Tetracycline

Two species of microalgae strains, M. aeruginosa and C. pyrenoidosa, were purchased from the freshwater algae culture collection at the Institute of Hydrobiology (FACHB), Wuhan, China, and cultivated in BG11 media (Table S1) prior use.
Tetracycline was obtained from J&K Scientific Ltd., Beijing, China. Microcystin-LR standard (SB05-287-2012) was purchased from the National Standard Material Center of China (Beijing, China). All reagents used were of analytical grade and ultrapure water (18 MΩ•cm) was used in all experiments.

Analytical standards included six antibiotics, ofloxacin (OFL), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), oxytetracycline (OTC), and tetracycline (TC) with purity >99.0%, and five medium-chain fatty acids, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and nonanoic acid, all purchased from J&K Chemical, Shanghai, China.
Stock standard solutions (1000 μg mL -1 ) for the six antibiotics were prepared every month by dissolving each compound in methanol and stored at 4 o C for further use. Working solutions were diluted with Milli-Q ultrapure water (Millipore, Bedford, MA, USA) and methanol (v/v = 50:50) to prepare a secondary mixed stock solution of 10 μg mL -1 . All of the working solutions were prepared every week and stored at 4 o C for further use.
summer of 2017. The seawater sample was filtered through a 0.45-μm membrane filter and stored at -4 o C until analysis. The sediment sample was air-dried at room temperature before grinding and sieving. Fish, shrimp, shellfish, and squid were purchased from local fishing boats (Weifang, China) and stored at -20 o C after grinding (JX-FSTPRP-24 grinder, Shanghai, China). All samples were analyzed within 1 wk of sample collection.