100
2018). Interspecific differences in the sensitivity to U, mainly caused by differences
on their trophic status, were observed between freshwater fish (Bywater et al. 1991)
species exposed to the same source of contamination.
The U present in natural waters can be bioaccumulated by aquatic biota (Fig. 4)
and is sometimes biomagnified through the food chain, representing a potential hazard to the organism itself and to other organisms, which can include human beings
(Bergmann et al. 2018). The bioaccumulation process relies on the differences
between the assimilation and depuration capacities of a given organism (Pauget
et al. 2017). Many studies have demonstrated the ability of aquatic plants to accumulate U in concentrations higher than the water they are exposed to (Favas et al.
2014, 2016). The high bioaccumulation capacity of some aquatic plant species supports its potential use in phytofiltration of waters contaminated by U (Cordeiro et al.
2016). Uranium accumulation was also observed in the periphyton community, with
no evidence of negative impact on the productivity and biomass (Bunn 2007). In
general, U accumulation is observed in the aquatic biota, inducing effects of different levels in the biological communities (Simon et al. 2018).
The ecotoxicological data about U is abundant for many aquatic species, which
is widely used to establish water quality guidelines (Sheppard et al. 2005).
Ecotoxicological tests using local freshwater organisms are performed since the
1980s (Cheng et al. 2010). Classical endpoints of ecological relevance in terms of
population dynamics include mortality, growth, reproduction, and morbidity
(Beaugelin-Seiller et al. 2012). Extensive information about early and sublethal
effects of the exposure of aquatic organisms to high U concentrations is available.
Measurements of neurotoxicity (Barillet et al. 2007), oxidative stress (Reis et al.
2018), and genotoxicity (Barillet et al. 2011) were used as endpoints to understand
the primary subcellular damage caused by U interaction with the biota. Increased
physiological effects were also observed across generations of microcrustaceans
exposed to U (Massarin et al. 2010). However, knowledge about the trends of the U
interaction with aquatic organisms under environmentally realistic concentrations
found in natural waters is still not well-established, mainly in tropical regions.
A few examples of bioaccumulation and toxicity tests can be found in the literature focusing on tropical freshwater and aquatic organisms. For example, Ferrari
et al. (2017) investigated the U toxicity of aquatic organisms in the vicinity of the
Osamu Utsumi mine, at Poços de Caldas city, Brazil. Chemical analysis and acute
toxicity tests using two species of microcrustaceans (Ceriodaphnia silvestrii and
Daphnia magna) were conducted in threated U mine effluents and waters of the
Antas Reservoir. The spatial distribution of the U concentrations was similar to the
acute toxicity observed for both species. Furthermore, the data obtained demonstrated that the variation in water hardness (mainly related to the treatment of the
effluents) considerably influenced the toxicity to microcrustaceans. Water hardness
was demonstrated to have a protective effect to the aquatic species studied. This
study provided very useful information about the U toxicity to aquatic organisms in
tropical areas, since C. silvestrii is a microcrustacean species widely distributed
throughout South America.
J. A. Galhardi et al.
2018). Interspecific differences in the sensitivity to U, mainly caused by differences
on their trophic status, were observed between freshwater fish (Bywater et al. 1991)
species exposed to the same source of contamination.
The U present in natural waters can be bioaccumulated by aquatic biota (Fig. 4)
and is sometimes biomagnified through the food chain, representing a potential hazard to the organism itself and to other organisms, which can include human beings
(Bergmann et al. 2018). The bioaccumulation process relies on the differences
between the assimilation and depuration capacities of a given organism (Pauget
et al. 2017). Many studies have demonstrated the ability of aquatic plants to accumulate U in concentrations higher than the water they are exposed to (Favas et al.
2014, 2016). The high bioaccumulation capacity of some aquatic plant species supports its potential use in phytofiltration of waters contaminated by U (Cordeiro et al.
2016). Uranium accumulation was also observed in the periphyton community, with
no evidence of negative impact on the productivity and biomass (Bunn 2007). In
general, U accumulation is observed in the aquatic biota, inducing effects of different levels in the biological communities (Simon et al. 2018).
The ecotoxicological data about U is abundant for many aquatic species, which
is widely used to establish water quality guidelines (Sheppard et al. 2005).
Ecotoxicological tests using local freshwater organisms are performed since the
1980s (Cheng et al. 2010). Classical endpoints of ecological relevance in terms of
population dynamics include mortality, growth, reproduction, and morbidity
(Beaugelin-Seiller et al. 2012). Extensive information about early and sublethal
effects of the exposure of aquatic organisms to high U concentrations is available.
Measurements of neurotoxicity (Barillet et al. 2007), oxidative stress (Reis et al.
2018), and genotoxicity (Barillet et al. 2011) were used as endpoints to understand
the primary subcellular damage caused by U interaction with the biota. Increased
physiological effects were also observed across generations of microcrustaceans
exposed to U (Massarin et al. 2010). However, knowledge about the trends of the U
interaction with aquatic organisms under environmentally realistic concentrations
found in natural waters is still not well-established, mainly in tropical regions.
A few examples of bioaccumulation and toxicity tests can be found in the literature focusing on tropical freshwater and aquatic organisms. For example, Ferrari
et al. (2017) investigated the U toxicity of aquatic organisms in the vicinity of the
Osamu Utsumi mine, at Poços de Caldas city, Brazil. Chemical analysis and acute
toxicity tests using two species of microcrustaceans (Ceriodaphnia silvestrii and
Daphnia magna) were conducted in threated U mine effluents and waters of the
Antas Reservoir. The spatial distribution of the U concentrations was similar to the
acute toxicity observed for both species. Furthermore, the data obtained demonstrated that the variation in water hardness (mainly related to the treatment of the
effluents) considerably influenced the toxicity to microcrustaceans. Water hardness
was demonstrated to have a protective effect to the aquatic species studied. This
study provided very useful information about the U toxicity to aquatic organisms in
tropical areas, since C. silvestrii is a microcrustacean species widely distributed
throughout South America.
J. A. Galhardi et al.