Responses of Shortfin Eel (Anguilla Australis) Exposed In Situ to Pulp and Paper Effluent

Abstract

The responses of shortfin eel (Anguilla australis) to discharges from two pulp and paper mills, municipal wastewater, and a geothermal power plant wastewater were examined. Eels were caged at 3 sites along the Tarawera River, North Island, New Zealand, to explore effects of a 3-wk exposure down a contamination gradient (Ref → D1 → D2). Most of the observed effects were seen in eels caged at the furthest downstream site (D2), below all the discharge areas. General hematology in eels was unaffected, as measures did not differ markedly at the two downstream sites compared with the reference site. At D2, eels were significantly lighter per unit length (reduced condition factor), although liver and spleen size (LSI and SSI) were unaffected. Significantly elevated circulating sex steroid concentrations (testosterone and estradiol) were measured in D2 eels and increasing sex steroid levels at both sites downstream of the reference site were observed. Significant ethoxyresorufin O-deethylase (EROD) activity induction was seen in D2 eels and bile chemistry showed significant accumulation of pyrene and retene equivalents. However, significantly greater concentrations of total resin acids were found in the bile of eels from the intermediate site (D1), between the two pulp and paper mills. The higher polycyclic aromatic hydrocarbon (PAH) equivalents found in the bile of D2 eels suggest that resin acid neutrals, particularly retene, are responsible for some of the effects observed in eels at the furthest downstream exposure site. Levels of pulp and paper mill extractives in sediment, including the PAH retene, support this conclusion.

Funding for this research was obtained through the Sustainable Management Fund from the New Zealand Ministry for the Environment, Norske Skog Tasman Mill, Environment Bay of Plenty, Carter Holt Harvey Consumer Brands, and the Foundation for Research, Science and Technology. The authors thank David West, Megan Finley, Katherine Trought, Ian Kusabs, Tairua Whakaruru, Don Jellyman, Glenn Ellery, and Dana Thompson for their assistance, and Christine Bezar for editorial comments. All fish manipulations were done in accordance with Forest Research Code of Ethical Conduct for the handling of animals and the New Zealand Animal Welfare Act (1999).

Notes

Ataria, J. 2001. The development of biological effects based tests in eels and mice and their application. PhD thesis, Lincoln University, Lincoln New Zealand