Abstract
Microbial eukaryotes are pivotal components of marine ecosystems. However, compared with the pelagic environments, the diversity distribution and the driving mechanisms of microbial eukaryotes in the marine sediments have rarely been explored. In this study, sediment cores were collected along a transect from inner to outer Dongshan Bay, Southeast China. By combining high throughput sequencing of small-subunit (SSU) rRNA gene with measurements on multiple environmental variables, the genetic diversity, community structure and assembly processes, and environmental shaping factors were investigated. Alveolata (mainly Ciliophora and Dinophyceae), Rhizaria (mainly Cercozoa), and Stramenopiles (mainly Bacillariophyta) were the most dominant groups in terms of both relative sequence abundance and operational taxonomic unit (OTU) richness. Grain size composition of the sediment was the primary factor determining the alpha diversity of microbial eukaryotes followed by sediment depth and heavy metal, including chromium (Cr), zinc (Zn), and plumbum (Pb). Geographic distance and water depth surpassed other environmental factors to be the primary factors shaping the microbial eukaryotic communities. Dispersal limitation was the primary driver of the microbial eukaryotic communities, followed by drift and homogeneous selection. Overall, our study shed new light on the spatial distribution patterns and controlling factors of benthic microbial eukaryotes in a subtropical bay which is subjected to increasing anthropogenic pressure.
Highlights
Microbial eukaryotes are critical components of the microbial food webs and play pivotal roles as primary producers, consumers, decomposers, and trophic links in influencing the biogeochemical processes in the marine aquatic systems (Worden et al, 2015; Caron et al, 2016)
The contribution of Rhizaria to the total microbial eukaryotic communities generally increased with the increasing water depth in the DNA dataset a smaller portion was found in the RNA extractions (Not et al, 2009; Xu et al, 2017a)
In term of operational taxonomic unit (OTU) richness, the sunlit layer of the ocean was found to be represented by diplonemids (Excavata), which sometimes surpassed other groups to be the most dominant group (Flegontova et al, 2016)
Summary
Microbial eukaryotes (protist) are critical components of the microbial food webs and play pivotal roles as primary producers, consumers, decomposers, and trophic links in influencing the biogeochemical processes in the marine aquatic systems (Worden et al, 2015; Caron et al, 2016). They are pivotal components of the marine sediment ecosystems and play diverse roles in maintaining ecosystem function and biogeochemical cycling (Orsi, 2018). The diversity of benthic microbial eukaryotes was considered “the under-charted majority” (Forster et al, 2016)
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