Comparison of Escherichia coli levels in Lake Michigan between 2004 and 2006 and of Escherichia coli levels between Bradford Beach and the South Shore Marina.

By Amanda Kaboskey, Katrina Patterson and Elisa Ratliff

Abstract

            We compared the levels of Escherichia coli in the waters of Lake Michigan near the Jones Island Water Treatment Plant in Milwaukee, WI.  We found that there was no statistical difference between the average numbers of E. coli colonies found in the waters of Lake Michigan near the Jones Island Waste Water treatment plant between 2004 and 2006.  We also compared the levels of E. coli in the waters of Lake Michigan near Bradford Beach and the South Shore Marina. We also found no statistical difference between the levels of E. coli in the waters from Bradford Beach and the South Shore Marina (p=0.322).

Introduction

The amount of Escherichia coli present in water is often used to identify the quality of water in a given area (Savageau 1983).   E. coli is present and has a positive role in the colons of humans and other mammals.  They help to further break down food into usable nutrients that the body.  E. coli plays a very important role in human digestion as long as it stays in the colon. However, the presence of E. coli in the water supplier is a problem especially if it gets into the drinking water system because it can cause severe gastric problems in individuals who ingest the bacteria (Fields 2005).

E. coli normally survive at 37 ◦C when they are in their primary environment in the colon.  However, they can survive in temperatures below freezing from 10 ◦C- 14◦C although they normally will exhibit negative growth rates at lower temperatures (Savageau 1983).  The E. coli normally live under anaerobic conditions in the colon but when they are in the water they generally live in an aerobic environment and this also contributes to their negative growth rate in water (Savageau 1983).  Due to this fact, water samples were taken a few centimeters below the water surface instead of right at the surface in hopes of capturing a more anaerobic environment. 

A study was done in 2004 by our peers from Alverno College and we sought to test the water from Lake Michigan in the same areas they did and compare our results to see if the coliform bacteria has increased or decreased (Doughty and Clark 2004).   We hypothesized that the average number of E. coli colonies would be lower in 2006 than they were in 2004.

The study done in 2004 only tested water south of the MMSD Jones Island Waste Water treatment plant (Doughty and Clark 2004).  We wanted to expand the sampling and test water from Lake Michigan north of water treatment plant as well.  We decided to take samples from the Bradford Beach area.  This is a popular beach in the summer in which many people swim in so we thought it would be very interesting to see what the water quality would be like in this area. This specific beach often emits a noticeably pungent smell, so it led us to believe that there may be some bacterial colonies living in the water.  We hypothesized that the average number of E. coli colonies would be greater north of the treatment plant at Bradford Beach than it would be south of the plant at the South Shore Marina.

Materials

  • Large screw-top test tubes (12)
  • Gloves
  • Wader boots
  • Keson 50 meter graduated metric tape measure(model OTR50M)
  • Label Tape
  • Marker
  • Fume hood
  • 3M Petrifilm E.coli/Coliform Count Plates (30)
  • Sterile pipettes (30)
  • Incubator (37 C)
  • Scientific Institutes Darkfield Quebec Colony Counter

 

                                                                 Methods

            On October 25, 2006, a total of 12 water samples from Lake Michigan were collected in sterile screw-top test tubes. There were two locations chosen for water sampling the South Shore Marina (2900 S. Shore Drive, Milwaukee,WI) and Bradford Beach (2400 N. Lincoln Memorial Drive, Milwaukee, WI). The South Shore Marina which is located 3,369 meters south of the Milwaukee Metropolitan Sewerage District’s Jones Island Water Treatment Plant (700 E. Jones Street, Milwaukee, WI). Bradford Beach is located 11,877 meters north of the MMSD Jones Island Water Treatment Plant. We were unable to collect samples from the Jones Island Water Treatment Plant because all areas near the facility were enclosed by fences with restricted access or the open areas didn’t allow easy access to the water. A total of seven water samples were collected from the South Shore Marina location and five water samples from the Bradford Beach location. At both locations the samples were collected 150 meters apart (Table 1).

            Each water sample was first shaken, and then inoculated in one ml amounts to a 3M Petrifilm E.Coli/Coliform Count Plate #2006-01KC according to the instructional manual included with the plates. This was done under a fume hood using one ml sterile pipettes. Each water sample was used to inoculate two plates, which were labeled with the sample number and A or B. The plates were then incubated at 37 C and the water samples placed in the microbiology refrigerator.

            On October 27, 2006 the plated water samples were then analyzed to determine the number of bacterial colonies that had grown and were then classified according to the color of their growth (Table 2). This was done using a Darkfield Quebec Colony Counter from Scientific Institutes. The plates were then returned back into the 37 C incubator. Microsoft Excel for Windows, version 5.1 was used to perform a T-test and to generate our graphs for the Lake Michigan water samples. The plates that experienced no growth 3A, 4B, 5A, 5B, 6A, and 7A were reinnoculated onto new Petrifilm plates. This was done using the same procedure as the previous plates. The plated water samples were then analyzed on October 30, 2006 in the same manner as the previous plates.

 

                                                                                                             

Table 1: The Locations and Interval Distances of the Lake Michigan Water Samples.

Location

Sample (#)

Distance (Meters)

Distance From the Jones Island Water Treatment Plant (m)

South Shore Marina

1

0

3,369

(South of MMDS)

2

150

3,519

 

3

300

3,669

 

4

450

3,818

 

5

600

3,969

 

6

750

4,119

 

7

900

4,269

Bradford Beach

8

0

11,877

(North of MMDS)

9

150

12,027

 

10

300

12,177

 

11

450

12,327

 

12

600

12,477

 

 

Results

            There was no statistical difference between the average numbers of E. coli colonies found in the waters of Lake Michigan near the Jones Island Waste Water treatment plant between 2004 and 2006 (Figure 1, P=0.442). There was no statistical difference between the levels of E. coli in the waters of Lake Michigan at Bradford Beach and South Shore Marina (Figure 2, P=0.322).

 

 

 

 

 

 

 

 

Table 2: The Amounts of Bacterial Colonies Counted from the Lake Michigan Water Samples

 

Plate

# of bacterial colonies

 

Coliform Colonies

 

Non-Coliform Colonies

 

E.coli colonies

 

1A

8

1

4

3

1B

10

2

3

5

2A

2

-

2

1

2B

4

2

1

-

3A

-

-

-

-

3B

2

-

2

-

3C

31

31

-

-

4A

1

-

1

-

4B

-

-

-

-

4C

1

1

-

-

5A

-

-

-

-

5B

-

-

-

-

5C

3

3

-

-

6A

-

-

-

-

6B

1

-

1

-

6C

3

3

-

-

7A

-

-

-

-

7B

-

-

-

-

7C

1

1

-

-

8A

5

-

5

-

8B

3

-

3

-

9A

6

1

5

-

9B

4

-

4

-

10A

28

4

24

-

10B

11

1

10

-

11A

22

5

16

1

11B

16

3

11

2

12A

21

1

20

-

12B

23

1

22

-

 

 

Figure 1. Comparison of average number of E. coli colonies between 2004 and 2006.

 

 

           

Figure 2. Comparison of average number of E. coli colonies at Bradford Beach and South Shore Marina

 

Discussion

            The levels of Escherichia coli found in the waters of Lake Michigan near the Jones Island Water Treatment Plant in Milwaukee, WI had no statistical difference in 2006 than the levels found from 2004.  Several factors could have affected our results.  First of all, by the time our water samples were collected the first hard frost had already come and this could have killed off many of the E. coli in the water (Savageau 1983). If the experiment were to be conducted again we would be sure to take water samples earlier in the fall before the temperatures became too low. 

            We noticed a correlation between the presence of birds in an area and the presence of E. coli.  E. coli colonies were found in the areas were ducks and seagulls were congregating.  It is possible that the bird feces is the source of the E. coli instead of sewage from the water treatment plant. E. coli is found in the intestinal tracts of animals, so these bacteria could be found in the feces of the birds (Holton 2002).

            There was also no statistical difference between the average numbers of colonies E. coli found in the waters of Bradford Beach versus the South Shore Marina.  This could be due to the fact that in general there were only a few colonies found in only a few samples so it was hard to get data that is statistically significant.  In the future we could greatly increase our sample size in an effort to get data that is statistically significant. 

           

 

 

 

 

 

 

 

References

Doughty, L. and Clark, B. 2004. The Effect of Untreated Sewage on Escherichia coli Population Levels in Lake Michigan. Alverno College. Retrieved on October 4, 2006 from http://courses.alverno.edu/educator/student/viewsite.cgi?burtonrs*anderser*mpos=4&spos=0&slt=z55h8Xren7jU.*bi341012006fa*0001*3

Fields, Scott. 2005. Great Lakes: Resource at risk. Environmental Health Perspecitves, 113: 164-173. Retrieved on October 4, 2006 from JSTOR.

Holton, C.W. 2002 E.coli exposed! Environmental Health Perspectives, 110:586-589. Retrieved on November 22, 2006 from JSTOR database.

Savageau, M.A. 1983. Escherichia coli habitats, cell types and molecular mechanisms of gene control. The American Naturalist, 122: 732-744. Retrieved on October 4, 2006 from JSTOR.