Sample Abstract of a 5th grade student project
HOW DOES WATER POLLUTION AFFECT THE HEART RATE OF DAPHNIA (Water Flea)? John
Herr, and Judy Luedke (teacher) Valley Presbyterian School, 9200 N. Haskel
Ave. North Hills, CA 91343
Daphnia magna (waterflea) is a fresh water crustacean found in lakes and ponds
throughout much of North America and is an important element in the aquatic
food chain. Experiments were developed to determine how water pollution from
common household products affects the heart rate of Daphnia magna. Images
of the Daphnia heart were viewed on a computer connected to a compound videomicroscope
through an analog/digital converter. Daphnia were placed in single drops of
pond water on depression slides and videotaped twice to record normal resting
heart rates. Heart rates were determined by playing the digital videos in
slow motion and dividing the number of beats by the elapsed time reported
by the software. After an average resting heart rate was determined, one drop
of 1.0% pollutant was added to each slide, bringing the final pollutant concentration
to 0.5%, and the heartbeats were recorded at one, three, five and thirty minutes
from the time of exposure. The procedure was replicated with a second Daphnia
for all pollutants tested and the results were averaged. All of the pollutants
tested made the heart rates decrease during the thirty minutes observed. After
thirty minutes the heart rate went down 100% in ammonia and Draino“,
but only 51% in ethanol, and 21% in paint thinner. The greatest effect was
observed with ammonia which killed Daphnia in 3 minutes, followed by Draino“
which killed the Daphnia 5 minutes. Ethanol reduced the heart rate 51% after
thirty minutes while pant thinner reduced the heart rate only 21% during the
same period.
