Beth Martinez

BI 341: Ecology

10-21-2007

 

Field Research Project:

 

Comparison of the dissolved O2 level in local ponds and rivers

 

Abstract:

 

            Oxygen is an important component of water for aquatic species survival (Foss et al, 2007).  Dissolved O2 levels (DO) differ in various bodies of water.  There are several ways in which water receives O2 including aeration (EPA, 2007).  I wanted to see whether the DO was higher in rivers than in ponds because rivers are constantly in motion.  I used an oxygen meter to take readings from several different local ponds and rivers.  I found that there was a significant difference in the DO between the rivers and ponds (p = 0.041).  The average O2 level for rivers was higher, 30.9 mg/L versus 17.1 mg/L for the ponds.

 

Key Words:  Dissolved oxygen levels (DO), aeration, water quality      

 

Introduction:

 

            Water is a source of life that most living organisms on the planet cannot do without.  Studies have found that aquatic species are healthier and are able to survive harsher conditions such as high ammonia concentrations when the water oxygen levels are most favorable (Foss et al, 2007).  Due to the presence of man and industry, water pollution continues to be a problem throughout the world.  One of the determining factors for the cleanliness of water is its dissolved oxygen level (Sanchez et al, 2007). 

There are several ways in which water can receive O2, one of which is directly from the air through aeration, or when the water is stirred (EPA, 2007).  Rivers are always moving and ponds are mostly stagnant unless there is a breeze present.  For this reason, I hypothesized that the dissolved O2 level in rivers would be greater than the dissolved O2 levels in ponds.

Researchers do not have an exact number for the ideal dissolved O2 level in water; although they do know that aquatic animals do better and show less signs of stress when the O2 level is above 6 mg/L.  When the O2 level of the water and air are in equilibrium, the range is in between 8 and 14 mg/L depending on the temperature outside (EPA, 2007). 

Much time and effort goes into monitoring the dissolved oxygen levels in our region, specifically in the rivers and the Great Lakes.  This is a way that the Environmental Protection Agency can determine if their water management programs are in fact making a difference in the water quality (EPA, 2007).

 

Methods:

            All O2 level readings were taken using an YSI 85 Oxygen, Conductivity, Salinity, & Temperature Meter, Model 85/25 Ft., SN: 97H1423.  All readings were taken at local ponds and rivers, and there were more ponds than rivers available for sampling in the area.  Every reading was taken at a water depth of 20cm, which was basically the deepest depth allowed for directly off of most shores.  For the ponds, the O2 meter probe was moved from side to side at a rate of about 30 cm per second until the reading stabilized.  This did not need to be done for the rivers, where the water was constantly moving. 

            All readings were taken over the course of two different days.  The days differed in temperature by just less than 1 o C (Fig. 2).  I chose the entry points to take my readings based on convenience and safety.  If there was a several meter stretch that was equally accessible, I marked off each meter using a Keson 50 Meter Graduated Metric Model- OTR 50 M.  Starting at the furthest left access point when facing the water, I marked off each meter going for no more than 10 meters.  I then used a random number table retrieved from Stat Trek.com to choose which meter point to take the reading. 

The entry points to all readings taken at ponds were near the recreational buildings or pavilions that were located a few meters from the water’s edge.  Each of these buildings had either cement or wooden slabs that went directly to the water’s edge.

River

Description of entry point

 

Milwaukee

Reading was taken off the pier located behind the Milwaukee Ale House Restaurant.  Facing the water, I measured off the ten meters starting from the farthest left point of the pier.  Meter 5 was randomly selected as entry point.

 

Kinnickinnic

Reading was taken beneath the bridge of the Kinnickinnic River Parkway which is located inside of Jackson Park.  I measured off the ten meters starting from flush up to the right side of the bridge, when facing south.  Meter 2 was randomly selected as entry point.

 

Menomonee

Reading was taken directly across the street from Jacobus Park Pond.  There is only one slender, steep path that leads up to the rivers edge.  Reading was taken from edge.

 

Root

Root River reading was taken from the top of the bridge that goes over the river, facing east on Root River Parkway.  I measured off the ten meters starting from the farthest left point of the bridge facing east.  Meter 2 was selected as the entry point.

 

Body of Water

Address

Jackson Park Pond and Kinnickinnic River

KK River Parkway and S. 43rd St.               

Mitchell Park Pond

W. Pierce St and S. 25th St

Kosciusko Park Pond

S. 8th and W. Lincoln Ave.

Humboldt Park Pond

S. Lenox Ave and E. Montana St

Holler Park Pond

S. 6th St and W. Edgerton Ave

Wilson Park Pond

W. Howard Ave and S. 20th St

Greenfield Park Pond

W. Lincoln Ave and S. 116th St

Jacobus Park Pond and Menomonee River

N. 66th St and Menomonee River Parkway

Milwaukee River

E. Buffalo St and S. Water St

Root River

Root River Parkway and W. Lincoln Ave.

 

Figure 1. Location of entry points where dissolved O2 level readings were taken.

 

 

 

 

 

 

 

 

 

 

Results:

 

Location

Time

O2 level reading

H2O temp.

Date

Outdoor temp.

Jackson Park Pond

1:30 pm

8.8 mg/L

14.3 o C

10-13-07

14.6 o C 

Mitchell Park Pond

1:51 pm

9.1 mg/L

15.6 o C

10-13-07

14.6 o C 

Kosciusko Park Pond

2:19 pm

9.9 mg/L

15.0 o C

10-13-07

14.6 o C 

Humboldt Park Pond

3:10 pm

10.2 mg/L

14.2 o C

10-13-07

14.6 o C 

Holler Park Pond

3:37 pm

9.9 mg/L

14.4 o C

10-13-07

14.6 o C 

Wilson Park Pond

4:18 pm

24.2 mg/L

14.2 o C

10-13-07

14.6 o C 

Greenfield Park Pond

5:27 pm

24.8 mg/L

14.9 o C

10-15-07

15.4 o C

Jacobus Park Pond

6:01 pm

39.9 mg/L

14.1 o C

10-15-07

15.4 o C

Kinnickinnic  River

5:00 pm

24.3 mg/L

15.3 o C

10-15-07

15.4 o C

Root River

5:31 pm

24.6 mg/L

12.7 o C

10-15-07

15.4 o C

Menomonee River

6:28 pm

41.2 mg/L

14.1 o C

10-15-07

15.4 o C

Milwaukee River

5:35 pm

33.5 mg/L

18.0 o C

10-15-07

15.4 o C

 

Figure 2.  Data collected at local ponds and rivers including dissolved O2 level and water temperature.

           

           

 

 

 

 

            There was a significant difference between the dissolved O2 levels in the ponds versus the rivers (Fig. 3, p = 0.041).  The average O2 level in the rivers was higher, 30.9 mg/L with a standard deviation of 8.085 mg/L, compared to the ponds which had an average of 17.1 mg/L with a standard deviation of 11.425 mg/L.

 

Figure 3.  Dissolved O2 levels in rivers vs. ponds.

 

 

Discussion:

 

            In conducting this project, my hypothesis was supported by the data that was gathered (p = 0.041).  The average dissolved O2 level in rivers was in fact higher that the average in the ponds.  This makes sense because ponds are often stagnant, where rivers are continually in motion.  Oxygen levels are dependant on many other factors than just aeration. 

Algae require O2 to survive and remove it from the water, lowering the dissolved O2 level.  High phosphorus levels lead to higher levels of algae which increase the problem (EPA, 2007).  Photosynthetic activity of algae and other organisms causes the dissolved O2 levels to fluctuate depending on the time of day and season.  Dissolved O2 levels are the lowest during the day, and the spring is the highest photosynthetic time of year (Neal et al, 1998).     

In order for environmental workers to know how clean surface waters are, dissolved O2 levels are usually taken (Sanchez et al, 2007).  When dissolved O2 levels are too low, aquatic animals do poorly or die (Foss et al, 2007).  When the highest possible oxygen saturation level for a water source is known, and the actual dissolved O2 level is lower than this, the mg/L in between these two values is known as the dissolved oxygen deficit (D).  The dissolved oxygen deficit has a direct relationship with the water quality index (WQI), which is a common instrument with criteria used to determine water quality.  This index is used to take large quantities of information about a body of water, and to compute the data into a single number in between 1-100, 100 being the highest level of water quality (Sanchez et al, 2007). 

Researchers have found that there is a relationship between D and WQI, supporting the idea that the dissolved oxygen levels can be used as an indicator of water quality.  As D increases, WQI decreases.  This is helpful because D can be measured in a shorter amount of time than it would take to use the WQI to analyze water samples (Sanchez et al, 2007).

In doing this project, I realized that it takes a lot of time to get readings from different bodies of water.  If I were to do this experiment again, I would plan on traveling further in order to have more rivers in the data.  I also would have liked to have taken my samples within the same hour of the day.  However, this would take several days more to accomplish.

 

References

 

Environmental Protection Agency GLNPO. (2007). Great Lakes Monitoring- Dissolved Oxygen Depletion in Lake Erie. Retrieved on October 2, 2007 from: http://www.epa.gov/glnpo/glindicators/water/oxygenb.html

 

Foss, A.; Imsland, B. R.; Schram, E.; Stefansson, S. O. (2007). Interactive effects of oxygen saturation and ammonia on growth and blood physiology in juvenile turbot. Aquaculture, 271: 244-251. Retrieved on October 16, 2007 using Science Direct database.

 

Neal, C.; Harrow, M.; Williams, R. J. (1998).  Dissolved carbon dioxide and oxygen in the River Thames. Science of the Total Environment, 24: 205-217. Retrieved on October 16, 2007 using Science Direct database.

 

Sanchez, E.; Colmenarejo, M. F.; Vicente, J.; Rubio, A.; Garcia, M. G.; Travieso, L.; Boria, R. (2007). Use of the water quality index and dissolved oxygen deficit as simple indicators of watersheds pollution. Ecological Indicators, 7: 315-328. Retrieved on October 16, 2007 using Science Direct database.