The objective of this research was to determine the effects of acidification, a change in water pH, on the grass shrimp Palaemonetes pugio. The null hypothesis is that when water temperature, salinity and pH change, the heart rate of the grass shrimp in beats per minute will not change. The dependent variable was heart rate as a measure of metabolic oxygen consumption. The independent variables were salinity, water temperature, pH and the length of each P. pugio.
The size in length of each P. pugio was inversely correlated with heart rate and beats per millimeter of length. The average heart rate of P. pugio at a pH of 6.5 was significantly lower than at a pH of 7.5. The heart rate of P. pugio did not vary significantly at salinities of 10, 15, 20 and 25 parts per thousand. The average heart rate of the prawn at 10°C was significantly lower than that at a water temperature of 25°C.
The null hypothesis that the heart rate of P. pugio would not vary with a change in pH was rejected; the average heart rate at 6.5 was significantly lower than at 7.5. The null hypothesis that heart rate would not vary with a change in salinity was accepted; the average heart rate did not vary significantly with changes in salinity. The null hypothesis that heart rate would not vary with a change in water temperature was rejected.
This is the first study to show that as the length of the prawn increases, its heart rate declines, regardless of variations in pH, water temperature and salinity. Based on the inverse relationship between the length of P. pugio and both heart rate and beats/mm, it is recommended that scientists in future studies measure the organism’s length to calculate the beats/mm of P. pugio and other species of Palaemonetes.
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George, American Museum of Natural History – Young Naturalist Awards, August 2011. Full article.
