Great Lakes Offshore Biological Desert
and the Nearshore Slime Around the Tub
David Rockwell
Monitoring Indicators and Reporting Branch
US EPA, Great Lakes National Program
Office
Methods
• Great Lakes National Program Office
• Annual monitoring cruises, 1983-2005
– Spring unstratified (April)
– Summer stratified (August)
GLNPO Biology Program
Measures
• Phytoplankton
– Community Composition, Biomass
– Deep Chlorophyll Maximum
– Historical Communities
• Crustacean Zooplankton and Benthos
– Community Composition
– Size Structure of Community
GLNPO Sampling Stations
Different colors indicate regions
assumed to be homogeneous
Methods
• 1984-1990:
– Tows B-2 m
– 63 mm mesh net with flowmeter
– Biomass calculated from avg.
length/spp generated from 20 m tows
• 1998-2005
– 100 (or B-2 m) tows
– 153 mm mesh net with flowmeter
– 20 individuals/spp measured/sample
Zooplankton Communities in Lake Huron
1984-2005
Mary Balcer
University of Wisconsin-Superior
Richard P. Barbiero
CSC, & Loyola University Chicago
Biomass mg/m3
Total crustacean biomass with standard error bars
60000
Northern Basin
40000
20000
0
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004
160000
140000
Southern Basin
Biomass mg/m3
120000
100000
80000
60000
40000
20000
0
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004
Cladocerans Copepods
#3
#1
Cyclopoid copepod
Daphnia
#2
Bosmina
Bosmina
Diaptomid copepod
Limnocalanus
3
Biomass (mg/m )
Biomass of major taxonomic groups
40000
Huron North basin
20000
0
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
120000
Huron South basin
3
Biomass (mg/m )
100000
80000
60000
40000
20000
0
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
immature calanoids
adult calanoids
immature cyclopoids
adult cyclopoids
predatory clads
daphnid clads
non daphnid clads
Diporeia Decline
Northern Basin
3000
1000
0
1998
1999
2000
2001
2002
2003
2004
2005
Southern Basin
2500
1500
1000
500
0
1999
2000
2001
2002
2003
2004
2005
Diporeia abundance (#/m2)
2000
1998
Diporeia abundance (#/m2)
2000
Diporeia Decline
30000
Northern Basin
Biomass mg/m3
3000
20000
2000
15000
10000
1000
5000
0
0
1998
1999
2000
2001
2002
2003
2004
Diporeia abundance (#/m2)
25000
2005
120000
Southern Basin
Biomass mg/m3
2500
2000
80000
1500
60000
40000
1000
20000
500
0
0
1998
1999
2000
2001
2002
2003
2004
2005
Diporeia abundance (#/m2)
100000
Size distribution of crustacean biomass
6000
1998
5000
immature calanoids
adult calanoids
immature cyclopoids
adult cyclopoids
predatory clads
daphnid clads
South Basin
4000
3000
2000
1000
0
12000
1999
11000
non daphnid clads
10000
6000
1998
5000
9000
North Basin
4000
8000
7000
3000
6000
2000
5000
1000
4000
6000
0
3000
1999
5000
2000
4000
1000
0
6000
3000
2000
2001
5000
1000
4000
4000
0
3000
2001
3000
2000
2000
1000
1000
6000
0
6000
0
2002
5000
2002
5000
4000
4000
3000
3000
2000
2000
1000
1000
3000
0
3000
0
2003
2000
2003
2000
1000
1000
2000
0
2000
0
2004
1000
2004
1000
0
2000
2000
0
2005
1000
2005
1000
0
0
0
1
2
Length (mm)
3
4
0
1
2
Length (mm)
3
4
Lake Huron and Lake Superior
Zooplankton Communities
3
Biomass (mg/m )
Superior central basin
2004
2000
1000
0
0
1
2
3
4
Huron northern basin
3
Biomass (mg/m )
Length (mm)
2005
2000
1000
Limnocalanus macrurus
0
0
1
2
3
4
Length (mm)
Diaptomus sicilis
8000
Phosphorus Loading
Trends
Superior
6000
GLWQA
Target
4000
Recent Loads
Dolan and McGunagle 2005
0
30000
8000
Erie
Michigan
6000
20000
4000
10000
2000
0
0
8000
15000
Ontario
Huron
6000
10000
4000
5000
2000
2005
2000
1995
1990
1985
1980
1975
1970
2005
2000
1995
1990
1985
1980
1975
1970
1965
0
0
1965
P Load (tonnes yr-1)
2000
Total Phosphorus
Trends (Spring)
8
Harvey Bootsma SOLEC 2006
Superior
GLWQA Target
6
4
♦ ♦ Environment Canada
■ ■ USEPA-GLNPO
2
TP (mg L-1)
0
8
6
40
Michigan
4
20
2
10
0
0
30
25
20
15
10
5
0
15
Huron
10
5
0
1965
1970 1975
Erie Central
30
1980 1985
1990 1995
2000 2005
1965
Ontario
1970
1975 1980
1985
1990
1995 2000
2005
Plots of simulation results and data for TP (mgP/L) in the Upper
Great Lakes: (a) Superior, (b) Michigan, and (c) Huron. The waterquality objectives are shown as dashed lines.
(RWG D Annex 3 Technical Subgroup Report DePinto et al 2006)
•
Superior
Michigan
Huron
Schematic of a long-term, total phosphorus
model for the Great Lakes (Chapra 1977).
Nearshore Shunt Hypothetical Construct
Hecky et al 2004 Can.J. Fish Aquat. Sci 61
Secchi disk depths near Milwaukee, Lake Michigan
Dr. Harvey Bootsman
, SOLEC
2006For Outer Harbor Site 13
Annual Secchi
Disk Data
10
9
Mussel
invasion
8
7
6
5
4
3
Secchi (Meters)
2
1
0
1990
1992
1994
1996
1998
2000
2002
1991
1993
1995
1997
1999
2001
Median
25%-75%
Non-Outlier Range
OH-13
Databy
source:
MMSD
Data provided
MMSD
Cladophora
Lake Erie Total Phosphorus, ug-P/L
Pre(1983-1989)/Post (1990-2004)
Eastern Basin
50
45
40
35
30
25
20
15
10
5
0
1980
No
Significant
Difference
1985
1990
1995
2000
2005
2010
Central Basin
50
40
30
No
Significant
Difference
20
10
0
1980
1985
1990
1995
2000
2005
2010
Western Basin
50
45
40
35
30
25
20
15
10
5
0
1980
No
Significant
Difference
1985
1990
1995
Year
2000
2005
2010
Lake Erie Total Dissolved Phosphorus, ug-P/L
Pre(1983-1989)/Post (1990-2004)
20
Eastern Basin
15
Significant
Increase
(p=0.021)
10
5
0
1980 1985 1990 1995 2000 2005 2010
20
Central Basin
15
Significant
Increase
(p<0.001)
10
5
0
1980 1985 1990 1995 2000 2005 2010
25
Western Basin
20
No
Significant
Difference
15
10
5
0
1980
1985
1990
1995
Year
2000
2005
2010
DRP/TP
Figure courtesy of
Dr. Peter Richards, Heidelberg College
Maumee
Cuyahoga
Sandusky
Grand
Sandusky and Maumee River Watersheds
Lake Erie
Figure courtesy of Dr. Peter Richards, Heidelberg College
P in Wisconsin Cropland
50
40
30
20
Average [P] (ppm)
60
10
0
1968- 1974- 1978- 1982- 1986- 1991- 199573
77
81
85
90
94
99
Bundy and Sturgul 2001
Long-term Influence of Soil P on Lake P
Soil P inputs reduced after year 250
Phosphorus Density (g m-2)
Soil [P]
1000
1000
Sediment [P]
100
100
P Input to soil
10
10
Water [P]
P Inputs to Soil (g m-2 y-1)
10000
10000
1
1
0
500
1000
1500
2000
Years
Source: S.R. Carpenter, 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
Long-term Influence of Soil P on Lake P
Soil P budget balanced at year 250
Phosphorus Density (g m-2)
Soil [P]
1000
1000
Sediment [P]
100
100
P Input to soil
Water [P]
10
10
1
1
0
200
400
600
800
P Inputs to Soil (g m-2 y-1)
10000
10000
1000
Years
Source: S.R. Carpenter, 2005
Summary
•
Offshore Declines in Zooplankton Biomass are observed Lake Huron.
•
Phosphorus loads and open lake phosphorus concentrations have declined
in the Great Lakes in response to controls
•
Top down effects are observed to contribute to decline in the lower food
web.
•
Nearshore Cladophora increases appear to be link to Dreissena invasion
via increased water clarity and cycling of nutrients
•
Total phosphorus loading has increased soluble fraction and open lake
concentrations in Lake Erie have a significant increase in soluble fraction in
the spring.
•
Total phosphorus concentrations in the Upper Great Lakes appear to below
levels modeled to exist in 1800.
 Dissolved Reactive Silica increases in Lakes Michigan and Huron are linked
to TP declines.
 Dissolved Reactive Silica increases in Lake Erie are linked to predation by
Dreissena
Nearshore shunt of nutrients redirected to the nearshore zones of the Lakes
contributing to the reemergence of Cladophora while offshore P concentrations
remain low.
Continued addition of P to soils may pose a challenge to the lakes well into
the future.
 In the nearshore zone, increased water clarity has altered the relationship
between P supply and algal abundance.
 More P abatement would benefit the nearshore zone, but would it benefit
pelagic zone?