CONTRIBUIÇÃO DA DECOMPOSIÇÃO DE MACRÓFITAS AQUÁTICAS (Eichhornia azurea) NA MATÉRIA ORGÂNICA DISSOLVIDA

Abstract

A matéria orgânica nos ambientes aquáticos exerce papel fundamental em diversos processos ecológicos sendo a decomposição uma das principais rotas de ciclagem da matéria. A contribuição das macrófi tas aquáticas se dá principalmente pela produção de detritos, já que seu carbono é de difícil assimilação direta pela maioria dos organismos. As análises espectroscópicas tem se constituído numa ferramenta importante no estudo da matéria orgânica, pois permitem uma distinção razoável entre materiais lábeis e refratários. A partir da comparação dos espectros de fl uorescência da matéria orgânica resultante de um experimento de decomposição de macrófi tas aquáticas e da matéria orgânica da água, do sedimento e do solo de ambientes da planície de inundação do alto rio Paraná, estimou-se a contribuição das macrófi tas para o reservatório de carbono nesses ambientes. Foi possível verifi car maior contribuição da decomposição nos ambientes oligotrófi cos conectados ao rio Paraná, enquanto que nos ambientes conectados aos rios Ivinheima e Baia predominam matéria orgânica alóctone, principalmente substâncias húmicas pedogênicas. Palavras-chave: Macrófi tas aquáticas, fl uorescência, decomposição, planície do rio Paraná ABSTRACT CONTRIBUTION TO DISSOLVED ORGANIC MATTER BY DECOMPOSITION OF AQUATIC MACROPHYTES, Eichhornia azurea. Organic matter plays a fundamental role in many ecological processes and decomposition is among the main cycling routes of organic matter. The decomposition of aquatic macrophytes generates much debris, since the carbon of these algae is not easily assimilated by other organisms. Spectroscopic analyses are important in organic matter studies, because it enables satisfactory distinction between labile and refractory materials can be obtained. Through comparing the fl uorescence spectrum of the organic debris generated by a decomposing macrophyte with those of water, sediment, and soil samples from the Upper Paraná River fl oodplain water bodies, we were able to estimate the contribution of decomposition to local carbon cycles. The results revealed a higher contribution of decomposition to the oligotrophic environments connected with the Paraná River, while some water bodies connected with the rivers Ivinheima and Baia showed a greater participation of allochthonous organic matter, mainly derived from humus.

Implication of anaerobic and aerobic decomposition of Eichhornia azurea (Sw.) Kunth. on the carbon cycling in a subtropical reservoir

“…The null coefficient for DOC mineralization resulted from a possible conversion of soluble compounds into humic substances with a refractory nature. Azevedo et al (2008) observed an increased humification degree in DOM after the 60 th day of decomposition of E. azurea. Humic substances from anaerobic decomposition of E. azurea showed the maximum production of humic and fulvic acids on the first month of incubation (Bitar, 2003).…”

Decomposition Dynamics ofTypha angustifoliaunder Aerobic Conditions

“…A previous study 28,29 on aquatic macrophytes demonstrated that there were high amounts of dissolved oxygen and a high pH during the decomposition period, most likely due to atmospheric diffusion and the consumption/degradation of organic acids produced at the beginning of the decomposition process. Humic substances can complex with orthophosphate in the presence of Fe III at low pH levels, though the mechanisms are not well known.…”

“…The increase in the available phosphorus (orthophosphate) concentration during humification can indicate the presence of high pH and dissolved oxygen, decreasing the assimilation of orthophosphate. 29,30 Therefore, we can presume that the increase in phosphorus at 60 days was most likely due to large amounts of dissolved oxygen and a high pH, which prevented interactions between the humic substances, Fe III , and phosphorus. The predominance of orthophosphate observed during the initial degradation period (Figure 2) was in accordance with the observations reported by Cheesman et al 10 The orthophosphate released to the water column during leaching can be incorporated into organic matter during the catabolism period, as observed by the increase of phosphomonoesters between days 30 and 60 (Table 1).…”

Colonization by Chironomidae Larvae in Decomposition Leaves ofEichhornia azureain a Lentic System in Southeastern Brazil

“…Aquatic plants play a fundamental role in various ecological processes, with the decomposition of their biomass being one of the main routes for cycling organic matter (Azevedo et al 2008). Additionally, macrophytes are important sources of litter (Pieczyfiska 1986), utilized as food and shelter by aquatic invertebrates (Gonçalves et al 2000).…”