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 m mesh net with flowmeter– Biomass calculated from avg.

length/spp generated from 20 m tows

• 1998-2005– 100 (or B-2 m) tows– 153 m mesh net with flowmeter– 20 individuals/spp measured/sample

Mary Balcer   Richard P. BarbieroUniversity of Wisconsin-Superior CSC, & Loyola University Chicago 

Zooplankton Communities in Lake Huron1984-2005

Total crustacean biomass with standard error bars

Northern Basin

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004B

iom

ass

g

/m3

0

20000

40000

60000

Southern Basin

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

Bio

ma

ss

g/m

3

0

20000

40000

60000

80000

100000

120000

140000

160000

Daphnia

Bosmina

Cyclopoid copepod

Diaptomid copepod

Limnocalanus

#1#1#3#3

#2#2

Cladocerans Copepods

Bosmina

Biomass of major taxonomic groups

Huron North basin

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006

Bio

mas

s (

g/m

3 )

0

20000

40000

Huron South basin

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006

Bio

mas

s (

g/m

3 )

0

20000

40000

60000

80000

100000

120000

non daphnid clads

daphnid cladspredatory clads

adult cyclopoidsimmature cyclopoidsadult calanoidsimmature calanoids

Diporeia DeclineNorthern Basin

1998 1999 2000 2001 2002 2003 2004 2005

Dip

ore

ia abu

nda

nce

(#/m

2)

0

1000

2000

3000

Southern Basin

1998 1999 2000 2001 2002 2003 2004 2005

Dip

ore

ia abu

nda

nce

(#/m

2)

0

500

1000

1500

2000

2500

Diporeia DeclineNorthern Basin

1998 1999 2000 2001 2002 2003 2004 2005

Bio

mas

s g

/m3

0

5000

10000

15000

20000

25000

30000

Dip

ore

ia abu

nda

nce

(#/m

2)

0

1000

2000

3000

Southern Basin

1998 1999 2000 2001 2002 2003 2004 2005

Bio

mas

s g

/m3

0

20000

40000

60000

80000

100000

120000

Dip

ore

ia abu

nda

nce

(#/m

2)

0

500

1000

1500

2000

2500

non daphnid clads

daphnid cladspredatory clads

adult cyclopoidsimmature cyclopoidsadult calanoidsimmature calanoids

1998

0

1000

2000

3000

4000

5000

6000

1999

0

1000

2000

3000

4000

5000

6000

2001

0

1000

2000

3000

4000

2002

0

1000

2000

3000

4000

5000

6000

2003

0

1000

2000

3000

2004

0

1000

2000

2005

Length (mm)0 1 2 3 4

0

1000

2000

1998

0

1000

2000

3000

4000

5000

6000

1999

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

2001

0

1000

2000

3000

4000

5000

6000

2002

0

1000

2000

3000

4000

5000

6000

2003

0

1000

2000

3000

2004

0

1000

2000

2005

Length (mm)0 1 2 3 4

0

1000

2000

Size distribution of crustacean biomass

North Basin

South Basin

2005

Length (mm)0 1 2 3 4

Bio

mas

s (

g/m

3)

0

1000

2000

2004

Length (mm)0 1 2 3 4

Bio

mas

s (

g/m

3)

0

1000

2000

Superior central basin

Huron northern basin

Diaptomus sicilis

Limnocalanus macrurus

Lake Huron and Lake Superior Zooplankton Communities

0

10000

20000

30000

0

5000

10000

15000

1965

1970

1975

1980

1985

1990

1995

2000

2005

0

2000

4000

6000

8000

0

2000

4000

6000

8000

1965

1970

1975

1980

1985

1990

1995

2000

2005

0

2000

4000

6000

8000

Phosphorus Loading Trends

Recent Loads Dolan and McGunagle 2005

Michigan

P L

oad

(to

nn

es y

r-1)

Superior

Erie

OntarioHuron

GLWQATarget

0

10

20

30

40

0

5

10

15

1965 1970 1975 1980 1985 1990 1995 2000 200505

1015202530

1965 1970 1975 1980 1985 1990 1995 2000 2005

0

2

4

6

8

Total Phosphorus Trends (Spring)

Harvey Bootsma SOLEC 2006

Michigan

TP

(g

L-1)

♦■ ■

♦ Environment CanadaUSEPA-GLNPO

Huron Ontario

Erie Central

0

2

4

6

8 SuperiorGLWQA Target

Superior

Michigan

Huron

Plots of simulation results and data for TP (gP/L) in the Upper Great Lakes: (a) Superior, (b) Michigan, and (c) Huron. The

water-quality objectives are shown as dashed lines. (RWG D Annex 3 Technical Subgroup Report DePinto et al 2006)

• 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

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

Secchi disk depths near Milwaukee, Lake Michigan

Dr. Harvey Bootsman, SOLEC 2006

Data source: MMSD

Cladophora

Lake Erie Total Phosphorus, ug-P/L Pre(1983-1989)/Post (1990-2004)

Central Basin

0

10

20

30

40

50

1980 1985 1990 1995 2000 2005 2010

NoSignificantDifference

Eastern Basin

0

5

10

15

20

2530

35

40

45

50

1980 1985 1990 1995 2000 2005 2010

NoSignificantDifference

Western Basin

05

101520253035404550

1980 1985 1990 1995 2000 2005 2010Year

NoSignificantDifference

Lake Erie Total Dissolved Phosphorus, ug-P/LPre(1983-1989)/Post (1990-2004)

Eastern Basin

0

5

10

15

20

1980 1985 1990 1995 2000 2005 2010

SignificantIncrease(p=0.021)

Central Basin

0

5

10

15

20

1980 1985 1990 1995 2000 2005 2010

SignificantIncrease(p<0.001)

Western Basin

0

5

10

15

20

25

1980 1985 1990 1995 2000 2005 2010Year

NoSignificantDifference

DRP/TPMaumee

Sandusky

Cuyahoga

Grand

Figure courtesy of Dr. Peter Richards, Heidelberg College

Sandusky and Maumee River Watersheds Lake Erie

Figure courtesy of Dr. Peter Richards, Heidelberg College

Ave

rage

[P

] (p

pm)

P in Wisconsin Cropland

Bundy and Sturgul 2001

0

10

20

30

40

50

60

1968-73

1974-77

1978-81

1982-85

1986-90

1991-94

1995-99

1

10

100

1000

10000

0 500 1000 1500 2000

1

10

100

1000

10000

P Input to soil

Water [P]

Soil [P]

Sediment [P]

YearsSource: S.R. Carpenter, 2005

Long-term Influence of Soil P on Lake PSoil P inputs reduced after year 250

Ph

osp

ho

rus

De

nsi

ty (

g m

-2)

P In

pu

ts t

o S

oil

(g m

-2 y

-1)

0

1

2

3

4

5

1970 1975 1980 1985 1991 1994 1995

Ave

rage

[P

] (p

pm)

Soi

l P S

tora

ge C

hang

e (k

g ha

-1)

P in Wisconsin Cropland

Bundy and Sturgul 2001

0

10

20

30

40

50

60

1968-73

1974-77

1978-81

1982-85

1986-90

1991-94

1995-99

1

10

100

1000

10000

0 200 400 600 800 1000

1

10

100

1000

10000

Ph

osp

ho

rus

De

nsi

ty (

g m

-2)

P In

pu

ts t

o S

oil

(g m

-2 y

-1)

Long-term Influence of Soil P on Lake PSoil P budget balanced at year 250

P Input to soil Water [P]

Soil [P]

Sediment [P]

YearsSource: 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.

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?

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.