As Rotas De Liberação Do Carbono Dos Detritos De Macrófitas Aquáticas

Abstract

RESUMONesse estudo discutem-se eventos relativos à liberação do carbono (e.x. CO 2 , CH 4 , COD) durante a decomposição das macrófi tas aquáticas. Foi realizada uma breve compilação para examinar a variação dos teores de carbono dessas plantas. Os processos de mineralização são discutidos em função de fatores controladores dos sistemas aquáticos continentais (ex. temperatura, disponibilidade de oxigênio dissolvido). Propõe-se ainda, um modelo cinético que descreve e compara as velocidades dos processos de mineralização dos diferentes componentes dos detritos. Pelo modelo adotado, concluiu-se que a mineralização possui, no geral, três rotas que envolvem diferentes proporções de carbono. A rota predominante (oxidação dos compostos orgânicos refratários particulados; i.e. fi bras) é a mais lenta (tempo médio de meia vida: 88 dias); as mineralizações dos compostos orgânicos dissolvidos e lábeis envolvem menos carbono (ca. 29,7%) e constituem-se em processos de curto prazo. Palavras-chave: Mineralização, decomposição, modelos matemáticos, COD, COP, detritos. ABSTRACT THE RELEASE PATHWAYS OF CARBON FROM DETRITUS OF AQUATIC MACROPHYTES.Herein, processes linked to the release of the carbon (e.g. CO 2 , CH 4 , DOC) from decomposition of aquatic macrophytes are discussed. A brief compilation of other studies was made to verify the variation of carbon contents in the plant tissues, and carbon mineralization processes were discussed in face of the conditioning factors that usually operate at continental aquatic systems (e.g. temperature, availability of dissolved oxygen). A kinetic model was proposed to describe and compare the rate of mineralization of released detritus. The mineralization generally follows three different pathways, each one involving different amounts of carbon. The predominant pathway -oxidation of particulate refractory organic compounds, like fi bers -is the slowest pathway, with a mean half-time of 88 days. The mineralization of soluble and labile organic compounds seem to involve less carbon (ca. 29.7%), and takes place faster.

Anaerobic decomposition of submerged macrophytes in semiarid aquatic systems under different trophic states, Paraba State, Brazil

“…As they presented slower decomposition rates, the fibers are generally accumulated in limnic sediments, becoming possible precursors of humic compounds (Bianchini and Cunha-Santino, 2008), which allows us to affirm that the refractory fractions of E. densa and C. braunii, could act in the ecosystem metabolism as a possible precursor source in the humic substances genesis, due to the low coefficient of mineralization (k R ). The dissolved carbon presented a refractory potential during E. densa and C. braunii decomposition, with low mineralization coefficients (K 3 ).…”

“…During the biomass decomposition of submerged macrophytes, significant changes can occur in water, that is, increase of dissolved and particulate organic matter, aquatic system acidification, increased electrical conductivity (Bianchini and Cunha-Santino, 2010) and nutrient release (Wang and Fan, 2013). Such physical and chemical changes may be affected either by extrinsic factors like intrinsic ones, such as the species chemical composition (Bianchini and Cunha-Santino, 2008) and the nutrient concentration in the water which can accelerate the organic matter degradation or make it slower (Xie et al, 2004) due to the heterotrophic activity dynamics during the degradation process.…”

Spatial and seasonal distribution of chromophoric dissolved organic matter in the Upper Paraná River floodplain environments ( Brazil)

“…Carbon from aquatic macrophytes and periphyton, for example, can vary in quantity and quality according to the present species (Osborne et al, 2007). The mineralized or humified fractions and the velocity of mineralization and humification can also vary (Bianchini Junior and Cunha-Santino, 2008). Besides different sources, DOM is also influenced by various mechanisms, such as water mixing and photodegradation (Zhang et al, 2011).…”

Bacterioplankton features and its relations with doc characteristics and other limnological variables in Paraná river floodplain environments (PR/MS-Brazil)

“…However, Daniel et al (21) showed that in the absence of recent algal carbon the microbial loop keeps transferring energy to metazooplankton. Regarding the carbon from aquatic macrophytes decomposition, it is estimated that around 24% can be converted to microorganisms’ biomass (10). These pieces of information lead to the importance of carbon quality determining microbial loop role in an ecosystem.…”