Newsletter 16 | 18 June 2018

Newsletter 16, 18 June 2018

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 November 2018).

Newsletter contents

Upcoming events in the Netherlands

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  • The 'Week of the invasive exotic species' started on the 15th of June, with many different events throughout The Netherlands. 15 - 24 June 2018 More information.

  • Symposium 'Water talk: Reducing urban water risks in a changing climate' 21 June 2018, Brussels More information.

  • Symposium "Scaling up Building with Nature", linking ecology with hydraulic engineering. Utrecht, 27 June 2018 More information.

  • 'Big Jump 2018', a European-wide day to call attention for clean surface waters for swimming. 8 Juli 2018, Aalst More information.

  • Symposium 'Water in smart cities: leefbaarheid door groenblauwe daken' 19 September 2018, Nijmegen More information.

CWE Symposium

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Towards renewable energy: opportunities and consequences for freshwater and marine ecosystems
29 June 2018, Deltares, Delft

Renewable energy sources such as solar panels, geothermal energy and wind turbines are increasingly replacing fossil fuels. Freshwater and marine ecosystems provide many opportunities for generating renewable energy, however, this may come with ecological consequences. This CWE symposium brings together research on both the opportunities and consequences of the current energy transition for freshwater and marine ecosystems.

Registration (free) and more information is available on the CWE website.

The succeeding CWE symposium will be in winter 2018
23 November 2018, Antwerp, Belgium
Theme: 'Physics of wetlands'

International conferences

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  • 17th International Symposium on Microbial Ecology (ISME17), 12 - 17 August 2018, Leipzig, Germany. More information.

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

  • Annual meeting of the Ecological Society of America (ESA), 5 - 10 August 2018, New Orleans, USA More information.

  • 16th International Conference of the IWA Specialist Group on Wetland Systems for Water Pollution Control 30 September - 4 October 2018, Valencia, Spain More information.

  • 11th INTECOL International Wetlands Conference, September 2020, Christchurch, New Zealand. More information.


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  • STOWA launched a first description of the "Ecologische Systeemtoestanden" (EST’s) for lentic waters. These EST's are important instruments for gaining insight into the ecological conditions of water bodies and taking cost-effective management decisions for improvement. More information.

  • From 8-10th of June thousands of people joined the first nationwide 'citizen science' ditch survey in The Netherlands. During the Dutch Ditch Days, they counted aquatic invertebrates and performed simple water quality tests at more than 120 locations. The most counted water animals were the backswimmer (Notonectidae), followed by the amphipods and pond snails. Based on the results of the aquatic invertebrate counts, the average Dutch ditch would score 6.3 out of 10 in terms of water quality. The Dutch Ditch Days were organized by NIOO-KNAW. More information.

  • A new 'Peilbesluit voor het IJsselmeergebied' has been signed last week by the minister, which starts a fluctuating water regime management in the IJsselmeer and Markermeer during summer. For the last 100 years the water levels in the IJsselmeer and Markermeer have been stabilized at 20 cm below NAP throughout the whole summer period, and at 40 cm below NAP during the winter. As of next year, the water level in summer will be allowed to fluctuate between 10 cm in spring and lowered by 10 cm in the autumn. More information.
  • Every year the Unions of the Waterboards and the 'Nederlandse Waterschapsbank' hand out a price for water innovation ('Waterinnovatieprijs'). Categories for the contest are always ‘Watersafety’, ‘Clean water’ en ‘Sufficient water’. This year, a fourth category is added: ‘Circular economy’. How do we stop the large amounts of garbage in our water, and how do we create a circular economy? Innovative projects can be handed in until 28 August 2018. More information.

Guest column: Aquatic plants and water quality

Jan Roelofs (Radboud University Nijmegen), Gerben van Geest (Deltares) & Hilde Tomassen (B-ware)
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"Currently, at the Radboud University of Nijmegen a large field study is carried out that relates the occurrence of aquatic plants to environmental conditions of surface water and sediments in The Netherlands. This research is a repetition of a survey that was carried out during 1978 – 1982. In this column, the main conclusions of the study during 1978 – 1982 are presented, and compared to recent findings."

Results of survey 1978 - 1982
Between 1978 -1982 in The Netherlands, a large field study was carried out to relate the occurrence of aquatic plant species to environmental conditions of the surface water and sediments. In these years, a total of 600 water bodies were examined twice a year, once in the summer half-year and once in the winter half-year. In total, about 56 water and sediment characteristics were measured and related to the composition of aquatic vegetation at these sites. The results of that research were published between 1983 and 1985. Based on these publications, a book on aquatic plants and water quality was published by the KNNV in 1986.

The research yielded many new discoveries. For example, it turned out that about 80 percent of the original weakly buffered heathland pools on pleistocene sandy soils were strongly acidified due to atmospheric deposition. In fact, this study resulted in the discovery of water acidification in The Netherlands. This was caused by high atmospheric deposition of mainly sulphur. Before 1900, chloride was the dominant anion in heathland pools and around 1980 this had shifted to sulphate. The most prominent species of weakly buffered waters such as Littorella uniflora, Lobelia dortmanna, Isoetes echinospora, Pilularia globulifera, Scirpus fluitans and many others showed a strong decline and were seriously threatened. At that time, species such as Isoetes echinospora had become completely extinct in The Netherlands, while Lobelia dortmanna was present at only one location. By contrast, Juncus bulbosus had become the dominant species in strongly acidified waters. Ecophysiological experiments with tubers showed that the strong increase of this species was due to low pH of surface waters in combination with high ammonium levels. The concentrations of ammonium were indeed very high in acidified waters and experiments with artificial rain water showed that the high ammonium levels originated from atmospheric deposition. This can be seen as the discovery of the ammonia problem in The Netherlands, because until then – even internationally – it was completely unknown that intensive livestock farming resulted in high ammonia emissions into the environment.

Left: Lobelia dortmanna - Dortmann's cardinalflower - Waterlobelia / Right: Potamogeton nodus - Longleaf pondweed - Rivierfonteinkruid

In these years, the water quality was also poor in large, national waters such as the river Rhine and Meuse, and also in streams and lakes that were fed by these rivers. As a results, aquatic plants were nearly absent in large rivers and lakes, such as Veluwemeer. This was strongly in contrast with the situation of the 50s of the last century. At that time, the water was still clear in fens like the Wieden and Weerribben, and well developed aquatic vegetation occurred with Stratiotes aloides and many Potamogeton-species. During the field study during 1978 – 1982 however, Stratiotes aloides was almost absent in the Weerribben, and the water was highly turbid.

Similarly, conditions had also worsened for species characteristic of brackish waters along the coast. This was mainly the results of the completion of the Delta works (which resulted in the reduction of the input of brackish water) in combination with eutrophication caused by agricultural land use. As a result, species such as Ruppia maritima and Ruppia cirrhosa disappeared almost entirely from The Netherlands. In the agricultural area, environmental conditions varied from one area to the other. At that time, streams and ditches with excellent water quality and species rich communities were still present on a local scale, especially at locations with strong seepage of ground water from pleistocene areas.

Comparison with recent situation
Currently, in many areas in The Netherlands the environmental conditions differ strongly from 40 years ago. In many nature reserves, the water quality has improved spectacularly. This is the result of a strongly reduction of atmospheric sulphur deposition and a 50% reduction of the nitrogen deposition. Additionally, in many heathland pools the sulphur-rich sediments have been removed. Accordingly, none of the pools sampled in recent years showed indications for acidification, while hundreds of (previously acidified) pools have now strongly improved conditions. This has resulted in the spontaneous turn of the previously (almost) extinct species such as Isoetes echinospora and Lobelia dortmanna at about ten sites, while in many other locations soft-water species such as Pilularia globulifera, Littorella uniflora, Scirpus fluitans, Hypericum elodes, Luronium natans, Baldellia repens and many others have become regularly occurring species again.

The condition for macrophyte growth is also significantly better in the river Rhine, and – to a lesser extent – in the river Meuse. As a result, the water quality has also improved considerably in lakes that are fed by river water. In 1980, hardly any aquatic plants grew in the river Rhine and Meuse, as well as in large lakes. Nowadays, extensive vegetations of aquatic plants occur in these water bodies, which characteristic species such as Potamogeton nodosus, Potamogeton perfoliatus, Najas marina and many others. Many lakes are also largely colonized by water plants, including various species of Charophytes.

In many peat areas, we also see positive developments in water quality. Water clarity in ditches and lakes in the Wieden and Weerribben has become very high again. Stratiotes aloides is just as common as in the fifties of the last century, and nowadays up to seven species of Potamogeton can be found close together. This improvement in water quality can be partly attributed to the improvement of the Rhine and the IJssel, but also to an adapted hydrology which resulted in a strong reduction of the input of agricultural water. Additionally, water levels are allowed to fluctuate again, which has also resulted in a reduced input of eutrophied alkaline water.

Stratiotes aloides - Water soldier - Krabbescheer

For brackish inland water, conditions have improved too. In Zeeland, Noord Holland and the Wadden Sea, new shallow pools were created that are fed with brackish seepage water. Additionally, well tubes have been constructed that increase the input of seepage water and eutrophied sediments have been removed. These measured have resulted in the return of characteristic species for brackish conditions, such as Ruppia maritima, Ruppia cirrhosa and Zannichellia palustris ssp. pedunculata.

By contrast, the water quality in ditches in agricultural areas has declined strongly compared to 40 years ago. Currently, many locations are strongly eutrophied, resulting in a dominance of duck weed (Lemna ssp.) and filamentous macro-algae. The deteriorated water quality is mainly the result of the strong intensification of agricultural land use. Many ditches that were previously fed with seepage water have disappeared, because they have been filled up with soil and converted to grassland. Additionally, the grassland is heavily fertilized by manure, which is injected into the ground. Because many areas are currently drained by tubes, this has resulted in a deteriorated water quality of ditches that are fed by these drains. Fortunately, there are still a number of farmers who opt for cows in the pasture and the maintenance of (seepage) ditches, which means that most types of characteristic species for ditches with good water-quality can still be maintained in the Netherlands. Nevertheless, the occurrence of these species in agricultural areas has decreased strongly over the past decades.

Overall, it can be concluded that the water quality has improved significantly in national waters (large rivers and lakes) as well as in nature reserves. Also along the coast, conditions for brackish vegetations (such as Ruppia species) have improved strongly. This contrasts strongly with conditions in agricultural areas, where intensive farming has resulted in a strong deteriorated water quality (and associated aquatic plant communities) over the past 40 years.

PhD graduations

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  • Thijs Frenken (NIOO-KNAW) 18 April 2018 10:30 "Live and let die: How climate change affects bottom-up and top-down factors regulating phytoplankton disease".
  • Mohammad Ravanbakhsh (UU) 3 May 2018 12:45: "Manipulation of plant ethylene balance by soil microbiota: a holobiont perspective to stress tolerance"
  • Thomas Lameris (UvA/NIOO-KNAW) 18 May 2018 14:00 "Outflying climate change: Optimal timing of migratory geese breeding in a warming Arctic."
  • Amber Heijboer (UU) 6 June 2018 16:00. "Disentangling microbial decomposition networks"
  • Peiyu Zhang (NIOO-KNAW) 28 September 2018 14:30. "Trophic interactions in warming waters: Aquatic plant-consumer interactions under climate change".


Recent key publications

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  • Baattrup-Pedersen A, Garssen AG, Göthe E, Hoffmann CC, Oddershede A, Riis T, Van Bodegom PM, Larsen SE & Soons MB (2018) Structural and functional responses of plant communities to climate change-mediated alterations in the hydrology of riparian areas in temperate Europe. Ecology and Evolution

  • dos Reis Oliveira, PC, Kraak, MHS, van der Geest, HG Naranjo, S and PFM Verdonschot (2018) Sediment composition mediated land use effects on lowland streams ecosystems. Science of the Total Environment 631, 459-468

  • Frenken, T, Wierenga, JHW van Donk, E, Declerck, SAJ, de Senerpont Domis, L, Rohrlack, T, and DB Van de Waal (2018) Fungal parasites of a toxic inedible cyanobacterium provide food to zooplankton Limnology and Oceanography in press

  • Grutters, B, Saccomanno, B, Gross, EM, Van de Waal, DB, van Donk, E, and ES Bakker (2017) Growth strategy, phylogeny and stoichiometry determine the allelopathic potential of native and non‐native plants. Oikos 126 (12), 1770-1779

  • Hilt, S, Nuñez, A, Marta, M, Bakker, ES, Blindow, I, Davidson, TA Gillefalk, M et al. (2018) Response of submerged macrophyte communities to external and internal restoration measures in north temperate shallow lakes. Frontiers in Plant Science 9:194

  • Kleyheeg E, Claessens M & MB Soons (2018) Interactions between seed traits and digestive processes determine the germinability of bird-dispersed seeds. PLoS ONE 13: e0195026.

  • Pärn, J. Verhoeven, JTA, Butterbach-Bahl, K, Dise, NB et al. (2018) Nitrogen-rich organic soils under warm well-drained conditions are global nitrous oxide emission hotspots. Nature Communications

  • Petruzzella, A, Manschot, J, van Leeuwen, CHA, Grutters, B and ES Bakker (2018) Mechanisms of invasion resistance of aquatic plant communities. Frontiers in Plant Science 9: 134

  • Ravanbakhsh, M., Sasidharan, R., Voesenek, L.A.C.J., Kowalchuk, G.A. & Jousset, A.L.C. 2018 Microbial modulation of plant ethylene signaling - ecological and evolutionary consequences. Microbiome, 6.

  • Treep HJ, De Jager M, Kuiper LS, Duman T, Katul GG & MB Soons (2018) Costs and benefits of non-random seed release for long-distance dispersal in wind-dispersed plant species. Oikos

  • Van Leeuwen, C.H.A. (2018) Internal and external dispersal of plants by animals: an aquatic perspective on alien interference. Frontiers in Plant Sciences 9:153.

  • Westveer, JJ, van der Geest, HG, van Loon, EE and PFM Verdonschot (2018) Connectivity and seasonality cause rapid taxonomic and functional trait succession within an invertebrate community after stream restoration. PloS ONE 13 (5), e0197182