Biomagnification of mercury in a marine grazing food-chain: algal cells Phaeodactylum tricornutum, mussels Mytilus edulis and flounders Platichthys flesus studied by means of a stepwise-reduction-CVAA method

Abstract

A stepwise-reduction-cold vapor atomic absorption spectrometry (CVAA) method has been further developed. The method is relatively simple and quick and allows measurements of both inorganic and organic mercury in the same small biological sample. It provides an effective technique for studying biomagnification of mercury in a marine grazing food-chain (algae/mussels/fish). In laboratory experiments with mussels exposed to both inorganic mercury (965 ng I-') and organic mercury (methylmercury) (35 ng I-'), and fed algal cells at a natural low concentration from a chemostat for 80 d, uptake of both mercury species was linear. Organic mercury was taken u p 15 times more readily than inorganic mercury. Flounders force-fed with food contaminated with equal concentrations of organic and inorganic mercury for 46 d readily accumulated organic mercury in blood cells, liver, kidney and muscle-tissue while inorganic mercury was only accumulated in measurable amounts in Liver and kidney. During an elimination experiment (48 d) with both force-fed and starved flounders (loaded with mercury), organic mercury concentration did not decrease in the muscle-tissue, but significantly decreased in the liver, kidney and blood cells, while inorganic mercury tended to increase in the liver. Thus organic mercury may be biotransformed to inorganic mercury in the liver. Relatively low concentrations of organic mercury in the gall bladder indicate that enterohepatic recirculation may not play a similar role in fish as reported for mammals. Higher mercury concentrations in the proximal part of the intestine compared to the distal part show, however, that some mercury may be secreted via the bile and reabsorbed, but no differences between fed and starved fish were found Though only about 1 % of the total mercury in chronically polluted waters may be in the organic form, an enhanced uptake rate of organic mercury in mussels leads to differential partitioning of the 2 mercury forms. Since fish such as flounder may primarily feed on juvenile bivalves about 75 % of the total mercury ingested by fish may be in the inorganic form. The efficient accumulation of organic mercury and the lack of elimination results in an increasing organic mercury concentration with both age and trophic level (i.e. biomagnification) in the marine grazing food-chain.

Mercury in fishes from Augusta Bay (southern Italy): Risk assessment and health implication

“…This implies potential effects on the food web of the surrounding area as already reported by several authors studying marine systems (Riisgard and Hansen, 1990;Futter, 1994;Jarman et al, 1996;Atwell et al, 1998). This hypothesis is supported by the high mean HgT concentrations measured in pelagic species caught outside the bay, which are similar to those reported for other sites affected by Hg pollution: the Adriatic Sea (Wolfgang, 1983;Storelli and Marcotrigiano, 2001;Storelli et al, 2002Storelli et al, , 2004Storelli et al, , 2007Storelli et al, , 2010Gibičar et al, 2009), Turkish areas (Tuzen, 2009), Spanish coastal areas (Pastor et al, 1994) and Israel area (Hornung et al, 1980) (Table 2).…”

Bioaccumulation kinetics and exposure pathways of inorganic mercury and methylmercury in a marine fish, the sweetlips Plectorhinchus gibbosus

“…In contrast, no Hg(II) was found in the head after 28 d elimination. Riisgaard & Hansen (1990) showed that flounder Platichthys flesus force-fed with contaminated mussels accumulated MeHg in blood cells, liver, kidney and muscle tissues, while Hg(II) only accumulated in measurable amounts in the liver and kidney.…”

“…In contrast, no Hg(II) was found in the head after 28 d elimination. Riisgaard & Hansen (1990) showed that flounder Platichthys flesus force-fed with contaminated mussels accumulated MeHg in blood cells, liver, kidney and muscle tissues, while Hg(II) only accumulated in measurable amounts in the liver and kidney.We used the radiotracer technique to study the biokinetics of Hg(II) and MeHg in the sweetlips. Whether there was any biotransformation (methylation and demethylation) within the fish body was not revealed by our study.…”

Influence of trophic position and foraging range on mercury levels within a seabird community

“…Mercury (Hg) is a non-essential heavy metal that biomagnifies within food webs (Riisgard & Hansen 1990, Jarman et al 1996 and can accumulate in toxic concentrations in top predators (Eisler 1987). Although high levels of exposure are often associated with localised sources of pollution (such as chlor-alkali works or lignite burning), elevated concentrations have also been reported in biota from high latitudes (Wagemann et al 1990, Bocher et al 2003.…”