The effects of waterborne cations on 65Zn uptake, Zn toxicity, and relationships with Ca uptake were examined in juvenile rainbow trout, Oncorhynchus mykiss, in soft water. Whole-body Zn uptake (waterborne [Zn] = 100 μg·L-1 = 1.5 μM) was greatly reduced by a variety of cations. This reduction was directly related to the concentration of positive charges, regardless of which ion carried that charge. Thus, 1.0 mM Na+, K+, NH4/+, and N-methyl-D-glucamine+ and 0.5 mM Mg2+ (divalent) reduced Zn uptake to a similar extent (~50%), indicating a relatively nonspecific competition for anionic sites on the gill. Ca2+ was an exception and was more potent at reducing Zn uptake, likely because only Ca2+ would also compete for absorption. Although Na+ and Mg2+ were able to markedly reduce Zn uptake, they had no effect on Zn toxicity (measured with 96-h LC50 tests), a result paralleled by their inability to restore Ca2+ uptake that was inhibited by Zn. In contrast, Ca2+ reduced Zn toxicity and restored Ca2+ uptake. These results partially dissociate Zn uptake from Zn toxicity, implicate disturbed Ca2+ uptake as the toxic mechanism, and have profound implications for water quality criteria where Ca2+ and Mg2+ (the two 'hardness' cations) are traditionally considered to be equally protective.
|Number of pages||8|
|Journal||Canadian Journal of Fisheries and Aquatic Sciences|
|State||Published - Dec 1 1999|
ASJC Scopus subject areas
- Aquatic Science