Effects of elevated temperature and CO2 on the composition of phytoplankton and zooplankton communities

Internship/MSc research project

The worldwide rise of atmospheric carbon dioxide (CO2) causes global warming. This so-called greenhouse effect causes species extinctions and alterations in structure and functioning of ecosystems. Apart from temperature effects, elevated CO2 may also have direct effects on ecosystems. Lakes are particularly sensitive for elevated CO2, because they receive additional carbon from the surrounding watershed –in addition to direct atmospheric exchange. The latter is caused by CO2-enhanced terrestrial plant growth, leading to more input of dissolved organic carbon (DOC) and (after senescence) particulate organic carbon (POC), which eventually end up in lakes and is degraded to DOC and finally CO2 (Fig. 1). The The effects of this large carbon influx depend on the balance between carbon and nutrients, which forms the basis of the so-called ‘ecological stoichiometry’ (Sterner & Elser, 2002), and as such being the central point of view of this project.

Sterner, R.W., J.J. Elser, 2002. Ecological stoichiometry: the biology of elements from molecules to biosphere. Princeton University Press, Princeton,New Jersey.

Figure 1: Atmospheric carbon enters a lake via two pathways: 1. through direct exchange at the lake surface; and 2. via vegetation in the surrounding watershed; plant-sequestered carbon is released as particulate organic carbon (POC) and dissolved organic carbon (DOC) and ultimately being degraded to CO2

Lakes in The Netherlands are on the way back from eutrophication; therefore it is expected that nutrien concentrations will remain equal or go down in the near future, causing a relative surplus of carbon. This may affect the competitive balance between different phytoplankton species, which has immediate consequences for water quality. Furthermore, these algae contain less nutrients per unit biomass, resulting in a lower food quality for herbivores such as cladocera (water fleas). Because zooplankton in turn is consumed by larger predators such as insects and fish, altered algal food quality may affect the entire food web. You will find more information in the article : Effects of climate change on lake functioning.

Approach
This internship/MSc research project investigates the possible effects of elevated temperature and CO2 on the composition of fytoplankton and zooplankton communities. This research project investigates how the altered stoichiometric composition of the phytoplankton affects the zooplankton.The latter will initially be investigates using one phytoplankton species, the green algae Scenedesmus obliquus (Figure 2), and one zooplankton species, the rotifer Brachionus calyciflorus (Figure 3).

Figure 2. The green algae Scenedesmus 

Figure 3. The rotifer Brachionus

In due time, more phytoplankton and zooplankton species will be investigated, such as copepods and cladocera (Fig. 4).

Figure 4. Different zooplankton species

By culturing the algae at different temperatures and CO2 concentrations, the composition may change (Fig. 5, 6). These algae will be fed to zooplankton in flow-through vessels (Fig. 7), where the zooplankton species can be studied separately and in competition. Furthermore, the population dynamics of algae and zooplankton together will be investigated in these vessels.

Figure 5. Experiment that investigates the effects of elevated temperature and CO2 on phytoplankton chemical composition

Figure 6. Experiment on chemical composition phytoplankton (continuous culture)

Figure 7. Test of a prototype flow-through vessel

Duration
Internships or MSc research projects will be set up jointly, and may last from 2-3 months up to 1 year. The research is being carried out at the NIOO-Centre voor Limnology. Practical supervision at the NIOO-CL will be done by Nico Helmsing, scientific supervision will be done by Anthony Verschoor and Ellen van Donk.

Contactperson
Questions can be addressed to Anthony Verschoor: 0294 239356/06 43577216, a.verschoor@nioo.knaw.nl, http://www.nioo.knaw.nl/ppages/averschoor

This research is part of the project “Effects of increased pCO2 on freshwater pelagic ecosystems through hydrodynamical-chemical coupling: a stoichiometric perspective.”, financed by the Water programme of the NWO (Netherlands Organisation for Scientific Research), P.I.’s Ellen van Donk (NIOO-CL) and Jef Huisman (University of Amsterdam, Institute for Biodiversity and Ecosystem Dynamics [UvA-IBED]).
 

[figuren 4, 6 en 7 invoegen, opgevraagd per mail a. verschoor]