太湖马来眼子菜(Potamogeton malaianus)生物量变化及影响因素

2006年5月和10月在太湖马来眼子菜分布区进行了定点采样,分析了马来眼子菜的生物量在不同水域变化特征及影响其生物量主要因素。结果表明:不同水环境中,马来眼子菜的生物量变化较大,介于526～4843g/m2,个体植株生物量依次为叶>根>茎,其中叶的生物量占总生物量的55%～80%。水深增加能促进植株高度和生物量的增加,但单位面积生物量变化不明显。群落的自疏效应使马来眼子菜生物量与资源供应维持在一个动态平衡的水平上。马来眼子菜的生物量与水体中TN呈显著正相关,P是影响其生物量变化的间接限制因子,根、茎、叶的N/P介于16.92～59.88之间,叶片的N/P达到42.33。马来眼子菜对水环境的形态可塑性响应是其在水环境长期变化中逐步成为幸存者和优势种的重要原因之一。底泥的深度和营养含量对其分布和生物量具有显著影响。围网捕捞、养殖以及航运的发展是造成局部地区马来眼子菜生物量急剧下降的主要人为因素。不同水域的生物量的差异是水深、水体营养盐、底质特征、水体透明度、人类活动等因素综合作用的结果。同时,对水环境变化在形态上较强的可塑性响应,也是马来眼子菜生物量变化的重要原因之一。     

太湖马来眼子菜(Potamogeton malaianus)生物量变化及影响因素

2006年5月和10月在太湖马来眼子菜分布区进行了定点采样,分析了马来眼子菜的生物量在不同水域变化特征及影响其生物量主要因素。结果表明：不同水环境中,马来眼子菜的生物量变化较大,介于526~4843 g/m²,个体植株生物量依次为叶>根>茎,其中叶的生物量占总生物量的55%~80%。水深增加能促进植株高度和生物量的增加,但单位面积生物量变化不明显。群落的自疏效应使马来眼子菜生物量与资源供应维持在一个动态平衡的水平上。马来眼子菜的生物量与水体中TN呈显著正相关,P是影响其生物量变化的间接限制因子,根、茎、叶的N/P介于16.92~59.88之间,叶片的N/P达到42.33。马来眼子菜对水环境的形态可塑性响应是其在水环境长期变化中逐步成为幸存者和优势种的重要原因之一。底泥的深度和营养含量对其分布和生物量具有显著影响。围网捕捞、养殖以及航运的发展是造成局部地区马来眼子菜生物量急剧下降的主要人为因素。不同水域的生物量的差异是水深、水体营养盐、底质特征、水体透明度、人类活动等因素综合作用的结果。同时,对水环境变化在形态上较强的可塑性响应,也是马来眼子菜生物量变化的重要原因之一。     

Effects of an artificial protection structure on the sandy shore macrofaunal community: the special case of Lido di Dante (Northern Adriatic Sea)

Biomanipulation of eutropicated peaty lakes has rarely been successful; clear water with dense macrophyte stands fails to develop in most cases. It was unclear whether (1) high turbidity due to resuspension by benthivorous fish or wind is the major cause of low macrophyte density or whether (2) the establishment of submerged macrophyte stands is prevented by a lack of propagules, low cohesive strength of the lake sediment, high concentrations of phytotoxics, grazing by waterfowl and/or shading by periphyton growth. These hypotheses were tested in an experiment in a shallow peat lake in the Netherlands (Terra Nova). Removal of fish from a 0.5 ha experimental site resulted in clear water and the development of a dense (90% coverage) and species-rich (10 species) submerged vegetation. At a fish-stocked site and a control site the water remained turbid and dense macrophyte stands did not develop. The establishment of submerged macrophytes appeared not to be limited by a lack of propagules. Introduced plants grew poorly in turbid water, but very well in clear water. Exclosures showed that bird grazing reduced the plant biomass. In clear water grazing seemed to enhance the vegetation diversity. Periphyton development did not prevent plant growth in clear water. After the experiment, the fish stock was greatly reduced in the whole lake (85 ha), to test if (3) in a large lake, submerged macrophyte stands will not develop after biomanipulation. In the first season after fish reduction, transparency increased and species-rich submerged macrophyte stands developed, covering 60% of the shallow parts of the lake. Most of the species known to have occurred in the past re-established. The results indicate that high turbidity caused by benthivorous fish in combination with bird grazing were the major causes of the absence of submerged macrophyte stands in this lake. Abiotic conditions after the clearing of the lake were suitable for the growth of macrophytes. We infer that the restoration potential of submerged macrophyte stands in eutrophicated peaty lakes can be high, and results can be obtained quickly.     

Weight-density relationships in submerged macrophytes

Summary Crowded stands of submerged plants in Québec lakes have a weight-density with a shallower, but not significantly different, slope and an intercept 10 fold lower than those for terrestial stands. The examination of a larger data set including both freshwater and submerged macrophytes supported these differences. This data set suggested that those differences, as well as those among submerged stands, are largely attributable to the light levels incident upon the stand. The differences in weight-density relationships between submerged and terrestrial stands were paralleled by a smaller biomass per unit volume outgrown of the submerged plants, as predicted from the dimensional examination of the weight-density relationship. The variations in biomass per unit volume associated to differences in the species growth form explained deviations about the weightdensity relationship of stands growing under relatively similar light conditions.Contribution No. 201 to the Lake Memphremagog project, McGill Limnology Research Centre     

梁子湖六种沉水植物种群数量和生物量周年动态

研究了梁子湖子湖之一满江湖的六种沉水植物种群数量和生物量在1997.3-1998.3的月动态。结果表明:满江湖沉水植物群落中,优势种为黄丝草、金鱼藻和穗状狐尾藻;六种沉水植物种群最大密度、最大单位面积生物量出现的月份各不相同,但两者变化的趋势一致。黄丝草、穗状狐尾藻种群为增长型种群,金鱼藻、苦草、黑藻种群稳定发展,菹草种群有衰退的趋势。沉水植物群落的最大生物量达到4676g/m2(鲜重,10月),总水草的最大密度为1865枝/m2(11月).根据1997年3-12月植物生长期内的数据,拟合出了六种沉水植物和总水草的生长模型方程。       

牛山湖两种优势小型鱼类空间分布与沉水植被的关系

运用8种网目规格的成套浮性刺网作为鱼类采样工具,于2005年夏季在长江中游浅水草型湖泊牛山湖进行鱼类定量采样,通过比较不同茂密程度黄丝草生境中的小型鱼类组成、数量和大小结构,探讨此类湖泊小型鱼类的空间分布特征及其与沉水植被的关系.采样期间共捕获13种1124尾鱼,依据其等级丰度和出现频次,鳖和红鳍原鲌为该湖优势上层小型鱼类.在调查的沉水植物生物量范围内,鱼类物种丰富度和Shannon多样性指数与沉水植物生物量之间呈现倒抛物线关系;两种优势小型鱼类的种群丰度均与沉水植物生物量有着显著的线性正相关关系,且其平均个体大小在裸地生境较高、沉水植被茂密区较低,幼鱼更倾向群聚于厚密的黄丝草生境中;其他生境因子(水深和离岸距离)对鳖和红鳍原鲐空间分布的影响不显著.黄丝草植被生境是牛山湖两种优势小型鱼类的重要保护生境,应加强对黄丝草等沉水植被的保护及恢复.     

Influence of macroinvertebrates and macrophytes on waterfowl utilization of wetlands in the Prairie Pothole Region of northwestern Wisconsin

Waterfowl and limnological data were monitored on Waterfowl Production Area (WPA) wetlands in northwestern Wisconsin over a 6-yr period (1983–88) to determine the impact of macroinvertebrates and macrophytes on waterfowl utilization. Interrelationships between limnological conditions and Waterfowl Breeding Pair Densities (BPDs reported as pairs/ha water surface) were analyzed using correlation and general linear model analysis techniques.Annual changes in waterfowl BPDs differed between wetlands according to differences in the structure of macrophyte communities and basin morphometry. The strength of associations differed between the two dominant waterfowl species. In a wetland dominated by dense stands of submersed vegetation, annual fluctuations in blue-winged teal (Anas discors) BPDs corresponded directly with changes in macrophyte biomass, but not with changes in macroinvertebrate density. In a nearby less densely vegetated wetland of similar water chemistry and trophic status, fluctuations in teal BPDs corresponded directly with changes in macroinvertebrate density, but not with changes in macrophyte biomass. These associations occurred despite a significant positive correlation between macroinvertebrates and macrophyte biomass in the latter habitat. Annual fluctuations in mallard (Anas platyrhynchos) BPDs were not correlated significantly with either macrophyte biomass or macroinvertebrate density in either wetland.     

附着生物对太湖沉水植物影响的初步研究

在水草生长比较旺盛的季节（5—6月）,以富营养化严重的太湖梅梁湾和水草较丰富的贡湖湾作为采样区域,研究了2种环境状态不同湖区附着生物的现存量及其对沉水植物的影响.结果表明:富营养化严重水域植物上附着生物的现存量较高,但不同种类植物间有所差异.附着生物显著抑制水生植物光合作用,6月的抑制作用高达91.9%以上.这种抑制作用的大小随附着生物量的增加而增强,且受宿主植物的影响.     

Impacts of sediment type on the performance and composition of submerged macrophyte communities

To restore deteriorated lake ecosystems, it is important to identify environmental factors that influence submerged macrophyte communities. While sediment is a critical environmental factor for submerged macrophytes and many studies have examined effects of sediment type on the growth of individual submerged macrophytes, very few have tested how sediment type affects the growth and species composition of submerged macrophyte communities. We constructed submerged macrophyte communities containing four co-occurring submerged macrophytes (Hydrilla verticillata, Myriophyllum spicatum, Ceratophyllum demersum and Chara fragilis) and subjected them to three sediment treatments, i.e., clay, a mixture of clay and quartz sand at a volume ratio of 1:1 and a mixture at a volume ratio of 1:4. Compared to the clay, the 1:1 mixture treatment greatly increased overall biomass, number of shoot nodes and shoot length of the community, but decreased its diversity. This was because it substantially promoted the growth of H. verticillata within the community, making it the most abundant species in the mixture sediment, but decreased that of M. spicatum and C. demersum. The sediment type had no significant effects on the growth of C. fragilis. As a primary nutrient source for plant growth, sediment type can have differential effects on various submerged macrophyte species and 1:1 mixture treatment could enhance the performance of the communities, increasing the overall biomass, number of shoot nodes and shoot length by 39.03%, 150.13% and 9.94%, respectively, compared to the clay treatment. Thus, measures should be taken to mediate the sediment condition to restore submerged macrophyte communities with different dominant species.     

Size spectra and abundance of planktonic ciliates within various habitats in a macrophyte-dominated lake (Eastern Poland)

Body size, community structure, abundance and biomass of ciliates were compared in various stands of macrophytes in a macrophyte-abundant shallow lake in Eastern Poland. Samples were collected in belts of Phragmites, Typha, Ceratophyllum, Elodea, Stratiotes and Chara. Additionally, protozooplankton was collected from the open water zone surrounding the vegetation belts. Differences in numbers of ciliate taxa between micro-sites were statistically significant. The highest numbers were found in Chara and Ceratophyllum stands, lower numbers in Stratiotes and Elodea stands and the lowest in the open water, Phragmites and Typha areas. Ciliate biomass was, like density, significantly higher in submerged macrophytes than in emergent macrophytes and open water zones. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of two vegetated zones of sparse stem structure (Phragmites and Typha) and the open water zone, the second group comprised submerged macrophyte species, which were more dense and complex. Generally, the abundance of ciliates correlated positively with total suspension solid (TSS) and total organic carbon (TOC) concentrations. In the Chara and Ceratophyllum stands, relations between ciliate numbers, TSS and TOC were stronger.     

Interactive effects of light and snail herbivory rather than nutrient loading determine early establishment of submerged macrophytes

Submerged macrophytes play a key role in maintaining a clear‐water phase and promoting biodiversity in shallow aquatic ecosystems. Since their abundance has declined globally due to anthropogenic activities, it is important to include them in aquatic ecosystem restoration programs. Macrophytes establishment in early spring is crucial for the subsequent growth of other warm‐adapted macrophytes. However, factors affecting this early establishment of submerged macrophytes have not been fully explored yet. Here, we conducted an outdoor experiment from winter to early spring using the submerged macrophytes Potamogeton crispus and Vallisneria spinulosa to study the effects of shading, nutrient loading, snail herbivory (Radix swinhoei), and their interactions on the early growth and stoichiometric characteristics of macrophytes. The results show that the effects strongly depend on macrophyte species. Biomass and number of shoots of P. crispus decreased, and internode length increased during low light conditions, but were not affected by nutrient loading. P. crispus shoot biomass and number showed hump‐shaped responses to increased snail biomass under full light. In contrast, the biomass of the plant linearly decreased with snail biomass under low light. This indicates an interaction of light with snail herbivory. Since snails prefer grazing on periphyton over macrophytes, a low density of snails promoted growth of P. crispus by removing periphyton competition, while herbivory on the macrophyte increased during a high density of snails. The growth of V. spinulosa was not affected by any of the factors, probably because of growth limitation by low temperature. Our study demonstrates that the interaction of light with snail herbivory may affect establishment and growth of submerged macrophytes in early spring. Macrophyte restoration projects may thus benefit from lowering water levels to increase light availability and making smart use of cold‐adapted herbivores to reduce light competition with periphyton.     

Effects of Spirogyra arcta on biomass and structure of submerged macrophyte communities

The presence of algae can greatly reduce the amount of light that reaches submerged macrophytes, but few experimental studies have been conducted to examine the effects of algae on biomass and structure of submerged macrophyte communities. We constructed communities with four submerged macrophytes (Hydrilla verticillata, Egeria densa, Ceratophyllum demersum, and Chara vulgaris) in three environments in which 0 (control), 50 and 100% of the water surface was covered by Spirogyra arcta. Compared to the control treatment, the 100% spirogyra treatment decreased biomass of the submerged macrophyte communities and of all the four macrophytes except C. demersum. Compared to the control and 50% treatments, the 100% treatment significantly increased relative abundance of C. demersum and decreased that of E. densa. Therefore, the presence of S. arcta can greatly affect the productivity and alter the structure of submerged macrophyte communities. To restore submerged macrophyte communities in conditions with abundant algae, assembling communities consisting of C. demersum or similar species may be a good practice.     

Effects of grazing by fish and waterfowl on the biomass and species composition of submerged macrophytes

Biomanipulation improved water transparency of Lake Zwemlust (The Netherlands) drastically. Before biomanipulation no submerged vegetation was present in the lake, but in summer 1987, directly after the measure, submerged macrophyte stands developed following a clear-water phase caused by high zooplankton grazing in spring. During the summers of 1988 and 1989 Elodea nuttallii was the most dominant species and reached a high biomass, but in the summers of 1990 and 1991 Ceratophyllum demersum became dominant. The total macrophyte biomass decreased in 1990 and 1991. In 1992 and 1993 C. demersum and E. nuttallii were nearly absent and Potamogeton berchtholdii became the dominant species, declining to very low abundance during late summer. Successively algal blooms appeared in autumn of those years reaching chlorophyll-a concentrations between 60–130 µg l^–1. However, in experimental cages placed on the lake bottom, serving as exclosures for larger fish and birds, E. nuttallii still reached a high abundance during 1992 and 1993. Herbivory by coots (Fulica atra) in autumn/winter, and by rudd (Scardinius erythrophthalmus) in summer, most probably caused the decrease in total abundance of macrophytes and the shift in species composition.     

云南抚仙湖摇蚊幼虫的空间分布及其环境分析

2005年6—7月在抚仙湖共采集到摇蚊科幼虫5属6种,其中花纹前突摇蚊和羽摇蚊为优势种,两者的相对密度之和达94.9%,相对生物量之和达97.5％,其现存量基本代表了抚仙湖中摇蚊幼虫的现存量.全湖摇蚊幼虫平均密度为（275±333） ind·m^-2,平均生物量为(0.642±0.763） g·m^-2.花纹前突摇蚊为全湖性分布,羽摇蚊主要分布在明星鱼洞以南湖区,其他种类为局部性分布.小突摇蚊为典型的深水贫营养型种类,其分布的平均水深达107.2 m.抚仙湖摇蚊幼虫密度分布与水深呈极显著正相关(P＜0.001),与底质和水草的关系为沙砾石底＜沙泥底＜细泥底;水草区＜非水草区.与1980年前后的调查资料相比,摇蚊幼虫的出现率和现存量显著增加,并出现了典型富营养型的指示种羽摇蚊,表明抚仙湖水体的营养水平在提高.     

珠江河网典型水草床与贝类群落生物量特征

于2015年和2018年12月初调查珠江河网4个江段(左滩、小塘、外海和榄核)的典型水草床群落生物量时空变化特征,同时调查了相应江段的水草床、邻近非水草床区域的主要贝类生物量时空变化,并利用CCA分析其与主要水文、水质及沉积环境因子的相关性。结果表明:珠江河网典型水草床群落主要以刺苦草为优势种,偶伴生金鱼藻、穗状狐尾藻和轮叶黑藻等种类;对比两次调查结果发现,除小塘江段水草床生物量(以鲜重计)维持较稳定,高达9 kg·m^-2以外,其余3个江段的水草床均有种类减少、生物量下降的消落趋势。小塘江段贝类生物量最高,均值达968.8 g·m^-2,显著高于其他江段;所调查江段水草床区域中的贝类均高于非水草床区域;在由浅至深的水草床区域,虽然水草生物量逐增,但其贝类生物量却逐减;相同江段非水草床区域的贝类生物量显著低于水草床区域,表明珠江河网水草床为贝类提供良好的栖息、生长和繁育生境。径流量和水位变化可能是驱动珠江河网典型水草床群落年际演替的主要因素,而水草优势种类的保持可能受沉积物粒径组分和水体流速等因子的调控。     

An experimental system to study ecophysiological responses of submerged macrophytes to temperature and light

An experimental growth system was devised to study the ecophysiological responses of submerged macrophytes to temperature and light. Using the system, a pilot study was conducted to compare responses to light of three representative species common to the littoral zone of Lake Biwa: Vallisneria asiatica Miki var. biwaensis Miki, which is endemic to Japan, Potamogeton maackianus A. Benn., a dominant submerged macrophyte in Lake Biwa, and Elodea nuttallii (Planch.) St. John, one of the most influential submerged exotic macrophytes naturalized in Japan. Different relative growth rate responses and other growth parameters among the species were observed. We ascertained the experimental system to be useful for the comparison of ecophysiological responses of submerged macrophytes.     

水生植物群落动态与演替的研究

 本文根据10年定位研究的结果,讨论了哈尔滨朱顺泡(湖)水生植物的种类组成和动态变化;分析了群落建群种的替代及其影响因素;指出水体变浅是导致水生植物群落演替的关键因素。同时利用盖度、密度、频度和重要值等计算了群落的数量特征,并按重要值划分了不同演替阶段的优势种和亚优势种;根据生活型确定了群落的分层结构;建立了群落生物量的分层模型。随着湖底上垫作用的进行,物种的消失速率在加快;实验证明透明度仅影响沉水植物的分布,而营养盐含量低是群落生产力限制因子。     

Phytoplankton biomass in Lake Xolotlán (Managua): Its seasonal and horizontal distribution

Some well-documented studies on restoring eutrophic lake systems in The Netherlands by fish stock management have been evaluated with the emphasis on the role of macrophytes. Furthermore, the factors determining the light climate for submerged macrophytes in a large shallow eutrophic lake (Lake Veluwe) have been assessed and the potential success of biomanipulation in large scale projects is discussed. Today relatively little attention has been paid to macrophyte management although the importance of macrophytes in lake restoration has been recognized regularly. The biomanipulation strategy was successful in small scale projects. In a large scale project, however, wind-induced resuspension may largely determine the underwater light climate through attenuation by the water column and periphytic layer. Therefore, restoration of relatively large waterbodies by fish stock management only is expected not to lead to any noteworthy improvement of the light climate for submerged macrophytes. Additional measures aimed at reducing wind-induced resuspension of sediment particles and reestablishing of the macrophyte stands are required for successful biomanipulation strategies. Water quality managers should pay more attention to macrophyte stands in biomanipulation projects because macrophytes enhance a more stable and diverse ecosystem. Restoration objectives and the methods of their achievement must be carefully planned since an abundant submerged macrophyte vegetation may have undesirable effects as well.     

Assessing maximum depth distribution,vegetated area,and production of submerged macrophytes in shallow,turbid coastal lagoons of the southern Baltic Sea

Submerged macrophytes improve water quality in shallow coastal lagoons but eutrophication often resulted in a degradation of macrophytes. Management measures that protect and restore macrophyte stands require knowledge on what limits macrophyte distribution. Information on macrophyte production and distribution in the Darss-Zingst Bodden Chain (southern Baltic Sea) is lacking since an almost complete loss of submerged vegetation in the 1980s. Nutrient input was reduced in the 1990s and macrophytes seem to recover, although turbidity is high and light conditions are still poor. However, this recovery raised hope that returning macrophytes could stabilize sediments and improve water clarity. In this study, seasonal changes in photosynthesis–irradiance curves of selected macrophyte species were used to calculate potential primary production in different depths and turbidity situations. Bathymetry of the area is then used to assess depth distribution and vegetated area. Since the so-calculated depth limits correspond well with the actual depth distribution in the field, macrophyte depth distribution is concluded to be mostly determined by light conditions. Most macrophytes grow in very shallow areas up to 50 cm depth where also 70% of potential primary production takes place. Present light conditions do not support a further expansion of macrophyte distribution in the DZBC.     

Development of submerged macrophyte and epiphyton in a flow-through system: Assessment and modelling predictions in interconnected reservoirs

Every approach to lake restoration requires the reestablishment of submerged macrophytes. However, macrophyte overgrowth in shallow lakes may lead to deterioration and a consequent necessity for restoration treatments. We assumed that a major threat to the increased trophic level in the Jankovac flow-through system arises from the sediment, where the accumulation of deciduous leaf litter and decayed macrophyte fragments could generate anoxic conditions. The integrated Water Quality Model (WQM) and the Submerged Aquatic Vegetation Model (SAVM) were combined in the Jankovac Model (JanM) and applied during the vegetated season in 2008 and 2014, with the aim to offer a possible approach to the maintenance of good water quality. The impacts of flow velocity and epiphyton growth on submerged macrophyte coverage and biomass were simulated. Biocenotic analyses suggested that epiphyton growth was more extensive in 2014 in comparison to 2008. The results of JanM indicated that increased flow velocities enhanced macrophyte growth and dissolved oxygen concentrations concurrently with the decline of epiphyton biomass. Furthermore, results suggested that epiphyton growth rate of 0.4 d⁻¹ maintained macrophyte coverage and biomass at a satisfactory level of 70% reservoir coverage. Considering the proposed scenarios hydraulic treatment could be applied to regulate submerged macrophytes in shallow reservoirs, as an efficient and less invasive approach than sediment removal, especially in sensitive karst areas.