Reproductive disruption in wild longear sunfish (Lepomis megalotis) exposed to kraft mill effluent

Abstract

Worldwide, wild fish living in rivers receiving municipal and industrial discharges may experience endocrine disruption as a result of exposure to anthropogenic pollutants. The purpose of this study was to evaluate the hormonal status of wild fish in a U.S. river receiving unbleached kraft and recycled pulp mill effluent (Pearl River at Bogalusa, LA). We evaluated two alternative hypotheses: the effluent contained constituents that suppressed male and female reproduction, or it contained an androgenic substance that masculinized females. To evaluate the likelihood of fish exposure to effluent, we marked 697 longear sunfish (Lepomis megalotis) over a 2-year period; 83% of recaptured fish were found at the site of initial capture, and only one fish migrated from an effluent-receiving site to a reference site. We can reasonably assume that fish captured from an effluent-receiving site are residents, not transitory migrants. To diagnose endocrine disruption, we measured sex steroid hormone [17beta-estradiol (E2), testosterone (T), and 11-ketotestosterone (11KT)] and vitellogenin (VTG) concentrations in male and female longear sunfish captured at two sites upstream and two sites downstream of the effluent outfall. Kraft pulp mill effluent did not affect male reproductive physiology but did suppress female T and VTG levels when effluent constituted>or=1% of river flow. Masculinization was not observed. Longear sunfish in the Pearl River experience moderate reproductive suppression in response to unbleached kraft and recycled pulp mill effluent.

Figure 1

Site locations along the Pearl River near Bogalusa, Louisiana. Outfall, site of wastewater discharge into the Pearl River (river flows south). Map was adapted from the USGS Bogalusa East, LA-MS map, USGS entity ID MPTLA0072PP01, 1997.

Figure 2

Male longear sunfish sampled from the Pearl River near Bogalusa, Louisiana. (A) 11KT. (B) T. Numbers below the x-axis indicate sample sizes for each site on each date. Both androgens increased with body size and varied significantly over time, but did not differ between sites. Values are mean ± SEM.

Figure 3

Male longear sunfish sampled from the Pearl River near Bogalusa, Louisiana. (A) VTG. (B) E₂. Neither VTG nor E₂ varied with body size or between sites, but both parameters showed significant seasonal variation. Sample sizes for each site on each date are shown in Figure 2B. Values are mean ± SEM.

Figure 4

Female longear sunfish sampled from the Pearl River near Bogalusa, Louisiana. (A) VTG. (B) E₂. (C) T (note logarithmic scale). All three parameters varied significantly over time. Numbers below the x-axis indicate sample sizes for each site on each date. E₂ was similar between sites; VTG was significantly lower at the downstream site in 2002 when effluent concentration exceeded 1% of river flow; and T was significantly lower in females sampled at the downstream site. Values are mean ± SEM.

Figure 5

Female longear sunfish sampled from the Pearl River near Bogalusa, Louisiana. 11KT varied significantly over time, but not between sites. Sample sizes for each site on each date are shown in Figure 4C. Values are mean ± SEM.