Multi-marker study of the responses of the Unio tumidus from the areas of small and micro hydropower plants at the Dniester River Basin, Ukraine.

The impact of the hydropower plants (HPPs) on the aquatic life is expected, but the biochemical markers of ecotoxicity have not been investigated in relation to HPP proximity. The aim of this study was to compare the responses of mollusk Unio tumidus from the small HPP (reservoir (Ku) and downstream of the dam (Kd)) and micro HPP (upstream (Zu) and downstream of the dam (Zd)). In total, 11 indexes (n) from digestive gland, hemocytes (lysosomal integrity), and gonads (alkali-labile phosphates, ALP) were analyzed. The mollusks from the reservoir demonstrate the typical signs of toxic impact: cholinesterase and glutathione depletion, the highest glutathione S-transferase activity, and ratio of extralysosomal cathepsin D compare to all other groups. The specimens from the micro HPP have the highest levels of glutathione (Zd) and lipid peroxidation (Zu) and lesser Cu/Zn-SOD activity (Zu) than other groups. These indications of stressful conditions may derive from the regular oscillations in the water flow regimes at the micro HPP. For both HPPs, the responses of upstream and downstream groups are distinct. The calculated IBR/n (4.17, 3.85, 3.12, and 0.26 for Ku, Kd, Zu, and Zd correspondingly) gives a quantitative basis for the evaluation of environmental impact of HPPs. Graphical abstract .

Biochemical responses of freshwater mussel Unio tumidus to titanium oxide nanoparticles, Bisphenol A, and their combination.

Multiple interactions between different pollutants in the surface waters can cause unpredictable consequences. The aim of the study was to evaluate the combined effect of two widespread xenobiotics, titanium oxide nanoparticles (TiO2) and bisphenol A (BPA), on freshwater bivalve Unio tumidus. The specimens were exposed for 14 days to TiCl4 (Ti, 1.25 µM), TiO2 (1.25 µM), BPA (0.88 nM), or their combination (TiO2 + BPA). Every type of exposure resulted in a particular oxidative stress response: TiO2 had antioxidant effect, decreasing the generation of reactive oxygen species (ROS) and phenoloxidase (PhO) activity, and doubling reduced glutathione (GSH) concentration in the digestive gland; Ti caused oxidative changes by increasing levels of ROS, PhO and superoxide dismutase; BPA decreased the GSH level by a factor of two. In the co-exposure treatment, these indices as well as lysosomal membrane stability were not affected. All Ti-containing exposures caused elevated levels of metalated metallothionein (Zn,Cu-MT), its ratio to total metallothionein protein, and lactate/pyruvate ratio. Both BPA-containing exposures decreased caspase-3 activity. All exposures, and particularly co-exposure, up-regulated CYP450-dependent oxidation, lipid peroxidation and lipofuscin accumulation, lysosomal cathepsin D and its efflux, as well as alkali-labile phosphates in gonads and caused DNA instability (except for TiO2). To summarize, co-exposure to TiO2 + BPA produced an overlap of certain individual responses but strengthened the damage. Development of water purification technologies using TiO2 requires further studies of the biological effects of its mixtures. U. tumidus can serve as a sentinel organism in such studies.