Caracterização biogeoquímica da matéria orgânica em um estuário de macromaré localizado na interface Amazônia-semiárido no nordeste do Brasil

Mariana Costa Corrêa, Jefferson Horley Feitosa Serejo, Thiago Pessanha Rangel, Braulio Cherene Vaz de Oliveira, Marcelo Gomes de Almeida, Francisco José da Silva Dias, Carlos Eduardo de Rezende

Abstract


Estuaries are transitional, coastal environments that act as natural filters and areas for the exchange of water and materials, mainly organic matter, which is composed of a significant portion of the transported carbon. Estuaries may import, export or retain dissolved and particulate organic matter. The aim of this study is to understand the composition of the organic matter in the water column of São Marcos Bay Estuarine Complex, a macrotidal environment under influence of semidiurnal tides. To investigate the distribution of organic matter more precisely, the elemental composition was used along with the carbon and nitrogen isotopic composition. The sampling was carried out in August 2016, in 3 transects, with a total of 14 stations. The water was sampled in two different depths, subsurface and bottom. The following parameters were measured: suspended particulate matter, dissolved organic carbon, particulate organic carbon, carbon and nitrogen stable isotopes andthe atomic ratio (C/N)a. The parameters electrical conductivity, dissolved oxygen, and temperature were measured in situ. SPM had a mean of 360.6 (mg L-1) in the medium with a small decrease (mean of 344.6 mg L-1) for the innermost part of the bay. The organic carbon presented higher concentrations in the dissolved mean 10.97 mg L-1 form than the particulate form mean 0.38 mg L-1, varying between the depths and the sampling stations. The total nitrogen concentrations were low and may be related to the low influence of nitrogen compounds. The isotopic signatures and the C/N ratios indicated that mangroves are the most abundant source of particulate and dissolved organic carbon in the study region.


Keywords


Estuarine complex; Geochemical tracers; Stable isotope; Carbon; Nitrogen; São Marcos Bay Estuarine Complex.



DOI: http://dx.doi.org/10.21715/GB2358-2812.2019331107

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