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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03555

    Biological and anthropogenic influences on macrophage aggregates in white perch Morone americana from two tributaries of Chesapeake Bay, USA

    Mark A. Matsche*, Vicki S. Blazer, Erin L. Pulster, Patricia M. Mazik

    *Corresponding author:

    ABSTRACT: Total volume of macrophage aggregates (MAV) was estimated in the liver and spleen of white perch Morone americana from Chesapeake Bay using stereological approaches. Hepatic and splenic MAV were compared between fish populations from the Choptank River (n = 122), a tributary with extensive watershed agriculture, and the Severn River (n = 131), a tributary with extensive watershed development. Hepatic and splenic MAV increased with fish age, were greater in females from the Severn River only, and were significantly greater in fish from the more polluted Severn River (higher concentrations of polycyclic aromatic hydrocarbons, organochlorine pesticides, and brominated diphenyl ethers). Water temperature and dissolved oxygen had a significant effect on organ volumes, but not on MAV. Modeling results indicated that age and river were most influential on hepatic and splenic MAV, suggesting that increased MAV in Severn River fish resulted from chronic exposures to higher concentrations of environmental contaminants and other stressors. Hemosiderin was abundant in 97% of spleens and was inversely related to fish condition and positively related to fish age and trematode infections. Minor amounts of hemosiderin were detected in 30% of livers and positively related to concentrations of benzo[a]pyrene metabolite equivalents in the bile. This study demonstrated that hepatic and splenic MAV were useful indicators in fish from the two tributaries with different land use characteristics and concentrations of environmental contaminants. However, more data are needed from multiple seasons and from a range of tributaries with a wider gradient of environmental impacts to validate these results in this species.