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DOI

Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine
environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton
populations will cause a transfer of carbon and nutrients into parasites, which may change the type of food available
for higher trophic levels. Some phytoplankton species are inedible to zooplankton, and the termination of their population
by parasites may liberate otherwise unavailable carbon and nutrients. Phytoplankton spring blooms often consist
of large diatoms inedible for zooplankton, but the zoospores of their fungal parasites may serve as a food source
for this higher trophic level. Here, we investigated the impact of warming on the fungal infection of a natural phytoplankton
spring bloom and followed the response of a zooplankton community. Experiments were performed in ca.
1000 L indoor mesocosms exposed to a controlled seasonal temperature cycle and a warm (+4 °C) treatment in the
period from March to June 2014. The spring bloom was dominated by the diatom Synedra. At the peak of infection
over 40% of the Synedra population was infected by a fungal parasite (i.e. a chytrid) in both treatments. Warming did
not affect the onset of the Synedra bloom, but accelerated its termination. Peak population density of Synedra tended
to be lower in the warm treatments. Furthermore, Synedra carbon: phosphorus stoichiometry increased during the
bloom, particularly in the control treatments. This indicates enhanced phosphorus limitation in the control treatments,
which may have constrained chytrid development. Timing of the rotifer Keratella advanced in the warm
treatments and closely followed chytrid infections. The chytrids’ zoospores may thus have served as an alternative
food source to Keratella. Our study thus emphasizes the importance of incorporating not only nutrient limitation and
grazing, but also parasitism in understanding the response of plankton communities towards global warming.
Original languageEnglish
Pages (from-to)299-309
JournalGlobal Change Biology
Volume22
Issue number1
DOI
Publication statusPublished - 2016

    Research areas

  • national

ID: 1469466