I am a phytoplankton ecologist, currently working as an assistant professor in the department of Freshwater and Marine Ecology. In my research I combine experimental data and/or field data with mathematical models. I am fascinated by phytoplankton because they are responsible for about half of all global carbon fixation and form the base of the aquatic food web. Moreover, they are a hugely diverse group of organisms, both in shape and in traits. My scientific fascination regarding phytoplankton focuses on two global topics:
How do physiology (or traits) influence the ecological distribution of and the ecological interactions between different phytoplankton species.
What role do phytoplankton communities play in ecosystem functioning, in particular in carbon and nutrient cycles?
Rising atmospheric CO2 concentrations will increase dissolved CO2 concentrations, decrease pH and shift carbon speciation in aquatic systems. Phytoplankton need inorganic carbon (dissolved CO2 and often bicarbonate) to photosynthesize and grow. However, major species- and strain-specific differences exist both in carbon uptake strategies and pH tolerance.Therefore, changes in carbon chemistry are expected to impact both the size of phytoplankton blooms and the competitive interactions and species composition within phytoplankton blooms. I am workin on the following questions:
What inorganic carbon uptake strategies exist in freshwater phytoplankton, how do these traits influence competition and how are these traits related to the current distribution of phytoplankton species?
Which carbon uptake strategies will benefit from rising CO2 concentrations, and how will this impact phytoplankton communities?
Rising CO2 concentrations are predicted to change carbon cycling in lakes and intensify phytoplankton blooms. However, the role that phytoplankton blooms play in carbon cycling, carbon burial and the drawdown of atmospheric CO2 in freshwaters is relatively poorly studied. I am trying to answer the following questions:
How do phytoplankton blooms influence organic carbon burial and the atmospheric CO2 flux in different types freshwater systems?
Can the temporal dynamics of phytoplankton population density, organic carbon burial and the atmospheric CO2 flux be captured by a model and can this model be used to make predictions about these processes at increasing atmospheric CO2 concentrations?
Mussels feed on phytoplankton and suspended organic matter by filtering large quantities of water. Recently, the invasion of the quagga mussel (Dreissena rostriformis) in Lake Sloterplas coincided with a sharp reduction in the size of the cyanobacterial summer bloom in this lake. Cyanobacterial blooms are highly undesirable because they are potentially toxic. Together with Waternet (a Dutch water company), we are investigating whether and how the quagga mussel can be used to control the cyanobacterial bloom in the Sloterplas.
I'm an aquatic ecologist with experience in field monitoring, laboratory experiments and modelling. I studied biology at the Vrije Universiteit in Amsterdam. During my studies I focused on nutrient dynamics and biodiversity in soils and sediments. I carried out my PhD research on the population dynamics of a freshwater cyanobacterium at the Universiteit van Amsterdam and the Netherland Institute of Ecology (NIOO). As a postdoctoral researcher at the department of Aquatic Microbiology, I investigated the impact of rising CO2 concentrations on phytoplankton blooms in freshwaters. Currently, I am an Assistant Professor in the Freshwater and Marine Ecology group at IBED.
During my PhD I investigated the population dynamics of
Microcystis in Lake Volkerak-Zoommeer in the southwest
of the Netherlands. Microcystis is a notorious
potentially toxic cyanobacterium that causes problems in
freshwaters all over the world. It contains gas vesicles that
make it lighter than water, so that it can accumulate at the
surface of the water column, forming toxic scums.
Lake Volkerak-Zoommeer used to be an estuarium before the building of a dam turned it into a freshwater lake in 1987. Since the mid-90's, massive blooms of Microcystis dominate the lake during summer.
My research focused on benthic-pelagic coupling in the
population dynamics of Microcystis . Large amounts of
Microcystis overwinter in the sediment and relatively
little was known about the interactions between this benthic
population and the well studied pelagic population in the water
column. I monitored Microcystis populations in the
water column and in the sediments and measured the exchange
between the two populations for a period of two years. In
addition I studied Microcystis growth and mortality in
the lab under different light intensities and temperatures.
Furthermore I studied the aggregation of clay to
Microcystis and the subsequent sinking of buoyant
colonies from the water column.
My measurements show that the benthic populations of Microcystis remain viable throughout the year and my models show that benthic Microcystis contribute substantially to the size of the summer bloom. Also, resuspension of the sediment can affect the two populations in different ways. Resuspension enables recruitment of the benthic population to the water column. However, the increase in suspended sediment particles can also increase sedimentation of the pelagic population to the sediment through the attachment of suspended particles to Microcystis colonies.
This knowledge was then used to predict which lake management strategies could be effective in the battle against Microcystis blooms in Lake Volkerak-Zoommeer: the (re-)introduction of saline water into the lake or flushing with freshwater. My model of the population dynamics of Microcystis indicates that both water management strategies can be effective in reducing blooms in the lake. However, since freshwater availability during summer is generally low, the water managers are currently considering the reintroduction of saline water.
Below you can download a pdf file of my thesis "Benthic pelagic coupling in the population dynamics of the cyanobacterium Microcystis ".
Same of these publications can be downloaded (see below)