Soil greenhouse gas fluxes partially reduce the net gains in carbon sequestration in mangroves of the Brazilian Amazon.

There is interest in assessing the potential climate mitigation benefit of coastal wetlands based on the balance between their greenhouse gas (GHG) emissions and carbon sequestration. Here we investigated soil GHG fluxes (CO and CH) on mangroves of the Brazilian Amazon coast, and across common land use impacts including shrimp farms and a pasture. We found greater methane fluxes near the Amazon River mouth (1439 to 3312 μg C m h), which on average are equivalent to 37% of mangrove C sequestration in the region.

Seasonal drives on potentially toxic elements dynamics in a tropical estuary impacted by mine tailings.

This study investigates the impact of seasonality on estuarine soil geochemistry, focusing on redox-sensitive elements, particularly Fe, in a tropical estuary affected by Fe-rich mine tailings. We analyzed soil samples for variations in particle size, pH, redox potential (Eh), and the content of Fe, Mn, Cr, Cu, Ni, and Pb. Additionally, sequential extraction was employed to understand the fate of these elements.

How do soil processes control the provision of ecosystem services in coastal wetlands?

Coastal wetlands are known for their diverse ecosystems, yet their soil characteristics are often misunderstood and thought to be monotonous. These soils are frequently subjected to saline water saturation, leading to unique soil processes. However, the combination and intensity of these processes can vary considerably across different ecosystems.

Soil greenhouse gas emissions from dead and natural mangrove forests in Southeastern Brazil.

Mangroves forests may be important sinks of carbon in coastal areas but upon their death, these forests may become net sources of carbon dioxide (CO) and methane (CH) to the atmosphere. Here we assessed the spatial and temporal variability in soil CO and CH fluxes from dead mangrove forests and paired intact sites in SE-Brazil. Our findings demonstrated that during warmer and drier conditions, CO soil flux was 183 % higher in live mangrove forests when compared to the dead mangrove forests.

The inclusion of Amazon mangroves in Brazil's REDD+ program.

The Legal Amazon of Brazil holds vast mangrove forests, but a lack of awareness of their value has prevented their inclusion into results-based payments established by the United Nations Framework Convention on Climate Change. Based on an inventory from over 190 forest plots in Amazon mangroves, we estimate total ecosystem carbon stocks of 468 ± 67 Megagrams (Mg) ha; which are significantly higher than Brazilian upland biomes currently included into national carbon offset financing. Conversion of mangroves results in potential emissions of 1228 Mg COe ha, which are 3-fold higher than land use emissions from conversion of the Amazon rainforest.

Pyrogenic carbon stocks and its spatial variability in soils from savanna-forest ecotone in amazon.

Forest fragments from Amazon are important long-term carbon (C) reservoirs with an essential role in the global C balance. They are often impacted by understory fires, deforestation, selective logging and livestock. Forest fires convert soil organic matter into pyrogenic carbon (PyC), but little is known about its distribution and accumulation along the soil profile.

The novel mangrove environment and composition of the Amazon Delta.

Both freshwater floodplain (várzeas and igapós) forests and brackish-saline mangroves are abundant and well-described ecosystems in Brazil. However, an interesting and unique wetland forest exists in the Amazon Delta where extensive mangroves occur in essentially freshwater tidal environments. Unlike the floodplain forests found upriver, the hydrology of these ecosystems is driven largely by large macro-tides of 4-8 m coupled with the significant freshwater discharge from the Amazon River.

Litho-climatic characteristics and its control over mangrove soil geochemistry: A macro-scale approach.

Brazil hosts an extensive coastal area, marked by a great diversity of geoenvironments. The present study evaluated the role of geoclimatic factors in the geochemistry of mangrove soils by using wet extractions and several physical and chemical parameters. Soil samples were collected in 11 mangrove forests from NE (n = 94) and SE Brazil (n = 230).

Soil Organic Matter Responses to Mangrove Restoration: A Replanting Experience in Northeast Brazil.

Mangroves are among the most relevant ecosystems in providing ecosystem services because of their capacity to act as sinks for atmospheric carbon. Thus, restoring mangroves is a strategic pathway for mitigating global climate change. Therefore, this study aimed to examine the organic matter dynamics in mangrove soils during restoration processes.

Ecosystem carbon losses following a climate-induced mangrove mortality in Brazil.

Drought events may induce mangrove mortality and dieback events worldwide as a result of climate extremes. As mangroves sequester large quantities of carbon, quantifying the losses of these stocks following climate disturbances may guide wetland governance strategies globally. In Southeast Brazil, we determined the total ecosystem carbon stocks (TECS) of pristine mangroves that were up to 1851 Mg of carbon per hectare (Mg C ha), which are the highest stocks measured from South American and raising estimates of Brazil's mangrove TECS to 0.

Role of Fe dynamic in release of metals at Rio Doce estuary: Unfolding of a mining disaster.

The role of Fe oxyhydroxides dynamic on metal bioavailability was studied in the Rio Doce estuary after the largest mining disaster in the world. Soon after the disaster in 2015, metals were associated with Fe oxyhydroxides under a redox-active estuarine environment. Our results indicate that organic matter inputs from plant colonization on deposited tailings over estuarine soils led to a reductive dissolution of Fe oxyhydroxides within two years.

Manganese: The overlooked contaminant in the world largest mine tailings dam collapse.

Manganese (Mn) is an abundant element in terrestrial and coastal ecosystems and an essential micronutrient in the metabolic processes of plants and animals. Mn is generally not considered a potentially toxic element due to its low content in both soil and water. However, in coastal ecosystems, the Mn dynamic (commonly associated with the Fe cycle) is mostly controlled by redox processes.

From sinks to sources: The role of Fe oxyhydroxide transformations on phosphorus dynamics in estuarine soils.

The availability of phosphorus (P) in estuarine ecosystems is ultimately controlled by the nature of interactions between dissolved P and the soil components (e.g., soil minerals), especially iron (Fe) oxyhydroxides.

Nitrogen mineralization and eutrophication risks in mangroves receiving shrimp farming effluents.

Nitrogen (N) inputs originated from shrimp farming effluents were evaluated for potential changes in the net N mineralization for mangrove soils from Northeastern Brazil. Our study provides notable information and assessment for the potential enhancement of N mineralization in preserved and shrimp-impacted semi-arid mangrove soils of the Jaguaribe River estuary, which is one of the largest shrimp producers of Brazil, using an analytical and daily tidal variation experimental approach. Nitrogen-rich effluents promoted a significant (p value < 0.

Phosphorus enriched effluents increase eutrophication risks for mangrove systems in northeastern Brazil.

Discharge of effluents loaded with phosphorus (P) from anthropogenic activities constitutes serious eutrophication risks in marine and terrestrial ecosystems, including mangroves. Three mangroves in NE-Brazil were studied to evaluate the impact of P-rich-effluents from shrimp farming and domestic sewage, in relation to a control area (natural mangrove). Soil phosphorus fractionation and water chemical analysis were performed to assess potential pollution.

Does food partitioning vary in leaf-eating crabs in response to source quality?

Mangroves have a relevant ecosystem function due to their efficiency in blue carbon sequestration. Autotrophic carbon conservation in mangroves remains controversial. In this sense, autotrophic nutrient assimilation by crabs can highlight their ecosystem function.

Risk assessment and copper geochemistry of an orchard irrigated with mine water: a case study in the semiarid region of Brazil.

This study aimed to evaluate mine water reuse, elucidating the potential problems related to trace metal biogeochemistry focusing on Cu dynamics in water, soil, and plants. Water samples were collected from a Cu mine and a reservoir used to store mine water. Additional samples were taken from soils from an uncultivated area and a banana orchard (irrigated with mine water for at least 10 years) and plant from the irrigated area.

Shrimp ponds lead to massive loss of soil carbon and greenhouse gas emissions in northeastern Brazilian mangroves.

Mangroves of the semiarid Caatinga region of northeastern Brazil are being rapidly converted to shrimp pond aquaculture. To determine ecosystem carbon stocks and potential greenhouse gas emissions from this widespread land use, we measured carbon stocks of eight mangrove forests and three shrimp ponds in the Acaraú and Jaguaribe watersheds in Ceará state, Brazil. The shrimp ponds were paired with adjacent intact mangroves to ascertain carbon losses and potential emissions from land conversion.

The Samarco mine tailing disaster: A possible time-bomb for heavy metals contamination?

In November 2015, the largest socio-environmental disaster in the history of Brazil occurred when approximately 50 million m of mine tailings were released into the Doce River (SE Brazil), during the greatest failure of a tailings dam worldwide. The mine tailings passed through the Doce River basin, reaching the ecologically important estuary 17 days later. On the arrival of the mine wastes to the coastal area, contamination levels in the estuarine soils were measured to determine the baseline level of contamination and to enable an environmental risk assessment.

Are acid volatile sulfides (AVS) important trace metals sinks in semi-arid mangroves?

Acid-volatile sulfides (AVS) formation and its role on trace metals bioavailability were studied in semi-arid mangroves. The semi-arid climatic conditions at the studied sites, marked by low rainfall and high evapotranspiration rates, clearly limited the AVS formation (AVS contents varied from 0.10 to 2.

High Primary Production Contrasts with Intense Carbon Emission in a Eutrophic Tropical Reservoir.

Recent studies from temperate lakes indicate that eutrophic systems tend to emit less carbon dioxide (CO2) and bury more organic carbon (OC) than oligotrophic ones, rendering them CO2 sinks in some cases. However, the scarcity of data from tropical systems is critical for a complete understanding of the interplay between eutrophication and aquatic carbon (C) fluxes in warm waters. We test the hypothesis that a warm eutrophic system is a source of both CO2 and CH4 to the atmosphere, and that atmospheric emissions are larger than the burial of OC in sediments.