study investigated the phytoremediation potential of six naturally occurring macrophytes from Nange (a stream in Buea municipality where cars have been driven into and washed for over 20 years). Plant samples were collected before and after car wash, then analysed for copper, zinc, lead and cadmium accumulation. There was an increase in concentration of all the four heavy metals in water after carwash point, with Zn having the highest concentration (0.27 mg/L). Mean concentration of the heavy metals in the water showed that Zn and Pb had the highest concentrations (0.24 mg/L each) while the least concentration was obtained in Cu (0.12 mg/kg). Heavy metal concentrations in the sediments were higher after car wash point than before. Cadmium had the highest concentration (5.58 mg/kg) while Cu had the least (0.75 mg/kg). <em>Ludwigia peruviana</em> had the highest BAFs for all the heavy metals (22.95 for Cu, 33.41 for Zn, 21.79 for Pb and 7.85 for Cd). Species with the leasts were: <em>Anubias barteri</em> for Cu (7.16), <em>Polygonum persicaria</em> for Zn (14.28), <em>Rorippa nasturtium-aquaticum</em> for Pb (11.60) and <em>Vallisneria spiralis</em> for Cd (1.98). <em>L. peruviana</em> had the highest BAC values (Cu = 10.11, Zn = 14.73, Pb = 11.39, Cd = 3.85) and BCF values (Cu = 12.84, Zn = 18.67, Pb = 10.40, Cd = 4.00). <em>A. barteri</em> had the highest TF (Cu = 1.49, Zn = 1.27, Cd = 1.99) except for Pb where both <em>A. barteri </em>and <em>L. peruviana</em> each had a TF of 1.10. While all the six plants were found to be good accumulators of the heavy metals, <em>L. peruviana</em> showed remarkable efficiency indicating that the species is a good candidate for cleaning such environments.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.42007397,41871073)the Natural Science Foundation of Shandong Province(No.ZR2020QD002)。
文摘Decades of species composition changes can lead to the eutrophication-driven loss of submerged macrophytes in shallow lakes.Investigating the mechanisms of these nature-and human driven changes is crucial for the restoration and management of such lakes.To investigate the changes in aquatic macrophyte communities over the past two centuries,we analyzed macrofossils in sediments from a^(210)Pb-dated core obtained in Dongping Lake in the lower Huanghe(Yellow)River Basin,eastern China.Multiple factor analysis(MFA)revealed an association between macrophyte shifts and changes in various environmental stressors(invertebrates,grain size,geochemistry,and documented records),indicating that macrophyte community changes before 1960 were predominately driven by flood disturbances.Ever since,anthropogenic pollution and the construction of water conservancy projects have caused variations in hydrology and nutrients,leading to significant changes in the composition of macrophyte communities.Macrofossil data reveal a decline in diversity and pollution-intolerant species during the late 1980 s and the early 2000 s,which is indicative of eutrophication.We also found that the current environment of Dongping Lake exhibits a clear degeneration in emergent plants and a proliferation of macrophyte species associated with eutrophic conditions,which could be attributed to water level fluctuation and nutrient input due to the water supply from the eastern route of the South-to-North Water Diversion Project as well as climate warming.Our results provide valuable insights for assessing ecosystem health and the restoration and management of Dongping Lake and similar lakes in the Huanghe River region and elsewhere.
基金supported by the National Special Program of Water Environment(No.2017ZX07204002)the National Natural Science Foundation of China(No.41871082)。
文摘The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.
基金Javna Agencija za Raziskovalno Dejavnost RS,Grant/Award Number:P1-0212。
文摘The presence,abundance,and distribution of aquatic macrophytes and their growth forms in the river Krka in Slovenia were studied.The studied slow-flowing lowland River Krka is also called a»green river«since it is overgrown with macrophytes from its source to its outflow to the river Sava.The environmental parameters of the river ecosystem were also assessed using the modified version of the RCE(Riparian,Channel,and Environmental Inventory)method.Within 24 sections reaching from 100 to 250 m,23 taxa of macrophytes were found.Sections were distributed noncontinuously from the source to the outflow more or less equally along the river course.The invasive alien species Elodea canadensis reached the highest relative abundance,followed by Ranunculus trichophyllus,Potamogeton crispus,Myriophyllum spicatum,Ceratophyllum demersum,and Potamogeton nodosus.Potamogeton crispus was present in most of the studied sections followed by Nasturtium officinale and M.spicatum.The river offers suitable conditions for the high diversity of macrophytes regarding the type of substrate,low flow velocity,heterogeneity of habitats,and relatively high concentrations of nutrients.In comparison to the survey performed in 2003,when the river Krka was surveyed continuously from the source to the outflow,we found that seven of the submerged and natant macrophytes were not detected in 2020.Macrophytes,growing in the river Krka,indicated meso-to eutrophic conditions.Five species recorded in the river Krka are listed on the Red list of endangered species in Slovenia,indicating the need to conserve the river ecosystem.
基金jointly funded by the National Key R&D Program of China(No.2017YFC0405205)the Major Projects on Control and Rectification of Water Body Pollution(No.2017ZX07203–004)+1 种基金the National Natural Science Foundation of China(Nos.42071118 and 41621002)supported by the TüBITAK,BIDEB program 2232.
文摘Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships between submerged macrophyte presence and the ratio of Secchi disk depth(SDD) to water depth, i.e. SDD/depth, nutrients and wind, we conducted an extensive sampling campaign in a macrophyte-dominated area of the eastern region( n = 36) in 2016 in Lake Taihu, China, and combined the data gathered with results from extensive physico-chemical monitoring data from the entire lake. We confirmed that SDD/Depth is the primary factor controlling the community composition of macrophytes and showed that plant abundance increased with increasing SDD/Depth ratio( p < 0.01), but that only SDD/Depth > 0.4 ensured growth of submerged macrophytes. Total phosphorus and total nitrogen also influenced the growth and community composition of macrophytes( p < 0.01), while Chl a was an indirectly affecting factor by reducing underwater light penetration. Wave height significantly influenced plant abundance( p < 0.01), whereas it had little effect on the biomass( p > 0.05). The key to restore the macrophyte beds in the lake is to reduce the nutrient loading. A decrease of the water level may contribute as well in the shallow bays but will not bring plants back in the main part of the lake. As the tolerance of shade and nutrients varied among the species studied, this should be taken into account in the restoration of lakes by addition of plants.
基金Supported by the National Natural Science Foundation of China(No.40730528)the National Basic Research Program of China(973Program)(No.2008CB418104)+2 种基金the Knowledge Innovation Project of Chinese Academy of Sciences(No.KZCX2-YW-JC302)the Jiangsu Provincial Science Foundation(No.BK2009024)the Frontier Foundation of Nanjing Institute of Geography & Limnology,Chinese Academy of Sciences(No.09SL021001)
文摘Leaves of terrestrial and aquatic plants are home to a wide diversity of bacterial species. However, the diversity and variability of epiphytic bacteria on their submerged plant hosts remains poorly understood. We investigated the diversity and composition of epiphytic bacteria from two common submerged macrophytes: Vallisneria natans and Hydrilla verticillata in Taihu Lake, Jiangsu, China, using methods of terminal restriction fragment length polymorphisms (T-RFLP) and clone library analyses targeted at bacterial 16S rRNA genes. The results show that: (1) the libraries of the two waterweeds contain wide phylogenetic distribution of bacteria, and that the sequences of the two libraries can be separated into 93 OTUs (at 97% similar value); (2) Betaproteobacteria, including Burkholderiales, was the most abundant bacterial group on both plants. Cyanobacteria and Gammaproteobacteria were the second largest groups on V. natans and H. verticillata, respectively. Both clone libraries included some sequences related to those of methanotrophs and nitrogen-fixing bacteria; (3) Cluster analysis of the T-RFLP profiles showed two distinct clusters corresponding to the two plant populations. Both ANOSIM of the T-RFLP data and Libshuff analysis of the two clone libraries indicated a significant difference in epiphytic bacterial communities between the two plants. Therefore, the epiphytic bacterial communities on submerged macrophytes appear to be diverse and host-specific, which may aid in understanding the ecological functions of submerged macrophytes in general.
基金Supported by the National Natural Science Foundation of China (39925007)the High Technology Research and Development Program of China (2002AA60l021)the Knowledge Innovation Program Key Project of Chinese Academy of Sciences (KSCX2-SW-102)
文摘In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. vertieillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length ofplantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. vertieillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.
基金Supported by the National Natural Science Foundation of China(Nos.U1202231,31225004)the National Science Foundation for Young Scientists of China(No.31200383)
文摘Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings:macrophyte-dominated and phytoplankton-dominated water regimes.An ecosystem regime shift from macrophytes to phytoplankton blooming typically reduces the number of species of invertebrates and fishes and results in the homogenization of communities in freshwater lakes.We investigated how microbial biodiversity has responded to a shift of the ecosystem regime in Dianchi Lake,which was previously fully covered with submerged macrophytes but currently harbors both ecological states.We observed marked divergence in the diversity and community composition of bacterioplankton between the two regimes.Although species richness,estimated as the number of operational taxonomic units and phylogenetic diversity(PD),was higher in the phytoplankton dominated ecosystem after this shift,the dissimilarity of bacterioplankton community across space decreased.This decrease in beta diversity was accompanied by loss of planktonic bacteria unique to the macrophyte-dominated ecosystem.Mantel tests between bacterioplankton community distances and Euclidian distance of environmental parameters indicated that this reduced bacterial community differentiation primarily reflected the loss of environmental niches,particularly in the macrophyte regime.The loss of this small-scale heterogeneity in bacterial communities should be considered when assessing long-term biodiversity changes in response to ecosystem regime conversions in freshwater lakes.
基金Supported by the Research Institute for East Asia Environments of Kyushu University and Mitsubishi Corporation in Japan
文摘In a 10-day aquarium experiment, this investigation examines macrophyte restoration in eutrophic Lake Taihu, the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte, Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase （SOD） activity of the plant＇s leaves and induced the catalase （CAT） and peroxidase （POD） activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations, whereas the malonaldehyde （MDA） increased significantly at chlorophyll a （Chl a） concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 〉109 μg/L. Additionally, high biomass of V. asiatica （2 222 g FW/m^2） can inhibit the reproduction of cyanobacteria more significantly than low biomass （1 111 g FW/m^2）. High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L, as expressed by the increased MDA in leaves, compared with low biomass of K asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu.
文摘Three species of aquatic plants (Scirpus validus, Phragmites australis and Acorus calamus) were used as experimental materials to study their capacity to purify contaminated water and their effects on water pH and dissolved oxygen (DO). The water was contaminated with different concentrations of nitrate (5 mg/L, 15 mg/L and 25 mg/L). The results indicated that the concentration of nitrate, species of aquatic plant and their interaction significantly impacted denitrification (P = 0.00). Under the same concentrations, the three species of aquatic plants provided varying degrees of purification. Acorus calamus provided effective purification under all three concentrations of nitrate wastewater, with removal percentages of 87.73%, 83.80% and 86.72% for nitrate concentrations of 5 mg/L, 15 mg/L and 25 mg/L, respectively. In terms of the purification ability by unit fresh weight, Acorus calamus exhibited the worst purification capacity, whereas the capacities of Scirpus validus and Phragmites australis were higher. The purification capacity of Scirpus validus for the three concentrations was as follows: 0.08 mg/(L·g FW), 0.29 mg/(L·g FW), and 0.51 mg/(L·g FW). The capacity of Phragmites australis was 0.07 mg/(L·g FW), 0.25 mg/(L·g FW), and 0.53 mg/(L·g FW). The capacity of Acorus calamus was 0.04 mg/(L·g FW), 0.12 mg/(L·g FW), and 0.21 mg/(L·g FW). Under increased concentrations of nitrate, the three species of aquatic plants exhibited various degrees of increased purification capacity. Under the different concentrations of nitrate, the three species exhibited the same trends with respect to water pH and DO, increasing first and then falling. The pH remained at approximately 7.5, and the DO fell to 4.0 mg/L. A comprehensive analysis reveals that Acorus calamus provides excellent nitrate purification, although by unit fresh weight, both Scirpus validus and Phragmites australis provide superior purification capacity.
基金Supported by the National Natural Science Foundation of China(No.41867056)the Guizhou Provincial Key Technology R&D Program(Nos.2021470,2023216)。
文摘Denitrifying bacteria in epiphytic biofilms play a crucial role in nitrogen cycle in aquatic habitats.However,little is known about the connection between algae and denitrifying bacteria and their assembly processes in epiphytic biofilms.Epiphytic biofilms were collected from submerged macrophytes(Patamogeton lucens and Najas marina L.)in the Caohai Lake,Guizhou,SW China,from July to November 2020 to:(1)investigate the impact of abiotic and biotic variables on denitrifying bacterial communities;(2)investigate the temporal variation of the algae-denitrifying bacteria co-occurrence networks;and(3)determine the contribution of deterministic and stochastic processes to the formation of denitrifying bacterial communities.Abiotic and biotic factors influenced the variation in the denitrifying bacterial community,as shown in the Mantel test.The co-occurrence network analysis unveiled intricate interactions among algae to denitrifying bacteria.Denitrifying bacterial community co-occurrence network complexity(larger average degrees representing stronger network complexity)increased continuously from July to September and decreased in October before increasing in November.The co-occurrence network complexity of the algae and nirS-encoding denitrifying bacteria tended to increase from July to November.The co-occurrence network complexity of the algal and denitrifying bacterial communities was modified by ammonia nitrogen(NH_(4)^(+)-N)and total phosphorus(TP),pH,and water temperature(WT),according to the ordinary least-squares(OLS)model.The modified stochasticity ratio(MST)results reveal that deterministic selection dominated the assembly of denitrifying bacterial communities.The influence of environmental variables to denitrifying bacterial communities,as well as characteristics of algal-bacterial co-occurrence networks and the assembly process of denitrifying bacterial communities,were discovered in epiphytic biofilms in this study.The findings could aid in the appropriate understanding and use of epiphytic biofilms denitrification function,as well as the enhancement of water quality.
基金Supported by the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2016FBZ08)the Natural Science Foundation of Jiangxi Province(No.2015ZBBF6008)the National Natural Science Foundation of China(No.31200356)
文摘Antioxidant systems are vital in life activities of macrophytes.Species with diff erent life forms need to cope with distinct environments by modifying physiological characters,especially antioxidant systems.In order to find diff erences among life forms and consequence of lake eutrophication,we studied three antioxidant enzymes activity(superoxide dismutase(SOD),ascorbate oxidase(APX)and catalase(CAT))and total soluble phenolics(TP)content in leaves of 26 macrophyte species in September 2013 in Lake Erhai,China.We found that antioxidation varied accordingly with life forms.The activities of SOD and APX in emergent macrophytes(EM)and floating-leaved macrophytes(FM)were much lower than those of submerged macrophytes(SM).On the contrary,TP content was much higher in EM and FM species.There was a negative correlation between TP and antioxidant enzyme activities(CAT and APX).The results suggested that EM and FM species rely on phenolics might to adapt to adverse environments(higher herbivores predation pressure and UV radiation intensity),while SM species more rely on antioxidant enzymes possibly due to lower demand for antioxidation and/or lack of light and inorganic C availability for phenolics synthesis.We also found FM species represent highest fitness in term of antioxidant system,which would lead to overgrowth of FM species and littoral zone bogginess during lake eutrophication.Finally,it is necessary to carry out the verification experiment under the control condition in the later stage,especially for the dominant ones in eutrophic lakes,to understand the exact adaptive mechanisms of them.
基金supported by the National Basic Research Program (973) of China (No. 2012CB417004)the National Natural Science Foundation of China (Nos. U1202235,41173118, 41301544)the Shandong Provincial Natural Science Foundation (No. ZR2012DQ003)
文摘A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition（N, NH4Cl100, 200, 400 mg/kg, respectively） were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4^＋may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.
文摘Macrophytes play critical ecological role in inland water bodies, especially in shallow systems. Water hyacinth (Eichhornia crassipes) is an invasive plant species introduced to Ethiopian water bodies around the mid 20th century with recently exacerbated devastating ecological and economic consequences. Here we report the impact of the invasive plant species on macrophyte species assemblage and biodiversity in Lake Abaya, southwestern Ethiopia. We compared four sites in Lake Abaya, two hyacinth infested and two non-infested, each site consisting of 15 plots. Our results showed that water hyacinth affects the macrophyte community composition, abundance and diversity negatively. Even though some macrophyte species from the Poaceae and Cyperaceae families appear to coexist with the alien plant, the invasive species has reduced macrophyte abundance and diversity at the infested sites, and in some cases changed the community to nearly monotypic flora. Our data affirm that water hyacinth has the potential to alter macrophyte composition, abundance and diversity in the wider Ethiopian aquatic ecosystems. A broad & closer, systematic and comprehensive look at the short and long term consequences of its expanding invasion within the framework of specific local environmental, ecological and societal conditions is long-overdue.
基金Supported by the National Natural Science Foundation of China (Nos.U2240207,41971043,51809178)the Guangxi Key Research and Development Program of China (No.2018AB36010)。
文摘Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional and existing species of different growth forms,particularly under the low light and high nutrient conditions of eutrophic lakes.We measured the functional traits of mature Vallisneria natans(Lour.)Hara plants and Potamogeton crispus L.shoots in monoculture and mosaic patterns under different light and nutrient conditions.The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients,but the reverse was true for P.crispus biomass allocation.Moreover,interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species.Specifically,the interaction of P.crispus to V.natans was biased towards competition,while the interaction of V.natans to P.crispus was converted from facilitation to competition by eutrophication,particularly in the homogenous mosaic growth pattern.This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system.In addition,we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation,even if their growth forms and growing seasons are different.These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.
文摘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.
文摘Investigations in 1991 to 1993 showed that a perennial submerged plant, Potamogeton maackianus A.Benn., which always dominates the submerged vegetation in the shallow lakes in the middle and lower basins of the Changjiang River, had been extinct from Donghu Lake of Wuhan, and that some other submerged plants sensitive to water contamination had also dissappeared or declined in the lake. The r-selected species, Najas marina L., Myriophyllum spicatum L. and Vallisneria sp. had superseded the K-selected one, P. maackianus, to co-dominate the submerged vegetation. Several hypereutrophic or eutrophic subregions had switched from macrophyte dominance to phytoplankton dominance, while the shrinkage of macrophytes and the deterioration of water quality had also become more and more severe in the other subregions. The emergent macrophytes were poorly developed and the share of leaf-floating plants hed increased in the lake. It was found that the existing vegetation fluctuated drastically from year to year. Macrophyte restoration experiments carried out in large enclosures at 3 subregions of different trophic state, suggested that the aquatic vegetation of less polluted sublakes,such as Niuchao, Tanglin and Houhu Lakes, could recover spontaneously after stocking of herbivorous fish stopped, that K-selected plants should be introduced into these sublakes to enhance the stability of aquatic vegetation,that a prerequisite for the recovery of macrophytes in the severely polluted basins is the reduction of external and internal nutrient loadingr coupled with feasible management measures; and that r-selected submerged species should be used as pioneer plants for the macrophyte recovery.The recently introduced exotic submerged plant, Elodea canadensis,transplanted into the Houhu Enclosure could survive but failed to surive summer in the enclosures located in the hypereutrophic Shuiguohu Bay.
文摘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
文摘In this study, we estimated the growth area of aquatic macrophytes that have expanded spontaneously in Lake Shinji, located in eastern Shimane Prefecture, Japan, using Terra satellite Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Visible and near infrared ASTER data from April, August, and September 2012 were used. The water depth at which ASTER can detect submersed aquatic macrophytes using in situ spectral reflectance of aquatic macrophytes and a bio-optical model was also examined. As a result, when the threshold value of a normalized difference vegetation index (NDVI) was set to 0, only aquatic macrophytes up to a depth of approximately 10 cm could be detected. The growth area of aquatic macrophytes detected by NDVI from ASTER data was in relatively good agreement with the growth area as observed by aerial photography.
文摘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.
文摘Phytoremediation is a cheap and environmentally friendly technique in which green plants in situ are used to clean the soil, sediments and water of heavy metals. This study investigated the phytoremediation potential of six naturally occurring macrophytes from Nange (a stream in Buea municipality where cars have been driven into and washed for over 20 years). Plant samples were collected before and after car wash, then analysed for copper, zinc, lead and cadmium accumulation. There was an increase in concentration of all the four heavy metals in water after carwash point, with Zn having the highest concentration (0.27 mg/L). Mean concentration of the heavy metals in the water showed that Zn and Pb had the highest concentrations (0.24 mg/L each) while the least concentration was obtained in Cu (0.12 mg/kg). Heavy metal concentrations in the sediments were higher after car wash point than before. Cadmium had the highest concentration (5.58 mg/kg) while Cu had the least (0.75 mg/kg). <em>Ludwigia peruviana</em> had the highest BAFs for all the heavy metals (22.95 for Cu, 33.41 for Zn, 21.79 for Pb and 7.85 for Cd). Species with the leasts were: <em>Anubias barteri</em> for Cu (7.16), <em>Polygonum persicaria</em> for Zn (14.28), <em>Rorippa nasturtium-aquaticum</em> for Pb (11.60) and <em>Vallisneria spiralis</em> for Cd (1.98). <em>L. peruviana</em> had the highest BAC values (Cu = 10.11, Zn = 14.73, Pb = 11.39, Cd = 3.85) and BCF values (Cu = 12.84, Zn = 18.67, Pb = 10.40, Cd = 4.00). <em>A. barteri</em> had the highest TF (Cu = 1.49, Zn = 1.27, Cd = 1.99) except for Pb where both <em>A. barteri </em>and <em>L. peruviana</em> each had a TF of 1.10. While all the six plants were found to be good accumulators of the heavy metals, <em>L. peruviana</em> showed remarkable efficiency indicating that the species is a good candidate for cleaning such environments.
