Newsletter 15 | 20 December 2017

Newsletter 15, 20 December 2017

We gladly present you a new 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.

Casper van Leeuwen (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 (released April 2018).

Newsletter contents

Upcoming events in the Netherlands

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  • Symposium "Medicijnresten in afvalwater: technieken, ontwikkelingen en alternatieven" 19 Januari 2018, Amersfoort. More information.
  • Symposium "Waterkwaliteit op de kaart IV" 25 Januari 2018, Utrecht. More information.
  • Symposium on Ecological Key Factors (Ecologische Sleutel Factoren) by STOWA on 14 - 15 March 2018, Amersfoort. More information.

CWE Symposium

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Over 80 attendants visited the CWE symposium on "Future of aquatic carbon: impacts, feedbacks and mitigation" in November. PDF's of the presentations are now available online on the CWE website.

Next CWE symposium: June 2018.

International conferences

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  • 15th International Symposium on Aquatic Plants, 18 - 23 February 2018, New Zealand. More information.

  • Society of wetland Scientists Europe Chapter symposium, April 30 - May 5 2018, Macedonia. The symposium will be held in the city of Ohrid, which is located on the bank of the deepest and most diverse lake of Europe. There will be field trips to this lake and to Lake Prespa, where two species of pelicans breed. More information.

  • Conference: “Restoration of Eutrophic Lakes: Current Practices and Future Challenges”, 4 – 6 June 2018, Finland. More information.

  • Association for the Sciences of Limnology and Oceanography (ASLO), 10 - 15 June 2018, Canada. More information.

  • Congress of the International Society of Limnology (SIL), 19 - 24 August 2018, China. More information.


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  • The Institute for Biodiversity and Ecosystem Dynamics (IBED-UvA) started using a new research vessel. The "R.V. Dreissena" will be used for research on Lake Markermeer. The construction of the R.V Dreissena is the result of a crowdfunding’s effort initiated by aquatic biologist Harm van der Geest (IBED-UvA). Until now, research was done with small dinghy’s that were not suitable to safely use in all weather conditions. Waves on Lake Markermeer can be as high as a meter. With the new ship both researchers and students are able to do research safely in all seasons, and during stormy conditions. More information.
  • Utrecht University started a "Biodiversity and Climate Variability Experiment" on the 11th of October, called "UU BioCliVE". This is an experiment manipulating plant diversity and future precipitation scenario to examine how biological diversity can provide us with natural insurance against climate variability. More information.

The UU BioCliVE experiment

  • Several wetland scientists have obtained new positions: Sarian Kosten (permanent position at Radboud University), Annelies Veraart (tenure track at Radboud University) and Arie Vonk (tenure track at University of Amsterdam). 
  • New course for PhD students on Aquatic Ecology 18 - 23 March 2018: "Robustness of aquatic ecosystems in the face of global change". More information.
  • The Vijfde Kennisdag Zoetwater took place on the 22nd of November, with presentations and an interactive market about optimizing water management. Particular attention was paid to pilot research projects and innovations (such as "smart weirs"), and it was discussed how to further expand existing alliances and find new topics for alliances among water managers.
  • On the 24th of November there was a Farewell Symposium for Prof. Riks Laanbroek of NIOO-KNAW/UU. There were lectures on microbes, plants, elements and how they are connected: a tribute to his work. More information.

Guest column: Studying mangrove forests at the Atlantic coast of Florida

Riks Laanbroek (NIOO-KNAW and Utrecht University)
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"In 2007, my colleague Jos Verhoeven of Utrecht University invited me to join him and Dennis Whigham of the Smithsonian Environmental Research Centre in Edgewater, Maryland, to the mangrove forests of Florida." Many of these mangrove forests border directly on holiday resorts and condominiums. To prevent nuisance from noxious midges and mosquitos, a large number of mangrove forests had been impounded in the fifties and sixties of the last century. However, after intensive tropical storms, these impoundments changed into huge bathtubs with prolonged standing water giving rise to deterioration of the vegetation. Hence, in the eighties the hydrological isolation of the impounded mangrove forests was partly lifted by including culverts in the dikes. The health of the mangrove vegetation improved again, but the problem of midges and mosquitos returned also. To solve this problem, it was decided to implement rotational impoundment management (RIM), meaning that the impoundment was flooded during the summer period, which is the period of insects proliferation, by pumping water from the bordering lagoon. The implementation of RIM was meant to start in 2009, which gave us the opportunity to measure plant and biogeochemical characteristics two subsequent years before summer flooding began. It was hypothesized that flooding the mangrove forest soil with water from the lagoon would improve the growth conditions of the plants by releasing stress factors such as drought and nutrient limitation. At the same time, flooding would inhibit aerobic processes in the soil by limiting the oxygen availability. One of these processes is nitrification that converts ammonium into nitrate. Under such conditions, the process of denitrification would become totally dependent on nitrate from the floodwater.

Left: Jos Verhoeven and Dennis Whigham in the dwarf Black Mangrove vegetation before RIM started; Right: Author in the dwarf Black Mangrove vegetation two years after RIM started.

With some interruptions, plant and biogeochemical characters of Black Mangrove forests were determined annually in March from 2007 - 2014. Measurements were done in an impoundment with RIM and as control also in an impoundment without RIM. The latter impoundment, however, experienced already a limited tidal regime since a dike breach in 1974. Soil samples were transported to the nearby Smithsonian Marine Station at Fort Pierce, and prepared for soil chemical, biogeochemical and microbial analyses. As hypothesized, summer flooding had a positive effect on the performance of the mangrove trees in the impoundment with RIM. The amount of organic nitrogen compounds in the soil also increased. At the same time the nitrification and denitrification potentials in the soils decreased to low levels. Notably, the amounts of organic nitrogen compounds and the nitrification and denitrification potentials in the soil of the impoundment without RIM changed in the same direction as in the impoundment with RIM. Hence, the changes in soil characteristics were not governed by the presence or absence of RIM, but by other, yet unknown environmental factors. Nevertheless, the positive outcome of the measurements is that by RIM the impounded mangrove forests resemble more a natural mangrove forest.

Being annually in Florida, I took the advantage of collecting freeze-drying mangrove forest soil samples for molecular analyses, and more specifically for analyzing the ammonia-oxidizing microbial community, my favorite pet microbes. By studying spatial effects of flooding on the distribution of ammonia-oxidizing microorganisms it was shown that soil beneath Red Mangroves growing at the lower intertidal zone had a different ammonia-oxidizing community than soil underneath Black Mangroves growing at the higher intertidal zone. Such a difference in community composition as observed in natural mangrove forest soils was less clear in an impounded forest soil. Hence, tide seems to be a governing factor in structuring ammonia-oxidizing microbial communities in mangrove forest soils. Differences in ammonia-oxidizing bacterial communities were also observed between different vegetation types as they occur in impounded Black Mangrove forests. The species that dominate in the vegetation with dwarf trees (i.e. Nitrosomonas aestuarii) was largely replaced by other species in soil beneath sparse or dense vegetation (e.g. Nitrosospira sp). Aerating ammonium-enriched suspensions of the soils underneath the sparse and dense vegetation led to a dominance of N. aestuarii within 6 days, showing that the in-situ ammonia-oxidizing communities below the sparse and dense vegetation were ammonium and/or oxygen limited. The analyses of temporal effects on size and composition of this community as performed by my colleagues Mariet Hefting of Utrecht University and Eiko Kuramae of the Netherlands Institute of Ecology (NIOO-KNAW) are still underway.


Design of the salt marsh experiment with the four treatments (a. control, b. leaf litter, c. seedlings, d. leaf litter plus seedlings).

The zones with mangrove trees is restricted to the tropics and the subtropics based on the number of frost days. In the last decades, it has been observed that likely by global warming the mangrove migrate north and south, and enter formerly mangrove-free salt marshes. Mangrove trees, and especially Red Mangrove trees, are well known for their tannin and polyphenolic contents that exceeds their content in the salt marsh grasses. Since tannins and polyphenolics bind to proteins, the activity of exoenzymes in salt marsh soil will be repressed upon the arrival of mangrove trees. This will then affect the cycling of carbon and nitrogen in salt marsh soils.

To study the size of such an effect of mangrove trees on the carbon and nitrogen cycle in a salt marsh soil, we performed an experiment with leaves and seedlings of the Red Mangrove in a Distichlis spicata dominated salt marsh on Merritt Island at the Atlantic coast of Florida. The grass in plots of one square meter was annually cut in March starting in 2011. In half of the plots, the cut grass was put back, while the other half received 300 g of Red Mangroves leaf litter mimicking the annual leaf litters fall. In a full factorial way, half of the plots were planted with seedlings of the Red Mangrove and the other half was not. Plant growth characteristics were determined annually in March, simultaneously with measurements on soil chemical, biogeochemical and microbial parameters. At the same time, a litterbag experiment with D. spicata litter was performed to study the effect of the presence of Red Mangroves on the decomposition of the aboveground salt marsh vegetation.

The presence of Red Mangrove leave litter stimulated the growth of Red Mangrove seedlings in the experimental plots, but the combination of Red Mangrove seedlings and leaf litter repressed the decomposition of D. spicata litter. Hence, migration of Red Mangrove trees may interfere with the carbon and nutrient cycling in the salt marsh by retarding organic matter decomposition on one site and immobilizing nutrients on the other. No effects of treatments were observed on microbial genes related to nitrogen cycling, which was likely due to the already existing nitrogen limitation of the salt marsh before the introduction of the mangrove trees. Upon arriving at the salt marsh in March 2015, frost appeared to have terminated the experiment. Hence, a natural end of our mangrove migration study.

PhD graduations

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  • Gijs van Dijk (RUN) 14 December 2017 12:30. "Peatlands affected by biogeochemical stressors" More information.
  • Michiel Verhofstad (NIOO-KNAW) 20 December 2017 18:00. "To mow or not to mow:  An ecological and societal perspective on submerged aquatic plant growth" More information.
  • Mandy Veldhuis (NIOO-KNAW) 19 Maart 2018 14:30 "Elements of carbon cycling, primary producers in aquatic systems under global change". Personal page.
  • Jelle Treep (UU) 21 Maart 2018 14:30. "Flying cheap; Modelling the passive movement of plants and animals". More information coming soon here.

Recent key publications

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  • Aben, R.C.H., Barros, N., van Donk, E., Frenken, T., Hilt, S., Kazanjian, G., Lamers, L.P.M., Peeters, E.T.H.M., Roelofs, J.G.M., de Senerpont Domis, L.N., Stephan, S., Velthuis, M., Van de Waal, D.B., Wik, M., Thornton, B.F., Wilkinson, J., DelSontro, T. & S. Kosten (2017) Cross continental increase in methane ebullition under climate change. Nature Communications 8: 1682.

  • Brouwer, E., Denys, L., Lucassen, E.C.H.E.T., Buiks, M. & T. Onkelinx (2017) Competitive strength of Australian swamp stonecrop (Crassula helmsii) invading moorland pools. Aquatic Invasions 12(3): 321–331.

  • Bush, T., Diao, M., Allen, R.J., Sinnige, R. Muyzer, G. & Huisman, J. (2017). Oxic-anoxic regime shifts mediated by feedbacks between biogeochemical processes and microbial community dynamics. Nature Communications 8 (#789)

  • Emsens, W.-J., Aggenbach, C.J.S. Smolders, A.J.P., Zak, D. & R. Van Diggelen (2017) Restoration of endangered fen communities: the ambiguity of iron–phosphorus binding and phosphorus limitation. Journal of Applied Ecology 54(6):1755–1764

  • Fraaije, R.G.A., Moinier, S. van Gogh, I. Timmers, R. van Deelen, J.J., Verhoeven, J.T.A. & M.B. Soons (2017) Spatial patterns of water-dispersed seed deposition along stream riparian gradients. PloS one 12 (9), e0185247

  • Garssen, A.G., Baattrup‐Pedersen, A. Riis, T. Raven, B.M. Hoffman, C.C., Verhoeven, J.T.A. & M.B. Soons (2017) Effects of increased flooding on riparian vegetation: Field experiments simulating climate change along five European lowland streams. Global Change Biology 23(8): 3052–3063

  • Harpenslager, S.F., Overbeek, C.C., van Zuidam, J.P., Roelofs, J.G.M., Kosten, S. & L.P.M. Lamers (2017). Peat capping: Natural capping of wet landfills by peat formation. Ecological Engineering,

  • Kleyheeg, E., Treep, J. Jager, M., Nolet, B.A. & M.B. Soons (2017) Seed dispersal distributions resulting from landscape‐dependent daily movement behaviour of a key vector species, Anas platyrhynchos. Journal of Ecology 105(5): 1279–1289

  • Monde, C., Syampungani, S., Rico, A. & P.J. van den Brink (2017) The potential for using red claw crayfish and hybrid African catfish as biological control agents for Schistosoma host snails. African Journal of Aquatic Science 42: 235-243

  • Overbeek, C.C., van der Geest, H.G., van Loon, E.E., Klink, A.D., van Heeringen, S., Harpenslager, S.F. & W. Admiraal (2017). Decomposition of aquatic pioneer vegetation in newly constructed wetlands. Ecological Engineering,

  • Rico, A., Zhao, W., Gillissen, F., Lürling, M. & P.J. van den Brink (2018) Effects of temperature, genetic variation and species competition on the sensitivity of algae populations to the antibiotic enrofloxacin. Ecotoxicology and Environmental Safety 148:228-236

  • Robroek, B.J.M., Jassey, V.E.J., Payne, R.J., Martí, M., Bragazza, L., Bleeker, A., Buttler, A., Caporn, S.J.M., Dise, N.B., Kattge, J., Zając, K., Svensson, B.H., van Ruijven J. & J.T.A. Verhoeven (2017) Taxonomic and functional turnover are decoupled in European peat bogs. Nature Communications 8: 1161

  • Spears, B. M., Futter, M.N., Jeppesen, E., Huser, B.J. , Ives, S., Davidson, T.A., Adrian, R, Angeler, D.G., et al. & S.J. Thackeray (2017) Ecological resilience in lakes and the conjunction fallacy. Nature Ecology & Evolution 1: 1616–1624

  • Van Leeuwen, C.H.A., Lovas-Kiss, Á., Ovegård, M., & A.J. Green (2017) Great cormorants reveal overlooked secondary dispersal of plants and invertebrates by piscivorous waterbirds. Biology Letters 13: 20170406

  • Verhoeven, J.T.A., Beltman, B. Janssen,, R. & M.B. Soons (2017) Delineating landscape-scale processes of hydrology and plant dispersal for species-rich fen conservation: the Operational Landscape Unit approach Wetlands Ecology and Management 25 (6): 761-774