Figure 1.
Hydrological map of the Bolivian part of the Iténez basin.
Sampling locations (black point) and water mercury concentrations (star) are indicated. The principal sampled locations were: 1- San Martín River; 2- Blanco River; 3- Iténez River. (Redrawn from [13]).
Figure 2.
Isotopic signature of sources, invertebrates and fish in three rivers of the Iténez basin (Amazon, Bolivia).
Biplots display mean values (± sd in error bars) of δ13C and δ15N values for sources (A,B,C) POM = Particulate organic matter, Litt = Leaf litter, Peri = Periphyton; C3 = C3 aquatic macrophytes and TVeg = Terrestrial Vegetation; and invertebrates groups (D,E,F): Ephe = Ephemeroptera, Odo = Odonata, Dec = Decapoda, Col = Coleoptera and Gas = Gasteropoda. (G,H,I) represented mean values (± sd in error bars) of δ13C and Trophic Position (derived from δ15N) of fish species: detritivore (1 = Curimatella cf. alburna, 2 = Psectrogaster sp.), herbivore (3 = Schizodon fasciatus), insectivore (4 = Triportheus angulatus) and piscivore (5 = Pseudoplatystoma sp., 6 = Pygocentrus nattereri, 7 = Hoplias malabaricus and 8 = Acestrorhynchus sp.). In biplots (A,B,C), C4 aquatic marcophytes (δ13C : −12.3 to −13.2‰; δ15N : 2 to 2.2‰) were not plotted and δ13C and δ15N values of detritivore (1, 2) and herbivore (3) fish species were reported.
Table 1.
Isotopic composition (δ15N, δ13C) of food sources and invertebrates in three rivers of the Iténez basin.
Table 2.
Standard Length, mercury concentration and isotope signature (δ15N and relative Trophic Position - TP, δ13C) of eight fish species populations sampled in three rivers of the Iténez basin (Amazon, Bolivia).
Table 3.
Source relative contributions (mean % ± sd, estimated by SIAR mixing model) to detritivore (Psectrogaster sp. and Curimatella cf. alburna) and herbivore (Schizodon fasciatus) fish diet in three rivers of the Iténez basin.
Figure 3.
Mercury biomagnification in fish assemblage of three rivers from the Iténez basin (Amazon, Bolivia).
Biplots display mean values (± sd in error bars) of Trophic Position (derived from δ15N) and [Hg]ww of detritivore (1 = Curimatella cf. alburna, 2 = Psectrogaster sp.), herbivore (3 = Schizodon fasciatus), insectivore (4 = Triportheus angulatus) and piscivore (5 = Pseudoplatystoma sp., 6 = Pygocentrus nattereri, 7 = Hoplias malabaricus and 8 = Acestrorhynchus sp.) fish species. Slope of the relation correspond to biomagnification along the food chain.