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Effect of microplastics PAN polymer and/or Cu2+ pollution on the growth of Chlorella pyrenoidosa
Summary
Researchers exposed the microalga Chlorella pyrenoidosa to polyacrylonitrile (PAN) textile microplastics and copper alone and in combination, finding that PAN amplified copper toxicity to algae, likely by altering copper speciation or cell surface interactions.
Polyacrylonitrile polymer (PAN), a common representative textile material and a microplastic, has significant influence on phytoplankton algae, especially with co-exposure with other pollutants, e.g. Cu. In the present study, we carried out experiments to reveal the population size variation trends of Chlorella pyrenoidosa over time (during a whole growth cycle of 6 days) under PAN and/or Cu. The levels of pigments (chlorophyll a, b, total chlorophyll and carotenoids), chlorophyll a fluorescence parameters, and other physiological and biochemical indices, containing total protein measurements of HO, catalase (CAT), and malondialdehyde (MDA) under different treatment groups were measured to explain the physio-ecological mechanism of the effect of PAN and/or Cu on the growth of C. pyrenoidosa. The results showed that PAN, Cu and the combination of PAN and Cu inhibited the growth of C. pyrenoidosa. Chlorophyll a and b decreased significantly with increasing levels of pollutants (PAN and/or Cu); however, the carotenoid levels increased with increasing levels of pollutants (PAN and/or Cu) for the first three cultivation days. The oxygen-evolving complexes (OECs) of C. pyrenoidosa had been damaged under Cu pollution. The results also showed that CAT activity, MDA content and HO activity of C. pyrenoidosa increased with increasing levels of pollutants (PAN and/or Cu); however, total protein content decreased with increasing levels of pollutants (PAN and/or Cu) at the first cultivation day. These results indicate that pollutants (PAN and/or Cu) are harmful to the growth of the C. pyrenoidosa population and negatively affect the levels and function of the pigments in C. pyrenoidosa by decreasing chlorophyll a and b levels, increasing carotenoid levels, and increasing antioxidant enzyme activity.