PARENT SESSION
80 - Biomonitoring and Assessment
8:00 AM to 6:30 PM, Wednesday, 15 May 2002
Exhibition Area

(80-40) Use of stable isotopes to "fingerprint" industrial effluents and trace fish exposure for cumulative effects assessment.

Dubé, Monique^*,1, Wassenaar, Len¹, ¹ National Water Research Institute, Environment Canada, Saskatoon, Saskatchewan, Canada

ABSTRACT- Stable isotopes of carbon ( ¹³C) and nitrogen (¹⁵ N) have been used to describe food web relationships amongst organisms and food sources. Stable isotopes of sulfur (³⁴ S) and chloride (³⁷ Cl) have shown promise to illustrate exposure of aquatic biota to pulp mill effluent and chlorinated solvents, respectively. Our objective was to use a multi-stable isotope approach (¹³ C, ¹⁵ N, ³⁴ S, ³⁷ Cl) to: 1) characterize the isotopic signatures of Canadian pulp mill effluents; and 2) assess fish tissue assimilation of stable isotopes in a laboratory exposure. Effluents from 11 mills were collected and represented a cross section of mill process types and effluent treatment strategies. Analyses of the effluents showed isotopic signature ranges of -25.5 to -14.7 for ¹³ C, -4.0 to -2.6 for ¹⁵ N, -3.7 to 16.5 for ³⁴ S, and -1.7 to 0.8 for ³⁷ Cl. Each mill effluent had a distinct isotopic "fingerprint" demonstrated through principal components analyses. To assess tissue assimilation of isotopic signatures, hatchery-reared juvenile rainbow trout ( Onchorhynchus mykiss) were raised for 45 d in the laboratory under control conditions and after exposure to 10% pulp mill effluent. Fish within each treatment were fed chironomids (Chironomus tentans) cultured under either control conditions or under effluent exposed conditions (10%). Survival differed between control (100%) and effluent-exposed (56%) fish. Fish increased in wet weight (g) by 50% in both treatments over the exposure period. Signatures of ¹³ C and ¹⁵ N did not differ between control and effluent exposed chironomids, fish liver tissue or dorsal muscle. However,³⁷ Cl results showed some differences in exposed fish and chironomids. Using isotopes to "fingerprint" effluents shows promise for tracking sources contributing to aquatic pollution.

Key words: stable isotope, pulp mill effluent, rainbow trout, chironomus tentans