Differential recovery of δ¹³C in multiple tissues of white sucker across age classes after the closure of a pulp mill

Abstract

Techniques to document recovery after the closure of pulp mills that discharge enriching effluents are not well established, but ␦ 13 C may be a useful tool. In the 1990s, the muscle tissue of white sucker (Catostomus commersonii) collected downstream of two pulp and paper mills discharging into separate streams (Mattagami and Kapuskasing rivers) was enriched in 13 C compared with upstream fish, suggesting uptake of pulp-derived C. The Mattagami River mill was closed in 2006, and analysis of muscle and gonad for ␦ 13 C was performed in 2011. As expected, fish captured in 2011 downstream of the operational Kapuskasing mill still showed the influence of the pulp-derived C in muscle and gonad tissue. After the closure of the Mattagami River mill, muscle tissue of white sucker was still enriched in 13 C compared with upstream fish, while gonad tissue was not. The patterns observed in the Mattagami River were, however, related to age; the oldest fish showed enrichment of ␦ 13 C in both muscle and gonad tissue, suggesting the residual occurrence of pulp-derived C. This study suggests that measurements of stable isotopes in fish across a broad age range may indicate ecosystem improvements. These techniques may also be useful where no data prior to the upgrade or closure are available for comparison.Résumé : S'il n'y a pas de technique bien établie pour documenter le rétablissement après la fermeture d'usines de pâte qui relâchent des effluents enrichissants, le ␦ 13 C pourrait s'avérer utile. Dans les années 1990, des tissus musculaires de meuniers noirs (Catostomus commersonii) prélevés en aval de deux usines de pâte et papier relâchant des effluents dans des ruisseaus différentes (Mattagami et Kapuskasing) étaient enrichis en 13 C par rapport à ceux de poissons en amont des usines, semblant indiquer une absorption de C provenant de la pâte. L'usine sur la rivière Mattagami a fermé ses portes en 2006, et les analyses ont été répétées en 2011. Comme prévu, leurs muscles et gonades de poissons capturés en aval de l'usine toujours en exploitation sur la rivière Kapuskasing présentaient encore une influence du C provenant de la pâte. Après la fermeture de l'usine de la rivière Mattagami, les tissus musculaires de meuniers noirs étaient toujours enrichis en 13 C par rapport à ceux de poissons en aval, alors que les tissus gonadiques ne l'étaient pas. La distribution du 13 C observée dans la rivière Mattagami était toutefois reliée à l'âge, les muscles et les gonades de poissons plus vieux présentant un enrichissement du ␦ 13 C, suggérant la présence résiduelle de C provenant de la pâte. L'étude donne à penser que la mesure d'isotopes stables dans des poissons d'âges très variés pourrait permettre de documenter l'amélioration d'écosystèmes. Ces techniques pourraient également être utiles quand aucune donnée antérieure à la mise à niveau ou la fermeture n'est disponible pour des fins de comparaison. [Traduit par la Rédaction]

Regional and Long-Term Analyses of Stable Isotopes of Fish and Invertebrates Show Evidence of the Closure of a Pulp Mill and the Influence of Additional Stressors

“…However, the influence of both PME and impoundments on δ 13 C are similar in direction, but may differ by magnitude. As in other studies, fish living downstream of pulp mill discharges in the Moose River Basin had more enriched δ 13 C values compared with those captured at upstream locations (Wassenaar and Culp 1994), an effect that was attributed to inputs of terrestrial carbon in the effluents (Wassenaar and Culp 1994; Lowell et al 1995; Dubé et al 2005; Arciszewski et al 2014). Whereas terrestrial carbon from the mills was expected to enrich δ 13 C at both of the Mattagami and Kapuskasing downstream sites, there was also a coincidental influence of the upstream hydroelectric dams: impoundments are known to affect the δ 13 C of resident species (Freedman et al 2014).…”

“…The δ 13 C values in white sucker muscle, however, remained enriched, but the source of the enrichment likely shifted from both the PME and the dam during the 1990s, to only the dam in the 2010s. Although some residual influence of the PME at Mattagami downstream may be possible, the signal is likely marginal (Arciszewski et al 2014). A similar dam‐only signal was also observed in δ 13 C of white sucker collected in the Groundhog River that was independent of any PME.…”

“…Effluent was discharged 0.15 km downstream of the dam by 2 submerged multiport diffusers at a rate of 0.8 m 3 /s. Operations and effluent releases stopped in July 2006 when the mill was permanently closed (Arciszewski et al 2014). The mill was dismantled in 2008, and only the hydroelectric dam remains at the Smooth Rock Falls site.…”

“…Discharge of effluents from pulp mills is often associated with a variety of changes in receiving environments, such as impacts on reproductive development in fish and evidence of nutrient enrichment in fish and invertebrates (Munkittrick et al 1991; Lowell et al 2005). The relative abundances of naturally occurring stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) have been used as tracers of terrestrial carbon and other nutrients that are released in pulp mill effluents (PMEs) and incorporated into the tissues of aquatic biota (Wassenaar and Culp 1994; Lowell et al 1995; Farwell 2000; Wayland and Hobson 2001; Dubé et al 2005; Arciszewski et al 2014). The terrestrial carbon from the pulping process can be distinct in its δ 13 C from autochthonous sources within the river (Wayland and Hobson 2001), and, if so, the assimilation of this nutrient source by downstream invertebrates and fishes can be determined (DeNiro and Epstein 1981; Wassenaar and Culp 1994; Farwell 2000).…”

“…Although incorporation of enriched nutrients from PMEs into the food web has been examined (e.g., Culp and Lowell 1998; Wayland and Hobson 2001), the timing and magnitude of isotopic change once discharges are discontinued are less certain. One study found age‐related changes in δ 13 C following the closure of a pulp mill where older fish had residual pulp‐derived δ 13 C values in muscle and gonad tissues, whereas fish that reached maturity after the closure of the mill did not (Arciszewski et al 2014). A second study found depleted δ 15 N and enriched δ 13 C of invertebrates exposed to effluents from a pulp mill following a 9‐mo closure in 2011, and a reversal of that response in 2013, 10 mo after the re‐opening of a pulp mill (Mendoza 2016).…”