The effects of mining tailings in the physiology of benthic algae: understanding the relation between mud’s inductive acidification and the heavy metal’s toxicity

Highlights

• Mariana’s mud was evaluated for toxic effects of heavy metals and acidification.

• Sargassum cymosum and Hypnea musciformis were evaluated for physiological responses.

• The presence of mud and acidic conditions caused lethality and metabolic damages.

• The acidified condition had the greatest impact over physiology of both species.

• The toxicity effects of mining tailings are intensified by abiotic changes.

Abstract

The direct and indirect effects of mining tailing on macroalgae were evaluated in vitro to determine the relationship between heavy metals toxicity and pH alterations caused by the presence of pollutants. The marine brown seaweed Sargassum cymosum (C. Hagard 1820) and its main epiphytic alga, the red seaweed Hypnea pseudomusciformis (Nauer, Cassano, Oliveira, 2015), were exposed to Mariana’s mud in cross treatments, including presence or absence of mud, and normal (˜8.0) or acidic (˜7.0) pH conditions. The effects of different biological conditions were also evaluated in two treatments, with seaweed in isolated or associative conditions, for a seven-day period. The measured variables were growth rates and metabolic descriptors, such as chlorophyll a, phenolic compounds, total proteins, and the analysis of enzymatic activity, e.g. catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD). Kruskal-Wallis and post-hoc Dunn’s test were performed to evaluate the significant differences among treatments and biological conditions. Decreased growth rates in treatments with presence of mud or in acidic conditions were detected and probably related to deviations of metabolic energy towards the synthesis of defensive metabolites. Especially in the acidified culture medium, both algae species presented significant declines in pigments concentration, antioxidant compounds and an accentuated inhibition of enzymatic activity. The algal association was not beneficial for either species and H. pseudomusciformis was responsible for reducing the defensive ability of Sargassum against stressors. Considering the results, we infer that the physiological ability of both algae to resist metals and/or acidified conditions was affected not only by their mutual interference in each other, but also by the interaction between the abiotic parameters evaluated in this study.

Costa G. B., Ramlov F., Koerich G., Navarro B. B., Cabral D., Rodrigues E. R. O., Ramos B., Fadigas S. D., Rörig L. R., Maraschin M. & Horta P. A., 2019. The effects of mining tailings in the physiology of benthic algae: understanding the relation between mud’s inductive acidification and the heavy metal’s toxicity. Environmental and Experimental Botany 167: 103818. doi: 10.1016/j.envexpbot.2019.103818. Article (subscription required).

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