Effect of co-occurrence of marine nematodes and microbes on carbon and nitrogen cycles in coastal sediments

Abstract:

[Objective] This study is aimed to investigate the interaction effects of marine free-living nematodes and microbes on carbon and nitrogen cycles in coastal sediments. [Methods] We used 16S rRNA and 18S rRNA high-throughput sequencing technology to inspect the diversity and community of bacteria, archaea and eukaryotes in 33 coastal sediment samples. The Spearman correlation method was adapted to analyze the co-occurrence pattern between marine nematodes and microbes (bacteria and archaea), to recognize the microbial group with significant correlation with nematodes. [Results] In summer, the average relative abundance of nematode OTUs decreased with the increasing depths both in mangrove and intertidal mudflat sediments. Similar pattern was discovered in winter samples with one exception that the averaged relative abundance of nematode OTUs in deeper layer was significantly higher than that in upper layer. The five most abundant marine nematode OTUs belong to Monhysterida (47%), Chromadorida (19%), Enoplia (16%) and Tylenchida (9%). Those OTUs are significantly correlated with Thermoplasmata, Bathyarchaeota, gamma-and delta-Proteobacteria. [Conclusion] In the wetland sediments sampled from Mai Po Nature Reserve of Hong Kong, the microbes those have significant correlation with nematodes play important roles in carbon, nitrogen and sulfur cycles. It implies that the potential interaction effects between marine nematodes and microbes have crucial impacts on biogeochemical cycles. Our results could help us to uncover the ecological function of nematodes in the environments, to better understand the roles of marine nematodes in the benthic ecosystems.