Temperature mainly determines the temporal succession of the photosynthetic picoeukaryote community in Lake Chaohu, a highly eutrophic shallow lake

Abstract

Photosynthetic picoeukaryotes (PPEs) are key players in aquatic systems, while their diversity and community composition dynamics remain poorly understood. The monthly composition of PPEs in Lake Chaohu was investigated using a combination of flow cytometry sorting and high throughput sequencing. Results indicated that temperature is the most important factor shaping PPEs community structure. The PPEs community can be categorized into three groups that are dominant at different temperature ranges: high temperature (>21.8 °C), intermediate temperature (between 9.8 °C and 21.8 °C) and low temperature (<9.8 °C). At the supergroup level, Cryptophyta were dominant at the intermediate temperature level, and Bacillariophyta were prevalent at low temperatures. In comparison, Chlorophyta PPEs were sensitive to temperature at the order level. Molecular network analysis using 18S rDNA sequencing results from sorted samples revealed that the Operational Taxonomic Units (OTUs) of PPE from the same taxonomic groups were predominantly positive, implying that they were occupying similar niches. The cooccurrence patterns between PPEs and fungi were mostly negative. In particular, OTU101, which was associated with Chytridiomycota, was negatively related to many OTUs belonging to Chlorophyta and Diatom, indicating that their potential parasitic associations may be not species-specific.

Keywords: Ecological network; Heterotrophic picoeukaryotes; Photosynthetic picoeukaryotes (PPEs); Temporal succession.