Ciliate grazing on the bloom-forming microalga Gonyostomum semen Ciliate grazing on the bloom-forming microalga Gonyostomum semen 2024-398-1 https://doi.org/10.57804/bzkb-3987 Swedish National Data Service Svensk nationell datatjänst Landing page Ciliate grazing on the bloom-forming microalga Gonyostomum semen Ciliate grazing on the bloom-forming microalga Gonyostomum semen 2024-398-1 https://doi.org/10.57804/bzkb-3987 Sassenhagen, Ingrid Sassenhagen, Ingrid 146-300-188 Swedish National Data Service Svensk nationell datatjänst Landing page Cell count data set from infection experiment containing 8 columns, which are described below. Day: Day of the experiment. Date: Date of the experiment. Code: Unique identifier for each combination of G. semen and ciliate strains. G.semen_strain: Identifier for the G. semen strain used in this treatment. Ciliate_strain: Identifier for the ciliate strain used in this treatment. G. semen mono-cultures (without ciliates) are named "control". Treatment: Distinguishes control and grazing (with ciliates) treaments. Count: Specifies which taxon was counted (G. semen or ciliate). cells/ml: Cell concentration counted under an inverted microscope in cells/mL. The freshwater raphidophyte Gonyostomum semen forms extensive summer blooms in northern European humic lakes. The development of these blooms might be facilitated by a lack of natural top-down control, as few zooplankton species are able to prey on these large algal cells (up to 100µm) that expel trichocysts upon physical stress. In this study, we describe a small ciliate species (<17µm) that preys on G. semen by damaging the cell membrane until cytoplasm and organelles spill out. Sequencing of clonal cultures of the ciliate tentatively identified it as the prostomatid species Urotricha pseudofurcata. Grazing experiments illustrated that feeding by U. cf. pseudofurcata can significantly reduce cell concentrations of the microalga. However, differences in cell size and growth rate between two investigated ciliate strains resulted in noticeably different grazing pressure. Environmental sequencing data from five different lakes supported potential interactions between the two species. Urotricha cf. pseudofurcata might, thus, play an important role in aquatic ecosystems that are regularly dominated by G. semen, reducing the abundance of this bloom-forming microalga and enabling transfer of organic carbon to higher trophic levels. The dataset was originally published in DiVA and moved to SND in 2024. Cellräkningsdata från infektionsexperiment. Se engelsk beskrivning för mer information. Datasetet har ursprungligen publicerats i DiVA och flyttades över till SND 2024. Access to data through SND. Data are freely accessible. Åtkomst till data via SND. Data är fritt tillgängliga. openAccess