Potamogeton Malaianus Research Articles

Nitrogen loading affects microbes, nitrifiers and denitrifiers attached to submerged macrophyte in constructed wetlands

Submerged macrophytes and biofilms are important components of wetlands. However, little is known about the changes of microbes in biofilms attached to submerged macrophytes upon nitrogen loading. This study investigated the changes of microbes, algae, nitrifiers and denitrifiers in biofilms attached to the leaves of artificial plants (AP), Potamogeton malaianus (PM), Vallisneria natans (VN) and Hydrilla verticillata (HV) under varied initial concentrations of total nitrogen (TN). Nitrogen addition increased biofilm biomass and changed dissolved oxygen concentrations and pH values in overlaying water. Epiphytic algal densities showed the same trend at the same N level:AP>PM>VN>HV. As revealed by cluster analysis at phylum level, algae compositions in biofilm from four plants showed some host-specific at 2 and 12mgL−1 TN, but was clustered in the same group at 22mgL−1 TN regardless of plant species. Submerged macrophytes had better performance in total N removal than AP. In general, N application significantly increased the abundance of amoA, nirK, nirS, napA and cnorB in biofilm. The abundance of the denitrification genes (nirK, nirS, napA, narG and cnorB) was positively correlated with nitrogen application, while amoA was correlated with concentration of dissolved oxygen. These results indicate that N loadings stimulated the growth of biofilms attached to submerged macrophyte and the removal of total N can be partially ascribed to the synergistic interactions of submerged macrophyte and biofilms in wetlands. These results highlight the ecological role of submerged macrophyte-biofilm system in nitrogen removal in wetlands.

Analyzing the effects of four submerged macrophytes with two contrasting architectures on zooplankton: A mesocosm experiment

<p>Increases in the structural complexity of submerged macrophytes are often shown to be linked to higher invertebrate abundance and diversity, but a number of studies have demonstrated, however, that this is not always the case. The objective of this study was to analyze the effects of four macrophyte species with two contrasting architectures (simple architecture with broad leaves: <em>Vallisneria spiralis</em> L. and <em>Potamogeton malaianus</em> Miq. and complex architecture with finely dissected leaves: <em>Ceratophyllum demersum</em> L. and <em>Myriophyllum verticillatum </em>L.) on zooplanktons. We hypothesized that structurally more complex macrophytes would support more zooplanktons and higher diversity, species richness, abundance and biomass, and to test our hypotheses, zooplankton samples within the above-mentioned macrophytes were collected to analyze the variances at different times. Contrary to our expectations, we found that the zooplankton’ responses were independent to the macrophyte architecture. Specially, although finely dissected<em> M</em>.<em> verticillatum</em> could significantly increase total zooplanktons, diversity, species richness, rotifers and cladocerans than the other three macrophytes, the effects of finely dissected <em>C</em>.<em> demersum</em> on these parameters exhibited no significant differences compared to two broad leaved macrophytes (<em>V</em>.<em> spiralis</em> and <em>P</em>.<em> malaianus</em>). Moreover, broad leaved macrophytes even increased more abundance zooplanktons than finely dissected <em>C</em>.<em> demersum</em>. In addition, the effects of macrophytes on zooplanktons also varied with zooplankton species. For example, the four tested macrophytes could significantly increase cladoceran abundance and biomass. Yet for copepods, the density was significantly increased<em> </em>in presence of <em>V</em>.<em> spiralis</em> and <em>C</em>.<em> demersum</em>, but<em> P</em>.<em> malaianus </em>and<em> M</em>.<em> verticillatum</em> did not show significant effects on copepod density. Moreover, all the tested macrophytes except for <em>V</em>.<em> spiralis</em> even significantly suppress copepod biomass. Therefore, our results did not support the hypothesis that structurally complex macrophytes harbor more zooplanktons, and showed that the effects of the investigated macrophytes on zooplanktons were not likely to depend on their architectures, but seemed to rely on complex relationships between macrophyte and zooplankton species.</p>

Stable carbon isotopic composition of submerged plants living in karst water and its eco-environmental importance

The stable carbon isotopic composition of submerged plants (δ13CP) can be controlled by physiological and environmental factors. Herein, we took advantage of a short, natural karst river with an annual mean bicarbonate (HCO3−) value of 3.8mmolL−1 to study the stable carbon isotopic composition of submerged plants along the river and the influence of environmental conditions on the δ13CP values. The δ13CP values of Ottelia acuminata, Potamogeton wrightii, Vallisneria natans, and Hydrilla verticillata from upstream to downstream show a gradient and ranged from −34.8‰ to −27.8‰, −36.6‰ to −23.7‰, −35.1‰ to −25.3‰, and −38.6‰ to −26.3‰, respectively and even more depleted values for the first two species at the uppermost site. Diurnal variation of water chemistry and concentration of the dissolved inorganic carbon (DIC) and the stable carbon isotopic composition of DIC (δ13CD) indicate that the macrophytes and other primary producers in the river have a very high net photosynthetic rate. The gradient of δ13CP values was consistent with CO2 being a declining source of inorganic carbon for photosynthesis in the downstream transect. The results demonstrate that the high DIC concentration with lower negative δ13C value, particularly in karst water environment has a significant role in controlling the stable carbon isotopic composition of submerged plants living in it.

Combined effects of submerged macrophytes and aquatic animals on the restoration of a eutrophic water body—A case study of Gonghu Bay, Lake Taihu

Submerged macrophytes and filter-feeding aquatic animals have been widely used in ecological engineering to control eutrophic pollution. However, the use of filter-feeding aquatic animals to control eutrophic water bodies remains debatable. As such, more work is needed to understand the combined effects of submerged macrophytes and aquatic animals on the restoration of eutrophic water bodies. In this study, we first conducted a mesocosm experiment to evaluate the combined effects of submerged macrophytes and aquatic animals on water body restoration, and then applied these results in the field. We found that silver carp (Hypophthalmichthys molitrix) deteriorated water quality by increasing nutrient and total suspended solid concentrations, and decreased the biomass of submerged macrophytes. However, triangle sail mussels (Hyriopsis cumingii) promoted the establishment of a clear-water state by grazing on phytoplankton and detritus, and stimulating submerged macrophyte growth. In practical ecological engineering, we suggest that silver carp can be used at low density (20g/m3) as a biomanipulation tool, despite their potential to deteriorate water quality. Furthermore, stocking mussels in nets at a biomass of 150g/m3 can be effectively used to restore eutrophicated water bodies. Finally, Hydrilla verticillata and Potamogeton malaianus, in combination with filter-feeding aquatic animals, are suitable submerged macrophyte species for the restoration of eutrophicated lakes.

Mapping species of submerged aquatic vegetation with multi-seasonal satellite images and considering life history information

Spatial information of the dominant species of submerged aquatic vegetation (SAV) is essential for restoration projects in eutrophic lakes, especially eutrophic Taihu Lake, China. Mapping the distribution of SAV species is very challenging and difficult using only multispectral satellite remote sensing. In this study, we proposed an approach to map the distribution of seven dominant species of SAV in Taihu Lake. Our approach involved information on the life histories of the seven SAV species and eight distribution maps of SAV from February to October. The life history information of the dominant SAV species was summarized from the literature and field surveys. Eight distribution maps of the SAV were extracted from eight 30m HJ-CCD images from February to October in 2013 based on the classification tree models, and the overall classification accuracies for the SAV were greater than 80%. Finally, the spatial distribution of the SAV species in Taihu in 2013 was mapped using multilayer erasing approach. Based on validation, the overall classification accuracy for the seven species was 68.4%, and kappa was 0.6306, which suggests that larger differences in life histories between species can produce higher identification accuracies. The classification results show that Potamogeton malaianus was the most widely distributed species in Taihu Lake, followed by Myriophyllum spicatum, Potamogeton maackianus, Potamogeton crispus, Elodea nuttallii, Ceratophyllum demersum and Vallisneria spiralis. The information is useful for planning shallow-water habitat restoration projects.

Growth and Community Composition of Submerged Macrophytes in Lake Taihu (China): Assessment of Changes in Response to Sediment Characteristics

The aim of this study was to investigate variation in biomass allocation and community composition of submerged macrophytes to elucidate the effect of sediment depth on the growth and species diversity of submerged macrophytes. Field investigations were conducted in 36 sampling sites located across Lake Taihu, China; six plant species were found and communities were dominated by Potamogeton malaianus and Vallisneria natans. The results showed that the plant–sediment distribution relationship was supported by a biological trait (biomass index) and a strong predictive power of sediment depth to plant biomass, and the occurrence selectivity of submerged macrophytes toward relatively firm bottoms could be demonstrated along the eastern shore. Root and stem biomass were strongly positively correlated to sediment depth over a range from 0.1 to 0.25 m (p < 0.01), and approximately 0.25 m could be regarded as an upper limit for depth effect on the growth of submerged macrophytes. The results also demonstrated that species varied in their responses to sediment conditions, which influenced the community composition of submerged macrophytes. The observed pattern suggests the effect of sediment on growth and community composition is an important aspect restricting the restoration of submerged macrophytes.

Responses of Physiological Indices of Typical Submerged Macrophytes to Water Quality in Taihu Lake

It was well known that physiological indices of submerged macrophytes could reflect change of water quality. The correlation between physiological indices of submerged macrophytes and change of water quality was studied under the cooperation of in-situ monitoring and lab analysis, combined with measuring Chlorophyll and free proline (PRO) contents as well as peroxidase (POD) activities in the leaves of Potamogeton wrightii Morong and Potamogeton crispus L. under different water quality and nutrition status. The results showed: ①there were significant spatial differences among water factors and the comprehensive eutrophication index (TLI) of distribution areas of Potamogeton wrightii Morong and Potamogeton crispus L. Mesotrophic water was more suitable for the growth of Potamogeton wrightii Morong, while Potamogeton crispus L. grew well in eutrophic water. ②there were significant spatial differences among physiological indices of Potamogeton wrightii Morong and Potamogeton crispus L. in Taihu Lake. Besides, there were significant relationships between Chlorophyll contents, POD activities of two species and TLI. ③water transparency as well as nitrogen and phosphorus nutrition were important factors leading to changes in Chlorophyll contents and POD activities of Potamogeton wrightii Morong and Potamogeton crispus L.. The findings from this study indicate that physiological properties of Potamogeton wrightii Morong and Potamogeton crispus L. have a very close correlation with nutrition status and physiochemical properties of water.

Stoichiometric characteristics of four submersed macrophytes in three plateau lakes with contrasting trophic statuses

Plant nutrient concentrations and their stoichiometric characteristics are often used to predict nutrient availability and nutrient limitation. However, there is still debate because plants, especially submersed macrophytes, can store excess nutrients and exhibit different survival strategies. To determine the extent to which the trophic status of lakes affect nutrient concentrations of submersed macrophytes and to estimate the relative contribution of lake and interspecific differences to variation of plant nutrient concentrations, we investigated four common submersed macrophytes, Potamogeton maackianus, Potamogeton pectinatus, Potamogeton malaianus and Myriophyllum spicatum, in three plateau lakes with contrasting trophic statuses (i.e. oligotrophic: Fuxian Lake; mesotrophic: Erhai Lake; eutrophic: Dianchi Lake) in Yungui Plateau in southwest China. The results indicated that the average C: N ratios were not different among the three lakes. However, the C: P and N: P ratios in Erhai Lake and Dianchi Lake were significantly lower than those in Fuxian Lake. The N: P ratios of P. maackianus and P. pectinatus did not significantly differ among the lakes. By contrast, the N: P ratios of P. malaianus and M. spicatum indicated different levels of interspecific stoichiometric homeostasis. The C and N concentrations and C: N ratios were mainly determined by the species, while the P concentrations and C: P ratios were mainly determined by the trophic status of lakes. Our study suggested that the C: N: P stoichiometric characteristics of submersed macrophytes exhibit high interspecific differences but substantial homoeostasis in response to different trophic conditions in plateau lakes.

Effects of visible light radiation on macrophyte litter degradation and nutrient release in water samples from a eutrophic shallow lake

ABSTRACTVisible light is a major fraction of the solar spectrum; however, information on visible light radiation of macrophyte detritus is lacking. In this study, we conducted a microcosm experiment to assess the effects of visible light radiation on degradation of two litter species: Potamogeton malaianus (P. malaianus) and Phragmites australis (Ph. australis). This research represents an investigation of mass loss, microbial activity and nutrients released over a period of 168 days. Overall, we found that visible light radiation had significant effects on litter decomposition, but it did not affect the microbial activities which degrade cellulose and lignin. The decomposition rate order of the three components in P. malaianus and Ph. australis in treatments was: cellulose > hemicellulose > lignin. The visible light radiation mainly affected the degradation of lignin, which is the primary compound in litter susceptible to photodegradation. The exposure to visible light radiation up to 17.6 Wm−2 stimulated the dissolved organic carbon release and reduced the molecular weight to less reactive. Meanwhile, no obvious difference in nutrient contents (TP, TN, NO3–N, NO2–N, and NH3–N) was observed among different visible light intensities. The results of this study contribute to better understanding of the photochemical behaviour of macrophyte litter in shallow lakes.

The impact of plant morphology on flow structure: comparative analysis of two types of submerged flexible macrophyte

ABSTRACTThe presence of aquatic vegetation in riverine and lacustrine environments alters the mean and turbulent flow structure and thus impacts the fate and transport of sediment and contaminants. Turbulent flows through Vallisneria natans (V. natans) and Potamogeton malaianus (P. malaianus) were investigated in a laboratory flume. The impact of plant morphology on mean velocity profile and turbulence distribution was analysed and discrepancies in flow alteration caused by different types of macrophyte were highlighted. Results show that a dense canopy of submerged macrophyte leads to a velocity profile featuring a counter velocity gradient in the lower part of the canopy. Negative Reynolds stress and its local maximum were observed there. Discrepancies in flow structure caused by different morphologies of both tested plants were further identified. With smaller frontal area in the lower part of the canopy, P. malaianus causes a much bigger gradient and local maximum in the velocity profile, and thus a larger local stress maximum than V. natans. The mean velocity gradient around the top of canopy, the Reynolds stress and the turbulence kinetic energy at the canopy interface are smaller than for the flow through the V. natans canopy. Larger reduction of the mean velocity within the V. natans canopy makes the suspended sediment of fine particles more easily deposited than in the P. malaianus canopy.

Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves—the latter lack stomata—while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 μM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 μM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10265-016-0844-x) contains supplementary material, which is available to authorized users.

Research on an emergency treatment technology for black-odor water caused by macrophytes decaying

水草腐烂加速水体耗氧和水体还原性物质的溶出进程,在夏、秋季高温条件下极易引发局部水体黑臭.以太湖沉水植物优势种马来眼子菜(Potamogeton malaianus)、苦草(Vallisneria natans)及浮叶植物优势种莕菜(Nymphoides peltatum)为受试材料,利用太湖原位底泥培养模拟水草腐烂形成的黑臭水体,考察不同的环境材料处置方式(壳聚糖(CTS)、聚合氯化铝(PAC)、聚丙烯酰胺(PAM)、CTS+PAC和PAC+PAM)对黑臭水体浊度、溶解氧浓度、挥发性硫化物等黑臭水体特征污染物的絮凝沉降规律及去除机理.结果表明:(1)絮凝处理24 h后,CTS+PAC组合对黑臭水体的浊度去除效果最佳,浊度去除率达70.3%,上覆水溶解氧浓度明显提高,增加率为261.5%;(2)加石英砂悬浊液加速絮体沉淀,形成絮体之后加石英砂使水体浊度稳步下降,4 h之后,浊度去除率达74.9%,显著高于与絮凝剂一起加入的处理组(29.8%);(3)植物腐烂释放的含硫特征嗅味物质主要为硫化氢(H₂S)、甲硫醚和二甲基三硫醚.不同植物体腐烂释放的含硫挥发性有机物浓度差异显著,马来眼子菜释放的4种含硫有机物总和分别为莕菜和苦草释放的319.8%和252.2%;(4)CTS+PAC处理后苦草及马来眼子菜腐烂水体中挥发性有机硫化物浓度较对照组分别降低了18.6%和44.5%.PAC+PAM组合絮凝处理组对莕菜腐烂水体中H₂S有较好的去除效果,去除率达到52.4%.CTS+PAC絮凝剂组合处理的H₂S浓度均低于对照组,苦草、马来眼子菜和莕菜腐烂后黑臭水体中H₂S浓度分别降低了27.4%、41.0%和28.6%.CTS+PAC组合对H₂S和二甲基硫醚类物质等致臭物释放的抑制效果优于PAC+PAM组合絮凝处理.;Aquatic plants decaying will accelerate the process of dissolved oxygen depletion and promote the dissolution of reducing substance, which can easily lead to partial water black-odor in a hot summer. In this study, dominant species of submerged plants Potamogeton malaianus, Vallisneria natans and floating-leaved dominant species Nymphoides peltatum in Lake Taihu were selected as test material. Then the macrophytes decayed in cylindrical sediment in the culture system in which simulated conditions in situ. The black-odor waters were formed to study the flocculation and sedimentation kinetics, removal mechanism of water turbidity, volatile sulfide, dissolved oxygen and other water and soil interface characteristics which were treated with different environmental material disposals(chitosan(CTS), poly aluminum chloride(PAC), polyacrylamide(PAM), CTS+PAC and PAC+PAM). The results suggest that:(1) After 24 h, the turbidity removal of black smelly water treated by CTS+PAC was optimal, when turbidity removal rate was 70.3%. The CTS+PAC combination can increase the dissolved oxygen in overlying water more significantly than other environmental material disposals, and the increase rate is 261.5%.(2) Taking flocculation experiments by joining flocculants in the black smelly water with different flocculants, the suspension of quartz sand was added at different timing. Quartz sand suspension can accelerate flocculant precipitation, adding quartz sand before flocculant is significantly better than after it with turbidity removal rate 74.9% compared to 29.8%.(3) Sulfur characteristic odor compounds released by decay aquatic plants are mainly hydrogen sulfide(H₂S), dimethyl sulfide and dimethyl trisulfide. volatile organic sulfur compounds(VOSCs) released by difference decayed plants was significantly different. The sum of the four forms of organic sulfur released from Potamogeton malaianus were 319.8% of Nymphoides peltatum and 252.2% of biter grass.(4) Volatile organic sulfur compounds contents of Vallisneria natans and Potamogeton malaianus decaying water treated by CTS+PAC was reduced by 18.6% and 44.5%. Treatment PAC+PAM has a good deodorizing effect on Nymphoides peltatum for the removal rate of H₂S reached 52.4% when treatment CTS+PAC affected both three kind of plants. The content of H₂S reduced by 27.4%, 41.0% and 28.6% in Vallisneria natans, Potamogeton malaianus and Nymphoides peltatum, respectively. The inhibitory effect of odorant(such as H₂S and dimethyl sulfide) in treatment CTS+PAC was higher than that in treatment PAC+PAM.

Carbon and nitrogen stable isotopes of macrophytes from Lake Taihu

Nitrogen and carbon stable isotope values can be used to obtain eco-physiological information on macrophytes. This study collected macrophytes at different seasons from Gonghu Bay and Meiliang Bay of Lake Taihu,China to determine the variations of stable isotope values with regard to different season,space and species. The results showed that,with the season,space and species changing,nitrogen and carbon stable isotope values of macrophytes were changed,and the changed values were not obvious with seasonal variation in general,but had certain regularity with the space changes. The nitrogen stable isotopes of Myriophyllum spicatum,Potamogeton malaianus,Vallisneria natans and Eichhornia crassipes in Meiliang Bay were significantly higher than those of Gonghu Bay. The nitrogen stable isotope from emergent plants of Phragmites communis showed higher level in Meiliang Bay than that in Gonghu Bay. However,the carbon stable isotope values of Myriophyllum spicatum and Vallisneria natans in Gonghu Bay were significantly higher than those in Meiliang Bay,others were not significant in the differences. In Gonghu Bay and Meiliang Bay,the carbon stable isotope values of floating plants and emergent plants were lower in Phragmites communis,Eichhornia crassipes and Trapa incise,while Potamogeton maackianus,Ceratophyllum demersum,Potamogeton malaianus,Vallisneria natans,Elodea nuttallii and Myriophyllum spicatum of submerged plants were higher. This might due to the different environments and carbon sources.

The enhanced survival of submerged macrophyte Potamogeton malaianus by sediment microbial fuel cells

Submerged macrophytes can promote the water quality and then facilitate the maintenance of good ecological status in aquatic environments, but have been subjected to severe reduction due to eutrophication. This study investigated the effect of sediment microbial fuel cell (SMFC) on the growth of submerged macrophyte Potamogeton malaianus in degenerated sediments taken from a shallow eutrophic lake. Over 6 weeks, it was found that the growth of P. malaianus was significantly enhanced by both closed-circuit SMFC and open-circuit SMFC in term of survival rate and biomass contents. Survival rate of plants were 103.7% and 107.4% in closed-circuit and open-circuit SMFC treatments respectively, but only 18.5% with only plants without SMFC due to unfavorable environments in sediments. Obvious difference in physicochemical properties of sediments was not observed in the three treatments. However, high-throughput sequencing showed higher abundances of iron-reducing Geobacter, Desulfuromonas and Geothrix in bulk sediments with closed-circuit SMFC, and plant growth-promoting Pandoraea and Methylophilus in sediments with open-circuit SMFC at the end of experiment. These distinct bacterial communities might regulate nutrients/trace metals availability to plants and then make some contribution to plant growth. SMFC employment thus provided an alternative strategy for re-establishment of aquatic macrophytes in sediment-contaminated aquatic environments.

Growth and C/N metabolism of three submersed macrophytes in response to water depths

For submersed macrophytes, carbon (C) and nitrogen (N) metabolism is a central factor affecting growth and survival under low light availability. Three common submersed macrophytes, Vallisneria natans, Potamogeton maackianus, and Potamogeton malaianus, were grown at five water depths (1.0, 2.5, 4.0, 5.5, and 7.0m) to explore mechanism of low light adaptation in terms of C/N metabolism by examining relative growth rate (RGR) and contents of soluble carbohydrate (SC), starch, total carbon (TC), free amino acid (FAA) and total nitrogen (TN) in leaf, stem and root of the plants. With increasing water depth, P. malaianus, P. maackianus and V. natans initiated dying at 4.0m, 5.5m and 7.0m water depths, respectively. V. natans showed higher RGR than the other two species. For all the plants, the FAA contents increased with increasing water depth, except for the roots of P. maackianus. The TN contents showed a unimodal curve along water depths with the highest in moderate water depth, except for P. malaianus and the roots of V. natans. For V. natans and P. maackianus, the C metabolic indices (SC, starch, and TC) showed a unimodal curve along water depths with the lowest in moderate water depth in the leaves and stems, except for TC contents in the leaves of P. maackianus. Compared with P. maackianus and P. malaianus, lower SC and FAA contents and higher starch storage in V. natans contributed to its higher tolerance to deeper depths. The nonlinear changes in metabolite contents along water depths for V. natans and P. maackianus demonstrated complex mechanism for low light adaptation, and thus partly explained the wider ranges of colonizing water depths than P. malaianus.

수로와 강변의 습지에 발생한 수생잡초의 분포 및 방제 현황

수로, 하천, 호수, 강 주변에서 발생하는 수생잡초는 왕성한 생장으로 관개, 배수에서 유속 감소, 수생 생태계에 영향 등으로 막대한 피해를 입히고 수생잡초를 방제하기 위하여 많은 비용을 지출하고 있다. 따라서 본 연구는 수로, 하천, 강 주변 습지와 수중에서 발생하는 수생잡초와 침입식물의 분포 및 방제에 관한 정보를 분석하여 수생잡초의 효과적인 관리대책 수립에 필요한 자료를 제공하고자 하였다. 수로, 저수지, 호수 주변의 수생잡초는 갈대, 나도겨풀, 줄, 망초, 개망초, 소리쟁이, 개기장, 미국가막사리, 부들, 주요 강변의 습지에서는 바랭이, 갈대, 소리쟁이, 쑥, 환삼덩굴, 피, 미국가막사리, 고마리가 우점하였다. 수로 및 호수에서 발생한 침수잡초는 검정말, 나자스말, 대가래, 말즘, 붕어마름, 생이가래, 마름이 우점하였다. 습지에서 외래잡초는 토끼풀, 달맞이꽃, 개망초, 망초, 미국가막사리, 메귀리, 돼지풀, 도꼬마리, 미국개기장, 소리쟁이가 우점하였다. 수생잡초 방제는 기계적, 화학적, 생물적 방법에 의존하고 있으며, 앞으로 우리나라에서 습지에서 수생잡초와 외래잡초를 방제하기 위하여 수생잡초의 주기적인 모니터링과 기계적, 화학적 방제를 포함한 종합잡초관리 체계에 관한 연구가 요망된다. Many irrigated and drainage canals, reservoirs, lakes, and rivers are choked by the explosive growth of aquatic weeds, resulting in enormous direct loss in Korea. Distribution of aquatic weeds and exotic invasive plant species in irrigation and drainage waterways, and riparian wetlands was reviewed to provide basic information for management of aquatic weeds and invasive plant species in wetlands. Dominant emergent weeds in canals, reservoirs and lakes were Phragmites communis, Leersia japonica, Zizania latifolia, Conyza canadensis, C. annuus, Rumex crispus, Panicum dichotomiflorum, Bidens frondosa, and Oenothera odorata. Dominant emergent weeds in wetlands of rivers include Digitaria sanguinalis, P. communis, R. crispus, Artemisia princeps, Humulus japonicus, Echinochloa crusgalli, B. frondosa, and Persicaria thunbergii. In irrigation and drainage canals and lakes, dominant submersed weeds were Hydrilla verticillata, Najas minor, Potamogeton malaianus, P. crispus, Ceratophyllum demersum, Myriophyllum verticillatum, Salvinia natans, and Trapa natans. Dominant exotic weeds in wetlands include Trifolium repens, O. odorata, C. annuus, B. frondosa, Avena fatua, Ambrosia artemisiifolia, X. strumarium, and P. dichotomiflorum. Approaches to aquatic weed control were mechanical, chemical and biological control techniques. Periodic monitoring of aquatic weeds and exotic weeds, and their integrated management studies are needed in waterways and riparian wetlands in Korea.

The distribution of aquatic vegetation in Gonghu Bay, Lake Taihu, 2012

Gonghu Bay is an important drinking water resource area for Wuxi City and Suzhou City. With the rapid deterioration of water quality,cyanobacteria bloom has become progressively worse,which might endanger human healthy through water utilization.In order to provide a theoretical basis for managing water resources of Gonghu Bay,an aquatic vegetation survey was undertaken.Eight transects were set,and boat-based survey was performed. The results indicated: 1) There were 34 species,belonging to 27 genus and 20 families,distributed in Gonghu Bay. Monocotyledons and submerged plants were the dominant taxa and ecotypes,respectively. 2) Grass-dominated state and algal-dominated state were coexisted in Gonghu Bay,as the results of the percentage of aquatic vegetation distribution area to total area was 45. 35%,while the percentage of bare water area to total area was 54. 65%.3) The aquatic vegetation in Gonghu Bay could be divided into 8 community types,and the Potamogeton malaianus community was the biggest in terms of distribution area and biomass. 4) Overall,the distribution pattern of aquatic vegetation in Gonghu Bay illustrated that north area was associated with bare water,east area was dominated by macrophytes,and other areas were taken by macrophytes with low coverage and biomass. The distributions of aquatic macrophytes in Gonghu Bay might have responded to the deterioration of water quality and fishing practice by trap nets. Furthermore,we also speculated that over-excavated dredging wasthe reason that aquatic macrophytes disappeared in north area. The current research suggested that,in order to improve the vegetation growth,aquatic vegetation restoration projects should be carried out in the north and the bay mouth of Gonghu Bay. Meanwhile,water quality monitoring of Yangtze River-Lake Taihu water transfer project should be further strengthened. What's more,invasive plants,especially Cabomba caroliniana,should be effectively monitored.

O2, pH, and Redox Potential Microprofiles around Potamogeton malaianus Measured Using Microsensors

This study aimed to elucidate the effects of periphyton on the microprofiles of oxygen (O2), pH, and oxidation-reduction potential around the stems and leaves of a submerged macrophyte Potamogeton malaianus and on the plant growth in the eutrophic shallow Taihu Lake, China. The microprofiles were measured using a motorized microprofiling system equipped with microsensors. The leaf age of the macrophyte and periphyton exerted significant effects on the microprofiles of O2, pH, and oxidation-reduction potential. O2 concentration and pH increased whereas the oxidation-reduction potential decreased with decreasing distance to the stem/leaf surface. The fluctuation amplitudes of O2, pH, and oxidation-reduction potential were the largest in the microprofiles of mature leaves and the lowest in senescent leaves. The periphyton increased the thickness of the broad diffusive boundary layer and fluctuation amplitudes of O2, pH, and oxidation-reduction potential. When the periphyton was removed, the thickness of the broad diffusive boundary layer in the microprofiles of stems, senescent leaves, and mature leaves reduced by 29.0%, 49.72%, and 70.34%, and the O2, pH, and oxidation-reduction potential fluctuation amplitudes also declined accordingly. Our results suggest that a thick periphyton exerted negative effects on the growth of macrophytes by providing extensive shading and creating a barrier that hindered the transport of dissolved substances such as O2, and led to premature decline in macrophytes in the eutrophic Taihu Lake. The consequent implications can help to elucidate the control mechanism of the broad diffusive boundary layer around macrophytes on nutrient cycling in eutrophic waters and to better understand the role of this layer in the Taihu Lake and other similar eutrophic waters.

Anaerobic digestion of submerged macrophytes: Chemical composition and anaerobic digestibility

Aquatic weeds including submerged macrophyte have been excessively propagated and causing environmental issues in freshwater environment of many countries, and the sustainable treatments have been investigated. In the present study, five submerged macrophyte species dominant in Lake Biwa, Japan, Ceratophyllum demersum, Egeria densa, Elodea nuttallii, Potamogeton maackianus and Potamogeton malaianus were used as a substrate for anaerobic digestion to investigate the chemical composition and the anaerobic digestibility. The lignin content of the submerged macrophyte widely ranged from 3.2 to 20.7%-TS depending on species. The lignin of all macrophytes contained 27.2–59.4% of hydroxycinnamic acids, suggesting they are relatively alkali-labile as compared with woody plants. The total CH4 yield of submerged macrophytes greatly varied from 161.2 to 360.8mLg-VS−1 depending on species. The CH4 conversion efficiency of C. demersum, El. nuttallii, Eg. densa, P. maackianus and P. malaianus was 57.1, 61.4, 60.6, 33.9 and 72.2%, respectively. The results showed that C. demersum, El. nuttallii, Eg. densa and P. malaianus are feasible for anaerobic digestion due to the high methane recovery, whereas P. maackianus was not preferable for anaerobic digestion. The present study revealed that the methane recovery of submerged macrophytes is regulated by the lignin content, as well as other lignocellulosic biomass.

Influence of eco-hydrological factors on aquatic plant succession in a regulated river: a case study of the Petchburi River, Thailand

Monitoring of aquatic plant biomass in the Petchburi River, a regulated river system in Thailand, was carried out together with the examination of eco-hydrological characters and the sedimentary organic content. The surveys were performed during May, August and November of 2010 and 2011. The results indicated temporal variation in water velocity (0.08–2.51 m/s) and medium to low organic levels (0.58–4.68%) of the benthic substrates. Dominant aquatic plants were Hydrilla verticillata (L.F.) Royle and Potamogeton malaianus Miq. with the highest biomass of 70.84 and 182.72 g/m2, respectively. The biomass was substantially decreased during the flood-induced discharge period. This study indicates that Potamogeton has more adaptive potential to high water velocities than Hydrilla, while Hydrilla prefers lower water velocities. Discharge velocities of less than 0.5 m/s could provide positive growth rates of such submerged plants. Approaching the discharge control from this ecological point of view can further contribute to river habitat conservation.