Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Belang van dispersie bij herstel van waternatuur
Didderen, K. ; Verdonschot, P.F.M. - \ 2010
De Levende Natuur 111 (2010)3. - ISSN 0024-1520 - p. 24 - 29.
hydrobiologie - migratie - duikers - waterdieren - dispersie - macrofauna - hydrobiology - migration - culverts - aquatic animals - dispersion
Resultaten van herstelmaatregelen in wateren vallen vaak tegen, omdat de gewenste fauna niet (terug)komt. Een belangrijke reden hiervoor is dat (her)kolonisatie van waterfauna moet plaatsvinden vanuit bronpopulaties. Om meer te weten te komen over de dispersie van macrofauna en hun verplaatsing door het water is de barrièrewerking van duikers onderzocht. Dit leidt tot een aantal aanbevelingen.
Effecten van de rode Amerikaanse rivierkreeft op de vegetatie en macrofauna van sloten
Verdonschot, R.C.M. ; Schaik, H. van; Verdonschot, P.F.M. - \ 2009
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 42 (2009)20. - ISSN 0166-8439 - p. 36 - 39.
sloten - rivierkreeft - zoetwaterecologie - invasie - hydrobiologie - geïntroduceerde soorten - vegetatie - waterplanten - aquatische ecologie - macrofauna - ditches - crayfish - freshwater ecology - invasion - hydrobiology - introduced species - vegetation - aquatic plants - aquatic ecology
Exotische rivierkreeften breiden zich zeer sterk uit in Nederland. Wat voor effecten dit heeft op de inheemse waterplantenvegetaties en macrofauna is onbekend. In het kader van het project PLONS voerde Alterra daarom bij wijze van case-studie een experiment uit, waarin de invloed van de rode Amerikaanse rivierkreeft op slootecosystemen onderzocht is. In afgesloten cilinders zijn de veranderingen gevolgd die optraden in de biomassa van verschillende soorten waterplanten en de samenstelling van de macrofaunagemeenschap na introductie van de rivierkreeft. De invloed bleek variabel en soortspecifiek. Met name afstervende planten werden gegeten. Een aantal waterplanten raakte los door het omwoelen van de bodem. De macrofaunagemeenschap werd niet merkbaar beïnvloed. In het maag-darmstelsel van de kreeften werd met name organisch bodemmateriaal en plantenresten aangetroffen, wat een aanwijzing is dat de kreeften een rol spelen bij de afbraak van organisch materiaal. Exoten hoeven dus niet altijd een negatieve invloed te hebben op zoetwaterecosystemen.
Improved exposure assessment in Dutch ditches
Adriaanse, P.I. - \ 2009
hydrobiologie - ecosystemen - oppervlaktewater - drainage - drift - waterverontreiniging - sloten - uitspoelen - toxische stoffen - aquatische ecosystemen - kaderrichtlijn water - hydrobiology - ecosystems - surface water - water pollution - ditches - leaching - toxic substances - aquatic ecosystems - water framework directive
At present the exposure of the aquatic ecosystem to plant protection products is under-estimated in the Dutch registration procedure. Only spray drift is considered to be a relevant entry route in surface water. In reality drainage and surface run off may also be important routes. The EU registration procedure does take these routes into account. Construction of a Dutch ditch scenario with a 90th-percentile probability of occurrence exposure concentration, that considers the three relevant entry routes
Verslag Workshop Exotische zoetwaterkreeften en –krabben in Nederland Bilthoven, Sportvisserij Nederland, 19 juni 2008
Hoogenboom, H.J.C. - \ 2008
Bilthoven : s.n.
zoetwaterecologie - geïntroduceerde soorten - cancridae - krabben (schaaldieren) - rivierkreeft - schaaldieren - hydrobiologie - freshwater ecology - introduced species - crabs - crayfish - shellfish - hydrobiology
Verslag Workshop Exotische zoetwaterkreeften en –krabben in Nederland. Presentaties: 1. Bram Koese: Geschiedenis, herkenning en verspreiding van zoetwaterkreeften; 2. Menno Soes & Jos Spier: Ecologie en schade aan waterkwantiteit en –kwaliteit; 3. Tammo Bult: De commerciële mogelijkheden van de Wolhandkrab; 4. Bas van der Wal: discussie en aanbevelingen voor beleid en onderzoek
Lake restoration: successes, failures and long-term effects
Sondergaard, M. ; Jeppesen, E. ; Lauridsen, T.L. ; Skov, C. ; Nes, E.H. van; Roijackers, R.M.M. ; Lammens, E. ; Portielje, R. - \ 2007
Journal of Applied Ecology 44 (2007)6. - ISSN 0021-8901 - p. 1095 - 1105.
waterkwaliteit - herstel - meren - eutrofiëring - fosfor - effecten - aquatische ecologie - hydrobiologie - evaluatie - kaderrichtlijn water - nederland - denemarken - water quality - rehabilitation - lakes - eutrophication - phosphorus - effects - aquatic ecology - hydrobiology - evaluation - water framework directive - netherlands - denmark - nutrient loading reductions - shallow eutrophic lake - food-web manipulation - of-the-art - submerged macrophytes - danish lakes - planktivorous fish - temperate lakes - top-down - biomanipulation
1. Eutrophication constitutes a serious threat to many European lakes and many approaches have been used during the past 20–30 years to improve lake water quality. Results from the various lake restoration initiatives are diverse and the long-term effects are not well described. 2. In this study we evaluated data from more than 70 restoration projects conducted mainly in shallow, eutrophic lakes in Denmark and the Netherlands. Special focus was given to the removal of zooplanktivorous and benthivorous fish, by far the most common internal lake measure. 3. In more than half of the biomanipulation projects, Secchi depth increased and chlorophyll a decreased to less than 50% within the first few years. In some of the shallow lakes, total phosphorus and total nitrogen levels decreased considerably, indicating an increased retention or loss by denitrification. The strongest effects seemed to be obtained 4–6 years after the start of fish removal. 4. The long-term effect of restoration initiatives can only be described for a few lakes, but data from biomanipulated lakes indicate a return to a turbid state within 10 years or less in most cases. One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. 5. Synthesis and applications. Lake restoration, and in particular fish removal in shallow eutrophic lakes, has been widely used in Denmark and the Netherlands, where it has had marked effects on lake water quality in many lakes. Long-term effects ( > 8–10 years) are less obvious and a return to turbid conditions is often seen unless fish removal is repeated. Insufficient external loading reduction, internal phosphorus loading and absence of stable submerged macrophyte communities to stabilize the clear-water state are the most probable causes for this relapse to earlier conditions
Eutrophication constitutes a serious threat to many European lakes and many approaches have been used during the past 20-30 years to improve lake water quality. Results from the various lake restoration initiatives are diverse and the long-term effects are not well described. In this study we evaluated data from more than 70 restoration projects conducted mainly in shallow, eutrophic lakes in Denmark and the Netherlands. Special focus was given to the removal of zooplanktivorous and benthivorous fish, by far the most common internal lake measure. In more than half of the biomanipulation projects, Secchi depth increased and chlorophyll a decreased to less than 50% within the first few years. In some of the shallow lakes, total phosphorus and total nitrogen levels decreased considerably, indicating an increased retention or loss by denitrification. The strongest effects seemed to be obtained 4-6 years after the start of fish removal. The long-term effect of restoration initiatives can only be described for a few lakes, but data from biomanipulated lakes indicate a return to a turbid state within 10 years or less in most cases. One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. Synthesis and applications. Lake restoration, and in particular fish removal in shallow eutrophic lakes, has been widely used in Denmark and the Netherlands, where it has had marked effects on lake water quality in many lakes. Long-term effects (> 8-10 years) are less obvious and a return to turbid conditions is often seen unless fish removal is repeated. Insufficient external loading reduction, internal phosphorus loading and absence of stable submerged macrophyte communities to stabilize the clear-water state are the most probable causes for this relapse to earlier conditions.
Graadmeter natuurwaarde voor aquatische natuur : typen, indicatoren en monitoring van regionale wateren
Didderen, K. ; Verdonschot, P.F.M. - \ 2006
Wageningen : WOT Natuur & Milieu (WOt-werkdocument 34) - 164
hydrobiologie - sloten - waterlopen - zoetwaterecologie - natuurbescherming - oppervlaktewater - kwaliteit - meting - monitoring - referentienormen - nederland - aquatische ecosystemen - natuur - hydrobiology - ditches - streams - freshwater ecology - nature conservation - surface water - quality - measurement - reference standards - netherlands - aquatic ecosystems - nature
De graadmeter natuurwaarde geeft inzicht in de toename of afname van de totale soortendiversiteit. De graadmeter is afgestemd op deelgebieden die bestaan uit een combinatie van fysisch-geografische regio's, met daarbinnen natuurtypen. Per type wordt bekeken, in welke mate (indicator) soorten nog voorkomen. In dit WOT Natuur & Milieu project is gekeken op welke wijze de graadmeter voor aquatische natuur verbeterd kan worden
Ecologische beoordeling van visstand in beken en rivieren volgens nieuwe Europese methode EFI
Leeuw, J.J. de; Backx, J.J.G.M. ; Buijse, A.D. - \ 2006
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 39 (2006)17. - ISSN 0166-8439 - p. 54 - 56.
visbestand - zoetwatervissen - waterlopen - rivieren - ecologie - beoordeling - hydrobiologie - biologische monitoring - visstand - fishery resources - freshwater fishes - streams - rivers - ecology - assessment - hydrobiology - biomonitoring - fish stocks
In het kader van het Europese project FAME is een methode ontwikkeld om op eenvoudige wijze de ecologische toestand van beken en rivieren vast te stellen aan de hand van de visstand. Deze methode, European Fish Index (EFI) genaamd, voldoet aan de eisen van de Kaderrichtlijn Water. De EFI is een belangrijke toevoeging aan het Nederlandse instrumentarium, omdat de methode op Europese schaal toetsbaar is en voor allerlei typen beken en rivieren zinvolle vergelijkingen mogelijk maakt met (vrijwel) ongestoorde situaties die in Nederland zo goed als verdwenen zijn
Rehabilitating large regulated rivers; lowland river rehabilitation conference; Wageningen, 29 september - 3 oktober 2003
Buijse, A.D. ; Klijn, F. ; Leuven, R.S.E.W. ; Middelkoop, H. ; Schiemer, F. ; Thorp, J.H. ; Wolfert, H.P. - \ 2005
Stuttgart (Germany) : Schweizerbart (Archiv für Hydrobiologie Suppl. vol. 155, no. 1-4) - 738
stroomvlakten - herstel - rivierregulering - rivieren - hydrobiologie - floodplains - rehabilitation - river regulation - rivers - hydrobiology
Regulating rivers has reduced the natural dynamic processes, altered the landscape and its biodiversity. Along large rivers that serve manifold functions, rehabilitation attempts have recovered stretches or certain features, but complete restoration probably will be a utopia. Key questions of the conference were e.g. how sustainable or effective are we so far; how well did we assess our achievements; what are the costs and benefits, opportunities and constraints, the end-points? More than 50 oral contributions and over 40 posters were presented at the conference, 45 of which, from 14 different countries, are published as peer-reviewed papers in this issue
A growth model of the cockle (Cerastoderma edule L.) tested in the Ooosterschelde estuary (The Netherlands)
Rueda, J. ; Smaal, A.C. ; Scholten, H. - \ 2005
Journal of Sea Research 54 (2005)4. - ISSN 1385-1101 - p. 276 - 298.
bivalvia - groei - hydrobiologie - voortplanting - simulatiemodellen - nederland - oosterschelde - ecofysiologie - aquatische ecosystemen - growth - hydrobiology - reproduction - simulation models - netherlands - eastern scheldt - ecophysiology - aquatic ecosystems - mussel mytilus-edulis - gut-passage time - marennes-oleron - seasonal-variation - preingestive selection - ecophysiological model - seston concentration - variable conditions - particle selection - crassostrea-gigas
The authors present an ecophysiological model of the bivalve Cerastoderma edule that simulates individual growth and reproduction under ambient conditions in temperature and food availability in the Oosterschelde estuary, SW Netherlands. The model contains feedback loops in the uptake and metabolism of food and in the partitioning of carbon to the internal state variables: somatic tissue, storage, organic shell matrix and gametes. The model was calibrated for 24 parameters, based on random distributions of parameter values. This procedure includes an estimate of confidence intervals of the output variables. The simulated growth of shell length and animal wet and dry weight reflected the observed values of growth in the field for the period 1993–1997. The model is a tool for the integration of ecophysiological knowledge of this species and also for carrying-capacity studies of shellfish culture and for environmental management of populations in estuarine and coastal areas
We present an ecophysiological model of the bivalve Cerastoderma edule that Simulates individual growth and reproduction under ambient conditions in temperature and food availability in the Oosterschelde estuary, SW Netherlands. The model contains feedback loops in the uptake and metabolism of food and in the partitioning of carbon to the internal state variables: somatic tissue, storage, organic shell matrix and gametes. The model was calibrated for 24 parameters, based on random distributions of parameter values. This procedure includes an estimate of confidence intervals of the output variables. The simulated growth of shell length and animal wet and dry weight reflected the observed values of growth in the field for the period 1993-1997, The model is a tool for the integration of ecophysiological knowledge of this species and also for carrying-capacity studies of shellfish Culture and for environmental management of populations in estuarine and coastal areas. (c) 2005 Elsevier B.V. All rights reserved.
Ditch maintenance and biodiversity of macrophytes in the Netherlands
Peeters, E.T.H.M. - \ 2005
Verhandlungen Internationale Vereinigung für Theoretische und Angewandte Limnologie 29 (2005). - ISSN 0368-0770 - p. 185 - 189.
sloten - waterplanten - biodiversiteit - schoonmaken - hydrobiologie - soortendiversiteit - nederland - agrarische bedrijfsvoering - aquatische ecosystemen - agrobiodiversiteit - ditches - aquatic plants - biodiversity - cleaning - hydrobiology - species diversity - netherlands - farm management - aquatic ecosystems - agro-biodiversity
The first objective of the present study is to analyze the biodiversity of the aquatic ditch vegetation in relation to various envirotunental factors. A second objective is to test whether macrophyte biodiversity is highest at an intermediate level of ditch cleaning frequency
Verkenning van de waarde van historische gegevens voor het invullen van biologische referentietoestanden voor beken en sloten
Nijboer, R.C. ; Hoorn, M.W. van den; Verdonschot, P.F.M. - \ 2003
Wageningen : Alterra (Alterra-rapport 755) - 112
waterlopen - zoetwaterecologie - sloten - waterorganismen - waterplanten - referentienormen - geschiedenis - waterkwaliteit - hydrobiologie - nederland - macrofauna - streams - freshwater ecology - ditches - aquatic organisms - aquatic plants - reference standards - history - water quality - hydrobiology - netherlands
Met de inwerkingtreding van de Europese Kaderrichtlijn Water moet de ecologische kwaliteit van de Nederlandse wateren beoordeeld worden ten opzichte van de nagenoeg natuurlijke referentietoestand. In Nederland is dit een probleem, omdat de meeste wateren in meer of mindere mate door menselijk handelen beonvloed zijn. Een mogelijkheid voor het verkrijgen van informatie over de natuurlijke referentietoestand van wateren is het raadplegen van historische informatie uit een periode waarin de wateren nog in een meer natuurlijke staat verkeerden. Voorliggend rapport beschrijft de resultaten van een intensieve zoektocht in archieven naar historische informatie over de levensgemeenschappen in sloten en beken.
STOWA-systeem voor de ecologische beoordeling van brakke, binnendijkse wateren
Dam, H. van; Gotjé, W. ; Franken, R. ; Ietswaart, T. - \ 2002
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 35 (2002). - ISSN 0166-8439 - p. 6 - 25.
oppervlaktewater - brakwater - zoutgehalte - kwaliteit - waterkwaliteit - ecologie - beoordeling - evaluatie - karakterisering - karakteristieken - classificatie - hydrobiologie - aquatisch milieu - ecohydrologie - binnenwateren - aquatische ecosystemen - ecologische beoordeling - surface water - brackish water - salinity - quality - water quality - ecology - assessment - evaluation - characterization - characteristics - classification - hydrobiology - aquatic environment - ecohydrology - inland waters - aquatic ecosystems - ecological assessment
UItleg over een nieuw ecologisch beoordelingssysteem voor brakke binnenwateren, aansluitend bij de al bestaande STOWA-beoordelingssystemen voor andere watertypen. Op grond van het ecologisch functioneren en een geformuleerd ecologisch streefbeeld worden beïnvloedingsfactoren, karakteristieken en maatstaven onderscheiden, waarmee voor verschillende hoofdtypen en subtypen brakke binnenwateren een ecologisch profiel kan worden opgesteld. Zowel het zoutgehalte als de dynamiek blijken belangrijke differentiërende factoren tussen brakwatersystemen; morfologie en voedselrijkdom spelen een ondergeschikte rol
Referentiewaarden voor waterplanten in regionale oppervlaktewatersystemen; voorstudie natuurverkenning 2
Zuidhoff, A.C. ; Smits, N.A.C. ; Schaminée, J.H.J. ; Jansen, A.J.M. - \ 2002
Nieuwegein : Kiwa - 79
waterplanten - oppervlaktewater - watersystemen - hydrobiologie - sloten - waterlopen - laagveengebieden - nederland - aquatische ecosystemen - aquatische ecologie - natuurwaarde - vegetatie - aquatic plants - surface water - water systems - hydrobiology - ditches - streams - fens - netherlands - aquatic ecosystems
Onderhavige studie is een eerste praktische uitwerking voor vijf regionale watersystemen van de zogenaamde natuurwaarde-index. De natuurwaarde is in deze index gedefinieerd als een functie van de natuurkwaliteit en het areaal van een (water)systeem. Voor de natuurkwaliteit kunnen verschillende variabelen gebruikt worden, bijvoorbeeld de vegetatie (zoals in de voorliggende studie). De huidige natuurwaarde wordt bepaald als percentage van een referentiewaarde (uit het verleden). In deze studie wordt daarbij voor de huidige situatie gesproken van de ‘resterende natuurwaarde’, omdat in alle besproken regionale watersystemen sprake is van achteruitgang ten opzichte van de referentiewaarde. Het voorliggende onderzoek is eveneens bedoeld als een soort pilot-uitwerking van de Europese Kaderrichtlijn Water, welke per oppervlaktewatersysteem vraagt om indeling in vijf kwaliteitsklassen, waarbij vegetatie één van de kwaliteitsvariabelen vormt. De doelstelling van voorliggende studie is: Op basis van vegetatie voor vijf regionale watersystemen de resterende natuurwaarde in de huidige situatie bepalen ten opzichte van de referentiewaarde De vijf watersystemen waar het om gaat, zijn: * Vennen in hoog Nederland; * Beken in hoog Nederland; * Heuvellandbeken; * Plassen in het laagveengebied; en * Sloten in net laagveengebied
Interacties tussen visetende vogels en visserij: broodnijd een kwestie van dichtheidsafhankelijkheid
Leeuw, J.J. de - \ 2001
Limosa 74 (2001)2. - ISSN 0024-3620 - p. 69 - 72.
osmerus - visserij - visbestand - vogels - roofvogels - prooi - predator prooi verhoudingen - voedselketens - biomassa - biologische productie - populatiedichtheid - populatiedynamica - seizoenvariatie - biologische mededinging - concurrentie tussen dieren - voedingsgedrag - populatie-ecologie - dierecologie - hydrobiologie - ijsselmeer - fisheries - fishery resources - birds - predatory birds - prey - predator prey relationships - food chains - biomass - biological production - population density - population dynamics - seasonal variation - biological competition - animal competition - feeding behaviour - population ecology - animal ecology - hydrobiology - lake ijssel
Nuancering van het veel verbreide idee van concurrentie tussen visetende vogels enerzijds en sport- en beroepsvisserij anderzijds. Een reconstructie van het seizoensverloop van productie, consumptie en biomassa van Spiering (Osmerus eperlanus) in het IJsselmeer laat zien dat dichtheidsafhankelijke processen (groei en sterfte) een zodanige rol spelen dat van concurrentie nauwelijks sprake is; alleen de aalscholvers ondervinden in het late voorjaar schade van de beroepsvisserij op spiering in het vroege voorjaar
Ecologische streefbeelden voor stromende wateren Veluwe & Vallei
Jaarsma, N.G. ; Verdonschot, P.F.M. ; Nijboer, R.C. ; Hoorn, M.W. van den - \ 2001
Wageningen : Alterra (Alterra-rapport 377) - 107
waterkwaliteit - hydrobiologie - waterlopen - biologische monitoring - aquatische ecosystemen - ecohydrologie - gelderland - aquatische ecologie - beken - fauna - natuurontwikkeling - oppervlaktewater - vegetatie - Utrecht - Veluwe - Gelderse Vallei - water quality - hydrobiology - streams - biomonitoring - aquatic ecosystems - ecohydrology
Het project Ecologische streefbeelden voor stromende wateren Veluwe & Vallei heeft ten doel om toetsbare streefbeelden te ontwikkelen voor de stromende wateren in het beheersgebied van de waterschappen Veluwe en Vallei & Eem. Het is het vervolg van het project Maatweb stromende wateren Veluwe & Vallei. In het maatwebproject zijn de verschillende macrofaunagemeenschappen van de stromende wateren in het beheersgebied beschreven. Voor de in totaal dertien onderscheiden gemeenschapstypen uit dit rapport zijn negen streefbeelden ontwikkeld. Deze bestaan uit een beschrijving van de gewenste abiotische condities in combinatie met biotische indicatorsoorten van macrofauna en macrofyten. Daarnaast zijn de te verwachten vissen, amfibieën en vogels bij de streefbeelden vermeld. Selectie van de macrofauna heeft plaatsgevonden met behulp van literatuuronderzoek. Tevens zijn, door middel van statistische analyse, ecologische preferenties van macrofaunataxa voor een aantal voor het streefbeeld relevante milieuvariabelen bepaald.
Landbouwbestrijdingsmiddelen: waarom wijken toelatingsnormen af van MTR's
Appelman, J. ; Brock, T.C.M. - \ 2001
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 34 (2001)21. - ISSN 0166-8439 - p. 25 - 27.
pesticiden - landbouw - waterkwaliteit - waterverontreiniging - verontreinigingsbeheersing - normen - beleid - overheidsbeleid - oppervlaktewater - risico - risicoschatting - milieueffect - hydrobiologie - aquatische gemeenschappen - zoetwaterecologie - doseringseffecten - biotesten - toxiciteit - toxicologie - waterorganismen - ecotoxicologie - ecohydrologie - aquatische ecosystemen - aquatische ecologie - bestrijdingsmiddelen - milieu - pesticides - agriculture - water quality - water pollution - pollution control - standards - policy - government policy - surface water - risk - risk assessment - environmental impact - hydrobiology - aquatic communities - freshwater ecology - dosage effects - bioassays - toxicity - toxicology - aquatic organisms - ecotoxicology - ecohydrology - aquatic ecosystems
Uitleg over de totstandkoming van de door het College voor de Toelating van Bestrijdingsmiddelen (CTB) gehanteerde normen voor het bepalen van de risico's van bestrijdingsmiddelen voor het aquatisch ecosysteem, en hoe deze toelatingsnormen zich verhouden tot de in het waterkwaliteitsbeleid gehanteerde maximaal toelaatbare risiconiveaus (MTR's). Beide normen worden vergeleken met de waargenomen effecten van stoffen (insecticiden, herbiciden, fungiciden) in veldexperimenten. Daaruit blijkt dat de CTB-normen voldoende bescherming bieden voor waterorganismen
Nieuwe poelen: maatwerk gewenst
Creemers, R.C.M. ; Lenders, H.J.R. ; Stumpel, A.H.P. - \ 2000
De Levende Natuur (2000). - ISSN 0024-1520
plassen - habitats - aquatisch milieu - hydrobiologie - amphibia - natuurbescherming - ecologisch herstel - natuurtechniek - aquatische ecosystemen - ponds - aquatic environment - hydrobiology - nature conservation - ecological restoration - ecological engineering - aquatic ecosystems
Uit de bijdragen in dit themanummer blijkt duidelijk dat poelenaanleg inmiddels in grote delen van Nederland ingeburgerd is als middel om op kleinschalige wijze relatief snel natuurwinst te bereiken. Dit kan zowel binnen de bestaande natuurgebieden als daarbuiten, waarmee poelenaanleg een goed middel is om de verweving tussen natuur- en cultuurlandschap te versterken. De vraag dringt zich op of poelenprojecten aan de verwachtingen voldoen. Is het graven van standaard veedrinkpoelen de juiste weg of moeten er wellicht meer nieuwe inzichten ingepast worden?
Bezetting en kolonisatie van poelen door kamsalamander en bruine kikker in Twente
Sluis, T. van der; Bugter, R. - \ 2000
De Levende Natuur 101 (2000)4. - ISSN 0024-1520 - p. 107 - 111.
plassen - biotopen - habitats - aquatisch milieu - hydrobiologie - populatiedichtheid - populatiedynamica - populatie-ecologie - kolonisatie - dispersie - amphibia - kikkers - rana temporaria - inventarisaties - monitoring - natuurbescherming - salamanders - aquatische ecosystemen - populatiebiologie - overijssel - twente - ponds - biotopes - aquatic environment - hydrobiology - population density - population dynamics - population ecology - colonization - dispersion - frogs - inventories - nature conservation - aquatic ecosystems - population biology
Biomanipulation in the Netherlands : 15 years of experience
Meijer, M.L. - \ 2000
Agricultural University. Promotor(en): Marten Scheffer. - S.l. : S.n. - ISBN 9789058082268 - 208
eutrofiëring - hydrobiologie - waterbeheer - nederland - biologisch waterbeheer - aquatische ecosystemen - eutrophication - hydrobiology - water management - netherlands - biological water management - aquatic ecosystems
<p>Up to the mid 1950's Dutch lakes were characterised by clear water and luxurious macrophyte growth. In the 1960's eutrophication changed this situation and the lakes suffered from cyanobacterial blooms, turbid water and poor submerged vegetation. Restoration programmes were aimed at reducing the rates of the external phosphorus loading. Due to these measures, the nutrient- and chlorophyll-a concentrations decreased. The transparency of the water, however, increased only slightly. In the past one decade it has been recognised that eutrophication had given the turbid state various stabilising mechanisms through which it is very resistant to restoration measures centred on nutrient reduction.</p><p>A drastic reduction of the fish stock, known as biomanipulation, was suggested as an alternative approach. This thesis examines and evaluates the potential of biomanipulation as an additional restoration method and tries to understand and explain the mechanisms involved.</p><p><em>Alternative stable states (Chapter 2)</em></p><p>The turbidity of lakes is generally considered to be a smooth function of their nutrient status. However, models and observations in lakes suggest that over a range of nutrient concentrations, shallow lakes can have two alternative equilibria: a clear state dominated by aquatic vegetation, and a turbid state characterised by high algal biomass. This bi-stability has important implications for the possibilities of restoring eutrophied lakes. The turbid state is stabilised by planktivorous fish consuming large zooplankton, the grazer of algae and by benthivorous fish resuspending the bottom sediment in search for food. Nutrient reduction alone may have only a little impact on water clarity, but an ecosystem disturbance like fish stock reduction may contribute to factors to bring the lake back to a clear state. Once the clear water state has led to colonisation of the lakes with macrophytes, the macrophytes will stabilise the clear water state by various mechanisms. They may increase sedimentation and reduce resuspension, they may provide refuges for zooplankton against fish predation, in addition the macrophytes will compete with algae for nutrients, especially nitrogen and some macrophyte species may excrete allelopathic substances, that may inhibit algal growth.</p><p><em>The first Biomanipulation experiments (Chapter 3 and 4)</em></p><p>Biomanipulation in the Netherlands started with an experiment in small ponds (Chapter 3). Ten ponds of 0,1 ha were divided into two compartments; one half of each pond was stocked with 0+ cyprinids, the other served as a reference. This replicated, controlled experiment demonstrated significant differences in transparency, algae and zooplankton between compartments with fish and without fish. Despite the repeated addition of nutrients in the ponds no eutrophic conditions could be realised, probably due to increased sedimentation in the relatively small mesocosms. Although the aim of the experiment was to demonstrate the impact of planktivorous 0+ cyprinids on zooplankton and algae, the 0+ carp appeared to resuspend the bottom sediment as well, as the turbidity could not be explained by algal biomass only.</p><p>Lake Bleiswijkse Zoom was biomanipulated by dividing the small lake into two parts, and removing more than 75% of the original fish biomass from one part (Chapter 4). In the treated part the removal of bottom-stirring activity by benthivorous fish and the increase in zooplankton grazing causing low chlorophyll-a concentrations led to an increase of Secchi depth transparency from 20 cm to the bottom of the lake. Within two months the Characeae became abundant. The two parts differed significantly in inorganic suspended solids, algal biomass, transparency and total nutrient concentrations. Compared with the control compartment the number of fish species in the treated part increased.</p><p><em>Impact of benthivorous fish on turbidity (Chapter 5)</em></p><p>In two biomanipulated small lakes (Bleiswijkse Zoom and Noorddiep) the increase in transparency was not only caused by a decrease in algal biomass but also by a decrease in sediment resuspension by benthivorous fish. The biomass of benthivorous fish and the concentration of inorganic suspended solids were positively related. A model was used to calculate the impact of resuspended inorganic suspended solids on the turbidity. By combining these relations a direct effect of benthivorous fish on the Secchi depth was calculated. In addition, it is argued that the algal biomass was also indirectly influenced by removal of benthivorous fish, as the benthivorous fish prevented macrophytes from settling, whereas macrophytes were essential to keep the water clear.</p><p><em>Comparison of results with a Danish lake (Chapter 6)</em></p><p>In Chapter 6 the five year results of three biomanipulated Dutch lakes (Lake Zwemlust, Noorddiep and Bleiswijkse Zoom) are compared with one Danish biomanipulated lake (lake Vaeng). The fish stock reduction led in general to a low fish stock, low chlorophyll-a, increase in Secchi disk transparency depth and a high abundance of macrophytes. Large Daphnia became first abundant, but their density soon decreased due to food-limitation and predation by fish. The total nitrogen concentrations decreased due to N-uptake by macrophytes and enhanced denitrification. In lake Bleiswijkse Zoom the water transparency decreased and the clear water state was unstable. The fish stock increased and the production of young fish in summer was high. Clear water occurred only in spring . Large Daphnia decreased markedly in summer and the macrophytes dissappeared. Except in Bleiswijkse Zoom the water remained clear in all lakes during the first five years. In summer of the sixth year transparency decreased in the hypertrophic lake Zwemlust. Also in the less eutrophic lake Vaeng, a short-term turbid state (6 weeks) occurred in summer 1992 after a sudden collapse of the macrophytes. Deterioration of the water quality seems to start in summer and is apparently related to a collapse in macrophytes. At a low planktivorous fish stock the duration of the turbid state is shorter than in presence of a high planktivorous fish biomass which became apparent comparing Lake Vaeng with lake Zwemlust.</p><p><em>Development of fish communities after biomanipulation (Chapter 7)</em></p><p>The development of fish communities after biomanipulation has been studied in detail in three small lakes. In lake Zwemlust, after the biomanipulation, the introduced pike could not control the explosive growth of the introduced rudd. In lake Noorddiep and Bleiswijkse Zoom the fish population became more diverse. Bream and carp became less dominant and were partly replaced by roach and perch. The main predator pike-perch was strongly reduced and replaced by pike and perch. The share of piscivorous fish increased at all sites. The recruitment of young-of-the-year fish was similar or even higher in the clear overgrown areas than in the turbid water before the measures, but the recruitement of young -of-the-year to older species differed between the species. Predation by pike and perch could not control the young-of-the-year cyprinids, but their predation may have contributed to the shift form bream to roach, because of selective predation on bream in the open water, while roach was hiding in the vegetation. The macrophytes provided new refugia and feeding conditions that favour roach and perch, but offer relatively poor survival conditions for bream and carp.</p><p><em>Biomanipulation on a large scale (Chapter 8)</em></p><p>The drastic fish removal in Lake Wolderwijd (2670 ha) showed that also in a very large lake biomanipulation cause water clarity to increase. In this large lake in total 425 tons of fish were removed, i.e. ca. 75% of the original fish stock. In addition 625.000 specimen of 0+ pike were added to the lake. The success of biomanipulation in the lake was transient. In spring 1991 the transparency of the water increased as a result of grazing by <em>Daphnia galeata</em> . The clear-water phase lasted for only six weeks. Macrophytes did not respond as expected and most of the introduced young pike died. However, from 1991 to 1993 the submerged vegetation gradually changed. Chara began to spread over the lake (28 ha in 1991 to 438 ha in 1993). The water over the Chara meadows was clear, probably as a result of increased net sedimentation in these areas, due to reduced resuspension.</p><p><em>Evaluation of Biomanipulation Projects (Chapter 9)</em></p><p>Evaluation of eighteen biomanipulation projects showed that biomanipulation can be a very effective method to increase the transparency of the water in lakes. In almost half of all projects a return to the clear water state was obtained and in only ten per cent of the projects the biomanipulation failed to cause an increase in the Secchi depth. In all other cases, the water transparency increased significantly. The increase in Secchi depth was significantly stronger than the general trend observed in Dutch lakes where no measures have been taken. The improvement in Secchi depth and chlorophyll-a was also more marked in lakes where only the phosphorus load had been reduced.</p><p>The critical factor for obtaining clear water was the extent of the fish reduction in winter. Significant effects were observed only after &gt; 75% fish reduction. Success seems to require substantial fish reduction. In such strongly biomanipulated lakes, wind resuspension of the sediment did not influence water clarity. No conclusions can be drawn with respect to the possible negative impact of cyanobacteria or <em>Neomysis</em> on grazing by <em>Daphnia</em> and consequently on water clarity. In all lakes, with an additional phosphorus loading reduction, the fish stock had been reduced less drastically. In these lakes, the effect on transparency was less pronounced than in the lakes with &gt; 75% fish removal.</p><p>Daphnia grazing seems responsible for spring clear water in all but one clear lakes. The factors that determine the clear water in summer are less obvious and more diverse, but a high macrophyte cover seems to play an important role in all the lakes.</p><p>The decrease of the Secchi depth over the years in almost all manipulated eutrophic lakes supports the idea that the clear, vegetation dominated state is not stable at high nutrient conditions. However, the return time to the turbid water state is long ( &gt; 8 years). As we have not applied biomanipulation in mesotrophic lakes, we could not investigate if under those conditions the clear water state would be stable on the long term. For the stability of the clear water state it would be good to have a large piscivorous population. Under the present condition in The Netherlands, with "constant" waterlevels, scarce emergent vegetation and relatively high nutrient concentrations, no dense population of piscivores are likely to develop.</p><p><em>Development of ideas (Chapter 10)</em></p><p>How our ideas have evolved on biomanipulation on biomanipulation in the past fifteen years is subject of the last chapter. Biomanipulation seems a more effective tool than it was thought when it was started, especially for eutrophic lakes. Expected negative aspects like increase in inedible algae have hardly been found. Also the ideas on the working of biomanipulation have evolved. In accordance with earlier ideas, the increase in water clarity mostly occurs in spring and <em>Daphnia</em> grazing seems crucial for this spring clear-water phase. Reduced resuspension after removal of benthivores has been shown to be important in three out of the eighteen lake studies. However, in most lakes the fish removal caused a reduction in nutrient concentrations, which may have been caused by a reduction in the benthivores or by an increase of bottomalgae.</p><p>According to early views, colonisation of macrophytes seems crucial for maintaining the clear water in summer. In lakes without macrophyte growth, the water frequently became turbid again in summer, if predation of 0+ fish on <em>Daphnia</em> was high. At least a coverage of 50-&gt;70% of the lake with macrophytes is required to keep the water clear in the whole lake. At lower coverage only locally clear water above the macrophytes may be achieved. Macrophytes induce many changes in the ecosystem, which help stabilising the clear water state. The expected increase of piscivore control of 0+ fish has not been found in Dutch lakes. Rather, the macrophytes seem to stimulate the production of 0+ fish in eutrophic lakes. Macrophytes can provide refuge for zooplankton, but this effect may be small if high densities of 0+ fish or Neomysis are present within the vegetation. In large, shallow lakes reduced resuspension and increased sedimentation between the macrophytes may significantly contribute to the water clarity. Furthermore, nitrogen limitation of the algal growth has proven to be important in some lakes, but in others a strong reduction of the chlorophyll-a nutrient ratio's suggest that other factors than nutrient limitation are responsable for the low algal biomasses in presence of plants. Those can be related to zooplankton grazing, allelopathic effects or increase of filtering zebramussels.An increase in benthic algae may play a role in this too, but there is not yet much knowledge on this aspect.</p><p><em>Implication for the water quality manager</em></p><p>This thesis shows that biomanipulation can be a very effective restoration method provided the fish biomass reduction is substantial. Indeed, biomanipulation seems to be more effective in increasing water transparency than reducing the phosphorus load. Biomanipulation may even lead to a substantial reduction of the nutrient concentrations in the water column. Provided that a substantial fish reduction is carried out, the system may shift to a clear water state even at high nutrient concentrations.</p><p>The costs of biomanipulation are low compared to the costs of phosphorus reduction measures (Boers et al, 1997). Although this study shows that in eutrophic lakes no long-term success can be obtained, the long return time to the turbid state implies that even in highly eutrophic lakes, where the clear state is not stable, biomanipulation may be an cost-effective management strategy, as in some lakes it may suffice to reduce the fish stock drastically once every five year.</p><p>However, biomanipulation may not work in all conditions. In open systems with a a lot of boats, it may be difficult to remove a substantial part of the fish stock. In those lakes repeated fish reduction may also have effect (as shown in Finland and Sweden), but in The Netherlands there is not yet much experience with this method. Furthermore in lakes with a very high density of inedible cyanobacteria, and a high resuspension of sediment the potential of the method is still to be tested.</p><p>With future applications attention should be paid to removal of more than 75% of the fish stock, removal of small fish in adjacent ditches, removal or disturbance of spawning fish to reduce the production of 0+ fish and to reservation of money for additional fisheries. Furthermore the potential for macrophyte growth should be investigated beforehand, and if necessary macrophyte stimulating measures should be taken, like reducing the water depth or addition of oospores or seeds of plants.</p><p>The challenge for the future is to create a shift to the clear water state by means of biomanipulation in more open systems, in lakes with a high density of inedible cyanobacteria or floating layers of cyanobacteria and in lakes with a high resuspension of loose sediment.</p>
Purification function of wetlands : spatial modelling and pattern analysis of nutrient reduction in the Liaohe Delta
Li, X. - \ 2000
Agricultural University. Promotor(en): Arnold Bregt; R.H.G. Jongman. - S.l. : S.n. - ISBN 9789058081650 - 122
waterzuivering - wetlands - landschap - voedingsstoffen - afvalwaterbehandeling - hydrobiologie - fysische modellen - geografische informatiesystemen - china - natuur - water treatment - landscape - nutrients - waste water treatment - hydrobiology - physical models - geographical information systems - nature
<p>The eutrophication of coastal seawater has been a serious problem for the last two decades in Eastern China. The purification function of natural wetlands at big river deltas provides a potential solution to cut down nutrient input into the sea. The purpose of this research is to give a quantified evaluation as to what extent the natural wetland can be used as a treatment system for nutrient enriched river water. By integrating processed-based mathematical models with GIS, a number of valuable results and conclusions have been obtained through this study.<p>A spatial simulation model has been established based on the field and literature data, to simulate the nutrient reduction and its distribution in the wetland of Liaohe Delta, China. A non-linear regression model is used for the nutrient reduction in the canal system, while Mander-&-Mauring's linear regression model is adopted for the reed fields. According to the simulation result, there is a "mutual compensation" for the nutrient reduction in the reed system and canal system, so that the total reduction rate remains relatively stable in spite of the input concentration change at the pumping station. It is 66% for total nitrogen and 90% for soluble reactive phosphorus. In combination with the canals, the present 80,000 ha of reed can remove about 3,200-4,000 tons of nitrogen and 80 tons of soluble reactive phosphorous during the irrigation period each year. But this is only 1/10 of its total reduction capacity, with water being the limitation factor.<p>Four spatial combinations of reed, canals and pumping stations are designed to investigate the effect of pattern on nutrient reduction: 1) canal density, 2) reed area size, 3) reed shrinking pattern and 4) pumping station position. The simulation results indicate that each factor brings less than 10% deviation in total nutrient reduction rate, though the absolute reduction quantity can be different. If the reed area is stable, it is better to remain a low canal density, and keep the pumping station near the border of the reed area. Generally speaking, smaller reed area close to the pumping station is more efficient in nutrient reduction than larger, scattered ones. The shrinkage pattern of land transformation for the reed is most recommended in keeping a high reduction rate for the nutrients. The present reed area can accept at least 4 times more water in spring.<p>The relationship between landscape structure and nutrient reduction is measured with the help of some landscape indices. Not all the landscape pattern indices are closely related to the nutrient reduction of the wetland system. Therefore the ability of pattern indices to characterize the effect of pattern change on function is rather limited. Redundancies also exist among similar indices. Landscape indices should be chosen according to the purpose of the study, based on the criteria of simplicity, generality and ecological meaningfulness.<p>The research work is a combination of landscape ecology, wetland ecology and GIS technology. The spatial model developed is also applicable for other areas with similar situations. The results will contribute to a sustainable landscape planning in the study area. It is concluded that the natural wetlands have a great potential to be used for reducing nutrient input into the sea.<br/>
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