By: Drew Zagala

Test the nitrate, phosphorus, and pH of the Iris Pond and Green Heron Pond. Compare results to previous water quality tests to understand changes in nutrient levels and pH of the Arboretum’s bodies of water.

Additionally, test the nitrate, phosphorus, and pH of Tamarack Lake to determine its water quality and create a baseline for future monitoring.

High nutrient levels in a water system can severely change its ecosystem Increases algae concentrations and algal blooms Decrease levels of dissolved oxygen Reduces biodiversity Reduces aesthetic appeal

Credit: Sevenhillslake.com

Additionally, Green Heron supplies irrigation for the Arboretum grounds High levels of nutrients can encourage weeds

Nitrogen Applied usually as Nitrate (NO3

-), Urea(CH4N2O), and Ammonia (NH3) Highly water soluble chemicals

Prone to erosion by rain events, over-watering, and groundwater runoff

Source: United States Geologic Survey. Copyright 2003

Phosphorus Applied as Phosphorus penta-oxide (P2O5)

▪ Not water soluble, but binds to soil particles

Prone to erosion as soil erodes from an area – rain events, over-watering, high slope gradients

Source: The Caribbean Environment Program. Copyright 2014

pH tends to determine the type of plants/animals that can live in a body of water Nutrient availability for plants Solubility of heavy metals or other toxins

Source: Fundamentals of Environmental Measurements. Copyright 2016

Minnesota Pollution Control Agency Calculated average nutrient and pH levels for various ecosystems in

Minnesota.

North Central Hardwood Forests

Critical Eutrophic Level – 85 ppb phosphorus “Minnesota Lake Quality Assessment Report 3rd Edition”

Field pH Nitrate Total Phosphorus

8.6-8.8 10 ppb 23-50 ppb

25.8

20.4 20 20

0

5

10

15

20

25

30

2011 2012 2013 2016

Nit

rate

(ppb

)

Year

Arboretum Water Body Nitrate Levels (ppb)

Iris PondEcosystem Average

10 ppb

286

85

1736

52

0

50

100

150

200

250

300

350

2008 2011 2012 2013 2016

Pho

spho

rus

(ppb

)

Year

Arboretum Water Body Phosphorus Levels (ppb)

Iris Pond

Ecosystem Average

23-50 ppb

Critical Eutrophic Level85ppb

Shoreline buffer installed

7.7

8.1

7.6

8

5

5.5

6

6.5

7

7.5

8

8.5

2011 2012 2013 2016

pH

Year

Arboretum Water Body pH

Iris Pond

2016 Data was collected for Green Heron Pond..

Unable to sample from “cleaner” center of lake High levels of decomposing matter▪ Bog would normally filter out high levels of phosphorus from entering greater

lake area

Nitrate Phosphorus pH

Green Heron Pond <20 ppb 1440 ppb 7.04

128

20.5

0

20

40

60

80

100

120

140

2011 2012

Nit

rate

(ppb

)

Year

Arboretum Water Body Nitrate Levels (ppb)

Green Heron

Ecosystem Average10 ppb

41

2724

0

5

10

15

20

25

30

35

40

45

2008 2011 2012

Pho

spho

rus

(ppb

)

Year

Arboretum Water Body Phosphorus Levels (ppb)

Green Heron

Ecosystem Average

23-50 ppb

Critical Eutrophic Level85ppb

8

8.7

5

5.5

6

6.5

7

7.5

8

8.5

9

2011 2012

pH

Year

Arboretum Water Body pH

Green Heron

Horticulture Research Center

Lake Minnewashta

20

0

5

10

15

20

25

2016

Nit

rate

(ppb

)

Year

Arboretum Water Body Nitrate Levels (ppb)

Tamarack Lake

Ecosystem Average10 ppb

65

0

10

20

30

40

50

60

70

2016

Pho

spho

rus

(ppb

)

Year

Arboretum Water Body Phosphorus Levels (ppb)

Tamarack Lake

Ecosystem Average23-50 ppb

Critical Eutrophic Level85ppb

8.5

5

5.5

6

6.5

7

7.5

8

8.5

9

2016

pH

Year

Arboretum Water Body pH

Tamarack Lake

Iris Pond Healthy!

Green Heron Pond Relatively healthy!

Tamarack Lake Healthy!

Good levels of dissolved oxygenLow levels of algae and algal bloomsSupport diverse biota

Safe levels of dissolved oxygenModerate algae and algal bloomsSupport biota

Good levels of dissolved oxygenLow levels of algae and algal bloomsSupport diverse biota

Reduce the use of liquid fertilizers Do not over-apply!

Clean up grass clippings and pulled weeds

Remove animal droppings

And….

Designed to catch and store eroding nutrients and soil before they can pollute bodies of water.

What are desirable traits for the plants in a Shoreline Buffer? Deep root systems -Tolerate high levels of nutrients Tolerate high/variable levels of water High biodiversity, preferably perennial

Phosphorus erosion diagram: http://agrihelper.blogspot.com/2016/06/types-of-erosion-splashsheetrill-and.html Nitrogen erosion diagram: http://pubs.usgs.gov/fs/2003/fs091-03/ pH diagram: http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/ Minnesota Pollution Control Ecosystem Averages: https://www.pca.state.mn.us/quick-links/eda-guide-typical-minnesota-water-quality-

conditions Previous Water Quality data collected by past interns: Dan Miller. Water Quality Tests conducted by Tri-City/William Lloyd Analytical Laboratories Critical Eutrophic Levels from: Heiskary, Steven A., and C. Bruce Wilson. Minnesota lake water quality assessment report: Developing nutrient

criteria. Water Assessment & Environmental Information Section, Environmental Analysis & Outcomes Division, Minnesota Pollution Control Agency, 2005.

Eutrophic Lake Image: http://sevenhillslake.com/technical.html