Abstract
Mangrove ecosystems, where litter and organic components are degraded and converted into detrital materials, support rich coastal fisheries resources. Sesarmid (Grapsidae) crabs, which feed on mangrove litter, play a crucial role in material flow in carbon-rich and nitrogen-limited mangrove ecosystems; however, the process of assimilation and conversion into detritus has not been well studied. In this study, we performed microbiome analyses of intestinal bacteria from three species of mangrove crab and five sediment positions in the mud lobster mounds, including the crab burrow wall, to study the interactive roles of crabs and sediment in metabolism. Metagenome analysis revealed species-dependent intestinal profiles, especially in Neosarmatium smithi, while the sediment microbiome was similar in all positions, albeit with some regional dependency. The microbiome profiles of crab intestines and sediments were significantly different in the MDS analysis based on OTU similarity; however, 579 OTUs (about 70% of reads in the crab intestinal microbiome) were identical between the intestinal and sediment bacteria. In the phenotype prediction, cellulose degradation was observed in the crab intestine. Cellulase activity was detected in both crab intestine and sediment. This could be mainly ascribed to Demequinaceae, which was predominantly found in the crab intestines and burrow walls. Nitrogen fixation was also enriched in both the crab intestines and sediments, and was supported by the nitrogenase assay. Similar to earlier reports, sulfur-related families were highly enriched in the sediment, presumably degrading organic compounds as terminal electron acceptors under anaerobic conditions. These results suggest that mangrove crabs and habitat sediment both contribute to carbon and nitrogen cycling in the mangrove ecosystem via these two key reactions.
Highlights
Mangroves are highly productive intertidal ecosystems that can transfer organic matter and nutrients from forest sediments to the coastal ocean [1,2,3,4,5,6,7]
In N. smithi, the Simpson index was similar between individual crabs, indicating that the homogeneity of operational taxonomic unit (OTU) was unchanged among the samples
In the Venn diagram analysis of crabs, 105 out of the 1422 OTUs were shared by the three crab species, while 400, 362, and 289 OTUs were unique to N smithi, E. versicolor, and P. indiarum, respectively (S3 File)
Summary
Mangroves are highly productive intertidal ecosystems that can transfer organic matter and nutrients from forest sediments to the coastal ocean [1,2,3,4,5,6,7]. It has long been considered that mangrove leaf litter is a major carbon source that is degraded in the sediment and converted into detrital materials as the basis of the detritus food chain in coastal areas [1, 4, 5]. The abundance and diversity of crabs can affect organic matter degradation and sediment characteristics[17, 19,20,21]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
