title: Methylmercury levels and bioaccumulation in the aquatic food web of a highly mercury-contaminated reservoir.
abstract: The low Ebro River basin (NE Spain) represents a particular case of chronic and long-term mercury pollution due to the presence of an industrial waste (up to 436 μg/g of Hg) coming from a chlor-alkali plant Albeit high total mercury (THg) levels have been previously described in several aquatic species from the surveyed area, methylmercury (MeHg) values in fish individuals have never been reported. Accordingly, in order to investigate bioaccumulation patterns at different levels of the aquatic food web of such polluted area, crayfish and various fish species, were analysed for THg and MeHg content. At the hot spot, THg mean values of crayfish muscle tissue and hepatopancreas were 10 and 15 times, respectively, greater than the local background level. Higher mean THg concentrations were detected in piscivorous (THg=0.848 ± 0.476 μg/g wet weight (ww); MeHg=0.672 ± 0.364 μg/g ww) than in non-piscivorous fish (THg=0.305 ± 0.163 μg/g ww; MeHg=0.278 ± 0.239 μg/g ww). Although these results indicated that THg in fish increased significantly with increasing trophic position, the percentage of the methylated form of Hg was not strongly influenced by differences in relative trophic position. This is an important finding, since the fraction of THg as MeHg in the top fish predator was unexpectedly lower than for other species of the aquatic food chain. Moreover, mean THg concentrations in piscivorous fish exceed the maximum level recommended for human consumption. From our findings, it is clear that for this specific polluted system, speciation becomes almost mandatory when risk assessment is based on MeHg, since single measurements of THg are inadequate and could lead to an over- or under-estimation of contamination levels.
authors.affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research, IDAEA-CSIC, Jordi Girona, 18-26. E-08034 Barcelona, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Carrasco
authors.forename: Lluís
authors.initials: L
authors.lastname: Benejam
authors.forename: Josep
authors.initials: J
authors.lastname: Benito
authors.forename: Josep M
authors.initials: JM
authors.lastname: Bayona
authors.forename: Sergi
authors.initials: S
authors.lastname: Díez
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000378:metabolism*; D003400:Astacoidea / Q000378:metabolism; D004784:Environmental Monitoring; D005399:Fishes / Q000378:metabolism; D020387:Food Chain; D043143:Hepatopancreas / Q000378:metabolism; D007220:Industrial Waste / Q000032:analysis; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D045483:Rivers / Q000737:chemistry; D013030:Spain; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*; D014881:Water Supply / Q000032:analysis
chemical_list: D007220:Industrial Waste; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury