High-throughput sequencing analysis reveals dynamic seasonal succession of diatom assemblages in a temperate tidal flat

Benthic diatoms are a major phytoplankton group, and play pivotal roles in coastal biogeochemical cycles and food webs. However, their community structure and diversity remain poorly understood. We investigated the variability in their taxonomic composition and diversity over 5 years in a temperate tidal flat based on high-throughput sequencing of the rbcL gene. Chao1 and Shannon species richness and diversity estimates in this study ranged from 412 to 9582 and from 2.7 to 6.3, respectively, showing higher diversity than previous estimates based on traditional morphological analyses. At the genus level, Navicula, Nitzschia, and Amphora were dominant in all seasons. However, at the 98% identity operational taxonomic unit level, seasonal changes in community structure were remarkable. A number of taxa were found only during a specific season, and only a small portion of taxa were commonly found in all seasons. This seasonal succession was mainly influenced by sediment temperatures and sand ratios. Our research provides a solid basis for the high diversity of tidal flat diatoms.