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Ciliate Grazing on the Bloom-Forming Microalga Gonyostomum semen
Ingrid Bergman1, Eva S Lindström1, Ingrid Sassenhagen2,3
1Department of Ecology and Genetics/Limnology, Uppsala University, Uppsala, Sweden.
Microbial Ecology
|January 18, 2024
Summary
A newly identified ciliate, Urotricha pseudofurcata, preys on the bloom-forming alga Gonyostomum semen. This grazing significantly reduces algal populations, potentially controlling blooms in humic lakes.
Area of Science:
- Aquatic Ecology
- Microbiology
- Phycology
Background:
- Gonyostomum semen, a large freshwater raphidophyte, forms extensive summer blooms in humic lakes.
- Limited top-down control by zooplankton facilitates G. semen blooms due to its large cell size and defense mechanisms.
Purpose of the Study:
- To identify and characterize a novel predator of G. semen.
- To assess the potential of this predator in controlling G. semen blooms and facilitating carbon transfer.
Main Methods:
- Isolation and culturing of a small ciliate predator.
- Sequencing for tentative identification of the ciliate as Urotricha pseudofurcata.
- Grazing experiments to quantify feeding rates and impact on G. semen populations.
Main Results:
- A ciliate species, tentatively identified as Urotricha cf. pseudofurcata, was observed to prey on G. semen.
- Grazing by U. cf. pseudofurcata significantly reduced G. semen cell concentrations.
- Variations in ciliate strain size and growth rate influenced grazing pressure.
Conclusions:
- Urotricha cf. pseudofurcata is a potential key predator controlling G. semen blooms in humic lakes.
- This ciliate facilitates the transfer of organic carbon to higher trophic levels.
- Environmental DNA data supports the ecological relevance of the G. semen-Urotricha interaction.
