Effect of the antibiotic tetracycline on structural-functional characteristics of coccolithophore Chrysotila sp. and the degree of its calcification

Abstract

Coccolithophorids play a fundamental role in the marine carbon cycle, fixing inorganic carbon during photosynthesis and exporting CO2 during calcification. In the presented study, the toxic effect of tetracycline on coccolithophorids of Chrysotila sp. was evaluated and the possibility of removing the antibiotic from water using this microalga was investigated. Tetracycline at a concentration of 1–15 mg L−1 had no effect on the growth of Chrysotila sp. and at higher values (20–25 mg L−1) it stimulated the growth of the algae. As the concentration of tetracycline increased, a tendency to decrease the percentage of coccolith-covered cells in the culture was observed. At the same time, the growth of Chrysotila sp. was realized mainly at the expense of uncovered coccoliths cells, the number of covered cells changed insignificantly. Coccolith- covered and uncovered Chrysotila sp. cells showed different physiological responses to antibiotic addition. Calcified cells are more sensitive to tetracycline, which is expressed in an increase in their size and a decrease in granularity, a decrease in specific chlorophyll fluorescence and enzymatic (esterase) activity, and an increase in the production of reactive oxygen species. Reduction of cell calcification under exposure to pollutants is potentially dangerous by changes in the biogeochemical cycle of nutrient elements in the aquatic ecosystem.It is shown that the main mechanism of tetracycline removal from water is photodegradation. However, in the presence of Chrysotila sp. the rate of tetracycline degradation is significantly higher (by 7–15%) than in samples without algae.