The bioturbation contribution of tropical sea cucumber density on the microbial community of the coral reef sediment.

Microorganisms serve as a key driving factor of coral reef ecosystems, which are influenced by marine benthic animals. However, research on influences of benthic animals on the microbial community structure of sediments is still limited. In this study, we used deposit-feeding sea cucumbers as the model organism and employed metabarcoding sequencing to analyze the effect of Holothuria atra density on the community structure of prokaryotic microorganisms in coral reef sediments. The results indicated that high-density H. atra significantly altered sediment prokaryotic community structure, while its effects on α-diversity remained non-significant. Tax4Fun based functional prediction suggested that pathways related to folding, sorting and degradation, energy metabolism, metabolism of cofactors and vitamins, and signal transduction were more highly represented in the high-density treatment. We hypothesize that high-density H. atra bioturbation may influence microbial processes involved in the turnover of organic matter within coral reef sediments. This study highlights that the effect of deposit-feeding holothurians on sediment microorganisms in the coral reef area is density-dependent. The findings indicate that higher densities of H. atra exerted a stronger influence on sediment microbial communities under the experimental conditions. Whether such microbially mediated effects translate into broader ecosystem-level benefits in coral reef areas warrants further investigation.