• INFLUENCE OF MANGROVE ROOT BIOMASS AND SEDIMENT PROPERTIES ON MACROFAUNAL ASSEMBLAGES

Mangrove macrofaunal communities play critical roles in nutrient cycling, bioturbation, and ecosystem functioning, yet the relative importance of sediment conditions and belowground root structures in shaping these communities remains poorly understood, particularly in fragmented urban mangrove forests. This study investigated how sediment properties and belowground root biomass jointly influences macrofaunal diversity and composition across three mangrove areas in Singapore (Sungei Buloh Wetland Reserve, Pasir Ris Park, Ulu Pandan) under two dominant mangrove species, Avicennia alba and Rhizophora apiculata. Findings showed that environmental variation across the sites reflected complex legacies of human disturbance and ecological succession. Sediment depth consistently reduced species richness, diversity and evenness, while sediment texture structured assemblage evenness. Although site identity was the strongest predictor of community composition at broader spatial scales, within sites, however, fine root biomass emerged as the only local-scale driver of macrofaunal community composition. Interactions between fine root biomass, organic matter, tree species and site, further highlight how fine roots significantly mediate local habitat conditions for macrofaunal assemblages and drive compositional changes. Altogether, these findings challenge mangrove management and restoration approaches which primarily rely on aboveground indicators, and identify fine root biomass as a candidate belowground indicator of mangrove recovery. Restoration programmes may benefit from optimising belowground fine root development in nursery protocols and including monitoring of macrofaunal responses to better capture functional recovery in degraded urban mangroves.