Morphological and molecular analyses of season-specific responses of freshwater ciliate communities to top-down and bottom-up experimental manipulations

作者：Usman Asghar, Indranil Mukherjee, Bettina Sonntag, Caio César Pires de Paula, Vojtěch Kasalický, Paul‐Adrian Bulzu, Anusha Singh, Tanja Shabarova, Kasia Piwosz, Karel Šimek · 发表于：mSystems · 年份：2025 · DOI：10.1128/msystems.00304-25 · 被引用次数：5 · 研究领域：Microbial Community Ecology and Physiology、Protist diversity and phylogeny、Marine and coastal ecosystems

ABSTRACT In aquatic microbial food webs, ciliates represent an important trophic link in the energy transfer from prokaryotes, algae, and heterotrophic nanoflagellates (HNFs) to higher trophic levels. However, the trophic role of abundant small ciliates (<20 µm) is not clearly understood. To unveil their trophic linkages, we conducted two experiments manipulating both top-down and bottom-up controlling factors, thus modulating the trophic cascading and bacterial prey availability for protists during contrasting spring and summer seasons with samples collected from a freshwater meso-eutrophic reservoir. Water samples were size fractionated to modify food web complexity, i.e., 10 µm, 20 µm, and unfiltered control and amended with bacterial prey additions. The samples were analyzed by morphological and sequencing techniques. The bacterial amendments triggered strong ciliate growth following the peaks of HNFs in the 10 and 20 µm treatments, reflecting a trophic cascading from HNFs to raptorial prostome ciliates ( Balanion planctonicum and Urotricha spp.) in spring. In summer, HNFs and ciliates peaked simultaneously, suggesting the important trophic cascade also from bacteria to bacterivorous scuticociliates ( Cyclidium glaucoma and Cinetochilum margaritaceum ) and HNFs. In spring, unfiltered treatments showed stronger ciliate top-down control by zooplankton than in summer. The sequence analysis revealed season-specific manipulation-induced shifts in ciliate communities and the...