Patterns And Processes In Marine Microeukaryotic Community Biogeography From Xiamen Coastal Waters And Intertidal Sediments,Southeast China

Microeukaryotes are found in almost all environments on Earth and cover a wide spectrum of cell sizes,shapes and taxonomic affiliations.These microorganisms,such as algae,protozoa and fungi play a variety of crucial roles in marine ecosystems.Studies about microeukaryotic community assembly have implications ranging from ecosystem stability and functions to human health.However,little is known about the relative importance of the processes that drive planktonic and benthic microeukaryotic biogeography in subtropical offshore areas.This study compares the microeukaryotic community compositions(MCCs)from coastal waters and intertidal sediments around Xiamen Island,southeast China,using high-throughput sequencing of 18S rDNA,and quantifies the relative contributions of spatial and environmental variables on the distribution of marine MCCs(including total,dominant,rare and conditionally rare taxa).The main results are as follows:1.Our results in coastal waters and intertidal sediments around Xiamen Island showed that planktonic and benthic MCCs were significantly different,and the benthic richness(6627 OTUs)was more higher than that for plankton(4044 OTUs)with the same sequencing effort.The proportions of OTUs and sequences of Excavata were significantly higher in the benthos than in the plankton.In contrast,Alveolata and Diatomea had significantly higher richness and abundance in planktonic than in benthic communities.2.Mantel tests revealed that environmental factors(salinity,TP,TN)were significantly related to the change of benthic MCCs.However,planktonic MCCs might be affected by more complex mechanisms(such as biotic interactions and other unmeasured ecological variables).Further,benthic MCCs exhibited a significant distance-decay relationship,whereas the planktonic communities did not,This result might be ascribed to the plankton were extremely dynamic largely due to current and/or other ecological factors.3.Both the environmental and spatial factors played significant roles in influencing the biogeography of total and dominant planktonic and benthic microeukaryotic communities,although their relative effects on these community variations were different.However,a high proportion of unexplained variation in the rare taxa(78.1%to 97.4%)and conditionally rare taxa(49.0%to 81.0%)indicated that more complex mechanisms may influence the assembly of the rare subcommunity.These results demonstrate that patterns and processes in marine microeukaryotic community assembly differ among the different habitats(coastal water vs.intertidal sediment)and different subcommunities(total,dominant,rare and conditionally rare microeukaryotes),and provide novel insight on the microeukaryotic biogeography and ecological mechanisms in coastal waters and intertidal sediments at local scale.