Eelgrass survey for Eastern Long Island Sound, Connecticut and New York

              Eelgrass Survey for Eastern Long Island Sound, Connecticut and New York
Ralph Tiner1, Herb Bergquist1, Tom Halavik2 and Andrew MacLachlan2
1U.S. Fish and Wildlife Service
National Wetlands Inventory Program
Northeast Region
300 Westgate Center Drive
Hadley, MA 01035
2U.S. Fish and Wildlife Service
Southern New England Coastal Program
3769 D Old Post Road
Charlestown, RI 02813
Prepared for:
Connecticut Department of Environmental Protection
Office of Long Island Sound Programs
79 Elm Street
Hartford, CT 06106
National Wetlands Inventory Report
April 2003
This report should be cited as:
Tiner, R., H. Bergquist, T. Halavik, and A. MacLachlan. 2003. Eelgrass Survey for
Eastern Long Island Sound, Connecticut and New York. U.S. Fish and Wildlife Service,
National Wetlands Inventory Program, Northeast Region, Hadley, MA. National
Wetlands Inventory report. 14 pp. plus Appendices.
Table of Contents
Page No.
Introduction 1
Methods 3
Results 7
Field Review 7
Extent of Eelgrass 9
Historic Data 11
Summary 12
Acknowledgments 13
References 14
Appendix A. Maps showing distribution of eelgrass beds located during this inventory
Appendix B. Maps showing historical data combined with the results of this inventory
1
Introduction
The Office of Long Island Sound Programs (OLISP) within the Connecticut Department
of Environmental Protection (DEP) is responsible for assessing and restoring natural
habitats in the Long Island Sound ecosystem. In 2001, the OLISP contacted the U.S.
Fish and Wildlife Service (Service) about undertaking a survey of eelgrass beds in Long
Island Sound. The survey would be conducted through application of photointerpretation
techniques with some field checking. The Service's National Wetlands Inventory
Program (NWI) has been mapping wetlands and deepwater habitats through air
photointerpretation techniques since the mid-1970s and had recently completed
preliminary mapping of submerged aquatic vegetation for the Peconic Estuary in eastern
Long Island, New York. The Service and the DEP developed a cooperative agreement to
perform an eelgrass inventory for the eastern end of Long Island Sound, which included
acquiring tide-synchronized true color photographs for maximum resolution of eelgrass
beds.
This report outlines the methods used in the survey, summarizes inventory results, and
provides detailed maps showing the location of eelgrass beds detected during the survey.
Study Area
The project area encompasses the eastern end of Long Island Sound, including Fishers
Island and the North Fork of Long Island (Figure 1). It included all coastal embayments
and nearshore waters (i.e., to a depth of –15 feet at mean low water) bordering the Sound
from Clinton Harbor to the Rhode Island border and including Fishers Island and the
North Shore of Long Island from Southold to Orient Point and Plum Island. The study
area includes the tidal zone of 18 sub-basins in Connecticut: Little Narragansett Bay,
Stonington Harbor, Quiambog Cove, Mystic Harbor, Palmer-West Cove, Mumford Cove,
Paquonock River, New London Harbor, Goshen Cove, Jordan Cove, Niantic Bay, Rocky
Neck State Park, Old Lyme Shores, Connecticut River, Willard Bay, Westbrook Harbor,
Duck Island Roads, and Clinton Harbor, and two areas in New York: Fishers Island and a
portion of the North Shore of Long Island.
2
Figure 1. Location of eelgrass survey study area, with sub-basins designated.
3
Methods
Acquisition of Aerial Photography
Aerial photography for mapping eelgrass beds and other submerged aquatic vegetation
must meet certain requirements for the best level of bed resolution. The National
Oceanic and Atmospheric Administration's Coastal Change Analysis Program has
developed aerial photography specifications for such mapping (Dobson et al. 1995). June
is the recommended flying time for submersed rooted vascular plants in the Northeast.
Aerial photos acquired for this project met these specifications; the Service acquired
1:19,200 true color aerial photography captured during low tide on June 18, 2002. Figure
2 shows an example of a portion of one aerial photo used in this study.
Eelgrass Database Construction
Eelgrass beds were detected through aerial photointerpretation techniques using a digital
transfer scope (DTS). The DTS allowed identification and delineation of suspected
eelgrass beds and simultaneous creation of a digital database. Digital orthophoto quarter-quads
(DOQQs; obtained from: http://magic.lib.uconn.edu/index.html) served as base data
for this inventory for geospatial registration of beds and historical data.
After initial photointerpretation and digital database construction, draft maps were
prepared for field review. Data were displayed on coastal geodetic survey (navigation)
maps to show bed locations relative to recognizable landmarks for field review. Aerial
photos plus these maps were used to help locate interpreted beds for inspection. An
underwater video camera mounted on an aluminum pole was used to examine potential
eelgrass beds where beds or bottoms were not visible from the boat.
Biologists estimated the density of eelgrass in the beds by eye from the boat or by area
observation using the underwater camera. No quantitative analysis of stem density was
recorded, so density estimates are approximate. Eelgrass beds were placed in three
potential categories based on relative density of vegetation: high, medium, and low. As a
general guide, low density beds had an estimated shoot density of less than 20 percent
cover of shoots per square meter; medium density beds - 20 to 60 percent shoot density;
high density beds - 60 percent or higher (Figure 3). A sample of the field form is
presented as Figure 4.
Field work was performed by Service personnel from our Southern New England Coastal
Program Office (SNEP), with assistance from Regional NWI personnel. Cornell
Cooperative Extension Service, Marine Program (CMP) inspected the North Shore of
Long Island. Eleven days were spent in the field verifying locations of potential eelgrass
beds during the summer and early fall of 2002 (September 18, 19, and 29; October 3, 4,
8, 10, 15, 18, 22, and 28) by SNEP. CMP spent two days (November 4 and 20, 2002)
searching for eelgrass beds on the North Shore. A total of 246 sites were inspected;
specific locations (latitude/longitude) of these sites were recorded using ground
positioning system (GPS) technology by SNEP. These data were added to the digital
4
database. Data were not recorded in this manner from field inspections of the North
Shore covered the area from Goldsmith's Inlet to Mulford Point and from preliminary
field work by SNEP in the Little Narragansett Bay area.
Based on field review comments, aerial photos were re-examined, needed revisions
made, and the eelgrass database was finalized.
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Figure 2. Portion of true color aerial photograph (1:19,200) showing eelgrass beds
(marked by arrows).
5
Figure 3. Underwater view of an eelgrass bed that was typical of our observations.
6
Figure 4. Blank field data form.
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Submerged Aquatic Vegetation Field Data Sheet
Project: Eastern Long Island Sound
Investigators:____________________________________________________________
Date of Investigation: ____________
Predicted Tidal Data: Time of High Tide ________ Height ______ feet
Field Site Data:
Site #:____ Location (lat/long):___________________________________________dd
Map Name/State: ___________________ Estuary/Bay Name: ____________________
Time: _____ Water Depth:____ ft Eelgrass Present? Y N Estimated Cover: H M L
Other Species? Rockweed Other Algae Other
Comments: _____________________________________________________________
_______________________________________________________________________
Site #:____ Location (lat/long):___________________________________________dd
Map Name/State: ___________________ Estuary/Bay Name: ____________________
Time: _____ Water Depth:____ ft Eelgrass Present? Y N Estimated Cover: H M L
Other Species? Rockweed Other Algae Other
Comments: _____________________________________________________________
_______________________________________________________________________
Site #:____ Location (lat/long):___________________________________________dd
Map Name/State: ___________________ Estuary/Bay Name: ____________________
Time: _____ Water Depth:____ ft Eelgrass Present? Y N Estimated Cover: H M L
Other Species? Rockweed Other Algae Other
Comments: _____________________________________________________________
_______________________________________________________________________
Site #:____ Location (lat/long):___________________________________________dd
Map Name/State: ___________________ Estuary/Bay Name: ____________________
Time: _____ Water Depth:____ ft Eelgrass Present? Y N Estimated Cover: H M L
Other Species? Rockweed Other Algae Other
Comments: _____________________________________________________________
_______________________________________________________________________
7
Results
Field Review
Out of a total of 246 field sites, 112 were found to have eelgrass (Zostera marina) (Table
1). Of these sites, 11 had high cover, 83 had medium cover, 6 had medium to low cover,
and 12 had low cover. Sites lacking eelgrass had varying amounts of other submerged
aquatic vegetation including rockweeds (Fucus and Ascophyllum) attached to underwater
boulders and bedrock outcrops and other algae, or were devoid of such vegetation. Nine
small eelgrass beds (not photointerpretable) were identified on the seaward side of
Fishers Island. For the database, each of these field check sites was given a 10m buffer
for producing an area estimate of slightly less than 0.1 acre.
Field observations about water depth at which eelgrass was observed relative to predicted
high tide are summarized for selected areas in Table 2. Eelgrass beds were found at
water depths ranging from 4.5 feet to 16.0 feet (Site 74a). The deepest reading came
within 4 hours of predicted high tide and the predicted tide for the day of inspection was
3.4 feet.
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Table 1. Number of field check sites in each sub-basin and number with eelgrass beds.
# of # with # of # with
Sub-basin Sites Eelgrass Sub-basin Sites Eelgrass
Fishers Island (NY) 63 32 Goshen Cove 7 7
Mystic Harbor 14 9 Palmer-West Cove 10 1
Quiambog Cove 10 9 Stonington Harbor 6 5
Jordan Cove 9 6 New London Harbor 9 7
Niantic Bay 17 9 Connecticut River 6 0
Westbrook Harbor 28 0 Willard Bay 2 0
Clinton Harbor 12 0 Duck Island Roads 8 2
Little Narragansett Bay 6 6 Mumford Cove 12 12
Paquonock River 6 6
8
Table 2. Examples of observed water depth for eelgrass beds in eastern Long Island
Sound. Note: Tide predictions are based on expected tide at New London State Pier.
Predicted values for sites are mostly within 1.0 foot and 1/2 hour of predicted values for
New London. Of course, the actual time and height of tide on day of record varies due to
weather conditions. (Source data for predicted tide: http://www.tidelinesonline.com)
Site Study Depth of Time Predicted Predicted
# Sub-basin Eelgrass Observed Time of Height of
(ft) High Tide High Tide (ft)
116 Mystic Harbor 5.0 1:55PM 11:17AM 3.9
201a Mystic Harbor 11.0 4:30PM 11:17AM 3.9
105 New London Harbor 7.0 10:05AM 8:05 AM 3.1
125a Fishers Island 10.0 11:30AM 7:17AM 2.8
126 Fishers Island 6.0 12:00PM 7:17AM 2.8
123a Fishers Island 4.5 12:34PM 8:18AM 3.1
139a Fishers Island 14.0 11:05AM 8:18AM 3.1
99 Niantic Bay 5.0 4:00PM 1:02PM 3.6
307a Duck Island Roads 6.0 2:40PM 8:26AM 2.9
74a Jordan Cove 16.0 10:40AM 2:01AM 3.4
74b Jordan Cove 14.0 10:40AM 2:01AM 3.4
251b Jordan Cove 11.0 11:29AM 2:01AM 3.4
9
Extent of Eelgrass
A total of 163 eelgrass beds accounting for nearly 1,600 acres were inventoried. A
summary of their locations by sub-basin is given in Table 3. Figure 5 shows the location
of eelgrass beds in the study area. More detailed maps showing the location, size, and
shape of these beds in each sub-basin are presented in Appendix A.
Most of the sites with eelgrass were estimated to have medium stem density (Table 3).
Only 17.6 acres of high density beds were inventoried. Please note that the density
estimates are subjective and not based on quantitative analysis of cover; medium to low
density beds from field observations were mapped as medium density beds.
Six sub-basins had over 100 acres of eelgrass beds. Quiambog Cove had the most
acreage with 357 acres. Only one other area had over 200 acres of eelgrass: Little
Narragansett Bay (286), while Fishers Island had almost 200 acres. The remaining sub-basins
with more than 100 acres of beds were Goshen Cove (157), Niantic Bay (139), and
Rocky Neck State Park (103).
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Table 3. Eelgrass beds in eastern Long Island Sound. Sites are in Connecticut, except
where noted otherwise.
Acres of Acres of Acres of
High Medium Low Total
Sub-basin Density Density Density Acres
(number) (number) (number) (number)
Little Narragansett Bay 0 285.8 (13) 0 285.8 (13)
Stonington Harbor 0 42.8 (8) 0 42.8 (8)
Quiambog Cove 1.0 (1) 356.2 (9) 0 357.2 (10)
Mystic Harbor 0 78.9 (12) 0 78.9 (12)
Palmer-West Cove 0 34.8 (6) 0 34.8 (6)
Mumford Cove 0 86.2 (9) 0 86.2 (9)
Paquonock River 0 30.1 (6) 0 30.1 (6)
New London Harbor 0.2 (1) 23.3 (5) 7.1 (1) 30.6 (7)
Goshen Cove 1.7 (3) 73.3 (3) 82.0 (2) 157.0 (8)
Jordan Cove 0 19.2 (6) 24.1 (1) 43.3 (7)
Niantic Bay 9.2 (2) 129.5 (12) 0 138.7 (14)
Rocky Neck State Park 0 102.8 (28) 0 102.8 (28)
Duck Island Roads 0 1.1 (2) 1.1 (2)
Fishers Island, NY 5.5 (8) 184.8 (19) 3.2 (4) 193.5 (31)
North Shore, NY 0 15.7* (2) 0 15.7* (2)
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Total 17.6 (15) 1,464.5 (140) 116.4 (8) 1,598.5 (163)
*Beds listed as medium although no record of density was reported by field inspector.
10
11
Historical Data
During this study, we gathered information from past eelgrass surveys and compiled information
in our digital database. A series of seven maps were prepared to show the results of these surveys
in more detail as compared with our data (see Appendix B). These products provide a composite
view of the results of various eelgrass surveys. No historic data were available for the North
Shore of Long Island.
12
Summary
Our survey located and mapped roughly 1,600 acres of eelgrass beds in eastern Long Island
Sound. Six sub-basins had over 100 acres of eelgrass beds: Quiambog Cove (357), Little
Narragansett Bay (286), Fishers Island (194), Goshen Cove (157), Niantic Bay (139), and Rocky
Neck State Park (103). Eelgrass beds were mostly present from Rocky Neck State Park east to
the Rhode Island border. Two small beds were found on the North Shore of Long Island, New
York. No eelgrass was found from the Old Lyme Shores sub-basin to Clinton Harbor, except for
two small beds (totaling 1.1 acres) associated with the Duck Island breakwater in the Duck
Island Roads sub-basin.
13
Acknowledgments
Funding for this project was provided by the Connecticut Department of Environmental
Protection (DEP) through a grant from the U.S. Environmental Protection Agency as part of the
Long Island Sound Study. Ron Rosza was project officer for DEP. Ralph Tiner was the
principal investigator for U.S. Fish and Wildlife Service (Service) and was responsible for
project design, management, data analysis, and report compilation.
Photointerpretation, digital database construction, and geographic information system (GIS)
processing was done by Herb Bergquist (Service). He compiled data for summation in this
report and prepared maps and figures included herein.
Our Southern New England Estuary Program (SNEP) was responsible for field review of
potential eelgrass beds, with Andrew MacLachlan and Tom Halavik taking lead roles in this
effort. Others assisting in the field included Mark Engler, Don Henne, and Julianna Wyman
(SNEP), Greg Mannesto (New England Field Office, Service), Lisa Holst (New York State
Department of Environmental Conservation), Chris Pickerell (Cornell Cooperative Extension,
Marine Program), Herb Bergquist, and Ralph Tiner.
14
References
Dobson, J.E., E.A. Bright, R.L. Ferguson, D.W. Field, L.L. Wood, K.D. Haddad, H. Iredale III,
J.R. Jensen, V.V. Klemas, R.J. Orth, and J. P. Thomas. 1995. NOAA Coastal Change Analysis
Program (C-CAP): Guidance for Regional Implementation. U.S. Department of Commerce,
National Oceanic and Atmospheric Administration, National Marine Fisheries Service,
Washington, DC. NOAA Technical Report NMFS 123.
(http://www.csc.noaa.gov/crs/lca/proto2.html#c4p1)
Appendices
Appendix A.
Maps showing distribution of eelgrass beds
located during this inventory
Clinton Harbor/Westbrook Harbor/Duck Island Roads Sub-basins
Connecticut River/Old Lyme Shores/Rocky Neck State Park/Willard Bay Sub-basins
Fishers Island
Goshen Cove/Jordan Cove/Niantic Bay Sub-basins
New London Harbor/Paquonock River/Mumford Cove Sub-basins
Palmer-West Cove/Mystic Harbor/Quiambog Cove Sub-basins
Stonington Harbor/Little Narragansett Bay Sub-basins
New York Long Island, Orient Point Area
Appendix B.
Maps showing historical data combined
with the results of this inventory
Clinton Harbor/Westbrook Harbor/Duck Island Roads Sub-basins
Connecticut River/Old Lyme Shores/Rocky Neck State Park/Willard Bay Sub-basins
Fishers Island
Goshen Cove/Jordan Cove/Niantic Bay Sub-basins
New London Harbor/Paquonock River/Mumford Cove Sub-basins
Palmer-West Cove/Mystic Harbor/Quiambog Cove Sub-basins
Stonington Harbor/Little Narragansett Bay Sub-basins