Effect of light and nutrients on interspecific interactions between submerged macrophytes:implications for restoration of multispecies aquatic vegetation in eutrophic lakes

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.

Temporal characteristics of algae-denitrifying bacteria co-occurrence patterns and denitrifier assembly in epiphytic biofilms on submerged macrophytes in Caohai Lake,SW China

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.

Establishing Submersed Macrophytes via Sinking and Colonization of Shoot Fragments Clipped off Manually

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.

Epiphytic bacterial communities on two common submerged macrophytes in Taihu Lake: diversity and host-specificity

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.

Phytoremediation Potential of Three Species of Macrophytes for Nitrate in Contaminated Water

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.

Antioxidant systems of aquatic macrophytes in three life forms:a case study in Lake Erhai,China

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.

SPECIES COMPOSITION AND SEASONAL DENSITY DYNAMICS OF CILIATED PROTOZOA IN BAOAN LAKE WITH PARTICULAR REFERENCE TO THE SUBMERGED MACROPHYTES

From April 1996 to October 1997, regular samplings were carried out monthly at 8 stations in a macrophytic basin of Baoan Lake. From the water samples, 47 genera, 96 species of ciliata were identified. Stations covered with macrophytes had greater number of ciliate species and higher percentage of sessile species. The mixotroph Strombidium viride bearing algal endosymbionts dominated numerically the whole ciliate communities; most of the other dominants were bactivores. Total ciliate density in Lake Baoan was 6170-34310 ind./L. The seasonal density fluctuations of the dominant species populations were also investigated. Maximum abundances were observed in spring and winter during the decay of macrophytes and minimum densities were observed during the summer months of luxuriant macrophytes growth.

STUDY OF THE ECOLOGICAL RESTORATION OF AQUATIC MACROPHYTES IN A EUTROPHIC SHALLOW LAKE

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.

Estimation of Growth Area of Aquatic Macrophytes Expanding Spontaneously in Lake Shinji Using ASTER Data

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.

Phytoremediation Potential of Some Macrophytes from a Car Wash Stream in Buea, South Western Cameroon

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). Ludwigia peruviana 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: Anubias barteri for Cu (7.16), Polygonum persicaria for Zn (14.28), Rorippa nasturtium-aquaticum for Pb (11.60) and Vallisneria spiralis for Cd (1.98). L. peruviana 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). A. barteri had the highest TF (Cu = 1.49, Zn = 1.27, Cd = 1.99) except for Pb where both A. barteri and L. peruviana each had a TF of 1.10. While all the six plants were found to be good accumulators of the heavy metals, L. peruviana showed remarkable efficiency indicating that the species is a good candidate for cleaning such environments.

Polycyclic Aromatic Hydrocarbon (PAHs) Concentrations in Some Aquatic Macrophytes in Hilla River, Iraq

Phragmites australis, Potamogeton pectinatus, Potamogeton perfoliatus and Ceratophyllum demersum were selected to study concentrations of PAHs in lotic ecosystems. Six sampling sites were selected along Al-Hilla River and sampling was conducted in 2010 and 2011. Sixteen PAHs listed as priority pollutants were detected in the samples collected, including Naphthalene (Nap), Acenaphthylene (Acpy), Acenaphthene (Acp), Fluorene (Flu), Phenanthrene (Phen), Anthracene (Ant), Fluoranthene (Flur), Pyrene (Py), Benzo (a) Anthracene (B(a)A), Chrysene (Chry), Benzo (b) Fluoranthene (B(b)F), Benzo (k) Fluoranthene (B(k)F), Benzo (a) Pyrene (B(a)P), Dibenzo (a, h) Anthracene (D(b)A), Benzo (ghi) Perylene (B(ghi)P) and Indeno (1,2,3-cd) Pyrene (Ind). The results of the study illustrate that the PAH concentration in macrophytes varies among their species. These variances were as follows: P. australis 0.425 to 299.424 μg/g dry weight (Dw) for B(ghi)P and B(b)F, respectively;P. perfoliatus 0.354 to 235.84 μg/g Dw for B(b)F and B(ghi)P, respectively;C. demersum 0.996 to 162.942 μg/g Dw for Ant and B(ghi)P, respectively;and P. pectinatus 0.383 to 99.87 μg/g Dw for Ant and Nap, respectively. The accumulation potential of PAHs was also investigated by calculating the Bioconcentration Factor (BCF) and Bio-sediment Accumulation Factor (BSAF). The ranges of BCF ratios were 0.05 to 5334.5, 0.08 to 1602.5, 0.01 to 536.6, 0.16 to 1882 in P. australis, P. perfoliatus, P. pectinatus and C. demersum, respectively. The range of BSAF ratios were 3.14 to 1041.6 and 1.5 to 2920.8 in P. australis and P. perfoliatus, respectively.

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

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

Removal of Heavy Metals by Two Free Floating Aquatic Macrophytes

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

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

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

邛海大型水生植物时空分布及其退化原因

根据2021年7和12月、2022年5和9月邛海水生植物调查结果,结合文献资料,分析了邛海水生植物种类组成、群落结构和空间分布状况以及退化原因,提出了邛海水生植物恢复的对策建议。邛海湖区有水生植物23种,主要分布在水深2 m内,在湖泊北岸成片分布,湖泊西岸和南岸呈斑块状分布,东岸零星分布,总面积约1.3 km^(2)。水生植物分布面积由1990s前占湖面积的20%左右缩减到目前的不足5%,沉水植物群落结构简单化,浮叶植物和挺水植物分布范围扩张。1998年洪水从海河口倒灌,致使高枧湾水域沉水植被消失;近10年来湖泊运行水位抬升和透明度下降使得邛海水生植物分布面积进一步缩小、种群单一化。需要恢复邛海水位运行的自然节律,减少污染负荷输入改善水体透明度,辅之人工生态修复等措施,逐步恢复邛海水生态系统健康。

生态调度控制汉江中游入侵沉水植物过度生长效果研究

针对汉江中游江段入侵沉水植物伊乐藻(Elodea nuttallii)过度生长的问题,以2019年调查监测为基础,采用生物量、分布面积、流速、流量等指标,于2020-2021年在汉江丹江口水库联合王甫洲水利枢纽开展了控制伊乐藻过度生长的生态调度试验并评估其生态效果。结果表明:(1)丹江口−王甫洲区间适宜入侵沉水植物伊乐藻生长的水域面积达16.8 km^(2),主要分布在坝前两岸浅水区、泄水闸上游洲滩、水岸新城、中洲岛、木排港、羊皮滩等区域;(2)生态调度的控制效果显著,伊乐藻生物量和分布面积呈逐年减少趋势,其年度峰值生物量变化与春季萌发期1-3月流量极值比(r=-0.997)和生长旺盛期4−8月平均流量(r=-0.963)的相关系数均大于0.9,与全年平均流量(r=-0.748)和4−8月平均水温(r=0.732)的相关系数大于0.7,流量(流速)和水温是影响伊乐藻生物量的关键因子;(3)根据王甫洲坝前漂浮伊乐藻日打捞量与入库流量统计,可以对伊乐藻成熟团聚体产生明显冲刷影响的王甫洲入库流量(即丹江口水库下泄流量)条件为不小于1500m^(3)/s;丹江口水库峰值流量为3500m^(3)/s的单次汛期调度过程,可减少研究区间内约40%的伊乐藻生物量。

不同功能型沉水植物对溶解氧影响及环境效应

研究选用刺苦草(Vallisneria spinulosa)、黑藻(Hydrilla verticillata)和穗花狐尾藻(Myriophyllum spicatum)分别代表底层型、冠层少根型和冠层多根型沉水植物,通过中宇宙实验,探索不同功能型沉水植物在生长过程中水柱和沉积物中溶解氧(DO)浓度及其相关指标的差异。实验结果表明:不同处理组水柱DO浓度存在显著差异,空白组水柱DO浓度显著低于植物处理组,且空白组水柱总氮(TN)和总磷(TP)浓度降低程度最少;黑藻组比叶面积、叶面积指数、净增长生物量、相对生长速率和水柱DO浓度最大,能够有效降低水柱TP和TN浓度;穗花狐尾藻组株高最高,提升水柱DO浓度显著高于刺苦草,水柱TP降低程度最大;刺苦草组比根长、单株总根长和根冠比最大,提升沉积物深度6 cm以内的DO效果最好,沉积物铁含量最高,沉积物总氮(TN)、总碳(TC)含量和间隙水总溶解性磷(TDP)浓度最低。在修复富营养湖泊过程中,可根据水和沉积物缺氧状况,合理配置底层型和冠层型沉水植物,构建释氧能力较强的群落,从沉积物表层到水柱上层均为湖泊提供充足的氧气,从而更加有利于清水态的形成。

长湖草/藻型湖区浮游植物群落特征及与环境因子的关系

研究长湖草型湖区和藻型湖区浮游植物群落结构特征及其与环境因子的关系,为长湖草型湖泊生态系统的培植、水环境保护和生态修复提供理论支撑。根据长湖形态特征共设5个采样点,于2020年4、7、10月和2021年1月进行采样调查,测定水化学指标并鉴定浮游植物样品,通过对湖泊内草型湖区(水生植物为主)和藻型湖区(水生植物分布较少或无水生植物覆盖)浮游植物群落结构进行对比分析。结果表明,草型湖区和藻型湖区分别鉴定出浮游植物80种和91种,以绿藻门种类数最多,分别为38种和50种。两类湖区均以小球藻属(Chlorella)和小环藻属(Cyclotella)为主要优势属。草型湖区和藻型湖区浮游植物丰度分别为0.59×10^(7)~2.34×10^(7)个/L和0.73×10^(7)~3.06×10^(7)个/L,生物量分别为8.98~18.98 mg/L和10.08~28.25 mg/L。藻型湖区多样性指数略高于草型湖区,两湖区水质整体为轻污染到中污染。冗余分析(RDA)结果显示,草型湖区浮游植物优势种主要受水温、DO、TN、TP和水位影响,藻型湖区主要受DO、TN、氮磷比和水位影响。

衡水湖湿地水生植物生长对水质的影响

为探究衡水湖水生植物生长腐解对湿地水动力水质影响,调查研究衡水湖大型水生植物优势种芦苇(Phragmites australis)、香蒲(Typha latifolia)的生长腐解动力学参数,基于EFDC(Environmental Fluid Dynamics Code)模型构建了衡水湖水动力-水质-水生植物模型,模拟了2018~2022年衡水湖水生植物生长过程和水质变化,定量分析了植物生长对水体水质变化的时空影响及影响机制,并提出适应植物生长过程的衡水湖水质精细化管理保障措施.结果表明,利用植物生长积累量(以C计)表征植物生长腐解动力学相关参数,植物生长期生长系数和腐解期代谢系数分为0.01d^(-1),0.05d^(-1),用于建立衡水湖生态水质模块实现系统模拟研究;有植物生长区较无植物大湖心区在植物生长期对氨氮、总磷浓度降低可达40%~60%,腐解期增加可达60%~80%,且植物对原位及周边500~1000m范围内作用显著;在成熟期(10月)对植物70%茎叶量进行收割,氨氮浓度峰值最大由1.833mg/L降至1.095mg/L,下降率达到40.25%,总磷浓度由0.172mg/L降至0.119mg/L,下降率达到30.78%,年均下降率为25.41%和21.28%,大湖西部滩区氨氮、总磷改善效果明显,且无植物生长的大湖心区域水质也有一定提升.同时,在植物生长期(5~9月),考虑植物生长对水深的要求(芦苇保持-0.3~0.7m、香蒲保持0.24~0.96m),加强水量水位的控制,保障植物生长条件.

云南5个典型高原湖泊沉水植物群落组成及其与环境因子的关系

通过对云南中部5个典型高原湖泊沉水植物和水环境状况进行野外调查,研究该区域主要沉水植物群落组成及其与环境因子的关系,为云南高原湖泊沉水植被保护和管理提供理论参考。综合营养状态指数计算表明,所选取的5个湖泊中,异龙湖、杞麓湖和星云湖属于富营养湖泊,抚仙湖和阳宗海属于贫-中营养湖泊。调查共发现沉水植物6科10属15种,微齿眼子菜(Potamogeton maackianus)和穿叶眼子菜(P.perfoliatus)在贫-中营养湖泊中为主要优势种,穗花狐尾藻(Myriophyllum spicatum)和篦齿眼子菜(P.pectinatus)在各营养类型湖泊中均能成为优势种或亚优势种,轮叶黑藻(Hydrilla verticillata)、菹草(P.crispus)和金鱼藻(Cerato-phyllum demersum)仅在富营养湖泊中成为优势种。沉水植物多样性分析表明,抚仙湖的香农-威纳多样性指数(H')最高,平均值达到1.63;杞麓湖的H'最低,平均值仅0.79,总体来说,贫-中营养湖泊的沉水植物多样性要高于富营养湖泊。沉水植物群落物种与水环境因子的冗余分析(redundancy analysis,RDA)结果显示,透明度(SD)、pH、硝氮(NO_(3)^(-)-N)是影响这些不同营养水平湖泊沉水植物分布特征的关键环境因子,pH、氨氮(NH_(4)^(+)-N)、水温(WT)是影响贫-中营养湖泊沉水植物分布特征的关键环境因子,WT、电导率(SPC)、叶绿素a(Chl-a)是影响富营养湖泊沉水植物分布特征的关键环境因子。研究对于恢复、保护和管理该区域湖泊沉水植物具有重要指导意义。