Abstract

Largemouth bass (Micropterus salmoides) and common carp (Cyprinus carpio) were collected from 13 sites in 4 river basins in the southeastern United States to document spatial trends in accumulative contaminants, health indicators, and reproductive biomarkers. Organochlorine residues, 2,3,7,8- tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ), and elemental contaminants were measured in composite samples of whole fish, grouped by species and gender, from each site. Fish were field-examined for external and internal anomalies, selected organs were weighed to compute somatic indices, and tissue and fluid samples were preserved for fish health and reproductive biomarker analyses.

Mercury concentrations in bass samples from all sites exceeded toxicity thresholds for mammals [>0.1 micrograms per gram wet weight (μg/g ww)], fish (>0.2 μg/g ww), and birds (>0.3 μg/g ww) and were greatest (>0.5 μg/g ww) in samples from the Alabama River at Eureka Landing, Alabama; the Mobile River at Bucks, Alabama; the Apalachicola River at Blountstown, Florida; the Savannah River at Sylvania, Georgia; and the Pee Dee River at Bucksport, South Carolina. Selenium concentrations were relatively high (>0.75 μg/g ww) in fish from the Tombigbee River at Lavaca, Alabama; the Mobile River at Bucks; and the Chattahoochee River at Omaha, Georgia compared to those from other sites. Concentrations of 2,2-bis (p-chlorophenyl)- 1,1-dichloroethylene (p,p’-DDE) were high in fish from the Chattahoochee River at Omaha and the Mobile River near Bucks, which was near a 2,2-bis (p-chlorophenyl)-1,1- dichloroethylene (DDT) formulating facility that historically discharged into the lower Mobile River.

Toxaphene concentrations in fish from the Flint River near Albany, Georgia (60-100 nanograms per gram (ng/g) ww) may pose a risk to fish. Concentrations of other formerly used (total chlordanes, dieldrin, endrin, aldrin, mirex, and hexachlorobenzene) and currently used (pentachlorobenzene, pentachloroanisole, dacthal, endosulfan, γ-HCH, and methoxychlor) organochlorine residues generally were low or did not exceed toxicity thresholds. Total polychlorinated biphenyls concentrations in samples from the Coosa River at Childersburg, Alabama; the Apalachicola River at Omaha; the Apalachicola River at Blountstown; and the Pee Dee River at Bucksport were >480 ng/g ww and may be a risk to piscivorous wildlife. Dioxin-like activity as measured by TCDD-EQ was greatest [>10 picograms per gram (pg/g)] in male fish from the Coosa River at Childersburg and the Mobile River at Bucks. Hepatic ethoxyresorufin O-deethylase activity generally was greatest in carp from the Mobile River Basin [means >10 picomols per minute per milligram of protein (pmol/min/mg)] and in bass from the Tombigbee River at Lavaca and Pee Dee River at Pee Dee, South Carolina (means >65 pmol/min/mg). Altered biomarkers were noted in fish from all basins.

The field necropsy and histopathological examination determined that fish from the Mobile River Basin generally were in poorer health than those from the other basins. In bass, health assessment index scores were correlated with mercury and p,p’-DDE concentrations. High health assessment index scores in Mobile River Basin fish were widespread and caused primarily by parasitic infestations, which were most severe in fish from the Tombigbee River at Lavaca and the Alabama River at Eureka Landing. Tumors were present in few fish (n = 5; 0.01%). Ovarian tumors of the same origin (smooth muscle) were present in two older carp from the Chattahoochee River near Omaha, Georgia and may be contaminant related. Reproductive biomarkers including gonadosomatic index, vitellogenin concentrations, and steroid hormone concentrations were anomalous in fish from various sites but were not consistently related to any particular chemical contaminant. Intersex gonads were identified in 47 male bass (42%) representing 12 sites and may indicate exposure to endocrine disrupting compounds. The incidence of intersex male bass was greatest in the Pee Dee River Basin and least severe in the Mobile River Basin. Male bass and carp with low concentrations of vitellogenin were common in all basins. Comparatively high vitellogenin concentrations [>0.35 milligram per milliliter (mg/mL)] in male fish from the Coosa River at Childersburg, the Savannah River at Sylvania, and the Pee Dee River at Rockingham and Bucksport indicate exposure to estrogenic or anti-androgenic chemicals.