Avaliação dos teores de carbono em sedimento de pradarias marinhas da espécie Halodule wrightii no banco dos cajuais, Icapuí - CE

Abstract

The intensification of greenhouse gas (GHG) emissions due to human activities is the main cause of current climate change, with the potential to increase global temperatures by 1.5oC, according to the Intergovernmental Panel on Climate Change (IPCC). Currently, the development of nature-based solutions for climate mitigation seeks to reverse these effects with little risk. Monitoring blue carbon ecosystems, such as, mangroves, seagrass beds and tidal flats, which are capable of storing carbon, is a potential tool for assessing the sequestration of atmospheric CO2. Coastal wetland ecosystems play a significant role in the accumulation of blue carbon, with the capacity to be converted into organic carbon and deposited in sediment. The aim of this study was to evaluate the levels of total organic carbon and total nitrogen in a marine prairie bank located in Icapuí, Ceará. Sediment samples of approximately 30cm were collected at three stations (E1, E2 and E3), a total of 28 sub-samples. The carbon content of the angiosperm bank was quantified using three methods: the gravimetric method, the chemical method (Walkley and Black) and elemental analysis. The three methods were compared and the best estimate was observed between the three methodologies, with a significant positive correlation between the Walkley and Black and Elemental methods (r = 0.837), and between the Gravimetric and Elemental methods (ρ = 0.877). Linear relationships were therefore drawn up between the elemental and gravimetric methods, obtaining a correction factor. Organic carbon measured by the elemental method showed average concentrations of 1.82 ± 0.38 % in E1, 2.31 ± 0.45 % in E2 and 1.59 ± 0.56 % in E3, with significant spatial variation between the stations, and with values close to those found in the literature. The average value of nitrogen in the sediment was 0.22 ± 0.19 %, 0.37 ± 0.07 and 0.14 ± 0.16 at stations E1, E2 and E3 respectively and, through the C:N ratio, it was identified that the origin of the organic matter deposited in the prairie sediments was predominantly aquagenic. Thus, this work contributes to understanding the role of a blue carbon ecosystem in mitigating climate change through soil carbon storage. In addition, it highlights the importance of monitoring blue carbon ecosystems in the context of carbon retention and possible mitigation of atmospheric CO2.