Seasonal Changes in the Levels of Bacteria in Lake Wingra

Seasonal Changes in the Levels of Bacteria and E. Coli in Lake Wingra

By: Jessica Dennison, Stephanie Hendrickson, Emily Ciha

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Data Graphs and Results Discussion and Conclusion Implications and Recommendations

· Vilas Beach usage has declined in the past fifteen years from nearly a hundred thousand beach users in 1988 to about fifteen thousand beach users in 2001.

· The impact of sediment, excessive nutrients, road salts, and other pollutants carried from streets, buildings, lawns and parks to Lake Wingra, cause more bacteria to be present.

· Lake Wingra was closed due to these factors that contribute to high levels of bacteria and E. coli present.

Questions:

· How safe is the water at our local beach?

· How do these levels change throughout the seasons from late fall to spring?

Hypothesis:

· Levels of Bacteria and E.coli increases through winter months and reach an all time high during the spring.

· The impact of sediment, excessive nutrients, road salts, and other pollutants carried from streets, buildings, lawns and parks to Lake Wingra, cause more bacteria to be present.

Methods:

· We took samples in three different areas of Lake Wingra: the beach, the dock and the spring.

· There were a total of three different results that were taken in November, January and March.

· Each time we took three different samples for each areas using a 100ml sterilized plastic container. (For our first set of results we have an error factor and were only able to take two samples for the beach.)

· After each time we collected the samples, we mixed the water samples with a powder chemical that detects E. coli and coliforms, also knows as the Colilert System.

· We put water samples in quanta trays with 49 bit pouches and 48 smaller pouches and sealed the tray which dispersed the water samples among the pouches.

· We placed each sample in an incubator for 24 hours which allowed us to observe the E. coli levels for each sample. We took each sample that had yellow cells and placed them under an ultraviolet light which enabled us to read the E. coli levels.

Data Graphs and Results:

Figure 1:

Starting with our first results from November, the bacteria levels were high in the dock and in the spring areas compared to the beach. Considering all of these results were fairly close, we assume our results were more accurate than the samples taken in January. As you can see above, the level of bacteria in the beach, increased dramatically in January. This could be considered an error factor, because there was a large amount of sediment, which could also prove that sediment in the beach held or contained a lot of bacteria. In figure 2 the beach data was not used because of the sediment in the samples caused it to be an error. Another interesting fact to look at in our results was the bacteria levels actually decreased in the dock and the spring in January, compared to our results in November.

Figure 2

In figure two you see a line graph. The blue represents the tests that were taken in November. The pink line represents the tests taken in January. Notice there is no information for the beach in the January testing; this is because of sediment that got into the samples that caused an error in readings. The blue line from test number one seems to peak at the dock site, while in test number two, there is little if any E. coli found. Our hypothesis was true for the spring. In the first testing that was done, the E. coli in the spring was much higher the first time we tested.

Figure 3:

For our last set of tests we found that the levels of E. coli were significantly less then the previous tests we had done. Especially at the beach the results went from off the charts to barley detectable. This proved that our hypothesis was untrue. From the results of the tests, the E. coli seemed to have subsided as the seasons changed from fall to winter to now early spring. There was no line of error for the results in the spring season.

Discussion and Conclusion:

· Possible reasons for our results could be that the second samples were taken after a fresh rain and snow shower.

· We also encountered a factor of error in the beach samples from January when there was heavy sediment in our samples due to having to break open the ice to get the water sample.

· We concluded that our hypothesis was incorrect. Through the seasons the levels of bacteria and E. coli actually decreased overall opposed to increasing.

· Our hypothesis did not take into consideration that goose feces would contribute to the high levels of bacteria in the early winter.

· Our results and the information from our study can be useful in the early winter.

Implications and Recommendations:

· Further studies should be done on the levels of bacteria and E. coli in Lake Wingra.

· Drilling a hole in the lake when it is frozen rather than trying to the kick through the ice would be more appropriate and hopefully give more accurate results.

· For future studies, more frequent testing such as twice a month throughout the year, could help to determine the bacteria levels year round.

· People need to be informed and aware of the factors that affect the water quality so they can help in reducing the level of bacteria and E. coli in Lake Wingra.

· Studies such as ours will only help in opening the eyes of the public to bacteria levels and water safety.