Bioindicators of stress in fish in Biscayne Bay: Stress protein 70 and melanomacrophage aggregates

Biscayne Bay is a moderately contaminated, subtropical estuary in Southeastern Florida. Major sources of contamination to Biscayne Bay include non-point source pollutants funneled to the Bay via the Miami River and other canals. Different sites in the Bay have different levels of contamination which have been shown to correlate with bioindicators including the prevalence of morphological abnormalities in fish. The objectives of this study were to review bioindicators in Biscayne Bay and to examine of the utility of two bioindicators, stress protein 70 in liver and gill of gray snapper, Lutjanus griseus, and melanomacrophage aggregates (MMA) in spleens of gray snapper and pinfish, Lagodon rhomboides. Stress protein 70 was induced in the laboratory in gray snapper in response to heat. Levels of stress protein 70 (inducible and constitutive) in liver and gill of gray snapper collected from natural populations at contaminated and reference sites in Biscayne Bay varied considerably and either did not reflect contamination or reflected other environmental conditions in addition to contamination such that the level of the stress protein 70 could not be attributed to contamination. These results indicate that stress protein 70 would not be useful as evidence fish are negatively impacted at contaminated sites or to document exposure in Biscayne Bay. MMAs in gray snapper spleens became significantly smaller and significantly more numerous when fish in the laboratory were exposed to copper. Gray snapper and pinfish collected from natural populations at contaminated sites also had significantly more numerous and, sometimes, smaller MMAs than fish from reference sites. More numerous MMAs were therefore considered evidence of exposure. In addition, variability between individual fish in number of MMAs was greater at the contaminated sites. Thus, MMAs may be a useful bioindicator for documenting exposure to contamination in Biscayne Bay.