沉水植物苦草(Vallisneria natans)对多环芳烃污染沉积物的修复作用

沉水植物是浅水湖泊生态系统的关键种群,对水环境质量及水生生态系统结构有重要影响.以东太湖大水港和湖湾区2个典型的具有不同污染程度的沉水植物苦草(Vallisneria natans)生长区域为研究对象,考察苦草对多环芳烃(PAHs)的修复效果.结果表明,经过34 d植物修复试验,重度污染的东太湖大水港沉积物中PAHs的去除率为62%,沉积物中PAHs降解速率为0.024 d-1;而中度污染的东太湖湖湾区沉积物的PAHs去除率为42%,其降解速率为0.015 d~(-1).种植苦草的沉积物中PAHs的降解速率是未种植苦草的降解速率的2~3倍.苦草对沉积物中高分子量PAHs的修复效果尤为显著.因此,苦草可以有效地用于PAHs污染沉积物的修复,尤其是在重污染和高分子量PAHs污染沉积物中,苦草的修复作用更加明显.     

太湖草/藻型湖区沉积物-水界面环境特征差异

在太湖草、藻型湖区进行冬、夏两季多点采样,分别对采样点的水环境特征、泥面以上5 cm上覆水中营养盐以及沉积物的含水量、中值粒径、有机碳、氮、磷、金属元素和溶解氧进行测定.结果表明:夏季藻型湖区表层水体pH高于中、底层,冬季草型湖区各层水体pH高于藻型;草型湖区水体浊度夏季低于藻型,冬季反之;藻型湖区上覆水中的硝态氮和磷酸根浓度显著高于草型;草型湖区沉积物中含水量冬季显著高于夏季;草型湖区沉积物中总有机碳显著高于藻型;Fe、Zn、Ca、Pb、Na和K等元素在草、藻型湖区间差异显著;沉积物中溶解氧表现为冬季深于夏季,藻型深于草型的规律.     

Optimizing environmental flow and macrophyte management for restoring a large eutrophic lake-marsh system

With increasing environmental degradation from eutrophication, management strategies associated with eutrophic water restoration initiatives are necessary and have garnered wide interest. Macrophytes contribute to water quality improvement in lake-marsh systems through nutrient uptake, while causing considerable water loss through transpiration. In reverse, hydrological variations affect macrophyte growth status and thus phytoremediation performance. The interactions between hydrological and ecological processes in lake-marsh systems are complex, but environmental flow management strategies accounting for these interactions have been rarely proposed. Accordingly, this study combines environmental flow and macrophyte management in the restoration of a large eutrophic lake-marsh system, accounting for interactions between hydrological and nutrient removal processes. We consider both nutrient uptake and transpiration-driven water loss of macrophytes as well as the impacts of hydrological conditions on macrophyte growth status and sediment biological denitrification. Regulating upstream dam operation is an effective measure for environmental flow management. Thus, we develop an optimization model to guide upstream water release while simultaneously regulating macrophyte area in a lake-marsh system, aiming to minimize the ratio of environmental flow demand to reservoir water availability and maintain satisfactory water quality in the system throughout the year. A genetic algorithm is adopted for solving the optimization model. By applying the method in a typical lake-marsh system (Baiyangdian) in China as a case, we introduce a new macrophyte management regime (for area cover and harvesting regimes) and an optimal environmental flow management schedule. Results show that appropriate monthly fluctuations in wetland water level are beneficial to phytoremediation performance, and harvesting macrophytes in stages is effective in reducing transpiration-driven water loss without inordinately damaging nutrient uptake by macrophytes. This study offers a useful tool for lake-marsh system restoration management and highlights the significance of regulating hydrological processes in water quality restoration.     

水位波动的幅度与频率对刺苦草(Vallisneria spinulosa)生物量和形态特征的影响

沉水植物是维持浅水湖泊清水稳态以及湖泊生态系统结构与功能的关键生物类群.近年来,气候变化和人类活动的双重作用造成湖泊水文情势的明显改变,对沉水植物的生长、繁殖和演替有着较大的影响.本文选取2个水位波动幅度与2个波动频率(逐渐改变水位),以恒定水位作为对照,研究湿地中具有重要生态功能的沉水植物刺苦草(Vallisneria spinulosa)的生物量及地上和地下营养器官形态结构对水位波动的响应.结果表明,相对于恒定水位,波动水位(低幅度低频率、低幅度高频率、高幅度低频率、高幅度高频率)对刺苦草的总生物量和获取限制资源相关器官有显著影响.相比于对照组,水位波动能够显著降低刺苦草分株数、叶片数、根数、根长、匍匐茎数、总匍匐茎长以及叶、根、地上和地下生物量,但会显著增加其株高和比叶面积.不同波动频率(低频率和高频率)和幅度(低幅度和高幅度)对光合器官的形态特征都没有显著影响,但叶和地上部分的生物量积累均受到波动幅度的显著影响.水位波动幅度显著改变了刺苦草的根数和根长,而波动频率的影响不显著.因此,对浅水湖泊受损刺苦草群落进行重建时,应避免较大幅度的水位波动,从而有利于增强植株快速恢复的能力.     

中国苦草属(Vallisneria)植物萌发与生长的影响因素

由于人类生产生活对众多淡水水体的扰动、污染,我国苦草属(Vallisneria)植物的种群规模出现了严重的退化.明确苦草属植物萌发和生长的影响因素,阐明苦草属植物退化的原因,是保护和恢复该属植物亟需解决的科学问题.通过对已发表的文献进行收集和分析,总结了影响苦草属植物萌发和生长的主要因素,并通过挖掘文献中的数据,对重要环境因子与苦草属植物萌发和生长参数的关系进行了分析.结果表明:(1)涉及苦草(V.natans(Lour.) Hara)的研究较多,而涉及刺苦草(V.spinulosa Yan)和密刺苦草(V.denseserrulata Makino)的研究较少;(2)苦草属植物种子的萌发受到温度、光照强度、水深、掩埋深度、基质情况和储存方式等因素的影响;(3)苦草属植物生长受到光照强度、水深、水体营养水平、底泥营养水平、底泥有机质和动物牧食等因素的影响;(4)其他条件适宜时,苦草和刺苦草种子在20～30℃都保持较高的萌发率(均值 50%);(5)苦草种子萌发率随着掩埋深度的增加而快速下降;(6)苦草的相对生长率随光照强度的增加而升高,随水深增加而下降;(7)苦草的相对生长率随着氨氮浓度增加而下降;(8)水体和底泥中高含量的总氮和总磷对苦草属植物生长的抑制作用主要是通过促进浮游植物和附着藻生长导致的遮光,而不是直接毒害作用.未来需要进一步加强苦草属植物萌发、生长参数与环境因子关系的定量研究,更好地服务于该属植物的保护和恢复.     

Influence of environmental parameters on the biomass development ofRuppia drepanensis populations in Doñana National Park: the importance of conditions affecting the underwater light climate

The development of submerged plant communities dominated byRuppia drepanensis Tineo in the brackish marsh of the Doñana National Park (SW Spain) was coupled to seasonal variation in environmental factors for two consecutive years. Plant biomass increased rapidly in early spring (March), with steady biomass yields (up to 100 g afdw m^–2) together with abundant flowering and fruiting in late spring (April–May). Wind-induced sediment resuspension and periphyton growth strongly influenced the light climate experienced by the submerged vegetation, while a phytoplankton effect was generally negligible. Development of the submerged vegetation coincided with a decrease in water extinction coefficient and in bicarbonate concentration. Thus, where dense macrophyte meadows develop, light climate probably is the limiting factor in the early spring, while temperature and bicarbonate levels are so by the end of the season. Interannual variation was found to be very high, both in abundance and distribution of the submerged vegetation, mainly because of differences in rainfall which influenced the inundation cycle. Grazing by waterfowl accounted also for this effect, as in dry years birds concentrate in the few wetlands still containing water.     

Mechanisms for Organic Matter and Phosphorus Burial in Sedimentsof a Shallow, Subtropical, Macrophyte-Dominated Lake

We studied the role that submersed aquatic vegetation (SAV) plays in the sedimentation of organic matter (OM) and phosphorus (P) in Lake Panasoffkee, Florida (USA), a shallow, hard-water, macrophyte-dominated water body. Carbon/Nitrogen ratios (C/N) and stable isotope signatures (δ¹³C and δ¹⁵N) in algae, higher plants, and surface sediments were measured to identify sources of OM to the lake mud. Pollen, plant macrofossils, and geochemistry in sediment cores indicated that primary productivity and SAV abundance in Lake Panasoffkee increased in the late 1800s, probably as a response to increased P loading from human settlement and forest clearance. SAV and associated periphyton served as temporary sinks for soluble P, maintaining relatively clear-water, low-nutrient conditions in the lake. P accumulation in Lake Panasoffkee sediments increased together with indicators for greater SAV presence. This suggests that SAV and associated epiphytes promote P burial and retention in sediments. Although it might be assumed that rooted submersed macrophytes are directly responsible for P uptake from water and transfer to sediments, C/N and stable carbon isotope results argue for the importance of other macrophyte growth forms, and perhaps epiphytic algae, in permanent OM and P sequestration. For instance, high rates of photosynthesis by epiphytes in hard-water systems consume CO₂ and promote CaCO₃ precipitation. Sloughing of accumulated carbonates from macrophyte leaves transfers epiphytes and associated P to the sediment. Our paleolimnological findings are relevant to restoration efforts in the Florida Everglades and support the claim that constructed SAV wetlands remove P from waters effectively.     

Effects of turbulence motion on the growth and physiology of aquatic plants

Growth, stem morphology and some biochemical parameters were studied of one completely submerged (Myriophyllum spicatum) and two floating leaved macrophytes (Nymphoides peltata and Trapa japonica) under different turbulence velocities. The root mean square velocities of the high, medium and low amount of turbulence that was generated for the experiment were 2.18 ± 0.66, 1.48 ± 0.26 and 0.70 ± 0.07 cm s⁻¹, respectively, in the microcosm. All three experimental plants survived exposed to all turbulence conditions provided, although a decrease in shoot elongation rate was associated with an increase in turbulence. Acceleration of tissue H₂O₂ generation and MDA content increased during the study period in all plant species. Oxidative enzymatic activities (POD, IAA and CKX) increased with time in plants under medium and high turbulence velocities. The shoot elongation rate, stem and leaf diameter, chlorophyll content and carbohydrate fractionations were found to be affected by this abiotic stress. It is evident from this study that high turbulence velocity inhibits normal metabolic activities of all three plants, while low to medium turbulence does not harm the floating leaved plants. Moreover, floating leaved plants were found to possess highly capable strategies to cope with this mechanical stress than completely submerged species.     

人工湿地植物的选择

本文阐述了植物在人工湿地中的作用和选择人工湿地植物的一些原则,并分析了人工湿地在我国的应用前景.植物在人工湿地中起着非常重要的作用,不但可以去除污染物质,维持湿地环境,而且具有生态美学和经济价值;选择了人工湿地植物应考虑植物的适应性、耐污能力、净化能力、根系、经济和观赏价值以及物种间的合理搭配.最后指出,人工湿地技术在我国有广阔的应用前景.     

中国西北干旱区湖泊沉积物中有机质碳同位素组成的环境意义——以民勤盆地三角城古湖泊为例

通过对中国西北干旱区石羊河流域民勤盆地三角城古湖泊沉积物有机质碳同位素组成(δ13Corg)分析,表明末次冰期与全新世时气候和植被有明显的差异,末次冰期δ13Corg总体偏轻(-30‰～-25‰),而全新世碳同位素组成则有较大的变化,在早全新世碳同位素组成有多次短期快速变重(-10‰左右)的变化,中全新世碳同位素组成总体偏重(-20‰～-10‰),晚全新世碳同位素组成偏轻(-25‰左右)。分析表明湖泊沉积物有机质碳同位素组成反映了陆生C3植物和湖泊内源水生植物变化的关系,末次冰期以来西北干旱区C4植物不发育,偏重的有机质碳同位素值与C4植物无关。从沉积物中有机质组分、元素等分析表明,末次冰期时主要以河流相沉积为主,湖泊中有机质主要来源于上游祁连山的陆生C3植物,有机碳含量较低,表明当时的上游的陆生植被不繁盛,区域气候较干冷;从全新世开始,三角城古湖泊开始形成,沉积物中碳同位素组成偏重的有机质主要来源于湖泊中的沉水植物,此时湖泊水体较大,湖泊生产力较高。而沉积物中有机质碳同位素组成偏轻时期的有机质主要来源于挺水植物、陆生C3植物,较低的有机碳含量说明该时期陆生植被不发育,气候较干冷,湖泊水体较小