Exposure and potential food chain transfer factor of Cd, Se and Zn in marine fish Lutjanus argentimaculatus

Abstract

Radiotracer techniques were employed to quantify the rates of uptake from aqueous and dietary sources, and rates of elimination of Cd, Se and Zn by a marine predatory fish, the mangrove snapper Lutjanus argentimaculatus. The relative significance of bioaccumulation of metals by fish from water and food and the food chain transfer factor were then assessed using a kinetic modeling approach. Cd and Zn in the aqueous phase exhibited an approximately linear uptake pattern over a 1 to 2 d exposure, whereas Se exhibited a 2-compartmental uptake at a low ambient concentration, with a slow initial uptake followed by a rapid increase in Se influx. Most of the accumulated aqueous Se and Zn were incorporated into the muscles, whereas Cd was evenly distributed in the viscera and the remaining tissue, with a lower proportion in the gills. The influx rates were dependent on the ambient metal concentration and were tissue-specific for each metal. The assimilation efficiency of trace metals in fish ingesting different prey (copepods, Artemia sp. and clam tissue) ranged from 6 to 24% for Cd, 32 to 68% for Se and 15 to 46% for Zn, and decreased with an increase in ingestion rate. The efflux rate constant of Cd in fish following uptake from the dietary phase (0.047 d -1 ) was higher than that following aqueous uptake (0.025 d -1 ), whereas the efflux rate constants of Se and Zn were comparable between these 2 exposure pathways. Our modeling calculations indicate that dietary uptake of Cd and Zn dominates their accumulation in fish when zooplankton are the main prey, whereas aqueous uptake may be the dominant pathway when planktivorous fish are the dominant prey for the predatory fish. Dietary uptake always dominates Se accumulation in these fish. The modeling results also indicated that the food chain transfer factor of Cd was < 0.5 in the fish regardless of the ingestion rate and the assimilation efficiency, consistent with the results of field studies. However, Se and Zn may potentially be biomagnified when the ingestion rate and assimilation efficiency are at the high end of the range possibly encountered by the predatory fish. KEY WORDS: Metals · Mangrove snapper · Exposure · Food chain · Uptake Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 238: [173][174][175][176][177][178][179][180][181][182][183][184][185][186] 2002 2001). Organ specificity in metal accumulation may also be related to the metal speciation and the regulation of essential and non-essential metals (Hanson 1997, Baskin 2000, McGeer et al. 2000, Burgos & Rainbow 2001. Although most studies have quantified the metal concentrations in fish collected from the field, where they are exposed to metals both in the aqueous and in the dietary phases, it is difficult to quantitatively distinguish the metal uptake via food or water. Such information is useful for modeling metal transport within marine food chains and the interaction between fish and their environments.Recently, the kinetic modeling approach ha...

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