Measurement of Dissolved Oxygen in Lakes and Ponds during Light and Dark Conditions

Juliane Finn; Rosie Berger

November 2007

 

Abstract: Dissolved Oxygen was recorded in the absence and presence of light to test if levels were different. Algae goes through photosynthesis when light is available and respiration when it is lacking, which led us to the hypothesis that dissolved oxygen would be higher during the day. All data was taken in the same 24 hours, and results showed that dissolved oxygen levels were higher during the day than at night.  A two tailed t-test resulted in a p-value of 2.6 x 10-11.

 

Introduction: Lakes include vegetation and different forms of algal growth, which go through photosynthesis and respiration to obtain and transform energy. Photosynthesis requires sunlight and water, and is performed during the day, while respiration is done with the absence of light. Peak photosynthesis rates are obtained in the late morning when sunlight intensity is near optimal (Urchin et. al, 2005). Basically, during photosynthesis plants take in carbon dioxide and water, and release oxygen, conversely during respiration they take in oxygen and release carbon dioxide and water. From this, we hypothesized that oxygen levels would be higher during the day when algae is photosynthesizing. Dissolved oxygen (DO) consumption and regeneration by aquatic macrophytes is directly related to their rates of photosynthesis and respiration (Urchin et. al, 2005). In addition, the variation of dissolved oxygen in aquatic systems is impacted by the algae (Kish et al 2006)

 

Methods and Materials: Ten different lakes and ponds were chosen in the area of Milwaukee to test dissolved oxygen. Each location is listed by the address instead of the latitude and longitude (table 1 and 2). Locations consisted of Upper Kelly Lake, Whitnall Park Pond, Scout Lake Park, Bay View Park (Lake Michigan), Humboldt Park, Root River Parkway Pond, McCarty Park, Jackson Park Pond, Wilson Park Pond, and Greenfield Park. Ten samples were taken during daylight with clear skies, and ten night samples were taken after sundown. Samples were collected with plastic Ziploc bags separated by day and night and each labeled appropriately. Night samples were placed in a cooler directly after taken and the day samples in a clear plastic box. Dissolved Oxygen was measured on site with a YSI 85 Model. All samples were collected in the same day, but absorbency, transmittance, and pH were recorded within 48 hours (table 1 and 2). Temperature, salinity, and dissolved oxygen were recorded using this instrument. The pH was tested using pH test strips and comparing the color to the given table. Absorbency and Transmittance were recorded after running each sample through the Fisher Scientific Spectro Master model 410 wavelength 560.

 

Results: After all data was collected and processed, results supported the initial hypothesis. Dissolved oxygen was significantly higher during the day with a p-value of 2.6 x 10-11 (figure 1.1). Averages for dissolved oxygen came to 19.429 mg/L during the day and 5.385 mg/L at night (figure 1.1).

 

 

 

 

Table 1.  Day and Night Comparison (DO, Absorbency, and Transmittance)

 

Site #

Park

Location

 DO day

(mg/L)

DO Night

(mg/L)

Absorben-cy Day (ABS)

Absorben-cy Night (ABS)

Transmit-tance Day (%)

Transmit-

tance Night (%)

1

Whitnall

5879 S. 92nd Street

19.10

5.23

.08

.0005

83

99.5

2

Greenfield

2028 S. 124th

19.30

4.48

.025

.0095

99

98

3

Humboldt

3000 S. Howell Ave

19.25

4.99

0.0

0.0

100

100

4

Wilson

1601 W. Howard

19.60

6.46

.095

.03

81

94

5

Jackson

3500 W. Forest Home Ave

21.70

5.76

.225

.15

60

70

6

Bay View Park (Lake Michigan)

Estes Street and Superior Ave.

19.47

4.20

0

0

100

100

7

McCarty

8214 W. Cleveland Ave.

18.70

1.87

.087

.001

80

99

8

Scout Lake

6201 W. Loomis Rd.

19.46

6.59

.08

 

83

 

9

Root River Parkway Pond

Root River Parkway and College Ave.

19.31

9.40

.06

 

87

 

10

Hales Corners

5765 S. New Berlin Rd.

18.4

4.87

0.0

0.0

100

100

 

 

 

Table 2.  Day and Night Comparisons (pH, Temperature, and Salinity)

 

Site #

Park

Location

pH day

pH night

Temperature day (C)

Temperature night (C)

Salinity day

Salinity night

1

Whitnall

5879 S. 92nd Street

6.5

6.5

12.8

8.4

0.0

0.0

2

Greenfield

2028 S. 124th

7.0

7.0

11.5

10.7

0.1

0.0

3

Humboldt

3000 S. Howell Ave

7.0

7.0

12.5

10.5

0.1

0.1

4

Wilson

1601 W. Howard

6.0

6.0

13.9

10.4

0.6

0.3

5

Jackson

3500 W. Forest Home Ave

6.5

6.5

11.9

10.4

0.3

0.0

6

Bay View Park (Lake Michigan)

Estes Street and Superior Ave.

7.0

7.0

12.6

9.4

0.0

0.0

7

McCarty

8214 W. Cleveland Ave.

6.5

6.5

12.7

11.6

0.1

0.2

8

Scout Lake

6201 W. Loomis Rd.

6.0

6.0

11.8

10.3

0.0

0.0

9

Root River Parkway Pond

Root River Parkway and College Ave.

7.0

7.0

12.0

11.3

1.2

1.2

10

Hales Corners

5765 S. New Berlin Rd.

7.0

6.5

12.8

11.8

0.1

0.3

 

 

Figure 1.1 Dissolved Oxygen with and without the presence of light

 

Discussion and Conclusion:  The results found in this experiment supported our hypothesis.  The levels of dissolved oxygen were higher during the daytime hours than the nighttime hours.  This can be explained by the processes of respiration and photosynthesis.  The lakes and ponds studied all had some level of algal growth in them.  This algae releases oxygen during the day when photosynthesis is taking place and draws in oxygen at night during respiration, therefore oxygen levels will be higher when the sun is out and the algae is photosynthesizing. As stated earlier, photosynthesis and respiration can have large affects on the levels of dissolved oxygen within a body of water.  Higher levels of algal growth could lead to increased photosynthesis and respiration, conversely lower levels of growth could lead to decreased photosynthesis and respiration. Surrounding habitat that lines the perimeter of the ponds or lakes could contribute to the algal growth in this experiment. Heavier brush and vegetation could prohibit run off of organic matter into the water, which would lead to less algal growth in the absence of organic matter.  On the other hand, little or no brush surrounding the body of water could lead to increased runoff of organic matter and an increase of algal growth and dissolved oxygen. Heavy population of geese, ducks and other animals could also increase growth of algae due to the droppings which are high in nutrients. Algal growth is controlled by many factors, nutrients being the main component (Kish et al 2006).  Those parks that had concrete public access may experience increased run off because there is no brush or thick vegetation to take in the nutrients. Nitrogen, phosphorus, or light can help to limit algal growth, but increased levels of this can often result in unwanted blooms (Busse et al. 2006). In turn, this leads to poorer water quality and increased algal growth. Sites that had a constant flow of water were also noticed to have minimal amounts of algae. When the water is stagnant, nutrients are utilized quickly by the algae and not transported down stream by currents. Besides fecal matter from animals and amount of brush, human development also contributes to the ecology of the water. Urban land use has a large influence on the chemistry and biology of streams as well as increased nutrient levels, increased light, and altered hydrology (Busse et al. 2006). As urban development increases brush, trees and other natural vegetation gets depleted which alters the ecology.

            There are a few things that could be changed if this experiment were to be redone.  First, when collecting the water samples it is highly recommended that sterile glass bottles be used in the place of plastic bags, this will lead to less of a mess and less water lost in transport.  Second, it could be beneficial to test water levels at different depths rather than just under the surface.  This could lend an idea to how dissolved oxygen levels differ in different areas of the body of water.  Lastly, nutrients could be measured to determine what aids and what hinders algal growth which could in turn influence the dissolved oxygen levels. 


 

Literature Cited

Urchin, C.G., Hunter, J.G., Park, S.S., and Vadas, T.M. (2005) In situ Measurement of Macrophyte Photosynthesis and Respiration in Shallow Lakes. Journal of Environmental Engineering 131:2 Retrieved November 10, 2007 from EBSCO host

Kish, S.M., Bartlett, J., Warwick, J.J., McKay, A., and Fritsen, C. (2006) Long-Term Dynamic Modeling Approach to Quantifying Attached Algal Growth and Associated Impacts on Dissolved Oxygen in the Lower Truckee River, Nevada. Journal of Environmental Engineering 132: 10. 1366-1375. Retrieved November 21, 2007 from EBSCO host

Busse, L.B., Simpson, J.C., Cooper, S.D. (2006) Relationships among nutrients, algae, and land use in urbanized southern California streams. Canadian Journal of Fish and Aquatic Science. 63: 2621-2638 Retrieved November 21, 2007 from EBSCO host.