ZINC EXPOSURE OF PALAEMONETES ARGENTINUS AND POTAMOGETON PUSSILLUS: BIOMARKERS? SELECTION AND POTENTIAL USE OF NATIVE SPECIES AS METAL CONTAMINATION BIOINDICATORS

BERTRAND, L.; AMÉ, M.V; MONFERRÁN, MAGDALENA VICTORIA

Guaraparí

Congreso; ECOTOX 2014; 2014

Heavy metals are among main environmental pollutants. Chemical analysis quantifies pollutants in detail, but lack the ability to judge the impact of those on biota. Thus, biomarkers, were developed to assess the impact of environmental pollutants in terms of exposure and damage of organisms. The aim of this work was to evaluate the response of biomarkers in freshwater shrimp and the macrophyte experimentally exposed to zinc (Zn) and the potential use of them as bioindicators of aquatic pollution. The experimental design involved 96h of exposure and 4 experimental conditions: control, 5 μgZnL-1=[1], 50 μgZnL-1=[2], 500 μgZnL-1=[3]. Several biomarkers of effects (Thiobarbituric acid reactive substances=TBARs, peroxide=Pe, carbonylated protein=CP, cholinesterase and antioxidants enzymes activity, metallothionein=MT, Chlorophylls= Cl a and Cl b, Phaeophytins = Pheo a and Pheo b) and exposure (accumulation= Accu, cytosolic=S and insoluble=P zinc) were measured. Our results indicate a differential response pattern between body sectors of shrimps. In cephalothorax a net Accu and P fraction increase occurred from [2]. The increase in P fraction could be indicating a cellular metal detoxification strategy. The cytosolic Zn rise occurred only at [3] and it was closely correlated with MT induction. Significant inhibition of microsomal AChE reported at [3] could be indicating a negative effect of an essential metal over the nervous system. Evidence of lipid damage has been found at [3] even though the increase of Pe levels has been detected from [1]. The TBARs increase probably induces the enhanced response of cytosolic GST, an enzyme with capacity to reduce lipid hydroperoxides. Superoxide dismutase (SOD) and catalase are the enzymes responsible for the removal of ROS, both increased their activity at [3] when Pe and TBARs showed higher levels. Moreover, in abdomen P fraction increase has been observed from [2] and net Accu at [3] as S fraction. A significant damage over proteins has been quantified from [2]. CP expression occurred at lower exposure concentration than the net Zn Accu. GPx, SOD, microsomal and cytosolic GST have been inhibited from [1]. Inhibitor effect of Zn over GPx has been reported(1). Conversely, microsomal AChE activity increased from the lowest Zn concentration while GR risen its activity only at [3] probably to maintain levels of GSH an antioxidant molecule. In both body sectors, cytosolic ChEs have had a rapid response with inhibition from [1] which can explain the protective role of these enzymes. The metal interaction with cytosolic ChE enzymes avoids the interaction with microsomal isoform directly linked with nervous impulse. P. pusillus leaves presented Accu from [2] and Pe increase from [1] . Pigments like Cl a and Pheo a increased from [1]. Cl b also increased concentration at [2] and [3]. At low levels, Zn maintains chlorophyll synthesis through SH- group protection, which could explain the pigments? rise (2). GR and GPx activities have been inhibited at [3]. In stem, a significant metal Accu occurred from [1] and GPx was the only enzyme with an increase in activity at [1] and [2]. In root, Accu occurred from [1] and the Pe level increase occurred also from [1]. Finally, GPx and GR showed a significant inhibition from [1] and [2], respectively. Discriminant analysis showed in P. argentinus that the inhibition pattern of cytosolic AChE and increase patterns of Accu, MT, SOD and Pe, could be explain differences among exposure conditions in cephalothorax. Instead, in abdomen, a dose response inhibition was observed for GSTm, GPx, BChE and SOD, while an augment was observed for CP, GR and AChEm. The biomarkers response points out P. argentinus as potential bioindicator of Zn contamination. Conversely, in P. pussillus the Accu proved to be sensitive biomarker of Zn water contamination, especially in leaves and roots, suggesting a potential use of macrophyte as bioindicator of metal contamination and water phytoremediation.