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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Improving communication and validation of ecological models : a case study on the dispersal of aquatic macroinvertebrates
    Augusiak, Jacqueline A. - \ 2016
    Wageningen University. Promotor(en): Paul van den Brink, co-promotor(en): V. Grimm. - Wageningen : Wageningen University - ISBN 9789462579378 - 192
    macroinvertebrates - aquatic invertebrates - ecological modeling - ecology - models - dispersal - environmental policy - macroinvertebraten - waterinvertebraten - ecologische modellering - ecologie - modellen - verspreiding - milieubeleid

    In recent years, ecological effect models have been put forward as tools for supporting environmental decision-making. Often they are the only way to take the relevant spatial and temporal scales and the multitude of processes characteristic to ecological systems into account. Particularly for environmental risk assessments of pesticides the potential benefits of including modelling studies were recognized and a dialogue between different stakeholder groups was opened. Representatives from academia, pesticide-producing industries, and regulators are nowadays discussing their needs, possibilities, and ways of implementation for improving the use and usefulness of such models. However, it quickly became evident that not all involved parties possess the same background knowledge in regards to modelling terminology and model quality understanding. Proper communication of a given model's structure, robustness, and soundness is crucial to render a model of real use to the decision-making. Doubts about a model's quality and mode of operation may lead to an immediate rejection of the conclusions drawn from its estimations.

    In this thesis, we addressed this point of concern, and performed a literature review focusing on aspects surrounding quality assessments, validation, and communication of models. "Validation" was identified as a catch-all term, which is thus useless for any practical purpose. Based on the review, we developed a framework that splits the seemingly blurry process into associated components and introduce the term ‘evaludation’, a fusion of ‘evaluation’ and ‘validation’, to describe the entire process of assessing a model's quality and reliability. Considering the iterative nature of model development, the modelling cycle, we identified six essential elements of evaludation: (i) ‘data evaluation’ for scrutinising the quality of numerical and qualitative data used for model development and testing; (ii) ‘conceptual model evaluation’ for examining the simplifying assumptions underlying a model's design; (iii) ‘implementation verification’ for testing the model's implementation in equations and as a computer programme; (iv) ‘model output verification’ for comparing model output to data and patterns that guided model design and were possibly used for calibration; (v) ‘model analysis’ for exploring the model's sensitivity to changes in parameters and process formulations to make sure that the mechanistic basis of main behaviours of the model has been well understood; and (vi) ‘model output corroboration’ for comparing model output to new data and patterns that were not used for model development and parameterisation.

    In a subsequent step, we used the evaludation framework to re-evaluate and adjust the documentation framework TRACE (TRAnsparent and Comprehensive Eco- logical modelling; Schmolke et al. 2010), a general framework for documenting a model's rationale, design, and testing. TRACE documents should provide convincing evidence that a model was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. TRACE documents link the science underlying a model to its application, thereby also linking modellers and model users, for example stakeholders, decision makers, and developers of policies. TRACE thus becomes a tool for planning, documenting, and assessing model evaludation, which includes understanding the rationale behind a model and its envisaged use.

    To provide an example of the measures that can be taken to increase general trust in a model's design and output, we chose MASTEP (Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides) for a case study. MASTEP is an individual-based model used to describe the effects on and recovery of the water louse Asellus aquaticus after exposure to an insecticide in pond, ditch, and stream scenarios. The model includes processes of mortality of A. aquaticus, life history, random walk between cells and density dependence of population regulation. One of the submodels receiving particular criticism was the random walk procedure and the uncertainty attached to the parameters used. The parameters were estimated based on experimental studies performed under very limiting conditions.

    We designed and performed experiments to derive more precise parameters and to better understand the movement behaviour of this freshwater isopod. The experimental procedure that we developed employed video tracking of marked individuals that were introduced alone or as part of a group of unmarked individuals into arenas of approximately 1m2 in size. We recorded the paths of the marked individuals under a set of different conditions, i.e. presence or absence of food or shelter, population density, and after sublethal exposure to chlorpyrifos and imidacloprid. Based on the experimental findings, we refined the movement modelling procedure used in MASTEP to derive more realistic dispersal estimates, with which we revisited a modelling study performed previously by Galic et al. (2012). In this study, the effects of pesticide application timing on population dynamics and recovery times were tested and compared to outcomes from previous versions. It was furthermore possible to integrate an increased level of environmental complexity that could not be addressed before due to a lack of data. Compared to former versions of the population model, recovery times did not change significantly when the same movement parameters were applied to all simulated individuals. This indicates that the previous assumptions already yielded robust estimations. Accounting for life stage dependent movement restraints, though, delayed recovery when exposure occurred shortly before a reproduction cycle. Based on these findings, it was concluded that an increase of ever more realism and environmental complexity in modelling studies needs to be done carefully on a case-by-case basis. Increased realism in models can introduce an unwarranted increase in model complexity and uncertainty, which is not always supporting an improved credibility level of a model.

    Despite the need for basic ecological research for more comprehensive ecological models, we further argue that a modelling study in general can benefit greatly from an improved plan that considers communication needs from the start. Considering such needs early on can help develop a time- and cost-saving strategy for model testing and data collection, while providing a thorough understanding of a model's underlying mechanisms across several layers of stakeholder groups.

    Assessing recovery potential of aquatic macroinvertebrate populations using ecological models
    Galic, N.G. - \ 2012
    Wageningen University. Promotor(en): Paul van den Brink, co-promotor(en): Hans Baveco. - S.l. : s.n. - ISBN 9789461732286 - 247
    macrofauna - waterinvertebraten - populatiedynamica - pesticiden - ecosysteemdiensten - ecologische risicoschatting - modellen - agro-ecosystemen - macrofauna - aquatic invertebrates - population dynamics - pesticides - ecosystem services - ecological risk assessment - models - agroecosystems
    Doordat de groeiende wereldbevolking een steeds grotere druk op natuurlijke ecosystemen legt, wordt de vraag naar een goede methode voor het beoordelen van de mogelijkheid tot herstel van een systeem steeds groter. Dit is vooral relevant voor agrarische ecosystemen welke traditioneel als functie hebben om voedsel voor de menselijke populatie te produceren. Agrarische ecosystemen leveren echter ook andere ecosysteemdiensten zoals omzettingen van nutriënten, bestuiving, het op peil houden van een bepaalde bodemkwaliteit en structuur, maar ook esthetische en recreatieve diensten, waarvan de duurzaamheid moet worden gewaarborgd.
    Predicting the response of aquatic invertebrates to stress using species traits and stressor mode of action
    Rubach, M.N. - \ 2010
    Wageningen University. Promotor(en): Paul van den Brink, co-promotor(en): D.J. Baird; S.J. Maund. - [S.l. : S.n. - ISBN 9789085857679 - 194
    waterarthropoden - waterinvertebraten - insecticiden - chloorpyrifos - kenmerken - toxiciteit - ecotoxicologie - ecologische risicoschatting - gevoeligheid - aquatic arthropods - aquatic invertebrates - insecticides - chlorpyrifos - traits - toxicity - ecotoxicology - ecological risk assessment - sensitivity
    How much stress can one take? It depends, on the combination of your mental and physical characteristics (traits), but it’s hard to predict. Chemicals can have devastating effects on ecosystems and they can cause stress in animals and plants. Thus, their risk for ecosystem health needs to be assessed, before use. Species show very different tolerances to the diversity of chemicals due to the combination of both their traits and the molecular mechanism of causing damage in the cell. The challenge lies in finding the relevant species traits and their link to the chemical. In this project an insecticide and 15 freshwater species were used to develop and test a framework for the prediction of responses to stress using traits. Time dependent processes, such as exposure patterns, uptake and excretion of the chemical, but also compensation, detoxification and thresholds were investigated and modelled. These processes were successfully linked to several traits such as size, lipid content, breathing strategy, exoskeleton thickness and evolutionary descent.
    The effect of pulse stimulation on marine biota - Research in relation to ICES advice - Progress report on the effects on benthic invertebrates
    Marlen, B. van; Haan, D. de; Gool, A.C.M. van; Burggraaf, D. - \ 2009
    IJmuiden : IMARES (Report / IMARES Wageningen UR C103/09) - 53
    waterinvertebraten - aquatische gemeenschappen - visserij - mariene biologie - pulsvisserij - aquatic invertebrates - aquatic communities - fisheries - marine biology - pulse trawling
    In response to ecosystem related concerns about bottom trawling and particularly beam trawling that were raised by various scientists in the last decades of the previous century. Many studies were done in the 1970s and 1980s, but in spite of promising results commercial uptake was lacking. The development of pulse trawling was again taken up in the 1990s by a private company (Verburg:Holland Ltd.) in The Netherlands. Meanwhile questions about ecosystem effects of introducing pulse beam trawling in the Dutch flatfish fishery were raised by the European Scientific, Technical and Economic Committee for Fisheries (STECF) and the Inter: national Council for the Exploration of the Sea (ICES) and discussed at the meeting of the ICES Working Group on Fishing Technology and Fish Behaviour (WGFTFB) in 2006. These questions led to field strength measurements in situ onboard the commercial beam trawler, and research on the effects of pulse stimulation on cod (Gadus morhua L.), and elasmobranch fish.
    Habitat variation and life history strategies of benthic invertebrates
    Franken, R.J.M. - \ 2008
    Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Edwin Peeters. - [S.l.] : S.n. - ISBN 9789085048688 - 158
    waterinvertebraten - benthos - waterlopen - milieufactoren - zoetwaterecologie - habitats - levensgeschiedenis - snelheid - substraten - gammarus pulex - plecoptera - oevervegetatie - aquatic invertebrates - benthos - streams - environmental factors - freshwater ecology - habitats - life history - velocity - substrates - gammarus pulex - plecoptera - riparian vegetation
    The thesis considers two key aspects of lotic freshwater ecosystems, the physical microhabitat and organic matter dynamics. The first part focuses on the indirect effects of light and riparian canopy cover on shredder growth and productivity through the effect on the nutritional quality of the food source. The second part addresses the nature of differences in response to physical habitat structure and current velocity in common species of shredders. Three invertebrate shredder-detritivore species were selected as study organisms: the freshwater shrimp Gammarus pulex, the freshwater louse Asellus aquaticus and the stonefly Nemoura cinerea
    Sediment stability and macroinvertebarte composition
    Siedlecka, A.M. ; Hoorn, M.W. van den; Verdonschot, P.F.M. - \ 2007
    klimaatverandering - waterinvertebraten - doorspoelen - sediment - macroinvertebraten - climatic change - aquatic invertebrates - flushing - sediment - macroinvertebrates
    Poster about the effects of climate change on aquatic fauna, especially the macroinvertebrates
    Avoidance of polycyclic aromatic hydrocarbon-contaminated sediments by the freshwater invertebrates Gammarus pulex and Asellus aquaticus
    Lange, H.J. de; Sperber, V. ; Peeters, E.T.H.M. - \ 2006
    Environmental Toxicology and Chemistry 25 (2006)2. - ISSN 0730-7268 - p. 452 - 457.
    waterverontreiniging - sediment - stroomvlakten - besmetters - toxicologie - polycyclische koolwaterstoffen - waterinvertebraten - waterdieren - gammarus pulex - asellus aquaticus - waterbodems - ecotoxicologie - water pollution - sediment - floodplains - contaminants - toxicology - polycyclic hydrocarbons - aquatic invertebrates - aquatic animals - gammarus pulex - asellus aquaticus - water bottoms - ecotoxicology - oligochaete lumbriculus-variegatus - induced community tolerance - rhine-meuse delta - pollution - toxicity - amphipod - metals - food - earthworm - responses
    Contamination of sediments is a serious problem in most industrialized areas. Sediments are often contaminated with trace metals and organic contaminants like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Bioassays are often used to determine the effect of contaminants on biota. However, survival or growth may not be the most sensitive endpoints. Behavioral changes often occur at much lower concentrations. Our study aimed to assess the effect of PAHs on habitat choice of two common freshwater invertebrates, the amphipod Gammarus pulex and the isopod Asellus aquaticus. We spiked clean field sediment with a mixture of four PAHs, fluoranthene, pyrene, chrysene, and benzo[k]fluoranthene, to a total concentration of 30 mg PAH/kg dry weight. Both species were offered a choice between PAH-spiked sediments and clean sediments in laboratory experiments. Results show that both species avoid PAH-spiked sediment. Origin of the population, either from a clean reference site or from a polluted site, did not affect habitat choice of either species
    Characterisation of pristine Polish river systems and their use as reference conditions for Dutch river systems
    Nijboer, R.C. ; Verdonschot, P.F.M. ; Piechocki, A. ; Tonczyk, G. ; Klukowska, M. - \ 2006
    Wageningen : Alterra (Alterra-rapport 1367) - 221
    rivieren - ecologie - waterlopen - meren - waterinvertebraten - biodiversiteit - polen - nederland - kwaliteitsnormen - rivers - ecology - streams - lakes - aquatic invertebrates - biodiversity - quality standards - poland - netherlands
    A central feature of the European Water Framework Directive are the reference conditions. The ecological quality status is determined by calculating the distance between the present situation and the reference conditions. To describe reference conditions the natural variation of biota in pristine water bodies should be measured. Because pristine water bodies are not present in the Netherlands anymore, water bodies (springs, streams, rivers and oxbow lakes) in central Poland were investigated. Macrophytes and macroinvertebrates were sampled and environmental variables were measured. The water bodies appeared to have a high biodiversity and a good ecological quality. They contain a high number of rare macroinvertebrate species. There are only few species that can not occur in the Netherlands, but their abundances were low. The Polish water bodies are suitable to describe reference conditions for similar Dutch water types. The data resulting from this project can be used to update the descriptions of reference conditions in the `Handboek Natuurdoeltypen¿or to develop the descriptions for the Water Framework Directive types.
    Periphyton: ecology, exploitation and management
    Azim, M.E. ; Verdegem, M.C.J. ; Dam, A.A. van; Beveridge, M.C.M. - \ 2005
    Wallingford, UK : CAB International - ISBN 9780851990965 - 319
    aquacultuur - detritus - micro-organismen - waterinvertebraten - aquatisch milieu - waterorganismen - kringlopen - voedingsstoffen - koolstofcyclus - koolstofvastlegging - aquatische ecosystemen - aquaculture - detritus - microorganisms - aquatic invertebrates - aquatic environment - aquatic organisms - cycling - nutrients - carbon cycle - carbon sequestration - aquatic ecosystems
    Periphyton, as described in this book, refers to the entire complex of attached aquatic biota on submerged substrates, including associated non-attached organisms and detritus. Thus the periphyton community comprises bacteria, fungi, protozoa, algae, zooplankton and other invertebrates. Periphyton is important for various reasons: as a major contributor to carbon fixation and nutrient cycling in aquatic ecosystems; as an important source of food in aquatic systems; as an indicator of environmental change. It can also be managed to improve water quality in lakes and reservoirs; it can greatly increase aquaculture production; it can be used in waste water treatment. The book provides an international review of periphyton ecology, exploitation and management. The ecology part focuses on periphyton structure and function in natural systems. The exploitation part covers its nutritive qualities and utilization by organisms, particularly in aquaculture. The final part considers the use of periphyton for increasing aquatic production and its effects on water quality and animal health in culture systems.
    Uptake of sediment-bound bioavailable polychlorobiphenyls by benthivorous carp (Cyprinus carpio)
    Moermond, C.T.A. ; Roozen, F.C.J.M. ; Zwolsman, J.J.G. ; Koelmans, A.A. - \ 2004
    Environmental Science and Technology 38 (2004)17. - ISSN 0013-936X - p. 4503 - 4509.
    sediment - biologische beschikbaarheid - polychloorbifenylen - benthos - karper - zoetwatervissen - meren - waterinvertebraten - chemicaliën - opname (uptake) - organische scheikunde - ecotoxicologie - waterbodems - sediment - bioavailability - polychlorinated biphenyls - benthos - carp - freshwater fishes - lakes - aquatic invertebrates - chemicals - uptake - organic chemistry - ecotoxicology - water bottoms - hydrophobic organic contaminants - aquatic food webs - contact time - pore-water - ingested sediment - extraction - lake - pollutants - fish
    It is unclear whether accumulation of sediment-bound chemicals in benthivorous fish depends on the degree of sequestration in the sediment like it does for invertebrates. Here, we report on the potential of slow and fast desorbing sediment-bound polychlorobiphenyl (PCB) fractions for accumulation in carp (Cyprinus carpio) in lake enclosures treated with different nutrient doses
    It is unclear whether accumulation of sediment-bound chemicals in benthivorous fish depends on the degree of sequestration in the sediment like it does for invertebrates. Here, we report on the potential of slow and fast desorbing sediment-bound polychlorobiphenyl (PCB) fractions for accumulation in carp (Cyprinus carpio) in lake enclosures treated with different nutrient doses. Routes of PCB uptake were quantitatively evaluated for 15 PCBs (log K-0W range 5.6-7.8) using model analysis. Fast-desorbing PCB fractions in the sediment were defined as the ratio of 6-h Tenax-extractable to (total) Soxhlet-extractable concentrations. These fractions varied between 4 and 22% and did not show a clear trend with log K-0W. However, bioaccumulation of PCBs in carp correlated much better with Tenax-extractable concentrations than with total-extractable concentrations. Nutrient additions in the enclosures had a positive effect on PCB accumulation. Model results show that PCB uptake in carp can be explained from (1) uptake through invertebrate food, (2) uptake from fast-desorbing fractions in ingested sediments, and (3) uptake from water, where PCBs are in partitioning equilibrium with fast-desorbing fractions. The main implication of this research is that fast-desorbing PCB fractions in sediments have great predictive potential for bioaccumulation in benthivorous fish.
    Sediment pollution and predation affect structure and production of benthic macroinvertebrate communities in the Rhine-Meuse delta, The Netherlands
    Lange, H.J. de; Jonge, J. de; Besten, P.J. den; Oosterbaan, J. ; Peeters, E.T.H.M. - \ 2004
    Journal of the North American Benthological Society 23 (2004)3. - ISSN 0887-3593 - p. 557 - 579.
    waterverontreiniging - waterinvertebraten - zware metalen - sediment - besmetters - stroomvlakten - predatie - toxicologie - nederland - ecotoxicologie - rijn - maas - zuid-holland - water pollution - aquatic invertebrates - heavy metals - sediment - contaminants - floodplains - predation - toxicology - netherlands - ecotoxicology - river rhine - river meuse - zuid-holland - saint-francois quebec - acid volatile sulfide - invertebrate community - toxicological factors - population-dynamics - floodplain lakes - fresh-water - availability - bioavailability - extraction
    Most floodplain sediments of the rivers Rhine and Meuse in The Netherlands are moderately polluted with trace metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other chemicals. The effects of these sediment-bound contaminants on the productivity of benthic macroinvertebrates are unclear. Sixteen locations along a pollution gradient were investigated in creeks in the Biesbosch floodplain area. Sediment samples were analyzed for bulk sediment characteristics and contaminants (total and bioavailable concentrations of trace metals, PAHs, and PCBs). Exclosures were used to study the effect of predation by fish and birds on macroinvertebrates. Macroinvertebrates were sampled and identified to species level, and production was estimated from biomass increases inside the exclosures during a 1-mo interval in spring
    Most floodplain sediments of the rivers Rhine and Meuse in The Netherlands are moderately polluted with trace metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other chemicals. The effects of these sediment-bound contaminants on the productivity of benthic macroinvertebrates are unclear. Sixteen locations along a pollution gradient were investigated in creeks in the Biesbosch floodplain area. Sediment samples were analyzed for bulk sediment characteristics and contaminants (total and bioavailable concentrations of trace metals, PAHs, and PCBs). Exclosures were used to study the effect of predation by fish and birds on macroinvertebrates. Macroinvertebrates were sampled and identified to species level, and production was estimated from biomass increases inside the exclosures during a 1-mo interval in spring. Benthic macroinvertebrate species richness was negatively affected by sediment contamination. Production of oligochaetes and chironomids was not correlated with levels of contamination, but production of gastropods was negatively correlated with contamination. Environmental variables that reflected food availability (seston and sediment organic C) were positively correlated with contamination. Predation significantly reduced invertebrate biomass, but the effects of predation and sediment contamination were not correlated with each other. Our study suggested that the moderate levels of contamination affected the structure but not the productivity of the benthic macroinvertebrate community, probably because of the counteracting effects of contamination and associated surplus of food.
    Testing the European stream typology of the Water Framework Directive for macroinvertebrates
    Verdonschot, P.F.M. ; Nijboer, R.C. - \ 2004
    Hydrobiologia 516 (2004)1-3. - ISSN 0018-8158 - p. 35 - 54.
    waterbeheer - ecologie - stroomgebieden - kwaliteitscontroles - waterinvertebraten - waterverontreiniging - beoordeling - testen - waterkwaliteit - richtlijnen (directives) - eu regelingen - kaderrichtlijn water - aquatische ecosystemen - ecologische beoordeling - water management - ecology - watersheds - quality controls - aquatic invertebrates - water pollution - assessment - testing - water quality - directives - eu regulations - water framework directive - aquatic ecosystems - ecological assessment - running waters - communities - management - systems
    In the EU Water Framework Directive (WFD) a typological framework is defined for assessing the ecological quality of water bodies in the future. The conditions in the Directive impose a strong demand for `new' assessment systems. During the AQEM project an assessment system was developed for European streams using macroinvertebrates. The aim of this study was to test if the typology suggested in the WFD is useful for developing an assessment system for macroinvertebrates in streams. In total 889 streams of 29 stream types were sampled in eight countries all over the major geographical gradients in Europe. These stream types fit the WFD typological demands and fit to the major European geographic regions (ecoregions). The sites included gradients from reference conditions (for the definition see Nijboer et al., 2004) to sites with bad ecological quality. Despite standardisation there were large differences between the participating countries concerning the number of taxa, the number of specimens and the taxonomic resolution. The data, including macroinvertebrates and environmental variables were analysed by using Canonical Correspondence Analysis (CCA). The observed macroinvertebrate distribution largely supported the WFD typological criteria. This means that the major macroinvertebrate distribution patterns in European streams follow climatological and geomorphological conditions and are well distinguished in terms of stream types. Furthermore, it was shown that large scale factors affected the macroinvertebrate distribution even on a very fine scale. Most explanatory variables seemed to be scale independent. Even at a fine scale major factors concerning geology, geomorphology and hydrology added to the species occurrences. Within stream types morphology together with physico-chemistry best explained the macroinvertebrates distribution. In conclusion, the WFD typology is useful for an assessment system for streams using macroinvertebrates. The large scale factors were indeed the variables that explained most of the variation in species composition. But as these factors even strongly act at the scale of stream types, a further refinement is most probably necessary to disentangle typological actors from water quality ones.
    Aquatic ecology of lowland streams
    Verdonschot, P.F.M. ; Hoorn, M.W. van den; Hoek, T.J. van den - \ 2002
    In: Effects of climate and land-use change on lowland stream ecosystems / van Walsum, P.E.V., Verdonschot, P.F.M., - p. 101 - 118.
    waterlopen - waterinvertebraten - oppervlaktewater - aquatische ecosystemen - noord-brabant - aquatische ecologie - beken - fauna - hydrologie - streams - surface water - aquatic invertebrates - aquatic ecosystems - noord-brabant - fauna
    Evaluation of bioassays versus contaminant concentrations in explaining the macroinvertebrate community structure in the Rhine-Meuse delta, the Netherlands
    Peeters, E.T.H.M. ; Dewitte, A. ; Koelmans, A.A. ; Velden, J.A. van der; Besten, P.J. den - \ 2001
    Environmental Toxicology and Chemistry 20 (2001)12. - ISSN 0730-7268 - p. 2883 - 2891.
    rivieren - delta's - waterinvertebraten - biotesten - toxiciteit - rijn - maas - rivers - deltas - aquatic invertebrates - bioassays - toxicity - river rhine - river meuse
    It is often assumed that bioassays are better descriptors of sediment toxicity than toxicant concentrations and that ecological factors are more important than toxicants in structuring macroinvertebrate communities. In the period 1992 to 1995, data were collected in the enclosed Rhine-Meuse delta, The Netherlands, on macroinvertebrates, sediment toxicity, sediment contaminant concentrations, and ecological factors. The effect of various groups of pollutants (polycyclic aromatic hydrocarbons, trace metals, oil, polychlorinated biphenyls) and of ecological variables on the structure of the macroinvertebrate community were quantified, Ecological factors explained 17.3␘f the macroinvertebrate variation, while contaminants explained 13.8ÐAnother 14.7 as explained by the covariation between ecological variables and contaminants. Polycyclic aromatic hydrocarbons explained a larger part of the variation than trace metals. The contributions of oil and polychlorinated biphenyls were small but significant. Elevated contaminant concentrations were significantly associated with differences in the macroinvertebrate food web structure. The response in bioassays (Vibrio fischeri, Daphnia magna, Chironomus riparius) was susceptible to certain contaminants but also to certain ecological factors. There was a weak correlation between in situ species composition and bioassays; 1.9␘f in situ macroinvertebrate variation was explained by the bioassay responses. This seems to contradict the validity of using bioassays for a system-oriented risk assessment. Possible reasons for this discrepancy might be the manipulations of the sediment before the test and a higher pollutant tolerance of the in situ macroinvertebrates. Thus, macroinvertebrate field surveys and laboratory bioassays yield different types of information on ecotoxicological effects, and both are recommended in sediment risk assessment procedures.
    Macrofauna in de verontreinigde waterbodem van de Rijn/Maas-delta
    DeWitte, A. ; Peeters, E.T.H.M. ; Besten, P. den; Velden, J. van der - \ 2000
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 33 (2000)10. - ISSN 0166-8439 - p. 16 - 19.
    bodemverontreiniging - fauna - bodemfauna - bodeminvertebraten - waterinvertebraten - bodembiologie - dierecologie - soortendiversiteit - statistische analyse - delta's - bodemkwaliteit - macrofauna - hollandsch diep - haringvliet - waterbodems - biesbosch - soil pollution - fauna - soil fauna - soil invertebrates - aquatic invertebrates - soil biology - animal ecology - species diversity - statistical analysis - deltas - soil quality - macrofauna - hollandsch diep - haringvliet - water bottoms - biesbosch
    Door middel van monsternemingen en statistische analyses is onderzoek gedaan naar de correlaties tussen fysische variabelen en verontreinigingen (zware metalen, organochloorpesticiden, PCB's, PAK's) in het sediment, de sedimenttoxiciteit bepaald door bioassays, en de variantie in soortensamenstelling van de bodembewonende macrofauna in Brabantsche Biesbosch, Dordtsche Biesbosch, Hollands Diep, Nieuwe Merwede en Haringvliet
    Ecological and statistical evaluation of effects of pesticides in freshwater model ecosystems
    Brink, P.J. van den - \ 1999
    Agricultural University. Promotor(en): M. Scheffer; T.C.M. Brock; C.J.F. ter Braak. - S.l. : Van den Brink - ISBN 9789054859987 - 164
    ecosystemen - zoet water - verontreiniging - pesticiden - pesticidenresiduen - zoetwaterecologie - milieueffect - risicoschatting - habitats - modellen - herbiciden - fungiciden - insecticiden - waterinvertebraten - stress omstandigheden - aquatische ecosystemen - ecotoxicologie - ecosystems - fresh water - pollution - pesticides - pesticide residues - freshwater ecology - environmental impact - risk assessment - habitats - models - herbicides - fungicides - insecticides - aquatic invertebrates - stress conditions - aquatic ecosystems - ecotoxicology

    Aquatic risk assessment of pesticides

    The first tier in the aquatic risk assessment procedure consists of a comparison between a Predicted Environmental Concentration (PEC) with a No Effect Concentration (NEC). A requirement for registration is that the PEC should not exceed the NEC. The NEC is calculated from the toxicity of the pesticide for defined standard test species (viz. algae Daphnia , fish) and an assessment factor, which accounts for potential differences between standard test species and indigenous species. The assessment factors used are 100 (to be multiplied with the acute EC50 of Daphnia and fish) or 10 (to be multiplied with the chronic NOEC of fish or EC50 of algae). Because this approach lacks ecological realism, the first aim of the present thesis was to validate the assessment factors used in the first tier by evaluating three chemicals with different modes of action (insecticide, herbicide, fungicide) as benchmark compounds.

    We compared the No Observed Effect Concentrations (NOECs), resulting from microcosm and mesocosm experiments using these compounds, with the NECs as used for the risk assessment procedure. Table 1 summarises the standards calculated from the first tier criteria set by the Uniform Principles (UP-standard), as well as the NOEC ecosystem for acute and chronic exposure regimes for the three substances. In addition, Table 1 lists the Dutch water quality standards. The assessment factors seem to protect the tested aquatic ecosystem against acute and chronic exposure to the insecticide chlorpyrifos and against chronic exposure to the herbicide linuron and the fungicide carbendazim (Table 1; chapters 2, 3 and 4). Dutch water quality standards for these three compounds were lower than the UP-standards and thus also seem to protect the aquatic ecosystems tested when exposed to individual compounds.

    A comparison between the UP-standards and the Lowest Observed Effect Concentration at the ecosystem level (LOEC ecosystem ) indicates that when the NEC is exceeded by a factor of 10, effects cannot be excluded in the case of chronic exposure. In the case of a single application of the insecticide chlorpyrifos, however, the assessment factor can be considered overprotective; an assessment factor of 10 instead of 100 would also seem to suffice. Two extensive literature reviews on the impact of insecticides and herbicides on aquatic microcosms and mesocosms also demonstrate that the first tier criteria of the Uniform Principles are generally adequate to protect different aquatic ecosystems from pesticide stress (Lahr et al., 1998; Van Wijngaarden et al., 1998). For compounds such as fungicides, however, hardly any information could be found in the open literature, so that validation of the assessment factors for these types of pesticide needs further attention.

    Table 1:Derived UP-standards, Dutch water quality standards and NOEC ecosystem observed in semi-field studies for the insecticide chlorpyrifos, the herbicide linuron and the fungicide carbendazim (all concentrations in µg/L). UP-standards were calculated from criteria set by the first tier of aquatic risk assessment. For references to toxicity values see Table 3 in chapter 1 of this thesis.
    UP-standardDutch water quality standardNOEC ecosystem / LOEC ecosystem
    Short-termLong-termAcute exposureChronic exposure
    Chlorpyrifos0.01 a0.01 c0.0030.1 / 0.9 (Chapter 2)0.01 d/ 0.1 e
    Linuron0.6 b*0.6 b*0.25- / -0.5 / 5 (Chapter 3)
    Carbendazim3.2 a1 c0.11- / -3.3 / 33 (Chapter 4)
    * Dutch standard would be 0.1 µg/L (0.1 x NOEC of the standard test algae; Anonymous, 1995); - No data available; a: 0.01 × LC50 Daphnia ; b: 0.1 × EC50 Algae; c: 0.1 × NOEC Daphnia; d: data from unpublished experiment, Van den Brink et al., in prep.; e: data from Van den Brink et al., 1995.

    Ecological effects and recovery

    One of the aims of the present thesis was to gain insight into long-term community responses and into the factors determining the recovery of affected populations after a single application of an insecticide in experimental ditches. As was expected from its mode of action, application of chlorpyrifos resulted in large adverse effects on arthropod taxa (chapter 2). Because this experiment was performed in relatively large, outdoor systems, the recovery of the affected populations could be investigated. The recovery of populations of individual species was highly dependent on their life-cycle characteristics, such as the number of generations per year, the presence of resistant life stages and the ability to migrate from one system to another. In chapter 2 this is illustrated by the responses of two mayflies, cladocerans and an amphipod. The mayflies Cloeon dipterum and Caenis horaria do not have life stages resistant to chlorpyrifos, but are able to migrate from one ditch to another. They are also almost equally susceptible to chlorpyrifos in the laboratory but showed a very different recovery pattern.

    The former species recovered within 12 weeks at the highest treatment level, whereas the latter species took 24 weeks to recover fully. This can be explained from the difference in the number of generations per year. C. dipterum has many generations per year and thus recolonises the ditch repeatedly, thus recovering as soon as the concentration of chlorpyrifos allows this. C. horaria , however, produces only one generation per year, so that recovery can only take place when the next generation recolonises the ditch. Unlike mayflies, Cladocerans are not able to migrate actively from one ditch to the other. They did, however, show a very fast recovery at the higher concentration (Chapter 2). This is possible because they have a short generation time and resistant life stages in the form of ephyppia. If a taxon is not able to recolonise an impacted system and does not have resistant life stages, the species can become extinct in isolated systems like the experimental ditches. This applies for the amphipod Gammarus pulex , which became extinct at the two highest concentrations and did not recover within the 55 week experimental period. No significant effects on the invertebrate community, with the exception of Gammarus, were found from week 24 after insecticide application onwards, suggesting recovery.

    As part of the third aim of the thesis, the long-term responses in ecosystem structure and functioning after chronic exposure to a herbicide and fungicide were studied in aquatic microcosms. The higher concentration of the photosynthesis-inhibiting herbicide linuron resulted in a decreased biomass of the macrophyte Elodea nuttallii and decreased abundance of most algal taxa (chapter 3). The dissolved oxygen and pH levels also decreased at lower pesticide concentrations as a consequence of inhibited photosynthesis. Although a decrease in the abundance of most algal taxa was observed after to the herbicide application, a net increase in chlorophyll-a was found for the phytoplankton, periphyton and neuston. This increase was completely caused by the green alga Chlamydomonas sp., which appeared to be relatively tolerant to linuron and also had the ability to develop a tolerance to relatively high concentrations within a week. As a result of this tolerance and the reduced competition for nutrients with macrophytes, the community in the microcosms shifted from macrophyte-dominated to an algae-dominated state, especially at the highest treatment level (150 µg/L). The Copepoda and Cladocera benefited from this increased food supply and showed elevated abundance values at the higher treatment levels. Some macrophyte-associated invertebrates decreased in abundance as a result of the decline of their habitat.

    The fungicide carbendazim, which belongs to the bendimidazoles, is known to adversely affect microorganisms and worms. This property explains its effects on the "worm-like" taxa of the Turbellaria and Oligochaeta, but could not explain its effects on invertebrate groups like Amphipoda, Gastropoda and Cladocera (chapter 4). Unlike the direct effects of chlorpyrifos and linuron, therefore those of carbendazim on freshwater populations could not be completely deduced from the latter's taxonomic relation with the pest organisms, carbendazim it is supposed to control. The fungicide appeared to have the mode of action of a biocide rather than a chemical with a specific mode of action. Due to the decline of many invertebrates and the concomitant reduction in grazing pressure, the chlorophyll-a level and the abundance values of some phytoplankton taxa increased at the two highest concentrations (330 and 1000 µg/L).

    The "eutrophication-like" consequences of insecticide contamination have also often been reported and discussed in the literature (e.g. DeNoyelles et al., 1994, Cuppen et al., 1995). The increased abundance of algae due to a decrease in susceptible herbivores is a commonly reported consequence of insecticide contamination (Van Wijngaarden et al., 1998).

    In the present thesis, the occurrence of herbicides in the aquatic ecosystem is regarded as an undesirable side effect of its use on land. However, herbicides are also deliberately released into aquatic ecosystems for the control of nuisance aquatic vegetation (Pieterse and Murphy, 1990). Aquatic weeds are most commonly removed using compounds with a mode of action specific to macrophytes. Since algae are relatively tolerant to these chemicals (Lahr et al., 1998), they may increase their biomass due to reduced competition for nutrients (Kobriae and Whyte, 1996). Terrestrial weeds are, in the Netherlands, usually controlled by means of photosynthesis-inhibiting herbicides (NEFYTO, 1996). Although their mechanism is different, chapter 3 shows that prolonged exposure to the photosynthesis-inhibiting herbicide linuron may also result in a shift from macrophyte dominance to plankton dominance. The review published by Lahr et al. (1998) shows that this may be true for photosynthesis-inhibiting herbicides in general.

    The effects of fungicides are largely unstudied, but chapter 4 indicates that fungicide contamination can also cause elevated algal densities. This means that all three pesticides can contribute to "eutrophication-like" effects, though the mechanisms differ. The significance of realistic concentrations of pesticides in causing symptoms of eutrophication in surface waters, however, largely remains to be investigated.

    Tools to evaluate microcosm and mesocosm experiments

    Semi-field experiments are usually evaluated at the taxon level. Since many species normally have low abundance values and/or show high variability (Van Wijngaarden et al., 1996), this approach has the great disadvantage that only a limited number of species can be properly analysed. This means that a substantial part of the information gathered is not used for the evaluation. This thesis presents a new multivariate tool for the analysis of treatment effects at the community level. Multivariate techniques have already been used for a long time in ecology to analyse the relation between communities and their environment. The most commonly used ordination technique is correspondence analysis, which is based on the bell-shaped unimodal model. This model fits in with the theory of the rise and fall in a preference of a species along an environmental gradient, described by their optimum and tolerance.

    Chapter 7 indicates why clustering and ordination based on correspondence analysis are not suitable for the analysis of the ecotoxicological data sets presented in this thesis. It argues that species normally have no optimum along the environmental axis of a stressor such as pesticides. Their response is more accurately described by a linear method; expected direct effects will increase with the concentration. On the basis of laboratory tests, this relation between the endpoint and the concentration of stressor is assumed to be sigmoid, and it is argued that a linear response model is a good approximation of this.

    Chapters 2 and 3 use Redundancy Analysis (RDA) to elucidate the effects of pesticides at the community level. RDA is the constrained version of the well-known ordination technique Principal Component Analysis (PCA) and is based on a linear response model (Jongman et al., 1995). In chapters 2 and 3 the analysis is constrained to the variance explained by treatment, time and their interaction. It was concluded that RDA successfully summarised the effects of a pesticide on a community in a single diagram, and is very useful especially when combined with Monte Carlo permutation tests for the determination of the significance of treatment effects. Kersting and Van den Brink (1997), however, found that output from RDA can sometimes result in very cluttered diagrams.

    Chapter 5 presents a new method, termed the Principal Response Curves, which overcomes this problem. PRC is based on RDA and extracts the first principal component from the treatment variance, by excluding from the analysis the variance explained by time as well as differences between replicates. It results in an easy-to-read diagram, showing the deviations of all treatments from the control in time. In contrast to most other techniques, it also allows a quantitative interpretation down to the species level. Chapter 6 introduces the rank 2 model of PRC, this means that after the extraction of the first basic response pattern, a second pattern is extracted, which expresses the most important deviation from the first response present in the data set. The second pattern is of particular importance if no single dominant response pattern is present in a data set but several sub-dominant ones occur. In chapter 6 this is illustrated by an analysis of the invertebrate and phytoplankton data sets of a microcosm experiment with two stressors, the insecticide chlorpyrifos and nutrient additions. This example shows that PRC is also able to summarise several different response patterns in two diagrams.

    Microcosm and mesocosm experiments are often said to be of limited value due to ecological variability and noise. From the experiments and statistical tools as described in this thesis we can conclude that despite the noise clear response patterns are revealed, if experiments are properly designed and analysed. Chapters 2, 3 and 4 illustrate that, even with a limited number of replicates, an ecological threshold level (e.g. NOEC ecosystem ) and an effect-chain covering different trophic levels can be obtained.

    Suggestions for future research

    In normal agricultural practice, protection of crops from pest organisms is not achieved by the application of a single compound; usually, several different compounds with different target organisms are used. Some pesticides are also administered repeatedly. The effects of combinations of pesticides on freshwater ecosystems are, however, largely unstudied (Hartgers et al., 1998). Therefore, it is important to develop criteria for the ecological risk assessment of mixtures of compounds, using realistic pesticide treatment regimes for particular crops.

    The problem of combination toxicity becomes even more complex when other substances used in agricultural areas, such as fertilisers, are taken into account. The combined effects of eutrophication and contaminant stress are largely unknown. It can be expected, however, that the trophic status of an ecosystem will alter the effects of pesticides (Chapter 6; Kramer et al., 1997).

    The ecological effect chain resulting from the experiments with the herbicide linuron and fungicide carbendazim demonstrated that microcosm and mesocosm experiments with pesticides as stressors can be very useful tools to investigate trophic interactions in aquatic ecosystems. The results of these experiments are currently being used to build a food-web model (Traas et al., 1998). Such models are considered to hold great promise for an improved understanding of ecosystem functioning and may eventually provide the ability to predict effects of contaminants at ecosystem level (Health Council of the Netherlands, 1997). The greatest obstacles that have to be overcome are the lack of solid data on parameter values (data on for instance maximum growth rate) and the lack of validation. This means that the further development of food web models require not only laboratory research on parameters values but also semi-field research for the collection of validation data sets (Health Council of the Netherlands, 1997).

    The modeling of direct effects and recovery patterns at the population level can be of great use for an assessment of the risks and a ranking of the effects of pesticides. For the future, modeling treatment effects and recovery patterns may be of great value as a research tool but also as a predictive tool. Models have the advantage that they allow integration of ecological and ecotoxicological knowledge, something that was largely absent from ecotoxicology until a few years ago. Development of these models will allow to a better evaluation of microcosm and mesocosm experiments performed for scientific or registration purposes.

    Toxicity of Derosal (active ingredient carbendazim) to aquatic invertebrates
    Wijngaarden, R.P.A. ; Crum, S.J.H. ; Decraene, K. ; Hattink, J. ; Kammen, A. van - \ 1998
    Chemosphere 37 (1998)4. - ISSN 0045-6535 - p. 673 - 683.
    waterinvertebraten - waterverontreiniging - fungiciden - carbendazim - toxiciteit - ecotoxicologie - aquatic invertebrates - water pollution - fungicides - carbendazim - toxicity - ecotoxicology
    Short- and long-term laboratory single species toxicity tests were performed with eleven invertebrate species and the fungicide Derosal(R) (a.i. carbendazim). Toxicity values differed widely between the tested invertebrates. The most sensitive species we found was the flatworm Dugesia lugubris (96hr-EC50: 25 g/L, 21d-NOEC(reproduction): 11 g/L). Besides within flatworms, other sensitive taxa were representatives of oligochaetes, amphipods and cladocerans. On the longer-term, offspring production of some gastropod species was found to be a relatively sensitive life history characteristic for this latter group.
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