by Jennifer Helwich, Leslie GenKuong, Natalia Papilaya, Emmy Yuswita and Cassandra Dillon
Many would expect Crystal Cove State Beach to be a safe beach to swim in, seeing that it is kept up by the state. Unfortunately, local contaminants have seeped into the water supply, causing our water to be polluted with some unsafe bacteria. Bacteria are not always dangerous to the publicís health. We ourselves produce Coliform bacteria, which aid in the digestion of food. They cause no harm to our body. One type of Coliform bacteria found in humanís intestines and in other warm blooded animals is Fecal Coliform. However, the presence of these bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of man or other animals. These organisms of bacteria may be separated from the total coliform group by their ability to grow at elevated temperatures and are associated only with the fecal matter of warm-blooded animals.Usually the water on the surface film of the water or in the sediments on the bottom contain greater abundance of Fecal Coliform.On September 14, 1999, we set out to prove that Coliform bacteria are present in Crystal Cove in meaningful amounts. This report lists in detail the results of our lab tests on water samples from Crystal Cove State Park.
When we arrived at Crystal Cove State Park, we decided to first take a sample from the nearest outflow. We took it directly from the waterfall. There, we also measured the temperature of the water with a thermometer. We measured the depth and width of two points on the outflow at 10 feet and 20 feet from the waterfall. We then timed the flow of the stream for 5 feet twice. After, we measured 40 and 80 feet to the left and right of the outflow, we took one liter water samples at each of the four positions and measured the temperature. Next, we took our samples to the lab to perform the tests.
First, we needed to perform what is called the presumptive test, which is used to determine if gas-producing lactose fermenters are present in each of the water samples. This test also determines the Most Probable Number (MPN) of coliforms present. The steps for this test were as follows: Set up 21 TSLB and 42 SSLB test tubes in a test tube rack and label each tube according to the amount of water that is to be dispensed into itó10 ml, 1.0 ml, and 0.1 ml. Shake each bottle of water to mix its ingredients. With a 10 ml pipette, add 10 ml of water to each of the TSLB test tubes. With the 1.0 ml pipette, add 1.0 ml of water to three of the SSLB test tubes. With a 1.0 ml pipette, add .1 ml of water to the last three SSLB test tubes. Incubate all of the tubes at 35 degrees for 48 hours. After 48 hours, examine each of the tubes individually looking for a small bubble in the tube of lactose broth and a color change to yellow. Determine the Most Probable Number by referring to the MPN table. Confirmed Test: Examine the petri plates filled with the bacteria and Endo Agar. Look for purple bacteria growth. This confirms that the bacteria found in the presumptive test is actually coliform bacteria.
We had a negative control, #0, which was pure bottled water. We found an MPN of 4. At location #1 (80 feet left from the outflow), we found that the Most Probable Number of bacteria present was 20. However, in the confirmed test, we came out with only a weak positive for coliform bacteria. At location #2 (40 feet left from the outflow) we found an MPN of 1100. The confirmed test also came back as a strong positive. Location #3 (outflow) came back with an MPN of 43 and a positive confirmed test. Location #4 (40 feet right from the outflow) had an MPN of 43 also and had a negative confirmed test. Finally, location #5 (80 feet right from the outflow) had an MPN of 4 and a negative confirmed test. Our test came back with a wide range of results for Most Probable Numbers, the highest being 1100, and the lowest being 4. We actually eliminated location #2 from our graph because the MPN was possibly a contamination. Table #1 explains how many out of three test tubes had a positive correlation with the presumptive test. All of these numbers lead us to find the most probable number of bacteria present.
The results from our lab experiment were actually both a bit expected and a bit surprising to us. First, we knew that there had to be some type of bacteria present in the water in the outflow because there was a state park sign next to the flow saying that it was contaminated. We predicted that there would be greater amounts of possible coliform bacteria the closer to the outflow the sample was from. This came out to be true with our tests; coliform bacteria was present in sample #3 (outflow) with the confirmed test. The unexpected result that we came up with was an MPN of 1100 in water sample #2. This was surprising because logically, the highest MPN should come directly from the outflow. The ocean does not produce coliform bacteria. This reading is a bit off the scale and could be because of a number of things that we couldnít pinpoint in the experiment. The most likely cause of this MPN is that the sample was contaminated; either from one of the other samples or from us touching the bacteria and adding it to the sample. It could also be the result of kelp or seaweeed that was infested bacteria that responds strongly to coliform. We would have been able to get a better idea of actual coliform present if we had done a few extra things.
If someone were to try this test, we would recommend taking at least two other sets of samples, and if possible, at times of different weather. Taking samples after rainfall would be ideal because there would be a lot more runoff from the city of Newport Beach, and the numbers would be more easily readable. Also, it would be ideal to take samples after both high and low tide. It would also have made things easier if we had all the dates planned out ahead of time when we would perform the actual experiments and given a bit of notice to the lab as to when we would be using it and needing the necessary materials.
Standard Methods for the Examination of Water and Wastewater, Twelfth edition. (New York: The American Public Health Association, Inc.) p. 608.
We would like to extend our sincere appreciation to Dr. Brad Dawson, Professor of Microbiology at Fullerton College. He provided us with the lab procedure and provided us with some helpful insight.
|Sample #||Presence in 10ml||Presence in 1ml||Presence in .1ml||MPN||Confirmed test|
|MPN=most probable number of coliform bacteria present|
|Table 1--Presence and MPN for water samples from Crystal Cove on September 14, 1999|