Impacts of the Zhe-Min Coastal Current on the biogeographic pattern of microbial eukaryotic communities

Abstract One interesting question in the study of marine microbial ecology is how ocean currents affect the geographic distributions of microorganisms. The Zhe-Min Coastal Current (ZMCC) is strong in winter and could influence the plankton communities in Hong Kong coastal waters by bringing species from far north. In this study, we investigated the spatial distribution of microbial eukaryotic communities (MEC) in the ZMCC and evaluated the relative contribution of environmental and spatial factors on the variations of MEC. The results showed that diverse taxa of diatoms (Bacillariophyceae) and Dinophyceae (Dinoflagellata) dominated the sequences in all samples. MEC compositions in the Hong Kong coastal waters were closer to the communities in the ZMCC than other adjacent areas. Abundant and rare taxa exhibited a similar geographic pattern of distribution. Environmental factors alone explained 14.1% and 27.6% of the variations in the entire and abundant communities, respectively, which were higher than pure spatial factors (8.3% and 19.5%, respectively). The lower importance of spatial factors (dispersal limitation) might be explained by the passive dispersal favored by current transportation and was further supported by the high immigration rate computed in the neutral community model (NCM). High fitness to the NCM (R2 = 0.74) indicated the predominant role of neutral process in shaping the MEC. The large proportion of unexplained variations in rare taxa suggested the importance of other potential factors, especially biotic interactions. Our study demonstrates the influences of coastal current on local and regional structures of MEC.