How different are the nematode communities between the two main habitats of a mangrove forest? Insights from a subtropical mangrove forest

Abstract

Sediment (inbenthic habitat) and fallen leaf (epibenthic habitat) are two distinguishable habitats inside the mangrove forests. In September 2020, sediment samples and leaf litter were collected from a subtropical mangrove forest, namely the Futian Mangrove Nature Reserve, in China. Subsequently, free-living marine nematodes were investigated to assess differences between the two habitats, and understand the important factors shaping nematode community in the mangrove ecosystem. Leaf litter were collected and divided into three decay degrees to reveal the successive changes of nematodes with leaf litter degradation. The results showed that nematode community on fallen leaves was characterized by the abundant Monhysteridae nematodes and the non-selective deposit feeders, which was different from the community in sediments where Linhomeidae and Chromadoridae nematodes and selective deposit feeders dominated. In general, bacterivores dominated at both habitats. Spatial variations of nematode community structure and diversity were observed at both habitats. TOM appeared as the significant factor affecting nematode community in the sediment, exhibited a negative correlation with nematodes diversity; while the spatial variations in nematodes on the fallen leaves were related to the concentrations of condensed tannin of the leaf litter. In addition, the spatial differences in nematode abundance and species composition observed in this study also were linked to differences in mangrove tree species. A subtle increase in the relative abundance of Diplolaimelloides and Diplolaimella with increasing degradation of leaves was observed, which might be due to their characteristics of opportunistic colonizers, the continuous changes in the concentrations of condensed tannin and/or microbial activity of the leaf litter.