Nuisance Nuisance Cladophora Cladophora Blooms in Lake Blooms in Lake Michigan: Michigan: Possible Causes and Management Options Possible Causes and Management Options Harvey Bootsma Harvey Bootsma Erica Young Erica Young John Berges John Berges
Dec 15, 2015
Nuisance Nuisance CladophoraCladophora Blooms in Lake Michigan: Blooms in Lake Michigan:
Possible Causes and Management OptionsPossible Causes and Management Options
Harvey BootsmaHarvey BootsmaErica YoungErica YoungJohn BergesJohn Berges
Temperature at 10 m, Atwater
0
5
10
15
20
25
31-May-03 30-Jun-03 31-Jul-03 30-Aug-03 30-Sep-03 30-Oct-03 30-Nov-03 30-Dec-03 30-Jan-04 29-Feb-04 31-Mar-04 30-Apr-04 31-May-04 30-Jun-04 31-Jul-04 30-Aug-04 30-Sep-04
Date
Tem
per
atu
re (
oC
)
J J A S O N D J F M A M J J A S O 2003 2004
Optimum for Cladophora growth
456789
1011121314
1975 1980 1985 1990 1995 2000YEAR
Temperature at the Linnwood Intake (15 m)
Optimum for Cladophora growth
No growth
0
1
2
3
4
5
6
7
1-Jul-04 31-Jul-04 31-Aug-04 30-Sep-04 31-Oct-040
1
2
3
4
5
6
7
1-Jul-04 31-Jul-04 31-Aug-04 30-Sep-04 31-Oct-04
+ive growth
Growth optimum at > 26 mol m-2 d-1
-ive growth-ive growth
July Aug Sep Oct
PA
R (
mo
l p
ho
ton
s m
-2 d
-1)
Date
Irradiance at 10 m, Atwater
Annual Secchi Disk Data For Outer Harbor Site 13
Secch
i (Meters) Median
25%-75% Non-Outlier Range
OH-13
19901991
19921993
19941995
19961997
19981999
20002001
20020
1
2
3
4
5
6
7
8
9
10
Data provided by MMSD
Musselinvasion
0
1
2
3
4
5
6
7
1-Jul-04 31-Jul-04 31-Aug-04 30-Sep-04 31-Oct-04
+ive growth
-ive growth-ive growth
July Aug Sep Oct
PA
R (
mo
l p
ho
ton
s m
-2 d
-1)
Date
Irradiance at 10 m, Atwater
2004
1991
Influence of P on Cladophora Growth RateN
et
Speci
fic
Gro
wth
Rate
(d
-1)
0.6
0.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.4
0.2
Stored Phosphorus (%P)
0.8
0
0.05
0.1
0.15
0.2
0.25
0.3
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
mg
/L
SRP
TP
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01
20-Year Phosphorus Trend at River Junction
Milwaukee River = 250 kg/day
P Sources in the nearshore zone (0 – 10 m)
Mussel recycling = 1,700 kg/daygg
Cladophora demand ~ 2,000 kg/day
June July Aug Sep Oct0
0.5
1
1.5
2
0
50
100
150
200
m3 s
-1
May June July Aug Sep Oct
2004
2005
2006
Milwaukee River discharge
3-Year Comparison of Cladophora phosphorus contentLake Michigan
Cladophora P content
g P
mg
-1
2004
2005
2006
P limitedgrowth
8oC
River P
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•
•
•
•
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•
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P
1990
5 m
12oC
River P
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P
2005
10 m
Net
Speci
fic
Gro
wth
Rate
(d
-1)
0.6
0.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.4
0.2
Stored Phosphorus (%P)
0.8
Influence of P on Cladophora Growth Rate
Conclusions
The recent increase in Cladophora growth is likely due to:
- Increased water clarity (more light at lake bottom)
- Warmer water temperatures in summer
- increased phosphorus inputs
Although P input from rivers has increased, there must also be an internal source of P in the lake that is promoting Cladophora growth. We suspect dreissenid mussels.
Future work must focus on the fate of river-borne phosphorus, and the importance of mussels as a phosphorus source.
An important question to answer: If we lower P input from rivers, will there be less Cladophora?