Nuisance Cladophora Blooms in Lake Michigan: Possible Causes and Management Options Harvey Bootsma...
-
Upload
gianna-wheatley -
Category
Documents
-
view
218 -
download
0
Transcript of Nuisance Cladophora Blooms in Lake Michigan: Possible Causes and Management Options Harvey Bootsma...
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
•• • ••••
••
•
•
•
•
•
•
•
••
• ••
• ••••
• •
•• •
• • •• •
• •• • ••
•
•
•• • •••• ••
•
• •••
• • • •••
••
•
•
•
•
•
••
•
• •
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
P
1990
5 m
12oC
River P
••••
•
•
•
••
•• ••• •• ••
•••••••••
•
• ••••
•
• ••
•
•
•
•
• •••
•• •
••
• •
•
•
•
• •
•
• •
•
•
•
••
•
•
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?