Curriculum Vitae
Name: Verschoor, Antonie Martinus (1971)
Education:
- BSc/MSc Aquatic Ecology and Water Quality Management, Wageningen University (The Netherlands), 1997.
- PhD Aquatic Ecology, Radboud University, Nijmegen (The Netherlands) 2005.
Professional experience:
- Trainee, Gulf Fisheries Centre, Department of Fisheries and Oceans, Moncton (Canada), 1996.
- Guest scientist, Department of Aquatic Ecology and Water Quality Management, Wageningen University (The Netherlands), 1997.
- Consultant lake restoration/fish monitoring/biomanipulation, Witteveen+Bos raadgevende ingenieurs bv, Deventer (The Netherlands), 1997-1999.
- PhD researcher inducible defences in plankton, Netherlands Institute of Ecology, Centre for Limnology, Nieuwersluis (The Netherlands), 1999-2004.
- Researcher/developer, AquaCultura bv (algal culturing company), Borculo (The Netherlands), 2004-2005.
- Postdoctoral fellow, Netherlands Institute of Ecology, Centre for Limnology, Nieuwersluis (The Netherlands), & guest @ University of Amsterdam (The Netherlands), Institute for Biodiversity and Ecosystem Dynamics, 2005-2008.
- External advisor Ingrepro bv (algal micro ingredients), Zutphen (The Netherlands), 2005-2006.
- CSO/head R&D Ingrepro micro ingredients bv, 2007-present.
Expertise
Micro-algae in food, feed and non-food applications
Microalgae are interesting ingredients in food and feed. Their annual areal yield is much higher than traditional (terrestrial) crops, e.g. open pond algal cultures already yield 20-30 tons/ha. For their growth, micro-algae require relatively cheap inorganic nutrients, which are even considered wastes in other (agro-)industries, such as CO2, NO3and PO4. These nutrients are converted into many useful compounds, such as proteins, carbohydrates, fatty acids, anti-oxydants, phytohormones, pigments and vitamins. These highly valued compounds make that micro-algae are perfect ingredients in many feed and food applications. I am involved in pilot studies on applications of micro-algae as source of vitamins, pigment and trace elements, and as immuno- and olfactory stimulants in many feed and food applications. Recently, interest has grown in algae as reneweble feedstock for non-food applications.
Ecological stoichiometry
Ecological stoichiometryuses the balance of energy (carbon) and nutrients (N,P) in organisms to describe the complex relationships between biota and biogeochemical cycles. By using the same mass-balance approach as employed in routine chemistry, ecological stoichiometry gives insight in the complex feedbacks and constraints operating on the fluxes of nutrients, carbon and the biotic components of food webs. In primary producers, carbon fixation and nutrient uptake are more or less uncoupled, meaning that they are flexible in their stoichiometry and can vary widely in carbon:nutrient ratios. Consumers, however, have a tighter stoichiometry and generally lower carbon:nutrient ratios (i.e. higher relative nutrietn content), and have to take up their nutrients in ratios as supplied by their food. This implies that when the carbon content of their food increases, a larger fraction of carbon (the non-limiting element) will be “in excess” relative to the herbivore demands, and will be lost as excretion, egestion or respiration. This will lower the growth efficiency, and thus limit the growth of zooplankton. Such effects may arise when either nutrient availablility to primary consumers decreases, AND/OR when carbon fixation increases (e.g. due to better light or CO2 availability). I am currently working on a project (STOICHWEB) that investigates the effects of increasing atmospheric CO2 on pelagic food webs, using the perspective of ecological stoichiometry.
Inducible defences
Most of my PhD thesis work has been on inducible defences in the plankton. Inducible defences are an intermediate strategy between being permanently defended and permanently undefended. High predation pressures induce a transitation from being undefended to defended, whereas low predation pressures induce the reverse process. The system that I have been working with, consists of the chlorophyte Scenedesmus (phytoplankton) , the herbivorous rotifer Brachionus (zooplankton) and the carnivorous rotifer Asplanchna (zooplankton). Grazing-released chemicals from Brachionus induce defensive colony formation in Scenedesmus, whereas chemicals from Asplanchna induce spine formation in Brachionus.
Together with my colleagues Nico Helmsing, Irene van der Stap, and Miquel Lürling (Wageningen University), I studied various defensive strategies (no, inducible and permanent) in Scenedesmus and related species, in response to grazing chemicals from Brachionus and the herbivorous cladoceran Daphnia. This showed that different strains have different defence strategies, but that there is no difference in response to the two different herbivores. With Yegor Zadereev (Instituteof Biophysics, Krasnoyarsk, Russia), I investigated the effectivity of defensive colony formation by performing grazing experiments on defended and undefended Scenedesmus. This showed that the effectivity of defence varies among strains, and that there is a trade-off between benefits (reduced predation) and costs (increased sedimentation) of colony formation. Work that I did with Ozan Bekmezci (Middle EastUniversity, Ankara) in the Limnotrons showed that sedimentation costs can be considerable under semi-natural conditions. Theoretical work on this system (Scenedesmus, Brachionus, Asplanchna) that I did together with Matthijs Vos, Wolf Mooij, Bob Kooi, Felix Waeckers and Don DeAngelis suggests that inducible defences, in contrast to no or permanent defences, give a gradual instead of a stepwise response to enrichment, and that inducible defences stabilise dynamics. Together with Irene van der Stap and Nico Helmsing we performed experiments with this system to test these predictions. The results revealed that inducible defences are indeed capable of stabilising large population fluctuations.
Projects
STOICHWEB (Effects of increased pCO2 on freshwater pelagic ecosystems through hydrodynamical-chemical coupling: a stoichiometric perspective)
Atmospheric carbon dioxide levels are currently increasing at unprecedented rates. Although this is known to cause the so-called ‘global warming’, the direct effects of CO2 on ecosystems are hardly understood. Freshwater lakes are particularly vulnerable to raised CO2, because this additional carbon will reach these lakes both through direct atmospheric exchange, and through runoff from increased terrestrial production in the surrounding watershed. This project aims to identify changes in food web and ecosystem functioning due to increased partial CO2 pressure (pCO2), from a stoichiometric perspective. Ecological stoichiometry studies the complex relationships between biota and biogeochemical cycles, using the balance between carbon and nutrients in organisms. For a reliable assessment of potential ecosystem effects, accurate assessment of the interactions and feedbacks between mixing regime, pelagic carbon and nutrient cycles, and living organisms, is essential.
With increasing pCO2, we expect that phytoplankton, the primary producers in the water column, will face a decoupling between photosynthesis and nutrient uptake with increasing dissolved inorganic carbon. This will lead to a higher carbon:nutrient ratio, which decreases their food quality for herbivorous zooplankton, which will in turn have a lower food quality for their consumers (insects, fish). Furthermore, increased pCO2 will cause changing competitive balances between species, increase the chance of extinctions due to stoichiometric deficiencies, lower the carrying capacity for higher trophic levels and increase the chance of catastrophic shifts in the ecosystem.
To investigate these hypotheses and to integrate processes at different levels, our approach is to combine small- and large scale experimental work with modelling and long-term data from real lakes. Chemostat experiments will be done to investigate the expected shifts in competitive balance in the food web. A biological community model will be developed and validated based on these chemostat experiments. An existing turbulence model that describes stratification and mixing processes will be extended to include carbon and nutrient cycling. The coupled physical-chemical model will then be linked to the biological model. Large scale experiments will be performed in our unique facility consisting of 8 replicate mesoscale laboratory ecosystems (Limnotrons). First, experiments are required to assess carbon and nutrient (phosphorus) exchange for calibration of the turbulence model. Validation of this model will be done using real lake and climate data. The integrated physical-chemical-biological model will yield more detailed hypotheses on changes in ecosystem structure and functioning, which will be tested with large-scale experiments. The validated model will be used to make prognoses for effects of increased pCO2 on food web structure and functioning for four basic types of lakes, which vary in alkalinity and mixing behaviour.
Co-Operation
Applicants and co-applicants involved in STOICHWEB
Prof. Dr. Ellen van Donk
Netherlands Institute of Ecology, Centre for Limnology, Nieuwersluis
Prof. Dr. Jef Huisman
University of Amsterdam (Netherlands), Institute for Biodiversity and Ecosystem Dynamics
Dr. Peter Schippers
Wageningen University (Netherlands), Aquatic Ecology and Water Management Group
Prof. Dr. Dag O. Hessen, Dr. Tom Andersen
University of Oslo (Norway), Department of Biology
Prof. Dr. James J. Elser
Arizona State University, Tempe (U.S.A.), School of Life Sciences
Prof. Dr. Frank Peeters
University of Konstanz (Germany), Limnological Institute, Department of Environmental Physics
Prof. Dr. Jotaro Urabe
Tohoku University, Sendai (Japan), Ecology and Evolutionary Biology
Selected Publications
1999
De Lange, H.J., A.M. Verschoor Verschoor, R. Gylstra, J.G.M. Cuppen & E. Van Donk, 1999. Effects of artificial ultraviolet-B radiation on experimental aquatic microcosms. Freshwater Biology 42: 545-560.
2001
Schippers, P., A.M. Verschoor Verschoor, M. Vos & W.M. Mooij, 2001. Does "supersaturated coexistence" resolve the "paradox of the plankton"? Ecology Letters 4: 404-407.
2003
Lürling, M., & A.M. Verschoor Verschoor, 2003. F0-spectra of chlorophyll fluorescence for the determination of zooplankton grazing. Hydrobiologia 491: 145-157.
Verschoor, A.M. M., J.J. Takken, B. Massieux & J. Vijverberg, 2003. The Limnotrons: a facility for experimental community and food web research. Hydrobiologia 491: 357-377.
2004
Jensen, T.C., & A.M. Verschoor Verschoor, 2004. Food quality effects on life history of Brachionus calyciflorus. Freshwater Biology 49: 1138–1151.
Vos, M., A.M. Verschoor Verschoor, B.W. Kooi, F.L. Wäckers, D.L. DeAngelis & W.M. Mooij, 2004. Inducible defenses and trophic structure. Ecology 85: 2783–2794.
Verschoor, A.M. M., I. van der Stap, N.M. Helmsing, M. Lürling, & E. Van Donk, 2004. Morphological responses of different Scenedesmaceae (Chlorococcales, Chlorophycae) to grazing chemicals from two contrasting zooplankton taxa. Journal of Phycology 40: 808–814.
Verschoor, A.M. M., M. Vos, & I. van der Stap, 2004. Inducible defences prevent strong population fluctuations in bi- and tritrophic food chains. Ecology Letters 7: 1143–1148.
2005
Ptacnik, R., G.D. Jenerette, A.M. Verschoor Verschoor, A.F. Huberty, A.G. Solimini, & J.D. Brookes. Applications of ecological stoichiometry for sustainable acquisition of ecosystem services. Oikos 109: 52-62.
Verschoor, A.M., 2005. Hard to Handle: Inducible Defences in Plankton. PhD thesis Radboud University Nijmegen, 200 pp.
Verschoor, A.M. M., H. Boonstra & T. Meijer, 2005. Stable isotope labelling for the study of zooplankton feeding. Hydrobiologia 546: 535–549.
2007
Bontes, B.,A.M. Verschoor, M.L. Dionisio-Pires, E. van Donk &B.W. Ibelings, 2007. Functional response of Anodonta anatina feeding on a green alga and four strains of cyanobacteria, differing in shape, size and toxicity. Hydrobiologia 584: 191–204.
Van der Stap, I., M. Vos, A.M. Verschoor, N.R. Helmsing, & W.M. Mooij. Induced defenses in herbivores and plants differentially modulate a trophic cascade. Ecology xxxx:xx-xx
Verschoor, A.M., Y.S. Zadereev & W.M. Mooij, 2007. Infochemical-mediated trophic interactions between the rotifer Brachionus calyciflorus and its food algae. Limnol. Oceanogr. 52(5): xx-xx
Links
PDF of my PhD thesis: Hard to Handle: Inducible Defences in Plankton
http://webdoc.ubn.ru.nl/mono/v/verschoor_a/hardtoha.pdf
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