496 Environmental Toxicology and Chemistry, Vol. 28, No. 3, pp. 496–502, 2009  2009 SETAC Printed in the USA 0730-7268/09 $12.00 + .00 COMPARISON OF WATER, SEDIMENT, AND PLANTS FOR THE MONITORING OF ANTIBIOTICS: A CASE STUDY ON A RIVER DEDICATED TO FISH FARMING HERVE ´ POULIQUEN,*† RAPHAE ¨ L DELE ´ PE ´ E,‡ CHANTAL THORIN,† JACQUES HAURY,†§ MICHAE ¨ LLE LARHANTEC-VERDIER,† MARIE-LINE MORVAN,† and HERVE ´ LE BRIS†§ †National Institute of Agriculture Research–National Veterinary School of Nantes, No. 1300 Bioagressor, National Veterinary School of Nantes, B.P. 40706, 44307 Nantes Cedex 03, France ‡Institut de Chimie Organique et Analytique, UMR CNRS 6005, Universite ´ d’Orle ´ans, BP 6759, 45067 Orle ´ans Cedex 2, France §National Institute of Agriculture Research, Agrocampus Rennes, UMR 985, 65 Rue de St Brieuc, CS 84215, 35042 Rennes Cedex, France ( Received 22 May 2008; Accepted 11 September 2008) Abstract—Oxolinic acid, flumequine, oxytetracycline, and florfenicol are antibiotics commonly used in farming. Because an important percentage of these antibiotics given to fish and cattle ends up, directly or indirectly, in the freshwater environment, suitable tools for the monitoring of these antibiotics are needed. A French river was chosen because of the location of four fish farms and a sewage plant on its main course. First, a passive monitoring program involving water, sediment, and autochthonous bryophytes was performed at 25 sampling sites tested once every three months for one year. Second, an active monitoring method was performed using moss bags for a one-month exposure period, both upstream and downstream of each potential source of antibiotics. Sediment and bryophyte samples, but not water samples, were found to be useful for monitoring environmental con- tamination by oxolinic acid, flumequine, oxytetracycline, and florfenicol. Sediments and bryophytes also appeared to be comple- mentary media for dating the river’s contamination by antibiotics. Data collected by both active and passive monitoring methods confirmed contamination of the river, mainly by flumequine and oxytetracycline, attributable to fish farming but also to terrestrial animal farming and perhaps human pharmaceuticals. Keywords—Oxytetracycline Oxolinic acid Flumequine Florfenicol Freshwater contamination INTRODUCTION In recent years, pharmacological substances in aquatic en- vironments have gained increasing attention because of their presence in surface, ground, and drinking water [1–3]. An unknown percentage of these substances ends up, directly or indirectly, in the receiving waters through sewage treatment plants. Approximately 70 to 80% of the antibiotics adminis- tered as medicated pellet feed in intensive fish farming are released into the aquatic environment as urinary and fecal excretion and uneaten medicated feed [4–7]. In France, inten- sive freshwater fish farming is the primary aquacultural en- terprise. The main antibiotics used in French fish farming are oxolinic acid (OA), flumequine (FLU), oxytetracycline (OTC), and florfenicol (FLO) because of their broad antibacterial spec- trum and high potency. In this context, it is essential to monitor OA, FLU, OTC, and FLO in the freshwater environment. Using water to mon- itor xenobiotics in the freshwater environment is not easy be- cause of the rapid dilution of pollutants. Sediments are widely used to monitor pollutants in the environment, and many au- thors have described the adsorption and accumulation of an- tibiotics in sediments [8–16]. The major problem with sedi- ment monitoring is that adsorption and degradation of anti- biotics differed with the structure and microbial activity of the sediment (sand, mud, or muddy sand) [10]. Recently, the bryo- phyte Fontinalis antipyretica Hedw. was found to strongly accumulate AO, FLU, and OTC in freshwater [17]. The same bryophyte did not show these accumulation abilities toward * To whom correspondence may be addressed (pouliquen@vet-nantes.fr). Published on the Web 11/3/2008. FLO (H. Pouliquen, Research Unit INRA–ENVN No. 1300, Nantes, France, unpublished data). As active compounds, antibiotics must be consider potential environmental micropollutants. High concentrations of anti- biotics in sediments may lead to the inhibition of river mi- croflora but also to the development of antibiotic-resistant mi- croflora, especially in the vicinity of fish farms [18]. Never- theless, in the freshwater environment, the presence of sedi- ments seriously reduced the biological activity of some antibiotics, such as OTC [19]. In the presence of divalent cations, such as Mg ++ and Ca ++ , it is unlikely that OTC con- centrations in sediments up to 285 g/g are of any biological significance [13]. Their toxicity for nontarget organisms is another environmental problem. For example, high drug con- centrations in common aquatic macrophytes may lead to tox- icity in these plants [20–23]. The present study set up suitable tools for monitoring OA, OTC, FLU, and FLO in the freshwater environment based on laboratory experiments. The goals of the study were twofold. First, we set out to assess the relevance of water, sediment, and autochthonous or transplanted bryophytes to spatiotem- porally monitored antibiotics used in fish farming in a river ecosystem. Second, we wanted to highlight trends of contam- ination by antibiotics in a river dedicated to fish farming. MATERIALS AND METHODS Study area The study area corresponds to a portion of the coastal Elorn River in Brittany (Finiste `re region, France). The main eco- nomic activities in the study area are agricultural: Breeding cattle and pigs and farming fish. Four fish farms and one sew- age treatment plant are located along the river [24] (Fig. 1).