ABSTRACT Comprehensive annual studies on the seasonal dynamics of heterotrophic protists in ice-covered hypereutrophic systems are scarce, despite their vital roles in aquatic microbial food webs. We examined the community composition and abundance of larger-bodied (15 μm) heterotrophic protists over 13 consecutive months in a northern temperate hypereutrophic lake that experiences four months of ice cover. The abundance of larger-bodied heterotrophic protists exhibited considerable seasonal variation, with an 852-fold annual fluctuation (from 100 to 85 200 individuals per liter), significantly surpassing the typical 10–50-fold variations observed in less extreme systems. Community functional composition underwent complete restructuring between the ice-covered and open-water periods: sessile Vorticella dominated under ice (17.7 times more abundant), while planktonic Strobilidium was 171 times more abundant during the open-water season. Testate amoebae (Difflugia) were absent under ice. Correlation analyses identified 17 significant associations between taxa and environmental parameters, with the strongest being Tintinnopsis sp.1 and redox potential (ρ = 0.898). These findings highlight that ice cover prompts a fundamental restructuring of larger-bodied protist communities, with different functional groups prevailing under contrasting seasons. Climate-driven reductions in ice cover duration may alter the structure of protist communities in northern temperate lakes, potentially triggering cascading effects on microbial food webs.
Husk et al. (Wed,) studied this question.