Debolina Ghosh
Hathaway Brown High School, Shaker Heights, Ohio, USA
Introduction: Daphnia Magna (water flea) is a prototype of the freshwater aquatic life. This study noted the effect of pH on its heart rate and life.
Material and Methods: The Daphnia magna, kept at a pH of 7, were examined under a microscope to record the heart rate at 0, 2, 5, and 10 minutes. Similar procedures were repeated for the pH 6 (vinegar solution) and 8 (sodium bicarbonate solution). The effect on heart rate was compared by unpaired (different cohorts) and paired (same cohort) t-test. Number of daphnia dying in each group was also recorded.
Results: 70 Daphnia magna were studied, 10 excluded as heart rate recording was faulty. Finally, there were 20 in each group- pH 7, 6, and 8. Heart rate at pH 7 was unchanged with time; it progressively decreased when exposed to the acid (pH 6) or alkali (pH 8). 10 Daphnia died in acid, 5 in alkali, and none in neutral pH after 10 minutes. Heart rates dropped significantly at 5 minutes of acid and 10 minutes of alkali exposure when compared to the neutral PH group. Within the same cohort, heart rates dropped significantly after 2 minutes of acid (P< 0.01) and alkali (P<0.05) exposure.
Discussion/Conclusions: The heart rate of Daphnia magna decreased significantly on exposure to mild acidic (pH 6) or alkaline (pH 8) environment, often leading to death. This study proves the impact of environmental pollution, greenhouse gas emission and consequent alteration of acid base status of the fresh water on aquatic life.