An in vitro – in vivo integrated approach for hazard and risk assessment of silver nanoparticles for soil organisms
Makama, S.I. - \ 2016
Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Nico van den Brink. - Wageningen : Wageningen University - ISBN 9789462578432 - 190
particles - nanotechnology - toxicity - earthworms - gene expression - soil - coatings - deeltjes - nanotechnologie - toxiciteit - aardwormen - genexpressie - bodem - afdeklagen
Owing to their small sizes, nanoparticles (NPs) exhibit completely different and novel characteristics compared to their bulk counterparts of the same chemical composition. These novel properties include increased reactivity due to large specific surface area, fluorescence and colour changes, increased biological barrier crossings and increased material strengthening combined with light-weight. Virtually all fields of human endeavours are exploiting nanotechnology to combat different challenges. This has led to an increase in the production and potential release of NPs into the environment. The novel properties of these NPs however, mean an enhanced potential for interactions with biological systems that are different from the interactions of known conventional chemicals, thus raising environmental and public health/safety concerns. Available literature has reported NP uptake in different organisms along with associated hazards. Therefore, to safeguard human and environmental health and safety, regulatory measures are necessary. Such measures must be based on sound scientific evidence and be risk-based rather than hazard-based. As such, the need to understand the fate of NPs after environmental release and their potential to pose hazards and risks to the environment is critical for a proper risk assessment and further development of policy strategies on the future regulation of the use of NPs.
Some studies have demonstrated different and sometimes conflicting effects of NP properties on their uptake in different organisms. Given that exposure determines whether hazards will turn into risks, there is a critical need for further systematic evaluation of the physico-chemical properties of engineered or manufactured NPs that influence uptake in terrestrial organisms, and also of how soil properties may affect these processes. The objective of this project was to determine the influence of size and surface coating (charge), two important physico-chemical properties of NPs, on their bioavailability, uptake and toxicity. The red earthworm Lumbricus rubellus, common in most parts of Europe, was used as a model soil organism. Silver nanoparticles (AgNPs) have been identified as one of the most commonly used NPs in many products, and their production is expected to continue to increase. Therefore, we selected AgNPs as our model NPs. For our investigations, we applied an integrated in vitro - in vivo approach, utilising high throughput in vitro methods as well as well-established in vivo toxicity end-points in the earthworm. A systematic experimental approach was developed for which AgNPs were synthesized in three sizes: 20, 35 and 50 nm. Surface-coating with bovine serum albumin (AgNP_BSA), chitosan (AgNP_Chit), or polyvinylpyrrolidone (AgNP_PVP) resulted in negative, positive and neutral particles respectively.
Firstly, macrophage cells (RAW 264.7) were exposed to AgNPs at 0 – 200 µg/mL (nominal concentrations) and uptake dynamics, cell viability, as well as induction of tumour necrosis factor (TNF)-α and reactive oxygen species (ROS) were assessed (Chapter 2). Generally, the adverse effects of exposure to the tested AgNPs resulted in reduced overall viability of the cells, which was similar for all AgNPs tested. On adenosine triphosphate (ATP) production and specific mechanisms of toxicity (TNF-α and ROS production) however, we observed that the AgNPs differed significantly, with the negatively charged AgNP_BSA being the most toxic. Significant ROS induction was only observed after exposure to the 20 nm positively charged AgNP_Chit. Effect of size was less prominent than that of surface coating, showing mostly limited differences that were not statistically significant under our experimental conditions. Live confocal imaging of exposed cells allowed the monitoring of the uptake dynamics and subcellular cytoplasmic accumulation of AgNPs. We observed fast uptake of AgNPs within 2.5 hours which is essential in case of exposure durations of 6 and 24 hours, as applied in our experiments. However, similar uptake did not always result in similar effects.
With the insights obtained from the in vitro assessments, we investigated the effects of size and surface coating (charge) of AgNPs on the bioaccumulation in, and toxicity (survival, growth, cocoon production) to the earthworm L. rubellus. Currently, metal engineered NPs in tissues are generally quantified based on total metal concentrations after acid destruction of samples. Such destructive methods are limited in providing information on the speciation and the forms of NPs which is essential for characterising the fate of NPs. In the present thesis, we developed a method using a combination of enzymatic tissue processing and single particle inductively coupled plasma–mass spectrometry (sp-ICP-MS) to characterise and quantify AgNPs in tissues of earthworms (Chapter 3). Subcellular fractionation of tissues was also applied to investigate potential association of AgNPs with the cellular metallothionein (MT) containing fraction of the earthworm tissues. This study provided, to the best of our knowledge, the first estimates of tissue Ag concentrations in both particulate and ionic forms in earthworms exposed in vivo to AgNPs via soil. The results obtained showed fairly low uptake of AgNPs, with earthworms exposed to a commercially obtained PVP-coated AgNP showing approximately 34% of their total Ag tissue burden being in particulate form. This indicates that although AgNPs accumulated in tissues of earthworms in their primary form, the dissolution of Ag in the soil, organism, or both played an important role in determining the ultimate fate of the AgNPs. Although the biological uptake of AgNPs was generally low, the method described in Chapter 3 was still capable of extracting NPs in quantities sufficient for identification, quantification and characterisation. It should be noted however, that the lower size detection threshold for the ICP-MS instrument used for these analyses is approximately 30 nm. Consequently, information on NPs smaller than 30 nm was not available. With the increasing optimisation of analytical systems that combine sp-ICP-MS, or other detection methods with, for example, asymmetric flow field-flow fractionation (AF4) which pre-sort different particle sizes, the potential for application of methods described in this thesis will be even greater.
Having developed a method for extracting Ag from tissues, we exposed earthworms to all nine synthesized AgNPs as well as to AgNO3 at two concentrations below known EC50s to control for ionic effects of Ag in a 28-day sub-chronic reproduction toxicity test in soil in Chapter 4. Uptake was observed to be generally highest for the negatively charged AgNP_BSA especially at the lower exposure concentration ranges. Total Ag concentrations in earthworm tissues reached a plateau level of about 80 mg Ag/kg dry weight (DW) for exposure concentrations between 15 – 100 mg Ag/kg soil DW. Reproduction was impaired at high nominal soil concentrations of all AgNPs tested, with AgNP_BSA particles being the most toxic. Size had an influence on uptake of the AgNP_PVP, showing both uptake and effect on reproduction of the 20 nm sized group to be significantly more than those of the 35 and 50 nm AgNP_PVP. This size effect however, did not hold for AgNP_BSA nor AgNP_Chit. Higher uptake from the soil may consequently lead to a higher potential for toxicity in organisms. Interestingly, internal total Ag tissue concentrations measured after 72 hour exposure were better at predicting the effect on reproduction than tissue concentrations after 28 days exposure. It is likely therefore, that reproduction was affected already in the 72 hour exposure window.
In order to further elucidate the likely mechanisms by which these AgNPs were exerting their effects, we conducted a toxicogenomic study in Chapter 5. Although AgNPs have been increasingly investigated, information regarding their effect on the gene expression profile of especially soil organisms is yet inadequate. Using RNAseq, we investigated the transcriptome and gene expression profiles of the earthworm L. rubellus, following exposure to the nine AgNPs. Overall, exposure to medium sized AgNPs at a concentration close to the EC50 for effects on cocoon production caused most pronounced responses at the transcriptional level. There was a correlation however, between the numbers of differentially expressed genes (DEGs) and internal Ag concentrations in the earthworms. Within the medium size AgNPs, AgNP_BSA caused extensive transcriptional responses, with 684 genes affected. In contrast ionic silver (AgNO3) did not affect gene expression at low as well as higher exposure levels. Only one gene was regulated by all AgNP and Ag+ treatments, indicating that there was hardly any functional overlap between the responses of the organisms to AgNPs with different coatings. Remarkably, this gene was metallothionein, a cysteine-rich peptide known to strongly bind free metal ions for chelation and detoxification, which was strongly up-regulated. Gene ontology enrichment analysis for 35 nm AgNP_BSA exposures revealed a total of 33 significantly enriched gene ontology terms related to biological processes. These included responses to pH, proton transport, cell differentiation, microtubule organisation, and and MT induction. Surface coating (BSA) was important in triggering the AgNP-induced differential gene expression profiles in earthworms. The importance of physicochemical properties of NPs in influencing their fate and toxicity is thus elucidated in the current study.
The studies reported in the current thesis showed that within the range of 20 to 50 nm, effects of the size of AgNPs on toxicokinetics and toxicodynamics are limited. However, effects of surface coating were consistent over the different levels of biological integration. Generally, the negatively charged AgNP_BSA accumulated to a higher extent in the earthworms, especially at lower concentrations. The in vitro uptake was fast for all NPs, but also showed the highest uptake of AgNP_BSA. The negatively charged AgNPs were also the most toxic, likely related to their increased uptake. This was evident at all levels: gene expression, cellular, and individual (population dynamic parameters) levels. At the in vitro level, this applied mostly to effects on specific modes of action (TNF-α induction, ROS production). For more general cytotoxic effects, the effects of surface coatings were less evident. Except in cells exposed to AgNP_Chit 20 nm, where there was a slight increase in ROS production, this set of AgNPs under the experimental conditions applied, did not appear to induce the production of ROS. This was supported by the lack of expression of any ROS-related gene in the gene expression profile analyses.
Based on the results of the current research, it can be concluded that the physico-chemical properties of NPs do influence their environmental fate and toxicity. It should be noted however that general predictions on the outcome of exposure to NPs are difficult to make, and NPs should be evaluated on a case by case basis. Our research supports the use of in vitro models to limit and prioritize further in vivo studies. Studies investigating the fate and effects of NPs for soil organisms are vital for a holistic approach towards a comprehensive and adequate environmental risk assessment (ERA). The studies described in this thesis contribute to this knowledge, thereby improving our understanding of the hazards and risks due to exposure to AgNPs, thus enabling their adequate and comprehensive ERA.
Aandacht voor de regenworm
Pulleman, M.M. ; Frazao, J.F.T.A. ; Faber, J.H. ; Goede, R.G.M. de; Groot, J.C.J. ; Brussaard, L. - \ 2016
Landschap : tijdschrift voor landschapsecologie en milieukunde 33 (2016)1. - ISSN 0169-6300 - p. 23 - 26.
akkerbouw - aardwormen - akkerranden - bodemstructuur - bodembeheer - landinrichting - landschapsbeheer - zuidhollandse eilanden - arable farming - earthworms - field margins - soil structure - soil management - land development - landscape management - zuidhollandse eilanden
Regenwormen leveren een belangrijke bijdrage aan de omzetting van bodemorganische stof en nutriënten en zorgen voor een goede bodemstructuur, maar ze zijn gevoelig voor verstoringen die de moderne landbouw met zich meebrengt (onder meer Pelosi et al., 2014). Naar aanleiding van strengere regelgeving rond het gebruik van meststoffen en toenemende bodemverdichting staat een beter begrip van de effecten van bodembeheer en landinrichting op regenwormengemeenschappen momenteel volop in de belangstelling.
Monitoring van ecologische risico’s bij actief bodembeheer van slootdempingen in de Krimpenerwaard : afrondende rapportage T1-monitoring Ecologie
Lange, H.J. de; Hout, A. van der; Faber, J.H. - \ 2016
Alterra, Wageningen-UR (Alterra-rapport 2703) - 61
bodemverontreiniging - zware metalen - polychloorbifenylen - bodemsanering - ecologische risicoschatting - risico - aardwormen - talpidae - krimpenerwaard - zuid-holland - soil pollution - heavy metals - polychlorinated biphenyls - soil remediation - ecological risk assessment - risk - earthworms - talpidae - krimpenerwaard - zuid-holland
In de Krimpenerwaard liggen circa 6500 slootdempingen en vuilstorten. Het dempingsmateriaal bevat
regelmatig verontreinigingen, zodat voor de hele regio sprake is van een geval van ernstige
bodemverontreiniging. Het gebiedsgericht bodembeheerplan voorziet in het afdekken van de
verontreinigde slootdempingen met gebiedseigen schone grond. De effectiviteit van de sanering wordt
geëvalueerd op basis van monitoring van ecologische risico’s. Dit rapport beschrijft de resultaten van
de T1-monitoring, waarin in een relatief korte tijd na afdekken (twee tot vier jaar) de effectiviteit van
de maatregel wordt beoordeeld. De saneringsmaatregel blijkt de meeste nadelige effecten van de
slootdemping op soortensamenstelling en aantallen regenwormen te hebben weggenomen. De
gehalten zware metalen in twee onderzochte regenwormsoorten zijn na sanering over het algemeen
lager dan de gebiedseigen referentie in de T0-monitoring. De saneringsmaatregel is dus op de korte
termijn effectief om de risico’s voor doorvergiftiging van zware metalen terug te brengen tot
gebiedseigen niveau. De PCB-gehalten in de twee soorten regenwormen vertonen veel variatie tussen
de jaren. De tendens is dat de gehalten in dempingmonsters lager zijn dan in referentiemonsters.
Vanwege de grote variatie en het beperkt aantal onderzochte locaties zijn deze conclusies alleen met
voorzichtigheid te trekken. Het PCB-gehalte in mollen bleek ook sterk variabel, in ruimte en in tijd.
Mollen die in de T1-monitoring gevangen zijn op afgedekte Shredder en Huishoudelijk afval
dempingen hebben significant hogere PCB-gehalten dan de dieren op de referentiepercelen. Het
afdekken van de demping heeft voor deze dempingcategorieën de ecologische risico’s onvoldoende
weggenomen. De effectiviteit op langere termijn met betrekking tot het al dan niet optreden van
herverontreiniging als gevolg van bioturbatie en capillaire opstijging werd niet onderzocht
Ecological functions of earthworms in soil
Andriuzzi, W.S. - \ 2015
Wageningen University. Promotor(en): Lijbert Brussaard; T. Bolger, co-promotor(en): O. Schmidt. - Wageningen : Wageningen University - ISBN 9789462574175 - 154
aardwormen - oligochaeta - bodemfauna - bodembiologie - bodemecologie - ecosystemen - bodemstructuur - earthworms - oligochaeta - soil fauna - soil biology - soil ecology - ecosystems - soil structure
Ecological functions of earthworms in soil
Walter S. Andriuzzi
Earthworms are known to play an important role in soil structure and fertility, but there are still big knowledge gaps on the functional ecology of distinct earthworm species, on their own and in interaction with other species. This thesis investigated how earthworms affect soil biochemical and biophysical functioning, and other organisms such as plants and smaller soil organisms.
Two field experiments with stable isotope tracers were performed to investigate how anecic earthworms (which feed on organic matter at the soil surface and dig deep burrows) transfer carbon and nitrogen from fresh plant litter into soil, and how this in turn affects soil organic matter composition, protists and nematodes. Another field experiment tested whether the anecic earthworm Lumbricus terrestris can counteract negative effects of intense rainfall on soil and plants (ryegrass). A greenhouse experiment was carried out to study how co-occurring earthworm species – two anecic and one endogeic (smaller, soil-feeding) – affect transfer of nitrogen from dung to soil and plants, nitrogen retention in soil, and plant growth. For the latter experiment, a method to produce herbivore (rabbit) dung triple-labelled with carbon, nitrogen and sulphur stable isotopes was developed.
Overall, the findings highlight important functions of earthworms in carbon and nitrogen cycling, soil biophysical structure maintenance due to burrow formation, and resulting biotic interactions. A novel finding was that the sphere of influence of anecic earthworms in soil (the ‘drilosphere’) is a much larger biochemical and biological hotspot than hitherto assumed. Rapid movement of carbon and nitrogen from surface to soil thanks to anecic earthworm activity resulted in spatial heterogeneity in soil carbon content, organic matter composition, and density of smaller eukaryotes (e.g. bacterial-feeding protists). Evidence was found that distinct earthworm anecic species may have dissimilar effects on soil biochemistry and plant growth, and that both anecic and endogeic earthworms may feed on surface organic matter (dung). This shows that the validity of earthworm ecological groups depends on the function under study, and suggests that, for some research questions, species identity should not be neglected; other approaches to quantify ecological differences between species (e.g. functional traits) are appraised. Finally, L. terrestris was found to ameliorate the disturbance of intense rain on plants, giving evidence to the idea that some components of soil biodiversity may contribute to ecosystem stability in the face of disturbance.
Tot de bodem uitzoeken : micro-organismen beïnvloeden plantengroei
Beintema, N. ; Groenigen, J.W. van - \ 2015
WageningenWorld (2015)2. - ISSN 2210-7908 - p. 10 - 15.
bodembiologie - bodembeheer - organische stof - aardwormen - bodemkwaliteit - organisch bodemmateriaal - koolstof - micro-organismen - bodemvruchtbaarheid - gewasbescherming - plantenontwikkeling - soil biology - soil management - organic matter - earthworms - soil quality - soil organic matter - carbon - microorganisms - soil fertility - plant protection - plant development
Per vierkante meter bodem leven honderden wormen en insecten samen met kilometers aan schimmeldraden, vele miljoenen aaltjes en miljarden bacteriën. Onderzoek maakt steeds meer duidelijk van het precaire evenwicht ondergronds, en de grote invloed daarvan op het leven bovengronds. Het levert nieuwe strategieën op voor gewasbescherming.
Earthworms and the soil greenhouse gas balance
Lubbers, I.M. - \ 2014
Wageningen University. Promotor(en): Lijbert Brussaard, co-promotor(en): Jan-Willem van Groenigen. - Wageningen : Wageningen University - ISBN 9789461739315 - 222
aardwormen - oligochaeta - broeikasgassen - bodem - koolstofvastlegging in de bodem - koolstofvastlegging - emissie - bodembiologie - earthworms - oligochaeta - greenhouse gases - soil - soil carbon sequestration - carbon sequestration - emission - soil biology
Earthworms play an essential part in determining the greenhouse gas (GHG) balance of soils worldwide. Their activity affects both biotic and abiotic soil properties, which in turn influence soil GHG emissions, carbon (C) sequestration and plant growth. Yet, the balance of earthworms stimulating C sequestration on the one hand and increasing GHG emissions on the other has not been investigated. Indeed, much is still unclear about how earthworms interact with agricultural land use and soil management practices, making predictions on their effects in agro-ecosystems difficult. In this thesis, I aimed to determine to what extent GHG mitigation by soil C sequestration as affected by earthworms is offset by earthworm-induced GHG emissions from agro-ecosystems under different types of management. To reach this aim, I combined mesocosm and field studies, as well as meta-analytic methods to quantitatively synthesize the literature.
Using meta-analysis, I showed that, on average, earthworm activity leads to a 24% increase in aboveground biomass, a 33% increase in carbon dioxide (CO2) emissions and a 42% increase in nitrous oxide (N2O) emissions. The magnitude of these effects depends on soil factors (e.g., soil organic matter content), experimental factors (e.g., crop residue addition or fertilizer type and rate) and earthworm factors (e.g., earthworm ecological category and -density).
Conducting both a mesocosm and a field study, I showed that earthworm activity results in increased N2O emissions from fertilized grasslands. Under field conditions I found an increase in earthworm-induced N2O emissions in autumn but not in spring, suggesting that earthworm effects in the field depend on soil physicochemical parameters influenced by meteorological and seasonal dynamics.
In a unique two-year experiment with a simulated no-tillage (NT) system and a simulated conventional tillage (CT) system, I found that earthworm presence increases GHG emissions in an NT system to the same level as in a CT system. This suggests that the GHG mitigation potential of NT agro-ecosystems is limited. When considering the C budget in the simulated NT system, I demonstrated that over the course of the experiment earthworms increase cumulative CO2 emissions by at least 25%, indicating a higher C loss compared to the situation without earthworms. Yet, in the presence of earthworms the incorporation of residue-derived C into all measured soil aggregate fractions also increased, indicating that earthworm activity can simultaneously enhance CO2 emissions and C incorporation into aggregate fractions.
In conclusion, the revealed dominance of GHG emissions over C sequestration as affected by earthworms implies that their presence in agro-ecosystems results in a negative impact on the soil greenhouse gas balance.
Regenwormen op het melkveebedrijf : handreiking voor herkennen, benutten en managen
Eekeren, N.J.M. van; Bokhorst, J. ; Deru, J. ; Wit, J. de - \ 2014
Driebergen : Louis Bolk Instituut (Rapport / Louis Bolk Instituut 2014-004 LbD) - 37 p.
aardwormen - bodemkwaliteit - bodemvruchtbaarheid - bodemvruchtbaarheidsbeheer - melkveehouderij - bodembiologie - graslanden - bouwland - graslandbeheer - earthworms - soil quality - soil fertility - soil fertility management - dairy farming - soil biology - grasslands - arable land - grassland management
In deze brochure worden handreikingen gegeven voor de praktijk, waarbij zowel strooiselbewonende, bodembewonende en pendelende regenwormen aan bod komen.
Koester de regenworm
Eekeren, N.J.M. van; Deru, J.G.C. ; Poot, N. - \ 2014
V-focus 11 (2014)2. - ISSN 1574-1575 - p. 40 - 41.
melkveehouderij - aardwormen - grondbewerking - voedingsbehoeften - nadelige gevolgen - strooisel - bodemstructuur - bodemfauna - dairy farming - earthworms - tillage - feed requirements - adverse effects - litter (plant) - soil structure - soil fauna
Regenwormen zijn belangrijk op een melkveebedrijf voor de afbraak van organische stof, het beschikbaar maken van nutriënten, behoud van bodemstructuur, waterinfiltratie, beworteling en uiteindelijk gewasopbrengst. Vooral pendelende wormen hebben unieke functies, maar zijn heel gevoelig voor een intensieve en/of kerende grondbewerking door hun levenswijze, in permanente gangen, en hun behoefte aan strooisel als voedsel. Als de melkveehouderij beter gebruikt wil maken van de pendelaars is de vraag wat het belangrijkste knelpunt is: grondbewerking of een gebrek aan voedsel en bescherming. Resultaten van een proef naar het effect op regenwormen wordt besproken.
Zanen, M. ; Alebeek, F.A.N. van; Hanegraaf, M. - \ 2013
bodembiologie - aardwormen - akkerbouw - graslanden - inventarisaties - soil biology - earthworms - arable farming - grasslands - inventories
Regenwormen zijn belangrijk voor de bodemkwaliteit. Daarnaast zijn regenwormen een belangrijke schakel in het voedsel web van ondergrondse naar bovengrondse biodiversiteit (o.a. weidevogels). Deze Herkenningskaart is onderdeel van het pakket ‘Brede Kennisontsluiting Bodembiodiversiteit’, Op een vierkante meter bouwland is het streeftraject 80-200 regenwormen. Voor grasland is de streefwaarde 300-700. Op klei zijn de aantallen meestal hoger dan op zand. Deze brochure geeft antwoord op de vraag: welke regenworm kan ik tegenkomen.
Can arable field margins and non-inversion tillage stimulate earthworm diversity?
Huerta-Lwanga, E. ; Crittenden, S. ; Goede, R.G.M. de; Brussaard, L. ; Pulleman, M.M. - \ 2013
akkerbouw - gereduceerde grondbewerking - grondbewerking - aardwormen - akkerranden - biodiversiteit - arable farming - reduced tillage - tillage - earthworms - field margins - biodiversity
The objective of this study was to determine the effects of field margins and reduced tillage (NIT) on abundance, biomass and diversity of earthworms.
Amazing grazing : All weather beweiding
Lubbers, I.M. - \ 2013
aardwormen - broeikasgassen - bodembiologie - emissie - universitair onderzoek - earthworms - greenhouse gases - soil biology - emission - university research
egenwormen blijken een flink aandeel te hebben in de opwarming van de aarde. Dat blijkt uit een onderzoek dat de Wageningen Universiteit samen met internationale collega's uitvoerde. Regenwormen, bekend van hun vermogen de bodemvruchtbaarheid te verbeteren, blijken de uitstoot van broeikasgassen vanuit de bodem flink te verhogen; koolzuurgas gemiddeld met 33% en die van lachgas met 42%. Lachgas kan gemakkelijker via hun gangenstelsels ontsnappen naar de atmosfeer voordat het omgezet kan worden naar het onschadelijke stikstofgas.
Soil biota and nitrogen cycling in production grasslands with different fertilisation histories
Rashid, M.I. - \ 2013
Wageningen University. Promotor(en): Lijbert Brussaard, co-promotor(en): Egbert Lantinga; Ron de Goede. - S.l. : s.n. - ISBN 9789461735485 - 192
stikstofkringloop - bodemfauna - mineralisatie - rundveemest - decompositie - bodeminvertebraten - bodem ph - aardwormen - graslanden - bodembiologie - nitrogen cycle - soil fauna - mineralization - cattle manure - decomposition - soil invertebrates - soil ph - earthworms - grasslands - soil biology
|Bodembeheer afstemmen op regen- en oorwormen
Maas, M.P. van der; Heijne, B. ; Balkhoven, H. - \ 2013
De Fruitteelt 103 (2013)19. - ISSN 0016-2302 - p. 8 - 9.
bodembeheer - fruitteelt - pyrus communis - dermaptera - aardwormen - bodemstructuur - duurzaam bodemgebruik - nuttige organismen - soil management - fruit growing - earthworms - soil structure - sustainable land use - beneficial organisms
Op fruitbedrijven in de provincie is eind vorig jaar een onderzoek gestart naar het stimuleren van regen- en oorwormen en het verbeteren van de fosfaatvoeding in peer. Op drie locaties wordt de gangbare perenteelt vergeleken met een bodemleven- en oorwormvriendelijke teeltwijze. Hierbij komen alle aspecten van de perenteelt aan bod zoals gewasbescherming, ondergroeibeheer, bemesting en organische stofaanvoer.
Unravelling hazards of nanoparticles to earthworms, from gene to population
Ploeg, M. van der - \ 2013
Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Nico van den Brink. - S.l. : s.n. - ISBN 9789461734440 - 192
aardwormen - lumbricus rubellus - nanotechnologie - blootstelling - ecotoxicologie - earthworms - lumbricus rubellus - nanotechnology - exposure - ecotoxicology
Nanotechnology is an expeditiously growing field, where engineered nanoparticles are being incorporated in many different applications, from food to waste water treatment (Dekkers et al. 2011; Gottschalk and Nowack 2011; Savage and Diallo 2005). Due to this large scale production and use of nanoparticles, their release into the environment seems inevitable (Crane et al. 2008; Handy et al. 2008a; Oberdörster et al. 2005). Actual exposure levels of nanoparticles under field conditions and the hazards of nanoparticle exposure to the environment are poorly understood, especially for the soil environment (Kahru and Dubourguier 2010; Navarro et al. 2008; Shoults-Wilson et al. 2011a).
Given the need for better characterization of hazards of engineered nanoparticles to the environment and soil organisms in particular, the aim of the present thesis was to investigate effects of nanoparticle exposure on the earthworm Lumbricus rubellus, as a model organism for soil ecotoxicology, and to contribute to the development of effect markers for engineered nanoparticle exposure in this model.
The present thesis was divided in different chapters. Chapter 1 provides an introduction to the topic and discusses the importance of research on the hazards of exposure to engineered nanoparticles. Furthermore, the aim and outline of the thesis are presented, with background information on the model organism, effect markers and nanoparticles.
In chapter 2 effects of exposure to the fullerene C60 (nominal concentrations 0, 15.4 and 154 mg C60/kg soil) on survival and growth during the different life stages of L. rubellus (cocoon, juvenile, subadult and adult), as well as reproduction were quantified. These important individual endpoints for population dynamics were incorporated in a continuous-time life-history model (Baveco and De Roos 1996; De Roos 2008). In this way, effects of C60 exposure on the individual endpoints could be extrapolated to implications for population growth rate and life stage distribution, i.e. the development of the population in terms of number of individuals in the different life stages. These implications at the population level may be more relevant for the ecological impact of C60 than effects on endpoints at the individual level (Klok et al. 2006; Widarto et al. 2004). At the individual level C60 exposure caused significant adverse effects on cocoon production, juvenile growth rate and survival. When these endpoints were used to model effects on the population level, reduced population growth rates with increasing C60 concentrations were observed. Furthermore, a shift in life stage structure was shown for C60 exposed populations, towards a larger proportion of juveniles. This result implies that the lower juvenile growth rate induced by C60 exposure resulted in a larger proportion of juveniles, despite increased mortality among juveniles. Overall, this study implied serious consequences of C60 exposure for L. rubellus earthworm populations, even at the lowest level of exposure tested. Furthermore, it showed that juveniles were more sensitive to C60 exposure than adults.
To complement the observations made on survival, growth and reproduction described in chapter 2, subsequent investigations on cellular and molecular responses of the earthworms to C60 exposure were performed (chapter 3). A set of established effect markers was used, which reflect different levels of biological organisation in the earthworm and may inform on the toxic mechanisms of adverse effects induced by C60 exposure (Handy et al. 2002; Heckmann et al. 2008). At the molecular level, four specific effect markers were selected, including markers for generic stress (heat shock protein 70 (HSP70) (van Straalen and Roelofs 2006), for oxidative stress (catalase and glutathione-S-transferase (GST) (Kohen and Nyska 2002) and for an immune response (coelomic cytolytic factor-1 (CCF-1) (Olivares Fontt et al. 2002). At the tissue level, histological analyses were used to identify damage to cells and tissues, and indications of inflammation in the tissues. In these investigations, exposure to C60 (0, 15 or 154 mg C60/kg soil) affected gene expression of HSP70 significantly. Gene expression of CCF-1 did not alter in adult earthworms exposed for four weeks, but was significantly down-regulated after lifelong exposure (from cocoon stage to adulthood) of earthworms, already to the lowest C60 exposure level. No significant trends were noted for catalase and glutathione-S-transferase (GST) gene expression or enzyme activity. Tissue samples of the C60 exposed earthworms from both experiments and exposure levels, showed a damaged cuticle with underlying pathologies of epidermis and muscles. Additionally, the gut barrier was not fully intact. However, tissue repair was also observed in these earthworms. In conclusion, this study demonstrated effects of sub-lethal C60 exposure on L. rubellus earthworms, at the level of gene expression and tissue integrity.
Although tissue injury is generally associated with an inflammatory response, as part of tissue repair (Cikutovic et al. 1999; Goven et al. 1994), the tissue damage observed for the in vivo C60 exposed earthworms in chapter 3 appeareded to occur without accompanying induced immune responses. The CCF-1 gene expression level was reduced in the C60 exposed earthworms, and histological observations did not show infiltration of damaged tissues by immune cells. In order to obtain further insight in mechanisms of effects observed at the molecular and tissue level on immune related parameters, the sensitivity of immune cells (coelomocytes) of L. rubellus earthworms towards exposure to selected nanoparticles was investigated in vitro (chapter 4). To this end, coelomocytes were isolated from unexposed adult L. rubellus earthworms and exposed to C60 in vitro. After exposure, these coelomocytes were tested for cellular viability, phagocytic activity and CCF-1 gene expression levels. The gene expression of CCF-1 was most affected, demonstrating a strong reduction, which indicated immunosuppression. Experiments with NR8383 rat macrophage cells and tri-block copolymer nanoparticles were used to compare sensitivity of the cell types and showed the usefulness of coelomocytes as a test system for nano-immunotoxicity in general. Overall, this study indicated that the absence of an immune response, in case of tissue injuries observed after in vivo C60 exposure, is likely caused by immunosuppression rather than coelomocyte mortality.
In subsequent investigations, the experiments performed for C60 were also carried out with silver nanoparticles (AgNP), both in vivo and in vitro (chapter 5). Effects of AgNP were assessed in vivo at nominal concentrations of 0, 1.5 (low), 15.4 (medium) and 154 (high) mg Ag/kg soil and compared to effects of silver ions, added as AgNO3 (nominal concentration 15.4 mg Ag/kg soil). In a four week reproduction assay, the high AgNP and AgNO3 treatments had a significant effect on cocoon production and high AgNP exposure also caused a reduction in weight gain of the adult earthworms. No juveniles survived the high AgNP treatment, therefore only F1 earthworms from the other exposure treatments were monitored for survival and growth, until adulthood. These individual endpoints were used to model effects on the population level. The low and medium AgNP as well as the AgNO3 treatments significantly reduced the population growth rate. The high AgNP treatment caused complete failure of the population growth. Furthermore, histological examination of the earthworms from all AgNP exposure treatments demonstrated tissue damage, with injuries mainly at the external barriers, e.g. the cuticle and the gut epithelium. In addition, effects of AgNP exposure were assessed in vitro and a reduction of coelomocyte viability was observed in a concentration-dependent manner, although the EC50 was fourteen times higher compared with that for Ag ions, added as AgNO3. Furthermore, characterisation of the in vivo exposure media implied that AgNP remained present in the soil in single and aggregated state, releasing Ag to the soil pore water up to at least eleven months. The ionic fraction of Ag in soils has been suggested to be bioavailable to organisms and (largely) responsible for the observed AgNP toxicity (Coutris et al. 2012; Koo, et al. 2011; Shoults-Wilson et al. 2011b). In comparison, the AgNO3 seemed to dissolve rapidly, as is also known for this metal salt, and fixation of Ag ions by the soil presumably led to a quick reduction of Ag bioavailability (Atkins and Jones 2000; Coutris et al. 2012; Ratte 1999). This is in line with the observation that effects were more prolonged in the AgNP treatments in comparison with the AgNO3 exposed animals. In conclusion, this study indicated that AgNP exposure may seriously affect earthworm populations, with the ability to cause immunotoxicity, injury to the external barriers of the earthworm body and a reduction in growth, reproduction and juvenile survival.
Finally, chapter 6 presents a discussion on the findings of the present thesis and provides suggestions for future research.
Regenwormen helpen u de bodem te bewerken!
Haagsma, W.K. ; Balen, D.J.M. van; Broek, R.C.F.M. van den - \ 2012
Westmaas : PPO AGV
aardwormen - bodemstructuur - bodemverbeteraars - bodembiologie - akkerbouw - earthworms - soil structure - soil conditioners - soil biology - arable farming
Regenwormen zijn zeer actief en verzetten jaarlijks 250 keer hun eigen gewicht aan grond. Zij zorgen voor: • Omzetting van organisch materiaal in humus. • Beschikbaar maken van mineralen als stikstof en fosfaat • Verbetering van de bodemstructuur • Verbetering doorlaatbaarheid bodem voor lucht en water • Verbetering van de beworteling
|Worm blij met natte zomer : Interview met Klaas van Rozen en Mirjam Pulleman
Berg, G.A. van den; Rozen, K. van; Pulleman, M.M. - \ 2012
Boerderij 97 (2012)49. - ISSN 0006-5617 - p. 40 - 43.
aardappelen - oogsten - akkerbouw - aporrectodea caliginosa - aardwormen - potatoes - harvesting - arable farming - earthworms
Het begin van zomer 2012 was nat. Half augustus zitten de wormen boven in de aardappelrug. Als de nazomer droog verloopt, is de kans op rooiproblemen groot.
|Hoe zit het met mijn regenwormen? : Project Duurzaam Bodembeheer bij peer op kleigrond in provincie Utrecht
Maas, M.P. van der; Heijne, B. ; Anbergen, R.H.N. - \ 2012
De Fruitteelt 102 (2012)28. - ISSN 0016-2302 - p. 10 - 11.
fruitteelt - bodembeheer - duurzaamheid (sustainability) - aardwormen - bodemstructuur - helmintologie - cultuurmethoden - bemesting - fruit growing - soil management - sustainability - earthworms - soil structure - helminthology - cultural methods - fertilizer application
Fruittelers hebben regenwormen nodig. Regenwormen verteren het blad zodat de schurftdruk vermindert en ze verbeteren de bodemstructuur zodat overtollig regenwater op de rij- en boomstroken sneller wordt afgevoerd. Maar hoeveel regenwormen zijn er minimaal nodig en hoeveel zijn er aanwezig? Welke maatregelen kunnen telers nemen om het aantal regenwormen te verhogen? Dat zijn enkele vragen die centraal staan in het project: Duurzaam bodembeheer bij peer op kleigrond. Het project gaat dit jaar in de provincie Utrecht van start.
Effect of grass-clover on the ecosystem services soil structure maintenance and water regulation
Eekeren, N.J.M. van; Bokhorst, J.G. ; Brussaard, L. ; Koopmans, C.J. - \ 2011
In: Proceedings of the third scientific conference of the International Society of Organic Agriculture Research (ISOFAR), 28 Sept - 1 Oct 2011. - - p. 44 - 47.
grasklaver - melkveehouderij - biologische landbouw - trifolium repens - aardwormen - bodemstructuur - bodemwaterretentie - wortels - grass-clover swards - dairy farming - organic farming - trifolium repens - earthworms - soil structure - soil water retention - roots
White clover has a lower root biomass and a higher abundance of earthworms than grass. This might have an impact on the ecosystem services soil structure maintenance and water regulation when white clover is introduced in the grassland on organic dairy farms. We investigated the root biomass, the abundance of earthworms and a selection of soil physical parameters in white clover, grass-clover, and grass with and without N fertilizer. The treatment with clover-only had a lower root biomass, a lower C/N-ratio of the roots, a higher abundance of earthworms, a higher number of earthworm burrows, a lower penetration resistance at the 20-30 cm soil layer and a lower proportion of crumbs in the soil, than the other treatments. This confirms the literature that pure clover stimulates the ecosystem services of water regulation, but is less conducive to soil structure maintenance. However, the grass-clover mixture did not differ significantly from the grass treatments, but differed from pure clover in a higher percentage of soil crumbs. We infer that, when clover is introduced in grassland on organic dairy farms to fix atmospheric N2, the mixture of grass and clover maintains the positive impact of grass roots on soil structure but only may show a positive effect of clover-only on water regulation with a higher clover percentage in the dry matter.
Wormen ploegen akker in drie jaar
Faber, J.H. - \ 2011
Kennis Online 8 (2011)juli. - p. 9 - 9.
aardwormen - ecosysteemdiensten - bodemfauna - earthworms - ecosystem services - soil fauna
Regenwormen en schimmels in de bodem hun werk laten doen in plaats van ploegen verbetert de grond en helpt tegen ziekten. Alleen heb je pas na vijf tot tien jaar profijt van omschakeling van ploegen naar niet-kerende bodembewerking.
Anecic earthworms and associated ecosystem services in a ley-arable crop
Eekeren, N.J.M. van; Bommele, L. ; Bokhorst, J.G. ; Schouten, T. ; Reheul, D. ; Brussaard, L. - \ 2010
In: 19th World Congress of Soil Science, Soil Solutions for a Changing World, 1–6 August 2010, Brisbane, Australia. - - p. 9 - 11.
aardwormen - graslanden - bouwland - bodemvruchtbaarheid - bodemecologie - ecosysteemdiensten - earthworms - grasslands - arable land - soil fertility - soil ecology - ecosystem services
Een vruchtwisseling van gras en maïs zou duurzaam kunnen zijn in termen van nutriëntengebruik, maar het effect op regenwormen is nog onvoldoende bekend. Regenwormen zijn verzameld in permanent akkerland, permanent grasland en grond waarop een vruchtwisseling was toegepast. De hoeveelheid regenwormen was het hoogst in permanent grasland. Na gebruik als akkerland heeft de populatie heeft minstens drie jaar nodig om te herstellen. De populatie anenic wormen waren echter na deze periode nog niet hersteld.