Abstract
This study aimed to identify potential sources of organic matter in sediment, using stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N). Sediment samples were gathered from the margin and in center of three subsystems: Ivinheima, Parana and Baia, in August/2001. The samples were fractionated granulometrically and separated by size ( 70 μm), prepared and sent to CENA / USP, for identifying the isotopes proportions. Significant differences were detected in the isotopic ratios of the sediment only between sampling stations. The Baia channel presented the lowest δ 13 C values, while the highest ones were recorded in Parana river. At this last, δ 15 N values were negative (-14.41‰). We did not verify significant difference in isotopic composition between the particle sizes of sediment, and between the sampling points. The main sources of carbon for the sediment were C3 macrophytes, periphyton and particulate organic carbon (POC). 13 C, δ 15 N.
Highlights
In floodplains, the matter and energy cycles involve the combination of the contributions of allochthonous and autochthonous sources that are dependent on the flood pulses (JUNK et al, 1997; MARSHALL et al, 2008)
Detritus is among the most important food sources for the food chain from tropical floodplains (WELCOMME, 1985), and one of the main link for organic matter cycling in freshwater ecosystems (WETZEL, 1975)
On the Paraná river floodplain, significant differences were observed between the carbon isotopic composition (δ13C) in the sediment samples from the sampling stations (ANOVA; p = 0.049)
Summary
The matter and energy cycles involve the combination of the contributions of allochthonous and autochthonous sources that are dependent on the flood pulses (JUNK et al, 1997; MARSHALL et al, 2008). Detritus is among the most important food sources for the food chain from tropical floodplains (WELCOMME, 1985), and one of the main link for organic matter cycling in freshwater ecosystems (WETZEL, 1975). Biological Sciences define non-living particulate material in aquatic ecosystems that comes from any trophic level, including allochthonous sources (WETZEL, 1975). It is defined as a mixture of particulate organic matter (dead and living particles such as algae, fungi and bacteria), which is often called detrital aggregate (BOWEN, 1982; MANN, 1988). Fish are important users of this resource and create indispensable links in the food chain, as they make the resources contained in the sediment available to piscivorous species (LOPES et al, 2009)
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