DYNAMIC ANALYSIS OF DISSOLVED ORGANIC SUBSTANCES IN ENCLOSED COASTAL SEA ENVIRONMENT; PERSISTENCE AND ACCUMULATION OF ANTIBIOTICS IN SEAWATER AND PLANKTON

摘要

Antibiotics have been licensed for use in a variety of food-producing animals and fishes including sheep, cattle, pig, poultry, yellowtail, and so on, in which they function as broad-spectrum bacteriostatic agents by inhibiting protein synthesis. However, there are not so many reports with regard to the fate and behavior of antibiotics in seawater and marine creatures, which means persistency of them in seawater and accumulation of them in plankton, shellfishes, fishes , and so on. The aim of the present study is to investigate the accumulation of the antibiotics in plankton cultivated in a medium including antibiotics and to proceed the monitoring of the persistent antibiotics in seawater and sediment Our analytical procedure includes solid-phase extraction method for sample preparation and HPLC/MS analysis of the extracts from plankton and seawater. The electrospray ionization HPLC/MS analysis of antibiotics is performed using acetonitrile/water mobile phase and an octadecyl-bonded silica gel column (ODS column). Diatom, Skeletonema costatum, has been cultivated in the medium including antibiotics to proceed our practical experiment for accumulation of antibiotics. The cultivated medium and plankton are collected in every six days and used for the analysis. When the oxytetracycline (OTC) is used as a source of antibiotics at the range of from 0.1 to 2.0mM in the medium, OTC from 7.36 to 1,290·g are detected in the extracts from the cultivated diatoms (1 L), whose values correspond to 1.19～103.47fg/plankton. On the other hand, OTC levels from 0.05 to 4.9ppb are observed in seawater, collected at various points in the Uranouchi-bay (Kochi).