In this experiment, 7 naturally co-occurring Asterionella formosa genotypes from Maarsseveen (freshwater lake, NL) were exposed to a temperature gradient ranging from 1°C to 21°C and to a single genotype of the obligate fungal parasite (the chytrid Zyghorizidium planktonicum) in a fully crossed experimental design. Each host genotype by temperature by infection exposure treatment was replicated 5 times and controlled (no parasite exposure) once, resulting in 35 treatment combinations and 210 experimental units.

The aim was to assess whether genotypes responded differently to infection and whether the ranking order for susceptibility to disease varied with temperature treatments in a way that could explain maintenance of genotype diversity in natural waters due to fluctuating selection pressure.

Measured variables were host cells/mL and parasite sporangia mL-1 for each sampling day (used to calculate yield over time)