Daphnia Experiment Reaction Paper

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For this experiment, I used Daphnia magna and Daphnia pulex that was cultured from stocks from Aquatic Bio Systems Inc. (Fort Collins, CO). Each species was cultured individually in 900 mL glass jars filled with moderately hard water. I created moderately hard water using the recipe as follows: 0.473 g CaSO4 , 0.959 g NaHCO3 , 1.223 g MgSO4 • 7H2O , and 0.039 g KCl per 10 L of deionized water. All references to water for the remainder of the paper refers to moderately hard water unless otherwise stated. These daphnid cultures were fed 2 mL of algae (Selenastrum capricornutum) containing 3.0 x 107 cells per mL on Monday, Wednesday, and Friday. The water was changed every Friday. Once a month, 1 mL of a yeast and trout chow
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I examined the effects of buffered and unbuffered gibberellic acid on Daphnia magna and Daphnia pulex. I used six different concentrations: 0 mg/L (control), 1 mg/L, 5 mg/L, 25 mg/L, 125 mg/L, and 625 mg/L. Gibberellic acid (99% purity, Chemservice, West Chester, PA) was dissolved in deionized water as it ionized into gibberellin and H+ ions. Buffered and unbuffered gibberellic acid 5000 mg/L stock solutions were used for spiking exposure jars. The buffered stock solutions were buffered with sodium bicarbonate until the solution reached a neutral pH. Glass jars were filled with moderately hard water and spiked with the appropriate amount of the gibberellic acid 5000 mg/L stock solution to total 100 mL. As an example, the 625 mg/L concentration had 12.5 mL of gibberellic acid 5000 mg/L stock solution and 87.5 mL of moderately hard water. The jars were allowed to equilibrate after being spiked. Control jars were set up similar to the 625 mg/L concentration except deionized water was used instead of the gibberellic acid 5000 mg/L stock …show more content…
magna; however, due to high control mortality, the experiment only lasted six days. Three different concentrations of buffered gibberellic acid were used: 0 mg/L, 1 mg/L, and 100 mg/L. The lowest concentration, 1 mg/L, was chosen because the acute study showed sublethal effects could be seen between 1 and 100 mg/L. The highest concentration, 100 mg/L, was chosen because the negative effects of gibberellic acid were anticipated at this concentration. The glass jars were filled in the same manner as the jars in the acute experiment. As an example, a 100 mg/L replicate would contain 2 mL of the buffered gibberellic acid 5000 mg/L stock solution and 98 mL of moderately hard water. In a similar manner as the acute experiment, the pH and the conductivity were recorded before the daphnids were placed in the jars. The daphnids were placed in the jars, after the jars were spiked, and allowed to equilibrate. There were four replicates for every concentration with every replicate having three

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