Eelgrass in Salem Sound: Abundance and Values

Robert BuchsbaumMassachusetts Audubon Society

Eelgrass habitat values

• A rich, productive habitat for many marine organisms– Nursery habitat for fish and invertebrates– Feeding area for many waterfowl, fish, and

invertebrates– Consumed directly or

as detritus• Filter of nutrients• Stabilizer of sediments

Paul Erickson

Distribution of eelgrass in Salem Sound

West Beach

Beverly Cove (off Patch Beach)

Beverly Cove

1989 flyover

Manchester Harbor

1989 flyover

Atlantic Brant and Wasting Disease

1997-1998 SSCW SCUBA surveys

eelgrass

mud

1997-1998 SCUBA Surveys Hospital Point eelgrass v Curtis Point

mud

Lobsters at mud site

0

2

4

6

8

10

12

14

16

18

20

15-Jun-97

19-Jul-97

13-A ug-

97

07-S ep-

97

04-Jan-98

22-F eb-

98

05-A pr-98

22-M ay -

98

S a m p lin g D a te

Num

ber o

f Lob

ster

s p

er T

rans

ect

Ha b ita t: S a nd ,S ilty M ud

Lobsters at Eelgrass site

0

2

4

6

8

10

12

14

16

18

2012

-Jun

-97

21-J

un-9

7

12-J

ul-9

7

26-J

ul-9

7

31-A

ug-9

7

14-S

ep-9

7

11-O

ct-9

7

03-J

an-9

8

15-F

eb-9

8

15-M

ar-9

8

12-A

pr-9

8

30-A

pr-9

8

Sampling Date

Num

ber o

f Lob

ster

s p

er T

rans

ect

Habitat:Eelgrass

Winter Flounder in mud site

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

1 5 -J u n -9 7

1 9 -J u l -9 7

1 3 -A u g -

9 7

0 7 -S e p -

9 7

0 4 -J a n -

9 8

2 2 -F e b -

9 8

0 5 -A p r-9 8

2 2 -M a y -

9 8

S a m p lin g D a te

Num

ber o

f Flo

unde

r

per t

rsan

sect

H a b i ta t: S a n d , S i lty M u d

L i k e ly w i n te r f lo u n d e r , b u t n o t p o s i t i ve ly i d e n ti f i e d to s p e c i e sd u e to tu rb i d w a te r

Winter Flounder in Eelgrass

0

5

10

15

20

25

30

35

40

12-J

un-9

7

21-J

un-9

7

12-J

ul-9

7

26-J

ul-9

7

31-A

ug-9

7

14-S

ep-9

7

11-O

ct-9

7

03-J

an-9

8

15-F

eb-9

8

15-M

ar-9

8

12-A

pr-9

8

30-A

pr-9

8

N o te d i ffe re nc e in s c a lec o m p a re d to o the r s ta tio ns

Num

ber o

f Flo

unde

r p

er T

rans

ect H ab ita t: E e lg r a s s

D ata s h ee t g rou pe d a ll flo un de rs . M o s t p rob ab ly th ey a re

w in te r flo un de r

Striped Bass

1997 DMF Trawl Surveys

• Beverly Cove eelgrass habitat had the highest fish diversity of the 6 stations– 17 species of fish

1. Cunner2. Pipefish3. Winter Flounder

– 7 decapods (lobsters, crabs, shrimp)– 2 other invertebrate species

The Massachusetts Oceans Act-2008

from Section 2:• The [ocean management] plan shall:

– (v) value biodiversity and ecosystem health – (vi) identify and protect special, sensitive or

unique estuarine and marine life and habitats• Scope is MA coastal water from 0.5 km

out to seaward boundary .

Criteria used for comparing values different types of marine habitats

Standard / Condition ScoreRare, unique, and/or sensitive habitat. Identified as critical habitat for endangered or threatened species (e.g.,nesting, staging) where there are no or very few other areas exist that provide similar structure or function.

3

Exceptional and somewhat unique habitat and/or habitat with high vulnerability. These are habitat areas wherefew others exist providing similar structure or function

2

Important habitat and/or habitat or resources susceptible to adverse impacts. Identified as areas that supportendangered, threatened, or special concern species or other important species, but where use is general oroccurs over large geographic areas.

1

From Mass Ocean Mgmt Habitat Working Group draft report-11/26/08

Biotic data used in ranking Habitat RankingRoseate Tern breeding and staging 3North Atlantic Right Whales 3Humpback Whale concentrations 3Fin whale concentrations 3Sei Whale concentrations 2SAV – eelgrass and wigeongrass 2Colonial waterbird nesting colonies 2Leach’s Storm Petrel nesting 2Common, Least and Arctic tern nesting and staging

2Common, Least and Arctic tern foraging 1Long-tailed Duck winter habitat 1Other marine seaducks and waterbirds 1Seal haul out islands 1

From Mass Ocean Mgmt Habitat Working Group draft report-11/26/08

Seagrass landscapesFonseca and Bell 1998. MEPS

Fonseca and Bell suggest cover threshold of 59% below which there would be functional effects or changes of associated organisms.

Cover of seagrass is a response to:

• Internal regulation of growth:– Rhizome elongation rates and branching

which are effected by:• Sediment type• Light levels• Nutrients

Factors influencing the development of eelgrass meadows• External natural factors

– Wave and current exposure– Current speed– Water depth– Herbivory

• Human disturbances– Trawling– Moorings– Boat wakes

From MassGIS seagrasscoverage

Distribution of eelgrass in Salem Sound

Effects of seagrass patch size – natural beds

Bostrom et al. 2006 Est. Coast. ShelfSci.

Num

ber of Studies

As a group, only bivalves seem to show more positive associations with larger seagrass patch sizes. Lower mortality in larger patches

Patch size effects on settling of larvae, feeding potential, and

movements of predatorWater movement Water movement

Former Habitat

http://www.buzzardsbay.org/eelgrass.htm

Potential Habitat – Abioticcriteria

http://www.buzzardsbay.org/eelgrass.htm

Hypothetical distribution of eelgrass in Buzzards Bay ca. 1600 based on depth contours.

Final thoughts

• All seagrass patches in New England waters, large or small, have habitat value far beyond that of unvegetated adjacent areas

• The mosaic of an eelgrass meadow includes vegetated and unvegetated areas that interact to support other species.

• We should be protecting potential habitat as well as existing eelgrass meadows.