Premium
Contrasting Pathways of Assimilation
Author(s) -
Dubé Monique G.,
Benoy Glenn A.,
Wassenaar Leonard I.
Publication year - 2006
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2005.0122
Subject(s) - assimilation (phonology) , environmental chemistry , chemistry , effluent , rainbow trout , trophic level , muscle tissue , biology , fish <actinopterygii> , ecology , fishery , environmental science , environmental engineering , anatomy , philosophy , linguistics
Fish are commonly used for monitoring the quality of waters receiving pulp mill effluents (PMEs). Isotopic assays of fish tissues have the potential to provide empirical evidence to link an effluent source to exposure. We show in a 45‐d factorial laboratory experiment that different exposure pathways lead to isotopic signatures in fish tissue. Rainbow trout ( Oncorhynchus mykiss ) were exposed to 10% PME in three ways; direct exposure through addition of PME to aquaria, indirect exposure through invertebrate food consumption ( Chironomus tentans cultured in 10% PME), and a combination of both exposure pathways. Of the four stable isotopes measured (δ 13 C, δ 15 N, δ 34 S, δ 37 Cl), δ 13 C, δ 34 S, and δ 37 Cl showed significant differences in exposed animal tissues. δ 37 Cl of fish muscle tissue showed consistent differences across trophic levels and revealed contrasting pathways of PME exposure. Contrasting δ 37 Cl values in C. tentans due to the presence or absence of 10% PME did not translate into δ 37 Cl differences in fish. Rather, δ 37 Cl ratios of fish muscle tissue were specifically related to 10% PME exposure in the aquaria (waterborne exposure pathway). Feasible distributions of 37 Cl source contributions for observed mixture ratios confirmed that PME accounted for observed differences in δ 37 Cl among treatments. Direct uptake of chloride ions across gill surfaces is the most likely pathway for assimilation of PME into fish tissues. Considering the variability of PMEs and receiving environments, use of a multi‐isotope approach is recommended for tracing exposure of fish. Use of 37 Cl should also be considered in light of its alternative assimilation pathway.