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.     

The species composition,occurrence and temporal stability of submerged aquatic macrophyte patches along the main channel border of pool 5A,Upper Mississippi River

Species composition, relative abundance, distribution and physical habitat associations of submerged aquatic macrophytes in the main channel border (MCB) habitat of Pool 5A, Upper Mississippi River (UMR) were investigated during the summers of 1980 and 1983. The submerged aquatic macrophytes in Pool .5A MCB were a small and stable component of the river ecosystem. Submerged plants occurred primarily in small, monospecific clumps. Clumps in close proximity to each other formed plant patches. Plant patches were stable in location and number between 1980 and 1983; 82.5% of the patches first observed in 1980 were present in 1983. Submerged macrophytes covered about 10–12 ha of the 201 ha MCB in Pool 5A. Submerged plants were most common in the lower two-thirds of the pool. Ten species of aquatic macrophytes occurred on rock channel-training structures and eleven occurred on non-rock substrates in the MCB. The most common submerged plants, in order of abundance, were Vallisneria americana Michx., Heteranthra dubia Jacq., Potamogeton pectinatus L., Ceratophyllum demersum L. and Potamogeton americanus C. & S.     

凤眼莲入侵程度对金鱼藻和黑藻生长及种间关系的影响

湿地生态系统中凤眼莲（Eichhornia crassipes）入侵造成湿地植物群落结构退化及功能崩溃,直接影响沉水植物的生长繁殖及初级生产力。目前关于凤眼莲的入侵机制有一定的研究,而关于凤眼莲入侵程度对沉水植物金鱼藻（Ceratophyllum demersum）和黑藻（Hydrilla verticillate）生长及种间关系的影响相对缺乏。以外来入侵植物凤眼莲,沉水植物金鱼藻和黑藻为研究对象,设计凤眼莲入侵程度（无入侵,轻度入侵对应盖度25%,重度入侵对应盖度75%）交叉定植方式（黑藻单种模式、金鱼藻单种模式,金鱼藻和黑藻混种模式）的控制实验,探究凤眼莲入侵强度对沉水植物金鱼藻和黑藻生长及种间关系的影响。结果表明,凤眼莲入侵程度显著降低了金鱼藻的生物量、分枝数;黑藻的株高、分枝数和分节数。无凤眼莲入侵时,两种沉水植物生物量均最大,两者种间竞争关系较强;随凤眼莲入侵盖度增加,两种沉水植物的生物量先急剧降低后略微增加,种间关系经过微弱促进后又变为竞争作用,其中黑藻表现出明显的竞争优势。此外,凤眼莲入侵略微降低了水体中的总氮、总磷含量。结构方程模型分析结果表明凤眼莲入侵以及水体总氮、总磷等水体理化性质对沉水植物生长均有显著负向影响（P<0.05）,且水体理化性质对沉水植物生长的影响强于凤眼莲入侵。总之,凤眼莲入侵显著降低了金鱼藻和黑藻生长繁殖,随着凤眼莲入侵程度增加,两种沉水植物种间关系由竞争转变为促进再转变为竞争。研究结果为凤眼莲入侵有效控制及湿地沉水植被的恢复与重建提供了一定的理论依据和技术支撑。     

An experimental study of habitat choice by Daphnia: plants signal danger more than refuge in subtropical lakes

1. In shallow temperate lakes, submerged plants often provide refuge for pelagic zooplankton against fish predation, a mechanism with potential strong cascading effects on water transparency and on the entire ecosystem. In (sub)tropical lakes, however, the interaction between aquatic plants and predation may be more complex, particularly because fish density is high within the plant beds in such systems. 2. Using laboratory ‘habitat choice’ experiments, we determined the effects of three (sub)tropical free‐floating plants, Eichhornia crassipes, Pistia stratiotes and Salvinia auriculata and the cosmopolitan submerged Ceratophyllum demersum, on horizontal movement by the water flea Daphnia obtusa. We tested for avoidance of plants in the absence and presence of alarm signals from crushed conspecifics and chemical cues from the fish Cnesterodon decemmaculatus, the fish have been subjected to different feeding regimes. 3. In the absence of other stimuli, D. obtusa strongly avoided the plants and the crushed conspecifics, as expected. However, the response to fish was insignificant regardless of their previous feeding regime. The avoidance of free‐floating plants was more pronounced than that of the submerged plant. Contrary to predictions based on research in temperate lakes, Daphnia did not take refuge among the plants but rather swam away from them when exposed simultaneously to plants and alarm signals. 4. We hypothesise that the avoidance of plants by D. obtusa may ultimately be attributable to an expectedly higher predation risk within the plants than in the pelagic, because of a high density of associated zooplanktivorous fish in the former. In the (sub)tropics, therefore, aquatic plants and particularly the free‐floating ones, may not promote cascading effects via Daphnia grazing on phytoplankton as seen in temperate eutrophic lakes.     

Effects of light heterogeneity on growth of a submerged clonal macrophyte

Many studies have examined the effects of spatial heterogeneity in light supply on clonal plants in terrestrial environments, but few have examined those in aquatic conditions. In a greenhouse experiment, we grew the rhizomatous submerged macrophyte Vallisneria spiralis L. in containers in three homogeneous light treatments (100%, 65%, and 30% of ambient light coded as high, medium, and low light, respectively) and two heterogeneous ones differing in patch scale (small and large patch). The growth of V. spiralis decreased significantly with decreasing light availability. In the low light conditions, V. spiralis allocated greater biomass to shoots and developed elongated leaves. In the patchy treatments, ramets distributed in the light‐rich patches had significant costs in the large patch treatment, but not in the small patch treatment, while both small and large patch treatments had no significant benefits in the light‐poor patches. We conclude that V. spiralis could escape from adverse habitats and occupy the favorable habitats. Providing the same amount of light, responses of V. spiralis to different patch scales were different at the patch level, but not at the whole clone level. Together, growth of V. spiralis could not benefit from different patch scales in heterogeneous environments at the patch as well as the whole clone level.     

Loss of Submerged Macrophytes in Shallow Lakes in North‐Eastern Germany

During the 1950s, the submerged vegetation of shallow lakes in north‐eastern Germany was dominated by nutrient tolerant species, with Ceratophyllum demersum and Myriophyllum sp. being most common. Almost one third of 300 investigated lakes had already lost their submerged macrophytes at that time. Very shallow lakes showed either high or low macrophyte abundance. Increasing depth resulted in medium macrophyte abundances, which may contribute to the stabilisation of local or temporary clearwater states. Forty years later, the percentage of lakes without macrophytes had dramatically increased. Between 55 and 85% of the investigated lakes showed a low abundance. The decline was most pronounced in very shallow lakes. The majority of the investigated lakes showed summer TP concentrations below 100 μg L^–1, but no colonisation by submerged macrophytes, which indicates a resilience against re‐colonisation.     

Concentrations of Trace Metals in Dominant Aquatic Plants of the Lake Provala (Vojvodina, Yugoslavia)

The trace metal (Fe, Mn, Zn, Cu, Ni, Pb, Cd, Sr, and Cr) contents in the most common submerged and floating aquatic plants Ceratophyllum demersum L., Myriophyllum spicatum L., and Nymphoides flava Hill. of Provala Lake were evaluated. Considerable higher contents of iron, manganese, zinc, nickel, lead and strontium were found in submerged species than in the floating ones. The presence of cadmium and lead in plant tissues points to a certain degree of lake water pollution.     

Benthic macroinvertebrates associated with four species of macrophytes

Benthic macroinvertebrates associated with four species of macrophytes (Nymphoides peltata, Ceratophyllum demersum, Polygonum amphibium and Carex sp.) were investigated during two growing seasons (2001 and 2002) in the slow-flowing Čonakut Channel in the Kopački rit Nature Park in Croatia. A total of 31 macroinvertebrate taxa were found. C. demersum, a submerged plant with dissected leaves, supported the highest macroinvertebrate abundance, almost seven times more than N. peltata, a floating plant with undissected leaves, which harboured the lowest abundance during the research period. Chironomidae larvae (50–83%) and Oligochaeta (14–46%) were the most abundant groups recorded on all macrophyte species. Water-level fluctuation, because of its influence on the appearance and growth of aquatic vegetation, and the trophic state of water within the macrophyte stands seemed to be the main factors which affected the taxonomic composition and abundance of macroinvertebrates.     

Comparison of the Adsorption Capabilities of Myriophyllum spicatum and Ceratophyllum demersum for Zinc,Copper and Lead

Industrial wastewaters contain various heavy metal components and therefore threaten aquatic bodies. Heavy metals can be adsorbed by living or non‐living biomass. Submerged aquatic plants can be used for the removal of heavy metals. This paper exhibits the comparison of the adsorption properties of two aquatic plants Myriophyllum spicatum and Ceratophyllum demersum for lead, zinc, and copper. The data obtained from batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q_max) were obtained for both plant species and each metal. The maximum adsorption capacities (q_max) achieved with M. spicatum were 10.37 mg/g for Cu²⁺, and 15.59 mg/g for Zn²⁺ as well as 46.49 mg/g for Pb²⁺ and with C. demersum they were 6.17 mg/g for Cu²⁺, 13.98 mg/g for Zn²⁺ and 44.8 mg/g for Pb²⁺. It was found that M. spicatum has a better adsorption capacity than C. demersum for each metal tested. Gibbs free energy and the specific surface area based on the q_max values were also determined for each metal.     

Clear,crashing, turbid and back – long‐term changes in macrophyte assemblages in a shallow lake

相似文献   

Natural and anthropogenic forcing of aquatic macrophyte development in a shallow Danish lake during the last 7000 years

Aim To investigate the long‐term changes in aquatic vegetation in a lowland, shallow lake, and to assess the relationship between aquatic vegetation and natural and anthropogenic catchment changes. Location Gundsømagle Sø, Zealand, Denmark: a shallow (mean depth 1.2 m), hypereutrophic lake (mean annual total phosphorus (TP) c. 700 μg TP L^?1) located in a predominantly agricultural catchment (88% cultivated land). The lake is presently devoid of macrophytes. Methods One hundred and forty‐seven contiguous samples from a sediment core (taken in 2000) were analysed for macrofossil remains together with loss‐on‐ignition and dry weight. From an earlier sediment core (taken in 1992), 67 samples were analysed for pollen and the two cores were correlated using the ignition residue profiles. Core chronology was determined by ²¹⁰Pb and ¹³⁷Cs dating of the recent lake sediments, while older sediments were dated by pollen‐stratigraphical correlation, as ¹⁴C dating proved problematical. Aquatic macrofossil abundance was used to reconstruct past changes in the lake's plant community and water‐level. The contemporary catchment land‐use change was inferred from sedimentary pollen data, and soil erosion to the lake was deduced from the minerogenic content of the lake sediments. Results The macrofossil record covers the last 7000 years, but aquatic plant remains were scarce prior to c. 1300 bc . After this date the abundance of submerged and emergent macrophyte remains increased dramatically, paralleled by an increase in sediment minerogenic matter and non‐arboreal pollen (NAP). Aquatic plant remains were abundant for more than 3000 years until the mid 1900s. Macrofossils of Linum usitatissimum (L.) (flax) and high pollen percentages of ‘Cannabis type’ (hemp) were recorded in periods between c. 1150 bc and 1800 ad . Main conclusions Our study suggests that, between c. 5000 bc and 1300 bc , the submerged plant community was confined to the littoral zone. From 1300 bc onwards, the submerged macrophyte vegetation expanded rapidly across the lake bed, presumably as a response to lake shallowing caused by a combination of climatic‐induced water‐level lowering and enhanced erosional infilling of the lake basin due to intensified anthropogenic activities in the catchment. The lake was meso‐eutrophic and had an extensive and diverse aquatic flora for more than 3000 years, until the middle of the twentieth century. In periods between c. 1150 bc and 1800 ad , the lake experienced direct anthropogenic impact from retting of fibre plants (Linum and Cannabis). Over the last 200 years, erosional infilling of the lake basin increased drastically, probably as a result of agricultural intensification. In the twentieth century, the lake was strongly affected by nutrient enrichment from both point sources (sewage from built‐up areas) and diffuse agricultural run‐off which led to hypertrophic conditions and the collapse of the submerged vegetation c. 1950–60. The concept of ‘naturalness’ and the implications for lake conservation are discussed.     

Closely related freshwater macrophyte species,Ceratophyllum demersum and C. submersum,differ in temperature response

相似文献   

Host Range of Mycoleptodiscus terrestris, a Microbial Herbicide Candidate for Eurasian Watermilfoil, Myriophyllum spicatum

A native strain of the fungal plant pathogen Mycoleptodiscus terrestris is capable of causing under experimental conditions necrotic shoot lesions and a generalized decline and disintegration of Eurasian watermilfoil (Myriophyllum spicatum), an exotic submerged aquatic weed in North America. The potential of this fungus to cause disease on nontarget plants was evaluated on 33 species and cultivars in 11 families. The nontarget selection, intended as a Tier I group, was biased toward probable suscepts consisting of submerged, floating, and emergent aquatic species and terrestrial crop plants. The plants were exposed to the fungal mycelium formulated in alginate beads. Pathogenicity rather than phytotoxicity was the primary mode of attack by the fungus. Of the 16 nontarget aquatic species tested, the fungus was pathogenic to Hydrilla verticillata (hydrilla), Myriophyllum aquaticum (parrotfeather), and Ceratophyllum demersum (coontail), but only in hydrilla did it cause plant mortality comparable to that in Eurasian watermilfoil. The remaining 13 submerged, floating, and emergent aquatic species were unaffected. Of the 17 terrestrial species screened, none was significantly affected by the fungus in germination studies, but postemergent disease symptoms developed on seedlings of 10 species. Four of the 10, Medicago sativa (alfalfa), Lotus corniculatus (birdsfoot trefoil), Trifolium hybridum (alyce clover), and T. repens (white clover), developed disease affecting 26-50% of their tissues. Thus, this host range testing scheme, based on the concept of screening plants under the maximum hazard potential, helped to identify susceptible species. Nonetheless, it exaggerated the nontarget risk due to the small number of host species tested. Screening a taxonomically diverse and larger selection of plants as well as testing under conditions of less severe exposure to the fungal inoculum are necessary to obtain a more realistic view of the host range than presently indicated.     

TEMPERATURE AND IRRADIANCE EFFECTS ON GROWTH OF PITHOPHORA OEDOGONIA (CHLOROPHYCEAE) AND SPIROGYRA SP. (CHAROPHYCEAE)1

Growth responses of Pithophora oedogonia (Mont.) Wittr. and Spirogyra sp. to nine combinations of temperature (15°, 25°, and 35°C) and photon flux rate (50, 100, and 500 μmol·m^?2·s^?1) were determined using a three-factorial design. Maximum growth rates were measured at 35°C and 500 pmol·m^?2·s^?1 for P. oedogonia (0.247 d^?1) and 25°C and 500 μmol·m^?2·s^?1 for Spirogyra sp. (0.224 d^?1). Growth rates of P. oedogonia were strongly inhibited at 15°C (average decrease= 89%of maximum rate), indicating that this species is warm stenothermal. Growth rates of Spirogyra sp. were only moderately inhibited at 15° and 35°C (average decrease = 36 and 30%, respectively), suggesting that this species is eurythermal over the temperature range employed. Photon flux rate had a greater influence on growth of Spirogyra sp. (31% reduction at 50 pmol·m^?2·s^?1 and 25°C) than it did on growth of P. oedogonia (16% reduction at 50 μmol·m^?2·s^?1 and 35°C). Spirogyra sp. also exhibited much greater adjustments to its content of chlorophyll a (0.22–3.34 μg·mg fwt^?1) than did P. oedogonia (1.35–3.08 μg·mg fwt^?1). The chlorophyll a content of Spirogyra sp. increased in response to both reductions in photon flux rate and high temperatures (35°C). Observed species differences are discussed with respect to in situ patterns of seasonal abundance in Surrey Lake, Indiana, the effect of algal mat anatomy on the internal light environment, and the process of acclimation to changes in temperature and irradiance conditions.     

沉水植物化感作用对西湖湿地浮游植物群落的影响

通过微宇宙实验,在控制光照和营养盐浓度的条件下分别研究了苦草(Vallisneria spiralis)、金鱼藻(Ceratophyllum demersum)和穗花狐尾藻(Myriophyllum spicatum)的化感作用对采集于杭州西湖湖西湿地的藻类密度、叶绿素a浓度、群落结构、多样性指数等的影响。其结果表明,3种沉水植物对微宇宙系统中的藻类都具有明显影响,藻类密度与叶绿素a浓度受到显著抑制,3个草-藻研究系统中藻类群落结构都发生了变化。在实验末期苦草组、金鱼藻组和穗花狐尾藻组中藻类总生物量(以细胞密度计)分别较初始值降低了37.06%、78.37%和83.40%。栅藻对3种沉水植物的化感作用敏感性较弱。藻类生物多样性方面,穗花狐尾藻系统中最高,其次是金鱼藻组,最后是苦草组,其Shannon-Wiener指数(H)分别为2.76、2.06和0.72,穗花狐尾藻组中H的显著高于苦草组(P0.05)。     

Ceratophyllum demersum – phosphorus interactions in nutrient enriched aquaria

High macrophyte density in shallow lakes is often associated with clear water, especially when the non-rooted, submerged angiosperm Ceratophyllum demersum is dominant. Lack of true roots and high surface area:volume ratio suggest that nutrient uptake from the water column by C. demersum may be high. Therefore, possible competition for nutrients, including phosphorus (P), could contribute to phytoplankton inhibition. C. demersum ability to absorb and store P at four nutrient levels (unenriched + three enrichment treatments) was investigated in a 34-day laboratory experiment using agar-based nutrient diffusing substrates (NDSs). P uptake rates and abatement potential by C. demersum were assessed from total phosphorus concentration (TP) patterns in the water column. Changes in C. demersum biomass (wet weight) also were determined. C. demersum took up P quickly. Some P release occurred during the experiment, especially under high nutrient conditions. Initial net P uptake by C. demersum was high, but medium-term (five weeks) average uptake was relatively low. Projected long-term net P uptake approached zero. Plant biomass loss and production of macrodetritus (plant fragments >1 mm) were highest in unenriched aquaria. Biomass loss in the lower enriched treatments was equally divided between loss as macrodetritus and as dissolved organic matter (DOM), but loss as DOM was four times higher than loss as macrodetritus in the highest nutrient treatment. The results suggest that medium- and long-term low phytoplankton biomass in C. demersum-rich lakes is achieved via mechanisms other than direct competition for nutrients from the water column.     

C4 characteristics of photosynthesis in the C3 alga Hydrodictyon africanum

Abstract Results obtained with Hydrodictyon africanum, and data from the literature, show that most green algae of the chlorophyte type (e.g. Chlorella, Chlamydomonas, Hydrodictyon) differ in their photosynthetic C fixation characteristics from most green algae of the charophyte type (e.g. Spirogyra, Chara) and from C₃ higher plants. The chlorophyte algae fix inorganic carbon by the photosynthetic carbon reduction cycle pathway, but have a low CO₂ compensation point in 250 μM O₂, a low inhibition of CO₂ fixation from 10 μM CO₂/250 μM O₂ when compared with 10 μM CO₂/zero O₂, and a low half-saturation constant for CO₂. These three characteristics are different from those of charophytes and C₃ higher plants, and resemble those of C₄ higher plants. It is suggested that these characteristics of chlorophyte algae are the result of a ‘CO₂ concentrating mechanism’ which increases the CO₂/O₂ ratio at the site of ribulose bisphosphate carboxylase-oxygenase action in a similar way to that achieved by the C₄?C₃ acid cycle in C₄ plants. In the chlorophyte algae, however, CO₂ concentration probably involves active HCO₃^? transport at the inner membrane of the chloroplast envelope. Active HCO₃^? transport can occur at the plasmalemma of charophyte algae and submerged aquatic higher plants as well as chlorophyte algae, so it is unlikely to explain the differences between the two groups of aquatic green plants. Differences in the properties of ribulose bisphosphate carboxylase-oxygenase, and differences in CO₂ production in the light, also seem inadequate to account for the different photosynthetic characteristics. The chlorophyte type of ‘C0₂ concentrating mechanism’ appears to be common in other classes of eukaryotic algae, and in cyanophytes. Some of the ‘advanced’ members of these eukaryotic algal classes (including the chlorophytes) may lack the mechanism, while some ‘primitive’ charophytes may retain the mechanism which their ancestors presumably possessed.     

Vegetative Propagule Pressure and Water Depth Affect Biomass and Evenness of Submerged Macrophyte Communities

Vegetative propagule pressure may affect the establishment and structure of aquatic plant communities that are commonly dominated by plants capable of clonal growth. We experimentally constructed aquatic communities consisting of four submerged macrophytes (Hydrilla verticillata, Ceratophyllum demersum, Elodea nuttallii and Myriophyllum spicatum) with three levels of vegetative propagule pressure (4, 8 and 16 shoot fragments for communities in each pot) and two levels of water depth (30 cm and 70 cm). Increasing vegetative propagule pressure and decreasing water level significantly increased the growth of the submerged macrophyte communities, suggesting that propagule pressure and water depth should be considered when utilizing vegetative propagules to re-establish submerged macrophyte communities in degraded aquatic ecosystems. However, increasing vegetative propagule pressure and decreasing water level significantly decreased evenness of the submerged macrophyte communities because they markedly increased the dominance of H. verticillata and E. nuttallii, but had little impact on that of C. demersum and M. spicatum. Thus, effects of vegetative propagule pressure and water depth are species-specific and increasing vegetative propagule pressure under lower water level can facilitate the establishment success of submerged macrophyte communities.     

Chlorophyll fluorometry sheds light on the role of desiccation resistance for vegetative overland dispersal of aquatic plants

相似文献   

Individuality in Problem Solving: String Pulling in Two Carduelis Species (Aves: Passeriformes)

The research reported here was designed to study the individual peculiarities of birds in solving a problem. Goldfinches Carduelis carduelis and siskins C. spinus were tested with the string‐pulling task: sitting on a perch from which a small food container is suspended by a string the test bird had to lift the container, using the bill to pull the string stepwise up and a foot to hold it, and repeat that until they could reach the food. Fifty‐two goldfinches and 29 siskins raised under controlled conditions were tested individually. Three groups became apparent: ‘inventors’ (23% of goldfinches; 62% of siskins) solved the problem by themselves; ‘imitators’ (25% of goldfinches; 10% of siskins) succeeded after seeing a performing conspecific; ‘duffers’ (52% of goldfinches, 28% of siskins) did not succeed either way. The species – but not the sexes – differed significantly in string‐pulling ability. The results of our experiments indicate that string pulling is an acquired combination of innate behaviour elements. An individual's string‐pulling competence may depend on prior experience of handling branchlets, on trial‐and‐error learning and on social learning (emulation). However, some individuals succeeded without these facilitating factors, while others did not succeed at all despite all of them present. Although functionally and motivationally related to feeding, the learned string pulling is often shown as a playful activity without an obvious reward.