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

Abstract

AIM: Our aim was to identify dissolved organic matter (DOM) main sources in environments of the Upper Paraná River floodplain and their seasonal and spatial variation. METHODS: Ultraviolet-visible and fluorescence spectroscopy were utilized. The samples were obtained from November 2007 to September 2008 in six lakes of the floodplain. RESULTS: DOM quality differs among environments and also between rainy and dry season. The environments connected with Paraná River showed a high variation on the allochthonous/autochthonous proportion. Aquatic macrophytes might represent an important contribution to DOM in Garças and Osmar lakes. CONCLUSIONS: In general, environments connected to Paraná River have a greater influence of autochthonous DOC, while the others are most influenced by allochthonous inputs.

Seasonal changes in optical properties of two contrasting tropical freshwater systems

“…The estimated apparent molecular size (M) is obtained by the ratio of two absorption coefficients (a250:a365), based on the fact that declining ratio indicates increasing of molecular size (De Haan, 1987;Peuravuori and Pihlaja, 1997). In recent decades researchers have used these spectral metrics to investigate the optical properties in temperate aquatic systems (Zhang et al, 2007a(Zhang et al, , 2007b(Zhang et al, , 2009Helms et al, 2008;Bracchini et al, 2010), but studies using this approach in tropical environments are still scarce and little is known to Brazilian aquatic systems (Teixeira et al, 2011(Teixeira et al, , 2013Bittar et al, 2015).…”

Interpretation of total phytoplankton and cyanobacteria fluorescence from cross‐calibrated fluorometers, including sensitivity to turbidity and colored dissolved organic matter

“…Consequently, the CDOM effect can be significant in the final predicted of total Chl a concentration, and algorithms without a CDOM correction can result in false signals of high risk of exposition to cyanobacteria, although the CDOM effect on the cyanobacterial Chl a is one fourth of the effect on total Chl a (Table ). This interference is also particularly relevant for monitoring phytoplankton in some ecosystems like floodplain rivers as the rainfall regime could substantially and rapidly change CDOM concentration (Teixeira et al ). The correction of the CDOM effect is most effective through the use of a fluorescent blank (Cullen and Davis ), which can be easily implemented in the field using syringe filters.…”

Spatial variability of chromophoric dissolved organic matter in a large floodplain river: control factors and relations with phytoplankton during a low water period

“…Fourth, isolation improves phytoplankton growth, which is shown at La3 by high Chl‐ a and low Pheo‐ a :Chl‐ a ratio; the alkaline conditions of the water because of the photosynthetic activity of phytoplankton increase the susceptibility of CDOM to photobleaching (Reche et al ., ). Fifth, isolation increases the production of autochthonous CDOM with low MW because of development of phytoplankton and bacteria (Sundh and Bell, ; Peduzzi et al ., ; Teixeira et al ., , ). Finally, groundwater hydrological connection reduces the input of high‐MW‐CDOM because this fraction is preferentially sorbed and retained by soil particles (Kaiser et al ., ).…”