Mercury dynamics in surface-active soil invertebrates from an ecological reserve in the Brazilian savanna

This study evaluated total mercury (THg) distribution and accumulation in soil, litter, and surface-active soil invertebrates at the Águas Emendadas Ecological Station (ESECAE), a savanna reserve in central Brazil. We assessed whether THg differed between soil and litter; whether soil pH and organic matter influenced soil THg, the degree of THg accumulation in invertebrates relative to soil and litter; whether feeding habits structured epigeic soil fauna according to THg concentrations; and whether biomagnification could be inferred within the local trophic network. THg concentrations were significantly higher in litter (51.7 ± 5.6 ng g⁻¹) than in soil (34.9 ± 13.5 ng g⁻¹; t = 4.402, df = 7, p = 0.0032). Soil organic matter was positively associated with soil THg (R² = 0.455, p = 0.039), whereas pH showed no significant relationship. Invertebrate THg concentrations ranged from 0.095 to 970.70 ng g⁻¹, reaching values approximately 15 times higher than those in soil or litter. Overall, 83.75% of samples showed bioaccumulation potential, and macroaccumulation predominated relative to both soil (80.38%) and litter (68.53%). Grouping by feeding habits revealed consistent accumulation patterns, indicating trophic-level biomagnification. Predator frequency increased from 9.1% in the lowest THg group to 45.5% in the highest, while phytophagous organisms decreased from 26.1% to 2.3%. Our results underscore the complexity of mercury cycling in terrestrial food webs and highlight the role of ecological traits and environmental parameters in modulating mercury bioavailability and transfer.