Influence of submarine groundwater discharge on Po-210 and Pb-210 bioaccumulation in fish tissues
Résumé
This study presents the results of the accumulation of Po-210 and Pb-210 in fish tissues and organs in a brackish-water marshland that is characterized by high concentrations of Rn-222 and Ra-226 supplied by submarine groundwater discharge (SGD). Tissues and organs from Cyprinus carpio, Chelon labrosus and Carassius auratus in the wetland were significantly enriched by both Pb-210 and Po-210 (up to 55 and 66 times, respectively) compared to blanks. The major input route of Pb-210 and Po-210 into the fish body seems to be through ingestion, due to the high levels of Pb-210 and Po-210 found in the gut content as well as in organs involved in digestion and metabolism (i.e. gut, kidney and hepatopancreas). Results showed that Po-210 was more accumulated in all fish tissues and organs except for the spine, which showed a higher affinity for Pb-210, due to its capacity to replace Ca from apatite in bones. Over all the variables analyzed, fish tissues/organs and, secondarily, fish species were the most important factors explaining the concentration of radionuclides, whereas fish length and the sampling location played a minor role. The relationship of the two radionuclides varied markedly among tissues and their concentration levels were only correlated in gills, gut and, marginally, in spines. In general, the highest values of Pb-210 and Po-210 concentrations in tissues were found on C. labrosus tissues rather C auratus and C carpio. This study demonstrates that inputs of natural radionuclides supplied by SGD to coastal semi-enclosed areas (such as marshlands, lagoons or ponds) may significantly increase the contents of Pb-210 and Po-210 in fish tissues/organs. Thus, this study represents one of the first evidences of direct ecological effects derived from SGD. (C) 2016 Elsevier Ltd. All rights reserved.