Carbon and alkalinity outwelling across the <scp>groundwater‐creek‐shelf</scp> continuum off Amazonian mangroves

Cabral, Alex; Dittmar, Thorsten; Call, Mitchell; Scholten, Jan; Rezende, Carlos Eduardo de; Nils, E.; Gledhill, Martha; Seidel, Michael; Santos, Isaac R.

doi:10.1002/lol2.10210

Cited by 34 publications

(23 citation statements)

References 52 publications

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“…Overall, several of Brazil's northern and northeastern states, where >80% of the country's mangroves are present, lack data; seven and nine states out of the 16 mangrove states in Brazil still lack data on soil organic carbon stocks and sequestration rates, respectively (Supplementary Table 1). It should also be noted that, while this study focused on carbon stocks and long-term carbon sequestration rates in biomass and soils, real time air-sea CO 2 fluxes, and DOC (dissolved organic carbon), DIC (dissolved inorganic carbon), and alkalinity (bicarbonate) export are important mechanisms of the carbon cycling in mangroves (e.g., Sippo et al, 2016;Carvalho et al, 2017;Cotovicz et al, 2019;Cabral et al, 2021) and should be taken into account to better constrain carbon budgets for Brazilian mangroves.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

Rovai

Twilley

Worthington

et al. 2022

Front. For. Glob. Change

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Mangroves are known for large carbon stocks and high sequestration rates in biomass and soils, making these intertidal wetlands a cost-effective strategy for some nations to compensate for a portion of their carbon dioxide (CO2) emissions. However, few countries have the national-level inventories required to support the inclusion of mangroves into national carbon credit markets. This is the case for Brazil, home of the second largest mangrove area in the world but lacking an integrated mangrove carbon inventory that captures the diversity of coastline types and climatic zones in which mangroves are present. Here we reviewed published datasets to derive the first integrated assessment of carbon stocks, carbon sequestration rates and potential CO2eq emissions across Brazilian mangroves. We found that Brazilian mangroves hold 8.5% of the global mangrove carbon stocks (biomass and soils combined). When compared to other Brazilian vegetated biomes, mangroves store up to 4.3 times more carbon in the top meter of soil and are second in biomass carbon stocks only to the Amazon forest. Moreover, organic carbon sequestration rates in Brazilian mangroves soils are 15–30% higher than recent global estimates; and integrated over the country’s area, they account for 13.5% of the carbon buried in world’s mangroves annually. Carbon sequestration in Brazilian mangroves woody biomass is 10% of carbon accumulation in mangrove woody biomass globally. Our study identifies Brazilian mangroves as a major global blue carbon hotspot and suggest that their loss could potentially release substantial amounts of CO2. This research provides a robust baseline for the consideration of mangroves into strategies to meet Brazil’s intended Nationally Determined Contributions.

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Section: Conclusion and Recommendationsmentioning

confidence: 99%

Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

Rovai

Twilley

Worthington

et al. 2022

Front. For. Glob. Change

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“…Although more pronounced in open oceanic surface waters, estuarine, and coastal waters may suffer acidification by the deregulation of the biological CO 2 pump. Mangroves export a significant proportion of their primary productivity as dissolved inorganic carbon (DIC) and alkalinity, and this locally increases coastal waters pH (Sippo et al, 2016;Cabral et al, 2021). In addition, net sulfate reduction or burial of reduced Sulfur compounds (mostly pyrite) also contribute significantly to the total alkalinity export (Hu and Cai, 2011).…”

Section: A Summary Of Observed Responses Of Mangroves To Climate Chan...mentioning

confidence: 99%

Mangrove Trace Metal Biogeochemistry Response to Global Climate Change

Lacerda¹,

Ward²,

Borges³

et al. 2022

Front. For. Glob. Change

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This review discusses observed impacts from different climate change-driven pressures on mangrove's role in modulating trace metal transfer at the land-ocean interface. It contributes to the literature in a global context and shows mangroves as mitigators or providing positive feedback to metal mobilization. Most chalcophile metals2+ accumulate in mangrove soils associated with sulfides while high sedimentation rates avoid their oxidation. Exudation of oxygen by roots fixates Fe, which co-precipitates metals as oxyhydroxides in the rhizosphere. These two biogeochemical processes reduce trace metal availability to plants and their mobility within estuaries. However, climate change-driven pressures alter this geochemical equilibrium. Increasing atmospheric CO2 and temperature, and the intensity and frequency of extreme climatic events, have proved to affect mangrove functioning and cover, but no direct observation on the impact on metal biogeochemistry is presently available, whereas sea level rise and saline intrusion impacts on the fate of metals have already been observed. Sea level rise increases erosion, that dissociates deposited sulfides releasing metals to the water column. Released metals adsorb onto suspended particles and can re-deposit in the estuary or are exported to continental shelf sediments. Saline intrusion may oxidize deeper sediment layers releasing metals to porewaters. Part of the mobilized metals may remain in solution complexed with DOM and have their bioavailability increased, as shown by high bioaccumulation factors and biomagnification and high metal concentrations in the estuarine biota, which results in higher human exposure through fisheries consumption. Since erosion occurs preferentially at the sea border and higher sedimentation at the higher reaches of the estuary, triggering mangroves migration landward, spatial gradients are formed, and shall be taken into consideration when planning mitigation or adaptation strategies. These observations suggest disruption of traditional humans dwelling in mangrove dominated coastlines by increasing contamination of coastal fisheries, often the principal protein source for those groups and an important source of income. Further research into the environmental and socioeconomic impacts of climate change driven alterations to metal biogeochemical processes in mangroves as contaminant levels are expected to increase.

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“…The northern and northeastern continental shelves of Brazil present widespread coral reef coverage (Leão et al, 2016;Soares et al, 2017;Soares et al, 2019) and the outwelling of carbon and alkalinity counteracting coastal acidification could be particularly relevant in shallow-water coral assemblages along the southwestern Atlantic coast (Cotovicz Jr. et al, 2020). However, estimates of carbon outwelling along the land-ocean continuum in Brazil (and elsewhere) are scarce (Cabral et al, 2021) and remain spatially and temporally limited. Therefore, it is important to calculate the outwelling from BCEs to correctly provide the actual sequestration capacities of BCEs, which may currently be underestimated.…”

Section: Mangrove Forestsmentioning

confidence: 99%

Blue Carbon Ecosystems in Brazil: Overview and an Urgent Call for Conservation and Restoration

et al. 2022

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In this article, we discuss knowledge and gaps regarding blue carbon ecosystems (BCEs) in Brazil, considering the urgency to apply protection actions and policies to safeguard their biodiversity and associated ecosystem services. We also indicate areas of further research to improve carbon stocks and sequestration rate estimates. We call attention to the shortage of studies on Brazilian BCEs relative to the growing knowledge on the Blue Carbon Framework accumulated worldwide over the last decade. Considering the extensive Brazilian Economic Exclusive Zone (known as “Blue Amazon”), knowledge concerning blue carbon stocks is vital at regional and global scales for mitigating global increases in atmospheric carbon dioxide (CO2). The Blue Amazon has at least 1,100,000 ha of vegetated and non-vegetated coastal ecosystems (mangroves, salt marshes, seagrass meadows, and hypersaline tidal flats) that collectively contain vast amounts of stored carbon, making Brazil an ideal place to test mechanisms for evaluating, conserving, and restoring BCEs. Other poorly understood potential sinks and sources of carbon are macroalgal and rhodolith beds, mudflats, continental shelf sediments, and marine animal forests in shallow, mesophotic, and deep waters. The carbon fluxes between diverse environmental compartments, such as soil–air, soil–water, groundwater–water–surface water, air–water, and land–ocean, in BCEs across the Blue Amazon must be studied. We emphasize the importance of assessing the total carbon stock and the recent dismantling of environmental laws that pose great risks to these important BCEs. The conservation and recovery of these areas would enhance the carbon sequestration capacity of the entire country. Furthermore, we highlight priorities to improve knowledge concerning BCEs and their biogeochemical cycles in the Blue Amazon and to provide information to assist in the reduction of atmospheric levels of CO2 for the United Nations Decade of Ocean Science (2021–2030).

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Carbon and alkalinity outwelling across the groundwater‐creek‐shelf continuum off Amazonian mangroves

Cited by 34 publications

References 52 publications

Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

Mangrove Trace Metal Biogeochemistry Response to Global Climate Change

Blue Carbon Ecosystems in Brazil: Overview and an Urgent Call for Conservation and Restoration

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