Differential responses of intertidal crab assemblages to rainfall intensity and dominant Mangrove species in Eastern Pacific forests

Mangrove sediments sequester large amounts of carbon, yet local controls on sediment organic carbon (SOC) remain uncertain. We tested how rainfall variability and dominant mangrove species relate to sediment physicochemical conditions and intertidal crab assemblages in five Eastern Pacific mangrove forests (Colombian Pacific coast). Sampling was conducted during the higher and lower rainfall periods in forests dominated by Rhizophora mangle or Avicennia germinans . We quantified crab density, assemblage composition, and burrow characteristics. We also measured sediment temperature, pH, conductivity, texture, bulk density, and SOC to 50 cm depth. We found a crossed response to rainfall: sediment properties differed most strongly between rainfall periods in A. germinans forests, whereas crab assemblages responded more clearly in R. mangle forests. Canonical correspondence analysis showed statistically significant but modest associations between crab assemblages and sediment variables; the reduced model explained only 14.1% of total variance, indicating weak-to-moderate relationships rather than strong environmental control. These results support partial decoupling between abiotic (sediment) and biotic (crab) responses to rainfall variability, likely shaped by habitat heterogeneity and mangrove structure. Our study underscores the need to consider mangrove dominance and short-term hydrological variability when interpreting community dynamics and carbon-related sediment processes in tropical intertidal wetlands.