Acclimation and deacclimation of brown trout (Salmo trutta) to zinc and copper singly and in combination with cadmium or copper.

Brown trout (Salmo trutta) were chronically exposed to low and high levels of zinc (Zn) alone, copper (Cu) alone, a Zn-Cu mixture, and a Zn-cadmium (Cd) mixture all starting with eyed eggs and continuing through to the fingerling stage. Exposure to the metals and metal mixtures resulted in acclimation as measured by greater median lethal concentrations (LC50) values relative to metal-naïve fry. The degree of acclimation was similar between the low and high exposures except for Cu, where acclimation was observed at the high but not the low acclimation level. The increases in tolerance relative to metal-naïve controls were usually less than a factor of 2 and never exceeded a factor of 3. Acclimation exposures did not affect hatch or survival except for the high-acclimation regime of Zn plus Cu. Acclimation came at an apparent metabolic cost because growth was decreased by most acclimation exposures. Deacclimation, as evidenced by a return of LC50 values to naïve levels, occurred after 2-5 weeks in clean water.

Reproductive disruption in fish downstream from an estrogenic wastewater effluent.

To assess the impact of an estrogenic wastewater treatment plant (WWTP) effluent on fish reproduction, white suckers (Catostomus commersoni) were collected from immediately upstream and downstream (effluent site) of the city of Boulder, CO, WWTP outfall. Gonadal intersex, altered sex ratios, reduced gonad size, disrupted ovarian and testicular histopathology, and vitellogenin induction consistent with exposure to estrogenic wastewater contaminants were identified in white suckers downstream from the WWTP outfall and not at the upstream site. The sex ratio was female-biased at the effluent site in both the fall of 2003 and the spring of 2004; the frequency of males at the effluent site (17-21%) was half that of the upstream site (36-46%). Intersex white suckers comprised 18-22% of the population at the effluent site. Intersex fish were not found at the upstream site. Chemical analyses determined that the WWTP effluent contained a complex mixture of endocrine-active chemicals, including 17beta-estradiol (E2) 17alpha-ethynylestradiol, alkylphenols, and bisphenol A resulting in an estimated total estrogen equivalence of up to 31 ng E2 L(-1). These results indicate that the reproductive potential of native fishes may be compromised in wastewater-dominated streams.

Intersex and other reproductive disruption of fish in wastewater effluent dominated Colorado streams.

Intersex white suckers (Catostomus commersoni) were collected in Boulder Creek and the South Platte River downstream of wastewater treatment plant (WWTP) effluent but not at reference sites. Eighty-three percent of the 60 white suckers collected downstream of the Boulder WWTP in spring and fall were female compared to 45% upstream (n=33). Only female (n=16) and intersex white suckers (n=4) were collected in the South Platte River downstream of the Denver WWTP in the spring. Gonad deformities and delayed follicular maturation were noted in some white suckers in Boulder Creek and the South Platte River downstream of the WWTP effluents. Asynchronous ovarian development was found in some female white suckers downstream of the WWTP effluents, but not upstream. The types and extent of sexual disruption differed in each river studied.