The potential of Blue Carbon as an integral part of global climate change adaptation and mitigation strategies requires quantification of drivers and rates of organic carbon (OC) burial and storage. However, there is limited recognition of how land use impacts benthic assemblages, their bioturbation potential, and OC burial in mangrove forests and tidal flats. Here we evaluated the effects of mangrove deforestation on benthic bioturbation potential (BPc), sediment accretion rates (SARs), and OC and total nitrogen (TN) burial in mangrove soils and tidal flat sediments from three estuaries in tropical Brazil. SARs based on 210 Pb dating varied significantly among undisturbed estuaries (2.1-18.6 mm yr −1) and the OC and TN burial rates were respectively 46% and 16% higher than global averages. The cleared mangrove sites had a twofold lower SAR, 40-fold lower OC burial, and over 100-fold lower TN burial when compared to undisturbed forests, revealing the pervasive impacts of land use. Variation in benthic assemblage structure and BPc among sites suggests that the composition and activity of macrofaunal communities may facilitate OC burial in some cases, yet the global extent and significance of bioturbation requires further study. Our work reveals a strong spatial variability in C burial in undisturbed mangrove forests and a decreased capacity of mangroves to accumulate C and sediments due to land use effects.

Tropical estuaries are highly productive and support diverse benthic assemblages within mangroves and tidal flats habitats. Determining differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support for management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition were evident, with mangrove forests being dominated by annelids (Oligochaeta and Capitellidae) whereas peracarid crustaceans were also abundant on tidal flats. Macrofaunal biomass, density and secondary production also differed between habitats and among estuaries. Those differences were related both to the composition of benthic assemblages and to random spatial variability, underscoring the importance of hierarchical sampling in estuarine ecological studies. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.

Estuaries are highly productive and support diverse benthic assemblages, but few estimates of benthic production are available for most ecosystems. In tropical estuaries mangroves and tidal flats are typical habitats with high spatial heterogeneity of benthic macrofaunal assemblages. However, accessing differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support to management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition, biomass, density and secondary production were significant, but also varied between estuaries. Macrofaunal secondary production differed between estuaries and between tidal flat and mangrove habitats, and those differences were related to the composition of benthic assemblages. High benthic production were associated with tidal flats in estuaries with presumable less human impacts, although benthic assemblages from mangrove sediments had similar production irrespective of human disturbances. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.

No abstract

Estuaries are highly productive and support diverse benthic assemblages, but few estimates of benthic production are available for most ecosystems. In tropical estuaries mangroves and tidal flats are typical habitats with high spatial heterogeneity of benthic macrofaunal assemblages. However, accessing differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support to management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition, biomass, density and secondary production were significant, but also varied between estuaries. Macrofaunal secondary production differed between estuaries and between tidal flat and mangrove habitats, and those differences were related to the composition of benthic assemblages. High benthic production were associated with tidal flats in estuaries with presumable less human impacts, although benthic assemblages from mangrove sediments had similar production irrespective of human disturbances. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.