Abstract
The intertidal zone occupies the shore between the high and low tide marks and is subjected both to natural forces and anthropogenic activities. Compared with the coastal ecosystem, studies comparing diversity and community structure of intertidal planktonic and benthic microeukaryotes are limited. Therefore, the ecological processes mediating their assemblies remain poorly understood. Environmental rRNA from two size fractions (nano- and micro-sized) of plankton and from seasonally collected (spring and summer) benthos, together with water and sediment chemistry and concentrations of heavy metals, were used to explore diversity and community structure of microeukaryotes in intertidal zones of southeast Fujian Province, China. Benthic microeukaryotes harbored significantly higher alpha-diversity than those of the plankton, whereas no distinct patterns of organism size/seasonal distribution were observed for either community. Community compositions differed significantly between planktonic and benthic microeukaryotes, with the former presenting size-fractionated discrepancies and the latter showing seasonal variation. Community turnover between planktonic and benthic microeukaryotes was mainly driven by stramenopiles and alveolates. Distance-decay patterns were found in both communities, with the rate of community turnover being higher for planktonic than benthic microeukaryotes. Among the environmental factors measured, the concentration of Cd and the water content of sediment were closely associated with benthic community variations, whereas none of the factors measured was identified as being responsible for planktonic community variation. Phylogenetic null model analysis indicated that dispersal limitation was the most crucial ecological process mediating community assembly for both planktonic and benthic microeukaryotes in intertidal zones, with heterogeneous selection making a higher contribution to community variation of benthic than planktonic microeukaryotes. Stochastic processes, mainly dispersal limitation, were found to prevail in both communities. This study thus provides new insights into the diversity distribution and assembly mechanism of microeukaryotes in intertidal zones.
Highlights
Microeukaryotes are extremely diverse organisms that can be found in almost all ecosystems where there is life, playing essential roles in driving biogeochemical cycles and energy flow (Caron et al, 2012; Anderson et al, 2013; De Vargas et al, 2015; Adl et al, 2019)
Knowledge of the diversity and patterns of distribution of microeukaryotes, especially their community assembly mechanisms, is of great significance for understanding the ecological processes that maintain ecosystem function and for predicting how ecosystems respond to environmental change at both local and regional scales
The distribution of environmental parameters was revealed by principal component analysis (PCA) (Supplementary Figure S1)
Summary
Microeukaryotes are extremely diverse organisms that can be found in almost all ecosystems where there is life, playing essential roles in driving biogeochemical cycles and energy flow (Caron et al, 2012; Anderson et al, 2013; De Vargas et al, 2015; Adl et al, 2019). Culture-independent approaches, e.g., high throughput sequencing (HTS), have been developed, which reveal high-yield genetic information with high quality at a fraction of the cost of traditional Sanger sequencing (Goodwin et al, 2016). Such methods enable researchers to comprehensively document microeukaryotes from a variety of marine environments (Gong et al, 2015; Massana et al, 2015; Hindshaw et al, 2017; Shulse et al, 2017; Lentendu et al, 2018). Using HTS on the V9 region of the 18S ribosomal RNA gene, De Vargas et al (2015) investigated the diversity of size-fractionated planktonic eukaryotes in the sunlit ocean, revealing a large number of unassigned OTUs and highlighting the importance of organism size in planktonic community structure. Employing HTS on the V4 region of the 18S ribosomal RNA gene, Forster et al (2016) found that benthic protists had much higher diversity than planktonic protists in European coastal regions
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