Effect of oxytetracycline on the community structure of nematodes: results from microcosm experiments

The release of antibiotics to the environment after use by fish farms could have potentially negative effects. Here, we assessed how the antibiotic oxytetracycline (OTC) affect the meiofaunal communities of Jeju Island in Korea. We assessed how: 1) nematodes responded to 0–2000 ppm OTC over 48 h; 2) Metoncholaimus spp. (the most abundant group) responded to 0–500 ppm OTC over 48 h; and 3) the meiofaunal community responded to 0–200 ppm OTC for 1-month. In experiment 1, all nematodes died at high antibiotic concentrations (1000 ppm, 2000 ppm), but death rates rapidly decreased at 500 ppm (42%) and below (0–9%). In experiment 2, Metoncholaimus spp. death rates were similar to those documented in experiment 1 for OTC concentrations of 500 ppm (45%) and decreased at 125 ppm and 250 ppm (to 30% and below). In experiment 3, long-term exposure to low concentrations (200 ppm or less) of OTC did not have a strong effect on meiofaunal density, with meiofaunal density in the experimental group showing no decline with OTC concentration. However, we confirmed that differences in OTC concentration affects the structure of meiofaunal communities, making it important to regulate their use by fish farms.