Fathead minnow response to broad-range exposure of ß-sitosterol concentrations during life-cycle testing.

The ß-sitosterol concentration in pulp and paper mill effluents is typically greater than that of other phytosterols and has been shown to cause a variety of effects in fish. The authors exposed fathead minnow (Pimephales promelas) to low (22 ± 0.93 µg/L), medium-low (70 ± 2.1 µg/L), medium-high (237 ± 5.5 µg/L), and high (745 ± 16.2 µg/L) concentrations of ß-sitosterol as well as negative (water), positive (ethynyl estradiol, 16 ± 0.58 ng/L), and carrier (0.6 mL/L acetone) controls. Fish were monitored over a full life cycle for population-level endpoints including growth and survival, reproductive endpoints (e.g. fecundity, sex steroids and vitellogenin, gonado-/hepatosomatic indices, and gonad histology). No significant differences were seen in fish growth, mortality, or reproduction with ß-sitosterol exposure, although a trend for lower egg production in ß-sitosterol exposures relative to the water control may be related to the acetone carrier. All ethynyl estradiol-exposed fish were smaller, showed female characteristics, and did not spawn. Sex steroid and vitellogenin were highly variable with no detectable treatment-related differences. Gonadal tissue showed no ß-sitosterol-related differences in reproductive development and spawning capability, although most ethynyl estradiol-exposed males had ovarian tissue and were not spawning-capable. The results indicate that ß-sitosterol exposure had little apparent impact on fathead minnow survival, growth, and reproduction even at concentrations >10 times that of typical effluents, although small sample size and variability precluded fully evaluating treatment responses on sex steroids and vitellogenin.

Responses of fathead minnows (Pimephales promelas) during life-cycle exposures to pulp mill effluents at four long-term receiving water study sites.

We exposed fathead minnows (Pimephales promelas to 7 concentrations of effluents from pulp mills at 4 Long-Term Receiving Water Study (LTRWS) sites. The primary objective of these investigations was to determine the potential for toxicity, particularly on fish reproduction, of the pulp mill effluents using laboratory tests. These tests were performed as LTRWS fish community assessments were being completed, thus results of the laboratory fish reproduction tests could be compared to in-stream fish community measurements. In general, bioindicators measured during the life-cycle tests, including gonadosomatic index (GSI), hepatosomatic index, condition factor, numbers of tubercles on heads of males and females, and gonadal histology did not show consistent patterns or dose response and did not predict effects on egg production. Gonadosomatic indexes and tubercles also did not indicate estrogenic or androgenic responses to the effluents during the life-cycle tests. The most consistently sensitive test endpoint showing a dose response was the 25% inhibition concentration (IC25) for egg production. Based on this endpoint all 4 effluents had effects on fish reproduction from 8% by volume to 100% effluent. However, in-stream effects on fish reproduction would not be expected based on these 4 life-cycle tests for any of the LTRWS stream sites. The mean effluent concentration in Codorus Creek, Pennsylvania, USA was approximately 32%, and the IC25 for the life-cycle test was 100% effluent, providing a margin of safety of approximately 3 times. The margins of safety at the other sites are much greater: 34 times for Leaf River, Mississippi, USA (IC25 = 69%, 2% mean receiving water concentration), 36 times for the McKenzie River, Oregon, USA (IC25 = 18%, 0.5% mean receiving water concentration), and 40 times for the Willamette River, Oregon, USA (IC25 = 8%, 0.20% mean receiving water concentration). Effects on fish numbers, diversity, and community structure due to the effluent were also not found during the LTRWS, which is consistent with these laboratory results. These findings indicate that in this case, when laboratory results combined with in-stream effluent concentrations suggest in-stream effects on fish population are not expected, the laboratory results are consistent with the in-stream observations. However, inferences about situations where laboratory results predict in-stream effects cannot be made from these data.

A long-term, multitrophic level study to assess pulp and paper mill effluent effects on aquatic communities in four US receiving waters: characteristics of the study streams, sample sites, mills, and mill effluents.

Watershed characteristics, study streams, sample sites, mills, and mill effluents are provided for 4 streams included in a long-term study to assess potential effects of pulp and paper mill effluents on US receiving waters. The study streams are Codorus Creek (Pennsylvania, USA), Leaf River (Mississippi, USA) and McKenzie and Willamette rivers (Oregon, USA) and were chosen to represent a blend of mill process types, effluent concentrations, and coldwater/warmwater stream systems. The described effluent quality, water quality, and habitat data sets encompass the initial 7 to 8 y of a study anticipated to continue >10 y and provide a backdrop to a series of articles describing periphyton, macroinvertebrate, and fish community properties in these same streams. The mean in-stream waste concentration (IWC) for these 4 effluent discharges was 32.4%, 2.0%, 0.5%, and 0.2% v/v for Codorus Creek and Leaf, McKenzie, and Willamette rivers, respectively, as compared with a median of 0.4% for US mills. Effluent quality measurements included Selenastrum capricornutum, Ceriodaphnia dubia, and Pimephales promelas chronic bioassays as sanctioned by the US Environmental Protection Agency for estimating effluent effects on receiving-water aquatic communities. Based on mean bioassay inhibition concentration for a 25% effect and on mean IWC, a margin of safety against adverse biological effects of 2, 25, 137, and 150 times was indicated for Codorus Creek and Leaf, McKenzie, and Willamette rivers, respectively. Habitat and water quality assessment was carried out over a gradient of sample sites above and below the effluent discharge to determine nonmill-related conditions that might interfere with interpretation of effluent effects. Noneffluent related localized differences in conditions for some parameters, including current velocity (McKenzie River), and surface incident photosynthetically active radiation (Codorus Creek and Willamette River) occurred at the sample stations immediately upstream or downstream of the effluent discharge. In addition, broader watershed differences were evident on Codorus Creek, where a relatively rich riparian corridor and stream structure occurred upstream in contrast to areas of canopy and stream-structure loss in the downstream urban area. The mill effluent discharges contributed to increases in receiving-water color and conductivity, although upstream tributaries contributed additional conductivity to Codorus Creek and color to the Leaf River. The McKenzie River provided the only example of a nutrient increase immediately downstream of a mill discharge. This increase in total nitrogen (0.11 vs 0.16 mg/L) could not, however, be differentiated with respect to whether it was of mill effluent or tributary stream origin. Tributary streams were potentially important total nitrogen contributors on Codorus Creek and the Willamette River. As an integrated study, the effluent quality and physical/chemical watershed descriptions provided here represent 1 component of the broader study addressing potential point-source effluent effects within the context of the larger watershed and a multiyear timescale. The absence of effluent-related in-stream chemical/physical responses, other than increases in conductivity and color, and a considerable bioassay-based margin of safety, provides for a working hypothesis that there will be no effluent-related biological population/community responses from these 4 mill discharges. This hypothesis, as it relates to periphyton, macroinvertebrate, and fish communities, will be addressed in other articles in this series.