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  • 1
    Electronic Resource
    Electronic Resource
    Seed dispersal, germination and seedling growth of six helophyte species in relation to water-level zonation (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 34 (1995), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Seed dispersal, germination, and seedling growth characteristics of six helophyte species. Iris pseudacorus, Phalaris arundinacea, Phragmites australis, Typha angustifolia, T. latifolia and Scirpus lacustris, were investigated in relation to their water-level zonation.2. The experiments demonstrated a large variation in these characteristics between the species.3. Propagule floating capacities range from 〈 1 h (S. lacustris) to 〉 1000 h (I. pseudacorus).4. Seed germination in a water-level gradient revealed two groups with respect to germination percentage - exposed soil species (I. pseudacorus, Phalaris arundinacea, Phragmites australis) and submerged soil species (T. angustifolia, T. latifolia).5. There were two contrasting types of seedling growth response to submergence and exposure: one group of species formed longest leaves under exposed conditions (Phalaris arundinacea, Phragmites australis, I. pseudacorus), and the other under submerged conditions (S. lacustris, T. latifolia, T. angustifolia).6. The results suggest that early life-history characteristics of the species relate to their locations in the riparian zonation: Phalaris arundinacea and Iris pseudacorus at the higher end, Phragmites australis intermediate, and Typha spp. and Scirpus lacustris at the lower end. Species occurring at lower locations show adaptations to (periodical) flooding of the soil (submersed germination and growth), while those from higher locations require prolonged exposed soil conditions to germinate and to survive the establishment stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00418.x
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  • 2
    Electronic Resource
    Electronic Resource
    A simple model for evaluating the costs and benefits of aquatic macrophytes (1999)
    Springer
    Hydrobiologia 415 (1999), S. 335-339 
    Details
    ISSN: 1573-5117
    Keywords: aquatic weeds; welfare; recreation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dense beds of aquatic macrophytes often cause nuisance to boaters and swimmers, and may obstruct water flow. Management of aquatic vegetation is, therefore, often aimed at reducing the biomass of the plants. If the nuisance is caused by exotic invasive species, there usually is no controversy with nature conservation aims. In shallow lakes, however, the interests of recreational users may conflict with nature conservation because the promotion of indigenous submerged vegetation is considered an important tool for lake restoration. Aiming at intermediate vegetation biomass seems a good solution for this controversy at first sight. However, we argue that such a compromise is often not the best policy from a welfare economic point of view. We present preliminary results of a graphical model, showing that the overall benefit for all ecosystem users may be minimal at the intermediate vegetation biomass. Furthermore, even if there is an optimal benefit at an intermediate macrophyte biomass, we argue that it is may not always be feasible to force the vegetation biomass to the desired level. Due to ecological feedback mechanisms, the system can have two alternative stable states: one with high vegetation biomass and one with little or no vegetation. It is concluded that it will often be better to realise a management strategy aimed at keeping some lakes (or parts of lakes) free of aquatic plants, whereas allowing others to be densely vegetated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003821314662
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  • 3
    Electronic Resource
    Electronic Resource
    Submerged vegetation development in two shallow, eutrophic lakes (1996)
    Springer
    Hydrobiologia 340 (1996), S. 115-120 
    Details
    ISSN: 1573-5117
    Keywords: macrophytes ; Potamogeton ; Charophytes ; eutrophication ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Submerged macrophyte vegetation in two shallow lakes in the Netherlands, Lake Veluwemeer and Lake Wolderwijd, has been affected by eutrophication in the late 1960's and 1970's. Recent changes in the vegetation occurred in the period following lake restoration measures. Between 1987 and 1993, the dominance of Potamogeton pectinatus decreased, while Charophyte ‘meadows‘ expanded over the same time interval. The pattern of change of the dominant macrophyte species might result from changes in the underwater light climate. Seasonally persistent clear water patches associated with the Chara meadows have been observed in the last few years. The interaction between submerged macrophyte vegetation succession and water transparency in the lakes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012742
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  • 4
    Electronic Resource
    Electronic Resource
    Biomanipulation in shallow lakes: state of the art (1997)
    Springer
    Hydrobiologia 342-343 (1997), S. 355-365 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The current state of biomanipulation was the subject of muchdiscussion at Shallow Lakes ‘95. This led to a workshop focusing onthe factors influencing the establishment of macrophytes and themechanisms responsible for their stability followingbiomanipulation. The purpose of the current paper is to distilcurrent knowledge on biomanipulation in shallow lakes gleaned fromdiscussions at the conference and recent literature.Biomanipulation should be used in the theoretical context of twoaltemative stable equilibria, as the extreme perturbation requiredto move from a phytoplankton dominated state to one dominated bymacrophytes. Understanding the nature of the factors and mechanismsresponsible for turbid water, is critical if biomanipulation is tobe appropriate. We suggest that with sufficient information,particular components of the fish community may be targeted andprecise figures for removal, designed to exceed critical thresholdvalues, may be set. Without this knowledge, a ‘play-safe’ strategyshould be adopted and at least 75% of the fish removed. Stockingwith piscivores may be a useful additional measure to fish removal.The principal objective of biomanipulation in shallow lakes is togenerate a period of clear water of sufficient length to allowmacrophytes to establish. To this aim, as well as for technicalreasons, biomanipulation is best undertaken in winter and earlyspring to generate clear water as early as possible in the season.In the cases where grazing is important, this coincides with thespring peak of Daphnia spp. Biomanipulation may have to berepeated if macrophytes do not colonise effectively within thefirst season. The factors responsible for the lag in response ofmacrophytes in some cases and the potential mechanisms contributingto the maintenance of clear water in macrophyte beds are discussed.From empirical data sets from many lakes, both a relative increasein the piscivorous fish stock and a reduction in nutrient levelsare thought to be important in stabilising the system in thelong-term. Whether biomanipulation may lead to alternativeequilibria (i.e. high diversity macrophyte communities withpiscivorous fish at high P) is unknown. Further study ofexceptional cases, theoretical modelling and development andanalysis of more long-term (〉10 years) case histories isrecommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017092802529
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  • 5
    Electronic Resource
    Electronic Resource
    Macroinvertebrate communities in relation to submerged vegetation in two Chara-dominated lakes (1997)
    Springer
    Hydrobiologia 342-343 (1997), S. 143-150 
    Details
    ISSN: 1573-5117
    Keywords: macrophytes ; macroinvertebrates ; Chara ; Potamogeton ; Chironomidae ; Gastropoda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Relationships between macroinvertebrates and the presence ofsubmerged vegetation were studied in two shallow eutrophiclakes inThe Netherlands, Lake Veluwemeer and Lake Wolderwijd. A shiftfromturbid water with sparse macrophyte cover (Potamogetonperfoliatus, Potamogeton pectinatus) towards clearwaterwith a dense cover of submerged vegetation (Chara spp.)hasbeen observed in the lakes over the past 10 years. RelativelylargeChara meadows (300–500 ha) have recently developed inbothlakes. The composition of macroinvertebrate fauna wasdetermined atsites varying in cover and dominant vegetation type bysamplingsediment and water during 1992 and 1994. Macrophyte biomass,sampling year and vegetation type were the major determinantsofmacroinvertebrate community composition. Valvatapiscinalis,Bithynia tentaculata, Gammarus tigrinus and Chironomussp.characterized the sites with high charophyte biomass, whereasPotamopyrgus antipodarum, Cladotanytarsus sp., Stictochironomus sp. dominated the samples with lowcharophytebiomass. Chara vegetation was different from Potamogeton sp. by showing lower densities of the midgelarvaeEinfeldia dissidens and Cricotopus gr. sylvestris.Seasonal variations in densities of the dominant molluscspecies(V. piscinalis, P. antipodarum) were closelyrelated tothe development of Chara biomass as well as toperiphytoncover on charophytes. Thus, changes of the light climate inbothlakes, which have led to an increase in colonization bysubmergedvegetation (particular Chara meadows), indirectly had alargeimpact on macroinvertebrate communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017094013491
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  • 6
    Electronic Resource
    Electronic Resource
    Classification of Danube Delta lakes based on aquatic vegetation and turbidity (1999)
    Springer
    Hydrobiologia 415 (1999), S. 187-191 
    Details
    ISSN: 1573-5117
    Keywords: submerged macrophytes ; lakes ; classification ; eutrophication ; remote sensing ; transparency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aquatic vegetation present in lakes in the delta of the River Danube was studied using field survey data and satellite image. Based on the spectral information from satellite images, three categories of lakes were distinguished: clear / macrophyte-dominated, intermediate and turbid / poorly vegetated. The satellite-based classification was consistent with vegetation cover and water transparency measured in the field. Cluster analysis of vegetation data from 235 relevés made in 22 lakes (1996-1998, each year in June) identified ten submerged vegetation types. The lakes were characterised by the frequency of occurrence of each vegetation type and ordinated, using Principal Components Analysis (PCA). A strong relationship appeared between the composition and density of aquatic vegetation and water transparency. Isolated lakes within the extensive beds of floating reed (plaur lakes) formed a separate group. Based on the ordination analysis, connectivity of lakes in the Danube Delta was concluded to be a major factor for the development of dense macrophyte vegetation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003856927865
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamics and stability of Chara sp. and Potamogeton pectinatus in a shallow lake changing in eutrophication level (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 335-342 
    Details
    ISSN: 1573-5117
    Keywords: transparency ; turbidity ; macrophytes ; logistic models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The submerged vegetation in Veluwemeer (The Netherlands) has shown large changes over the past 30 years. Potamogeton pectinatusL. remained present in the lake even during the hypertrophic period with total phospohorus (P) levels of about 0.6 mg P l-1. Furthermore, the data suggest that there may be one critical level of Secchi depth for the presence of charophytes (about 0.4 m), whilst there may be two critical P levels (0.3 mg P l-1for loss and 0.1 mg P l-1for their return). Logistic regression of detailed vegetation maps over the past 10 years (1988–1997) showed that occurrence of Charaspp. was positively related with spring averages of Secchi depth, while the occurrence of P. pectinatuswas slightly negatively related with Secchi depth. Both species had a negative sigmoid response to water depth. Sites without vegetation can be easily predicted by water depth and Secchi depth (97% for Charaand 99% for P. pectinatuscorrectly predicted cases). The sites where the species will appear are difficult to predict (50% for Charaand 3% for P. pectinatuscorrectly predicted cases, respectively). If the vegetation of a year prior to the census was included as variable, the predictability of the occurrence of P. pectinatusand Characan be improved to 71% and 53% correctly predicted cases, respectively. Grid cells which had been covered 1 year earlier with dense Charavegetation showed a different relationship with Secchi depth than the grid cells without earlier cover. Previous dense Chara(〉50% cover) stands returned always in the subsequent year independent on water depth or Secchi depth. Measurements in 1995 showed that dense charophyte beds decrease the turbidity to below 1 m-1(estimated light attenuation, K d ) in high summer, while outside the vegetation the water remained turbid (estimated K d ∼3 to 5 m−1). The positive effect on transparency, together with formation of dense propagule banks, may stabilize the Charavegetation. Dominance of P. pectinatusmay be restricted to turbid water, since Charaappears to be a stronger competitor than P. pectinatusin clear water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017074211970
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  • 8
    Electronic Resource
    Electronic Resource
    Impact of hydrodynamic changes on the zonation of helophytes (1996)
    Springer
    Aquatic ecology 30 (1996), S. 165-173 
    Details
    ISSN: 1573-5125
    Keywords: helophytes ; Phragmites ; Scirpus ; water level ; wave exposure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water movement has a strong impact on the development and persistence of helophyte stands along large water bodies. The decline ofScirpus andPhragmites stands in the Rhine-Meuse estuary (The Netherlands), due to changed hydrodynamic conditions (reduced tidal action, increased shoreline erosion), illustrates the effects of large-scale hydrological regulation. Hydrodynamic factors partly explain the distribution and composition of helophyte vegetation bordering the open water. A vertical zonation emerges during the stages of dispersal, germination, seedling establishment and adult growth of the plants. Differences between species may result in the occupation of different water-depth zones. Additionally, gradients of wave exposure result in a horizontal zonation along water bodies. Restrictions to helophyte development due to the hydrological regime and wave attack should be taken into account in wetland restoration studies. Water-level management, instead of a strict control of water levels, should be one of the key elements of water management in the future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272236
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  • 9
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    The role of water-level fluctuations in shallow lake ecosystems – workshop conclusions (2003)
    Springer
    Details
    Publication Date: 2003-01-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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  • 10
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    A statistical model predicting the occurrence and dynamics of submerged macrophytes in shallow lakes in the Netherlands (2003)
    Springer
    Details
    Publication Date: 2003-01-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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