Differential mediation of biogeochemical processes through bioturbation by fiddler and sesarmid mangrove crabs

Macrobenthic bioturbation is vital to facilitate nutrient turnover in estuarine ecosystems and drives spatial heterogeneity in the sediment matrix. In this study, we compared the sediment physico-chemical properties, microbial community structure and functional genes in vertically-stratified sediment samples from bioturbated (burrows of Parasesarma bidens and Tubuca arcuata) and non-bioturbated area in mangrove ecosystems (the Hanjiang River Estuary, Southern China). The result indicated that bioturbation by P. bidens and T. arcuata had significantly different effects on sediment properties, with the action of P. bidens enhancing nutrient accumulation while T. arcuata promoted N₂O emission. Burrow microhabitats harbored distinctive microbial communities although the dominant phylum and genera shared considerable similarity with the control sediment surface with Woeseia dominating in vertical profiles across different habitats. Co-occurrence network analysis revealed that crab bioturbation promoted formation of less complex but more functionally-specialized microbial communities. Crab bioturbation enhanced nutrient metabolism and separated clusters in dendrogram demonstrated the species-specific effect between P. bidens and T. arcuata. Our work verified the significance of bioturbators in regulating biogeochemical processes and highlighted the species-specific bioturbation effect between two dominant mangrove crabs (P. bidens vs. T. arcuata).