DEPTH-DEPENDENT DYNAMICS OF PROTIST COMMUNITIES AS AN INTEGRAL PART OF SPRING SUCCESSION IN A FRESHWATER RESERVOIR

Protists are essential contributors to eukaryotic diversity and exert profound influence on carbon fluxes and energy transfer in freshwaters. Despite their significance, there is a notable gap in research on protistan dynamics, particularly in deeper strata of temperate lakes. We aimed to address this by integrating protists into the well-described spring dynamics of Římov reservoir, Czech Republic. Over a two-month period covering transition from mixing to stratification, we collected water samples from three depths (0.5, 10 and 30 m) and up to three times per week. Microbial eukaryotic and prokaryotic communities were analysed using SSU rRNA gene amplicon sequencing and dominant protistan groups were enumerated by CARD-FISH. Following the rapid changes in environmental and biotic parameters during spring, microbial communities displayed swift transition from a homogeneous to distinct strata-specific communities. Epilimnion exhibited the prevalence of auto-, mixotrophic protists dominated by cryptophytes and associated with spring algal bloom-specialized bacteria. In contrast, meta- and hypolimnion protist community was dominated by putative parasitic Perkinsozoa, detritus or particle-associated ciliates, cercozoans and excavates co-occurring with bacteria associated with lake snow. Our high-resolution sampling matching the typical dividing time of microbes along with combined microscopic and molecular approach and inclusion of all the components of microbial food web allowed us to follow depth-specific populations' succession and interactions in a deep lentic ecosystem.

Primary Presenter: Indranil Mukherjee, Biology Centre, Czech Academy of Sciences (indranilmukherjee04@yahoo.com)

Authors:

Indranil Mukherjee, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (indranilmukherjee04@yahoo.com)

Vesna Grujčić, Stockholm University  (grujcicv@gmail.com)

Michaela Salcher, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (michaelasalcher@gmail.com)

Petr Znachor, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (znachy@gmail.com)

Jaromír Seďa, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (seda@hbu.cas.cz)

Miloslav Devetter, Institute of Soil Biology and Biogeochemistry, Biology Centre, Czech Academy of Sciences  (devetter@upb.cas.cz)

Pavel Rychtecký, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (pavel.rychtecky@hbu.cas.cz)

Karel Šimek, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (ksimek@hbu.cas.cz)

Tanja Shabarova, Institute of Hydrobiology, Biology Centre, Czech Academy of Sciences  (shabrik@gmail.com)