TY - JOUR
T1 - Physiological interactions of silver and humic substances in Daphnia magna
T2 - Effects on reproduction and silver accumulation following an acute silver challenge
AU - Glover, Chris N.
AU - Wood, Chris M.
N1 - Funding Information:
Tammie Morgan and Dr. Fernando Galvez are thanked for useful discussions. This work was supported by a NSERC Collaborative Research and Development Grant Project (CRDPJ 257740-02) with co-funding from Kodak Canada. CMW is supported by the Canada Research Chair program. Joe Gorsuch of Eastman Kodak Rochester, NY, USA is thanked for helpful comments on the manuscript.
PY - 2004/12
Y1 - 2004/12
N2 - Silver (Ag) in aquatic environments mediates its toxic actions by inhibiting sodium influx. Humic substances protect against silver toxicity by complexing the toxic, ionic form of the metal, but may also directly stimulate sodium influx in aquatic organisms. This study investigated the effects of silver and humic substances on the water flea Daphnia magna. Acute silver challenge (24 h; 1 μg L-1) and the chronic exposure to humic substances (Aldrich humic acid; 7 mg C L-1) had considerable influence on daphnid physiology and reproduction. In particular silver exposure in the absence of humic substances stimulated reproduction, resulted in enhanced adult mass, and altered both the response of the animal to subsequent silver exposure and a physiological surrogate measure of silver toxicity (whole body sodium concentration). The presence of humic substances countered the effects on adult mass and reproduction, returning these parameters to control levels. Humic substances also lowered silver body burden, but with significantly improved whole body sodium status than previously silver-exposed animals. These changes may distort the correlation between silver body burden and indicators of toxic action, an important tenet of site-specific risk assessment tools such as the biotic ligand model.
AB - Silver (Ag) in aquatic environments mediates its toxic actions by inhibiting sodium influx. Humic substances protect against silver toxicity by complexing the toxic, ionic form of the metal, but may also directly stimulate sodium influx in aquatic organisms. This study investigated the effects of silver and humic substances on the water flea Daphnia magna. Acute silver challenge (24 h; 1 μg L-1) and the chronic exposure to humic substances (Aldrich humic acid; 7 mg C L-1) had considerable influence on daphnid physiology and reproduction. In particular silver exposure in the absence of humic substances stimulated reproduction, resulted in enhanced adult mass, and altered both the response of the animal to subsequent silver exposure and a physiological surrogate measure of silver toxicity (whole body sodium concentration). The presence of humic substances countered the effects on adult mass and reproduction, returning these parameters to control levels. Humic substances also lowered silver body burden, but with significantly improved whole body sodium status than previously silver-exposed animals. These changes may distort the correlation between silver body burden and indicators of toxic action, an important tenet of site-specific risk assessment tools such as the biotic ligand model.
KW - Acclimation
KW - Biotic ligand model
KW - Chronic toxicity
KW - Dissolved organic carbon
KW - Hormesis
KW - Ion regulation
KW - Natural organic matter
KW - Sodium balance
UR - http://www.scopus.com/inward/record.url?scp=15944372891&partnerID=8YFLogxK
U2 - 10.1016/j.cca.2004.12.005
DO - 10.1016/j.cca.2004.12.005
M3 - Journal Article
C2 - 15683838
AN - SCOPUS:15944372891
SN - 1532-0456
VL - 139
SP - 273
EP - 280
JO - Comparative Biochemistry and Physiology - C Toxicology and Pharmacology
JF - Comparative Biochemistry and Physiology - C Toxicology and Pharmacology
IS - 4
ER -