Distinct seasonality of chytrid-dominated benthic fungal communities in the neritic oceans (Bohai Sea and North Yellow Sea)

- α-diversity showed no significant seasonality or regional differences.
- β-diversity showed a significant seasonality but no regional differences.
- Chytrids, mostly unclassified at lower taxonomic ranks, dominated.
- Seasonal changes were largely due to Chytridiomycota and Basidiomycota.
- Major fungal assemblages responded differently to the environmental changes.

Benthic fungal diversities in Bohai Sea and North Yellow Sea were investigated using pyrosequencing of 18S rDNA. Overall, Chytridiomycota dominated, followed by Basidiomycota, Ascomycota and Cryptomycota, in terms of alpha diversities and relative abundance. The beta diversity of benthic fungi showed a significant seasonality but no regional differences, accounted for by contrasting relative abundances of Chytridiomycota and Basidiomycota. Significantly seasonal changes in Chytridiomycota and Basidiomycota assemblage structure were also observed, but not for Ascomycota and Cryptomycota. Environmental filtering was more important than water depth and geographic distance in shaping the distribution of benthic fungi in the neritic oceans. The overall fungal beta diversity co-varied with concentration of chlorophyll a, pH, and salinity, distance from land, and water depth. The assemblage structure of benthic Chytridiomycota, Basidiomycota, Ascomycota and Cryptomycota co-varied with different sets of environmental parameters, suggesting their niche differentiations in the coastal sediments.