Effects of Copper, Cadmium, and Zinc on the Hatching Success of Brine Shrimp (Artemia franciscana) |
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Authors: | K V Brix R M Gerdes W J Adams M Grosell |
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Institution: | (1) EcoTox, 6330 SW 34th St., Miami, Florida 33155, USA;(2) University of Miami, 4600 Rickenbacker Cswy, Miami, Florida 33149-1098, USA;(3) Rio Tinto, 5295 South 300 West, Suite 300, Murray, Utah 84107, USA |
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Abstract: | Previous studies indicate that the hatching success of brine shrimp (Artemia franciscana) cysts is surprisingly sensitive to ambient metal concentrations. These studies estimated median effective concentrations
(EC50s) of 7, 5, and 28 μg l−1 for Cd, Cu, and Zn, suggesting that the hatching end point for A. franciscana is the most sensitive tested to date for Cd and Zn in saline environments and comparable in sensitivity with the most sensitive
tested to date for Cu. Furthermore, these data suggest that brine shrimp are at significant risk from Cu and Zn in Great Salt
Lake (GSL), UT, where ambient concentrations as high as 10 and 14 μg l−1, respectively, have been measured. Given that brine shrimp appear to be successfully reproducing in GSL, we hypothesized
that these toxicity values were either biased low as a result of an artifact of the test method used or that site-specific
water-quality conditions in the lake had decreased metal bioavailability such that brine shrimp could successfully reproduce.
To test these hypotheses, we initiated a step-wise series of experiments. First we investigated the effects of pretreatment
of brine shrimp cysts with antibiotics on brine shrimp sensitivity to metals because previous investigators as part of their
test methods have used antibiotics. Next we considered the effect of ionic composition of the artificial test media on sensitivity.
Finally, we evaluated the effects of the site-specific water quality of the GSL on metal bioavailability and toxicity. Results
indicate that pretreatment of cysts with antibiotics had no effect on sensitivity. However, we were unable to repeat the previous
values for Cd and Zn, obtaining EC50s of 11,859 and 289 μg l−1 for Cd and Zn, respectively. For Cu, however, we estimated an EC50 of 12 μg l−1, so we conducted further testing on the artificial media, adjusting the media composition to better reflect the Ca2+ and HCO
3
−
concentration of normal seawater. This increased the EC50 to 28 μg l−1. Finally we evaluated the toxicity of Cu in GSL water and obtained an EC50 of 68 μg l−1, suggesting that the increased dissolved organic carbon in GSL has a significant protective effect. Overall, the results
of this study suggest that brine shrimp hatching success is not particularly sensitive to Cd and Zn, but it is sensitive to
Cu. However, site-specific water-quality conditions ensure that brine shrimp cyst hatching success is not significantly affected
by any of these metals at the normal background concentrations that occur in GSL (<15 μg l−1). |
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