Comparison of protists at Xianghai wetland (China) in summer and winter using metagenomic sequencing

This project compared the summer and winter protist communities in the Xianghai wetland, an important ecological reserve in Jilin Province, China. Based on metagenomic next-generation sequencing (mNGS) technology, the identifications of seasonally shared and unique species, calculations of diversity indices, relationship examinations between environmental factors and protistan abundances, as well as analyses of co-occurrence networks were performed. The results showed that there were 612 shared species along with 233 and 389 unique species in summer and winter, respectively. The dominant unique species were Paramoeba pemaquidensis, Babesia bigemina, Symbiodinium sp. CS-164, Amphidinium operculatum, etc., and different environmental factors might contribute to the uniqueness and seasonal preferences. The α-diversity indices suggested that biodiversity and evenness were higher in summer and dominance was higher in winter, while the β-diversity results indicated that part of the community variation was independently driven by total phosphorus or temperature and that pH acted via a combined effect with temperature. The heat maps of protistan abundances with environmental factors showed that most exhibited positive correlations with temperature, while a few had negative correlations with pH and total nitrogen. The co-occurrence networks revealed that the protistan communities in the Xianghai wetland formed a decentralized ecosystem. Whether the relationships among the small and independent protistan groups of networks were mostly cooperative or mutualistic requires further verification, and connections were more numerous in summer and closer in winter. This research provides valuable information for the seasonal monitoring of protists in the Xianghai wetland.