The influence of crab burrows on sediment salinity in a Rhizophora-dominated mangrove forest in North Brazil during the dry season
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Many ecological processes are influenced by salinity. Burrowing crabs, abundant fauna of mangrove forests around the world, can facilitate sediment water fluxes, which may decrease the salinity in mangrove sediments. We investigated whether and how crab burrow density and secondary fine root biomass interact to drive sediment salinity during the dry season in a northern Brazilian mangrove forest. Areas with high density of Rhizophora mangle prop roots and areas free of such roots were compared. We found no correlation between burrow density and sediment salinity in areas with dense prop and fine roots, while crab density correlated negatively with sediment salinity in areas without prop roots, where fine root density was low. Hence, the strength of sediment desalination effects of crabs seems to be context dependent, and high root density of a salt-excluding mangrove species (R. mangle) seems to counteract the crabs’ effect. Our results complement those of a former study conducted in the same area during the rainy season, highlighting that the findings are independent from seasonality and should be considered when evaluating the overall ecological effects of crabs in mangrove ecosystems.
KeywordsRhizophora mangle Mangrove Ucides cordatus Sediment salinity
The authors would like to thank the University of Pará (UFPA), and Dr. Moirah Menezes and Dr. Ulf Mehlig for the support during the field work. The authors would also like to thank Dr. Thiago Branquinho de Queiroz from the Universidade Federal do ABC (São Paulo) for all support provided. Karen Diele received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland), and its support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (Grant Reference HR09011) and contributing institutions.
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