Microbiota and soil fauna mediate litter decomposition and associated carbon and nitrogen dynamics in mangrove blue carbon ecosystems: insights from a coastal lagoon in Malaysia

A 120-day field study was conducted in a Malaysian mangrove ecosystem to investigate the effect of mesh size (0.20 mm, 0.50 mm, and unprotected leaf litter/open litter) on litter decomposition and associated carbon (C)/nitrogen (N) release from two mangrove species, namely Bruguiera gymnorrhiza and Rhizophora mucronata. We hypothesized that excluding fauna from various functional groups through the use of litter mesh bags would significantly impact the decay rates and related dynamics of C and N among the treatments. As expected, marked differences in the decay rate were observed among treatments, with higher decay rates in the unprotected litter. Notably, the decay rates for B. gymnorrhiza were significantly greater than those observed for R. mucronata. Microbial communities played a more substantial role in decomposition, contributing 49%, surpassing the impact of macrofauna (29% contribution) and mesofauna (25% contribution). Consistent with our hypothesis, significant differences in C and N loss were observed among treatments for both species over time. Our findings underscore the influential role of various soil faunal functional groups in litter decomposition, significantly contributing to the release of C and N. This emphasizes their crucial role in the biogeochemical cycling of C and N in blue carbon ecosystems.