Submerged aquatic vegetation (SAV) abundance and diversity in the tidal Potomac River and estuary

By Nancy Rybicki, Jurate Landwehr, Edward Schenk, and Julie Baldizar

Goal: provide managers with information to help them understand variation in SAV coverage and determine strategies to meet the SAV restoration goal.

Tidal Fresh SAV

0

1000

2000

3000

78 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04

Years

SAV restoration goal based on historical coverage (1930's and 1950's)

Variation in SAV coverage, Potomac RiverSAV data from http://www.vims.edu/bio/sav :

Oligohaline SAV

0

5001000

1500

2000

78 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04

Years

SA

V (

Hec

tare

s)

SAV restoration goal based on historical coverage (1930's and 1950's)

Mesohaline Potomac SAV

01000200030004000

1978

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

SAV restoration goal based on historical coverage (1930's and 1950's)

No

data

River Flow

Phyto-plankton

Nutrients

Water Temperature

Total SuspendedSolids

Epiphytes

Solar radiation

Submersed Aquatic Vegetation

Light

Wind Speed

Water clarity is the primary factors influencing SAV abundance.

Literature review and analyses indicated MLRs of13% light for the fresh and oligohaline and22% for mesohaline to polyhaline SAV community (Carter et al. 2000, Batiuk et al. 2000, Kemp, et al. 2004)

Secchi depth of 0.7m = 13% light at 1m

1) EVALUATION OF SUBMERGED AQUATIC VEGETATION (SAV) AND WATERFOWL POPULATIONS WITH RESPECT TO EXOTIC SPECIES AND IMPROVING WATER QUALITY

2) POSSIBLE CAUSE OF VIRGINIA TRANSPLANTS 2003 & 2004

3) MAP SHOWING POTENTIAL AND CONTINUEING USGS WORK

Study Area

Improved water quality in an estuary with exotics enhances SAV diversity and waterfowl habitat,

by Rybicki and Landwehr

Data source:

SAV species, USGS and DC gov’t

SAV coverage, VIMS

Water quality, MDDNR

Waterfowl, Audobon Christmas bird count

Rybicki and Landwehr, in process

UTR

0

200

400

600

800

1000

1200

1400

1985

1987

1989

1991

1993

1995

1997

1999

2001

Other exotic Hydrilla

Native No species data

UOE

0

200

400

600

800

1000

1985

1987

1989

1991

1993

1995

1997

1999

2001

Other exotic Hydrilla verticillata

Native No species data

*****

LTR

0

200

400

600

800

1000

1985

1987

1989

1991

1993

1995

1997

1999

2001

Pro

du

ctiv

ity

(hec

tare

s)

Other exotic Hydrilla

Native No species data

0

500

1,000

1,500

0 500 1,000 1,500

SAV productivy previous year (ha)

SA

V p

rod

uct

ivit

y (h

a)

UTR LTR UOE Linear (All segments)

0

0.5

1

1.5

2

0 1 2 3

Total nitrogen (mg l-1)

Div

ersi

ty in

dex

UTR LTR UOE Linear (All segments)

SAV productivity is density specific SAV coverage, in hectares

0

50

100

150

200

250

1959

1962

1965

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

Wa

terf

ow

l co

un

t h

r-1 e

ffo

rt

0

500

1000

1500

2000

2500

SA

V (

he

cta

res

)

Waterfowl * SAV

Period 1 Myriophyllum present

Period 3 SAV returns, Hydrilla dominant

Period 2 No SAV

*******

Period

Wat

erfo

wl c

ou

nt

hr

-1 e

ffo

rt

0

10

20

30

40

50

80

100Oxyura

jamaicensisAthya affinis

and A. marila

Anasplatyrhynchos

Brantacanadensis

Aythyavalisineria

Fulicaamericana

Anasrubripes

Mergusmerganser

1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3

Period 1 = 1959-1966Period 2 = 1966-1982Period 3 = 1982-2001

A

BB

A

BAB

A

BB A

B AB

A

BAB

A

B

C

A

B B

A

B

C

(Ruddy) (Scaup sp.)

(Mallard) (Canada Goose)

(Canvas-back)

(Common Merganser)

(American Black)

(American Coot)

Conclusions 1985-2001 Potomac River-

Productivity of native, as well as exotic, SAV species was shown to vary with factors affecting water column light attenuation (TSS, Chlorophyll a).

Winter waterfowl increased significantly with SAV coverage, despite dominance by exotics.

SAV productivity was largely driven by Hydrilla productivity 1985-2001

Previous years propagules (tubers, seeds, etc) may dampen the effect of environmental variation

Our findings support management strategies to improve water clarity and reduce nutrient concentration in order to protect diversity and waterfowl habitat

Exploring Causes of a Seagrass Transplant Failure in the Potomac River (Virginia) –Mitigation for loss of SAV at Wilson Bridge construction site

We monitored a seagrass transplant site (Judith Sound) and a reference site (Dameron Marsh), in VA. The transplant site was one of six SAV transplant sites in the Potomac that have only been marginally successful since transplanting began in 2000 (written communication, Justin Reel) .

March to November, of 2003 and 2004, at both sites we measured habitat variables monthly, including sedimentation and erosion, shoot length and burial, salinity, and light attenuation.

Natural eelgrass at reference site and eelgrass tranplanted in fall 02 and fall 03 (written communication, Justin Reel) did poorly in 2003 and 2004

Figure 1. Precipitation and salinity during 2003 and 2004 at the transplant site and reference site. Precipitation data from Norfolk International Airport

Exploring Causes of a Seagrass Transplant Failure in the Potomac River (Virginia) –Mitigation for loss of SAV at Wilson Bridge construction site

1) Both sites were above the median 22 percent light level

2) The percent of shoot that was buried was greater at the transplant site (22 percent) than at the reference site (11 percent), although both percentages were below levels shown to be detrimental to eelgrass survival (Veermaat and others 1997).

3) Monitoring data support the conclusion that salinity not erosion or accretion, were the primary factors responsible for the decline of eelgrass at both sites.

4) Low sediment fertility may also play a role in lack of success at the eelgrass transplant site.

Exploring Causes of a Seagrass Transplant Failure in the Potomac River (Virginia) –Mitigation for loss of SAV at Wilson Bridge construction site

2003 SAV

Maryland

Potomac integrative analysis will enhance USGS SAV studies and other potential studies to explain ecosystem change to help assess the effectiveness of restoration strategies

Relationship between environmental variables and species of SAV

Field investigations of SAV health, sediment characteristics, water quality, and maximum depth of SAV, w/ many cooperators

Tracking sediment sources using isotopic tracers (Allen Gellis, USGS)

Dameron Marsh natural SAV health as a reference site for SAV transplantsImage from MDDNR website

Wetland restoration and sediment accretion studies