Newsletter 11 | 9 October 2015

We gladly present you with another Centre for Wetland Ecology (CWE) newsletter full of information concerning Wetland Ecology.

This newsletter will come to you twice per year to inform you about CWE symposia, STOWA activities and to announce other events and news.

Bart Grutters (coordinator CWE)
Liesbeth Bakker (chair CWE)

Please e-mail us so we can spread news about any upcoming events, job offers, symposia, PhD defences or publications, either on our website, twitter or the next newsletter.


Upcoming Wetland events

Please check our website for a complete overview of events.


CWE Symposium 27 November 2015

The upcoming CWE symposium entitled 'Half a century of fundamental and applied wetland ecology: from acidification to climate change' is dedicated to the retirement of Prof. dr. Jan Roelofs. Please register on our website.


Upcoming STOWA events

  • 5 November, a course on Cyanobacteria and Water Management will be held in Amersfoort. More information.
  • 6 November, a symposium on Plastics in Water held in Utrecht. More information.
    • 12 November, a symposium on Geomorphological Stream Restoration held in Renswoude. More information.

    For a complete overview of STOWA events, please check the STOWA agenda.


    • Amsterdam Water Science announces symposium 'Aquatic systems under pressure: Global change and human impact'
      The Amsterdam Water Science (AWS) and Global Ecology (GE) symposium will be an international meeting dedicated to the presentation and discussion of a new collaboration program between the research groups in aquatic sciences of the University of Amsterdam (UvA) and the Free University Amsterdam (VU) aiming to involve both international and Dutch researchers and stakeholders. This two days symposium will be held on the 25th November 2015 at the Koninklijk Instituut voor de Tropen (KIT), Amsterdam and on the 26th November at Amsterdam Science Park. To register please send an e-mail to before 17 November 2015. For more information, please visit the website.
    • Lake Ohrid, located in Macedonia, is Europe's oldest lake and is home to over 200 endemic species and rich in biodiversity earning it protection by UNESCO. However, urbanisation threatens the lake and your support is needed. Please visit the website dedicated to saving Lake Ohrid to show your support.
    • The Foundation for Life Sciences and Society recently published a magazine about Climate Change wherein scientists explain its consequences. Read the magazine here.The CWE symposium on Growing Peat was well visited and participants enjoyed the spectacular venue (church of Broek in Waterland), the diverse programme and the excursion to the Volgermeerpolder. For pdfs of the talks, please visit our website.
    • Alfons (Fons) J.P. Smolders was appointed Professor by Special Appointment (Dutch: Bijzonder Hoogleraar) at Radboud University Nijmegen, with teaching and research remit: Applied Biogeochemistry. Prof. Smolders was appointed retroactively on the first of July 2015. He is working at the spin-off company of our Department, B-WARE Research Centre and has already been a guest scholar and guest teacher at the Institute for Water and Wetland Research (IWWR) of our Science Faculty for many years.


    Guest column: Wim Admiraal (UvA), "Prickling questions on silicate"

    Silicon is an abundant element in the earth crust dissolving in water as low concentrations of silicon hydroxide or silicate. Dissolved silicate can be taken up by organisms to fulfil special roles: the diatoms (in Dutch: kiezelalgen) possess a mechanism to polymerize silicates into cell walls with a characteristic structure. This deposition process is not energetically demanding –silicates form a cheap building material already used by ancient organisms such as radiolarians and sponges. Fig. 1 shows the immense complexity of silicate structures formed in radiolarians. The capacity to use silicate led to the evolutionary success of diatoms relatively late: this group of algae expanded as important photosynthetic producers in inland waters and the sea only 100 10x6 years ago.

    The role of the silicates for aquatic biota is long known and accordingly dissolved silicate in seawater and freshwater water is considered as a nutrient and its concentration is measured in water monitoring. Dissolved silicate is being depleted in the growing season during the spring bloom of diatoms; subsequently other algae dominate the phytoplankton. Silicate is a natural product presumably not much affected by human activities, unlike phosphate and nitrogen compounds that diffuse into water with a dramatic impact on nearly every aspect of aquatic systems. Remarkably a new Dutch textbook on inland waters (Hoogenboom, 2014, KNNV, 419 pp.) does not even hint to a role for silicate, while two other elements, iron and sulphur, interfering with the phosphorus cycle, are clearly explained. How come?

    Figure: Silicate structures in Cyrtoidae (marine radiolaria) described by Ernst Haeckel in the ninetieth century.

    Let us face another linkage of biogeochemical cycles. In recent years questions on elevated carbon dioxide levels in the atmosphere have triggered studies on climate change and ocean acidification and new insight into the role of silicate emerged. Emeritus professor Schuiling from Utrecht University proposed the enhanced erosion of common silicate rock (olivines) as a potent trap for carbon dioxide. In the process of both natural and enhanced weathering silicate minerals dissolve into surface water.  The primary goal of enhanced weathering is extra carbon dioxide trapping thereby reducing the acidification of water. The release of dissolved silicate is an associated natural process. A proposed global scale engineering of carbon dioxide is subject of scientific debate and rigorous testing needs to be done. Yet the local application of the natural mineral olivine has been simply started based on theory. Schuiling, a geologist, coined in 2012 that increased silicate dissolution could counteract the shift from diatoms to cyanobacteria in eutrophic Dutch waters and could be instrumental in combatting a nasty consequence of eutrophication: blooms of cyanobacteria. The idea was killed of by a team of prominent Dutch wetland scientists (de Senerpont Domis, van Donk, Lürling, Huisman and van Dam, 2013) in the magazine H2O, arguing that the mid-summer application of silicate would not stimulate the heavy diatom cells sinking to greater depth. Poor geologist that endeavours to cross the borders of wetland ecology! Are some established views on eutrophication to be revised? Is the exclusive focus on nitrogen and phosphorus scientifically sound?

    Currently there is some evidence that the silicate cycle of Dutch waters has been greatly modified. In Lake Marken dissolved silicate is always low and many years ago the water from the Rivers Rhine and Meuse proved to be depleted from silicate by diatom blooms stimulated by high nitrogen and phosphate concentrations (Admiraal et al., 1990, Biogeochemistry 9,175-185). There is also evidence on the importance of the silicate cycle brought up by recent studies of the group of Eric Struyf (Antwerp University, Struyf and Conley, 2012, Biogeochemistry 107, 9-18; see CWE symposium, 2010).  Silicate fixation by diatoms and marsh plants (notably reed) and dissolution of biogenic silica is clearly a basic ecosystem process with repercussions for the response to eutrophication. But why is silicate banned from our textbooks and banned from the toolbox of water management?  


    Centre for Wetland Ecology @ Twitter

    We recently launched the CWE twitter account to keep you up-to-date on everything related to wetland ecology between newsletters.




    PhD graduations

    • Mariska Weijerman (WUR), 16 September 2015, "An integrated ecosystem model for coral reef management. where oceanography, ecology and socio-economics meet". More information.
    • Erik Kleyheeg (UU/NIOO), 23 September 2015, "Seed dispersal by a generalist duck". More information.
    • Noël Diepens (Wageningen UR), 19 October 2015, "Sediment toxicity testing and prospective risk assessment of organic chemicals". More information.
    • Jose van Diggelen (B-WARE/RU Nijmegen), 4 November 2015, "Human impact on peatlands: from biogeochemical issues towards sustainable land use options". Personal website.


    Recent key publications

    • Bakker et al 2015. Assessing the role of large herbivores in the structuring and functioning of freshwater and marine angiosperm ecosystems. Ecography doi: 10.1111/ecog.01651.
    • Bodelier 2015. Bypassing the methane cycle. Nature doi:10.1038/nature14633.
    • van Diggelen et al 2015. Differential responses of two wetland graminoids to high ammonium at different pH values. Plant Ecology doi: 10.1111/plb.12398.
    • Fraaije et al. 2015. Dispersal versus environmental filtering in a dynamic system: drivers of vegetation patterns and diversity along stream riparian gradients. Journal of Ecology doi: 10.1111/1365-2745.12460.
    • Harpenslager et al 2015. Rewetting former agricultural peatlands: Topsoil removal as a prerequisite to avoid strong nutrient and greenhouse gas emissions. Ecological Engineering doi: 10.1016/j.ecoleng.2015.08.002.
    • Janssen et al. 2015. Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective. Aquatic Ecology doi:10.​1007/​s10452-015-9544-1.
    • Kim et al 2015Combined effects of carbon, nitrogen and phosphorus on CH4 production and denitrification in wetland sediments. doi:10.1016/j.geoderma.2015.03.015.
    • Kuiper et al 2015. Food-web stability signals critical transitions in temperate shallow lakes. Nature Communications doi:10.1038/ncomms8727.
    • Robroek et al 2015Peatland vascular plant functional types affect methane dynamics by altering microbial community composition. Journal of Ecology doi: 10.1111/1365-2745.12413.
    • Swillen et al. 2015. Inbreeding and adaptive plasticity: an experimental analysis on predator‐induced responses in the water flea Daphnia. Ecology and Evolution doi: 10.1002/ece3.1545.
    • Veraart et al 2015Beyond nitrogen: The importance of phosphorus for CH4 oxidation in soils and sediments. Geoderma doi:10.1016/j.geoderma.2015.03.025.
    • Wright et al. 2015. Flooding disturbances increase resource availability and productivity but reduce stability in diverse plant communities. Nature Communications doi: 10.1038/ncomms7092