Erythromycin is an antibiotic employed in the treatment of infections caused by Gram positive microorganisms and the increasing use has made it a contaminant of emerging concern in aqueous ecosystems. Cerium oxide nanoparticles (CeO₂ NPs), which are known to have catalytic and antioxidant properties, have also become contaminants of emerging concern. Due to the high reactivity of CeO₂ NPs, they can interact with erythromycin magnifying their effects or on the other hand, considering the redox potential of CeO₂ NPs, it can alleviate the toxicity of erythromycin. The present study was carried out to assess the toxicity of both single compounds as well as mixed on Chlamydomonas reinhardtii and Phaeodactylum tricornutum (freshwater and marine microalgae respectively) employed as target species in ecotoxicological tests. Mechanisms of oxidative damage and those harmful to the photosynthetic apparatus were studied in order to know the toxic mechanisms of erythromycin and the joint effects with CeO₂ NPs. Results showed that erythromycin inhibited the microalgae population growth and effective quantum yield of PSII (E.Q.Y.) in both microalgae. However, the freshwater microalgae Chlamydomonas reinhardtii was more sensitive than the marine diatom Phaeodactylum tricornutum. Responses related to the photosynthetic apparatus such as E.Q.Y. was affected by the exposure to erythromycin of both microalgae, as chloroplasts are target organelle for this antibiotic.

Mixed experiments (CeO₂ NPs + erythromycin) showed the protective role of CeO₂ NPs in both microalgae preventing erythromycin toxicity in toxicological responses such as the growth of the microalgae population and E.Q.Y.

红霉素是一种用于治疗由革兰氏阳性微生物引起的感染的抗生素，并且越来越多的用途使其成为水生生态系统中日益受到关注的污染物。已知具有催化和抗氧化性能的氧化铈纳米颗粒（CeO ₂ NPs）也已成为人们关注的污染物。由于CeO ₂ NPs的高反应性，它们可以与红霉素相互作用，从而扩大其作用；另一方面，考虑到CeO ₂ NPs的氧化还原电位，它可以减轻红霉素的毒性。进行本研究以评估两种化合物以及混合的两种化合物对莱茵衣藻和三角藻的毒性。（分别为淡水和海洋微藻）作为生态毒理学测试的目标物种。为了了解红霉素的毒性机理以及与CeO ₂ NPs的联合作用，研究了氧化损伤的机理以及对光合作用装置有害的机理。结果表明，红霉素抑制了两种微藻中微藻种群的生长和PSII（EQY）的有效量子产率。但是，淡水微藻衣藻比海藻硅藻Phaeodactylum tricornutum更敏感。与光合作用相关的反应（例如EQY）受两种微藻暴露于红霉素的影响，因为叶绿体是该抗生素的目标细胞器。

混合实验（CeO ₂ NPs +红霉素）显示，CeO ₂ NPs在两种微藻中均具有保护作用，可防止红霉素在毒理学响应（例如微藻种群增长和EQY）中的毒性