Carbon and nitrogen stable isotope compositions of organic matter in marine sediment cores from the Abrolhos region: indicators of sources and preservation

Abstract

Organic matter is an important source of information on the transport and consolidation processes of sediments. In this study, the isotopes of carbon and nitrogen (δ 13 C and δ 15 N), total organic carbon (TOC), total nitrogen, carbon/nitrogen (C/N) ratio, and 13 C-NMR were utilized to understand the origin and behavior of organic material in the Abrolhos region. It were analyzed nine sediment cores taken from a mangrove, a channel between the mainland and the coral reefs. The average value of the C/N ratio in the mangrove was 18, which characterizes purely terrigenous areas. For the reefs, the average value of the C/N ratio was 8,which is characteristic of marine and coastal regions. For the sediment cores taken from the channel, the average value of the C/N ratio was 10, a typical value of areas under the influence of mangroves. The mean values of δ 13 C were -26.9‰ for the mangrove, -20.7‰ for the channel region, and -18.2‰ for the reefs. This variation is associated with the main source of organic matter, which in the mangrove is derived from vascular plants (mainly C3 metabolism) and for the reefs is derived from phytoplankton. The 13 C-NMR results corroborate the isotopic and elemental analyses. The analyses of these cores indicate that the anthropogenic influence on the coast did not significantly alter the composition of the material that has been deposited in about the last 80 years in the region of study.

Is the Kornati National Park Still an Acceptable Reference Area for Environmental Studies?

“…The δ 13 C values of organisms' tissues usually indicate the source of C rather than specifying the trophic levels [6,8]. The δ 13 C values measured in the H. trunculus varied significantly between different locations, from −19.15 to −14.47 , and are comparable with those reported in some other studies.…”

“…Organic matter produced in the marine environments is degraded (re-mineralized) and only partially stored in the marine sediment as sedimentary organic matter. In the coastal areas, the biggest contributor to the sedimentary organic C (C org ) is phytoplankton along with terrestrial organic debris, as a consequence of human interference [6].…”

“…Stable isotope compositions of organisms are used to identify the biochemical processes and sources of the pollution, as they are mainly influenced by the isotopic ratios of diet, metabolic pathways, and fractionating processes [4,5]. With the isotopic analysis, it is also possible to determine the source of sedimentary organic matter (marine, terrestrial) and thus to assess the anthropogenic impacts on the observed area [6].…”

Geochemical Equilibrium and Processes in Seawater

“…Stable isotope compositions of organisms are used to identify the biochemical processes and sources of the pollution, as they are mainly influenced by the isotopic ratios of their diet, metabolic pathways, and fractionating processes [18,19]. With isotopic analysis, it is also possible to determine the source of sedimentary organic matter (marine, terrestrial) and assess the anthropogenic impacts on the observed area [20].…”

Variabilidade sedimentológica e geoquímica em um sistema estuarino tropical sob forte influência antrópica (Rio Capibaribe-PE)

“…O carbono e o nitrogênio elementares são frequentemente utilizados na identificação destas fontes sedimentares, na determinação de processos biológicos, estimativa de taxas de acumulação de diferentes elementos em várias matrizes, determinação de inputs proporcionais, criação e avaliação de modelos (Sulzman, 2008;Portela, 2013). A razão Carbono/Nitrogênio (C/N) é empregada como um parâmetro na avaliação da influência relativa da matéria orgânica marinha e terrestre, indicando qual a fonte predominante de matéria orgânica para o ecossistema costeiro (Meyers & Ishiwatari, 1993;Meyers, 1994;Guo et al, 2004;Usui et al, 2006;Souza et al, 2013).…”