title: Assessing mercury exposure and biomarkers in largemouth bass (Micropterus salmoides) from a contaminated river system in California.
abstract: We evaluated mercury (Hg) exposure and two biomarkers, metallothionein (MT) gene expression and histopathological alterations in a wild fish species, largemouth bass (Micropterus salmoides), collected from the Sacramento-San Joaquin Delta, CA, a region polluted with Hg from historic mining activities. Hg is highly toxic and can disrupt multiple physiological systems in vertebrate species, including the immune system. Total mercury (THg) concentration in muscle tissue ranged from 0.12 to 0.98 ppm (wet weight) and was not related to body condition (r (2) = 0.005, p = 0.555). Using linear regression analysis, we found a positive relationship between MT gene expression (as determined using quantitative polymerase chain reaction) and copper, zinc, manganese, aluminum, and nickel (decreased to one variable by way of principal component analysis) (r (2) = 0.379, p = 0.044), a negative relationship with selenium (r (2) = 0.487, p = 0.017), and a weak, negative relationship with THg concentrations (r (2) = 0.337, p = 0.061). Juvenile largemouth bass collected from Hg-contaminated areas displayed histopathological features of immunosuppression compared with those collected from less contaminated areas as evidenced by significantly lower macrophage density in kidney and liver tissue (p = 0.018 and 0.020, respectively), greater trematode density in liver tissue (p = 0.014), and a greater number of adult trematodes. Our results suggest that largemouth bass may be experiencing sublethal effects from chronic Hg exposure. Furthermore, our findings illustrate the utility of examining multiple sublethal markers of effect to assess the impacts of contaminant exposure on physiological function in wild species.
authors.affiliation: Moss Landing Marine Laboratories, 8272 Moss Landing Rd, Moss Landing, CA 95039, USA. dmolin@dtsc.ca.gov
authors.forename: Daphne B
authors.initials: DB
authors.lastname: Gehringer
authors.forename: Myra E
authors.initials: ME
authors.lastname: Finkelstein
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Coale
authors.forename: Mark
authors.initials: M
authors.lastname: Stephenson
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Geller
mesh_terms: D000375:Aging / Q000276:immunology / Q000378:metabolism; D000818:Animals; D001492:Bass / Q000276:immunology / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002140:California; D004781:Environmental Exposure / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D015870:Gene Expression / Q000187:drug effects; D007668:Kidney / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D016014:Linear Models; D008099:Liver / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D008628:Mercury / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity; D008668:Metallothionein / Q000235:genetics; D045483:Rivers / Q000737:chemistry*; D013154:Spleen / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D014131:Trace Elements / Q000032:analysis / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D015415:Biomarkers; D014131:Trace Elements; D014874:Water Pollutants, Chemical; D008668:Metallothionein; D008628:Mercury