Impact of Seasonality on Copper Bioavailaility to Crabs (Ucides cordatus, Linnaeus, 1763) in Mangrove Soils of Todos os Santos Bay (Bahia, North Eastern Brazil)

Abstract

Crab and soil samples were seasonally collected at four mangrove sites (Cacha Prego, CP; Ponta Grossa, PG; Ilha de Maré, IM; and Pitinga, PT) in Todos os Santos Bay, in NE Brazil. Total Cu levels in soils ranged from 2.5 to 89.4 mg kg−1, while in crab organs (muscles, hepatopancreas, and gills), Cu ranged from 20 to 1,320 mg kg−1, with the highest concentrations found in the Ilha de Maré population, where soils showed a clear Cu enrichment. Total Cu content did not explain the abnormally high Cu concentrations observed in crabs from Pitinga, where total content in soil was low. Geochemical partitioning indicated that most of the potentially bioavailable Cu was found in the oxidizable fractions, pyrite and organic matter. Pyrite oxidation during the dry season led to increased Cu bioavailability. This process was of relevance in soils of the Pitinga mangrove, where sulfide oxidation led to soil acidification and to an increase in Cu associated with the most labile fractions.