Floating-leaved Macrophytes Research Articles

Zooplankton assemblage in four temperate shallow waterbodies in association with habitat heterogeneity and alternative states

We assessed the zooplankton assemblages in four temperate shallow waterbodies differing in macrophyte coverage and alternative states: transparent vs. turbid. The main objectives of this study were: (i) to determine the horizontal assemblage of zooplankton in structurally different habitats; (ii) to examine the role of fish, macroinvertebrates and environmental conditions in the observed zooplankton assemblage patterns; and (iii) to evaluate the zooplankton-macroinvertebrate-fish food web interactions in pelagial and littoral zone in transparent vs. turbid lakes. Abiotic factors and food resources, as well as zooplankton assemblage did not show significant difference along the gradient of habitat complexity, but exhibited pronounced variability among these waterbodies. Selected lakes contained nutrient levels that can undergo or were shifted into turbid state. Two waterbodies showed hysteresis: at similar nutrient conditions one remained transparent with macrophytes, while other shifted in its turbid state with increased phytoplankton biomass, and reduced population of planktonic crustaceans. Rotifers contributed mainly to the metazooplankton diversity and abundance. The results suggested that total phosphorous and phytoplankton were the main drivers in turbid waterbodies, and biotic interactions governed structuring of zooplankton assemblage in transparent waterbodies. Habitats of submerged and floating-leaved macrophytes do not appear to a secure refuge for zooplankton against predation. On the other hand, sediment in the vegetated and non-vegetated littoral zone functioned as an effective shelter. According to our results, zooplankton underwent strong predation pressure by macroinvertebrates and small-sized fish in the littoral and by larger-sized fish in pelagial, with alteration related to ecosystem peculiarities. Based on an applied ecological network model, zooplankters were equally vulnerable to predation in both the pelagial and littoral zones, and these biotic interactions were main factors for zooplankton homogenous horizontal distribution. These results suggest that zooplankton organisms play important role in the matter cycling and resilience of the food webs to environmental alterations.

Indicator Values of Emergent Vegetation in Overgrowing Lakes in Relation to Water and Sediment Chemistry

Lake overgrowth is one of the mechanisms affecting the gradual disappearance of lakes in the temperate zone caused by excessive eutrophication of waters. The aim of this study was to assess the possibility of using helophytes as bioindicators of lake overgrowth based on long-term changes based on the cartographic maps studies (1911–2012) and field analyses of plant form growth cover (2012–2014). Additionally, water and sediment chemistry in overgrowing lakes were investigated. The study comprised a total of 33 eutrophic lakes characterized by varying degrees of vegetation development. Based on discriminant analysis, four groups of lakes with diverse degrees of vegetation growth were distinguished. The group comprising the most overgrown water bodies was found to have the greatest percentage of helophytes, with a considerable proportion of submerged and floating-leaved macrophytes. Based on a review of archival materials, lakes which currently exhibit the highest degree of overgrowth were shown to have been affected by intensive littoral growth for over 100 years, which confirms bioindicator properties of helophytes in the assessment of the degree of lake overgrowth. In addition, lakes with the highest rate of overgrowth were characterized by a high content of nitrogen in sediment, with a concurrent high concentration of potassium.

Revisiting the Role of Aquatic Plants in Beaver Habitat Selection

Beaver (Castor canadensis) can help to restore wetlands and mitigate the effects of climate change on hydrological regimes in some areas. Therefore, ongoing resource management efforts seek to promote the presence and persistence of beaver populations. The long-term success of such endeavors requires an understanding of what conditions are conducive to sustaining beaver populations, often in landscapes with degraded forest resources. Available information about beaver habitat suitability is largely based on short-term studies in stream habitats that do not consider aquatic plant suitability, even though aquatic plants may comprise over half of beavers' annual diets. In the present study, we assess whether the availability of woody plants, conditions conducive to the availability of aquatic vascular plants (macrophytes), and/or other features of basin morphology are associated with the persistence and density of beaver occupancy in 23 lakes over a 50-y period. We incorporate field-based study that includes all species of macrophytes, to extend previous work that focused specifically on water lily species (Nymphaea spp., Nuphar spp.). Lake perimeter (a function of sinuosity and surface area) and total macrophyte cover were associated with the persistence and density of beaver occupancy in lakes. Each factor independently explained ∼70% (R2adj) of the variation in the persistence of beaver occupancy. Percent cover of floating-leaved macrophytes was a leading predictor of beaver colony density in lakes, independently explaining 72% (R2adj) of the variation. Brasenia schreberi appeared particularly valuable to sustaining beaver in smaller lakes. Several lakes with abundant Brasenia supported high colony densities and long-term colony occupancy. Where feasible, beaver restoration efforts may increase the probability of success by facilitating beaver access to lakes that host key rhizomatous macrophyte species.

Impact of water level fluctuation in the shaping of zooplankton assemblage in a shallow lake.

Abstract Shallow lakes are strongly affected by global climate changes reflected in significant parameters of ecosystem deterioration, i.e. biodiversity decrease, and water turbidity. Zooplankton research in Škrčev kut oxbow lake (Krapina River watershed, NW Croatia, Europe) was conducted during the summer of 2012 and 2013 with the aim to determine the effect of inter-annual, short-timescale changes of hydrological regime on environmental conditions, macrophytes, zooplankton and fish assemblage within an oxbow lake in the temperate region. Within one-year period the water level increased by 2 meters. This caused a significant reduction of floating-leaved macrophytes (i.e. Nuphar lutea), while turbidity, ortho-phosphate and chlorophyll a concentrations increased. These altered ecological conditions were reflected in the shift from floating-leaved macrophytes at the lower water level to phytoplankton-dominated lake at the higher water level. Zooplankton underwent significant alteration in assemblage. The results suggest that fish preference suppressed cladocerans and enhanced the rotifer and copepod abundance. Our results indicate that even in a short-timescale zooplankton assemblage mediates in the modification of ecosystem functioning.

The use of bdelloids in reference to rotifer biocoenotic indices as an indicator of the ecological state of small field water bodies: The effect of macrophytes, shading and trophic state of water

Species identification of many rotifers is very difficult due to e.g. body contraction in the preserved material. In the case of bdelloids, it is even more problematic as they can only be determined when alive. Therefore, a necessity for developing a method of using the class Bdelloidea for environmental analyses arose, so I examined them as a whole group. This is an approach that reduces extensive, time-consuming and particularly difficult taxonomic identification of certain species. The occurrence of bdelloids against various rotifer community indices in a mosaic of habitats of 220 small water bodies in an agricultural landscape was subjected to both abiotic and biotic factors so as to measure the extent of their reaction and the possibility of their usage in the assessment of environmental conditions. Despite their preference for forest ponds, bdelloids were also a very common and abundant element of field aquatic ecosystems. Due to their specific sensitivity bdelloids serve as a valuable ecological indicator which can be used for environmental assessment of habitat quality in small water bodies in the agricultural landscape and also for monitoring appropriate conservation actions for ponds. Bdelloids are typically macrophyte-associated organisms, selectively choosing Phragmites stands, a transitional area between aquatic and terrestrial ecosystems. Their response to the environment was similar to the littoral fraction and rotifer diversity indices, which were found to be in opposition to the eutrophic community associated with the open water area in large-surfaced fish ponds. Moreover, the increase in bdelloids in ponds of low human impact supports their potential for the diagnosis of natural ponds of low transformation level. Their preference towards ponds with an increasing layer of nymphaeids and pleustophytes also supports their role in diagnosing good-quality waters as floating-leaved macrophytes are known to improve water quality. It is recommended that bdelloids as a group can be used for the determination of the level of heterogeneity (connected with macrophyte occurrence) and the level of shade (generated by macrophyte cover) as well as the water quality state of small water bodies.

挺水植物与浮叶植物光合荧光特性的差异

PDF HTML阅读 XML下载 导出引用 引用提醒 挺水植物与浮叶植物光合荧光特性的差异 DOI: 10.5846/stxb201704120652 作者: 作者单位: 南京大学生命科学学院,南京大学生命科学学院,南京大学生命科学学院,南京大学生命科学学院,南京大学生命科学学院,南京大学生命科学学院,南京大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏省重点研发计划（现代农业项目）（BE2015357）；江苏省林业三新工程项目（LYSX[2015]16）；国家海洋局海洋公益性行业科研专项经费项目（201505023）；国家基础科学人才培养基金项目（J1210026）；中央高校基本科研业务经费项目（020814380026，020814380034） Photosynthetic characteristics differ between emergent and floating-leaved macrophytes Author: Affiliation: Nanjing University,Nanjing University,Nanjing University,Nanjing University,Nanjing University,Nanjing University,Nanjing University Fund Project: Fundamental Research Plan of Jiangsu Province (Modern Agriculture program, BE 2015357), Forestry “San-Xin” project of Jiangsu Province ( LYSX [2015] 16), The State Oceanic Administration of public welfare scientific research funding (201505023), National Undergraduate Innovation Program of China (J1210026), Fundamental Research Funds for the Central Universities (020814380026, 020814380034) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨自然生境中不同生活型水生植物光合生理特征的差异，选取4种挺水植物菖蒲（Acorus calamus L.）、再力花（Thalia dealbata Fraser）、梭鱼草（Pontederia cordata L.）、茭草（Zizania latifolia（Griseb.）Stapf），以及4种浮叶植物黄睡莲（Nymphaea mexicana Zucc.）、莼菜（Brasenia schreberi J.F.Gmel.）、金银莲花（Nymphoides indica（L.）O.Kuntze）、菱（Trapa bispinosa Roxb.）为研究对象，比较其叶绿素荧光参数、色素组成和比叶重的差异。研究发现，高光强下挺水植物电子传递速率（ETR）、非光化学淬灭（NPQ）等光合荧光参数、以及低光强下ETR拟合曲线的初始斜率（α）均值显著大于浮叶植物。不同挺水植物间光系统Ⅱ（PSⅡ）最大光化学效率（Fv/Fm）、ETR、NPQ、最大潜在电子传递速率（Ps）、最大电子传递速率（ETRm）及饱和光强（Em）变化幅度较大；不同浮叶植物间上述参数变化幅度较小。挺水植物叶绿素（Chls）、类胡萝卜素（Cars）含量均值也高于浮叶植物。但由于比叶重（SLW）的影响，不同水生植物间单位叶面积和单位叶鲜重色素含量的变化规律略有不同。挺水植物中再力花、梭鱼草光合能力较强，其光合荧光参数和色素比例均符合典型阳生型特征；菖蒲、茭草光合能力略弱，部分指标符合阴生型特征。4种浮叶植物各指标均符合阳生型特征。实验推测，挺水植物和浮叶植物由于叶片所处环境不同，其光合适应机制存在明显分化。挺水植物叶片所处环境异质性较大，因而不同物种之间光合参数适应范围也大；浮叶植物叶片所处环境相对均一，因而光合参数差异也小。浮叶植物也不依赖NPQ进行高光保护。在湿地植被恢复工具种筛选过程中应综合考虑环境异质性和不同物种光适应能力的差异。 Abstract:Emergent and floating-leaved macrophytes, two different life forms of primary producers in shallow lakes and riparian zones, play important roles in nutrient cycling and energy flow of aquatic ecosystems. To investigate the differences in photosynthetic characteristics between the two forms of macrophytes, chlorophyll fluorescence, pigment composition, and special leaf weight (SLW) of four emergent macrophytes (Acorus calamus L., Pontederia cordata L., Thalia dealbata Fraser, Zizania latifolia (Griseb.) Stapf) and four floating-leaved macrophytes (Nymphaea mexicana Zucc., Brasenia schreberi J. F. Gmel., Nymphoides indica (L.) O. Kuntze, Trapa bispinosa Roxb.) growing in natural habitats were compared. In general, emergent macrophytes showed higher electron transport rate (ETR) and non-photochemical quenching (NPQ) under high irradiation, as well as relatively higher initial slope (α) of ETR curve under low light, than did floating-leaved plants. Broader ranges on maximum quantum yield of PSⅡ (Fv/Fm), ETR, NPQ, maximum potential ETR (Ps), maximum ETR (ETRm) and saturating irradiance (Em) were also found among different species of emergent macrophytes. Average chlorophyll (Chls) and carotenoid (Cars) contents were also higher in emergent macrophytes than in floating-leaved ones. However, due to the discrepancy of SLW, the trends of pigment amount among species on a fresh matter basis differed from those per leaf area unit. Among the four emergent macrophytes, T. dealbata and P. cordata exhibited relatively higher photosynthetic ability, and all fluorescence parameters together with pigment ratios (Chl a/b, Chls/Cars) indicated they belonged to the sun type. However, A. calamus and Z. latifolia exhibited relatively lower photosynthetic ability, and part of the parameters were closer to the shade type. All four floating-leaved species exhibited as sun type. This suggests that the heterogeneity of environments contributes to the discrepancy of leaf photosynthetic abilities. Emergent leaves grow in highly diverse environments, so their photosynthetic parameters have broad ranges, whereas the environments for floating leaves are relatively stable, so their parameters are limited to small ranges. It may not be necessary for floating-leaved macrophytes to develop NPQ and internal heat dissipation to prevent high irradiation damage. In conclusion, special attention should be paid to both environmental heterogeneity and discrepancy of adaptation abilities when selecting aquatic macrophytes for wetland restoration. 参考文献 相似文献 引证文献

Disentangling food webs interactions in the littoral of temperate shallow lakes

Elucidation of food web interactions provides better understanding of ecosystem functioning, indicates anthropogenic impacts which often cause alterations in environmental conditions and detoriorations in feeding network in terrestrial and aquatic ecosystems. The importance of microfauna and macroinvertebrates in littoral zones of shallow waters has poorly been studied regarding their trophic interactions. This study compares invertebrate assemblage and food web interactions among epiphyton, zooplankton and benthic macroinvertebrates across structural heterogeneity in the littoral zone of three temperate shallow water bodies. Submerged and structurally-complex stands of Ceratophyllum demersum inhabited higher abundance of cladocerans and supported higher diversity and biomass of epiphytic protozoans and invertebrates in comparison to floating-leaved Nuphar lutea stands. Analysis of the ecosystem functioning illustrated the increased biomass of macroinvertebrate predators and a preference of predation over planktonic crustaceans in more complex macrophyte stands. Food webs displayed higher complexity and size with habitat heterogeneity, while epiphyton and zooplankton shared the important fraction in food resources among the invertebrate trophic network. Results of food web modelling indicated zooplankton and epiphyton as more vulnerable to invertebrate predation in the complex submerged macrophytes than in floating-leaved macrophyte stands. Integrated community, ecosystem and food web approaches in explanation of complex trophic interactions in the littoral zones justified an increase in diversity and food-web functional complexity with structural heterogeneity of microhabitats.

Spatial heterogeneity in induced defense of Brachionus calyciflorus within a single lake caused by a bed of floating-leaved macrophyte Trapa species

While induced defense of aquatic organisms against predators has been considerably studied by both laboratory and field research, our understanding is still limited about, for example, whether induced defense is variable between microhabitats within the same lake and how multiple predators influence induced defense in the natural environment. Here, we examined whether a rotifer species, Brachionus calyciflorus showed a different development degree of induced defenses against its predator Asplanchna and cyclopoid copepods between the microhabitats of a macrophyte bed consisting of Trapa species and open water. B. calyciflorus was more abundant and had larger posterolateral spines as a defensive trait in open water than in the Trapa bed. Asplanchna was more abundant in open water than in the Trapa bed, whereas cyclopoids were more abundant in the Trapa bed. Both of the predators significantly affected the development of the defense trait. The effect of Asplanchna on the defense trait was positive, whereas the effect of cyclopoids was negative. Thus, a spatial difference in the development degree of induced defense between the microhabitats occurred as the dense Trapa bed influenced the abundance of the two predators. The results also suggest that the induced defense of B. calyciflorus was effective in reducing the predation pressure from Asplanchna while B. calyciflorus was not able to avoid predation by cyclopoids in the Trapa bed.

Submerged seed, turion and oospore rain: A trap quantifying propagule deposition under aquatic vegetation

Submerged, free-floating and floating-leaved macrophytes produce a broad variety of specialized propagules to ensure population continuity and enhance dispersal. We quantified macrophyte propagule deposition in shallow ponds using a trap positioned near the sediment, designed to monitor diaspore rain in lentic aquatic environments. Propagule traps were tested under different set-ups, firstly within enclosed mesocosm experiments and secondly in vegetation communities growing in the open field. Mesocosms were installed in ponds containing monospecific stands of Chara globularis and Potamogeton pusillus under two contrasting conditions, with and without duckweed (Lemna minor), to evaluate cover impact on propagule release from the submerged macrophytes. During the studied interval, deposition of C. globularis oospores was not affected by Lemna cover. In P. pusillus, lemnid cover coincided with strong phenotypic alterations, including high turion investment. Traps openly installed in ponds containing Parvopotamion- and Magnopotamion/Hydrocharition-type associations showed that propagule rain was intensive underneath some macrophyte species and generally mirrored vegetation composition. Certain species were either over- or underrepresented. Generally, macrophyte abundance did not influence propagule deposition. Propagule traps are useful in studies assessing reproductive dynamics and resource allocation, potentially bypassing or complementing sediment propagule bank research, and aiding identification of recruitment bottlenecks.

Floating Aquatic Macrophytes Decrease the Methane Concentration in the Water Column of a Tropical Coastal Lagoon: Implications for Methane Oxidation and Emission

ABSTRACT In wetlands, the knowledge accumulated on the role of aquatic plants in the methane cycle focused on emergent macrophytes, to the detriment of other typologies. Herein, we evaluated whether the free-floating macrophyte Salvinia auriculata Aubl. and the floating-leaved macrophyte Eichhornia azurea (Sw.) Kunth. decrease the water column methane concentrations compared to a plant-free surface. We prepared microcosms by inserting an individual of S. auriculata or of E. azurea into chambers filled with lagoon water previously bubbled with CH4. Another set of chambers was incubated only with the prepared water, representing the plant-free surface. Half of the chambers were kept in the dark and half in sunlight to simulate a diel cycle. We observed greater loss of CH4, higher O2 uptake and lower CO2 outflow in the plants treatments. The decrease in methane concentrations in the E. azurea treatments was 93.5% in the light and 77.2% in the dark. In the S. auriculata treatments, the decreases were 74.2% and 67.4% in the light and in the dark, respectively. In plant-free surface the decrease was 58.7% in the light and 36.3% in the dark. These results indicate a role of floating aquatic macrophytes in the methane cycle in the water column. Moreover, our results suggest a diel variation of methane oxidation and methane emission, according to the differences observed in O2 uptake and CO2 outflow between dark and light conditions. Thus, future predictions of global methane budget should include the role played by floating aquatic macrophytes.

Effects of sediment-borne nutrient and litter quality on macrophyte decomposition and nutrient release

Macrophyte decomposition is a critical process that affects carbon and nutrient cycling, and energy flow, although the majority of the details involved in the process remain unclear. For the present study, a litter bag experiment was conducted to investigate the effects of sediment-borne nutrient and litter quality on the decomposition rates and nutrient release of four macrophyte life forms (emergent macrophyte: Phragmites australis, free-floating macrophyte: Hydrocharis dubia, floating-leaved macrophyte: Nymphoides peltata, submerged macrophyte: Ceratophyllum demersum), and a species mixture. Our results indicated that litter quality significantly influenced macrophyte decomposition and nutrient release. High-quality litter species (high initial nitrogen and phosphorus contents, as well as low C:N, C:P, and N:P ratios) decomposed more rapidly than low-quality litter species, and the initial C:N and C:P ratios, rather than the initial N and P contents, were effective indicators of the decomposition rate of macrophytes. Sediment-borne nutrients had little effect on the decomposition rate, yet a strong effect on the release of N and P, although the interactions between litter quality and sediment-borne nutrients significantly affected the decomposition rate. Three-way ANOVA analysis revealed that the litter quality imparted a more potent effect on the macrophyte decomposition rate and release of N and P than sediment-borne nutrients. These results implied that litter quality interacts with sediment-borne nutrients and may control macrophyte decomposition in shallow lakes.

Effects of floating-leaved macrophytes on water quality and phytoplankton: an in situ experiment in a Chinese shallow lake

In this study, in situ experiments were conducted to evaluate the effects of floating-leaved macrophytes (FLMs, i.e. Trapa uncinata and Nymphaea tetragona) on water quality and algal growth and to investigate the potential inhibition of phytoplankton growth by FLMs. Enclosures were established in a shallow subtropical eutrophic lake, and FLMs were planted therein. Open water areas in the enclosure with FLMs, an enclosure without FLMs, and the lake water surrounding the enclosures served as the control groups. Physical parameters, nutrient contents, and algae were evaluated for six sampling sites at 10-d intervals. Treatment with FLMs significantly promoted water transparency and reduced turbidity. However, the concentrations of nutrients were similar in the different sites, despite the nutrient absorption by FLMs. The overall algal abundance was reduced in the presence of FLMs, and this was shown in chlorophyll-a, algal density, and biomass. FLM treatments promoted changes in the algal community composition, benefitting metaphytic species adapted to higher transparency. A principal components analysis showed that algal attributes were higher in the control areas than in the FLM-covered areas, despite the similar nutrient concentrations. This indicated that the inhibition of algae in this study was based not on nutrient competition but instead on the shading effect. Using FLMs as a management tool to create a clear water state may be one solution for turbid waters in subtropical eutrophic shallow lakes.

Proposal of a typology of Spanish mountain lakes and ponds using the composition of functional groups of macrophytes

Before establishing the ecological status of lakes, the Water Framework Directive requires their classification in types. Typically, the development of a typology has been based on abiotic variables. However, for the typology to have validity, the classification of lakes should be corroborated with the biological communities in the bodies of water. In this study, to develop a biologically relevant typology, the natural variability of the macrophyte communities in mountain lakes and ponds was evaluated. The use of functional groups of macrophytes as an alternative to the taxonomic approach was also evaluated. Thirty-one reference mountain lakes and ponds, located in the northwest quadrant of the Iberian Peninsula, were included in the study. The functional groups of macrophytes were based on the inorganic source of carbon used in photosynthesis. The typology developed from the functional groups was more conclusive than the classification derived from the taxonomic data. The primary determinants of the variability in the composition of the functional groups of macrophytes among the different types of lakes were the changes in the pH and in the orthophosphate concentration related to the decomposition of macrophytes. The submerged macrophytes dominated in the lakes with low concentrations of orthophosphate and the highest levels of alkalinity. In the lakes with lower pH values, the floating-leaved macrophytes were the dominant plants when the phosphorus concentration was higher, whereas at intermediate concentrations of phosphorus, the bryophytes and isoetids were more abundant; these two lake types were differentiated because of the dominance of the bryophytes in those lakes with higher acidity.

Zoobenthos are minor dietary components of small omnivorous fishes in a shallow eutrophic lake

We examined whether small omnivorous fishes (smaller than ~100mm long) integrate littoral, pelagic and benthic pathways in a shallow, eutrophic lake (Lake Izunuma, Japan). The surface of the lake was covered by a dense vegetation of floating-leaved macrophytes, and small species dominated the icthyofauna. We determined the δ13C and δ15N ratios of five dominant species of small omnivorous fishes. Using a stable isotope analysis in the R mixing model, we determined the possible contribution of three potential food sources (epiphytic algae, zooplankton and zoobenthos (larval chironomids)) to omnivorous fish tissue compositions. Four omnivorous fishes (Gnathopogon elongatus elongatus, Pseudorasbora parva, Biwia zezera and Tridentiger obscurus) subsisted largely on epiphytic algae and zooplankton, whereas zoobenthos contributed little to their diets. Acheilognathus rhombeus subsisted mostly on epiphytic algae. Thus, in this shallow, eutrophic lake, omnivorous fishes incorporated both littoral and pelagic production into the food web, but rarely benthic production. The dominant benthic chironomid larvae often burrow several centimetres into the sediment, and the low dietary contribution of zoobenthos to small fishes may be due to inefficiency at foraging on buried benthos associated with fish body size.

Seasonal changes in the water bird community in Lake Inba: Influence of floating-leaved macrophytes on habitat selection

The abundance of the floating-leaved macrophytes, especially Trapa spp., has increased in many eutrophic lakes, butits effects on waterbirds is not clear. By covering the water surface with their floating-leaves, these macrophytes exert effects that differ from those of submerged macrophytes. In this study, we investigated seasonal changes in the species composition and habitat selection of the waterbird community in the shallow, eutrophic Lake Inba in relation to the presence/absence of native floating-leaved macrophytes (Trapa spp.). The results indicated higher abundances of the eastern spot-billed duck (Anas zonorhyncha), the little grebe (Tachybaptus ruficollis), the great egret (Egretta alba), theintermediate egret (Egretta intermedia), and the Eurasian coot (Fulica atra) in Trapa beds, whereas the great cormorant Phalacrocorax carbo was more abundant in the open water without macrophytes. Both great egrets and intermediate egrets seemed to actively choose the Trapa beds as a feeding habitat that allowed them to catch the small fish swimming beneath these plants. Eurasian coots utilized Trapa spp. as food directly, by grazing on its fruits and leaves. Little grebes selected Trapa beds for nesting, especially when their flock size was larger. Conversely, Trapa beds prevented the foraging behavior of great cormorants. In Lake Inba, with its suddenly deep shoreline and lack of shallow areas, there are few potential feeding habitats for waterbirds in the littoral zones. Therefore, Trapa beds might provide an alternative habitat for these species, thus serving as an important ecotone between terrestrial and aquatic ecosystems.

Clonal integration in Ludwigia hexapetala under different light regimes

Physiological integration among ramets of invasive plant species may support their colonization and spread in novel aquatic environments where growth-limiting resources are spatially heterogeneous. Under contrasting light conditions, we investigated how clonal integration influences growth, biomass allocation and morphology of Ludwigia hexapetala, an emergent floating-leaved macrophyte that is highly invasive in a range of wetland habitat types. In aquatic mesocosms, stolons of offspring ramets were either connected or severed from parent plants, with the pairs exposed to homogenous or heterogeneous combinations of sun or 85% shade. Morphological traits of all ramets were strongly influenced by light environment, and low light availability decreased plant growth, regardless of integration status. Allocation patterns varied with light regime; shaded plants increased allocation to leaf biomass while sun plants allocated more resources to belowground growth. Offspring ramets integrated with parents produced more biomass, suggesting a fitness advantage through integration. However, parent ramet performance declined with stoloniferous integration; integrated parents produced fewer ramets and allocated more resources to belowground biomass. For most response variables measured, there was no significant interactive effect between light treatment and integration, although parents growing in the shade attached to an offspring in the sun increased root mass ratio. The ability to establish and spread into new environments is a key trait of invasive plants, and physiological integration of resources may improve the establishment of juvenile ramets across variable light environments during early colonization. Physiological integration in patchy light environments may contribute to the invasiveness of L. hexapetala.

Characteristics and influence to overlying water of amino acids from typical plants distributed in Lake Taihu, China

The concentrations of total hydrolyzable amino acids( THAAs) were investigated in 8 kinds of typical plants of both East Lake Taihu and Gonghu Bay,in order to find the links and differences of composition of THAAs in the typical plants,sediments and water as well as the composition of THAAs in different typical plants of Lake Taihu. The form and composition of 15 kinds of THAAs in 18 samples were analyzed by o-phthalaldehyde pre-column derivatization-RP-HPLC. The average concentration of THAAs in typical plants of East Lake Taihu was 861. 6 ± 182. 96 μmol / g. The average concentration in typical plants of Gonghu Bay was 700. 0 ± 232. 3 μmol / g. The comparison of the concentrations of THAAs in different kinds of plants showed submerged macrophytes and floating-leaved macrophytes had the highest concentration of THAAs,followed by emerged macrophytes and terrestrial plants. The dominating amino acids were Asparagine,Glutamic acid,Arginine,Alanine and Lysine,which accounted for more than 50% of concentration of THAAs. About 30. 7%-94. 7% of the N in plants were from THAAs,which was an important source of N in plants. Meanwhile,in comparison with the composition of THAAs in sediments and water in Lake Taihu,the typical plants generally aligned with sediments but different from the water. It showed that THAAs in plant may be an important source of the THAAS in sediments.

Dynamics of dissolved nutrients among different macrophyte stands in a shallow lake

Seasonally changing mechanisms affect the concentrations of dissolved inorganic nitrogen and soluble reactive phosphorus, which differ between the stands of different macrophyte life forms and open water in a eutrophic lake. Macrophytes that take nutrients up for their growth also shelter sediments from resuspension that brings nutrients back to the water and affect denitrification, which removes nitrogen from the water ecosystem. In this study the changes in nutrient concentrations were observed during the open-water period from April to November, and also denitrification rates were measured at different phases of the open-water season. The study was conducted at a shallow eutrophic lake where the effect of macrophytes on water quality is remarkable. The concentration changes of different nitrogen forms during the summer were very similar at the open-water and floating-leaved macrophyte (Nuphar lutea L.) stations. Nitrate was depleted faster among the submerged macrophytes (Myriophyllum verticillatum L.) than among floating-leaved plants or in open water. The decrease in the concentration of nitrate was so significant during the summer that it also affected the total nitrogen concentration in the water. Denitrification was highest in sediments among floating-leaved macrophytes (average 4.3 mg N m−2 d−1) and lowest in sediments of submerged plants (average 1.5 mg N m−2 d−1). Denitrification among submerged macrophytes was limited by low nitrate availability.

Distinguishing surface cyanobacterial blooms and aquatic macrophytes using Landsat/TM and ETM + shortwave infrared bands

Satellite remote sensing can be considered a suitable approach to monitor the extent of cyanobacterial blooms compared with conventional ship surveys because of the patchiness and high spatial and temporal variability of the blooms. However, most of the existing algorithms are not capable of distinguishing cyanobacterial blooms and aquatic macrophytes due to their similar spectral characteristics in the red and near infrared (NIR) wavelengths. In this study, we conducted in situ spectral measurements and satellite data analyses for cyanobacterial blooms and aquatic macrophytes to find an effective method to distinguish them using medium-resolution Landsat satellite images. The reflectance spectra were measured for lake waters and cyanobacterial blooms with 13 different chlorophyll-a concentration levels (from 54 to 21,736μgL−1) and four types of aquatic macrophytes (two emerged and two floating-leaved macrophytes) in the wavelength range from 350 to 2500nm. In addition, seven Landsat images were collected for nine lakes in Japan or Indonesia. We calculated several selected indices, i.e., the normalized difference vegetation index (NDVI), five types of normalized difference water index (NDWI), and the floating algal index (FAI) to find an appropriate index for distinguishing cyanobacterial blooms and aquatic macrophytes.The results showed that the spectral characteristics of cyanobacterial blooms were significantly different from those of aquatic macrophytes in the short-wave infrared (SWIR) region, indicating that the SWIR bands are important for distinguishing cyanobacterial blooms and aquatic macrophytes. The results also showed that the combination of FAI and NDWI4,5 was an effective method for classifying lake areas. We first used the FAI for extracting lake waters, and we then used the NDWI4,5 to classify the remaining areas as cyanobacterial blooms or aquatic macrophytes. The results also showed that the threshold of NDWI4,5 was less sensitive to the effects of both the atmosphere and mixed pixels compared to the other indices. Our application of the FAI threshold of 0.05 and the NDWI4,5 threshold of 0.63 to six lakes in Japan and Indonesia showed that the proposed method could successfully distinguish lake water, cyanobacterial blooms, and aquatic macrophytes.

Photosynthetic response of the floating-leaved macrophyteNymphoides peltatato a temporary terrestrial habitat and its implications for ecological recovery of Lakeside zones

For the ecological recovery of lakeside zones in shallow eutrophic lakes, choosing suitable aquatic macrophytes which could adapt to the temporary terrestrial habitat due to water level change is very important. In the present study, an experimental approach was carried out to explore the photosynthetic response of the typical floating-leaved aquatic plant Nymphoides peltata (N. peltata ) to varying environmental factors. N . peltata grown under aquatic and terrestrial habitats showed similar photosynthesis-irradiance response patterns. The investigation of diurnal changes in gas exchange revealed that the net photosynthetic rate (P N ) and water-use efficiency (WUE) of the N . peltata grown in the terrestrial habitat were 68% and 94% higher, respectively, than those in the aquatic habitat at nine in the morning. N . peltata grown in the terrestrial habitat had approximately 51% less stomatal density and a 77% smaller stomatal aperture area compared with those grown in aquatic habitats. The above results indicated that N . peltata could be well-acclimated to the terrestrial habitat by developing a series of photosynthetic acclimation features. Our study may provide an important reference for restoration in lakeside zones of shallow eutrophic lakes.