Ecological Monitoring
of a Constructed Intertidal Flat at
Jonesport, ME

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Contribution 126
November 1999

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US Army Corps
of Engineers.

New England District

form approved
OMB No. 0704-0188

REPORT DOCUMENTATION PAGE

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'|1. AGENCY USE ONLY (LEAVE BLANK) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
November, 1999 FINAL REPORT

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
ECOLOGICAL MONITORING OF A CONTRUCTED INTERTIDAL FLAT AT JONESPORT, ME

6. AUTHOR(S)
Gary L. Ray, Ph.D.

8. PERFORMIGORGANIZATION
REPORT NUMBER

|7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
US Engineer Research and Development Center—WES—Coastal Ecology Branch
3909 Halls Ferry Road

Vicksburg, MS 39180-6199

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
US Army Corps of Engineers-New England District
696Virginia Rd
Concord, MA 01742-2751

11. SUPPLEMENTARY NOTES
Available from DAMOS Program Manager, Regulatory Branch
USACE-NAE , 696 Virginia Rd, Concord, MA 01742-2751

10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
DAMOS Contribution No. 126

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution unlimited

13. ABSTRACT

Intertidal flats are ecologically and commercially important habitats to the New England region of the U.S. They
provide forage for commercially important fish species and both migratory and resident shorebirds. They also support
shellfish and bait-worm industries. As a demonstration of the potential for beneficial use of dredged material in construction
of these habitats, dredged materials from a harbor construction project were placed on a site on the western side of Sheep
Island, Jonesport, Maine. After nine years the physical integrity of the site has not been compromised. The site quickly
developed a substantial population of the commercially important soft-clam, Mya arenaria, as well as a diverse and
abundant infaunal community. A population of the bait-worm Nereis virens was initially established but commercial-sized
worms were absent during the last sample period. The absence seems most likely due to normal interannual fluctuations in
abundance. A second, older constructed flat, resulting from intertidal disposal of dredged material, Beals Island, has an
extensive bait worm population but few soft-clams. Differences in species’ abundances appear most likely to be due to
substrate differences. The infaunal community, the principal source of forage for fish and shorebirds, at both sites is
comparable in diversity, abundance, biomass, and species composition to other New England intertidal flat assemblages.

14. SUBJECT TERMS Intertidal flats, Sheep Island, Jonesport, Beals Island

15. NUMBER OF TEXT PAGES: 62

16. PRICE CODE

17. SECURITY CLASSIFICATION OF |18. SECURITY CLASSIFICATION |19. SECURITY CLASSIFICATION |20. LIMITATION OF
REPORT Unclassified OF THIS PAGE OF ABSTRACT ABSTRACT

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ECOLOGICAL MONITORING
OF A CONSTRUCED INTERTIDAL FLAT AT
JONESPORT, ME

CONTRIBUTION #126

November 1999

Submitted to :

Regulatory Branch
New England District
U.S. Army Corps of Engineers
696 Virginia Road
Concord, MA 01742-2751

Prepared by:
Gary L. Ray, Ph. D.

Submitted by:
U.S. Engineer Research and Development Center
Waterways Experiment Station
Coastal Ecology Branch
3909 Halls Ferry Road
Vicksburg, MS 39180-6199

(601) 634-2589

US Army Corps
of Engineers:

New England District

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TABLE OF CONTENTS

Page

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FETS IE © BSA MEE See aera ee RR GIES A AE LL aL CU rts Lal Ra Le ga Vv

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Pe ENGI OD UW) CTO Nise he seta cise aan tea acre ie eee Ah al ie 1

PE Die PMI DalO] DSRS odecnseanen tte ane Ronee Bae er Meena EME ete nis ARIE Annies Ma MAN epee EARLE 9) 7

2 DESC HONGO I SMIG Va Teag sa sa anae Oks acta ate aire acta Sel ioe esr ee ante v7

Dida WET OJCCURELISCOLY seseee ac sehe ae tied ott MASA Aiea: a ae ey eye MN ah My ee et 7

Ze Semin Dat an OlecHony 8 oe scce nly: w nce hasen a keg sae 2 RGA en AS tae Rane ea see 8

Dee ROAD ESE ROCESSIIO tater, marc che nae on erst on nae Asatte at icv ee ee 10

ZED MC OLAS ICA NE CHMIQUES =. .cte ck sue con once caeeer SO TM CERES Re RE eee 11

SOMONE SWIMS Bir neste cisecmsc cect anes wate cect race or Mean eer e eT ee ERNE tee an 13

3-1 Sediment Texture and) Organic Content Resultsi.--.--e eee 13

STAT OHECEDRISIANIC seman ween Mer mace te te see eae ae OnnnNe fey eet et OAR 13

SleDs SBealsuslana\ cat 3. s.ces ec come cnn aera ae oe tar rac eR gure ee 14

3-25) Sott-Clamvyand) Bait-wormrSunveyeResults eee e. tee ee eee ee 16

3:2 a sShee pi ESTA ie ietnccee ons sthass ses stectne st iaclelea An aH cee canteen dete se abe tad eR 16

SIZ Se Soft-Clams!(Miyatarenania) iso cas eeeee. 2280 ee eee ese 16

Beedle VEIN KO GS (INGCSS WIKIS) opocoodososs ssosabeconoocdosboncvecasoaeaeocasnese 20

S22 IBEalsulsland yw iwenre Few We Oe. ae era PN Cone Peg cea 22

See alee Sont-EClamsi(Myayarenania) pase eeeeee ee eee Coreen eee EEE 22

SPD 2 aa Clam—wormis (NETeiShViFeNS) ees eee eee eee eee 23

SYSS Hum UIUC LUNI: J ARe Rye aoa rare ental NP arinee orn Sun CCU Aa carn NE eee MPN ee cree ee ok WS)

SF fl My Shice py al Sarah yeess craps eye Eisen! De fslog em ies AM aan SNES oh es BPMN aces 25

353 lee Assemblage Strctunel eu. n- sa eeess ee ee ae eee Se ese eeeeee eee 25

323.51 #2 eM aXONOMIC, SIRUCHUITE a Sot sata ca tgens, Senay. RMR aay cece aise 30

323225 BealssSland yrs ves teaemiaeccccs ol ece eects a0) au eR ESR adhe eects 37

33. 2 ele Assemblage, Sth ClULe ha ss 5tenc cae eta Ae Get DOH ee oo B7

5-3-2 2 MAXOUOMUC, SMUCLUNE a: esos neee ee ery ee eee EE 41

AT Orr DD ISC@USSIONGE, con nescence ce nen oe nea ree oi See Un ane aN ear TA Ge re Re oO 49

Ope SCONCE USION GS oo ak ras es yt seta Me un ras Rae seca ee ee 56

Gy REBERENCES #2 en.cucccorensocecnen eave non tee Rime cee cea oe SBOE one Re a tee 57

INDEX

APPENDICES

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i cay rises ii i f al
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Figure 1-1.
Figure 1-2.
Figure 1-3.
Figure 1-4.
Figure 3-1.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 3-6.
Figure 3-7.
Figure 3-8.

Figure 3-9.

Figure 3-10.
Figure 3-11.
Figure 3-12.
Figure 3-13.

Figure 3-14.

LIST OF FIGURES

Page
Map ofiStudy Area. Sayre: SPRIOUn. SEITE, FUT PEC ML ak SE, 2
Aerial view of Sheep Island 4: Bao sea aE, IE: Penn. eee 4
Panoramic view of the Sheep Island Constructed Intertidal flat................ 5)
Aerial viewsof Bealsistand*).2 Wah.) ee ae, SOS, VR Eel ee 6
Sheep Island#SedimentsVexture sey 5.2.5 sea ay sae, knee 13
Sheepilsiand*Sediment’Oreanic Content. sesse-e cee sees eeeeeecee eee: 14
Beals IslandySedimentMexture Peeeeaes eee ase eerae meee nie saat nectar 15
Bealsiisland'Sediment’Organic Contentoeyseye. cece ees cee eee 15
Abundance of Mya arenaria from Sheep Island cores .......................- 17
Size Frequency Histograms for Mya arenaria: Sheep Island 1991 ........... 18
Size Frequency Histograms for Mya arenaria: Sheep Island 1992 ........... 18
Abundance of Nereis virens from Sheep Island cores ....................2+000+ 19
Size Frequency Histograms for Nereis virens: Sheep Island 1991 ........... 21
Size Frequency Histograms for Nereis virens: Sheep Island 1992 ........... ail
Size Frequency Histograms for Mya arenaria: Beals Island 1992 ............ 23
Abundance of Nereis virens from Beals Island cores ................-...20+00++ 24
Size Frequency Histograms for Nereis virens: Beals Island 1992 ............ 25
Infaunal Taxa Richness (Taxa/Core) at Sheep Island .......................008- 27

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Figure 3-15.
Figure 3-16.
Figure 3-17.
Figure 3-18.
Figure 3-19.
Figure 3-20.
Figure 3-21.
Figure 3-22.
Figure 3-23.

Figure 3-24.

Infaunal Abundance (Animals/m’) at Sheep Island.................0e:eeeeeeeees 28

Infaunal Biomass (Grams Wet-Weight/m’) at Sheep Island..................-. 28
Sheep Island Infaunal Biomass Structure .................0:.ececceseecenseeeeees 29
Nonmetric Multidimensional Scaling for Sheep Island 1990-1991 ........... 39
Nonmetric Multidimensional Scaling for Sheep Island 1991-1998 ........... 34
Infaunal Taxa Richness (Taxa/Core) at Beals Island.........................2+: 37
Infaunal Abundance (Animals/m7) at Beals Island ...................seseeeeeees 38
Infaunal Biomass (Grams Wet-Weight/m’) at Beals Island ..................-. 40
Beals Island Infaunal Biomass Structure :.......20..2:02:.202-20-000s00eseesneeen 41
Nonmetric Multidimensional Scaling for Beals Island 1991-1998............ 48

Table 2-1.

Table 2-2.

Table 2-3.

Table 2-4.

Table 3-1.

Table 3-2.

Table 3-3.

Table 3-4.

Table 3-5.

Table 3-6.

Table 3-7.

Table 3-8.

Table 3-9.

Table 3-10.

Table 3-11.

Table 3-12.

Table 3-13.

LIST OF TABLES
Sheep Island Pittand'Rake'Samples 20 y7yae Stites tac seein d tack ance
BealsilslandsPittand Rake! Sampleses.pieseeeee see aes ae et neat
Sheep Island Infaunal and Sediment Samples ........................eeeeeeeeeees
Beals Island Infaunal and Sediment Samples................2...2:cecceeseeeeeees
Sheep Island Soft-Clam (Mya arenaria) Survey Results........................
ANOVA Results for Sheep Island Mya arenaria Abundance (Cores)........
Sheep Island Clam-Worm (Nereis virens) Survey Results .....................

ANOVA Results for Sheep Island Nereis virens Abundance (Cores) ........

Beals Island Soft-Clam (Mya arenaria) Survey Results.........................

Beals Island Clam-Worm (Nereis virens) Survey Results......................

ANOVA Results for Beals Island Nereis virens Abundance (Cores).........

Sheep Island Infaunal Taxa Richness ANOVA Results.................2.-.20+5
Sheep Island Infaunal Total Abundance ANOVA Results .....................

Sheep Island Infaunal Total Biomass ANOVA Results.........................

Relative Abundance and Occurrence of Dominant Taxa at Sheep
islands Constructed yIntertidalyilatyseeee cesar pert eee ee eee cee eee eee eee eeece

Relative Abundance and Occurrence of Dominant Taxa at Sheep
IslandReference: Site. 40. i:1.5. 5 asccatnnc ass: ee saneunene seen sacmerraacisecmecaase

Similarity Percentage (SIMPER) Results for Sheep Island Constructed
lativs-uketerence Comparisons) by Veale --eereeeaeeeer eee eeee ne scee see eee

Table 3-14.

Table 3-15.

Table 3-16.

Table 3-17.

Table 3-18.

Table 3-19.

Table 4-1.

Table 4-2.

Table 4-3.

Beals Island Infaunal Taxa Richness ANOVA Results ......................00-
Beals Island Infaunal Total Abundance ANOVA Results .....................-
Beals Island Infaunal Total Biomass ANOVA Results........................+-

Relative Abundance and Occurrence of Dominant Taxa at Beals
Island Constructed :IntertidaluBlaty, Was. saeete eee. cc eee eee. oe ee eee

Relative Abundance and Occurrence of Dominant Taxa at Beals
Island‘Reféréence' Site. 2.1. 3.22 8 De eee

Similarity Percentage (SIMPER) Results for Beals Island Constructed
Flativs:)References@omparisons bys eater. 2asses.5- 4426 2-2 2os--eeeeeeeeeee

Diversity and Abundance of North Atlantic Intertidal Flat Infauna ..........
Species Composition of North Atlantic Intertidal Flat Infauna................

Comparison of Biomass and Biomass Composition Results with other
New England Intertidal Flats’ -72 3. acte eee oso ene cec cence cease eee eee ee ee eereee

Appendix Table 1. 1998 Worm Rake Collection Data

Appendix Table 2. Sheep Island Taxa List and Abundances (No./m’)

Appendix Table 3. _ Beals Island Taxa List and Abundances (No./m’)

Vi

EXECUTIVE SUMMARY

Intertidal flats are ecologically and commercially important habitats to the New
England region of the U.S. They provide forage for commercially important fish species
and both migratory and resident shorebirds. They also support shellfish and bait-worm
industries. As a demonstration of the potential for beneficial use of dredged material in
construction of these habitats, dredged materials from a harbor construction project were
placed on a site on the western side of Sheep Island, Jonesport, Maine. After nine years
the physical integrity of the site has not been compromised. The site quickly developed a
substantial population of the commercially important soft-clam, Mya arenaria, as well as a
diverse and abundant infaunal community. A population of the bait-worm Nereis virens
was initially established but commercial-sized worms were absent during the last sample
period. The absence seems most likely due to normal interannual fluctuations in
abundance. A second, older constructed flat, resulting from intertidal disposal of dredged
material, Beals Island, has an extensive bait worm population but few soft-clams.
Differences in species’ abundances appear most likely to be due to substrate differences.
The infaunal community, the principal source of forage for fish and shorebirds, at both
sites is comparable in diversity, abundance, biomass, and species composition to other
New England intertidal flat assemblages.

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1.0 INTRODUCTION

A major portion of the sediment dredged annually from our nation's harbors and
navigation channels has the potential for beneficial use. Habitat development, an important
example of such a use, has been employed in the construction, restoration and
enhancement of a variety of coastal habitats including salt marshes, oyster beds, and
waterbird nesting sites (e.g., Yozzo, Titre, and Sexton, 1996; Parnell, DuMond, and
McCrimmon, 1986). Since 1988, the US Army Engineer New England District (CENAE)
has been examining construction of intertidal flats as a viable alternative to dredged
material disposal (Fleming et al., 1991). Construction of intertidal flats as a beneficial use
of dredged materials has previously been suggested by Kirby (1995) as a mechanism to
replace lost habitat and protect fragile shorelines from erosion. Hosokawa (1997) has also
supported the concept as a method of restoring lost sandy intertidal habitat in Japan.
Monitoring of constructed sand flats in Japan has indicated rapid colonization of deposited
sediments and establishment of benthic communities similar in biomass to natural flats
(Hosokawa, 1997; Okada, Lee, and Nishijima, 1997).

Intertidal flats account for 15.6% of coastal wetlands along the North Atlantic coast
of the United States (Field et al., 1991). Providing high levels of primary productivity and
forage for commercial fisheries species, they are ecologically and commercially important
(Peterson and Peterson, 1979; Whitlach, 1982). Intertidal flat primary producers,
dominated by microalgae such as diatoms, provide a third of the total organic carbon
budget for southern New England coastal areas (Marshall, 1970) and in the South Atlantic
provide up to 50% of total estuarine primary productivity (Pinckney and Zingmark, 1993).
Unlike vascular plants, whose high proportion of structural materials requires lengthy
decomposition periods, microalgae represent a concentrated and immediately accessible
food source to higher trophic levels (Olivier et al., 1996). The principal consumer groups
are dense assemblages of benthic invertebrates comprised primarily of polychaetes,
amphipods, and molluscs (Larsen and Doggett, 1991). These assemblages serve directly
and indirectly as forage for demersal fish and migratory shorebirds. Winter Flounder
(Pleuronectes americanus), a commercially important fish species, feed heavily on the
intertidal flat infauna (Wells, Steele, and Tyler, 1973). Juvenile flounder and other fishes
such as Atlantic herring (Clupea harengus), Atlantic Tomcod (Microgadus tomcod),
Atlantic Cod (Gadus morhua), longhorn sculpin (Myoxocephalus octodecemspinosus),
shorthorn sculpin, (M. scorpius), little skate (Raja erinacea), oceanpout (Macrozoarces
americanus), and sea raven (Hemitripterus americanus) are commonly found on intertidal
flats (Tyler, 1971). In addition, intertidal flats support large populations of sand shrimp
(Crangon septemspinosus) which are forage for flounder, other bottom feeding fishes, and
migratory shorebirds (Schneider and Harrington, 1981). Many shorebirds including
dowitchers, sandpipers, sanderlings, and plovers use Bay of Fundy and Maine intertidal

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

flats as stopover sites prior to their fall migrations to overwintering grounds in South
America (Hicklin, 1987). Benthic invertebrates provide a major portion of the food
resources needed to make these nonstop flights (Schneider and Harrington, 1981;
Matthews, Boates, and Walde, 1992). The amphipod Corophium volutator in particular,
has been found to be an important food source (Peer, Linkletter, and Hicklin, 1986).
Intertidal infauna such as Nereis virens also provide forage for resident shorebirds such as
herring and black-backed gulls (Ambrose, 1986). Intertidal flats also provide habitat for
commercial soft-clam (Mya arenaria) and bait-worm (Nereis virens and Glycera
dibranchiata) fisheries. Commercial fisheries statistics available on-line through the Maine
Department of Marine Resources website’ indicate that between 1989 and 1997 an average
of 2 million Ibs. of soft-clams were landed annually with an estimated value of $7.6
million/year. Clam-worm, N. virens, landings averaged 381,000 lbs./year between 1989
and 1996 representing a value of just under one million dollars/year while blood-worm (G.
dibranchiata) landings averaging 452,000 lbs./year were valued at $2.3 million/year.
Together these resources represent nearly 12 million dollars in income each year.

To explore the potential for beneficial use of dredged material in constructing
muddy intertidal flat habitat, approximately 74,500 cubic meters (100,000 cubic yards) of
dredged material resulting from breakwater construction and channel dredging in Sawyers
Cove, Jonesport, Maine (Washington County), were deposited on Sheep Island (Figure 1-
1). Sediments were placed in a shallow, circular basin (365 m diameter) surrounded by
rocky ledges on the leeward side of the island (Figure 1-2; Figure 1-3). In addition,
bedrock ledge material resulting from breakwater construction was placed along the
periphery of the site to help contain the dredged materials. Placement was initiated in
January 1988, interrupted in March 1988 for an environmental dredging window, and
finally completed in January 1989 (Fleming et al., 1991). The project resulted in creation
of 1.2 hectares (3 acres) of intertidal flat habitat. During the course of the study a second
site adjacent to Beals Island was identified as a mud flat resulting from intertidal disposal
of dredged material disposal in the 1960’s (Figure 1-4). Previously, Fleming et al. (1991)
and Ray et al. (1994a and 1994b) have reported results from monitoring of sediments, soft-
clam and bait-worm populations, and infaunal communities at Sheep and Beals Islands
between 1990 and 1992. The present report incorporates these results with those from
additional sampling efforts conducted in 1993, 1994, and 1998.

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

2.0 METHODS
2.1 Description of Study Area

Jonesport, Maine is located 80 km (50 miles) southeast of the Canadian border. The
coastline is typified by broad embayments and numerous granite islands (Kelley, 1987).
Intertidal flats have formed on the leeward side of most islands (e.g., Beals, Great Wass,
and Head Harbor) and other sites protected from oceanic swells (e.g., Machias Bay). The
climate is northern temperate with a mean annual air temperature of 43°C and mean annual
precipitation of 107 cm (Fefer and Schettig, 1980). Jonesport and the surrounding area lies
midway between two estuarine drainage areas, Englishman and Narraguagus Bays, but not
within the estuarine mixing zones (0.5 - 25 ppt) of either (NOAA, 1985). It is unlikely that
waters surrounding the islands experience salinities lower than 25 ppt even during peak
river flows. However, local salinity dilution undoubtedly occurs during periods of high
runoff. The principal natural threat to intertidal flats is erosion by storms and ice scouring.
Hurricanes and severe storms are infrequent but can result in substantial erosion (Yeo and
Risk, 1979). Ice scouring, the chief source of erosion, occurs when ice blocks are pushed
across flats by strong onshore winds, by the movement of tides, or during the spring
breakup of shorefast ice (Dione, 1969; Gordon and Desplanque, 1983).

The primary study area, Sheep Island, is a 3.9 hectare granite island located 2.3 km
southeast of Jonesport (Figure 1-1). Topped with a small copse of trees, it has extensive
rocky intertidal habitat with a gravelly sand intertidal flat at its base (Figure 1-2; Figure 1-
3). Sheep Island is unpopulated and accessible only by boat. The second study area, Beals
Island, is a much larger island (approximately 300 hectares) located 2 km due south of
Jonesport (Figure 1-1). It is connected to the mainland by a bridge and to Great Wass
Island to the east by a small causeway. The eastern connecting point was obviously once a
tidal channel but has since been filled. The area between Beals and Great Wass Islands,
Alley Bay, is now a sand and mud flat (Figure 1-4). The perimeter of the bay is rimmed by
riprap on the west and south and by a small pocket marsh, granite outcrops and sand flats
on the east. A water treatment facility is present at the northeastern tip of the bay. Easily
accessible by car, Alley Bay is a popular spot for digging soft-shell clams and bait-worms.
Species of concern in the area include soft-clams, bait-worms, harbor seals, and shorebirds
(USFWS, 1980).

2.2 Project History
The primary study site is an intertidal mud flat constructed with dredged materials

on the west side of Sheep Island (Figure 1-2). The constructed flat and an adjacent area of
gravelly intertidal sands (reference area) have been sampled to characterize changes in

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

8

sediment and monitor development of soft-clam and bait-worm populations, and benthic
macro-invertebrate (infauna) communities. During the initial sampling trip (1990), local
residents informed project personnel of an earlier dredged material deposit placed during
the 1960’s at nearby Beals Island (Figure 1-4). The Beals Island disposal operation
occurred prior to the National Environmental Protection Act (NEPA) and apparently no
records were kept of the precise location of the disposal area. An area corresponding to
residents’ descriptions was examined and the presence of stiff clays similar to dredged
sediments (clay balls) below the sediment surface seemed to confirm the area as a disposal
site. In 1991, the Beals Island site was added to the study as an example of a much older
(approximately 30 years) constructed intertidal flat.

In June 1990 the New England District (CENAE) and Normadeau Associates
conducted a survey of soft-clam populations, infauna and sediments at Sheep Island. All
sampling in subsequent years occurred in August or September during the lowest tides
available. In 1991, CENAE personnel and members of the Waterways Experiment
Station’s Coastal Ecology Branch (CEB) repeated the sampling of Sheep Island, extended
the survey to include bait-worms, and sampled the constructed flat and an appropriate
reference area at Beals Island. This sampling scheme was repeated in 1992. Only the
Beals Island site was accessible in 1993 due to inclement weather. Infaunal and sediment
samples were taken but no bait-worm or soft-clam sampling occurred. Infauna and
sediments were sampled at both sites in 1994. In 1998 sediments, infauna, and bait-worm
and soft-clam populations were sampled at Sheep Island, while at Beals Island only infauna
and sediment samples were taken.

2.3 Data Collection

Bait-worm and soft-clam samples were taken using several different methods
(Tables 2-1 and 2-2). Sampling methods changed from year-to-year as progressively more
experience was gained and limitations of individual methods were recognized. In 1990 and
1991 thirty 0.04 m? pits were dug using a shovel and sediments were rinsed over a 0.63 cm
(0.25 in.) mesh screen. Soft-clams collected on the screen were identified, counted, and
specimen widths measured to the nearest mm in the field. When sampling was expanded to
include bait-worms in 1991, it was recognized that while this method provided quantitative
samples it would not capture the full range of different sized worms due to the small
sampling area. In particular, it would undersample large commercial-size animals. Clam-
worms can reach 90 cm in length (Pettibone, 1963) and the maximum dimension of the pits
was only 20 cm. Commercial worm rakes were employed in order to collect these larger
specimens. Rakers collected all specimens encountered during a series of 5-minute
sampling periods, counted the specimens and measured their total lengths to the nearest
mm. Although this procedure resulted in collection of large animals it was relatively

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

No)

nonquantitative. To address this issue, in 1992, nine 1 m* areas were thoroughly hand-
raked at each site. No pit (shovel) samples were taken at this time. This method produced
reliable results but a considerable amount of time was required to adequately rake each
sample plot and a question arose as to the efficacy of the method to quantify medium and
small sized animals. Accordingly, in 1998, the area raked was reduced to 0.5 m? (a
maximum of eight areas were raked) and pit samples were taken from the corner of each of
raked plot and sieved over a 5 mm screen to insure collection of medium-sized animals.
Sampling was limited to the Sheep Island sites.

Table 2-1. Sheep Island Pit and Rake Samples*

Samples vee pslaunlta al eae
| 1990 | 30 | 0.04m? | m ere m
PESO ie ee eee
P| so oat Ft
i 998) RNS el ONT Shinn ES) a OPA Shoren | aan mae

Table 2-2. Beals Island Pit and Rake Samples*

baa eay Palen
Samples Area Sunnie Area Area:

Lisa] 0.04 m? ee
Romane ane ee eS on oe

* Represents type and number of samples taken at each sample site.
? Number of samples not recorded

Infauna were collected by forcing a 7.5 cm diameter coring tube into the sediment
to a depth of 10 cm. During the early part of the study a total of 30 cores were taken at
each site (Tables 2-3 and 2-4), however, the sample size was later reduced to 15. Equal
numbers of cores were taken at each of three different distances from the shoreline and
each core was taken at least 2 m away from any previous sample. Samples were washed
over a 0.5 mm mesh screen in the field, fixed in 4% formalin, and transported to the
laboratory. A total of 9 sediment grain size samples were collected at each site with a 5 cm
diameter coring tube to a sediment depth of 10 cm. Samples were placed in a plastic bag
and transported to the laboratory for analysis.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Table 2-3. Sheep Island Infaunal and Sediment Samples

Constructed Flat

HL TooaleepuMlar ee Spee
Sou e OrIRRE ESTP aU
ea a Re KO

Table 2-4. Beals Island Infaunal and Sediment Samples

a laa

EEO ORK TS es OR
PISS SOs ve SOR On
199% a Eail 151 Zils. oS) We Mee Ts eo a
21998 leds 1ST lines ard 15 Do a

2.4 Sample Processing

Sediment grain size analysis was performed using a combination of wet-sieving and
flotation methods (Folk, 1968; Galehouse, 1971). Sediment organic content was measured
by loss upon ignition (550° C). No organic content analysis was performed on the 1990
samples and none was possible in 1998 due to unavoidable delays in sample shipment. In
the laboratory infaunal samples were rinsed over a 0.5 mm mesh sieve to remove formalin,
transferred to 70% ethanol and stained with rose bengal solution to facilitate sorting of
specimens. After staining, the samples were rinsed to remove excess stain, examined under
3X magnification, specimens separated from the remaining sediment and detritus and
stored in 70% ethanol. Specimens were then identified to the lowest practical taxonomic
level and enumerated. Wet-weight biomass was determined for major taxonomic groups
(e.g., Polychaeta, Crustacea).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

11

Because of a change in contractors processing the samples, differences arose in the
level of taxonomic identifications between the 1990 and post-1990 sample sets particularly
in the identification of oligochaete worms (Annelida). The initial contractor was apparently
unfamiliar with the group so all specimens were recorded simply as Oligochaeta.
Examination of later samples indicated the presence of a number of species, including
Tubificoides benedini and Tectadrilus gabriellae, two of the most numerically abundant
taxa. Attempts to locate the 1990 specimen collection were unsuccessful making it
impossible to reexamine the specimens or measure biomass.

2.5 Statistical Analyses

Soft-clam and bait-worm abundances are reported on a per square-meter basis by
sampling method: core or pit and rake. Pit and rake data could not be analyzed statistically
due to differences in sample area and sampling method, however, abundances from core
samples could be evaluated using Analysis of Variance (ANOVA). Abundance data for
bait-worms and soft-clams were tested for normality and heterogeneity of variance prior to
ANOVA and transformed where necessary to conform to assumptions of the test. Sheep
Island Nereis virens and Mya arenaria data required fourth-root (x’*) transformations as
did clam-worm densities from Beals Island. Too few specimens were collected to permit
analysis of M. arenaria at Beals Island and Glycera dibranchiata at either site. Data were
tested using a two-way ANOVA with sampling date and site (constructed flat or reference)
as the main effects. When either site or year effects were significant (p<0.05) Tukey’s test
was empoyed to determine differences between means. Where the Site by Year interactions
were significant, the main effects could not be interpreted (Zar, 1996). Linear contrasts
were performed in order to determine where significant differences occurred between sites
among the sampling dates using the Bonferroni adjustment (p = 0.05/no. comparisons) to
correct for multiple comparisons (Underwood, 1997). Since there are five relevant site by
date combinations (e.g., Sheep Island Constructed Flat 1991 vs. Reference 1991), a p
value of 0.01 was required for a comparison to be considered statistically significant.
Where only four comparisons were possible (e.g., biomass data) a p value of 0.0125 was
required.

Soft-clam and bait-worm population structures were examined by construction of
size frequency histograms. Measurements for individual species were pooled by site and
date and the relative abundance of animals in each of at least 10 size classes were plotted.
A minimum sample size of 30 animals was required in order to reduce the influence of a
few very large or very small animals. In general, this restricted the size frequency analyses
to the 1991-1992 sample collections and excluded consideration of Glycera populations.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Summary sediment grain size data (e.g., % silts, % gravel) are presented as stacked
bar graphs. Infaunal assemblage parameters; taxa richness (taxa/sample), total numerical
abundance/m/? and total wet-weight biomass/m/’ were tested using ANOVA. Logarithmic
transformations were required for abundance and biomass. Where significant differences
were detected between main effects (Site or Year) or by linear contrasts, mean values +
one standard error have been plotted.

Infaunal taxonomic structure was examined using the nonparametric ordination
technique, Nonmetric Dimensional Scaling (NMDS) and Similarity Percentage (SIMPER),
a procedure that estimates the relative contribution of each taxon to overall similarity. The
total species list was reduced by considering only those taxa that comprised 1% or more of
total abundance or were present in 50% or more of the cores. In order to conform to
computational limits of the statistical software, the number of samples was reduced by
randomly selecting only 10 cores from each sample date and site for inclusion in the
analyses. For NMDS, abundance values were logarithmically transformed (log x+1) and
Bray-Curtis (BC) similarity values calculated for all possible combinations of samples.
Stress, a goodness-of-fit measure, was calculated for all NMDS comparisons. Stress values
less than 0.2 are considered to be adequate for interpretation of results (Clarke and
Warwick, 1994). For SIMPER analyses, abundances were fourth-root transformed as
recommended by Clarke and Warwick (1994). SIMPER calculates average sample
dissimilarity using the Bray-Curtis (BC) dissimilarity index (dissimilarity = 1- BC value).

Because of the oligochaete identification problem with Sheep Island 1990 data, it
was impossible to directly compare all years simultaneously. Instead, two separate analyses
were performed. First, 1990 and 1991 data were compared using the 1990 taxonomic
classifications (all oligochaete taxa pooled) and second, 1991 and all later samples were
compared using the full range of oligochaete identifications. Differences between 1990 and
post-1991 data are inferred from their relationship to the 1991 results.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

13

3.0 RESULTS
3.1 Sediment Texture and Sediment Organic Content Results
3.1.1 Sheep Island

As might be expected, sediment texture was finer at the Sheep Island constructed
intertidal flat than the reference area. The constructed flat was composed primarily of silts
and clays with relatively little (<25%) sand while the reference area was mostly sand and
gravel with less than 30% silts and clays (Figure 3-1). Sediment texture appeared to
coarsen at both sites in 1994 most likely representing methodological error. Sediment
texture at both sites in 1998 was similar to previous years. Sediment organic content was
higher at the Sheep Island constructed flat than the reference area in both 1992 and 1994
(Figure 3-2), although it decreased by 1-2% at both sites between years. As previously
noted no sediment organic content was measured in 1990 and logistical problems prevented
analysis of the 1998 samples.

Figure 3-1. Sheep Island Sediment Texture

100
% Silt/Clay

= = a % Sand

=|
ss | %Gravel
)
Qu.
5 50
1S)
ic
3
©
Ax 25
0
1990 1992 1994 1998 1990 1992 1994 1998
Constructed Flat (DM) Reference (REF)

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

14

Figure 3-2. Sheep Island Sediment Organic Content

Organic Content (%)

1992 1994 1992 1994
Constructed Flat (DM) Reference (REF)

3.1.2 Beals Island

Beals Island constructed intertidal flat sediments were also finer grained than those
of the respective reference site. In this case however, the difference was less pronounced
than at Sheep Island. Beals Island constructed flat sediments contained approximately 75%
silts and clays, while reference area sediments had 30-50% fines (Figure 3-3). The same
apparent coarsening of sediments found in 1994 Sheep Island samples was present in the
Beals Island sediments. Likewise, by 1998 sediment texture was similar to previous years.
Sediment organic content was also higher at the constructed flat than the reference site and
also declined between 1992 and 1994 (Figure 3-4).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Figure 3-3. Beals Island Sediment Texture

100

EA % Silt/Clay
i % Sand

75
s Es %Gravel
3
Qa
—& 50
1S)
r=]
3°
o
ay)
0
1992 1993 1994 1998 1992 1993 1994 1998
Constructed Flat (DM) Reference (REF)
Figure 3-4. Beals Island Sediment Organic Content
6

oN

N

Organic Content (%)
WwW

1992 1993 1994 1992 1993 1994
Constructed Flat (DM) Reference (REF)

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

16

3.2 Soft-clam and Bait-worm Survey Results

3.2.1 Sheep Island

3.2.1.1 Soft-Clams (Mya arenaria)

Initial rake and pit sample soft-clam abundances (animals/m’) were approximately
the same at both sampling sites, however, after 1991 densities were 2-3 times higher at the
constructed flat than the reference site (Table 3-1). Abundances from core samples, a
measure primarily of small-sized animals, indicated no differences between sites (p > 0.05)
for either species (Table 3-2). The only significant differences (p< 0.05) detected were
between sampling dates; Mya arenaria abundances were highest in 1994 (Figure 3-5).

Table 3-1. Sheep Island Soft-Clam (Mya arenaria) Survey Results*

Year
Puen 0 soos | eae
Ce ee aE Om OR |

Table 3-2. ANOVA Results for Sheep Island Mya arenaria Abundance (Cores)

Effect Test

Source DF Sum Sq. F Ratio
Eigse |) ST NN ovoiios ©) Wolosz50 bo ion
ear ea este eo 76 an KOoane mm
| Peron || (200) 0402413.) foo12 i aE

* Abundances in No. animals/m’; n = total numbers collected

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Figure 3-5. Abundance of Mya arenaria from Sheep Island Infaunal Cores*

250

Me ou
200 [a REF

150

Abundnace (No./m2)

1990 1991 1992 1994 1998
*DM = Constructed Intertidal Flat REF = Reference Site

Size frequency analysis of soft-clam populations was possible for both Sheep Island
sites, but only in 1991 and 1992. In 1991 the Mya population at the constructed intertidal
flat was smaller in size than that of the reference area; specimens in the 16-20 mm size
range constituted the bulk of the population (Figure 3-6). The reference area population
was bimodal with peaks at the 10-15 mm and 46-50 mm size ranges. In 1992 the modal
size of individuals from the constructed flat population had increased with the highest
proportion of individuals being 21-25 mm in length (Figure 3-7). Specimens from the
reference area population were smaller than previous samples with most specimens being
in the 31-35 mm size range. Although too few animals were collected in 1998 to perform
size frequency analysis, over half of those found were greater than 50 mm in length
(Appendix 1).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

18

Figure 3-6. Size Frequency Histograms for Mya arenaria: Sheep Island 1991*

50
40
S
e)
=
= 30
a.
iS)
Au
zs)
= 20
5)
(>)
pa
o
aw
10
0
Nunononaononononso w
STEN LESTE hake eon an ast@tnan
SO et OH OF Ot Ot OBO =
Saenanararamarrrnnwo or &

Length (mm)

85+

Figure 3-7. Size Frequency Histograms for Mya arenaria: Sheep Island 1992*

50

40

30

20

10 | i
0
BnNonownonccun oNneEeN IO wH
Bhat ai Svein nome ionlnete hte vp oi oitiann clk pete
S&S Xs) Gl Ye) oct Ko te Xe = Of OO
—! =) GQ) Al Gy 6d Sr Re oOo Om CO

*DM = Constructed Intertidal Flat REF = Reference Site

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

85+

From these data and the abundance results it appears that a substantial set
(recruitment) of soft-clams occurred soon after construction of the flat. Analysis of the
core abundances, a measure of small-sized animals, suggests that recruitment was and
continues to be equally successful at both sites. The abundance of larger-size animals,
collected by rake and pit sampling, indicates that large animals were evenly distributed
among the sites at first, but became substantially more abundant on the constructed flat
than the reference area (Table 3-1). The trend for increasing length of animals from the
constructed flat (Figures 3-7 and 3-8; Appendix Table 1) indicates that individuals rapidly
grew to commercial length (“50 mm). The numerous raking pits evident on the flat during
the 1998 field sampling (personal observation) is perhaps the clearest, if anecdotal,
evidence for establishment of a commercially viable population.

3.2.1.2 Clam-worms (Nereis virens)

Survey results for Sheep Island clam-worm populations are similar to those for soft-
clams (Table 3-3; Table 3-4). Abundances from rake and pit samples reflected considerable
annual variation with twice as many animals present at the reference area than the
constructed flat in 1991, the opposite result in 1992, and no animals found at either site in
1998 (Table 3-3). Clam-worms are large-bodied, mobile animals which periodically leave
their burrows to swim and breed in the water column (Pettibone, 1963). It is unclear how
much of the variation in rake/pit abundances was due to reproductive behaviors, natural
interannual variations in abundance, site-specific differences, or other factors. Data for
small-sized animals, i.e. the core data, indicate no difference (p > 0.05) in abundance
between sites or between sites over time (Table 3-4). Differences among years were
restricted to the highest and lowest values with 1990 abundances being the least and 1998
being the highest (Figure 3-8). Size frequency analysis, limited to the 1991 and 1992 data,
indicates that while the 1991 constructed flat and reference area populations had similar
structures (Figure 3-9), in 1992 constructed flat populations were dominated by much
smaller animals than those found at the reference area (Figure 3-10).

Table 3-3. Sheep Island Clam-worm (Nereis virens) Survey Results*

Year DM n REF n

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

20

3.2.1.2 Clam-worms (Nereis virens)

Survey results for Sheep Island clam-worm populations are similar to those for soft-
clams (Table 3-3; Table 3-4). Abundances from rake and pit samples reflected considerable
annual variation with twice as many animals present at the reference area than the
constructed flat in 1991, the opposite result in 1992, and no animals found at either site in
1998 (Table 3-3). Clam-worms are large-bodied, mobile animals which periodically leave
their burrows to swim and breed in the water column (Pettibone, 1963). It is unclear how
much of the variation in rake/pit abundances was due to reproductive behaviors, natural
interannual variations in abundance, site-specific differences, or other factors. Data for
small-sized animals, i.e. the core data, indicate no difference (p >0.05) in abundance
between sites or between sites over time (Table 3-4). Differences among years were
restricted to the highest and lowest values with 1990 abundances being the least and 1998
being the highest (Figure 3-8). Size frequency analysis, limited to the 1991 and 1992 data,
indicates that while the 1991 constructed flat and reference area populations had similar
structures (Figure 3-9), in 1992 constructed flat populations were dominated by much
smaller animals than those found at the reference area (Figure 3-10).

Table 3-3. Sheep Island Clam-worm (Nereis virens) Survey Results*

Year DM n REF n

* Abundances in No. animals/m?; n = total numbers collected

Table 3-4. ANOVA Results for Sheep Island Nereis virens Abundance (Cores)

Effect Test

Source DF Sum Sq. F Ratio D

Lnsaee TAO Gas osm IE |

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

21

virens: Sheep Island 1991*

Nereis

Figure 3-9. Size Frequency Histograms for

25

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Length (mm)

Figure 3-10. Size Frequency Histograms for

virens: Sheep Island 1992*

Nereis

DM
REF

a
ii

Length (mm)
REF

*DM = Constructed Intertidal Flat

25
20
5

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Reference Site

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

22

In contrast to the soft-clam data, clam-worm abundance and size frequency data suggest
that a large recruitment of clam-worms did not occur until 1992. As with the soft-clam,
recruitment was not site-specific and varied primarily among years. The high abundances
encountered in 1998 core samples suggest that a second “good” year for recruitment may
have occurred at this time.

3.2.2 Beals Island

3.2.2.1 Soft-Clams (Mya arenaria)

Soft-clams were much less abundant at Beals Island than Sheep Island throughout
the study. Practically no large-sized animals were collected in rake and pit samples in
either 1991 or 1992 (Table 3-5) and too few were collected in the core samples to analyze
densities. It was only in 1992 that sufficient specimens were collected to construct a size
frequency histogram and then only for the constructed intertidal flat (Figure 3-11). The
resulting figure indicates that the population was dominated by animals 36-45 mm in
length, a distribution similar to that of Sheep Island reference area populations for the same
time period (Figure 3-8).

Table 3-5. Beals Island Soft-Clam (Mya arenaria) Survey Results*
Year DM

n REF n
i eee as aaa a 2 |
Can a ae ee ee Oe a |

*Abundances in No. animals/m?; n = total numbers collected

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Figure 3-11. Size Frequency Histograms for Mya arenaria: Beals Island 1992*

25

NO
(=)

Percent of Population
—
Nn

10

5

0
NAuNnoNnoONOHNONON ON ON Tt
Bl SI LS Ee tat eal boast aoduTGs ME GlORS ans caer unten
CoO nm Omer Or Or Om O mt OO mm
[saa nNnarNmnranawtrrnnNn oO ORF

Length (mm)

3.2.2.2 Clam-worms (Nereis virens)

Clam-worms were far more abundant in rake and pit samples at the Beals Island
constructed flat than the reference area in both 1991 and 1992 (Table 3-6). The same is
true for three of the four years where linear contrasts detected significant differences
(p <0.01) between the constructed flat and reference area (Table 3-7; Figure 3-12).
Differences were detected between sites for all years except 1990 and reference values
were higher than constructed flat abundances only in 1993. Size frequency analysis was
possible only for the 1992 constructed flat samples; the population was bimodal with peaks
in the 110-199 and 200-209 mm categories (Figure 3-13).

Table 3-6. Beals Island Clam-worm (Nereis virens) Survey Results*

Year DM REF n

* Abundances in No. animals/m’; n = total numbers collected

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

24

Table 3-7. ANOVA Results for Beals Island Nereis virens Abundance (Cores)**
Effect Test

Source DF Sum Sq. F Ratio

[site [115.5506] 54.2444 | <0.0001
[Tie aay ne om
etier 4 ee eee
sero FON 051-3155 I 07 eo

Linear Contrasts**

199s wel S97 e993 OOF O9s

Estimate 0.3353 1.0286 -0.5670 1.0505 1.1280
t Ratio 1.9548 7.4407 -2.9000 5.3732 5.7695
Prob > |t| 0.0522 <0.0001 0.0042 < 0.0001 <0.0001

**Negative estimates indicate Dredged Material site abundances less than Reference site
values; positive estimates indicate abundances are higher than reference. Figures in bold
are significantly different at p<0.01.

Figure 3-12. Abundance of Nereis virens from Beals Island Cores*

2K KK A 6 2 OR EK KK 2K eK KK 2K OK AE EK

1991 1992 1993 1994 1998

* DM = Constructed Intertidal Flat REF = Reference Site
Values with ****** indicate linear contrasts are significantly different at p <0.01

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

25

Figure 3-13. Size Frequency Histograms for Nereis virens: Beals Island 1992*

:

14
—
L
& 12
B.
© 10
jaw
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Sate)
S|
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I I ee I oe ce |
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*DM = Constructed Intertidal Flat REF = Reference Site

3.3 Infauna
3.3.1 Sheep Island
3.3.1.1 Assemblage Structure

The structure of Sheep Island infaunal assemblages was compared by examining
taxa richness (a measure of diversity), total numerical abundance, total wet-weight
biomass, and biomass structure (proportional composition by major taxonomic groups).
Taxa richness differed significantly (p <0.05) among sites over time (site by year
interaction factor) thus requiring linear contrasts to determine which sites were different
and when (Table 3-8). Significant linear contrasts (p<0.01) were detected in 1990 and
again in 1992. In 1990 taxa richness was higher at the constructed intertidal flat than the
reference area by more than 3 taxa/core, whereas in 1992 reference area taxa richness was

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

26

higher than constructed flat values by 1 taxon/core (Figure 3-14). A significant interaction
factor was also encountered in the ANOVA for total numerical abundance (Table 3-9).
Linear contrasts of site means over time resulted in only one significant comparison
(p<0.01), the constructed flat versus reference area comparison for 1990. At this time
abundance was far greater at the constructed flat than the reference area (Figure 3-15).
Analysis of the total biomass data resulted in only the time factor (year) being significant
(p<0.05) (Table 3-10). Tukey tests of the annual means indicated that only the lowest
(1991) and highest (1998) biomass values were significantly different (p <0.05) (Figure 3-
16).

Table 3-8. Sheep Island Infaunal Taxa Richness ANOVA Results

Source DF Sum Sq. F Ratio

J
Site*Year
Leer wiLatt Misses [bose |

Linear Contrasts Results
1990 1991 1992 1994 1998

Estimate 5.0667 -1.8 -2.067 0.9333 2.4
t Ratio 4.5602 -2.291 -2.631 0.84 2.1601
Prob > |t| <0.0001 0.023 0.0092 0.4019 0.032

Table 3-9. Sheep Island Infaunal Total Abundance ANOVA Results

Source DF Sum Sq. F Ratio D
Pi | AO ee? Oo eae |

Linear Contrasts

1990 WE ey 1994 1998
Estimate 1.0382 -3e-4 0.0111 0.1109 0.3231
Std Error 0.1381 0.0976 0.0976 0.1381 0.1381
Prob > |t| <0.0001 0.9972 0.9097 0.4229 0.0203

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Dal

Table 3-10. Sheep Island Infaunal Total Biomass ANOVA Results

Source DF Sum Sa. F Ratio D

ne) eee a

Figure 3-14. Infaunal Taxa Richness (Taxa/Core) at Sheep Island*

14

ae | DM
12

a

10

Taxa/Core

1990 1991 1992 1994 1998
Year
*DM = Constructed Intertidal Flat REF = Reference Site
Values with ****** indicate linear contrasts are significantly different at p <0.01

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

28

Figure 3-15. Infaunal Abundance (Animals/m’) at Sheep Island*

120000
fel
100000
ner
80000
60000
40000
20000
0)

1990 1991 1992 1994 1998
Year

Animals/m2

Figure 3-16. Infaunal Biomass (Grams Wet-Weight/m’) at Sheep Island*
600

Nn
S
(=)

aN
(=)
(=)

Grams (Wet-Weight)/m2
N (oS)
S S
S S

S
(=)

1991 1992 1994 998

Year
*DM = Constructed Intertidal Flat REF = Reference Site
Values with ****** indicate linear contrasts are significantly different at p <0.01

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

29

The proportion of biomass contributed by major taxonomic groups (€.g.,
oligochaetes, polychaetes, etc.) differed both among sites and over time (Figure 3-17). In
1991 and 1992, molluscs provided approximately 50% of total biomass at the constructed
intertidal flat while polychaetes and crustaceans, respectively, made lesser contributions.
By 1994 molluscs accounted for 90% of all biomass at the constructed flat, however, this
value fell to 29% in 1998 when crustacean biomass increased from 15% to 40% of total
biomass. At the reference area, polychaetes were the overwhelming dominant in 1991
(68%), but were replaced by molluscs (53-93%) in subsequent samples. As at the
constructed flat, the highest proportion of mollusc biomass was found in 1994.

Figure 3-17. Sheep Island Infaunal Biomass Structure.

ee)

N

ESSSSSSSSsss
ERA AAA dN

y
g
U;
l
s

Petcent of Total Biomass
RSS Qaw

1991 1992 1994 1998 1991 1992 1994 1998
Constructed Flat (DM) Reference (REF)

Together, the assemblage structure parameters indicate that a diverse and abundant
infaunal assemblage was quickly established at the constructed intertidal flat. The absence
of site or site by year differences in biomass values also suggests that the assemblage
developed rapidly, achieving and maintaining levels comparable to the reference area. The
overall dominance of biomass by molluscs and the tendency for periods of particularly high
dominance to be identical at both sites (e.g., 1994) also indicates a high degree of
similarity between sites.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

30

3.3.1.2 Taxonomic Composition

A total of 90 taxa was collected at the Sheep Island sites between 1990 and 1998:
64 at the constructed intertidal flat and 81 at the reference site (Appendix Table 2).
Species composition was similar with 49 of the 90 taxa being present at both sites. A
total of twenty five taxa were classified as dominants, i.e., they constituted 1% or
more of total numerical abundance or were present in 50% or more of the samples
(Tables 3-11; 3-12). None of the dominants were found exclusively at either site.

The most abundant organism was the amphipod Corophium volutator. Reaching a
maximum density of 28,000 animals/m” in 1992, it was generally most abundant and
comprised the greatest proportion of the constructed flat assemblage (Appendix Table 2;
Table 3-11; Table 3-12). Next in importance were the oligochaetes Tectidrilus gabriella
and Tubificoides benedini. Tectidrilus was the more abundant of the two but its relative
importance varied among years: in 1991 and 1992 it was more than twice as numerous as
Tubificoides benedini at the constructed flat, but precisely the opposite was true in 1998.
Tectidrilus populations at the reference site were at least twice as dense as Tubificoides
populations in 1991, 1994, and 1998. The polychaete Capitella sp., the fourth most
abundant taxon, was generally more numerous at the reference area than at the constructed
flat and was one of the most commonly occurring taxa at both sites. Densities of the fifth
most abundant taxon, the amphipod Gammarus oceanicus, varied widely between sites and
over time. Highest densities of this species occurred at the constructed flat in 1998 when
abundances were over 19,000/m? (Appendix Table 2). Of the ten most abundant taxa the
remaining five were polychaetes: Exogene hebes, Streblospio benedicti, Fabricia sabella,

Pygospio elegans, and Polydora ligni.

Taxonomic composition of the sites was also compared using Nonmetric
Multidimensional Scaling (NMDS). As previously noted, differences in the level of
taxonomic detail between data from 1990 and the remaining sample collections required
two separate sets of comparisons: one between 1990 and 1991 data and a second
comparing 1991-1998 collections. NMDS of the 1990-1991 data separated both sites by
year but not by great degrees indicating small but persistent differences in species
composition (Figure 3-18). Similar results were obtained from NMDS of the 1991-1998
data indicating small but persistent differences among sites (Figure 3-19).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

31

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Figure 3-19. Nonmetric Multidimensional Scaling for Sheep Island 1991-1998

1991 1992 1994 1998

Dredged Material @) 4)
Reference @ Q ()

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

33

34

Figure 3-18. Nonmetric Multidimensional Scaling for Sheep Island 1990-1991

Ge Stress = 0.14

et

1990 199]

Dredged Material ©
Reference ©

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

35

SIMPER results compliment the comparisons of taxonomic composition and NMDS
results. In 1990 the constructed intertidal flat and reference sites were distinguished
primarily by higher densities of oligochaetes, the polychaetes Fabricia sabella, Pygospio
elegans, and the amphipod Gammarus oceanicus at the reference site, and Polydora
quadrilobata at the constructed flat (Table 3-13). After 1990, oligochaetes, specifically
Tectadrilus gabriella, contributed greatly to overall site dissimilarity and was always more
abundant at the reference site. Tubificoides benedini, another oligochaete, was also
generally more abundant at the reference site and was one of the five taxa contributing
strongly to dissimilarity in 1992 and 1994. The amphipod Corophium volutator, another
taxon making a large contribution to dissimilarity, was always most abundant at the
dredged material site. The polychaete Polydora quadrilobata was most abundant at the
constructed flat in 1990 and again in 1998. The remaining taxa among the top five taxa
contributing to dissimilarity in any given year were inconsistent in their distributions, 1.e.,
they would be most abundant at the constructed flat one year and at the reference area in
another. For instance, the polychaete Exogene hebes was most abundant at the constructed
flat in 1991, but in preceding and subsequent years it was most abundant at the reference
site.

In summary, taxonomic composition, NMDS, and SIMPER results indicate that
taxonomic structure of the Sheep Island constructed flat assemblage was slightly but
persistently different from that of the reference area. Differences arose from the relative
abundance of a few dominant taxa, the most important of which were the oligochaetes
Tectadrilus gabriella and Tubificoides benedini at the reference site and the amphipod
Corophium volutator at the constructed flat. Relative abundances of the remaining
dominant taxa were inconsistent or contributed little to taxonomic similarity.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

36

Table 3-13. Similarity Percentage (SIMPER) Results for Sheep Island Constructed Flat vs
Reference Comparisons by Year*

Pam ——farpcert mt
Ten vais —} a a

Phoxooehaishobo_| 3.78 | 799° | 28 | —= | —|
Fabrica abel [1S] — | 636 | O87 | 458)
Pygooo deems 927] 586 [051 | —= | —|
(Ciymenela torquata [3.27 | 668 | — | —— |
(Corophium bonelli [| 542 [—— | == |
Se ee
Tbifecdes boned | —= | 419 [1608] 10.0%] 452
iow menss | = 268 | 395 | |
IMyaarenaria | | 2.86 | 2.09 | 3.67 | 2.98 |
Polydor qudnobata [950 [2.83 | 2.01 | 1.34 [59°]
Ganmans anime | 1.03] <= | =|

Scottolana canadensis |---| 2.47 | 0.62 | 0.69 | 192 |
ee

Sicbospio bens | —= | —= | SF] 638 TARY
Talassomya sp. | = | — | 237 | 1.39 | 2.68 |
Mytilus eaulis | —= | —= | 0.78 | 2.27 | 2.21 |
Eitorina Iitoreay | Sr ae
aera marina =| == | = | 2.00 | 0.74 [2.69 |
Enchytraeidae =| = | | 1.16 | 1.60 | 4.48 |
Eiconelonga | Pesala | =| 207 sit]

*Values in bold are the five taxa contributing the most to dissimilarity for a comparison. Superscripts indicate where
abundances were highest (D= Constructed Flat; R = Reference); * indicates oligochaetes treated as single taxon for
test.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

37
3.3.2 Beals Island

3.3.2.1 Assemblage Structure

ANOVA of Beals Island infaunal taxa richness data indicated that sites differed
significantly (p<0.05) among years (Table 3-14). Linear contrasts of site by year means
showed that constructed flat values differed from reference values (p<0.01) only in 1992
(Table 3-14) when taxa/core were highest at the constructed flat (Figure 3-20). Total
numerical abundance also differed among sites over time, however, abundances were far
greater at the reference area than the constructed flat (Figure 3-21) in all years except 1991
(Table 3-15). Total biomass was higher at the reference area than the constructed flat in all

years except 1994 (Table 3-16; Figure 3-22).

Figure 3-20. Infaunal Taxa Richness (Taxa/Core) at Beals Island*

25
Bs
20 [a9] REF

i
N

Taxa/Core
=

1991 1992 1993 1994 1998
Year

*DM = Constructed Intertidal Flat REF = Reference Site
**Values with ****** indicate linear contrasts are significantly different at p <0.01

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

38

Figure 3-21. Infanual Abundance (Animals/m’) at Beals Island*
250000

200000 [ro] REF

150000

Animals/m2

100000

50000

1991 1992 1993 1994 1998
Year
*DM = Constructed Intertidal Flat REF = Reference Site

**Values with ****** indicate linear contrasts are significantly different at p <0.01

Table 3-14. Beals Island Infaunal Taxa Richness ANOVA Results

Source DF Sum Sq. F Ratio
MS i Cel core (er on
Pe aS eee ies ear)
Mo TS Sie iA Se" ia |
Linear Contrasts Results

1991 1992 1993 1994 1998

Estimate 1524 22533) -12133-026009 1267)
t Ratio -1.509 3.113 -0.985 -0.521 -1.101
Prob > |t| 0.133 0.002 0.326 0.6027 0.275

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Table 3-15. Beals Island Infaunal Total Abundance ANOVA Results

Source DF Sum Sa. F Ratio

[Site [1 | 6218 | 3.5578 | <0.0001
ver ois ees oor
EG 12a) wie) sae oot
Lia no eo Monee

[imear Contrasts
1991 1992 1993 1994 1998

Estimate -0.092 -0.436 -0.508 -0.395 -0.450
Std Error 0.087 0.070 0.099 0.099 0.099
Prob > |t| 0.2960 < 0.0001 <0.00010.0001 < 0.0001

Table 3-16. Beals Island Infaunal Total Biomass ANOVA Results

Source DF Sum Sq. F Ratio

Posite [0 | 32452 90.2734 0] <0.0001
[ihe Moe esa acm)
Jee De
sr nti | 28740728 | Oa

Linear Contrasts
1991 1992 1993 1994 1998

Estimate -0.333 -0.702 -0.497 0.598 -0.431
Std Error 0.128 0.103 0.149 0.146 0.146
Prob > |t| 0.0102<0.0001 0.001 0.0001 0.0036

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

39

40

Figure 3-22. Infaunal Biomass (Grams Wet-weight/m’) at Beals Island*

Grams (Wet-weight)/m2

oe N N W UO
Hw S So wa ©o
So So © Sa © ©

1991 1992 1993 1994 1998
Year

*DM = Constructed Intertidal Flat REF = Reference Site
**Values with ****** indicate linear contrasts are significantly different at p <0.01

Biomass structure was slightly different between sites, but was relatively consistent
over time (Figure 3-23). Polychaetes constituted the majority of biomass at both sites with
oligochaetes being second most important at the reference site and oligochaetes or
crustaceans being second most important at the constructed flat. Molluscs contributed
relatively little while miscellaneous groups formed a substantial amount of biomass only in
1998 when a number of large nemerteans were present (personal observation).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

41

Figure 3-23. Beals Island Infaunal Biomass Structure

Misc
GZ Mollusc
fis Crustacea

Oligochaeta

Percent of Total Biomass

— in| Lo | = co — ta o w co
oh oh oh oh oO cy ao oh a oh
YS Pe Se an a Se A ys Oe
Constructed Flat (DIM) Reference (REF)

3.3.2.2 Taxonomic Composition

A total of 78 taxa was collected at the Beals Island sites between 1991 and 1998:
Sixty-nine taxa were collected at the constructed flat and 65 at the reference area. A total
of thirty-three taxa were classified as dominants (Tables 3-17; 3-18). None of the
dominants were found exclusively at either site.

The ten most abundant taxa included (in order of abundance) Tubificoides benedini,
Exogene hebes and Streblospio benedicti, Tectadrilus gabriella, Capitella sp., the
amphipod Ampelisca vadorum, E. verugera, the amphipods Gammarus oceanicus and
Phoxocephalus holbolli, and Polydora quadrilobata (Appendix Table 3). Tubificoides
benedini, S. benedicti and G. oceanicus were always most abundant at the reference area
while T. gabriella and A. vadorum were always most abundant at the constructed flat.
Exogene hebes, Capitella sp. and P. quadrilobata were most abundant at the constructed
flat in 1991, but were more abundant in ensuing samples at the reference area. The
opposite was true for P. holbolli. Exogene verugera was found in exceptionally high
densities in 1992.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

NMDS of the Beals Island data produced a result similar to that found at Sheep
Island. There was a small but persistent difference in taxonomic composition of the
assemblages (Figure 3-24). As might be expected, SIMPER results corresponded closely
with patterns detected in comparisons of the relative abundances (Table 3-19). Tubificoides
benedini, the overall dominant, contributed greatly to dissimilarity and was found in
highest abundance at the reference site. Capitella sp. and Exogene hebes also contributed
substantially to structural differences between assemblages and were most abundant at the
reference site. Other taxa with high abundances at the constructed site included Tectadrilus
gabriella and A. vadorum. Exogene verugera and Fabricia sabella both contributed to
dissimilarity, but only during a single sample period (1992 and 1994 respectively). As at
Sheep Island, the results of the Beals Island taxonomic composition analyses indicated the
assemblages were composed of basically the same suite of taxa but in relatively different
proportions. These differences persisted over time for the most abundant taxa, but varied
between years for the less abundant forms.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

43

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

45

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

Table 3-19. Similarity Percentage (SIMPER) Results for Beals Island Constructed Flat vs

Reference Comparisons by Year*

*Values in bold are the five taxa contributing the most to dissimilarity for a comparison.
Superscripts indicate where abundances were highest (D= Constructed Flat; R =

Reference).

Tubificoides benedini | 12.68 | 8.42" | 8.56" | 8.97" | S24 |
Polydora quadrilobata 2.65
5.44?
4.34
Streblospio benedict
Pygospio elegans | 6.13| 5.82 | 8.03” | —— | —_
Exogene hebes +) 5.87 | —- | 10.5" | 8.99" | 81d |
Tubificoides sp. ‘| 4.15 0.38 | 3.13 | 196 | ——_
Polydora igi
Nereis viren
Heteromastus filiformis 3.21
Edotea montosa
(Glycera dibranchiata [2.51 | 1.43 [091 | 1.42 | —— |
Gammarus oveanicus
Tubificoides netheroides
Mineman vise oo y= =n ae
teone tonga |e | = | 7 | 2.29 | 2.61
(Corophium voluttor [0.61 [2.68 [283 | —- | 2.53 |
Nemertea 0.56 0.42 == on ie
Enehytraeidae |=
Fabrica sabella” +f | 3.27 | 2.56 | 0.43 | 7.02" |
Exogene verugera | ==) 8aI® | | — | — |
[dota balthiea So oT
Spio setosa f= es ae sat ae
eS ee aes

ae en on
es on aem

ee le eae

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

47

48

Figure 3-24. Nonmetric Multidimensional Scaling Plot for Beals Island 1991-1998

LOOT OZ MOSS 1994 M1998

Dredged Material @ ) S
Reference ee) 7) =)

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

49

4.0 DISCUSSION

Intertidal flats are important to the ecology and commercial fisheries of the New
England region. They produce substantial amounts of primary production in a form that is
immediately utilizable by consumer groups which in turn, provides forage for both
commercial fisheries species and migratory shorebirds (Peterson and Peterson, 1979;
Whitlach, 1982). In addition, intertidal flats support soft-clam and bait-worm fisheries
which are of direct importance to local economies (Brown, 1993). As with other coastal
resources, habitat loss or degradation of habitat function is a continuing concern. While
restoration or replacement of coastal habitats such as salt marshes has received
considerable attention over the years, the potential for construction of unvegetated
intertidal habitats has largely been ignored and the potential for beneficial use of dredged
material in construction of such habitats has remained relatively unexplored.

Overall, the project has been a success. Initial concerns that erosion would degrade
the site appear to have been groundless. Although no topographic survey has been
conducted since construction of the flat to directly measure changes in size or shape,
repeated visual observation over nine years, including aerial photography, indicates that the
physical integrity of the site has not been compromised (Figure 1-2; Figure 1-3). The flat
still extends from the midpoint of the western side of Sheep Island to a small rocky outcrop
near the northern end of the island (Figure 1-2). It has retained a roughly triangular shape
at low tide and there is no physical evidence of erosion, e.g., no apparent decline in height
or maximum extent from the shoreline (personal observation). Sediment texture of the
constructed flat and reference areas has remained constant over time with the exception of
1994 when both sites had increased proportions of coarse materials (Figure 3-1). Sediment
organic content has always been highest at the constructed flat, a reflection of the finer
sediments present at this site, and although organic contents declined over time, the decline
was similar at both sites.

The project was also successful in that populations of soft-clams (M. arenaria) and
clam-worms (N. virens) were established at the constructed flat. Of the two species,
clearly the soft-clams were the most successful, with commercial-size clams (~50 mm)
being present as early as 1992 (Figure 3-7). The continuing presence of adult clams in
1998 (Appendix Table 1) and smaller clams throughout the study (Figure 3-5) indicate that
the soft-clam population is firmly established. Anecdotal evidence in the form of personal
observations of rakers on the flat in 1994 and the presence of numerous raking pits on the
flat’s surface in 1998 are also indicative of a viable clam population. A clam-worm
population was also established at the constructed site. Small worms have been consistently
present throughout the study (Figure 3-8) and large worms were abundant in both 1991 and
1992. The absence of large worms in 1998 might seem to belie the conclusion that a clam-

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

50

worm population has been established, but evidence from long-term monitoring of worm
populations and life-history information indicate that periodic population “crashes” may be
characteristic of the species. Monitoring of populations of the congener N. diversicolor in
the middle reaches of the Forth estuary (Scotland) over a 35 year period detected periodic
declines in abundance (McLusky and Martins, 1998). Similar patterns are evident in
abundances of intertidal populations of the same species from the German coast (Dorjes,
Michaelis, and Rhode, 1986). The periods of decline appear to occur at 5-6 year intervals
or multiples of this interval which coincides with the reproductive period of the species.
During reproduction the adult worms emerge from the sediment and swarm at the surface.
After reproduction the adults disperse or die resulting in periodic disappearance of adult
worms from the sediment. Nereis virens has an expected life span of seven years and
shares most of the life-history characteristics of N. diversicolor including its reproductive
behaviors (Pettibone, 1963). While other factors cannot be excluded in accounting for the
absence of large worms, the simultaneous absence of large worms from both sites and the
coincidence of the time period with the clam-worm’s life span suggest the 1998 data are
the result of normal interannual variation. Alternative explanations are obviously possible
and include over-harvesting or some non-site selective disturbance (e.g., pollutant release,
ice-scouring, etc.). There is no objective way of distinguishing between the potential
explanations from the present database.

Finally, a healthy infaunal community has been established at the constructed flat.
The infaunal assemblage is similar to the reference area in respect to taxa richness (Figure
3-14) and abundance (Figure 3-15). Diversity of the Sheep Island sites is also comparable
to other North Atlantic intertidal assemblages (Table 4-1). Diversity, as measured by
Shannon-Wiener’s H’, ranged from 1.18 to 2.88 at the constructed flat and 1.84 to 3.05 at
the reference area. These ranges closely correspond to H’ values reported for other Maine
intertidal flats (e.g., Larsen and Doggett, 1991), Bay of Fundy flats (Ambrose, 1984) and
Massachusetts flats (Whitlach, 1977). Likewise, abundances at the Sheep Island sites
(11,000 to 95,000 animals/m’) are similar to those reported for other North Atlantic
intertidal flats (Table 4-1). Total biomass was lower at the constructed flat than the
reference area, particularly after 1992 (Figure 3-16), reflecting higher abundances of
oligochaetes and molluscs (Figure 3-17). While the similarity between the Sheep Island and
Beals Island biomass results, i.e., lower biomass at constructed flats, might seem to be of
concern, data from other New England intertidal flats indicates that these values are well
within normal bounds (Table 4-3). Bowen, Pembroke and Kinner (1989) measured biomass
at a number of intertidal flats in southern New England and reported values ranging from 6
to 612 g/m? and averaging 164 g/m’. Biomass at the Sheep Island constructed flat ranged
from 76 to 181 g/m? and averaged 125 g/m’, while the Beals Island constructed flat ranged
from 32 g/m’ to 127 g/m’ and averaged 72 g/m’. Average biomasses at the Sheep Island
and Beals Island reference areas were 285 g/m’ and 139 g/m’ respectively. Biomass

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

composition varied substantially among the southern New England flats (Table 4-3) and

51

like the study area flats, was dominated either by annelids or molluscs (Bowen, Pembroke,
and Kinner, 1989).

DM

Table 4-1. Diversity and Abundance of North Atlantic Intertidal Flat Infauna

Reference i m’)
gg frre cal swe Rau tuna tar sacra 34
Kitte
Falmouth
Boothbay Harbor

Diversity (H')| Abundance (X107/

te
p
Lan]
nm
@)
3
eb)
=)
Q
a
e)
@
oo
—
=
\O
No)
—

East Friendship

Addison
Whitlach (1977)
Sanderstetale(1062)emenbl th tahtak | jake 7-35 5m mene
Ambrose l(oe4)nuuamo ok ke S| es 3 eee
fuel CA EA CCSS een a ee
Commito (1982) era ee ee
|CommitoleiShrader (1985) lie mn 2011
[ise oe Sa ce SE I ca)

iZ2)

= Constructed Flat

REF = Reference Area

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

52

Table 4-2. Species Composition of North Atlantic Intertidal Flat Infauna
[ME] ME|ME|ME|ME|ME|ME] ME | ME | ME | ME |Fundy|MA|MA|
| Reference | _1 | 2 | 3 | 4 | 5 | 6 | 7 |SIDM|SIREF|BIDM|BIREF/8- 10] 11 | 12 |
Ree ee en ee ee Pos LL
BiCihe A EE ieee ee SEea
(Giese et) i ae EEE ee eet
Cetera Year La) | P| a a EN |
[SrAtmaphiiteite jokimsoni (|) | HU] 5-15 | Beale e On te | ee a
RS SCS ee Ee ee ecm | |
yar a tora || |e | RD |e] | | | | a
(URDU el (ee eee (Po ee es |
love ERO etn HEB eS di] |p iit Pat [|stats] ctl staat te
RCAC on en Oe Ee eee en ee eS es aS
Retreat ie i PE eS eee aes ae Le
Exe te rcrmaas urs lafcorals | Get | nny | Nn | EDN ORG] |NRE |GRr |
BC i ie Sa
pe Netty! acta GREE PS ea | ST a
GG a eS ESSE See EE Le
Eee i iin
[icine in Ea es Ee ee ea Le |
PER estore arash [ie tna een (on (ror [P| PS Se
[Secale eee see ee a ee ce a
See

ee a ee]

pc + ecu sea
orb vrai | ieee [eee |]
fix Gammarus sp. 77 OI=2]5 [re [PSY 7 a
|Phoxocephalus holbolli| T°) I ee ee ee
ll a ai ee Ls | |
SPA Gemma’ gemma’ S| Teele [Poise ee ey | a
Eee i eS eae
iMate OW] an |e] se

+ = Present +* = Listed as sp. or congenor
+1! = listed as Sabella fabricia

References:

1 - Larsen and Doggett (1991) 7 - Thiel and Watling (1998)

2 - Ambrose (1984) 8 — Wilson (1988)

3 - Commito (1982) 9 — Wilson (1989)

4 - Commito and Shrader (1985) 10- Wilson (1991)

5 - Commito (1987) 11- Sanders et al. (1962)

6 - Brown and Wilson (1997) 12- Whitlach (1977)

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

53

Table 4-3. Comparison of Biomass and Biomass Composition Results with other New
England Intertidal Flats

Site [Biomass g/m2
Fa See aL OT

[New Hampsties | NE | 7 ena ono |r aoe ar aloo
Massachusens* [Mal [6 | #3 [00 | 167 [00 |
oa sce Sw TVS TSO a TOE |
Soest I] 1 lS uv NTT TRON |
lnnConnecieut® [ACONN) |W hui612 | tas) |) cealit eel MOO |
ASH ena DATO9 | AT Rise 29 S|iNTA Da) E SORMLONOANE |
Steep sens [pvt 92 | 166 [a0 fine
sheep Island [DM194[_i81| 46 | 46 | 908 | 00 |
[Sheep Island [DMi198| 76 | 306 | 406 | 288 | 00 |
L Seon enn ea a en | |
3

Sheep Island [REF 1994[ 428. | 66 | 02 | 932 |
Bess isan’ | Dwrigor [| ons |
Een | en ware ie Re
Beais sland [DM1994|_127_—~«|~—si22—«?s=Ci dCi
3
[Beals stand [REF] _54_-| 909 | 91 | 00 | 00 |
GLE: (an Osa aos ao |
SB ee ToT TS TO
[Beals stand [REF I94| 44 «| ied odd
[Beals Ilana [REF I996| 334 «| ~—5 dP Sd C_id

DM = Constructed Flat
REF = Reference Area

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

54

Infaunal species composition of the Jonesport study sites was similar to other
Maine, Bay of Fundy and New England intertidal flats (Table 4-2). In a study of a number
of Maine flats Larsen and Doggett (1991) reported oligochaetes as the most abundant and
commonly occurring taxon. In fact, more than half the regional studies of intertidal infauna
list oligochaetes as one of the dominant taxa. While most of these studies do not identify
which species are present, Commito (1987) has reported T. benedini as the most abundant
species in a study at Bob’s Cove, Maine (also in Washington County). Other taxa
commonly described as dominants in North Atlantic intertidal assemblages include the
amphipod Corophium volutator, the polychaetes Heteromastus filiformis, Nereis virens,
Polydora spp. and Streblospio benedicti, and the bivalves Macoma balthica and | Mya
arenaria. All are among the Sheep Island dominants (Table 4-2).

The very high infaunal abundances encountered during the first sampling (June
1990) suggest that community development was not yet complete. Typically infaunal
assemblages progress through a series of successional stages beginning with a community
composed of a few pioneering species present in extremely high abundances (e.g., Pearson
and Rosenberg, 1978; Rhoads and Boyer, 1982; Rhoads and Germano, 1982). This
assemblage consists primarily of small tube-dwelling polychaetes or small bivalve molluscs
colonizing the surficial sediments. Over time the pioneering fauna are replaced by slightly
larger, longer-lived and deeper burrowing infauna. These later assemblages are more
diverse but less abundant and often include tubiculous ampeliscid amphipods and shallow-
dwelling bivalves (Santos and Simon, 1980). Finally, a highly diverse assemblage
dominated by large, long-lived, and deep-burrowing animals such as maldanid polychaetes
develops. Alternatively, there may be no predictable successional sequence, but simply a
rapid colonization by whatever taxa are present in nearby sediments (e.g., Diaz, 1994;
Zajac and Whitlach, 1982).

There may also be an annual successional sequence as described by Trueblood,
Gallagher, and Gould (1994) in Boston Harbor. This sequence has three “stages”: a spring
assemblage dominated by harpacticoid copepods, a spring-summer assemblage composed
of oligochaetes and the polychaetes Capitella sp., S. benedicti, and P. elegans, and a fall-
winter assemblage dominated by P. ligni. Whitlach (1977) has reported a slightly different
seasonal sequence with spring dominants being the amphipod C. insidiosum and the
polychaetes Marenzellaria viridis and Scoloplos sp. Summer dominants included S.
benedicti, H. filiformis, and Gemma gemma and fall-winter dominants included Mya
arenaria and Capitella s sp.

The high abundances encountered during the first sample period (June 1990) may
correspond to the pioneering stage described by Pearson and Rosenberg (1978) and Rhoads
and others (Rhoads and Boyer, 1982; Rhoads and Germano, 1982). Likewise, high

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

55

constructed flat taxa richness at this time may reflect a change in community structure from
the pioneering stage to a later more diverse assemblage, i.e., high diversity was due to the
presence of both assemblages. Other lines of evidence include high variability in taxonomic
composition of constructed flat samples (NMDS results), which is suggestive of infaunal
response to disturbed conditions (Warwick and Clarke, 1993) and domination of
constructed flat benthos by Capitella sp. and P. elegans, opportunistic species which are
early colonizers of disturbed sediments (e.g., Shull, 1997; Thiel and Watling, 1998).
Alternatively, both taxa were dominant at both sites and were equally or more abundant in
later samples (Appendix Table 2). As previously noted these species have also been
reported as summer dominants under undisturbed conditions (Trueblood, Gallagher, and
Gould, 1994). It is unclear from the available information whether or not a pioneering
assemblage was detected. What is clear, is that by 1991 the infaunal community of the
constructed flat was similar in most regards both to the reference site and other intertidal
flat assemblages in the North Atlantic.

Beals Island, an example of a thirty year old flat resulting from intertidal disposal of
dredged material, appears to have been somewhat less successful. Unlike Sheep Island, a
commercially viable soft-clam population has not been established, however, there is a
substantial clam-worm population. Reasons for the relative failure of the soft-clam are
uncertain but may be related to substrate. Sediments at the Beals Island constructed flat are
far more cohesive than corresponding sediments at Sheep Island (personal observation).
The cohesiveness of Beals Island sediments may be less conducive for the shallow
burrowing behavior of the clam. The more intense disturbance of the Beals Island
reference flat by worm-rakers may also result in increased clam mortality (Emerson,
Grant, and Rowell, 1990). Differences in clam-worm abundances between Beals Island
sites may also be related to substrate. The cohesive sediments of the flat are difficult to
traverse and may be avoided by professional worm-rakers. The rakers have limited time
between tides to gather their harvest and any delay means lost income. Although the
constructed flat cannot be considered a success in the sense of direct harvest it still
represents a “seed bank” of worms to replace animals harvested from the remainder of
Alley Bay and elsewhere.

The infaunal community of the Beals Island constructed flat was also somewhat less
developed than at the reference area. Although taxa richness and taxonomic composition
were roughly equivalent between sites (Figure 3-20; Appendix Table 3), constructed flat
abundance and biomass were much lower than reference area values (Figure 3-21; Figure
3-22). The differences in abundance and biomass were not restricted to a single group as
evidenced by similar biomass composition (Figure 3-23), but are more general in nature.
Reasons for the difference between constructed flat and reference area values are most
likely related to substrate, elevation and vegetation (intertidal Zostera marina beds).

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

56

Despite these differences the constructed flat is still comparable in diversity, abundance
and species composition to other intertidal flats. Diversity (H’) at the constructed flat was
well above most other North Atlantic flats (2.8-2.9), abundance was within normal ranges
(~ 30,000 animals/m7), and species composition was similar to other sites (Table 4-1;
Table 4-2). As previously discussed biomass and biomass composition were also within the
range of values measured at other New England intertidal flats (Table 4-3).

5.0 CONCLUSIONS

The principal conclusion from the monitoring effort at Sheep Island is that a
physically stable and biologically functional intertidal flat has been produced. A
commercially exploitable population of the soft-clam, Mya arenaria, has become
established at the constructed flat as well as a population of the bait-worm Nereis virens.
Within three years of construction, the infaunal community, an important source of forage
for both fish and shorebirds, developed to within expected values for diversity, abundance,
and species composition. At Beals Island, a much older constructed flat resulting from
intertidal disposal of dredged material, a substantial population of N. virens and a well
developed infaunal community were present. Neither constructed flat supported the same
level of total infaunal biomass found at the respective reference areas, but the measured
values were similar to those of other New England intertidal flats.

Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

57

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Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine

mma ESTING

Alley Bay, 8, 61

Ampelisca, 39, 45, 51,57, 72, 75
amphipod, 4, 33, 38, 45, 60, 65
amphipods, 1, 45, 60

Analysis of Variance, 13, 67

beneficial use, vii, 1, 4, 53, 64, 66

benthic communities, 1

biomass, vii, 1, 12, 13, 14, 28, 32, 40, 44,
555 CP

bivalves, 60

Capitella, 33, 39, 45, 46, 51, 57, 60, 61,
Uils 2

cohesive sediments, 61

colonization, 1, 60, 66, 67

commercial fisheries, 1, 53

Corophium, 4, 33, 38, 39, 51, 57, 60, 65,
Ves TS

crustaceans, 32, 44

cubic meters, 4

cubic yards, 4

diatoms, 1

disposal area, 9

disposal site, 9
disturbance, 54, 61, 63, 68
Diversity, vi, 54, 55, 62
dredging window, 4

erosion, 1, 8, 53, 63
Exogene, 33, 38, 39, 45, 46, 51, 57, 71, 74

fish, vii, 1, 62

Gammarus, 33, 38, 39, 45, 51, 57, 72, 75
Glycera, 4, 13, 14, 51, 57, 70, 72, 74
Great Wass, 8

Habitat development, 1
harbor seals, 8

Heteromastus, 51, 57, 60, 71, 74

ice, 8, 54, 63, 64, 68

infaunal community, vil, 54, 61, 62, 68
Intertidal flats, vii, 1, 4, 8, 53

intertidal habitat, 1, 8

Jonesport, vii, 4, 8, 60, 64

Macoma, 57, 60, 73, 75
marsh, 8, 67

marshes, 1, 53
molluscs, 1, 32, 55, 60

NMDS, 14, 33, 38, 46, 61

Oligochaeta, 13, 39, 57
oligochaete, 13, 14, 38
organic content, 12, 15

pioneering species, 60

polychaetes, 1, 32, 33, 38, 60, 63
Polydora, 33, 38, 39, 45, 51, 57, 60, 71, 74
primary production, 53

productivity, 1

rakers, 54, 61
recruitment, 22, 25, 66

salinity, 8

Sediment organic content, 12, 15, 17, 53
shorebirds, vii, 1, 4, 8, 53, 62, 64
SIMPER, v, vi, 14, 38, 39, 46, 51
Streblospio, 33, 40, 45, 51, 57, 60, 71, 74

taxa richness, 14, 28, 40, 54, 61, 62
taxonomic composition, 38, 46, 61, 62

worm rakes, 9

Zostera, 62

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Appendix Table 1. 1998 Worm-Rake Collection Data

Site Species (No.) Size (mm)

12 non SS ea Mm ti oa
ee ees ee ae
Sea So rr | Mien, arian Sod een
FS a ee a ae
ae eo ele
ess __ vee) te
es Se arenaria (2) oe 22
howeam en fee coe -11 | Mya arenaria(3) | arenaria (3) [ae ae | DOD)
Mya aremaria (3) 20, 46, 53
Mya arenaria (2) 52, 64

Appendix Table 2. Sheep Island Taxa List and Abundances (No./m’).

Constructed Intertidal Flat Reference Area
irtaenene Pa 11DM92 |DM94 |DM98 |REF90 |REF91 |REF92 [REF94 [RE
OLIGOCHAETA _ ee a | Ps ——

eo ee Es
Tectidrilus gabriella |_| _4249|_1613|_440]_1149| | 5650] 13407] 9837] 22528
INibifcaides neteroties [ool 220 ool
Tubifieidessp.__{_o|_dt_df__gf_ql_qi__f__q sj
Enchytracidae 1 |_|, 0) 00/513 | To | ol23t0/ aes
acanis ioral —_-——|-~0|= oh} ol 0) 00s) tole =0 on a
POLYCHAETA __| | __|§ — | toto ee =e eS
Capielides p00 toon ool
Capitomastus jonesi___ | |_| 733]_ Sot ofS
[Heteromastus filiformis | 29 220[ 880|__220[_220[_of_—220]_~ 220]
Ophelina acuminata | 0|_-293[ 440 of ota] 220] ot
Aricidea suecica |_| 220| 220] of of 220] oo
Naineris quadricuspida_ | 0] _o|_—of_— Sou]? 220] SF
[Scoloplos acums 1 [ss soli 220/10] oles 0] 0/| to aS
Pherusalaffinis | se 0|k_220| | 0] joint 0 409/ Soe
Clymenellatorquata___ | of 943[_— off 579|_ 2140] 1265| oo]
Euclymene zonalis | ol) of | of) 0 ol 4) oo ole
Maldanidae | 0) 0] 10) ool oe
Mharyx sp [ea 20/30] fo ol 220) os 264/70 a ee
Fabricia sabella |_|] 220] 20/9577] | 3007] 440] 3476
Polydora quadrilobata
Pygospio elegans | 4036| 682 220i So] 640/660] 264]

Scolocolepides viridis a a a

ee ee ee ee ee :
Streblospio benedicti__ | | __—0f__1163|_2577| 11000[ o_o] 3419] 682] 308
Fs longa 3a —o} — 230] — 220] — 468] of ol of 2931 20

Phyllodoce maculata a
SR BE | 220] 220] oo io] 22020 a
Phyllodooearenae fof _of ae
Exogenehebes | 14] 9130 528] 220| 220/463] 6734 1678[ 220/513]
Esagemvenssa [of of hell
Nereis virens | 72] 452[_ 524] 440| 592] 29] 402] 508] 367] 1100
Nereis diversicolor alo oo) a
INereisisp. 29) of 0) os ol is01| i oo oa
Nepthys incisa 100 = || is0/i220| 70 /io os e20 Ts
INephtys cacca | ool ool od oo
Nepthyidae 0] oo oo seo EO ae

Appendix Table 2 (Cont.). Sheep Island Taxa List and Abundances (No./m’).

a Intertidal Flat Reference Area
POLYCHAETA ae Ree ol ae FEE ea |

Glyceracapitata |] Same ee a ore
Cendant e
Reiners i 0 ii i i a Pe a

Veins it Soe es
[Bratecdanvilfealcefexte nl iii |i 0 (ONG ARO RO] i720 | eaaNO To |G
Protodorvillea gaspenses|__O| O_o] S27]
[Sliisfomer ing os/caeealinn | NNO | NNO| AIO RG NN io | SIRAG AE o | ieaisen ano eso
[Hiarmiothioe vimbricatal |laaee0| NNO] 7 0010) SENG | 0 | RO a oOo 20
icin Th toe SE 7 ao

eG

CRUSTACEA-.

core a Oe ee eel, oe | LO
[Ampelisca vadorum |__| __-422|_—220|_—-220| of 14] 745/220] 220]
Coan st Tio DS Oa eae a
ee ae aa a
Gammarus oceanicus_| 14] _691| 1387 __374|_ 19910 _347|_—220|_—770|__—*943|_1665|
caer mecalsne || AOA col lon a 0
Came aa A ee COE Cae ole

Reneeermennc’ | OUEMMGla: ol” UOMO al RO a ol OS
ets) ae eC ee ir aoe ar orn
———————————————
[Phoxocephalus holbolli_| _28{ 2035| 220 so] ~~ 72| 1748] ~—24al SC
he ee ba oe ee ee
GRUSWACEAMsopeda.. |< Summa a0 |. etn Ra eae
Edotea montosa RG sso io 220 A 2 es 0 |
Jaera marina UE od er a a a ata
iptiiatathuraltentis i iil omen O RNG NO] Co 20 oo AAG ro aA)
CSI Mrmr LOT UE ee Ta
Leptognatha cacea Rhea rr ee aS Ce Ore
Leptochelia savigni DMT DOT “COS aa oS Ga
(CRUSTAGEAEMise. | sla eT” A aa 2
Eudorella pusilla PSO a a ee Eo OG)
Onimayicmilnn Ol si ean ane ol we oe on
Ndiaye stant ricarilala (nO) MS)(ei DOING | NG 220 iO 70 Eo io iC)
Scottolanacanadensis | _0|_-440{—440/_—220| ~—220[ ~~ 60] 275] SSC
Crangon septemspinosus| 0] of |S 1320) ~~
Cephalocarida ESC iO REO a eC eC eG)

Appendix Table 2 (Cont.). Sheep Island Taxa List and Abundances (No./m’).

aa Intertidal Flat Reference es

CRUSTACEA | _
See a a TS
Diptera Weslo | 0) Sao Nol. ABO j. 7293) 1 10 0
CT a a To
ae |

io |
Myaacemra [3936 ser] a9 aol 0 aie |
Bialve spe oto oa ob |
MOLLUSCA-
Gastropoda

| ol solo) 1228/2201 igs] sho) 220/ies |
ee

FST ei | 2.) oe
Te i ia Cee
Platyhelminthies 01 | 0) _NO|____ si] Mo]. 20|_ 1. io] Sao Ao

a
hie
ib

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