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Journal of Plankton Research


Vernal pools are dynamic freshwater ecosystems that dry during the summer. These unique habitats are vital to a number of well-studied animal species but there is little documentation of the diversity of the SAR—Stramenopila, Alveolata and Rhizaria—clade in vernal pools. Here, we characterize the protist community over a portion of the hydroperiod as the vernal pool transitions from its winter stage through its drying out in late summer. Our study focuses on the SAR clade, which encompasses a broad range of morphological diversity and a variety of trophic modes within the microbial food web. Using high-throughput sequencing, we investigate the total community (DNA) and the active (RNA) members on a temporal scale. These molecular data reveal seasonality within microbial communities, suggesting a larger community of autotrophs in the winter followed by an increase in heterotrophs in the summer. Our analysis also suggests the presence of a microbial seed bank, a collection of encysted protists, in the sediments below the pool. We hypothesize the seed bank allows for community turnover: taxa encyst in the sediment in poor environmental conditions and exit their cysts when favorable conditions occur. We also observe seasonal preference and partitioning of the environment within clades of close relatives, including taxa closely related to the ciliate Halteria and the oomycete Haptoglossa. These data provide insights into the seasonal patterns of a frequently overlooked group of organisms in this unusual environment.


microbial eukaryotes, freshwater, high throughput sequencing, temporary forest pond





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© The Author(s) 2018. Published by Oxford University Press. All rights reserved.


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