Fig 1.
Map of the sampling locations in each basin study system.
(i.e. a = Amazon floodplain; b = Araguaia floodplain; c = Pantanal floodplain; d = Paraná floodplain). Each point in the map represents a lake where carbon sources were sampled and limnological parameters were quantified. AM = Amazon; AR = Araguaia; PA = Pantanal; PR = Paraná. This figure is similar but not identical to the original image (i.e. in Arrieira et al. [56]), and is therefore for illustrative purposes only.
Table 1.
Mean (±standard deviation) of limnological parameters for each basin.
TN = Total Nitrogen; TP = Total Phosphorous; Turb = Turbidity; Cond = Conductivity. The number of sample sites for each basin are in parentheses.
Fig 2.
Principle coordinates analysis biplot of limnological conditions among sampling locations and basins.
The first two axes explain 59% of the variation among sites (i.e. PC1 explained 36% and 23% was explained by PC2). AM = Amazon; AR = Araguaia; PA = Pantanal; PR = Paraná.
Table 2.
Mean (‰) and standard deviation (±SD) of carbon and nitrogen isotope values for each carbon source, and ANOVA results for the test of differences among basins.
PR = Paraná; PA = Pantanal; AR = Araguaia; AM = Amazon; n = number of samples for each source in each basin. Shared superscript lowercase letters indicate lack of significant differences for the Tukey post-hoc test.
Table 3.
Pearson correlation coefficients between stable isotope values (δ13C or δ15N) and environmental variables for each source.
Significant values are in bold with level of significance denoted using asterisks (* p<0.05; ** p<0.01; *** p<0.001). Turb = Turbitity, Cond = Conductivity, TN = Total Nitrogen, TP = Total Phosphorous.
Fig 3.
Regression trees predicting δ13C for each carbon source.
Splits are identified by boxes on branches with the corresponding parameter and value, and terminal nodes are identified by boxes including the mean value for the response variable (i.e. δ13C) as well as the number of samples and sampling locations included in the node. Plus and minus signs or basin abbreviations designate the level of parameter to the left or right of a split (e.g. pH less than or greater than 6.09 for the first split for periphyton).
Fig 4.
Regression trees predicting δ15N for each carbon source.
Splits are identified by boxes on branches with the corresponding parameter and value, and terminal nodes are identified by boxes including the mean value for the response variable (i.e. δ15N) as well as the number of samples and sampling locations included in the node. Plus and minus signs or basin abbreviations designate the level of parameter to the left or right of a split (e.g. TP less than or greater than 59.65 for the first split for riparian vegetation).