Biomonitoring of Environmental Status and Trends (BEST) Program environmental contaminants, health indicators, and reproductive biomarkers in fish from the Colorado River basin

Hinck, J.; Blazer, V.; Denslow, N.; Gross, T.; Echols, K.; Davis, A.; May, T.; Orazio, C.; Coyle, J.; Tillitt, D.

Seven fish species were collected from 14 sites on rivers in the Colorado River Basin (CDRB) from August-October 2003. Spatial trends in the concentrations of accumulative contaminants were documented and effects on the fish were assessed. Sites were located on the mainstem of the Colorado River and on the Yampa, Green, Gunnison, San Juan, and Gila Rivers. Common carp (Cyprinus carpio), black bass (Micropterus sp.), and channel catfish (Ictalurus punctatus) were the targeted species. Fish were examined for anomalies, selected organs were weighed to compute somatic indices, and tissue and fluid samples preserved for fish health and reproductive biomarker analyses. Composite samples of whole fish, grouped by species and gender, from each site were analyzed for organochlorine and elemental contaminants using performance-based and instrumental methods. 2,3,7,8-tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ) was measured using the H4IIE rat hepatoma cell bioassay. Selenium (Se) and mercury (Hg) concentrations were elevated throughout the CDRB, and pesticides concentrations were greatest in fish from agricultural areas in the Lower Colorado River and Gila River. Selenium concentrations exceeded toxicity thresholds for fish (>1.0 µg/g ww) at all sites except from the Gila River at Hayden, AZ. Mercury concentrations were elevated (>0.1 µg/g ww) in fish from the Yampa River at Lay, CO; the Green River at Ouray National Wildlife Refuge (NWR), UT and San Rafael, UT; the San Juan River at Hogback Diversion, NM; and the Colorado River at Gold Bar Canyon, UT, Needles, CA, and Imperial Dam, AZ. Concentrations of p,p’-DDE were relatively high in fish from Arlington, AZ (>1.0 µg/g ww) and Phoenix, AZ (>0.5 µg/g ww). Concentrations of other banned pesticides including toxaphene, total chlordanes, and dieldrin were also greatest at these two sites but did not exceed toxicity thresholds. Current-use or unlisted pesticides such as dacthal, endosulfan, γ-HCH, and methoxychlor were also greatest in fish from Gila River. Total polychlorinated biphenyls (PCBs; >0.11 µg/g ww) and TCDD-EQs (>5 pg/g ww) exceeded wildlife guidelines in fish from the Gila River at Phoenix, AZ. Hepatic ethoxyresorufin O-deethylase (EROD) activity was also relatively high in carp from the Gila River at Phoenix, AZ and in bass from the Green River at Ouray NWR, UT. Altered biomarkers were noted in fish throughout the CDRB. Multiple fish health indicators including altered body and organ weights and high health assessment index scores may be associated with elevated Se concentrations in fish from the Colorado River at Loma, CO and Needles, CA. Although grossly visible external or internal lesions were found on most fish from some sites, histopathological analysis determined many of these to be inflammatory responses associated with parasites. Edema, exophthalmos, and cataracts were noted in fish from sites with elevated Se concentrations. Reproductive biomarkers were anomalous in fish from the Gila River at Hayden and Phoenix, AZ. In addition, intersex fish were found at seven of 14 sites. The intersex condition was identified in smallmouth bass (M. dolomieu), largemouth bass (M. salmoides), channel catfish, and carp and may indicate exposure to endocrine disrupting compounds. Male carp, bass, and channel catfish with low concentrations of vitellogenin were common in the CDRB. Comparatively high vitellogenin concentrations (>0.2 mg/mL) were measured in male fish from the Green River at Ouray NWR, UT and the Colorado River at Imperial Dam, AZ and may indicate exposure to estrogenic chemicals. Biomarker responses may be associated with industrial and municipal discharges, mining operations, irrigated agriculture, and atmospheric deposition. Continued biological monitoring is warranted to identify consistently degraded sites and those with emerging problems in the CDRB.

Biomonitoring of Environmental Status and Trends (BEST) Program environmental contaminants, health indicators, and reproductive biomarkers in fish from the Colorado River basin

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