Differential Accumulation of Heavy Metals in Muscle and Liver of a Marine Fish, (King Mackerel, Scomberomorus cavalla Cuvier) from the Northern Gulf of Mexico, USA

Abstract

Levels of heavy metals such as lead, copper, cadmium, andzinc in marine fish have been extensively documented inthe primary literature (e.g., Juresˇa and Blanusˇa 2003;Rome´o et al. 1999; Zauke et al. 1999). These metals tend todistribute differentially in liver and muscle, most likelybecause of metal-binding proteins such as metallothioneinsin certain organs of fish (Atli and Canli 2003; De Smetet al. 2001; Hamilton and Mehrle 1986; Roesijadi 1992).These proteins bind copper (Cu), cadmium (Cd), and zinc(Zn), but not lead (Pb), allowing organs such as the liver toaccumulate higher levels of metals than other organs suchas muscle.Only a few monitoring studies have measured heavymetals in fish species found in the Northern Gulf of Mexico(Feldhausen and Johnson 1983; Hanson 1997; Vazquezet al. 2001). The current study measured Pb, Cu, Cd, andZn levels in muscle fillet and liver of king mackerel(Scomberomorus cavalla), a large (>1,500-mm fork length)reef-associated fish that inhabits subtropical and tropicalwaters throughout the Gulf of Mexico. The S. cavalla is avery common sport and food fish (McEachran and Fech-helm 2005).Materials and MethodsMuscle fillets and livers of nine king mackerel (S. cavalla)were collected June 2003 from the Alabama Fishing Rodeoheld at Dauphin Island, Alabama, and sponsored by theJAYCEES of Alabama. All samples (fillet and whole liver)were placed in plastic freezer bags and transported to theUniversity of South Alabama, Mobile, Alabama. Theywere immediately frozen at –80 C.Methods for extracting heavy metals from tissue sam-ples were derived from the U.S. Environmental ProtectionAgency (EPA) standard method 3051 (U.S. EPA 1994).Approximately 0.5 g of wet tissue was placed in a 45-mLTeflon insert with 5 mL of ultra pure nitric acid. A separate0.5-g section from each tissue sample was oven driedovernight at 65 C for determination of dry:wet weight ra-tios. Teflon inserts were capped, placed into Parr micro-wave digestion bombs (Parr Instrument Company, Moline,IL, USA), and heated in a microwave. Tissues were di-gested for 3 min at 700 W. The digestate was diluted to10% of the original volume by adding 45 mL of deionizedwater.To monitor the extraction efficiency of the precedingtechnique, 0.25-g dry weight samples of one of two Na-tional Institute of Standards and Testing standard referencematerials, #2976 mussel tissue or #1566b oyster tissue,were digested as described. The percentage of recovery forall metals exceeded 85% of certified values. Levels of Pb,Cu, and Cd were analyzed using a Varian SpectrAA220graphite furnace atomic absorption spectrophotometer(Varian Inc., Palo Alto, CA, USA). Levels of Zn wereanalyzed with a Perkin-Elmer flame atomic absorptionspectrophotometer (Perkin-Elmer, Waltham, MA, USA)because this metal tends to be high in biologic samples.Student’s t-tests (df = 16;