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An evaluation of sodium loss and gill metal binding properties in rainbow trout and yellow perch to explain species differences in copper tolerance
Author(s) -
Taylor Lisa N.,
Wood Chris M.,
McDonald D. Gordon
Publication year - 2003
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/02-256
Subject(s) - rainbow trout , perch , copper , soft water , gill , toxicity , biotic ligand model , copper toxicity , trout , biology , saturation (graph theory) , environmental chemistry , metal , sodium , zoology , toxicology , chemistry , fishery , fish <actinopterygii> , mathematics , organic chemistry , combinatorics
The main objective of the study was use a species comparison approach in order understand sensitivity and tolerance differences to copper. We hypothesized that species differences in toxicity would be reflected by differences in copper binding to high‐affinity sites on the gill. Specifically, the strength of copper binding (affinity, log K ) and maximum number of binding sites (saturation, B max ) for copper at the gill surface would vary among different species of fish. Two species that are different in their copper sensitivity are the rainbow trout ( Oncorhynchus mykiss ) and yellow perch ( Perca flavescens). We explicitly compared acute toxicity (median lethal concentrations via 96‐h LC50s) and whole‐body Na + loss in both organisms in two distinct water chemistries (i.e., hard and soft water). For both species, the copper binding sites at the gill surface were characterized for their affinity and saturability. The binding properties of the gill were quite similar between the two species in each water chemistry. Based on estimations of the free cupric ion concentration, the affinity, or log K , was 8.4 for both species in soft water, whereas in hard water, the affinity was higher (˜9.7). The B max value in soft water was 1.88 nmol/g for rainbow trout and yellow perch, while in hard water, saturation occurred at 3.63 nmol/g for rainbow trout and 9.01 nmol/g for yellow perch. More importantly, the amount of copper bound to the gills at 50% mortality (i.e., lethal accumulation; the LA50) was different between the two species (yellow perch LA50s were nine times higher than those of rainbow trout in soft water and hard water), indicating that the copper binding to the yellow perch gill must not have been ‘biologically reactive.’ According to 96‐h LC50s, yellow perch were less sensitive to copper than were rainbow trout; however, the difference between the two species was similar in hard water (1.05 vs 4.16 μM) and soft water (˜0.10 vs 0.44 μM). Perch were more tolerant because they lost less sodium upon exposure to copper; yet this mechanism of tolerance was not reflected by the amount of copper at the gill surface. The influence of water chemistry on the binding properties of the gill demonstrates the dynamic nature of the gill in maintaining ionoregulatory homeostasis, a key issue in the future development of the chronic biotic ligand model.