Temporal variation of total mercury concentrations and burdens in the liver of eelpout Zoarces viviparus from the Forth Estuary, Scotland:implications for mercury biomonitoring

Abstract

The utility of fishes a s biomonitors for mercury in aquatic environments is widely recognised, with skeletal muscle a s the tissue normally chosen for most monitoring programmes. The liver may also be a suitable candidate tissue for monitoring, as it concentrates many pollutants to higher levels than muscle, and is closely involved with processes of metal dynamics, storage, and detoxification. Little consideration has been given previously to the validation of the use of liver for mercury biomonitoring, with regard to quantifying natural temporal vanation. This study considered such variation in the eelpout Zoarces viviparusL., a resident estuarine fish species collected from a subtidal site near a formerly major industrial mercury discharge in the Forth Estuary, eastern Scotland Llver and skeletal muscle mercury concentrations, liver weight, and body size variables were measured for 196 individual eelpout in seven 3-month periods. Liver Somatic Index (LSI) was significantly hlgher, and liver mercury concentrations significantly lower, in the summer than In other seasons. Llver mercury burden (the mass of liver mercury per fish), in contrast, showed only llmited sign~ficant seasonal variation relative to body size, implying that the observed seasonal variation of liver mercury concentratlon (by around a factor of 3 between summer and winter) results largely from the dilution of simllar burdens by a seasonally growing and shrinking liver. Such natural seasonal variation may confound the use of the muscle/liver mercury concentration ratio, which has been proposed as evldence of fish migrat~on between waters with different levels of mercury contamination. These results also suggest that, as variation in liver mercury concentrations is closely related to seasonal vanation in LSI, liver t~s s u e may not be a reliable monitor for mercury in temperate species of marine fishes with seasonally fluctuating l~v e r size.

Perfluorooctane sulfonic acid in bib (Trisopterus luscus) and plaice (Pleuronectes platessa) from the Western Scheldt and the Belgian North Sea: Distribution and biochemical effects

“…This distribution pattern was previously shown for several metals and volatile chlorinated compounds in the Scheldt [11,23,24]. Seasonal variation in eelpout (Zoarces viviparus) liver mercury burden results largely from the dilution of similar burdens by a seasonally growing and shrinking liver, illustrating the possible impact of tissue dilution on concentrations of toxicants in fish tissues [28]. These authors observed a concentration gradient for a number of metals in the soft body tissues of the periwinkle (Littorina littorea) paralleling their Western Scheldt pollution gradient.…”

“…Solé et al [27] found lower concentrations of several organic pollutants in muscle tissue of deep-sea fish with larger sizes and suggested that tissue dilution might be responsible for this phenomenon. Seasonal variation in eelpout (Zoarces viviparus) liver mercury burden results largely from the dilution of similar burdens by a seasonally growing and shrinking liver, illustrating the possible impact of tissue dilution on concentrations of toxicants in fish tissues [28]. Tissue dilution as a result of changes in nutritional status can also greatly influence tissue concentrations, as was illustrated for cadmium exposure of dogwhelks (Nucella lapillus) [29].…”

Are red mullet efficient as bio-indicators of mercury contamination? A case study from the French Mediterranean

“…Seasonal variation of Hg content in marine fishes is poorly documented (Greenfield et al, 2013;Kucuksezgin et al, 2001;Mathieson et al, 1996). As Hg has a higher affinity for proteins, muscle displays a higher Hg concentration than gonads (Webb et al, 2006).…”

Mercury and methylmercury distribution in tissues of sculpins from the Bering Sea

“…For instance, great sculpin ( Myoxocephalus polyacanthocephalus ) caught off Adak, Alaska, were found to have ratios of 1:1 (muscle–liver) and 3:1 (muscle– kidney) (Burger et al 2007b). A muscle–liver ratio of >1 for [Hg] has been reported in estuarine fish species and elasmobranchs (Mathieson et al 1996; Coelho et al 2010). In adult marine mammals including whales, pinnipeds, and polar bears (Hyvärinen et al 1998; Wagemann et al 1998; Dietz et al 2000; Frodello et al 2000; Moses et al 2009), liver and/or kidney generally have the highest [THg].…”

“…Additionally, muscle represents a higher percentage of the body weight (larger compartment) than liver or kidneys and is more likely to be preferentially consumed by humans. Even when the [THg] is lower in muscle than in liver, muscle may have a greater proportion of the body burden of Hg (Giblin and Massaro 1973; Mathieson et al 1996; Brookens et al 2008). Thus, if there is concern about the risk of Hg exposure through piscivory, it is critical to include muscle samples in any assessment, and this is particularly important in species where differential tissue-specific distribution of Hg has not been examined.…”