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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    Copepod Prey Selection and Grazing Efficiency Mediated by Chemical and Morphological Defensive Traits of Cyanobacteria
    Rangel, Luciana M. ; Silva, Lúcia H.S. ; Faassen, Elisabeth J. ; Lürling, Miquel ; Ger, Kemal Ali - \ 2020
    Toxins 12 (2020)7. - ISSN 2072-6651
    cyanotoxin - functional trait - harmful algal bloom - neurotoxin - predator defense

    Phytoplankton anti-grazer traits control zooplankton grazing and are associated with harmful blooms. Yet, how morphological versus chemical phytoplankton defenses regulate zooplankton grazing is poorly understood. We compared zooplankton grazing and prey selection by contrasting morphological (filament length: short vs. long) and chemical (saxitoxin: STX- vs. STX+) traits of a bloom-forming cyanobacterium (Raphidiopsis) offered at different concentrations in mixed diets with an edible phytoplankton to a copepod grazer. The copepod selectively grazed on the edible prey (avoidance of cyanobacteria) even when the cyanobacterium was dominant. Avoidance of the cyanobacterium was weakest for the "short STX-" filaments and strongest for the other three strains. Hence, filament size had an effect on cyanobacterial avoidance only in the STX- treatments, while toxin production significantly increased cyanobacterial avoidance regardless of filament size. Moreover, cyanobacterial dominance reduced grazing on the edible prey by almost 50%. Results emphasize that the dominance of filamentous cyanobacteria such as Raphidiopsis can interfere with copepod grazing in a trait specific manner. For cyanobacteria, toxin production may be more effective than filament size as an anti-grazer defense against selectively grazing zooplankton such as copepods. Our results highlight how multiple phytoplankton defensive traits interact to regulate the producer-consumer link in plankton ecosystems.

    Risicobeoordeling blauwalgen in zwemwater : Nieuwe technieken voor de bepaling van de aanwezigheid van blauwalgtoxines
    Sollie, Susan ; Kardinaal, Edwin ; Faassen, E.J. - \ 2020
    Amersfoort : Stichting Toegepast Onderzoek Waterbeheer (STOWA) (Stowa rapport 2020-09) - ISBN 9789057738739 - 67
    Waterbeheerders voeren op grond van de Europese Zwemwaterrichtlijn analyses uit om in te schatten hoe groot het kans is op het voorkomen van blauwalgen(toxines) in zwemwater. Ze krijgen daarmee een beeld van het gezondheidsrisico voor zwemmers, op basis waarvan er zwemadviezen worden gegeven. De technieken die daarvoor nu worden gebruikt, meten alleen de hoeveelheden blauwalgen, maar niet de toxines die blauwalgen kunnen produceren, terwijl dat nu juist de ziekteverwekkende stoffen zijn. In dit onderzoek zijn de huidige technieken vergeleken met nieuwe technieken. Het gaat om technieken die direct(er) toxines bepalen. Hiervoor zijn in 2019 in totaal 103 watermonsters (afkomstig van 11 verschillende locaties) geanalyseerd met meerdere methoden. De uitkomsten zijn met elkaar vergeleken, waarbij de analyse van toxines met LC-MS/MS als 'gouden standaard’ is genomen. Het uiteindelijke doel is om een (kosten)effectieve analysetechniek te vinden die het meest geschikt is om het gezondheidsrisico voor zwemmers in kaart te brengen.
    Effects of guanotrophication and warming on the abundance of green algae, cyanobacteria and microcystins in Lake Lesser Prespa, Greece
    Maliaka, Valentini ; Verstijnen, Yvon J.M. ; Faassen, Elisabeth J. ; Smolders, Alfons J.P. ; Lürling, Miquel - \ 2020
    PLoS ONE 15 (2020)3. - ISSN 1932-6203

    Lake Lesser Prespa in Greece is a vital breeding habitat for the Dalmatian and Great White Pelican and a shelter for numerous rare and endemic species. However, eutrophication processes are distressing the lake system and the outbreaks of cyanobacterial blooms during the warm months may pose a threat to aquatic organisms due to the presence of microcystins (MCs). In this study we hypothesize that nutrients (eutrophication), nutrient-rich pelican droppings (guanotrophication) and warming (climate change) can affect the algal growth and MCs production in the water layer of Lake Lesser Prespa. Seston collected from three lake sites was incubated at ambient (20°C) and high (30°C) temperature with or without the addition of nutrients (nitrogen (N), phosphorus (P)), or pelican droppings. Results showed increased chlorophyll-a at higher temperature (30°C). N addition yielded higher chlorophyll-a levels than the non-treated water or when only P was added. The addition of both N and P as well as the addition of pelican dropping resulted in the highest chlorophyll-a at both temperatures. Notably, in the dropping-treatments, cyanobacteria and MCs were promoted while changes were evoked in the relative contribution of toxic MC-variants. Guanotrophication may thus influence the cyanobacterial dynamics and most likely their toxicity profile at Lesser Prespa.

    How the neurotoxin β-N-Methylamino-L-Alanine accumulates in bivalves: distribution of the different accumulation fractions among organs
    Lepoutre, Alexandra ; Faassen, E.J. ; Zweers, A.J. ; Lurling, M.F.L.L.W. ; Geffard, Alain ; Lance, E. - \ 2020
    Toxins 12 (2020)2. - ISSN 2072-6651
    The environmental neurotoxin β-methylamino-l-alanine (BMAA) may represent a risk for human health. BMAA accumulates in freshwater and marine organisms consumed by humans. However, few data are available about the kinetics of BMAA accumulation and detoxification in exposed organisms, as well as the organ distribution and the fractions in which BMAA is present in tissues (free, soluble bound or precipitated bound cellular fractions). Here, we exposed the bivalve mussel Dreissena polymorpha to 7.5 µg of dissolved BMAA/mussel/3 days for 21 days, followed by 21 days of depuration in clear water. At 1, 3, 8, 14 and 21 days of exposure and depuration, the hemolymph and organs (digestive gland, the gills, the mantle, the gonad and muscles/foot) were sampled. Total BMAA as well as free BMAA, soluble bound and precipitated bound BMAA were quantified by tandem mass spectrometry. Free and soluble bound BMAA spread throughout all tissues from the first day of exposure to the last day of depuration, without a specific target organ. However, precipitated bound BMAA was detected only in muscles and foot from the last day of exposure to day 8 of depuration, at a lower concentration compared to free and soluble bound BMAA. In soft tissues (digestive gland, gonad, gills, mantle and muscles/foot), BMAA mostly accumulated as a free molecule and in the soluble bound fraction, with variations occurring between the two fractions among tissues and over time. The results suggest that the assessment of bivalve contamination by BMAA may require the quantification of total BMAA in whole individuals when possible.
    Usability of the bivalves Dreissena polymorpha and Anodonta anatina for a biosurvey of the neurotoxin BMAA in freshwater ecosystems
    Lepoutre, A. ; Hervieux, J. ; Faassen, E.J. ; Zweers, A.J. ; Lurling, M. ; Geffard, A. ; Lance, E. - \ 2020
    Environmental Pollution 259 (2020). - ISSN 0269-7491
    Anodonta anatina - Bioaccumulation - Biosurvey - Dreissena polymorpha - β-Methylamino-L-alanine

    The environmental neurotoxin β-methylamino-L-alanine (BMAA) may represent a risk for human health in case of chronic exposure or after short-term exposure during embryo development. BMAA accumulates in freshwater and marine organisms consumed by humans. It is produced by marine and freshwater phytoplankton species, but the range of producers remains unknown. Therefore, analysing the phytoplankton composition is not sufficient to inform about the risk of freshwater contamination by BMAA. Filter-feeders mussels have accumulation capacities and therefore appear to be relevant to monitor various pollutants in aquatic ecosystems. We investigated the suitability of the freshwater mussels Dreissena polymorpha and Anodonta anatina for monitoring BMAA in water. Both species were exposed to 1, 10, and 50 μg of dissolved BMAA/L daily for 21 days, followed by 42 days of depuration in clean water. On days 0, 1, 7, 14, and 21 of exposure and 1, 7, 14, 21 and 42 of depuration, whole D. polymorpha and digestive glands of A. anatina were sampled, and the total BMAA concentration was measured. D. polymorpha accumulated BMAA earlier (from day 1 at all concentrations) and at higher tissue concentrations than A. anatina, which accumulated BMAA from day 14 when exposed to 10 μg BMAA/L and from day 7 when exposed to 50 μg BMAA/L. As BMAA accumulation by D. polymorpha was time and concentration-dependent, with a significant elimination during the depuration period, this species may be able to reflect the levels and dynamics of water contamination by dissolved BMAA. The species A. anatina could be used for monitoring water concentrations above 10 μg BMAA/L. D. polymorpha and A. anatina could be used to biomonitor BMAA in fresh water.

    Welke invloed heeft blauwalg op de landbouwgewassen?
    Faassen, Els - \ 2019

    Dat blauwalgen kunnen zorgen voor huidirritatie is algemeen bekend. Dat de bacterie mogelijk ook gevaarlijk is voor landbouwgewassen weten minder mensen. Toch laten steeds meer onderzoeken zien dat blauwalggif in voedsel schadelijk is voor de volksgezondheid.

    Methods for the analysis of cyanobacterial toxins: fit for purpose?
    Faassen, Els - \ 2019
    Toxic benthic cyanobacteria in The Netherlands, first results of a three year survey
    Faassen, E.J. ; Demarteau, Marta - \ 2019
    Potentieel toxisch fytoplankton in productiegebieden van tweekleppige weekdieren : evaluatie van het Nederlandse monitoringsprogramma met voorstellen voor een alternatieve aanpak
    Faassen, E. ; Bovee, T. ; Klijnstra, M. ; Alewijn, M. ; Gerssen, A. - \ 2018
    Wageningen : RIKILT Wageningen University & Research (RIKILT-rapport 2018.002) - 55
    Feit of Fictie: Hoe gevaarlijk is blauwalg?
    Faassen, Els - \ 2018

    Volgens een ecoloog in het AD is blauwalg veroorzaker van onder andere dementie, en nog een hoop andere ziektes. Heeft hij gelijk of is die stelling toch wat overdreven?

    Is the density of potentially toxic phytoplankton a reliable indicator for the presence of toxins in Dutch marine bivalves?
    Faassen, Els - \ 2018
    Cyanobacterial Blooms and Microcystins in Southern Vietnam
    Trung, Bui ; Dao, Thanh Son ; Faassen, Els ; Lürling, Miquel - \ 2018
    Toxins 10 (2018)11. - ISSN 2072-6651
    aquaculture - cyanobacteria - cyanotoxins - Mekong river

    Studies on cyanobacteria in Vietnam are limited and mainly restricted to large reservoirs. Cyanobacterial blooms in small water bodies may pose a health risk to local people. We sampled 17 water bodies in the vicinity of urban settlements throughout the Mekong basin and in southeast Vietnam. From these, 40 water samples were taken, 24 cyanobacterial strains were isolated and 129 fish, 68 snail, 7 shrimp, 4 clam, and 4 duck samples were analyzed for microcystins (MCs). MCs were detected up to 11,039 µg/L or to 4033 µg/g DW in water samples. MCs were detected in the viscera of the animals. MC-LR and MC-RR were most frequently detected, while MC-dmLR, MC-LW, and MC-LF were first recorded in Vietnam. Microcystis was the main potential toxin producer and the most common bloom-forming species. A potential health hazard was found in a duck⁻fish pond located in the catchment of DauTieng reservoir and in the DongNai river where raw water was collected for DongNai waterwork. The whole viscera of fish and snails must be completely removed during food processing. Cyanobacterial monitoring programs should be established to assess and minimize potential public health risks.

    A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins
    Mantzouki, E. ; Campbell, J. ; Loon, E. van; Visser, P. ; Konstantinou, I. ; Antoniou, M. ; Giuliani, G. ; Machado-Vieira, D. ; Gurjão de Oliveira, A. ; Maronić, D.Š. ; Stević, F. ; Pfeiffer, T.Ž. ; Vucelić, I.B. ; Žutinić, P. ; Udovič, M.G. ; Plenković-Moraj, A. ; Tsiarta, N. ; Bláha, L. ; Geriš, R. ; Fránková, M. ; Christoffersen, K.S. ; Warming, T.P. ; Feldmann, T. ; Laas, A. ; Panksep, K. ; Tuvikene, L. ; Kangro, K. ; Häggqvist, K. ; Salmi, P. ; Arvola, L. ; Fastner, J. ; Straile, D. ; Rothhaupt, K.O. ; Fonvielle, J. ; Grossart, H.P. ; Avagianos, C. ; Kaloudis, T. ; Triantis, T. ; Zervou, S.K. ; Hiskia, A. ; Gkelis, S. ; Panou, M. ; McCarthy, V. ; Senerpont Domis, L.N. de; Seelen, L. ; Verstijnen, Y. ; Lürling, M. ; Maliaka, V. ; Faassen, E.J. - \ 2018
    Scientific Data 5 (2018). - ISSN 2052-4463 - 13 p.
    Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.
    Organ distribution of the neurotoxin β-N-methylamino-L-alanine in the freshwater mussel Dreissena polymorpha
    Lepoutre, Alexandra ; Faassen, E.J. ; Geffard, Alain ; Lance, Emilie - \ 2018
    - 1 p.
    The impact of warming and nutrients on algae production and microcystins in seston from the iconic lake lesser Prespa, Greece
    Maliaka, Valentini ; Faassen, Els ; Smolders, Alfons J.P. ; Lürling, Miquel - \ 2018
    Toxins 10 (2018)4. - ISSN 2072-6651
    Bioassay - Climate change - Cyanotoxins - Eutrophication - Nutrient addition
    Lake Lesser Prespa and its adjacent pond, Vromolimni in Greece, is a shallow freshwater system and a highly protected area hosting an exceptional biodiversity. The occurrence of microcystins (MCs) producing cyanobacterial blooms in these waters during recent years can be harmful to the wildlife. We tested the hypothesis that both cyanobacterial biomass and MCs are strongly influenced by nutrients (eutrophication) and warming (climate change). Lake and pond water was collected from two sites in each water body in 2013 and incubated at three temperatures (20°C, 25°C, 30°C) with or without additional nutrients (nitrogen +N, phosphorus +P and both +N and +P). Based on both biovolume and chlorophyll-a concentrations, cyanobacteria in water from Lesser Prespa were promoted primarily by combined N and P additions and to a lesser extent by N alone. Warming seemed to yield more cyanobacteria biomass in these treatments. In water from Vromolimni, both N alone and N+P additions increased cyanobacteria and a warming effect was hardly discernible. MC concentrations were strongly increased by N and N+P additions in water from all four sites, which also promoted the more toxic variant MC-LR. Hence, both water bodies seem particularly vulnerable to further N-loading enhancing MC related risks.
    Genotoxic and cytotoxic effects on the immune cells of the freshwater bivalve Dreissena polymorpha exposed to the environmental neurotoxin BMAA
    Lepoutre, Alexandra ; Milliote, Nadia ; Bonnard, Marc ; Palos-Ladeiro, Mélissa ; Rioult, Damien ; Bonnard, Isabelle ; Bastien, Fanny ; Faassen, Elisabeth ; Geffard, Alain ; Lance, Emilie - \ 2018
    Toxins 10 (2018)3. - ISSN 2072-6651
    BMAA - Cytotoxicity - Freshwater bivalves - Genotoxicity - Hemocytes - Immunotoxicity
    The environmental neurotoxin β-N-Methylamino-L-alanine (BMAA) has been pointed out to be involved in human neurodegenerative diseases. This molecule is known to be bioaccumulated by bivalves. However, little data about its toxic effects on freshwater mussels is available, particularly on the hemolymphatic compartment and its hemocyte cells involved in various physiological processes such as immune defenses, digestion and excretion, tissue repair, and shell production. Here we exposed Dreissena polymorpha to dissolved BMAA, at the environmental concentration of 7.5 µg of /mussel/3 days, during 21 days followed by 14 days of depuration in clear water, with the objective of assessing the BMAA presence in the hemolymphatic compartment, as well as the impact of the hemocyte cells in terms of potential cytotoxicity, immunotoxicity, and genotoxiciy. Data showed that hemocytes were in contact with BMAA. The presence of BMAA in hemolymph did not induce significant effect on hemocytes phagocytosis activity. However, significant DNA damage on hemocytes occurred during the first week (days 3 and 8) of BMAA exposure, followed by an increase of hemocyte mortality after 2 weeks of exposure. Those effects might be an indirect consequence of the BMAA-induced oxidative stress in cells. However, DNA strand breaks and mortality did not persist during the entire exposure, despite the BMAA persistence in the hemolymph, suggesting potential induction of some DNA-repair mechanisms.
    Toxic cyanobacteria and cyanotoxins in European waters - recent progress achieved through the CYANOCOST action and challenges for further research
    Meriluoto, Jussi ; Blaha, Ludek ; Bojadzija, Gorenka ; Bormans, Myriam ; Brient, Luc ; Codd, Geoffrey A. ; Drobac, Damjana ; Faassen, Elisabeth J. ; Fastner, Jutta ; Hiskia, Anastasia ; Ibelings, Bastiaan W. ; Kaloudis, Triantafyllos ; Kokocinski, Mikolaj ; Kurmayer, Rainer ; Pantelić, Dijana ; Quesada, Antonio ; Salmaso, Nico ; Tokodi, Nada ; Triantis, Theodoros M. ; Visser, Petra M. ; Svirčev, Zorica - \ 2017
    Advances in Oceanography and Limnology 8 (2017)1. - ISSN 1947-5721
    Cyanobacteria - Cyanotoxins - Europe - Gaps of knowledge - Trends

    This review aims to summarise the outcomes of some recent European research concerning toxic cyanobacteria and cyanotoxins, with an emphasis on developments within the framework of the CYANOCOST Action: COST Action ES1105, Cyanobacterial Blooms and Toxins in Water Resources: Occurrence, Impacts and Management. Highlights of the Action include phycological and ecological studies, development of advanced techniques for cyanotoxin analysis, elucidation of cyanotoxin modes of action, management techniques to reduce cyanobacterial mass development, and research on methods and practices for cyanotoxin removal during drinking water treatment. The authors have identified a number of gaps in knowledge. Proposed directions for future research on toxic cyanobacteria and cyanotoxins are also discussed.

    Polyphasic toxicological screening of Cylindrospermopsis raciborskii and Aphanizomenon gracile isolated in Poland
    Rzymski, Piotr ; Poniedziałek, Barbara ; Mankiewicz-Boczek, Joanna ; Faassen, Els ; Jurczak, Tomasz ; Gągała-Borowska, Ilona ; Ballot, Andreas ; Lürling, Miquel ; Kokociński, Mikołaj - \ 2017
    Algal Research 24 (2017). - ISSN 2211-9264 - p. 72 - 80.
    Aphanizomenon gracile - Cyanotoxins - Cylindrospermopsis raciborskii - In vitro toxicity - α-γ,-Diaminobutyric acid

    Aphanizomenon gracile and Cylindrospermopsis raciborskii are extensively studied Nostocales of wide geographical distribution and have potential to produce toxins. However, a number of knowledge gaps regarding their toxicity and related health risks in certain locations, including Europe, exists. The present study applied a polyphasic approach to screen the toxicity of different strains of C. raciborskii (LBY-Cr, LBO-Cr and LKM-Cr) and A. gracile (LBY-Ag, LBN-Ag and LWI-Ag) isolated from five freshwater lakes of Western Poland. The following investigations were carried out: (i) in vitro toxicological studies employing human cells isolated from healthy donors; (ii) analytical screening for the presence of cylindrospermopsin (CYN), guanidinoacetate (GAA; initial CYN precursor and postulated general cyanobacterial metabolite), three microcystin (MC) analogues, β-N-methylamino-L-alanine (BMAA) and its isomer α-γ,-diaminobutyric acid (DAB), anatoxin-a (ATX) and ten saxitoxin (STX) analogues; and (iii) molecular studies of genes involved in CYN, GAA, MCs and ATX biosynthesis. Extracts of C. raciborskii LBY-Cr and A. gracile LBN-Ag caused a significant increase in the intracellular reactive oxygen content in human neutrophils during short-term (1 h) exposure and also led to lipid peroxidation and cell death. No cytotoxic effects were noted for the other tested strains. None of the toxin genes (cyrA, cyrJ, anaF and mcyE) and toxins (CYN, GAA, MCs, BMAA, ATX and STX) were detected. The only exception was DAB found at a concentration below 1.0 μg g− 1 dw in A. gracile LWI-Ag. It is the first time that cyanobacterial DAB producer has been identified in the Central European region. The study points to the production of as yet unknown metabolite(s) that may pose a relevant threat to human health through strains of C. raciborskii and A. gracile isolated from two Polish lakes, and adds to the general understanding of the toxicity of European strains of both species.

    Eutrophication and warming boost cyanobacterial biomass and microcystins
    Lurling, Miguel ; Oosterhout, Jean ; Faassen, Els - \ 2017
    Toxins 9 (2017)2. - ISSN 2072-6651
    Cell quota - Climate change - Cyanobacterial blooms - Cyanotoxins - Mitigation - Seston
    Eutrophication and warming are key drivers of cyanobacterial blooms, but their combined effects on microcystin (MC) concentrations are less studied. We tested the hypothesis that warming promotes cyanobacterial abundance in a natural plankton community and that eutrophication enhances cyanobacterial biomass and MC concentrations. We incubated natural seston from a eutrophic pond under normal, high, and extreme temperatures (i.e., 20, 25, and 30 °C) with and without additional nutrients added (eutrophication) mimicking a pulse as could be expected from projected summer storms under climate change. Eutrophication increased algal-and cyanobacterial biomass by 26 and 8 times, respectively, and led to 24 times higher MC concentrations. This effect was augmented with higher temperatures leading to 45 times higher MC concentrations at 25 °C, with 11 times more cyanobacterial chlorophyll-a and 25 times more eukaryote algal chlorophyll-a. At 30 °C, MC concentrations were 42 times higher, with cyanobacterial chlorophyll-a being 17 times and eukaryote algal chlorophyll-a being 24 times higher. In contrast, warming alone did not yield more cyanobacteria or MCs, because the in situ community had already depleted the available nutrient pool. MC per potential MC producing cell declined at higher temperatures under nutrient enrichments, which was confirmed by a controlled experiment with two laboratory strains of Microcystis aeruginosa. Nevertheless, MC concentrations were much higher at the increased temperature and nutrient treatment than under warming alone due to strongly promoted biomass, lifting N-imitation and promotion of potential MC producers like Microcystis. This study exemplifies the vulnerability of eutrophic urban waters to predicted future summer climate change effects that might aggravate cyanobacterial nuisance.
    The neurotoxin BMAA in aquatic systems : analysis, occurrence and effects
    Faassen, E.J. - \ 2016
    Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Miguel Lurling. - Wageningen : Wageningen University - ISBN 9789462577855 - 194
    cum laude - neurotoxins - aquatic environment - urban areas - effects - environmental impact - daphnia magna - elisa - water quality - analytical methods - aquatic ecology - neurotoxinen - aquatisch milieu - stedelijke gebieden - effecten - milieueffect - daphnia magna - elisa - waterkwaliteit - analytische methoden - aquatische ecologie

    Eutrophication is a major water quality issue and in many aquatic systems, it leads to the proliferation of toxic phytoplankton species. The neurotoxin β-N-methylamino-L-alanine (BMAA) is one of the compounds that can be present in phytoplankton. BMAA has been suggested to play a role in the neurodegenerative diseases Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis, although this hypothesis still needs to be confirmed. It is expected that the main human exposure pathways to BMAA are through direct contact with BMAA containing phytoplankton and through ingestion of BMAA contaminated food, such as fish and shellfish. However, reports on the occurrence of BMAA in aquatic systems have been conflicting and the cause of these reported differences was heavily debated. The use of different analytical methods seems to play a crucial role in the observed discrepancies, but initially, there was little consensus on which method produced most reliable results. The objectives of the work presented in this thesis therefore were to find out what has caused the differences in published results on BMAA concentrations, and to identify and produce reliable data on the presence of BMAA in aquatic systems. In addition, I aimed to determine the effect of BMAA exposure on a key species in many freshwater ecosystems, the grazer Daphnia magna.

    The performances of different analytical techniques were compared, and LC-MS/MS analysis, either preceded by derivatisation or not, was found to produce most reliable results. LC-FLD and ELISA should not be used for BMAA analysis, as both methods risk misidentifying BMAA or overestimating its concentrations due to their low selectivity. When reviewing literature on the presence of BMAA in aquatic systems, it was found that the observed discrepancies in results could be explained by the use of unselective analytical methods in some studies, and by severe reporting deficiencies in others. When only studies that used appropriate analytical techniques and that correctly reported their work were taken into account, it was shown that BMAA could be present in phytoplankton and higher aquatic organisms, in concentrations of µg/g dry weight or lower. These results are in agreement with our findings of BMAA in cyanobacterial scums from Dutch urban waters. In a 2008 screening, BMAA was found to be present in 9 out of 21 analysed cyanobacterial scums, at concentrations ranging from 4 to 42 µg/g dry weight. When this screening was repeated 8 years later with 52 similar samples, BMAA was detected below the quantification limit in one sample and quantified in another sample at 0.6 µg/g dry weight.

    In order to perform the work presented in this thesis, sensitive and selective analytical methods, mostly based on LC-MS/MS analysis without derivatisation, were developed. This resulted in a standard operating procedure for the underivatised LC-MS/MS analysis of BMAA in cyanobacteria. Also, a CYANOCOST initiated workshop was given, in which a group of scientists from 17 independent laboratories evaluated LC-MS/MS based methods in different matrices. A bound BMAA from found in the supernatant was the most abundant fraction in the positive samples that were tested: cycad seed, seafood and exposed D. magna. In addition, it was found that the deuterated internal standard used for quantification was not a good indicator for the release of BMAA from bound forms, resulting in unprecise quantification of total BMAA.

    BMAA was found to reduce survival, somatic growth, reproduction and population growth in D. magna. Animals did not adapt to BMAA exposure: exposed animals born from exposed mothers had a lower brood viability and neonate weight than animals exposed to BMAA, but born from unexposed mothers. In addition, D. magna was shown to take up BMAA from the growth medium and to transfer it to its offspring. D. magna therefore might be an important vector for BMAA transfer along the pelagic food chain, but whether BMAA plays a role in preventing zooplankton from controlling cyanobacterial blooms needs further investigation.

    Although BMAA research has much progressed between the start of this thesis’ work and its completion, some important questions still require an answer. Most urgently, it should be determined whether BMAA is indeed involved in the neurological diseases mentioned above, and if so, which doses trigger the onset of these diseases. Human exposure pathways should then be more systematically quantified, and it might be prudent to investigate if the occurrence of BMAA is restricted to aquatic systems, or whether sources from terrestrial systems contribute to BMAA exposure as well.

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