Changes in Composition of Particulate and Dissolved Organic Matter in the Negro River Under Different Climate Change Scenarios

The increase in temperature and CO₂ levels can cause changes in natural organic matter (NOM) due to disturbances in both productivity and microbial activity. In the Amazon region, despite the crucial role of aquatic ecosystems as sources and sinks of carbon, NOM remains poorly explored at the molecular level. This study aimed to characterize particulate organic matter (POM) and dissolved organic matter (DOM) fractions using GC-MS and FT-ICR MS, respectively, to assess the effects of a progressive increase in temperature and CO₂ concentration over 28 days. Water from the Negro River (Brazil) was incubated in microcosms simulating climate change scenarios projected by the IPCC: control (ambient temperature and CO₂ levels), mild (+1.5°C and 200 ppm), moderate (+2.5°C and 400 ppm), and drastic (+4.5°C and 850 ppm). During incubation, aliquots of water were taken from the microcosms and subjected to filtration using 0.7 µm glass fiber filter. The particulate fraction underwent liquid-liquid extraction, while the dissolved fraction was subjected to solid-phase extraction (Strata-X, 1 g). The initial results showed various chemical classes in POM samples, particularly n-alkanes, and fatty alcohols and acids, while in the DOM extracts, oxygenated formulae such as O₁-₂₀, NO₁-₂₀, and SO₁-₂₀, were observed. For both POM and DOM fractions, the results revealed that exposure time was a more significant factor in changing composition than temperature and CO₂ concentration, with the most pronounced changes observed after 2 days of incubation.

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Primary Presenter: Giovana Bataglion, Federal University of Amazonas (giovanabataglion@ufam.edu.br)

Authors:

Giovana Bataglion, Federal University of Amazonas  (giovanabataglion@ufam.edu.br)

Helene Lima, Federal University of Amazonas  (helenellima@gmail.com)

Cicero da Silva, Federal University of Amazonas  (cramonfender@gmail.com)

Danielle Franco, Federal University of Goiás  (daniellemitze@ufg.br)

Adalberto Val, National Institute of Amazonian Research  (dalval.inpa@gmail.com)

Boniek Vaz, Federal University of Goiás  (boniek@ufg.br)

Patricia Medeiros, University of Georgia  (medeiros@uga.edu)