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

Abstract

We experimentally determined the assimilation efficiency (AE) of ingested prey, the uptake-rate constant from the aqueous phase, and elimination-rate constant of both inorganic Hg (Hg [II]) and methylmercury (MeHg) in a marine predatory fish, the sweetlips Plectorhinchus gibbosus, using radiotracer techniques. The AE of Hg(II) and MeHg ranged between 10 and 27% and between 56 and 95%, respectively, for 3 different prey (copepods, silverside, and brine shrimp). The ingestion rate of the fish did not significantly affect the AE of Hg(II). Uptake of both species of Hg proceeded in a linear pattern, and the calculated uptake-rate constant was 0.195 and 4.515 l g -1 d -1 for Hg(II) and MeHg, respectively. Most of the accumulated Hg(II) was distributed in muscle tissues, whereas the accumulated MeHg was distributed evenly between gills and muscle tissues. The calculated elimination-rate constants for MeHg were 0.0103 and 0.0129 d -1 following dietary and aqueous uptake, respectively, whereas the elimination-rate constant of Hg(II) following dietary uptake (0.0547 d -1 ) was 1.9 times higher than the elimination following aqueous uptake (0.0287 d -1 ). These experimentally determined values were incorporated into a kinetic model to predict the exposure pathways and the relative contribution of Hg(II) and MeHg to the sweetlips. At the high end of the bioconcentration factor for both species of Hg in the prey, dietary ingestion is likely to be the main channel for their accumulation in the fish. The relative contribution of Hg(II) vs MeHg to the overall Hg bioaccumulation is largely controlled by the relative concentration of MeHg dissolved in seawater. Similar to the results of numerous field studies, the kinetic model predicted a potential trophic transfer factor of < 0.6 for Hg(II) and >1 for MeHg under conditions likely to be experienced by the fish in its natural environment. KEY WORDS: Mercury · Methylmercury · Exposure · Fish · Kinetic modeling Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 261: [257][258][259][260][261][262][263][264][265][266][267][268] 2003 bioavailability of these Hg species in marine fishes are less well studied (Pentreath 1976a,b, Honda et al. 1978, Barkay et al. 1997, Rouleau et al. 1998.Most previous studies measured the concentration of different Hg species in different tissues of fishes (Leah et al. 1991, Monteiro et al. 1996, Joiris et al. 2000. The routes of Hg accumulation, including the relative importance of different Hg species (inorganic and organic) and exposure pathways (aqueous vs dietary),are not yet well understood. Whereas it has generally been assumed that fishes accumulate MeHg mainly from dietary sources through very efficient assimilation of this compound (Mason 2002), it is quite possible that, because of its highly efficient absorption properties, they accumulate it from the aqueous phase also. Experimental studies on the routes of methylmercury exposure in fishes are indeed rather controversial (Honda et...

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

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Trace metal incorporation in otoliths of a territorial coral reef fish (Abudefduf saxatilis) as an environmental monitoring tool

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Mercury in coastal watersheds along the Chinese Northern Bohai and Yellow Seas

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