Where’s The Peak? Observations of Tidal Marsh

Diversity Along The Patuxent and Nanticoke Rivers

ByPeter Sharpe and Andrew H. Baldwin

The University of MarylandDepartment of Environmental Science and Technology

May-August 2006

Research Objectives1. Describe plant species richness across a

salinity gradient (fresh-brackish) in tidal marshes of two Chesapeake Bay Tributaries

Ric

hn

es

s

Salinity Salinity

Ric

hn

es

s

Fresh

Brackish

Transitional

Washington D.C.Patuxent River

Patuxent River Watershed Features

Watershed Size – 2,356 km2

Gradient Length – 47 kmMean Tidal Range at Jug Bay – 0.73 mLand Use:

1. 30% Agricultural 2. 40% Forest 3. 20% Urban4. 10% Other Land Uses

Number of Survey Plots - 13

Washington D.C.Patuxent River

Nanticoke River

Nanticoke River Watershed Features

Watershed Size – 2,136 km2

Gradient Length – 56 kmMean Tidal Range at Sharptown, MD – 0.76 mLand Use:

1. 48% Agricultural 2. 41% Forest 3. 2% Urban4. 8% Other Land Uses

Number of Survey Plots - 16

Patuxent and Nanticoke River Study Sites

Patuxent River Gradient – 47 km Nanticoke River Gradient – 56 km

Bivalve Harbor

Seaford, DE

Benedict

Jug Bay

MethodsVegetation surveyed using nested plot design consisting of

a series of 10x10 m modules (Peet et al. 1998)

10

2 3

7

4

6

54

2

3

2

892

43

2

1

Piezometer Location

GPS Reading

SCT Reading

50 m

20 m

Nest (Depth) Dimensions Area

Depth 5 10 cm x 10 cm 0.01 m2

Depth 4 32 cm x 32 cm 0.1 m2

Depth 3 1m x 1m 1 m2

Depth 2 3.16m x 3.16m 10 m2

Depth 1 10m x 10m 100 m2

Residuals 20 m x 50m 1,000 m2

Typical Sampling Location

High Marsh

Le

ve

e

Lo

w M

ars

h

Surveyed Area

10 m

Nanticoke River Species Richness Results (May-August) Residual Depth

1000 m2 Survey Area

Nanticoke River Residuals - May 2006

Distance Upstream (km)

0 10 20 30 40 50 60

Nu

mb

er

of

Sp

eci

es

0

5

10

15

20

25

30

35

40

Me

an

So

il S

alin

ity (

ppt)

0

1

2

3

4

5

6

7

8

9

10Nanticoke River Residuals - August 2006

Distance Upstream (km)

0 10 20 30 40 50 60N

um

be

r o

f S

pe

cie

s0

10

20

30

40

50

Me

an

So

il S

alin

ity (

pp

t)

0

1

2

3

4

5

6

7

8

Patuxent River Species Richness Results (May-August) Residuals

1000 m2 Survey Area

Patuxent River Residuals - June 2006

Distance Upstream (Km)

0 10 20 30 40 50

Num

ber o

f Spe

cies

5

10

15

20

25

30

35

Mea

n S

oil S

alin

ity (p

pt)01234567891011

Patuxent River Resdiuals - August 2006

Distance Upstream (Km)

0 10 20 30 40 50

Num

ber o

f Spe

cies

0

5

10

15

20

25

30

35

Mea

n S

oil S

alin

ity (p

pt)

0123456789101112

Conclusions1. Nanticoke River data show no immediate reduction in

richness, actually an increase along the Nanticoke up to mean soil salinity of 3-4 ppt (peak observed at 0.8 ppt soil salinity)

3. Periodic salt water stress could promote coexistence of freshwater and brackish species

4. Other potential factors: soil nutrient concentrations, marsh hydroperiods, toxicants, invasive species

2. Patuxent River data show slight peak in June within limits of salt intrusion followed by maintenance of species richness along gradient up to 3 ppt

Acknowledgements

Project funding provided by the Maryland/D.C. Chapter of The Nature Conservancy through a Biodiversity Conservation Research Fund Grant

Special thanks to Dr. Andrew Baldwin, Dr. David Tilley, Daniel Marcin, Robbie Vocke, Krissy Rusello, Douglas Rau, and Katherine Sharpe