Decomposition process of organic matter derived from freshwater phytoplankton

Abstract

We investigated the biodegradation process of freshwater phytoplanktonic organic matter using incubation experiments, with special reference to changes in three major biomolecules: neutral aldoses, amino acids and fatty acids. The concentration of neutral aldoses decreased drastically relative to amino acids and fatty acids during the early decomposition phase (days 0-7), owing largely to the rapid decomposition of storage carbohydrate. This resulted in a temporary decrease in the C/N ratio of organic matter. During the late phase (days 7-60), however, the rate of decrease in neutral aldoses slowed, while the considerable decrease in amino acids and fatty acids continued. The inconspicuous change in amino acid composition was probably due to the fact that no protein and/or peptide is composed of a limited species of amino acid. Although the compositional variety of organic matter among the phytoplankton was clearly observed at the start of decomposition, it became obscure in the course of 60 days. This indicates that while the organic composition of the labile fraction of phytoplanktonic organic matter varies depending on the phytoplankton groups, the refractory fraction has similar composition. The addition of bacterial organic matter is likely another reason for the similar composition of the remaining organic matter at day 60.

Phytoplankton relationship with bacterioplankton, dissolved carbohydrates and water characteristics in a subtropical coastal lagoon

“…Additionally, the decomposition rates of different carbohydrate components are also an important parameter in such a discussion. Several authors have demonstrated that glucose, mannose and xylose, the main carbohydrate components in Merin lagoon in this period, could be quickly degraded, decreasing the residence time of these components during intense heterotrophic bacterial metabolism (Giroldo et al, 2003(Giroldo et al, , 2005bHanamachi et al, 2008).…”

“…Extracellular polysaccharides production by phytoplankton depends on the species, their physiological state and environmental conditions (Urbani et al, 2005;Hanamachi et al, 2008). As a consequence, this process promotes qualitative and quantitative variations in the dissolved organic carbon (DOC) pool in the planktonic environment depending on the abundant species of primary producers and heterotrophic organisms (DellamanoOliveira et al, 2007).…”

Seasonal changes in optical properties of two contrasting tropical freshwater systems

“…DOM represents a complex of compounds and derives from main sources: allochthonous material produced from degradation of humic substances coming from runoff of terrestrial origin (Kieber et al, 2006;Miller et al, 2009); and autochthonous material, produced by autotrophic and heterotrophic in situ activities, but mainly by the bacterial degradation of phytoplankton and macrophytes (Kritzberg et al, 2004;Hanamachi et al, 2008;Henderson et al, 2008;Guillenette and Del Giorgio, 2012). The two different sources of DOM can be distinguished from differences in their optical and chemical characteristics.…”

Emissions of methane and carbon dioxide during anaerobic decomposition of aquatic macrophytes from a tropical lagoon (São Paulo, Brazil)

“…The cytoplasm and the exudates of these plants comprise the main source of labile organic carbon (Peret and Bianchini Jr., 2004;Hanamachi et al, 2008). The supporting tissues of macrophytes are a significant source of refractory carbon (i.e.…”