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PW03 Plant Toxicology and Soil Interactions
(PW070) Effects of Iron amd Micronutrient Metals on Algal Growth in the Presence of Chelators.
Hirsch, M1, Emmons, V1, Roser, K1, O'Donoghue, J1, English, J1, Rennie, I2, 1 Eastman Kodak Company, Rochester, NY, USA2 Kodak Limited, Harrow, United Kingdom
ABSTRACT- The chelator, 1,3-propylenediaminetetraacetic acid (1,3-PDTA) and the chelation complex, ammonium ferric propylenediaminetetraacetic acid (AF-PDTA) have shown significant apparent toxicity to the alga, P. subcapitata in standard growth inhibition tests. Fish and daphnid tests with the same materials show little or no acute toxicity. It is hypothesized that the inhibition of algal growth by these materials is due to sequestration of essential nutrient metals from the growth medium by creation of chelation complexes or by co-precipitation with iron complexes formed by photolysis of ferric chelates. Studies with algae exposed to AF-PDTA in medium in which micronutrients were increased 3X showed increased growth compared to controls. When standard iron supplementation was omitted from the medium and the concentrations of micronutrients were increased 3X, the growth of algae exposed to AF-PDTA was restored to control levels. Substitution of ferric citrate (a more stable for of iron) for ferric chloride in the growth medium largely prevented the effect of AF-PDTA on growth. When the concentrations of Zn, Cu, and Co were increased in standard media containing 1,3-PDTA, the growth of algae was completely restored to control levels. These results demonstrate that chelators and chelation complexes can produce similar algal growth inhibition that is related to micronutrient sequestration, although the mechanisms of sequestration differ. The results support and supplement existing data for other chelators which have shown that the algal growth inhibition test over-predicts the impact chelators have under environmentally relevant conditions.
Key words: Chelators, Micronutrient metals, Pseudokirchneriella subcapitata, Algal growth
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