Use of paired fathead minnow (Pimephales promelas) reproductive test. Part 2: Source identification of biological effects at a bleached kraft pulp mill

Abstract

Reproductive effects of pulp mill effluents on fish continue to be reported in Canadian waters. Spawning delays, reduced gonad size, and altered levels of sex steroid hormones have been found in both sexes of various fish species exposed to effluents. We initiated a project to identify the source/cause of such effects. In part 1 of this two-part series, we exposed mature adult fathead minnow (FHM; Pimephales promelas) for 21 d to final treated effluent (1% and 100% v/v) from a bleached kraft pulp mill in Terrace Bay (ON, Canada). Results suggested pulp mill effluent from this mill affected reproductive indicators in FHM and effects were dependent on effluent concentration, duration of exposure, and method of data analysis. The main objective of this paper was to use the FHM assay to identify waste stream sources within the mill that affect reproductive indicators. Various process streams were selected, characterized with respect to effluent chemistry and acute toxicity, and a subset was tested on-site with the 21-d FHM bioassay. Results showed that both the combined mill effluent (before secondary treatment) and the combined alkaline stream (CALK) caused both decreased spawning events (approximately 55% for both streams) and decreased egg production (28 and 74%, respectively), and the CALK stream resulted in significant male ovipositor development. By comparing response patterns we were able to identify the CALK stream as a source of compounds at this mill affecting reproductive indicators in FHM and highlight this stream for further toxicity identification evaluation.

Investigating the link between pulp mill effluent and endocrine disruption: Attempts to explain the presence of intersex fish in the Wabigoon River, Ontario, Canada

“…The short-term fathead minnow bioassay [5,6,19] requires a pre-exposure and exposure period, each of approximately 21 d in length. The pre-exposure trial was performed in the absence of effluent to establish baseline reproductive data and successful breeding pairs to be used in the exposure period.…”

“…Responses include disruption to physiological processes including: hepatic function, reproductive success, impaired development, and endocrine function [1]. In addition, decreases in reproduction have been noted in fish exposed to PME in Canada [2][3][4][5][6], and as reviewed by Belknap et al [7] also in Scandinavia, the United States, and New Zealand. Within Canada, 90% of the environmental effects monitoring (EEM) cycle two reports submitted to the federal government in 2000 found significant effects from PME on gonad size, liver size, and body condition factor [8,9].…”

Pulp and paper mill effluents induce distinct gene expression changes linked to androgenic and estrogenic responses in the fathead minnow (Pimephales promelas)

“…Male secondary sexual characteristics have been observed in females following much longer life-cycle tests with bleached sulfite mill effluent [26] or kraft mill effluent following secondary treatment [2,4], although not in all cases [7,13].…”

“…Similarly, female FHMs exposed to 100% effluent from a bleached kraft mill decreased the number of spawning events and produced fewer eggs, whereas exposure to both 1 and 100% effluent resulted in the development of ovipositors in male fish. Conversely, females exposed to 1% final effluent in the same study increased both egg production rate and LSI due to increased synthesis and deposition of vitellogenin (VTG), a protein required for egg production and a key biomarker of estrogenic exposure in aquatic toxicology [4].…”

“…Fish exposed to these effluents typically show increases in condition factor (K) and liver somatic index (LSI), but a decrease in gonadal somatic index (GSI) ( [1]; http://www.ec.gc.ca/inre-nwri/C5BD35C5-923F-4E1A-B5DA-3B1F527456E8/Synopsis_e.pdf; [2,3]). Other observed effects include altered steroid hormone levels and secondary sexual characteristics, and decreased fecundity and egg size [4]. To address these problems, over the past decade the pulp and paper mill industry has introduced effluent treatment technologies, such as removal of elemental chlorine from the paperbleaching process, that have collectively improved wastewater quality [5] and alleviated many of the negative effects of their operations on wild fish populations [3,5,6].…”