Extreme weather impacts on tropical mangrove forests in the Eastern Brazil Marine Ecoregion

Limnology & Oceanography

Sanders

Bissoli

et al. 2020

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.

Section: Discussionmentioning

confidence: 99%

Land use impacts on benthic bioturbation potential and carbon burial in Brazilian mangrove ecosystems

Limnology & Oceanography

Sanders

Bissoli

et al. 2020

“…Despite the importance of mangroves as carbon sinks and the ecological services they provide (Costanza et al., ; UNEP, ), they are vulnerable to loss through coastal development, pollution, and climate change (Pendleton et al., ; Servino, Gomes, & Bernardino, ). Brazil is no exception.…”

Section: Introductionmentioning

confidence: 99%

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

Kauffman

Ferreira

et al. 2018

Ecology and Evolution

103

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 mean total ecosystem carbon stock of mangroves in this semiarid tropical landscape was 413 ± 94 Mg C/ha. There were highly significant differences in the ecosystem carbon stocks between the two sampled estuaries suggesting caution when extrapolating carbon stock across different estuaries even in the same landscape. Conversion of mangroves to shrimp ponds resulted in losses of 58%–82% of the ecosystem carbon stocks. The mean potential emissions arising from mangrove conversion to shrimp ponds was 1,390 Mg CO2e/ha. Carbon losses were largely from soils which accounted for 81% of the total emission. Losses from soils >100 cm in depth accounted for 33% of the total ecosystem carbon loss. Soil carbon losses from shrimp pond conversion are equivalent to about 182 years of soil carbon accumulation. Losses from mangrove conversion are about 10‐fold greater than emissions from conversion of upland tropical dry forest in the Brazilian Caatinga underscoring the potential value for their inclusion in climate change mitigation activities.

“…The Eastern Brazil Marine Ecoregion is experiencing loss of mangrove forests and multiple other impacts to estuaries ( Barros et al, 2012 ; Bernardino et al, 2015 ; Gomes et al, 2017 ; Bernardino et al, 2018 ; Servino, Gomes & Bernardino, 2018 ). As in other estuarine ecosystems, macrofaunal assemblages are highly variable with respect to taxa composition and abundance.…”

Section: Discussionmentioning

confidence: 99%

“…1 ). The northernmost estuary, Piraquê-Açu-Mirim estuary (PAE; 19°57′S 40°09′W) is within a municipal conservation unit and covered by extensive and well-developed mangrove forests with an area of over 19 km 2 ( Bernardino et al, 2018 ; Servino, Gomes & Bernardino, 2018 ). The Vitória Bay estuarine system (VIB; 20°16′S 40°20′W) is the largest estuary in the region with approximately 18 km 2 of mangrove forests and surrounded by a densely populated metropolitan area with high levels of sewage input and industrial activities ( Jesus et al, 2004 ).…”

Section: Methodsmentioning

confidence: 99%

Benthic macrofaunal structure and secondary production in tropical estuaries on the Eastern Marine Ecoregion of Brazil

Bissoli

2018

PeerJ

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.