Wednesday October 26, 2022, 4 pm CEST

Corina Brussaard^1*

Phytoplankton virus ecology (with a focus on Phaeocystis)

^1a Department of Freshwater and Marine Ecology (FAME), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94920, 1090
XH, Amsterdam, The Netherlands
² Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB, Den Burg, Texel, The Netherlands
^* Corina.Brussaard@nioz.nl

With more than 70% of the living biomass in the oceans being microbial, marine viruses have plenty of unicellular hosts to choose from. Viruses for all taxonomic phytoplankton groups have been reported but a more detailed comprehension of their impact on population dynamics of the various phytoplankton under natural conditions is still limited. Using methods developed to enumerate aquatic viruses and determine the host specific mortality rates in the field, we show that viral lysis is a highly important loss factor for marine phytoplankton with average rates comparable to the more traditional losses by grazing. We translate our findings to carbon to better understand how viral activity affects the transfer of matter & energy, as well as the biogeochemical cycling. Dependent on their hosts’ metabolism, viral production is influenced by environmental factors affecting host growth and viability. At the same time, environmental variables regulate viral abundance through particle decay and loss of infectivity. Considering the increasing pressure of global climate change on aquatic systems, it is timely to study also virus-host interactions under different environmental conditions. Well-controlled experimental studies using key virus-host model systems are used to unravel underlying mechanisms. During this presentation, I will focus on the harmful algal species Phaeocystis globosa and highlight the level of viral control on population dynamics, the influence of key environmental factors.