Abstract
Free-living macrophytes play an important role in the health of aquatic ecosystems. Therefore, the use of aquatic plants as metal biomonitors may be a suitable tool for the management of freshwater reservoirs. Hence, in this study, we assessed the effects of cadmium (Cd) in Salvinia biloba specimens collected from the Middle Paraná River during a 10-day experiment employing artificially contaminated water (100 μM Cd). S. biloba demonstrated a great ability for Cd bioaccumulation in both the root-like modified fronds (named “roots”) and the aerial leaf-like fronds (named “leaves”) of the plants. Additionally, Cd toxicity was determined by the quantification of photosynthetic pigments (chlorophylls a and b, and carotenoids), flavonoids, and soluble carbohydrate contents in S. biloba over time (1, 3, 5, 7, and 10 days). In general, deterioration was more pronounced in leaves than in roots, suggesting a greater implication of the former in long-term Cd sequestration in S. biloba. Deleterious effects in the appraised parameters were well correlated with the total amount of Cd accumulated in the leaves, and with the qualitative changes observed in the plants’ phenotype during the 10-day metal exposure assay. The flavonoids and carotenoids in leaves were highly affected by low Cd levels followed by root carbohydrates. In contrast, chlorophylls and root flavonoids were the least impacted physiological parameters. Therefore, our results demonstrate that S. biloba displays dissimilar organ-linked physiological responses to counteract Cd phytotoxicity and that these responses are also time-dependent. Though further research is needed, our work suggests that easy-handled physiological data obtained from autochthonous free-floating S. biloba specimens may be used as a valuable tool for metal-polluted water biomonitoring.
Highlights
Free-floating macrophytes are macroscopic aquatic plants that play an important role in aquatic ecosystem health
We have demonstrated that Cd uptake within S. biloba biomass was the main removal mechanism used by these macrophytes to remove the metal from the water column [12]
We evaluate the pattern of Cd bioaccumulation in the root-like modified fronds and the aerial leaf-like fronds of naturally occurring S. biloba specimens during 10 days of plant exposure to water artificially contaminated with 100 μM Cd
Summary
Free-floating macrophytes (i.e., hydrophytes) are macroscopic aquatic plants that play an important role in aquatic ecosystem health. These organisms are key components in natural wetlands and can serve as bioindicators of a variety of ecosystem stressors such as nutrient runoff, changes in hydrologic regime, and exotic species invasion. During the last two decades, free-floating macrophytes have been extensively studied in relation to its growth, metabolic response, and phytoremediation capacity towards several environmental contaminants, especially heavy metals [5,6,7,8,9,10,11]. Local macrophyte species with an elevated biomass production rate enable more sustainable and economically viable phytoremediation strategies, especially in areas where communities have limited financial resources [12,13,19]
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