Seasonality of parasitic and saprotrophic zoosporic fungi: linking sequence data to ecological traits

Abstract

Zoosporic fungi of the phylum Chytridiomycota (chytrids) regularly dominate pelagic fungal communities in freshwater and marine environments. Their lifestyles range from obligate parasites to saprophytes. Yet, linking the scarce available sequence data to specific ecological traits or their host ranges constitutes currently a major challenge. We combined 28 S rRNA gene amplicon sequencing with targeted isolation and sequencing approaches, along with cross-infection assays and analysis of chytrid infection prevalence to obtain new insights into chytrid diversity, ecology, and seasonal dynamics in a temperate lake. Parasitic phytoplankton-chytrid and saprotrophic pollen-chytrid interactions made up the majority of zoosporic fungal reads. We explicitly demonstrate the recurrent dominance of parasitic chytrids during frequent diatom blooms and saprotrophic chytrids during pollen rains. Distinct temporal dynamics of diatom-specific parasitic clades suggest mechanisms of coexistence based on niche differentiation and competitive strategies. The molecular and ecological information on chytrids generated in this study will aid further exploration of their spatial and temporal distribution patterns worldwide. To fully exploit the power of environmental sequencing for studies on chytrid ecology and evolution, we emphasize the need to intensify current isolation efforts of chytrids and integrate taxonomic and autecological data into long-term studies and experiments.

Fungal parasitism on diatoms alters formation and bio–physical properties of sinking aggregates

“…We sampled a natural phytoplankton community in a temperate lake (Lake Stechlin), which comprised mostly filamentous cyanobacteria ( Planktothrix , 398 ± 74 filaments mL −1 and Aphanizomenon/Pseudanabaena , combined 443 ± 11 filaments mL −1 ) and diatoms ( Synedra 280 ± 63 cell mL −1 and Stephanodiscus/Fragilaria , combined 1382 ± 345 cells mL −1 ). Chytrid infections were highest on Planktothrix , Synedra , and Fragilaria cells, and thus, we inspected these taxa in more detail (~2% infection prevalence during our sampling, while prevalences of up to 44% on Synedra and Fragilaria have been observed previously at the same location) 24 . Bacterial abundances were ≥17-times higher on infected cells than on non-infected cells ( Planktothrix 0.1 ± 1.2 and 13.4 ± 14.8 bacteria 100 µm-filament −1 , Synedra: 0.9 ± 2.2 and 17.5 ± 20.9 bacteria diatom −1 , and Fragilaria : 0.5 ± 1.5 and 8.8 ± 6.3 bacteria diatom −1 , respectively, Fig.…”

“…For instance, members of the fungal division Chytridiomycota, referred to as chytrids, can thrive as microparasites on phytoplankton cells. These chytrids are traditionally well documented in lakes 23 , especially during bloom events when host abundances are high 24,25 . More recently, they have also gained increasing attention in coastal systems after being observed via microscopy, for instance, in the highly productive upwelling region off Chile 26 , in the Arctic Ocean 27,28 , and during harmful algae blooms in the Mediterranean Sea 29 .…”

Crop diversity promotes the recovery of fungal communities in saline-alkali areas of the Western Songnen Plain

“…Most saprotrophic fungi fall within the phyla of Ascomycota and Zygomycota have been categorized as r-members ( Yao et al, 2017a ). Similarly, Chytridiomycota also contains saprotrophic fungi and is commonly considered an r-member ( Van den Wyngaert et al, 2022 ). The Ascomycota, the largest fungal phylum, which has been found to be widely distributed in soil, may be the most important phylum in saline restoration ecosystems ( Fierer, 2017 ).…”

Critical role of parasite‐mediated energy pathway on community response to nutrient enrichment

“…Although edible phytoplankton is the primary food source of zooplankton, zoospores might form an important alternative food source during phytoplankton blooms dominated by inedible species (Gsell et al, 2022 ; Rasconi et al, 2014 ). In temperate regions, the mycoloop might regularly form an important energy source for zooplankton during the late summer season, when phytoplankton communities are typically dominated by less edible algae (Sommer et al, 2012 ; Van den Wyngaert et al, 2022 ), but also during spring blooms if dominated by cyanobacteria (Rasconi et al, 2012 ). Furthermore, its importance may be on the rise with worldwide eutrophication and global warming leading to the increasing dominance of often inedible or even toxic cyanobacteria (Bogard et al, 2020 ; Huisman et al, 2018 ).…”