The study aimed at measuring the influence of a wide range of oxytetracycline concentrations, with particular attention to the low levels of the antibiotic on cyanobacteria Microcystis aeruginosa and Nodularia spumigena, diatom Phaeodactylum tricornutum and the model green algae Chlorella vulgaris by conducting prolonged toxicity tests (lasting 10 days). Standard measurements (cell number, optical density, chlorophyll a concentration) were combined with photosynthetic parameters measurements. The obtained results show that concentrations of oxytetracycline present in the environment can affect tested microorganisms. It was found to decrease photosystem II efficiency and disrupt the photosynthesis process. A careful interpretation of photosynthetic parameters allowed a better understanding of the mode of action of oxytetracycline in relation to non-target photoautotrophic organisms like cyanobacteria and microalgae. In conclusion, it would appear that the use of standard chronic toxicity tests (72 h) does not allow to accurately and reliably assess the chronic impact of bioactive compounds including drugs and their metabolites on water organisms. On this basis, we recommend the application of extended duration tests.

该研究旨在测量广泛的土霉素浓度的影响，特别是通过进行长期的毒性试验，特别注意低浓度的抗生素对蓝藻铜绿微囊藻a和结节藻，硅藻Phaeodyylumum tricornutum和模型绿藻小球藻（Chlorella vulgaris）的抗生素含量低（持续10天）。标准测量（细胞数量，光密度，叶绿素a浓度）与光合作用参数的测量相结合。获得的结果表明环境中存在的土霉素浓度会影响被测微生物。发现降低光系统II效率并破坏光合作用过程。仔细解释光合作用参数可以更好地了解土霉素相对于非目标光自养生物（如蓝细菌和微藻）的作用方式。总之，使用标准的慢性毒性试验（72小时）似乎无法准确可靠地评估包括药物及其代谢产物在内的生物活性化合物对水生物的长期影响。在此基础上，我们建议应用持续时间测试。