Bad or good food, that’s the question!

A study on the effects of stoichiometric constraints on rotifer populations.

Every organism needs carbon (C), nitrogen (N) and phosphorus (P) for its growth and body maintenance. Consequently, the element that is shortest in supply will limit the maximal size of populations. Plants have been shown to be highly variable in their C:N:P ratios. In contrast, animals have much more fixed ratios and will therefore be more sensitive to the C:N:P-ratio in their food. A good understanding of the consequences of elemental limitation in animals can contribute a lot to the understanding of the mechanisms that control natural populations.

Aquatic invertebrates have repeatedly been shown to be very sensitive to phosphorus limitation. P indeed is a very important building block of macromolecules such as DNA, RNA and phospholipids. Recent evidence nevertheless suggests that rotifers may be more prone to nitrogen limitation. The evidence is, however, scant and requires more empirical evidence.

Project outline

We will perform laboratory experiments to evaluate the relative effects of carbon, nitrogen and phosphorus limitation on populations of the rotifer Brachionus calyciflorus. For this, we will first have to set up a series of chemostats feeding rotifer populations with phytoplankton varying in elemental ratios. We will also install and evaluate an electronic monitoring system that allows the automatic assessment of rotifer population densities at short time intervals (i.e. the FlowCam system). Finally, we will investigate the effects of the elemental ratios of the food on the population dynamics, morphology and elemental composition of the experimental rotifer populations. This topic is suitable for both long and short term internships of MBO, HBO and master students.

Duration

3–9 months