Impactos Da Mudança De Vegetação Local No Aporte De Matéria Orgânica Para Um Estuário Tropical Preservado (Estuário Do Rio Itapicuru – Ba)

Abstract

IMPACTS OF LOCAL VEGETATION CHANGES IN THE ORGANIC MATTERS INPUT FOR A PRESERVED TROPICAL ESTUARY (ITAPICURU-BA RIVER ESTUARY). Estuaries are major areas of organic matter (OM) deposition, playing an important role in the global carbon cycle. The Itapicuru's river estuary (IRE) is in the North Coast of Bahia (Brazil), in an Environmental Protected Area. Although it presents preserved conditions, some environmental changes caused by human activities can be observed. This study evaluated the anthropogenic impacts importance in concentrations/sources of OM deposited in IRE. n-Alkanes and stable isotopes (δ 13 C and δ 15 N) were analyzed in a sediment core collected in the studied region. Total n-alkanes (n-C 15 to n-C 35), TOC and TN concentrations varied from 1,333 to 7,384 ng g-1 , 0.65% to 2.51% and 0.07% to 0.13%, respectively. Values of δ 13 C and δ 15 N ranged from-28.8‰ to-24.3‰,-6.23‰ to 1.87‰, respectively. By the means of the isotopic composition and the selected n-alkanes diagnostic ratios values (Productivity aquatic index; Carbon Preference Index; Average Chain Length and Alkane index), the main OM sources for IRE were determined as C 3 terrestrial plants. This area is covered by mangrove/riparian vegetation, which mainly species have this photosynthetic pathway. Temporal changes in deposited OM occurred due natural and anthropogenic processes, such urban growth in the IRE upstream region.

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“…Despite anthropic threats to the environment (upstream river pollution, deforestation, real estate speculation, etc. ), the mangroves in the estuary are still well preserved (Guimarães et al 2019), due to the relatively small scale of activities such as fishing and tourism, the fact that part of the fishing techniques used are artisanal and more sustainable, and the large amount of water circulating in it. The conservation condition of the estuarine environments is also indicated by the abundant presence of species sensitive to environmental impacts, such as the top predator rufous crab-hawk (Buteogallus aequinoctialis), locally known as "gacici," a near threatened species (BirdLife International 2018).…”

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“…The region where the communities live is characterized by the presence of well-preserved mangroves (Guimarães et al 2019) and thicket-like shrub forests growing on sand dunes (known as restingas), as well as beach vegetation and anthropic environments, such as coconut plantations and pastures (Tng et al 2021). This plurality of ecosystems, in which fishing communities carry out different practices for obtaining resources, is also home to a number of endangered species, such as the capuchin monkey (Sapajus xanthosternos) and the greybreasted parakeet (Pyrrhura griseipectus), recently reported in the region by the Project team (Félix et al 2022).…”

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