Rasmus Lindberg (PhD student)

Many organisms respond to nutrient enrichment by reproducing faster. This makes evolutionary sense and is easy to understand as populations are released from nutrient limitation. Although most enrichments tend to be local and short-lived – devoured by growing populations – some are continuously replenished on a global scale. The enrichment of the atmosphere and oceans and lakes with carbon dioxide (which is food for plants) is a notorious example. Is the strategy for dealing with a short-term enrichment a good strategy for dealing with this long term enrichment?

Evolution experiments performed on microalgae suggest that it is not. A trade-off between reproduction and competitiveness and stress tolerance emerge in algae evolved in a carbon dioxide enriched environment. The explanation seems to be that the greater metabolic activity required for reproducing fast in an enriched environment leads to accumulation of damaging metabolic waste products (ROS). To test this hypothesis, I will manipulate growth rate in strains of the green alga Chlamydomonas reinhardtii that vary in vulnerability to ROS and evolve them in the laboratory. If ROS is the source of the trade-off, the impact size of the trade-off will vary with vulnerability to ROS and with growth rate.