David Thieltges is an ecologist investigating the role of parasites in ecosystems. ‘Parasites are still a relatively new research area for ecology. For a long time, the prevailing dogma was that parasites would not play a major role in ecology, but that view has now been abandoned. Obviously, parasites have direct effects on species. That was very clear, for example, during the outbreaks of the seal virus and with the high mortality of eider ducks at the turn of the century. Those ducks were found to be infected by a parasitic worm. In addition, parasites can cause more subtle and indirect effects. For example, if shellfish are affected by a parasite and are weakened or perish, this also has an effect on an entire ecosystem. Shellfish-eating birds then have less to eat, but those weakened shellfish also filter fewer algae from the water, which in turn has consequences for the rest of the system.’
‘Sometimes, the effects of parasites are quite bizarre. Male crabs that suffer from the parasitic crab hacker barnacle start to behave like egg-bearing females. They descend into deeper areas and fan water over the parasite on their belly as if it were an egg sac.’
‘Parasites are usually strongly dependent on specific hosts. A high diversity of parasites is therefore usually associated with a high biodiversity in general. So, in contrast to (veterinary) medicine, “many parasites” are therefore good news in ecology. Parasites only give rise to problems if the general diversity becomes too low. That knowledge has already been translated into new methods for fish farming. For example, salmon are no longer reared in a monoculture but in combination with other species that can keep the parasites at bay.’
‘In another part of my work, I examine the effects of climate change and species invasions on parasites. Due to southern species such as the seabass shifting northwards in relation to warming waters, or because we introduce exotic species ourselves, such as the Pacific oyster, new parasites are also entering our environment and can influence our ecosystems.’
I am a marine ecologist with a soft spot for parasites. My research revolves around understanding the ecological role of parasites in marine ecosystems on various spatial and organizational scales.
Using lab and field experimental approaches, my research group studies the effects of parasites on marine host individuals, populations and communities. We are also interested in how parasites influence the topology and dynamics of food webs. Another line of research aims to understand the patterns and processes underlying infections of marine hosts. This includes work on the role of ambient biodiversity in affecting parasite transmission and disease risk as well as studies on the effects of global changes such as rising temperatures and biological invasions on marine parasites and their hosts. Finally, we study large-scale patterns of parasitism using literature-based datasets and biogeographical and macroecologial approaches in order to understand the forces that have shaped parasitism in the sea.
Since 2020: Honorary Professor 'Marine Parasite Ecology', University of Groningen (NL)
Since 2015: Lecturer in the Marine Biology MSc programme of the University of Groningen (NL)
Since 2014: Senior research scientist at NIOZ Royal Netherlands Institute of Sea Research (NL)
2010-2014: Research scientist at NIOZ Royal Netherlands Institute of Sea Research (NL)
2007-2010: DFG Postdoc fellowship at the University of Otago (NZ)
2006/2007: DAAD Postdoc fellowship at the Aarhus University (DK)
Please find a complete list of my NIOZ-publications at the bottom of this webpage or on Publons/ResearcherID. You can download pdfs of my publications on ResearchGate. I also have a Google Scholar and a Twitter account.
Opinion piece on effects of invasive species in the Wadden Sea (in Dutch, 2020) in Friesch Dagblad.
Special issue published in 2016 based on an international NIOZ–AWI symposium held on Texel NL from 10–14 March 2014: ‘Ecology and evolution of marine parasites and diseases’. Co-edited together with Mathias Wegner (AWI, D).
Trilateral (DK, D, NL) report describing and evaluating the current ecological status of the Wadden Sea: Wadden Sea Quality Status Report 2017. Contribution of thematic report and as member of Editorial Board.
Our work covered in WadWeten (in Dutch)
Our work covered in the press, radio and science blogs
2018: BKO/UTQ (Basiskwalificatie Onderwijs/University Teaching Qualification), University of Groningen (NL)
2012-2013: Management Development Training, Leeuwendaal Instituut (NL)
2006: PhD in Ecology (summa cum laude), Christian Albrechts University Kiel & Alfred Wegener Institute for Polar and Marine Research, Wadden Sea Station Sylt (D)
1993-2001: MSc/Diplom in Biology (summa cum laude), major in zoology/ecology and minors in conservation biology, evolution & systematics and philosophy, Philipps University Marburg (D)
1996/97: Visiting student for an academic year (ecology, evolution, palaeontology and history of science), University of Edinburgh, Scotland
2007: DFG Postdoc fellowship for a three years stay at the University of Otago (NZ)
2006: DAAD Postdoc fellowship for a 9 months stay at Aarhus University (DK)
Maral Khosravi - PhD student (co-supervisor). Project 'Interactive impact of thermal stress and parasitism on gastropods in an extreme and variable sea environment, the Persian Gulf'. GEOMAR & Kiel University(D); main supervisor and promotor: Martin Wahl (GEOMAR, D).
Annika Cornelius - PhD student (co-supervisor). Project 'Interspecific interactions and ecosystem effects of invasive mud crabs'. AWI Sylt & Bremen University (D), main supervisor: Christian Buschbaum (AWI Sylt, D); promotor: Kai Bischof (University Bremen, D).
Claudia Bommarito (2020, co-supervisor). Project 'Global warming effects on host-parasite interactions in common molluscs of the Adriatic and Baltic Sea'. GEOMAR & Kiel University (D); main supervisor and promotor: Martin Wahl (GEOMAR, D).
Anouk Goedknegt (2017) Thesis title: 'Pacific oysters and parasites: species invasions and their impact on parasite-host interactions', defense at the Free University Amsterdam (VU), The Netherlands. Promotor: Jaap van der Meer
Former MSc students Wouter Koch (RUG Groningen, NL), Tabea Stier (University Hohenheim, D), Marieke Feis (RUG Groningen, NL), Reinier Nauta (RUG Groningen, NL), Jarco Havermans (RUG Groningen, NL), Anne Karin Schuster (University of Landau, D), Marin van Regteren (RUG Groningen, NL), Caroline Liddell (Wageningen University, NL), Annabelle Dairain (Pierre et Marie Curie College Parais, F), David Shoesmith (RUG Groningen, NL), Boukje Heidstra (RUG Groningen, NL), Sarah Bedolfe (RUG Groningen, NL), Eeke Haanstra (RUG Groningen, NL), Romy Cartiere (University of Amsterdam, NL), Luca Prins (University of Wageningen, NL), Lotte Geerlings (University of Wageningen, NL), Tjibbe Stelwagen (RUG Groningen, NL), Mark Bouwmeester (RUG Groningen, NL), Tijs Joling (University of Amsterdam, NL), Joshua Dagoy (University of the Basque Country, E), Jeffrey Knol (RUG Groningen, NL), Tom van Splunter (Leiden University, NL), Nadine Bleile (RUG Groningen, NL), Rebecca MacKinnon (Utrecht University, NL)
Anke Hempel (D), Mirjana Markovic (D), Estefania Velilla (NL), Karlos Ribeiro de Moraes (BR), Wiem Boussellaa (PhD student; Sfax University, Tunisia), David Bello Jimenez (University of Malaga, E), Nadine Bleile (University of Freiburg, D), Svenja Kling (Heidelberg University, D)
Various research projects for MSc students are available all year round. They range from field studies over field and lab experiments to literature-based approaches. Please contact me for more details or check the NIOZ internship webpages.
I am curently teaching in courses in the Marine Biology MSc (and BSc) programme of the University of Groningen.
In addition, I teach in the NIOZ Marine Masters Summer Course.