Formation and mineralization kinetics of dissolved humic substances from aquatic macrophytes decomposition

Author(s)

de Almeida Assuncao, Argos Willian ^[1] ; Souza, Brayan Petrick ^[1] ; da Cunha-Santino, Marcela Bianchessi ^{[1, 2]} ; Bianchini, Jr., Irineu ^{[1, 2]}

Affiliation

^[1] Univ Fed Sao Carlos UFSCar, Programa Posgrad Ecol & Recursos Nat, Rodovia Washington Luis, Km 235-SP-310, BR-13565905 Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos UFSCar, Dept Hidrobiol, Rodovia Washington Luis, Km 235-SP-310, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Journal of Soils and Sediments; v. 18, n. 4, p. 1252-1264, APR 2018.
• Web of Science Citations: 5

Abstract

Aquatic macrophytes are an important source of autochthonous dissolved organic carbon in aquatic ecosystems. Yield and mass loss of aquatic humic substances released from macrophytes decomposition could be affected by the plant species and oxygen availability. Our aim was to describe the kinetics of dissolved fulvic and humic acids formed from decomposition of four aquatic macrophytes under aerobic and anaerobic conditions. Samples of Eichhornia azurea (Sw.) Kunth, Egeria najas Planch, Oxycaryum cubense (Poepp. and Kunth), and Salvinia molesta (Mitchell) were incubated under aerobic and anaerobic conditions. On sampling days, the remaining particulate detritus were weighted and were measured for the pH, the electrical conductivity, and the organic carbon in the dissolved fraction. Humic substances were extracted from the dissolved fraction, separated into fulvic and humic acids, and then quantified. The mass loss of particulate and dissolved fractions were fitted to first order kinetic models. Aerobic environment favored mineralization of aquatic macrophyte detritus and humification of organic dissolved carbon. Incubations under aerobic conditions formed 3.6 times more humic acid than incubations under anaerobic conditions. However, incubations in an anaerobic environment formed 1.84 times more fulvic acid. The dissolved humic compounds presented low mineralization rates probably due to the presence of the macrophyte detritus in the incubation representing a more attractive source of resource for microorganisms. In many cases, the mineralization of HS was not noticed, leading to an increase in humic and fulvic acid concentration in the water. O. cubense detritus presented the highest carbon concentration, were related to refractory features, and generated the highest amounts of dissolved HA (mainly under aerobic condition). Egeria najas detritus presented the lowest carbon concentration, were related to labile features, and generated the highest amounts of dissolved FA (mainly under anaerobic condition). Besides that, high humic substance concentrations in the dissolved organic carbon were related to low mineralization of this fraction. (AU)

• FAPESP's process: 11/10178-6 - Kinetics and molecular variations of humic compounds formed from the decomposition of aquatic macrophytes.
• Grantee: Argos Willian de Almeida Assunção
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 11/16990-4 - Kinetics and molecular variations of humic substances formed from the decomposition of aquatic macrophytes
• Grantee: Irineu Bianchini Júnior
• Support Opportunities: Regular Research Grants