Update on Phosphorus and
Cladophora in the Lake Michigan
Nearshore Zone
Harvey Bootsma
Nearshore TP and TDP Concentrations Since 1980,
Near Milwaukee Harbor
30
Total Dissolved P
Total P
[P] (μ g L -1)
25
19.4
20
15
14.5
12.5
12.6
11.9
11.7
10
9.5
7.8
8.2
6.9
5
0
1980-84
1985-89
1990-94
1995-99
2000-05
1
Spring Total P
(mean of all pelagic stations)
7
GLWQA Target for Lake Michigan: 7 μg/L
Total P (μ g/L)
6
Michigan
5
4
3
Huron
2
1
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
0
20-Year Phosphorus Trend at River Junction
0.3
mg/L
0.25
0.2
TP
0.15
0.1
0.05
SRP
0
1
/1
/8
2
1
/1
/8
3
1
/1
/8
4
1
2
/3
1
/8
4
1
/1
/8
6
1
/1
/8
7
1
/1
/8
8
1
2
/3
1
/8
8
1
/1
/9
0
1
/1
/9
1
1
/1
/9
2
1
2
/3
1
/9
2
1
/1
/9
4
1
/1
/9
5
1
/1
/9
6
1
2
/3
1
/9
6
1
/1
/9
8
1
/1
/9
9
1
/1
/0 0
1
2
/3
1
/0 0
1
/1
/0 2
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01
Data Source: MMSD
2
In Milwaukee River, dissolved P is becoming a
larger fraction of TP
Dissolved P : Total P Ratio
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1980
1985
1990
1995
2000
2005
Average [P] (ppm)
P in Wisconsin Cropland
60
50
40
30
20
10
0
Soil P Storage Change
(kg ha-1)
1968- 1974- 1978- 1982- 1986- 1991- 199573
77
81
85
90
94
99
5
4
3
2
1
0
1970
1975
1980
1985
1991
1994
1995
Bundy and Sturgul 2001
3
Milwaukee River Transect, April 2005
10
9
8
7
6
5
4
3
2
1
0
20
40
60
80
SRP (μg L-1)
infotrek.er.usgs.gov/.../ milwaukeemap.gif
250
200
1982-87
Mean = 102
150
100
50
0
J
J
F
F
M
M
A
A
M
M
J
J
J
A
J
A
S
S
O
O
N
N
D
D
Total P (μg L-1)
250
200
Milwaukee River TP
Concentrations have
increased in late spring.
1988-95
Mean = 72
150
100
50
0
J
J
F
F
M
M
A
A
M
M
J
J
J
J
A
A
S
S
O
O
N
N
D
D
250
1996-2001
Mean = 120
200
150
100
50
0
J
F
M
A
M
J
J
A
S
O
N
D
4
Milwaukee River Discharge
40
35
1982-87
Avg. = 18.4
30
25
20
15
10
5
Annual Means
0
J
F
M
A
M
J
J
A
S
O
N
D
25
35
20
m3 s-1
30
1988-95
Avg. = 13.1
25
20
15
10
15
5
10
5
0
0
J
F
M
A
M
J
J
A
S
O
N
D
1981
1986
1991
1996
2001
35
30
1996-2001
Avg. = 14.3
25
20
15
10
5
0
J
F
M
A
M
J
J
A
S
O
N
D
Data source: USGS
5
.
ee R
auk
Milw
Milwaukee region
Nearshore Phosphorus loads,
May – July 2006
River load:
120 mg P m-2
Menomonee R.
ne
Cladophora zo
Kinnickinnic R.
Mussel Excretion:
506 mg P m-2
10 km
10 km
6
The Lake Michigan
Phosphorus Cycle
P Load
Nearshore
Loop
Offshore
Loop
Phytoplankton
DP
DP
Outflow
Zooplankton
Fish
Burial
Mussels have made nearshore water clear
Mussel
invasion
Source: MMSD
7
November 2007
November 2008
8
Near-Bottom Total Dissolved Phosphorus
Atwater, Lake Michigan
10
9
8
TDP (μg/L)
(mg/L)
TDP
7
6
5
2008
4
3
2006
2007
2
1
0
May
June
July
Aug.
Sep.
Oct.
Water Temperature at 9 m
25
2006
o
Temperature ( C)
20
15
2008
10
5
0
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
9
Lake Michigan Nearshore
Summer Temperature Trend
14
Optimum for Cladophora growth
o
June - August Mean T ( C)
13
12
11
10
9
8
7
6
5
4
1970
no Cladophora growth
1975
1980
1985
1990
1995
2000
2005
TEMPERATURE
PHOSPHORUS
Quagga Mussel
Cladophora
10
Lab Experiments:
Phosphorus Excretion by Quagga Mussels
-1
μ gP mgDW hr
-1
0.02
0.018
0.016
0.014
22oC
0.012
0.01
0.008
0.006
0.004
15oC
10oC
0.002
0
0
5
10
15
20
25
30
-1
0.2
350
0.18
0.16
300
0.14
B
250
0.12
0.1
200
150
0.08
μ
no
mussels
mussels
100
0.06
0.04
50
-1
400
Growth Rate (day )
-2
Biomass (gDW m )
Food Concentration (mg P ml )
0.02
0
0
0
5
10
15
20
25
o
Temperature ( C)
30
35
11
LIGHT ?
P Flux Between Mussels and Cladophora
μg P mussel-1 hr-1
0.2
0.15
0.1
0.05
0
Clean Mussels
Dirty Mussels
Mussels + Cladophora
-0.05
-0.1
12
Current Needs
3. What is the botulism mechanism?
Photo: Alice Van Zoeren
13
4 minutes
after dye injection
14
above mussels
K = 0.1 cm2 s-1
K = 0.01 cm2 s-1
mussel bed
Depth of anoxic zone in mussel bed
Effect of benthic respiration on thickness of anoxic layer
1.2
1
0.8
0.6
0.4
0.2
0
-1000
1000
3000
5000
-2
7000
-1
O2 uptake rate (mg m d )
15
16
DO (% Sat.)
Benthic O2 uptake by mussels
10
9.5
9
8.5
8
7.5
7
5,258 mg O2 m-2 d-1
0
50
100
Time (minutes)
Depth of anoxic zone in mussel bed (cm)
Effect of benthic respiration on thickness of anoxic layer
1.2
1
0.8
0.6
0.4
0.2
0
-1000
1000
3000
5000
-2
7000
-1
O2 uptake rate (mg m d )
17
K = 0.1 cm2 s-1
K = 0.01 cm2 s-1
above mussels
mussel bed
Underwater Particle Image Velocimetry
(PIV) System
18
PIV Image Analysis Results
Qian and Bootsma, in press
19
Vertical Soluble Reactive Phosphorus Profile
Over Mussel Bed
60
Height (mm)
50
dc
F=D
dz
40
30
20
10
0
0
10
20
30
40
50
[SRP] (nmol l-1)
The Cladophora Solution
20
Bruce Mozert / University of Florida Press
21