Ellen Van Donk

• Prof. dr.
• Head of Department at Netherlands Institute of Ecology

Methane (CH4) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. He...

Eukaryotic phytoplankton form the basis of aquatic food webs and play a key role in the global carbon cycle. Many of these evolutionarily diverse microalgae are also capable of feeding on other microbes, and hence simultaneously act both as primary producers and consumers. The net ecosystem impact of such mixotrophs depends on their nutritional str...

Chytridiomycota, often referred to as chytrids, can be virulent parasites with the potential to inflict mass mortalities on hosts, causing e.g. changes in phytoplankton size distributions and succession, and the delay or suppression of bloom events. Molecular environmental surveys have revealed an unexpectedly large diversity of chytrids across a w...

Human activities have dramatically altered nutrient fluxes from the landscape into receiving waters. As a result, not only the concentration of nutrients in surface waters has increased, but also their elemental ratios have changed. Such shifts in resource supply ratios will alter autotroph stoichiometry, which may in turn have consequences for hig...

Ecological stoichiometry has proven to be invaluable for understanding consumer response to changes in resource quality. Although interactions between trophic levels occur at the community level, most studies focus on single consumer species. In contrast to individual species, communities may deal with trophic mismatch not only through elemental pl...

Human activity is currently changing our environment rapidly, with predicted temperature increases of 1–5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat,...

After restoration, eutrophicated shallow freshwaters may show mass development of only one or two submerged macrophyte species, lowering biodiversity and hampering recreation. It is unclear which environmental factors govern this high percentage of the volume inhabited (PVI²) by submerged macrophytes, and whether the development of a more diverse,...

Secondary compounds can contribute to the success of non-native plant species if they reduce damage by native herbivores or inhibit the growth of native plant competitors. However, there is opposing evidence on whether the secondary compounds of non-native plant species are stronger than those of natives. This may be explained by other factors, bes...

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its...

Non‐native plants increasingly dominate the vegetation in aquatic ecosystems and thrive in eutrophic conditions. In eutrophic conditions, submerged plants risk being overgrown by epiphytic algae; however, if non‐native plants are less susceptible to periphyton than natives, this would contribute to their dominance. Non‐native plants may differ from...

Global warming has been shown to affect ecosystems worldwide. Warming may, for instance,disrupt plant herbivore synchrony and bird phenology in terrestrial systems, reduce primary production inoceans, and promote toxic cyanobacterial blooms in freshwater lakes. Responses of communities will notonly depend on direct species-specific temperature effe...

Significance Early-warning indicators (EWIs), statistical metrics of system resilience, have been hypothesized to provide advance warning of sudden shifts in ecosystems, or so-called “regime shifts.” Here we tested this hypothesis for four commonly used EWIs. We used empirical time series from five freshwater ecosystems with documented sudden, pers...

Numerous studies show that increasing species richness leads to higher ecosystem productivity. This effect is often attributed to more efficient portioning of multiple resources in communities with higher numbers of competing species, indicating the role of resource supply and stoichiometry for biodiversity-ecosystem functioning relationships. Here...

Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton populations will cause a transfer of carbon and nutrients into parasites, which may change the type of food available for h...

Internal phosphorus loading has become a major problem in many shallow freshwater lakes over the past decades due to the build-up of phosphorus stocks in the sediment. Iron is a natural capping agent which can enhance sediment P binding capacity, thus reducing P availability and shifting a lake from an algal to a macrophyte dominated state. Iron co...

Over the last decades, anthropogenic activities have discharged into the environment many manmade chemicals. There is a rising concern regarding pharmaceutical products and their spread into the environment (e.g. Kümmerer 2008). Due to the enormous quantities consumed, anti-inflammatories, antibiotics, anti-depressives, hormones and blood lipid reg...

The structure of aquatic ecosystems is determined by complex interactions among individual organisms at different trophic levels. Although our basic understanding of how top-down and bottom-up processes interact to determine food-web dynamics has advanced, we still lack insights into how complex interactions and feedbacks affect the dynamics and st...

2014. Coupled human and natural system dynamics as key to the sustainability of Lake Victoria's ecosystem services. Ecology and Society 19(4):

The elemental composition of phytoplankton is highly variable compared to the relatively narrow stoichiometry of zooplankton grazers. Using a full factorial design, we tested the effects of alterations in algal elemental composition (i.e., food quality) combined with food quantity on the life history of a Daphnia galeata clone from Lake IJsselmeer....

Harmful algal blooms threaten the water quality of many eutrophic and hypertrophic lakes and cause severe ecological and economic damage worldwide. Dense blooms often deplete the dissolved CO2 concentration and raise pH. Yet, quantitative prediction of the feedbacks between phytoplankton growth, CO2 drawdown and the inorganic carbon chemistry of aq...

Intraguild predators both feed on and compete with their intraguild prey. In theory, intraguild predators can therefore be very effective as biological control agents of intraguild prey species, especially in productive environments. We investigated this hypothesis using the mixotrophic chrysophyte Ochromonas as intraguild predator and the harmful...

The current changes in our climate will likely have far-reaching consequences for aquatic ecosystems. These changes in the climate, however, do not act alone, and are often accompanied by additional stressors such as eutrophication. Both global warming and eutrophication have been shown to affect the timing and magnitude of phytoplankton blooms. Li...

Eutrophication of shallow lakes in North-West Europe has resulted in cyanobacterial blooms, turbid water, and a decline in submerged macrophytes. Even though external inputs of phosphorus (P) are declining, internal loading of P from the sediment may delay the recovery of these aquatic ecosystems. Iron can be a useful chemical binding agent to comb...

Theory predicts that intraguild predation leads to different community dynamics than the trophic cascades of a linear food chain. However, experimental comparisons of these two food-web modules are rare. Mixotrophic plankton species combine photoautotrophic and heterotrophic nutrition by grazing upon other phytoplankton species. We found that the m...

Diatom-based assays have been successfully associated worldwide with the trophic status of lakes. Several studies have demonstrated a correlation between epiphytic diatoms and nutrient load in shallow lakes and wetlands. We examine the relative importance of environmental factors in explaining the structure of epiphytic diatom communities in a set...

We investigated how dynamics in phytoplankton biomass are driven through light and nutrient limitations in the M wanza G ulf, L ake V ictoria ( T anzania). We measured light attenuation, chlorophyll a and water quality parameters along a phytoplankton biomass gradient in the M wanza G ulf at six sampling stations in three different seasons from A u...

In our recent contribution to the special issue on plankton dynamics in a fast‐changing world, we outlined some general predictions of plankton dynamics in different climate regions now and in future, building on the P lankton E cology G roup (PEG) model (de Senerpont Domis et al ., 2013). We proposed a stylised version of plankton dynamics in Fig....

The cost of parasitism often depends on environmental conditions and host identity. Therefore, variation in the biotic and abiotic environment can have repercussions on both, species-level host-parasite interaction patterns but also on host genotype-specific susceptibility to disease. We exposed seven genetically different but concurrent strains of...

Fingerprinting of Asterionellaformosa isolates. Description of the AFLP fingerprinting and the statistical analysis methods used for the assessment of genetic diversity in the experimental Asterionellaformosa genotypes. (DOCX)

ANOVA models testing co-linearity between predictors host genotype and host cell-size. To assess whether genotype or host cell-size is the more appropriate predictor for host and parasite productivity, two ANOVA models were compared including either temperature and host genotype (model 1, tables S2.1 and S2.4) or temperature and host cell-size (mod...

Report: CHO/TNO, 22

Eutrophication has caused a decline of charophyte species in many shallow lakes in Europe. Even though external inputs of phosphorus are declining, internal loading of P from the sediment seems to delay the recovery of these systems. Iron is a useful chemical binding agent to combat internal phosphorus loading. However, the effects of iron addition...

Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottle...

Background In lakes that have become eutrophic due to sewage discharges or nutrient runoff from land, problems such as algal blooms and oxygen deficiency often persist even when nutrient supplies have been reduced. One reason is that phosphorus stored in the sediments can exchange with the water. There are indications that the high abundance of phy...

Contrary to expectation, populations of clonal organisms are often genetically highly diverse. In phytoplankton, this diversity is maintained throughout periods of high population growth (that is, blooms), even though competitive exclusion among genotypes should hypothetically lead to the dominance of a few superior genotypes. Genotype-specific par...

1. Many host–parasite interaction dynamics show distinct seasonality. Parasite population growth and invasion success are generally explained by host density dependence, while the direct influence of environmental factors on parasite life history traits has been underreported. 2. In waterbodies, resource availability and environmental conditions ch...

1. Different components of the climate system have been shown to affect temporal dynamics in natural plankton communities on scales varying from days to years. The seasonal dynamics in temperate lake plankton communities, with emphasis on both physical and biological forcing factors, were captured in the 1980s in a conceptual framework, the Plankto...

1. Rising atmospheric CO2 concentrations might affect the primary production and community composition of freshwater ecosystems. 2. We investigated these potential effects in laboratory mesocosms (Limnotrons), using monoculture experiments and competition experiments with the green alga Scenedesmus obliquus and the cyanobacterium Synechocystis sp....

1. Despite the strong impact parasites can have, only few models of phytoplankton ecology or aquatic food webs have specifically included parasitism. 2. Here, we provide a susceptible-infected model for a diatom-chytrid host–parasite system that explicitly includes nutrients, infected and uninfected hosts, reproduction of the parasite on the hosts...

The metabolic theory of ecology predicts that temperature affects heterotrophic processes more strongly than autotrophic processes. We hypothesized that this differential temperature response may shift mixotrophic organisms towards more heterotrophic nutrition with rising temperature. The hypothesis was tested in experiments with the mixotrophic ch...

The food webs of terrestrial soils and of freshwater and marine sediments depend on adjacent aboveground or pelagic ecosystems for organic matter input that provides nutrients and energy. There are important similarities in the flow of organic matter through these food webs and how this flow feeds back to primary production. In both soils and sedim...

Eutrophication has caused a decline of charophyte species in many shallow lakes in Europe. Even though external inputs of phosphorus are declining, internal loading of P from the sediment seems to delay the recovery of these systems. Iron is a useful chemical binding agent to combat internal phosphorus loading. However, the effects of iron addition...

Eutrophication has caused a decline of charophyte species in many shallow lakes in Europe. Even though external inputs of phosphorus are declining, internal loading of P from the sediment seems to delay the recovery of these systems. Iron is a useful chemical binding agent to combat internal phosphorus loading. However, the effects of iron addition...

Until 1992, zebra mussels (Dreissena polymorpha) were an important food source for diving ducks in Lake Markermeer (The Netherlands). After 1993, the mussel biomass sharply declined, and the currentpopulation is in poor condition (maximum shell length <15 mm) compared to populations from adjacent Lake IJsselmeer. Lake Markermeer is characterized by...

The seasonal succession of plankton is an annually repeated process of com-munity assembly during which all major external factors and internal inter-actions shaping communities can be studied. A quarter of a century ago, the state of this understanding was described by the verbal plankton ecology group (PEG) model. It emphasized the role of physic...

Marine and freshwater phytoplankton populations often show large clonal diversity, which is in disagreement with clonal selection of the most vigorous genotype(s). Temporal fluctuation in selection pressures in variable environments is a leading explanation for maintenance of such genetic diversity. To test the influence of temperature as a selecti...

The dynamic interactions among nutrients, algae and grazers were tested in a 2 × 3 factorial microcosm experiment that manipulated grazers (Daphnia present or absent) and algal composition (single species cultures and mixtures of an undefended and a digestion-resistant green alga). The experiment was run for 25 days in 10-L carboys under mesotrophi...

Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottle...

IntroductionDisturbance Factors Affecting LakesLake Restoration MeasuresPerspectivesAcknowledgements

Background/Question/Methods: The impact of climate change on biological systems is already apparent through changes in the phenology and the distribution of individual species. However, other stressors of ecosystem functioning, such as habitat fragmentation, eutrophication and pollution may act in concert with climate change. Possible non-additiv...

Macrophytes and nutrient loading are two factors that can strongly determine the diversity and composition of aquatic invertebrate communities. Both factors may also interact, because macrophyte species may be differentially affected by nutrients. Macrophyte community characteristics, such as species composition, morphotype and biomass have the pot...

Dominance by cyanobacteria hampers human use of lakes and reservoirs worldwide. Previous studies indicate that excessive nutrient loading and warmer conditions promote dominance by cyanobacteria, but evidence from global scale field data has so far been scarce. Our analysis, based on a study of 143 lakes along a latitudinal transect ranging from su...

Many organisms have developed defences to avoid predation by species at higher trophic levels. The capability of primary producers to defend themselves against herbivores affects their own survival, can modulate the strength of trophic cascades and changes rates of competitive exclusion in aquatic communities. Algal species are highly flexible in t...

Climate change scenarios predict a doubling of the atmospheric CO(2) concentration by the end of this century. Yet, how rising CO(2) will affect the species composition of aquatic microbial communities is still largely an open question. In this study, we develop a resource competition model to investigate competition for dissolved inorganic carbon...

1. We describe the dynamics of host–parasite interactions over a period of more than 30 years between the freshwater diatom Asterionella formosa and two highly virulent chytrid parasites (Rhizophydium planktonicum and Zygorhizidium planktonicum) in Lake Maarsseveen, The Netherlands. This period is characterised by a significant warming trend which...

Diatoms form large spring blooms in lakes and oceans, providing fuel for higher trophic levels at the start of the growing season. Some of the diatom blooms, however, are not grazed by filter-feeding zooplankton like Daphnia due to their large size. Several of these large diatoms are susceptible to chytrid infections. Zoospores of chytrids appeared...

Many organisms have developed defences to avoid predation by species at higher trophic levels. The capability of primary producers to defend themselves against herbivores affects their own survival , can modulate the strength of trophic cascades and changes rates of competitive exclusion in aquatic communities. Algal species are highly flexible in...

Planktothrix agardhii is a widespread harmful cyanobacterium of eutrophic waters, and can produce the hepatotoxins [Asp(3)]microcystin-LR and [Asp(3)]microcystin-RR. These two microcystin variants differ in their first variable amino acid position, which is occupied by either leucine (L) or arginine (R). Although microcystins are extensively invest...

Earth's climate is changing, and by the end of the 21st century in Europe, average temperatures are likely to have risen by at least 2 °C, and more likely 4 °C with associated effects on patterns of precipitation and the frequency of extreme weather events. Attention among policy-makers is divided about how to minimise the change, how to mitigate i...

Many short-lived or univoltine organisms at high latitudes and altitudes face the challenge to complete their life-cycle within a brief growing season. This means that they need to maintain a high growth rate at low temperatures, and one way of doing this is to allocate limiting resources like phosphorus to RNA in order to maximize protein synthesi...

Submerged freshwater macrophytes decline with increasing eutrophication. This has consequences for ecosystem processes in shallow lakes and ponds as macrophytes can reduce algal blooms under eutrophic conditions. We hypothesize that the productivity of submerged vegetation, biomass change under eutrophication and the suppression of algal blooms may...

Bioassays with the toxic cyanobacterium Microcystis aeruginosa PCC 7806, its non-toxic mutant Delta mcyB, and Daphnia magna as grazer were used to evaluate biotic factors in induced defence, in particular cyanobacterial and grazer-released info-chemicals. Three main questions were addressed in this study: Does Daphnia grazing lead to a loss of cyan...

While most experiments investigating zooplankton grazing on harmful cyanobacteria have been carried out with metazoan plankton, several protozoa can also feed efficiently on cyanobacteria. We investigated grazing by the mixotrophic flagellate Ochromonas sp. on the toxic cyanobacterium Microcystis aeruginosa. Ochromonas sp. grew rapidly on M. aerugi...

The combined influence of a pesticide (carbaryl) and a cyanotoxin (microcystin LR) on the life history of Daphnia pulicaria was investigated. At the beginning of the experiments animals were pulse exposed to carbaryl for 24h and microcystins were delivered bound in Microcystis’ cells at different, sub-lethal concentrations (chronic exposure). In or...

Advances in ecological stoichiometry, a rapidly expanding research field investigating the elemental composition of organisms and their environment, have shed new light on the impacts of climate change on freshwater and marine ecosystems. Current changes in the Earth’s climate alter the availability of carbon and nutrients in lakes and oceans. In p...

Fine organic suspended sediments (refractory detritus) play an important role in the underwater light attenuation of large shallow lakes with a peat origin and a eutrophication history. Wind driven resuspension of this material, its flocculation in the water column and the settlement of the formed flocs are the main processes governing the dynamics...

Advances in ecological stoichiometry, a rapidly expanding research field investigating the elemental composition of organisms and their environment, have shed new light on the impacts of climate change on freshwater and marine ecosystems. Current changes in the Earth's climate alter the availability of carbon and nutrients in lakes and oceans. In p...

While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biologic...

The effects of inducible defenses and constitutive defenses on population dynamics were investigated in a freshwater plankton system with rotifers as predators and different algal strains as prey. We made predictions for these systems using a chemostat predator–prey model and focused on population stability and predator persistence as a function of...

1. In order to test the effect of Ochromonas sp., a mixotrophic chrysophyte, on cyanobacteria, grazing experiments were performed under controlled conditions. We studied grazing on three Microcystis aeruginosa strains, varying in toxicity and morphology, as well as on one filamentous cyanobacterium, Pseudanabaena sp. Furthermore, we analysed the co...

Ecology Letters (2009) 12: 1326–1335 The elemental composition of primary producers reflects the availability of light, carbon and nutrients in their environment. According to the carbon-nutrient balance hypothesis, this has implications for the production of secondary metabolites. To test this hypothesis, we investigated a family of toxins, known...

The freshwater chlorophyte Scenedesmus obliquus (Turpin) Kützing produces colonies as an inducible defence against herbivores. We investigated the dynamics of Scenedesmus colony formation and disintegration in response to the density of the herbivorous rotifer Brachionus calyciflorus in large-scale mesocosms. Additional bioassays were performed to...