3. MID-ATLANTIC COASTAL HABITATS AND
ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL
RISE
This section should be cited as:
Strange, E.M., A. Shellenbarger Jones, C. Bosch, R. Jones, D. Kreeger, and J.G. Titus.
2008. Mid-Atlantic Coastal Habitats and Environmental Implications of Sea Level Rise.
Section 3 in: Background Documents Supporting Climate Change Science Program
Synthesis and Assessment Product 4.1, J.G. Titus and E.M. Strange (eds.). EPA
430R07004. U.S. EPA, Washington, DC.
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3.1 Overview
Author: Ann Shellenbarger Jones, Industrial Economics Inc.
This overview considers the species and habitats
of the mid-Atlantic from Virginia to New York
that are at risk from sea level rise. For different
habitats in this region, the ecological
implications of sea level rise vary in extent and
certainty. Vegetation type, soil type, sediment
inputs, and current ecological health can all
affect the ecological response to sea level rise. In
turn, the animal species that depend on these
habitats for activities such as foraging or nesting
will vary in their responses to habitat changes,
depending on species-specific responses to
changes in inundation, salinity, vegetation
structure and composition, and other habitat
characteristics. Where it is used, shoreline
armoring will influence the ability of both
habitats and biota to adapt to sea level rise. The
following bullets summarize the assumptions on
potential responses of mid-Atlantic habitats to
increasing rates of sea level rise and shoreline
armoring, based on answers to CCSP 4.1
Questions 2 and 31:
• Rising sea level can cause tidal marshes
(e.g., salt, brackish, and freshwater tidal
marshes) to erode at the waterward
boundary; drown in place and convert to
open water; vertically keep pace with sea
level rise through sedimentation and peat
formation; and/or expand inland as areas just
above the level of the tides become
inundated. If sea level rise increases the
salinity of an estuary, the vegetation
composition of brackish and freshwater
marshes may shift to more salt-tolerant
'Question 2: How does sea level rise change the ocean coastline?
Among those lands with sufficient elevation to avoid inundation,
which land along the Atlantic Ocean could potentially erode in
the next century? Which lands could be transformed by related
coastal processes? Question 3: What is a plausible range for the
ability of wetlands to vertically accrete, and how does this range
depend on whether shores are developed and protected, if at all?
In other words, will sea level rise cause the area of wetlands to
increase or decrease?
species. In areas where habitat is lost or
degraded, the myriad species dependent on
marshes—birds, fish, invertebrates, and
mammals—may show decreased growth,
reproduction, or survival.
• Tidal freshwater swamp forests, like
marshes, can retreat at the waterward
boundary; drown in place; keep pace with sea
level rise; and/or expand inland. In addition,
saltwater can induce vegetation shifts or
cause swamps to convert to open water by
oxidizing organic soils or inducing
subsidence. Within the study region, these
swamp forests are found primarily in the
tributaries of Chesapeake Bay. With
inundation, an associated increase in salinity
in the upper reaches of rivers will cause
larger trees to die, opening space for
germination, settlement, and establishment of
marsh macrophytes.
• Marsh and bay islands are found throughout
the mid-Atlantic study region. These isolated
areas provide nesting sites that are protected
from predators and human disturbance for
various bird species, particularly colonial
nesting water birds. Because of their limited
migration ability, these islands are
particularly susceptible to sea level rise.
• Sea level fens are an extremely rare type of
coastal wetland. These fens grow only under
unusual circumstances—where a natural seep
from a nearby slope provides nutrient-poor
groundwater to support their unique
vegetation and where the fens are protected
from nutrient-rich tidal flow. Sea level fens
are present in Delaware's Sussex County
Inland Bays watershed, on Long Island's
South Shore, and on the eastern shore of
Virginia's Accomack County. Because sea
level fen vegetation needs nutrient-poor
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[ >N 3,1 189 ]
waters, these unique wetlands might not
survive inundation by sea level rise.
• In nearshore waters, rising sea levels and
deepening waters will shade the deeper areas
of submerged aquatic vegetation (SAV) beds,
limiting photosynthesis. The landward edges
of SAV may move inland onto areas that are
currently tidal wetlands if the water bottoms
have suitable sediments. Seagrasses (e.g.,
eelgrass and widgeon grass) provide food
and shelter for a variety of fish and shellfish,
food for the species that prey on those fish
and shellfish, and physical protection from
wave energy for shorelines. Scientists are not
certain of the likely net change in SAV,
which will depend on the balance between
losses resulting from increasing depth in
current beds and gains due to migration into
inundated shoreline areas.
• Tidal flats may be readily lost with rising
seas, but may also be created temporarily in
areas where wetlands are inundated. Loss of
tidal flats would eliminate a rich invertebrate
food source for migrating birds.
• Estuarine beaches erode, but under natural
conditions the landward and waterward
boundaries usually retreat by about the same
distance. In the built environment, structures
can prevent the system from migrating
inland, in effect causing the beaches to be
squeezed between developed areas and the
water. Society will preserve many beaches
with sand replenishment (beach
nourishment). In areas that do lose beaches,
though, insects and other invertebrates such
as sand diggers, sand fleas, and numerous
crab species will lose their habitats.
Shorebirds that rely on beaches for forage
and nesting will also face more limited
resources.2
• Cliff areas can experience increased erosion
rates, or, if the cliff base is armored, the
erosion rates can decrease. In the latter case,
2Lippson, A.J., and R.L. Lippson, 2006, Life in the Chesapeake
Bay, 3rd ed., The Johns Hopkins University Press, Baltimore,
MD, pp. 26^2. For more detail on beach habitats and the species
that occur in them, see Section 3.1.7 of this section.
however, the armoring can eliminate habitat
for species (e.g., Puritan tiger beetles and
belted kingfishers) that depend on varying
rates of cliff erosion.
This section gives a general description of
vulnerable coastal habitats and potential
ecological consequences of sea level rise and
shoreline armoring in the U.S. mid-Atlantic
region from Virginia to New York. The
information presented here is based on current
scientific understanding as well as the
observations of local experts. In each section that
follows this overview, we begin by describing
the type of habitat (refer to the previous bulleted
list), then discuss potential ecological responses
to sea level rise and to shoreline armoring (if
any) for that type of habitat, presenting case
studies for specific bays, estuaries, and back
barrier lagoons of the mid Atlantic from New
York to Virginia.
Various general assumptions are made in this
section based on other information from the
CCSP and the scientific literature. Assumptions
for marsh survival rely on the response to CCSP
4.1, Question 3 (Reed et al., Section 2.1), which
describes accretion expectations under three sea
level rise scenarios for marshes in the mid-
Atlantic region. The three scenarios are (1) the
current rate of sea level rise, (2) an increase of 2
mm/yr above the current rate, and (3) an increase
of 7 mm/yr above the current rate. The accretion
expectations take into account sediment inputs,
marsh characteristics, and historical processes,
among other considerations.
Changes in salinity are not directly considered in
this section. In the absence of other factors, sea
level rise is expected to drive the salt front
farther upstream in estuaries and tributaries. For
example, one estimate for the Delaware River is
an 11 km movement upstream for the salt front.3
More recent models, however, indicate that any
concomitant changes in freshwater inputs to
tributaries may negate the upstream drive of the
3Hull, C.H.J., and J.G. Titus, 1986, Greenhouse Effect, Sea-Level
Rise, and Salinity in the Delaware Estuary, US EPA 230-05-86-
010, U.S. EPA and Delaware River Basin Commission,
Washington, DC, p. i.
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[ 190 ' ' i 1]
salt wedge.4 Although salinity change can have
profound effects on both flora and fauna, we do
not consider it in detail here because of the
uncertainty associated with salinity.
Changes in water depth will be a function of the
rate of sea level rise and the rate of
sedimentation.5 In embayments and estuaries
where the tidal prism increases, increased water
depth is likely.6 In Chesapeake Bay, some
researchers anticipate a water depth increase of
almost 20 percent.7 On the other hand, studies in
England have indicated that estuarine channels
might become both wider and shallower, which
may be an effect of sedimentation and local
geomorphology.8 Increased tidal prism is also
associated with an increase in interior ponding in
marshes, along with tidal creek bank erosion,
which can lead to catastrophic marsh loss (as in
the Blackwater Wildlife Refuge on Maryland's
Eastern Shore).9 We assume that in areas where
marshes are not expected to accrete sufficient
sediment to remain in place, an increase in water
depth will occur over any given area waterward
of the marsh. Shoreline protections can further
affect local water depths and are discussed in
each section as necessary.
3.1.1 TIDAL MARSHES
Tidal marshes are characterized based on
salinity. Freshwater marshes receive significant
4Najjar, R.G., H.A. Walker, P.J. Anderson, E.J. Barron, R.J.
Bord, J.R. Gibson, V.S. Kennedy, C.G. Knight, J.P. Megonigal,
R.E. O'Connor, C.D. Polsky, N.P. Psuty, B.A. Richards, L.G.
Sorenson, E.M. Steele, and R.S. Swanson, 2000, "The potential
impacts of climate change on the mid-Atlantic Coastal Region,"
Climate Research 14: 219-233, pp. 224-225.
'National Research Council (U.S.), 1987, Responding to Changes
in Sea Level: Engineering Implications, Committee on
Engineering Implications of Changes in Relative Mean Sea
Level, National Academy Press, Washington, DC, p. 36.
6Levin, D.R., 1995, "Occupation of a relict distributary system by
a new tidal inlet, Quatre Bayou Pass, Louisiana," pp. 71-84 in
Tidal Signatures in Modern and Ancient Sediments, B.W.
Flemming and A. Bartoloma, eds., Special Publication of the
International Association of Sedimentology (vol. 24.), Blackwell
Science, Oxford, U.K.
7Stevenson, J.C., M.S. Kearney, and E.W. Koch, 2002, "Impacts
of sea level rise on tidal wetlands and shallow water habitats: A
case study from Chesapeake Bay," American Fisheries Society
Symposium 32:23-36.
8Pethick, J., 1993, "Shoreline adjustments and coastal
management: Physical and biological processes under accelerated
sea-level rise," The Geographical Journal 159(2): 162-168.
'National Research Council, 1987, p. 69 (see note 5).
freshwater input and have waters that contain
less than 0.5 parts per thousand (ppt) of ocean-
derived salts. The waters of brackish (estuarine)
marshes are less than 18 ppt. Salt marshes
receive substantial inundation by ocean waters
and have waters that can reach 30 ppt. As
discussed in the following sections, numerous
finfishes, birds, crustaceans, mollusks, reptiles,
amphibians, and mammals rely on tidal marshes
for at least part of their life cycle for resources
such as food, shelter, nursery habitat, and nesting
or spawning sites.
Salt marshes are among the most productive
systems in the world, rivaling the productivity of
agricultural lands. These marshes are the primary
source of much of the organic matter and
nutrients that form the basis of the estuarine food
web.10 Primary productivity includes both
aboveground production (stalks and leaves) and
belowground production (roots and tubers) by
marsh plants as well as benthic algae. Much of
the aboveground primary production is in the
form of cellulose, which most animals cannot
digest. Therefore, most vascular plant material is
consumed by detritivores such as copepods,
amphipods, annelids, snails, and insect larvae.11
In turn, these organisms provide food for
macroinvertebrates such as saltmarsh snails,
ribbed mussels, and fiddler crabs, and small
resident fishes such as mummichogs, sheepshead
minnows, and Atlantic silversides.12 The
abundant invertebrates and small fishes of salt
marshes are food for larger consumers. Bay
anchovies, silversides, and other small schooling
species use salt marshes as nursery grounds and
are a food source for birds and piscivorous
fish.13'14
10Teal, J.M., 1986, The Ecology of Regularly Flooded Salt
Marshes of New England: A Community Profile, U.S. Fish and
Wildlife Service Biological Reports 85 (7.4), 69 pp.
"Currin, C.A., S.Y. Newell, and H.W. Paerl, 1995, "The role of
standing dead Spartina alterniflora and benthic macroalgae in
salt marsh food webs: Considerations based on multiple stable
isotope analysis," Marine Ecology Progress Series 121:99-116.
12Teal, 1986, pp. 21-25 (see note 10).
13McBride, R.S., 1995, "Marine forage fish," pp. 211-217 in
Dove, L.E., and R.M. Nyman (eds.), Living Resources of the
Delaware Estuary. The Delaware Estuary Program.
14Lippson and Lippson, 2006, p. 212 (see note 2).
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[ SECTION 3.1 191 ]
Photo 3.1: Marsh and tidal creek, Mathews County,
Birds that feed on crustaceans, mollusks, and
fish within salt marshes include clapper rails,
black rails, least bitterns, and many species of
terns and gulls. Fiddler crabs are common in the
diets of clapper rails, egrets, blue crabs,
diamondback terrapins, and raccoons. Some of
the birds are marsh-nesting obligates; others nest
frequently, but not exclusively, in marshes.
Three species of terns (including Forster's tern),
several species of gulls, and the seaside and salt
marsh sharp-tailed sparrows all nest in coastal
salt marshes;16
In addition to secondary production within the
marsh, some primary production may ultimately
contribute to the surrounding estuarine food web.
Kneib proposes that this occurs via "trophic
relays," which consist of juvenile fauna that
draw on the detrital food web of the marsh and
then transfer marsh-produced organic matter to
larger consumers as part of the estuarine food
web.17
Tidal creeks and channels frequently cut through
low marsh areas, functioning to drain the marsh
surface and serving as conduits for nekton (small
fish and decapod crustaceans) to enter the
wetlands during high tides and for nutrient-rich
plant detritus to be flushed out into deeper water
with receding tides (see Photo 3.1).21 Several fish
species that are marsh residents and use the low
marsh when it is flooded at high tide are found in
tidal creeks at low tide, including Atlantic
silversides, mummichogs, striped killifish, and
sheepshead minnows. Marsh creeks support
significantly higher densities of these species
than other intertidal habitats.22
Salt marshes are
characterized by distinct
vegetation zones based on
the degree of tidal
flooding and the salinity
tolerance of marsh plants.
Because they are
regularly flooded by daily
tides, low marsh soils
tend to be more
waterlogged, saline, and
anoxic than high marsh
soils.iS Low marsh is
clapper rail, willet, marsh
wren, seaside sparrow,
and American black duck. Ribbed mussels form
dense clumps on cordgrass roots and fertilize
them by contributing phosphorous and nitrogen-
rich pseudofeces.19 Fiddler crabs enhance
Spar Una spp. survival by aerating the marsh
soils.2"
Virginia15
characterized by
monospecific stands of
smooth cordgrass.
Characteristic bird species
of low marsh include
l ,All photos are courtesy of Jim Titus, except for Photo 3.3a by
Elizabeth Strange.
l0Erwin, R.W., G. M. Sanders, and D. J. Prosser, 2004, "Changes
in lagoonal marsh morphology at selected northeastern Atlantic
Coast sites of significance to migratory waterbirds," Wetlands
24(4): 891-903.
17Kneib, R.T., 1997, "Tidal marshes offer a different perspective
on estuarine nekton," .• iminal Review of Oceanography and
Marine Biology 35:1-120.
1?LaBranche, I, M. McCoy, and D. Clearwater, 2003, p. 17 in
Maryland State Wetland Conservation Plan, prepared by
Nontidal Wetlands and Waterways Division, Maryland
Department of the Environment.
19Kreamer, G.R., 1995, Saltmarsh invertebrate community, pp.
81-89 in Dove and Nyman, 1995 (see note 14).
20Dove and Nyman, 1995, pp. 81-89 (see note 14).
21Lippson and Lippson, 2006, pp. 202-203 (see note 2).
"Rountree, R.A., and K.W. Able, 1992, "Fauna of polyhaline
subtidal marsh creeks in southern New Jersey: Composition,
abundance and biomass,"Estuaries 15:171-185.
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[ 192 1 \ - - \ » ]
Characteristic macroinvertebrates of salt marsh
creeks include eastern mud snails, daggerblade
grass shrimp, longwrist hermit crabs, common
Atlantic slippershells, northern quahogs,
softshell clams, razor clams, blue crabs, and
horseshoe crabs. Great blue herons and egrets are
among the many colonial wading birds and other
waterbirds that commonly feed on the small fish
and benthic invertebrates found in tidal creeks. If
creeks deepen, these species will have increasing
difficulty foraging for essential food supplies.
High marsh is briefly flooded once or twice daily
on fewer than 10 days per month and is
dominated by salt hay and spike grass. High
marsh sediment contains more organic material
than low marsh.23'24 High marshes may include a
scrub-shrub community at the upland edge. Salt
shrubs often mark the limit of the highest spring
and storm tides. Characteristic shrubs include
groundsel, saltmarsh elder, and pasture rose. The
marsh edge is typically dominated by salt marsh
elder, whereas groundsel usually dominates the
upland edge. Grasses include those typical of
high salt marsh, including salt meadow grass,
black grass, and switchgrass. The invasive
common reed sometimes occurs in a narrow
fringe along the upland edge of marshes where
salinities are lower because of less tidal flooding
and greater freshwater runoff.
Characteristic birds of high salt marsh include
saltmarsh sharp-tailed sparrows, black rails, and
northern harriers. Many of these high marsh
species are adapted to nesting only in the short
grasses of the high marsh, such as salt hay and
spike grass, and may not thrive in the tall grasses
of the low marsh.
Brackish or estuarine tidal marshes in
estuaries of the mid-Atlantic are typically
dominated by species such as Olney three-
square, saltmarsh bulrush, switchgrass, dwarf
spike grass, black needlerush, narrow-leaved
cattail, big cordgrass, and the invasive common
reed. In mixed communities, the vegetation
occurs in zones. Big cordgrass is the most
23Brinson, M.M., R.R. Christian, and L.K. Blum, 1995, "Multiple
states in the sea level induced transition from terrestrial forest to
estuary," Estuaries 18(4): 648-659.
24LaBranche et al., 2003, p.17 (see note 18).
common near mean high tide (MHT), Olney
three-square at MHT, and switchgrass near the
spring tide line. Brackish marshes support many
of the same species as salt marshes, with some
notable exceptions. Bald eagles forage in
brackish marshes and nest in nearby wooded
areas. Because there are few resident mammalian
predators, small herbivores such as meadow vole
thrive in these marshes.25
Fish species common in the brackish waters of
the mid-Atlantic include striped bass and white
perch, which move in and out of brackish waters
year-round. Anadromous fishes, including
herring and shad, as well as marine transients
such as Atlantic menhaden and drum species, are
present in summer and fall. The most visible
invertebrates of the brackish marshes include
red-jointed fiddler crab, marsh periwinkle,
Atlantic ribbed mussel, and common clam
worm.26
Freshwater tidal marshes are characteristic of
the upper reaches of tributaries of estuaries. They
support a more diverse vegetation community
than more saline marshes. Like salt and brackish
marshes, freshwater tidal marshes can show three
distinct vegetation zones, depending on the
degree of tidal inundation. In general, the lower
tidal zone, exposed only at low tide, consists of
sparsely vegetated intertidal flats. The middle
zone is dominated by wild rice, spatterdock,
pickerelweed, and arrow arum. The upper tidal
zone is dominated by cattails, often with a
diversity of other species such as sensitive fern,
river bulrush, and sweet flag, and sometimes the
invasive common reed.27
In general, the species composition of freshwater
marshes does not appear to be limited by seed
availability. Instead, physical factors limit the
species composition, especially through
flooding. Some species germinate well when
25White, C.P., 1989, Chesapeake Bay: Nature of the Estuary, A
Field Guide, Tidewater Publishers, Centreville, MD, pp. 107-
123.
26White, 1989, p. 124 (see note 25).
27White, 1989, pp. 97-105 (see note 25).
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[ >N 3,1 193 ]
completely submerged; others are relatively
intolerant of flooding.28
Tidal freshwater marshes provide shelter, forage,
and spawning habitat for numerous fish species,
primarily cyprinids (minnow, shiner, carp);
centrarchids (sunfish, crappie, bass); and
ictalurids (catfish). Some estuarine fish and
shellfish can also complete their life cycle in
freshwater marshes.29
Freshwater tidal marshes are also important for a
wide range of bird species, and some ecologists
suggest that these marshes support the greatest
diversity of bird species of any marsh type,
including a variety of waterfowl; wading birds;
rails and shorebirds; birds of prey; gulls, terns,
kingfishers, and crows; arboreal birds; and
ground and shrub species.30 Perching birds such
as red-winged blackbirds are common in stands
of cattail. Tidal freshwater marshes support
additional species that are rare in saline and
brackish environments, such as frogs, turtles, and
snakes.31
In addition to food and shelter for various
species, marshes also improve water quality in
the surrounding river or estuary. The marshes
serve as filters for water draining from
surrounding upland areas. In particular, marshes
work to remove nutrients from runoff, process
chemical and organic wastes, and reduce the
terrigenous sediment load to the water column.32
Marsh processes remove nitrogen and
phosphorus compounds (e.g., nitrates, ammonia,
and phosphates) from the water stream. The
denitrification process (bacterial conversion of
ammonia or nitrates from organic wastes and
fertilizer into nitrogen gas) provides significant
benefits to water quality. High levels of nutrients
in coastal waters from nonpoint source runoff
lead to algal blooms and hypoxia, which can kill
large numbers of fish. Marsh vegetation also
retains much of the terrigenous sediment load
28Mitsch, W.J., and J.G. Gosselink, 2000, Wetlands, 3rd ed., Van
Nostrand Reinhold, New York, p. 275.
29Mitsch and Gosselink, 2000, p. 277 (see note 28).
30Mitsch and Gosselink, 2000, p. 279-280 (see note 28).
3'White, 1989, pp. 107-109 (see note 25).
32Tiner, R.W., andD.G. Burke, 1995, Wetlands of Maryland,
U.S. Fish and Wildlife Service, Region 5, Hadley, MA, pp. 146—
147.
from runoff, which can interfere with
photosynthesis in the water column (e.g., for
SAV) and can cause siltation in nearshore areas
(e.g., SAV or oyster beds).
Effects of Sea Level Rise on Tidal
Marshes
The ability of tidal marshes to migrate in
response to sea level rise depends on the supply
of sediment and organic matter that is available
to raise the marsh surface, the local tidal range,
and the slope of nearby lowland. In addition,
shoreline protection structures can block inland
migration. The placement of hard structures
reduces sediment inputs from upland sources and
increases erosion waterward of a structure.
Tidal marshes may keep pace with sea level rise
through vertical accretion and inland migration,
as long as there is a dependable source of
terrigenous sediment and the marsh can maintain
the same elevation relative to the tidal range. In
areas where neither sufficient accretion nor
migration can occur, increased tidal flooding can
stress marsh plants through waterlogging and
changes in soil chemistry, leading to a change in
species composition and vegetation zones. If
marsh plants become too stressed and die, the
marsh will eventually convert to open water or
mudflats (see Photo 3.2).33'34
Steadily increasing relative sea levels may cause
more frequent events such as saltwater flooding,
storm overwash, and wrack deposition. These
events, in turn, can trigger changes in wetland
ecosystems.35 The ability of marsh vegetation to
accrete terrigenous sediment and migrate inland
will determine marsh survival.36Marsh types,
33Callaway, J.C., J.A. Nyman, and R.D. DeLaune, 1996,
"Sediment accretion in coastal wetlands: A review and a
simulation model of processes," Current Topics in Wetland
Biogeochemistry 2:2-23.
34The Plum Tree Island National Wildlife Refuge is an example
of a marsh deteriorating through lack of sediment input and
migration capacity, due to development on its landward side.
Extensive mudflats front the marsh. See Section 3.11 on
Hampton Roads.
35Brinson et al., 1995, p. 655 (see note 23).
36Ward, L.G., M.S. Kearney, and J.C. Stevenson, 1998,
"Variations in sedimentary environments and accretionary
patterns in estuarine marshes undergoing rapid submergence,
Chesapeake Bay."Marine Geology 151:111-134.
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[ 194 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Photo 3.2: Fringing March and Bulkhead, Monmouth County, New
Jersey
however, have differing capacities for sediment
accretion. Facing increasing rates of sea level
rise, high marshes may not be able to trap and
accrete sufficient sediment, whereas low tidal
marshes, both fresh and estuarine, are more
likely to have this ability. Marshes without
riverine sediment input, such as those that fringe
islands, are at the greatest risk from sea level
rise.J / Sediment transport in low marsh areas is
facilitated by tidal creeks, which frequently
occur in networks throughout broad areas. These
networks are absent in more mature marshes and
in upland areas, limiting sediment input for high
marshes.38
If accretion does not maintain the marsh in place,
migration is also a possible mechanism for
marsh survival. In addition to artificial and
natural barriers (e.g., armoring structures),
sediment requirements also impede wetland
migration. Bare patches and a more mineral
sandy substrate are necessary for lower marsh
vegetation species to migrate onto areas that
once were high marsh. For successful transition,
a variety of factors, including
localized topographic
changes, erosion, deposition
of wrack on high marsh
plants, and ponding, can
contribute to deterioration of
the high marsh organic-rich
peat and allow for
colonization by low-marsh
Spar Una alterniflora39 S.
alterniflora can aggressively
colonize high marsh areas
that have been devegetated
by wrack deposition from a
storm or overwash event.
Even though S. alterniflora
can colonize deteriorated
high marsh areas with
suitable sediment types,
factors that reduce wetland
vegetation's ability to trap
sediments (e.g., construction of roads across
them or reductions in sediment supply) and the
processes that drive deterioration (described
previously) can continue even in the absence of
further sea level rise, resulting in total marsh
loss.4"
Local variation in rates of terrigenous
sedimentation and other processes such as
erosion will determine accretion and migration at
specific sites.41 In addition to anthropogenic or
natural physical barriers, storm-induced erosion
and sediment deficits can preclude migration. In
Chesapeake Bay, scientists estimate that "the
influx of particulates is not high enough to keep
pace with relative sea level rise" on a bay-wide
scale.42 A trend of decreasing sediment inputs
from major mid-Atlantic rivers because of
farmland abandonment in the mid-Atlantic
'Najjar et al., 2000, p. 223 (see note 4).
^Stevenson, J.C., and M.S. Kearney, 1996,
''Shoreline dynamics
on the windward and leeward shores of a large temperate
estuary," pp. 233-259 in Estuarine Shores: Evolution,
Environments, and Human Alterations, K.E, Nordstrom and C.T.
Roman (eds.), John Wiley & Sons, New York; and Najjar et al.,
2000, p. 223 (see note 4).
39Brinson et al., 1995, p. 655 (see note 23).
4flStevenson and Kearney, 1996, p. 238 (see note 38).
41Ward et al. (1998) (see note 36) found that accretion rates tend
to decrease down-estuary in the Nanticoke, an eastern Bay
tributary. Overall, rates in embayment marshes were close to or
less than the local sea level rise and not as spatially patterned as
the tributary marshes. A 0.24 cm/year accretion rate at the mouth
of an estuarine tributary (the Nanticoke) compared to a 0.19
cm/year accretion rate for an interior marsh area ("Variations in
sedimentary environments," p. 125). In Monie Bay, a low organic
content was found, indicating a higher level of mineral soils and
suggesting that accretion rates are lower than relative sea level
rise ("Variations in sedimentary environments," p. 127).
Stevenson and Kearney, 1996, p. 236 (see note 38).
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[ >N 3,1 195 ]
region suggests that a lack of sediment may also
affect wetlands outside of Chesapeake Bay.43
Similarly, lagoonal marshes, areas within
embayments or larger marsh systems, and
marshes migrating inland that are remote from
tributary sediment inputs may not be able to keep
pace with sea level rise.44 In areas without
sufficient sediment, wetlands may transition to
tidal flat or open water.
Vegetation type can also affect the ability of a
marsh to accrete sediment. Greater rates of
mineral and organic sediment trapping have been
associated with common reed (as compared to
Spartina spp.) in both a subsiding creek bank
marsh and a laterally eroding marsh.45
Researchers indicate that belowground
productivity most likely plays a key role in the
ability of the common reed to rapidly increase
substrate level.46 Given the greater ability of
marshes dominated by common reed to meet
increased rates of sea level rise, expected
ecological effects are lower in these areas.47
Effects of Armoring on Tidal Marshes
Shoreline protection can affect both migration
and accretion for wetlands. Increases in wave
energy generated by armoring structures can
eliminate marsh areas waterward of the
structures.48 Sediment scoured from bulkhead
bases in estuaries can "cover spawning habitats
formerly used by forage fish that spawn in the
upper intertidal zone."49 Marsh and tidal areas
43Najjar et al., 2000, p. 223 (see note 4).
44Erwin et al., 2004, p. 892 (see note 16).
45Rooth, J.E. and J.C. Stevenson, 2000, "Sediment deposition
patterns in Phragmites australis communities: Implications for
coastal areas threatened by rising sea-level," Wetlands Ecology
and Management 8:173-183.
46Ibid.
47At Eastern Neck National Wildlife Refuge, Maryland,
managers are leaving phragmites stands in place as a strategic
action against erosion. See Section 3.17, Chesapeake Bay's
Upper Bay, of this section.
48U.S. Geological Survey (USGS), 2003, "A summary report of
sediment processes in Chesapeake Bay and watershed," p. 55 in
Water-Resources Investigations Report 03-4123, USGS, Reston,
VA.
49Small, D., and R. Carman, 2005, "Marine shoreline armoring in
Puget Sound and the Washington State Hydraulic Code," p. 1 in
Proceedings of the 2005 Puget Sound Georgia Basin Research
Conference, March 29-31, 2005. Available at:
http://www.engr.washington.edu/epp/psgb/2005psgb/2005procee
dings/index.html from the University of Washington, College of
Engineering.
reinforced with armoring that prevents habitat
migration will suffer the greatest loss of
habitat.50'51 Elimination of these wetland areas
will also reduce the shoreline's ability to buffer
the effects of erosion and floods and to filter
nutrient and contaminant loads in runoff.
Ecological Effects on Tidal Marshes
Where tidal wetlands are lost, the myriad species
that depend on marshes—birds, fish,
invertebrates, amphibians, reptiles, and
mammals—can show decreased growth,
reproduction, or survival resulting from a
decrease in habitat quantity or quality. If salt
marsh areas are lost, avian marsh-nesting
obligates such as Forster's terns, black rails,
clapper rails, northern harriers, American black
ducks, seaside sparrows, and sharp-tailed
sparrows will lose habitat and are likely to suffer
reproductive stress.52 Lagoonal marshes and mid-
embayment areas are particularly susceptible to
changes induced by sea level rise. Tidal flats will
be inundated, and although changes in extent
might be localized at first, scientists anticipate an
overall reduction in forage habitat for shorebirds.
Sea level rise is also advancing the salinity
gradient upstream in some rivers, leading to
shifts in vegetation composition and the
conversion of some tidal freshwater marshes into
oligohaline marshes.53 High brackish marshes
can deteriorate as a result of ponding and wrack-
smothering of vegetation as salinity increases
with rising seas and storms accentuate the
fragmentation of the marshes.54 This process may
allow colonization by lower marsh species, but
50Galbraith, H., R. Jones, P. Park, J. Clough, S. Herrod-Julius, B.
Harrington, and G. Page, 2002, "Global climate change and sea
level rise: Potential losses of intertidal habitat for shorebirds,
Waterbirds 25(2): 173—183.
51Oyster Bay, New York, has experienced extensive marsh loss
as a result of bulkheading. See Section 3.3, Long Island South
Shore.
52For example, seaside and sharp-tailed sparrows are both
prevalent in at-risk marshes on Virginia's Eastern Shore. See
Section 3.19.
"Maryland Department of Natural Resources (DNR), 2005,
Chapter 4, Part 2, p. 49 in Wildlife Diversity Conservation Plan—
Final Draft, available at:
http://www.dnr.state.md.us/wildlife/divplan_wdcp.asp (accessed
February 28, 2007).
54Along the Patuxent River, Maryland, refuge managers have
noted marsh deterioration and ponding with sea level rise. See
Section 3.16 on the Western Shore.
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[ 196 ' ' i ]
that outcome is not certain.55 Low brackish
marshes may change dynamically in area and
composition as sea level rises. If they are lost,
forage fish and invertebrates of the low marsh—
such as fiddler crabs, grass shrimp, and ribbed
mussels—will no longer be available to the
predators that consume them. Even though more
ponding and "pannes" might provide some
additional foraging areas as marshes deteriorate,
the associated increase in salinity due to
evaporative loss will drive vegetation changes to
less diverse assemblages of salt-tolerant
species.56 In fact, high salt conditions will be
lethal for many species.
If marshes can migrate, changes in vegetation
assemblages will in turn affect the faunal species
that forage, nest, spawn, and seek shelter in tidal
marshes. Factors affecting fauna include reduced
available oxygen, structural changes in
vegetation, and reduction of foraging areas in
tidal flats. In these hypoxic conditions, more
salt-tolerant fishes such as mummichogs and
killifishes become prevalent.57
In areas where marshes are reduced, remnant
marshes might provide lower quality habitat and
pose greater predation risk for a number of bird
species that are marsh specialists and are also
important components of marsh food webs.
These species include the clapper rail, black rail,
least bittern, Forster's tern, willet, and laughing
gull.58 Scientists estimate that as much as 80
percent of the Atlantic Coast breeding population
of Forster's tern and 70 percent of laughing gull
are at risk because of habitat loss due to sea level
rise.59 Populations of some noncolonial species
are also at risk because of their already-low
population sizes, estimated at about 142,000 for
the clapper rail, 102,000 for the willet, and as
little as 13,000
55Stevenson and Kearney, 1996, p. 236 (see note 38).
56Maryland DNR, 2005, p. 49 (see note 53).
57Stevenson et al., 2002, pp. 25-26 (see note 7).
58Erwin, R.M., G.M. Sanders, D.J. Prosser, and D.R. Cahoon,
2006, "High tides and rising seas: potential effects on estuarine
waterbirds," pp. 214-228 in Terrestrial Vertebrates of Tidal
Marshes: Evolution, Ecology, and Conservation (R. Greenberg,
J. Maldonado, S. Droege, andM.V. McDonald, eds.). Studies in
Avian Biology No. 32, Cooper Ornithological Society.
59Ibid.
to 14,000 for the American black duck.60 The
number of bird species in Virginia marshes was
found to be directly related to marsh size; the
minimum marsh size found to support significant
marsh bird communities ranged from 4.1 to 6.7
ha.61 Particular species may require even larger
marsh sizes; minimum marsh sizes for successful
communities of the saltmarsh sharp-tailed
sparrow and the seaside sparrow, both on the
Partners in Flight WatchList, are estimated at 10
and 67 ha, respectively.62
Effects of marsh inundation on fish and shellfish
species are likely to be complex. In the short
term, inundation could make the marsh surface
more accessible, increasing production.
The benefits, however, will decrease as
submergence decreases total marsh habitat.63 A
marsh loss model, coupled with shrimp survey
data from the National Marine Fisheries Service,
suggests that losses in yields due to marsh loss
could be as high as 50 percent.64
Deterioration and mobilization of marsh peat
sediments increase the biological oxygen
demand in the immediate vicinity and deplete
oxygen levels to below requirement thresholds
for many game fish such as striped bass. In these
hypoxic conditions, more tolerant fish
assemblages including mummichogs and
killifish, become prevalent.65
60Ibid.
61Watts, B.D., 1993, Effects of Marsh Size on Incidence Rates
and Avian Community Organization within the Lower
Chesapeake Bay, Center for Conservation Biology Technical
Report CCBTR-93-03, The College of William and Mary,
Williamsburg, VA, 53 pp.
62Benoit, L.K., and R.A. Askins, 2002, "Relationship between
habitat area and the distribution of tidal marsh birds," The Wilson
Bulletin 114(3):314—323.
63Rozas, L.P., and D.J. Reed, 1993, "Nekton use of marsh-surface
habitats in Louisiana (USA) deltaic salt marshes undergoing
submergence," Marine Ecology Progress Series 96:147-157.
64Zimmerman, R.J., 1992, "Global warming: effects of sea level
rise on shrimp fisheries," pp. 58-73 in Proceedings of the
Southeast Fisheries Science Center Shrimp Resource Review,
K.N. Baxter and L. Scott-Denton (eds.), NOAA Technical
Memorandum, NMFS-SESC-299.
65Stevenson et al., 2002, pp. 25-26 (see note 7).
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[ >N 3,1 19? ]
3.1.2 FRESHWATER SWAMP FORESTS
Limited by their requirements for low salinity
water and high sediment inputs, tidal swamp
forests occur primarily in the upper regions of
tidal tributaries in Virginia, Maryland, Delaware,
New Jersey, and New York.66 Tidal hardwood
swamps occur in all of Virginia's major eastern
rivers, and are particularly pristine in the
Pamunkey and Mattaponi rivers. In these rivers,
pumpkin ash and swamp tupelo are the primary
overstory species. In the Potomac River and
farther north, green ash replaces pumpkin ash as
the dominant species.67 Parts of the Pocomoke
River tidal floodplain forests are dominated by
bald cypress. At the upland edges of tidal river
floodplains, loblolly pine, sweetgum, and oaks
can be present.68 Farther north (into New Jersey
and New York), varying tree species are present,
and the habitat is classified as northern Atlantic
coastal plain tidal swamp.69 North Carolina
contains large stands of forested wetlands,
particularly cypress swamps, as discussed in the
review of ecological impacts in North Carolina
(see, for example, Photo 3.3b).70
Throughout the forested swamps, "hummock-
and-hollow microtopography" dictates where
trees can establish themselves on small elevated
areas above the highest tide levels.71 A species-
rich herb vegetation layer includes a variety of
66NatureServe, 2006, "NatureServe Explorer: An online
encyclopedia of life" [Web application], Version 5.0,
NatureServe, Arlington, Virginia, available at:
http://www.natureserve.org/explorer, accessed September 1,
2006, and "Northern Atlantic coastal plain tidal swamp,"
CES203.282, accessed on September 1, 2006 at:
http: //www. natureserve. org / explorer/servlet/NatureServe? searchS
ystemUid=ELEMENT_GLOBAL.2.723205.
67Fleming, G.P., P.P. Coulling, K.D. Patterson, and K. Taverna,
2006, "The natural communities of Virginia: Classification of
ecological community groups. Second approximation. Version
2.2," Virginia Department of Conservation and Recreation,
Division of Natural Heritage, Richmond, VA, available at:
http://www.dcr.virginia.gov/dnh/ncintro.htm, accessed June 19,
2007.
68Maryland DNR, 2005, Wildlife Diversity Conservation Plan, p.
1 (see note 53).
69Westervelt, K., E. Largay, R. Coxe, W. McAvoy, S. Perles, G.
Podniesinski, L. Sneddon, and K. Strakosch Walz, 2006, A Guide
to the Natural Communities of the Delaware Estuary: Version 1,
NatureServe, Arlington, VA, pp. 270-273.
70Mark Brinson of East Carolina University is providing CCSP
and USGS with an analysis of these wetlands. We hope to work
with him to fully reflect these important wetlands.
71Fleming et al., 2006 (see note 67).
species such as jewelweed, arrow arum, and
sedges in the regularly flooded areas; marsh blue
violet, water hemlock, greenfruit clearweed,
false nettle, and ferns are found on the
hummocks (vegetated mounds that rise above the
adjacent wetland area).72 Tidal swamps support a
variety of wildlife, including the prothonotary
warbler, the two-toed amphiuma salamander, and
the bald eagle. Forested wetlands with thick
understories provide shelter and food for an
abundance of breeding songbirds.73 Various rare
and greatest conservation need (GCN) species
reside in tidal swamps, including the Delmarva
fox squirrel (federally listed as endangered), the
eastern red bat, bobcats, bog turtles, and the red-
bellied watersnake.74
Effects of Sea Level Rise on Tidal
Freshwater Swamp Forests
Tidal freshwater swamp forests are considered
globally uncommon to rare, and face a variety of
threats, including sea level rise. According to
Fleming and colleagues, "Crown dieback and
tree mortality are visible and nearly ubiquitous
phenomena in these communities and are
generally attributed to sea level rise and an
upstream shift in the salinity gradient in
estuarine rivers" (see also Photo 3.3a).75
Ecologists in Virginia note that where tree death
is present, the topography is limiting inland
migration of the hardwood swamp and the
understory is being infilled with marsh species
such as Spar Una.71
Ecological Effects on Tidal Freshwater
Swamp Forests
This pattern of crown dieback and marsh species
migration is likely to continue with sea level rise
acceleration. Salinity may increase as areas are
inundated, eliminating vegetation that relies on
the diluting effect of freshwater inputs. Loss of
72Maryland DNR, 2005, p. 1 (see note 53).
73Lippson and Lippson, 2006, p. 218 (see note 2).
74Maryland DNR, 2005, p. 4 (see note 53).
75Fleming et al., 2006 (see note 67).
76Written communication, Gary Fleming, vegetation ecologist,
Virginia Department of Conservation and Recreation, Division of
Natural Eleritage. Via email to Christina Bosch, Industrial
Economics, September 11, 2006. Subject: Re: Sea level rise
report wrap-up - please respond.
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[ 198 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
tidal swamp forests would
detrimentally affect the varied
fauna that reside there.
3.1.3 MARSH AND BAY
ISLANDS
Islands are common features
of salt marshes, and some
estuaries and back barrier
bays have islands formed by
deposits of dredge spoil.
Many islands are a mix of
habitat types, with vegetated
and unvegetated wetlands in
combination with upland
areas.77 Shorelines can be
composed of marsh or rocky
or sandy beaches. These
islands are important habitats
for birds because they provide
protection from terrestrial
predators such as the red fox.
Birds such as gull-billed
terns, common terns, black
skimmers, and American
oystercatchers nest on marsh
islands. '8 Many islands
provide secluded areas for
important bird colonies (e.g.,
the colonies of the rare black-
crowned night heron on North
and South Brother i slands in
New York; see Section 3.2 on
Long Island Sound). Salt
marsh islands in the New
Jersey back-barrier bays are
feeding and/or nesting sites
for a variety of birds and
turtles, including several
^Thompson's Island in Rehoboth Bay, Delaware, is a good
example of a mature forested upland with substantial marsh and
beach area. The island hosts a large population of migratory
birds. See Section 3.8 of this section.
78Rounds, R.A., R.M. Erwin, and J.H. Porter, 2004, '"Nest-site
selection and hatching success of waterbirds in coastal Virginia:
Some results of habitat manipulation," Journal of Field
Ornithology 75:317-329; Eyler, T.B., R.M. Erwin, D.B. Stotts,
and J.S. Hatfield, 1999, "Aspects of hatching success and chick
survival in gull-billed terns in coastal Virginia," Waterbirds
22:54-59; and Lauro, B., and J Burger, 1989, "Nest-site
selection of American oystercatchers (Haematopus pa Hiatus) in
salt marshes," Auk 106:185-192.
Photo 3.3a: Inundation and tree mortality in tidal freshwater swamp
at Swan's Point, Lower Potomac River
Photo 3.3b. Cypress along Roanoke River, North Carolina
species of tern, oystercatchers, plovers, and
diamondback terrapins (see Section 3.6 on New
Jersey Shore). Artificially enhanced islands,
generally created through dredge spoil, can
provide similar benefits (e.g., Hart-Miller Island
near Baltimore, Maryland); however, dredge
spoil islands can be particularly susceptible to
erosion (see Section 3.16, Chesapeake Bay's
Western Shore, and discussion of Poplar Island
in Section 3.18, Chesapeake Bay's Central
Eastern Shore). Hummocks can also be
considered a type of island (see Photo 3.4).
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[ SECTION 3.1 199 ]
Barrier islands form where
sand accumulates along
sandy coasts with small or
medium tide ranges and
wide continental shelves.7''
They contain many fragile
habitats such as sand
dunes, maritime forests,
and back-barrier marshes
that provide critical habitat
for many coastal species.
Barrier islands are a
common feature of the
U.S. Atlantic Coast.
Effects of Sea Level
Rise on Islands
Depending on their current
elevations, sediment
supply, and rates of
erosion, wetland islands could become the first
habitats to be eliminated as a result of sea level
rise. Sea level rise poses a unique threat to
islands, in that migration is not an option and
sediment inputs may be limited. Some scientists
believe that salt marsh islands in large coastal
lagoons will be more vulnerable to inundation as
sea level rises than fringing marshes because the
lagoons lack inorganic sediments.8" In some
cases, rising sea level may cause additional
islands to form, as portions of peninsulas erode
and higher water levels separate high ground
from the mainland. Many islands along the mid-
Atlantic Coast, and particularly in Chesapeake
Bay, have been lost or severely degraded
because of sea level rise. Although armoring can
be used to protect these islands, it is not
generally employed because the islands are
undeveloped.
Without human interference, barrier islands often
maintain a state of dynamic equilibrium between
sediment exchange, wave energy, and sea level,
migrating inland through a process often called
"overwash" or "barrier island rollover." Under
some circumstances, however, rising sea level
can increase the frequency of inlets, and under
extreme circumstances, sea level rise can cause
the islands to disintegrate or reform several
kilometers inland. The relatively slow rise in sea
level during the last several centuries has enabled
many barrier islands to widen far beyond their
critical width; it follows that accelerated sea
level rise would tend to cause most barrier
islands to narrow.
Ecological Effects on Islands
For island-nesting bird species, the loss of
wetland islands to flooding and erosion is a
serious problem. A shift to mainland marshes is
generally not an option for these species because
of predators present in those marshes. Numerous
species of special concern, including the piping
plover, nest in the protected back-dune areas of
barri er islands. Loss of these habitats could have
a serious effect on such rare species. To the
extent that estuarine and riverine beaches,
particularly on islands, survive better than barrier
islands, shorebirds like oystercatchers might be
able to migrate to these shores.81
The information presented here on barrier islands is very
limited because CCSP4.1 has at least two nationally recognized
barrier-island experts from USGS; hence this background report
is unlikely to be used for the CCSP discussions of barrier islands.
s0Erwin et al., 2004, pp. 891-903 (see note 16).
slMcGowan, C.P., T-R- Simons, W. Golder, and J. Cordes, 2005,
"A comparison of American oystercatcher reproductive success
on barrier beach and river island habitats in coastal North
Carolina,'' Waterbirds 28:150-155.
Photo 3.4: Marsh Drowning and Hummock in Blackwater Wildlife
Refuge, Maryland
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[ 200 1 i ]
3.1.4 SEA LEVEL FENS
The mid-Atlantic region contains a few areas of
the globally rare sea level fen habitat. These fens
are unique combinations of plant species, present
in Delaware's Sussex County Inland Bays
watershed, on Long Island's South Shore, and on
the eastern shore of Virginia's Accomack
County.82 Sea level fens generally occur just
above the upper high tide mark, at the bases of
slopes.83 Groundwater seepage from the slopes
provides sea level fens with nutrient-poor fresh
water. The fens occur only where they are
protected from nutrient-rich tidal flow by a
barrier such as a fronting tidal marsh.
The nutrient-poor environment and acidic soils
support a unique mix of vegetation species,
including both freshwater tidal species and
northern bog species, in sea level fens.84 Red
maple, blackgum, sweetbay, and southern
bayberry form the overstory; the herb layer
typically includes twig rushes, beaked
spikerushes, and beakrushes. Carnivorous plants,
including sundew and bladderworts, are also
present.85 The eastern mud turtle and the smallest
northeastern dragonfly (Nanothemis bella) are
two faunal species known to occur in the fens.86
The animal and plant species listed here are not
exclusive to sea level fens, but many are rare
species.
Effect of Sea Level Rise on Sea Level
Fens
Because these fens are located at the bases of
slopes, they are likely to be inundated by sea
level rise. The Virginia Natural Heritage
Program identifies sea level rise as a primary
threat to sea level fens because of the increase in
82For additional discussion, see Sections 3.8, Maryland and
Delaware Coastal Bays; 3.3, Long Island's South Shore; and
3.19, Virginia's Eastern Shore.
83Virginia Natural Heritage Program, Virginia Department of
Conservation and Recreation. Natural Heritage Resources Fact
Sheet: Virginia's rare natural environments: Sea-level fens.
Accessed on July 17,2007 at:
http://www.dcr.virginia.gOv/natural_heritage/documents/fsslfen.p
df.
84Ibid.
85Fleming et al., 2006 (see note 67).
86Virginia Natural Heritage Program (see note 83).
salinity and nutrient-rich water inputs.87 The
location of fens below slopes limits the
possibility for migration. During the
development of this report, no studies of the
effects of armoring on sea level fens were
identified.
Ecological Effects on Sea Level Fens
The unique vegetation assemblages and little-
studied animal communities of sea level fens are
likely to be eliminated by sea level rise. The
plant assemblages are unique, but the animal
species identified are present in other habitats.
The habitat is likely to convert to more usual
tidal marsh vegetation and faunal assemblages
following the increased incursion of higher
salinity waters. However, given the slopes at the
landward edges of the fens, migration will be
restricted and survival of any marsh areas will
depend on accretion rates.
3.1.5 NEARSHORE WATERS AND
SUBMERGED AQUATIC VEGETATION
(SAV)
Nearshore shallow water habitats perform a
variety of roles in the aquatic ecosystem. Key
ecological features of the nearshore shallow
water habitat include SAV, oyster reefs, and
nektonic (e.g., fish and decapod crustaceans) and
planktonic inhabitants. In areas without SAV or
oyster reefs, muddy and sandy substrates similar
to those found on tidal flats are present.88 Oyster
reefs are a key resource in intertidal and
nearshore waters; however, they are not
addressed in detail here because many factors
currently affect their success. Over harvest,
nutrient levels, and disease have all significantly
affected oyster reefs.. Changes related to sea
level rise may additionally affect the resource.
For example, if salinity were to increase, oysters
might be able to successfully colonize farther up
estuaries, but in their current areas they would
suffer greater losses from predators and disease.
These possibilities, though, are difficult to
estimate in the presence of annual variability.
This section therefore focuses on SAV, which
provides a wide array of ecological services and
87Fleming et al., 2006 (see note 67).
88Lippson and Lippson, 2006, pp. 126-127 (see note 2).
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[ >N 3,1 201 ]
is very sensitive to water depth and substrate.
SAV includes submerged, vascular rooted plants
found in the subtidal and, occasionally, in the
intertidal zone.89 SAV can occur as isolated
patches or form extensive beds. Aquatic
vegetation is distributed throughout the mid-
Atlantic region, dominated by eelgrass in the
higher salinity areas and a large number of
brackish and freshwater species elsewhere (e.g.,
widgeon grass and sea lettuce). During low tides,
SAV can be exposed on estuarine beaches and
tidal flats.90
Nearshore vegetation plays a strong role in
estuarine and bay ecology, regulating dissolved
oxygen, reducing suspended sediments and
nutrients, stabilizing bottom sediments, and
reducing wave energy.91 SAV communities
regulate the production, uptake, and storage of
nitrogen, carbon, and oxygen in the ecosystem.92
Optimum growing conditions for SAV are highly
dependent on light levels for photosynthesis.
Various interferences—such as increased
turbidity, epiphyte growth on leaves, and
increased water depth—can decrease the light
available to the plants for photosynthesis. Plants
at either end of the growing zone are stressed by
overexposure or sunlight limits. Nutrient runoff
(which boosts algal growth that shades the SAV)
as well as boating and mollusk dredging (which
cause physical disturbance to the beds) can all
have detrimental effects on SAV.93
89Hurley, L.M., 1990, Field Guide to the Submerged Aquatic
Vegetation of Chesapeake Bay, U.S. Fish and Wildlife Service,
Chesapeake Bay Estuary Program, Annapolis, MD, 48 pp.
9"Maryland DNR, 2005, pp. 22-23 (see note 53).
91Short, F.T., and H.A. Neckles, 1999, "The effects of global
climate change on seagrasses."AquaticBotany 63(1999): 169—
196.
92Buzzelli, C.P., 1998, "Dynamic simulation of littoral zone
habitats in lower Chesapeake Bay. I. Ecosystem characterization
related to model development," Estuaries 21(48):659-672;
Buzzelli, C.P., R.L. Wetzel, andM.B. Meyers, 1998, "Dynamic
simulation of littoral zone habitats in lower Chesapeake Bay. II.
Seagrass habitat primary production and water quality
relationships," Estuaries 21(48):673-689.
93Orth, R.J., J.R. Fishman, A. Tillman, S. Everett, and K.A.
Moore, 2001, Boat Scarring Effects on Submerged Aquatic
Vegetation in Virginia (Year 1), Final Report to the Virginia
Saltwater Recreational Fishing Development Fund; Moore, K.A.,
and R.J. Orth. 1997, Evidence of Wide spread Destruction of
Submersed Aquatic Vegetation (SAV) from Clam Dredging in
Chincoteague Bay, Virginia, Report to the Virginia Marine
Resources Commission. Both reports are available from VIMS
at: http://www.vims.edu/bio/sav/savreports.html (Accessed
October 16, 2007).
Except for a high predominance of sea lettuce in
New York's Jamaica Bay and the subtidal
reaches stretching from Little Egg Harbor south
to Cape May in New Jersey, the more northerly
SAV beds are largely eelgrass. Research in New
Jersey's coastal bays found a reduced habitat
quality of SAV in areas dominated by sea
lettuce.94
Seagrasses (e.g., eelgrass and widgeon grass)
provide food and shelter for a variety of fish and
shellfish, food for the species that prey on them,
and physical protection from wave energy for
shorelines. Organisms that forage in seagrass
beds feed on the plants themselves, on the
detritus and the epiphytes on plant leaves, or on
the small organisms found within the SAV bed.95
Invertebrates that are common in eelgrass
meadows include polychaetes such as the
common clam worm; mollusks such as bay
scallop and northern quahog; crustaceans such as
blue crabs, hermit crabs, and mud crabs; and
amphipods such as Lysianopsis alba and the
small, shrimp-like Ampelisca abdita. The
commercially valuable blue crab hides in
eelgrass during its molting periods, when it is
more vulnerable to predation. Blue crabs in the
postlarval phase (megalopae) preferentially
inhabit eelgrass beds.96
These invertebrates are in turn consumed by fish
and other predators.97'98 In Chesapeake Bay,
summering sea turtles frequent eelgrass beds.
The endangered Kemp's Ridley sea turtle
forages in eelgrass beds and flats, feeding on
94Sogard, S.M., and K.W. Able, 1991, "A comparison of eelgrass,
sea lettuce macroalgae, and marsh creeks as habitats for
epibenthic fishes and decapods," Estuarine, Coastal and Shelf
Science 33:501-519.
95For blue crabs, see Stockhausen, W.T., and R.N. Lipcius, 2003,
"Simulated effects of seagrass loss and restoration on settlement
and recruitment of blue crab postlarvae and juveniles in the York
River, Chesapeake Bay "Bulletin of Marine Science 72(2):409-
422. For fish, see Wyda, J.C., L,A. Deegan, J.E. Hughes, and
M.J. Weaver, 2002, "The response of fishes to submerged aquatic
vegetation complexity in two ecoregions of the mid-Atlantic
Bight: Buzzards Bay and Chesapeake Bay," Estuaries 25:86-
100.
96van Montfrans, J., C.H. Ryer, and R.J. Orth, 2003, "Substrate
selection by blue crab Callinectes sapidus megalopae and first
juvenile instars," Marine Ecology Progress Series 260:209-217.
97USEPA, 1982, Chesapeake Bay: Introduction to an Ecosystem,
USEPA, Washington, DC,, 33 pp.
98Lippson and Lippson, 2006, p. 181 (see note 2).
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[ 202 1 \ - - \ » ]
blue crabs in particular." Various water birds
feed on SAV, including brant, canvas back duck,
and American black duck, which is a U.S. Fish
and Wildlife Service species of concern.100
Forage for piscivorous birds and fish is provided
by a number of small fishes that are residents of
nearby marshes and move in and out of seagrass
beds with the tides, including mummichog,
Atlantic silverside, naked goby, northern
pipefish, and threespine and fourspine
sticklebacks. Juveniles of many commercially
and recreationally important estuarine and
marine fishes (including menhaden, herring,
shad, spot, croaker, weakfish, red drum, striped
bass, and white perch) and smaller adult fish
(such as bay and striped anchovies) use SAV
beds as nurseries that provide both food and
protection from predators.101 Adults of estuarine
and marine species such as sea trout, bluefish,
perch, pickerel, and drum search for prey in the
SAV beds.
Effect of Sea Level Rise on Nearshore
Waters and SAV
Sea level rise may harm seagrass beds through
inundation, increased turbidity, and saltwater
intrusion.102 In subtidal areas, rising sea levels
and deepening waters will shade seagrass and
limit photosynthesis. Extensive armoring
coupled with areas of limited natural migration
could significantly decrease seagrass abundance.
Although plants in some portion of a seagrass
bed could decline as a result of such factors,
landward edges may migrate inland depending
on shoreline slope and substrate suitability. The
extent of ecological effects is uncertain because
most changes in seagrass beds occur on a
"Chesapeake Bay Program sea turtles guide, 2003, available at:
http://www.chesapeakebay.net/seaturtle.htm, accessed February
27,2007.
100Perry, M.C. and A.S. Deller, 1996, "Review of factors
affecting the distribution and abundance of waterfowl in shallow-
water habitats of Chesapeake Bay," Estuaries 19:272-278.
101NOAA Chesapeake Bay Office, 2007, "Underwater grasses
and submerged aquatic vegetation," accessed June 19, 2007 at:
http://noaa.chesapeakebay.net/HabitatSav.aspx; Wyda et al.,
2002, pp. 86-100 (see note 95).
102Short andNeckles, 1999, pp. 169-196 (see note 91).
significantly shorter time scale than can be
attributed to sea level rise.103
Under optimal conditions, seagrasses could
migrate into deteriorating marshes. For example,
populations of widgeon grass were observed in
marsh potholes that developed as canals formed
through organic marsh deposits.104 Kentula and
Mclntire documented eelgrass expansion into a
basin created by sand deposition.105 Preliminary
studies of eelgrass in marsh areas being
inundated by relative sea level rise have,
however, shown that the sediment composition
of the low marsh areas may not be suitable for
eelgrass colonization. In areas where inundation
exposed underlying sand, eelgrass beds extended
into the areas, but areas of exposed peat were not
colonized. The difficulty in colonization was tied
to the impermeability of the substrate
(prohibiting seed settlement and germination)
and the high levels of nutrients in the sediment,
particularly nitrogen. These factors changed the
morphology of the eelgrass, making it less suited
to the energy level of its environment.106 Unlike
most wetland plants, seagrasses generally require
a low organic content for optimal growth.107
When tidal marshes, which have a high organic
content, are submerged, SAV such as Ruppia
maritima can have difficulty revegetating the
substrate. SAV grows significantly better in
areas where erosion provides sandy substrates
rather than fine-grained or high-organic-matter
substrates.108
103USFWS Chesapeake Bay Field Office, n.d., "Nutrient
pollution," accessed on July 20, 2006 at:
http://www.fws.gov/chesapeakebay/nutrient.htm.
104Christian, R.R., 1981, referenced in Brinson et al. 1995, p. 654
(see note 23).
105Kentula, M.E., and C.D. Mclntire, 1986, "The autecology and
production dynamics of eelgrass (L. Zostera marina) in Netarts
Bay, Oregon,"Estuaries 9(3): 188-193.
106Wicks, E.C., 2005, The Effect of Sea Level Rise on Sea
Grasses: Is Sediment Adjacent to Retreating Marshes Suitable for
Seagrass Growth? Thesis, Marine, Estuarine, and Environmental
Science Program, University of Maryland, College Park; and
preliminary research by Koch.
107Kemp, W.M., R. Batuik, R. Bartleson, P. Bergstrom, V. Carter,
G. Gallegos, W. Elunley, L. Karrh, E. Koch, J. Landwehr, K.
Moore, L. Murray, M. Naylor, N. Rybicki, J.C. Stevenson, and
D. Wilcox, 2004, "Elabitat requirements for submerged aquatic
vegetation in Chesapeake Bay: Water quality, light regime, and
physical-chemical factors," Estuaries 27:363-377.
108Stevenson et al. 2002, pp. 26, 32 (see note 7).
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[ >N 3,1 203 ]
The effect of sea level rise on the tidal range will
also have an impact on seagrass, although it may
be detrimental or beneficial. In areas where the
tidal range increases, plants at the lower edge of
the bed will receive less light at high tide, which
will increase plant stress.109 In areas where the
tidal range decreases, the decrease in intertidal
exposure at low tide on the upper edge of the bed
will reduce plant stress.110
Effects of Armoring on Nearshore Waters
and SAV
Areas of shoreline armoring are likely to
experience the biggest losses of seagrass.
Movement of seagrass beds shoreward will be
impeded by shoreline construction and armoring
in developed areas.111 Where inland migration is
not possible, seagrass will decline or be
eliminated as a result of inundation and increased
salinity as seas rise. Nearshore fishes have been
found to be significantly less abundant at
bulkheaded sites, in part because seagrass is not
present.112 Bulkheads and other hard structures
tend to affect the geomorphology of their
locations as well as any adjacent seagrass
habitats. Particularly during storm events, wave
reflection off of revetments can increase water
depth and magnify swash runup on downcoast
beaches.113 AUSGS sedimentation study notes
that these structures tend to increase erosion at
their bases by reflecting wave energy across the
nearshore bottom.114 Similarly, a study of
armoring in estuaries found that "wave energy
reflected from bulkheads causes an increase in
turbulence and erosional energy waterward of
the structure that can result in substrate
coarsening and lowering of the beach profile."115
These physical changes in turn affect the
habitats.
109Koch and Beer, 1996, referenced in Short and Neckles, 1999,
p. 179 (see note 91).
110Short and Neckles, 1999, pp. 179-180 (see note 91).
1 "Short and Neckles, 1999, p. 178 (see note 91).
112Byrne, D.M., 1995, "The effect of bulkheads on estuarine
fauna: a comparison of littoral fish and macroinvertebrate
assemblages at bulkheaded and non-bulkheaded shorelines in a
Barnegat Bay Lagoon," Second Annual Marine Estuarine
Shallow Water Science and Management Conference: 53-56.
113Plant, N.G. and G.B. Griggs, 1992, "Interactions between
nearshore processes and beach morphology near a seawall."
Journal of Coastal Research 8: 183-200, p. 190.
114USGS, 2003, p. 50 (see note 48).
115Small and Carman, 2005, p. 1 (see note 49).
As sea level rises in armored areas, accompanied
by erosional energy at the bottom, the nearshore
area deepens with no ability to migrate. In
addition to the effects of increased reflectional
wave energy, which can be dissipated to a large
degree by healthy seagrass communities, light
attenuation increases with the deepening water,
restricting and finally eliminating seagrass
growth. Optimum growing conditions for most
SAV require light levels typically found at up to
1 to 2 meters in depth, generally starting below
the mean lower low watermark.116 Light
reductions from water clarity and epiphyte
growth in most SAV beds are now at 1 meter or
less in depth.117
In addition to the effects of light quantity and
turbulence, high nutrient levels in the water are
also a limiting factor. Despite the protection
from wave energy provided in their interior,
breakwaters appear to be detrimental to seagrass
in the long term. Sediment trapping behind the
breakwater, which increases the organic content,
can limit eelgrass success. Low-profile armoring,
including stone sills and other "living shoreline"
projects, have a more limited impact on seagrass
growth.118 New designs for seagrass-friendly
breakwaters that allow rollover at high tide might
serve to flush out the interior of the breakwater
and eliminate excess nutrient buildup.119
Ecological Effects on Nearshore Waters
and SAV
The extent of ecological effects is uncertain,
because most changes in SAV beds occur on a
significantly shorter time scale than can be
attributed to sea level rise.120 Some species of
seagrass could survive the effects of sea level
116Kemp et al., 2004 (see note 107).
117Orth, R.J., and K.A. Moore, 1984, "Distribution and
abundance of submerged aquatic vegetation in Chesapeake Bay:
An historical perspective," Estuaries 7:531-540; Kemp et al.,
2004, p. 365 (see note 107).
118See, for example, National Academy of Sciences, 2006,
Mitigating Shore Erosion along Sheltered Shores, The National
Academies Press. Washington, DC, pp. 46, 57.
119Koch, E.W., L.P. Sanford, S.-N. Chen, D.J. Shafer, and J.M.
Smith, 2006, Waves in Seagrass Systems: Review and Technical
Recommendations. Final Report prepared for the U.S. Army
Corps of Engineers, System-Wide Water Resources Research
Program and Submerged Aquatic Vegetation Restoration
Research Program, ERDC TR-06-15, p. 16.
120USFWS, n.d., Nutrient pollution (see note 103).
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[ 204 1 i ]
rise by expanding inland. Submerged vegetation
cannot grow and survive, however, where
increased water depth or increased turbidity
severely restrict the amount of light available for
photosynthesis. Short and Neckles estimate that,
in general, a 50 cm increase in water depth as a
result of sea level rise could reduce the available
light in coastal areas by 50 percent, reducing
seagrass growth in current bed areas by 30 to 40
percent.121 Such reductions in seagrass could
have a significant effect on the many fauna
found in seagrass beds. For example, research
indicates that the abundance, biomass, and
diversity of fishes are higher near seagrass beds
than in unvegetated areas.122
In areas where seagrass is lost, the primary
productivity, the habitat provided to key species,
and the shoreline protection benefits will all be
affected.123 The extent of primary productivity
impact is unknown; autotrophs like
phytoplankton and sediment microalgae are
generally not considered capable of providing
the extent of primary production contributed by
SAV.124 In Chesapeake Bay, the microbenthic
algal community comprises between 3 and 5
percent of the total annual primary production
from all sources.125 Vegetation also increases the
dissolved oxygen content of the water; low
dissolved oxygen in summer (common in many
Atlantic waterways) is a major stressor on biota
such as the blue crab, Atlantic sturgeon, and
striped bass.126 Wrack from submerged aquatic
121Short and Neckles, 1999,p. 178 (seenote91).
122Wyda et al., 2002, pp. 86-100 (see note 95).
123Duarte, C.M., 2002, "The future of seagrass meadows,"
Environmental Conservation 29(2): 192-206.
124Borum, 1996, in Duarte, 2002, p. 199 (see note 123); reviewed
in Buzzelli 1998, p. 659 (see note 92).
125Wendker, S., H.G. Marshall, andK.K. Nesius, 1997, "Benthic
primary production within shallow water sites in Chesapeake
Bay," pp. 148-151 in Proceedings of the Second Marine and
Estuarine Shallow Water Science and Management Conference,
U.S. Environmental Protection Agency, Philadelphia, PA, EPA
903/R/97009, USEPA, Washington, DC.
126For blue crabs, see Mistiaen, J.A., I.E. Strand, and D. Lipton,
2003, "Effects of environmental stress on blue crab (Callinectes
sapidus) harvests in Chesapeake Bay tributaries," Estuaries
26(2A): 316-322. For Atlantic sturgeon, see Niklitschek, E.J., and
D.H. Secor, 2005, "Modeling spatial and temporal variation of
suitable nursery habitats for Atlantic sturgeon in the Chesapeake
Bay "Estuarine, Coastal, and Shelf Science 64(2005): 135-148.
For striped bass, see Coutant, C.C., and D.L. Benson, 1990,
"Summer habitat suitability for striped bass in Chesapeake Bay:
Reflections on a population decline," Transactions of the
American Fisheries Society 119:757-778.
vegetation also plays an important role in beach
communities, providing cover and food to a
variety of amphipods, isopods, and insects,
which are in turn fed on by shorebirds such as
plovers.127
Loss of SAV affects the large number of species
that depend on the vegetation beds for protection
and food. As noted previously, blue crabs are
particularly dependent on seagrass beds,
although some types of shoreline structures (e.g.,
riprap and jetties) can provide similar protective
cover to juvenile crabs.128 By one estimate, a 50
percent reduction in SAV results in a roughly 25
percent reduction in striped bass production.129
Fish abundance and species richness are also
affected by degradation of SAV habitat. A
decline in SAV also affects larger predators,
including shorebirds and sea turtles. Birds that
are primarily herbivorous are directly affected by
the loss of SAV. For diving and dabbling ducks,
researchers have noted a decrease in SAV in
their diets since the 1960s. With the decline of
SAV, the diet of geese and swans has shifted to
agricultural field wastes. For canvasback ducks,
SAV consumption has been replaced by a diet
high in invertebrates and crustaceans. Such diet
shifts have not been possible for all SAV-reliant
species. The decreased SAV in Chesapeake Bay
is cited as a major factor in the substantial
reduction in wintering waterfowl such as redhead
ducks.130
3.1.6 TIDAL FLATS
Tidal flats are found in the intertidal zone. They
have muddy substrates, typically composed of
silt and clay, that support sparse or no
vegetation. In brackish area flats, vegetation is
rare, consisting of occasional clumps of
127Dugan, J.E., D.M. Elubbard, M.D. McCrary, and M.O. Pierson,
2003, "The response of macro fauna communities and shorebirds
to macrophyte wrack subsidies on exposed sandy beaches of
southern California," Estuarine, Coastal and Shelf Science
58S:25^10.
128Maryland Sea Grant, 2001, p. 10 in Research Needs for
Sustainable Blue Crab Production in Maryland, A Workshop
Report, publication number UM-SG-TS-2001-01, prepared by
Maryland Sea Grant College, College Park.
129Kahn, J.R., and W.M. Kemp, 1985, "Economic losses
associated with the degradation of an ecosystem: The case of
submerged aquatic vegetation in Chesapeake Bay "Journal of
Environmental Economics and Management 12:246-263.
130Perry and Deller, 1996, p. 273, 276 (see note 100).
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[ SECTION 3.1 205 ]
saltmarsh cordgrass.
Freshwater flats,
common in Chesapeake
Bay tributaries, can
support herbaceous
species. Tidal flats are
critical foraging areas
for numerous birds,
including wading birds,
migrating shorebirds,
and dabbling ducks
such as mallards and
the American black
duck.
Effects of Sea Level
Rise on Tidal Flats
In areas with low
sediment supplies,
marsh will revert to
unvegetated flats and
eventually to open
water.131 For example, in New York's Jamaica
Bay, several hundred acres of low salt marsh
have converted to open shoals (see Section 3.4).
Except in high-sediment supply areas and in
locations where migration is possible, tidal flats
will gradually become inundated as sea levels
rise.
Effects of Armoring on Tidal Flats
In areas where sediments accumulate in shallow
waters and shoreline protection prevents
landward migration of salt marshes, flats could
become vegetated as low marsh encroaches
waterward, accelerating sediment deposition at
the waterward edge of the vegetated area and
leading to an increase in low marsh at the
expense of tidal flats.132 If sediment inputs are
insufficient, tidal flats will convert to subtidal
habitats.
Photo 3.5: Estuarine beach and bulkhead along Arthur Kills, New Jersey
Shorebirds feed on all trophic levels of beach
invertebrate communities, including primary
consumers (herbivorous insects, amphipods, and
isopods as well as suspension-feeding crabs and
bivalves) and the secondary consumers that feed
on them (crabs, isopods, polychaetes, and
beetles).133 As tidal flat area declines, increased
crowding in remaining areas will lead to
exclusion and mortality of many shorebirds.134 In
some cases, reversion of Spar una marsh to
unvegetated flats could benefit foraging by
wading birds and dabbling ducks. As the flats
become more deeply inundated, however, they
will become unavailable to short-legged
shorebirds.131 Modeling by Galbraith and
colleagues predicted that under a 2°C global
warming scenario,
sea level rise could inundate significant areas of
intertidal flats in some regions.136 Although this
may initially lead only to crowding of remaining
Ecological Effects on Tidal Flats
Loss of tidal flats would eliminate a rich
invertebrate food source for migrating birds.
131Brinson et al. 1995, p. 650 (see note 23).
132Redfield, A.C., 1972, "Development of a New England salt
marsh," Ecological Monographs 42:201-237.
133See, for example, M.D. Bertness, 1999, Chapter 6, "Soft
sediment habitats," pp. 249-312 in The Ecology of Atlantic
Shorelines, Sinauer Associates, Inc., Sunderland, MA.
134Galbraith et al., 2002, p. 173 (see note 50).
135Erwin et al., 2004, p. 902 (see note 16); andErwin, R.W., n.d.,
Atlantic Sea Level Rise, Lagoonal Marsh Loss, and Wildlife
Habitat Implications. Accessed at:
http://www.pwrc.usgs.gov/reshow/erwinlrs/erwinlrs.htm on
March 16, 2006.
13oGalbraith et al., 2002, p. 178 (see note 50).
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[ 206 1 i ]
tidal flat forage areas, Galbraith and
coinvestigators further noted that increased
crowding will lead to the exclusion and mortality
of shorebirds.137 Ponds within marshes might
become more important foraging sites for these
birds as mudflats are inundated by sea level
138
rise.
3.1.7 ESTUARINE BEACHES
Estuarine beaches are unconsolidated sandy
shores that are inundated by the tidal cycle.
Throughout most of the mid-Atlantic region and
its tributaries, these beaches front the base of low
bluffs and high cliffs as well as bulkheads and
revetments. The beaches are characterized by
steep foreshores and broad, flat, low tide terraces
(see Photo 3.5).139 Beaches can also occur in
front of marshes, sometimes retreating back over
them through storm-driven overwash processes.
Plants are typically sparse in beach areas,
surviving only above the high tide line with
adaptations for the harsh beach environment,
such as waxy leaves or strong root systems. In
Chesapeake Bay, such plant species include
seabeach and marsh orach (Atriplex cristata), sea
rocket (Cakile edentula), Russian thistle (Salsola
kali), and seablite.140
The most abundant beach organisms are
microscopic invertebrates (meiofauna) that live
between sand grains, feeding on bacteria and
single-celled protozoans. It is estimated that
more than 2 billion of these organisms can be
found in a single square meter of sand.141 The
meiofauna play a critical role in beach food webs
as a link between bacteria and larger consumers.
The most conspicuous invertebrates of beaches
are the macroinvertebrates that burrow in
sediments or hide under rocks. These include
hermit crabs, beach fleas, worms, beach
amphipods, bivalves, and snails. Various rare
and endangered beetles also live on sandy
shores. Diamondback terrapins and horseshoe
137Galbraith et al., 2002, p. 173 (see note 50).
138Erwin et al., 2004, p. 902 (see note 16).
139Jackson, N.L., K.F. Nordstrom, and D.R. Smith, 2002,
"Geomorphic-biotic interactions on beach foreshores in
estuaries," Journal of Coastal Research Special Issue 36:414-
424.
140Lippson and Lippson, 2006, p. 28 (see note 2).
141Bertness, 1999, 256-257 (see note 133).
crabs bury their eggs in beach sands. Piping
plover (federally listed as threatened), American
oystercatcher, and sandpipers feed on beetles,
larvae, marine worms, mollusks, and other
insects and crustaceans, as well as on horseshoe
crab eggs.142 In mid-Atlantic bays, particularly
Delaware Bay and southern Chesapeake Bay,
horseshoe crabs rely on estuarine beaches for
spawning during high spring tides.143 Migrating
shorebirds and resident gulls and terns feed on
the horseshoe crab eggs. The diamondback
terrapin nests in sandy areas above the high tide
mark and may hibernate along embankments on
muddier shorelines.144
Eggs of species that nest on estuarine beaches
and invertebrate infauna provide forage for
numerous bird species, including migratory
shorebirds and species that nest on nearby barrier
islands, such as the piping plover (federally
listed as threatened). Shorebirds feed on all
trophic levels of beach invertebrate communities
(see Photo 3.6).145 The insects, isopods, and
amphipods found in wrack deposits on estuarine
beaches are also an important source of forage
for birds (see Photo 3.7).146 The abundance of
these organisms has been shown to be highest at
sites with greater wrack. In addition, the
abundance of shorebird species is positively
correlated with the abundance of wrack and
wrack-associated invertebrates.147
142USFWS, 1988, Endangered Species Information Booklet:
Piping Plover, USFWS, Arlington, VA.
143Lippson and Lippson, 2006, p. 32 (see note 2); Dove and
Nyman, 1995 (see note 14).
144Chesapeake Bay Program, 2006, Diamondback terrapin,
available at:
http://www.chesapeakebay.net/diamondback_terrapin.htm,
accessed June 13, 2006.
145Dugan et al., 2003, p. 26 (see note 127).
146Jackson et al., 2002 (see note 139).
147Dugan et al., 2003, pp. 32-33 (see note 127).
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[ SECTION 3.1 207 ]
F-''
„
¦¦
Photo 3.6. Dinnertime along Peconic Estuary Beach, Long Island, New
York
Photo 3.7: Beach with beach wrack and marsh in New Jersey
Effects of Sea Level Rise on Estuarine
Beaches
As with vegetated tidal wetlands, the fate of
estuarine beaches depends on their ability to
migrate or on the presence of sufficient sediment
to allow accretion. Beaches can migrate through
marshes, generally through a process of
overwash and dune
building, as exhibited by
barrier islands.148'149 The
general lack of vegetation
on the beaches, however,
frequently limits the
ability to retain sediment.
In front of shoreline
protection structures, or
where the land behind the
existing beach has too
little sand to sustain it,
beaches that are not
nourished will erode and
eventually drown as sea
level rises. If impediments
to migration exist or
natural sediment inputs
decline, beaches will be
lost. Through nourishment
efforts, society will
preserve many beaches at
risk of erosion. But in
many areas where homes
are built on the shoreline,
beach loss will be
inevitable.
Effects of Armoring
on Estuarine Beaches
Many shoreline
protections interfere with
the survival of estuarine
beaches by both blocking
migration and affecting
sediment retention.
Because of the sediment
trapping effects of many
shore protections,
armoring that traps sand
in one area can limit or
eliminate longshore
transport. This, in turn,
diminishes the constant replenishment of sand
necessary for beach retention in nearby locations.
Areas with bulkheads frequently have artificially
148Jackson et al.. 2002, p. 418 (seenote 139).
149The overwash process is also observed on peninsulas (e.g., the
migration of Bethel Beach over marsh area in Mathews County,
Virginia). See Section 3.12, Chesapeake Bay's Middle Peninsula.
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[ 208 1 i ]
elevated land areas, or headlands, because not all
structures are built in a straight line. In areas
with sufficient sediment input relative to sea
level rise (e.g., upper tributaries and upper
Chesapeake Bay), accretion may keep beaches in
place in front of armoring.
In armored areas between headlands, the beach is
likely to become steeper and the sediments
coarser. Waterward of the bulkheaded headlands,
the foreshore habitat will be lost, often even
without sea level rise.150 If the areas between
these headlands are not armored, in most cases
sediment input will be reduced and inundation
will occur with rising sea level.
In many developed areas, estuarine beaches may
be maintained with beach nourishment, although
the ecological effects of nourishment remain
uncertain.151 Beach nourishment will allow
retention in areas with a sediment deficit, but
could reduce habitat value through effects on
sediment characteristics and beach slope.152
Some think that benthic organisms on the
shallow, low tide terrace of estuarine beaches are
less tolerant of burial as a result of beach
nourishment than organisms of the subtidal zone
of more energetic beaches.153 The viability of
horseshoe crab eggs depends on sediment
characteristics that promote drainage and
aeration, and therefore some coastal
geomorphologists predict that egg survival could
be low on beaches that are modified through
beach nourishment.154 On the other hand,
Delaware plans to nourish beaches that lie in
front of marsh for the purpose of preserving
horseshoe crab habitat.155
150Jackson et al., 2002, p. 420 (see note 139).
151Peterson, C.H. and M.J. Bishop, 2005, "Assessing the
environmental impacts of beach nourishment," Bioscience
55:887-896.
152Peterson and Bishop, 2005 (see note 151).
153Nordstrom, K.F., 2005, "Beach nourishment and coastal
habitats: Research needs to improve compatibility," Restoration
Ecology 13:215-222, p. 217.
154Jackson et al., 2002, p. 421 (see note 139).
155See, for example, Smith, D., N. Jackson, S. Love, K.
Nordstrom, R. Weber, and D. Carter, 2002, Beach Nourishment
on Delaware Shore Beaches to Restore Habitat for Horseshoe
Crab Spawning and Shorebird Foraging, prepared for The
Nature Conservancy, Delaware Bayshores Office, Wilmington,
DE, accessed on June 19, 2007 at:
http: //www. dnrec. state. de.us/fw/hcrabs/FINAL%20Beach%20Ha
bitat%20Restoration%20Report.pdf.
Ecological Effects on Estuarine Beaches
Where beaches are lost, the many invertebrates
that burrow in the sand and species that spawn
on beaches will lose critical habitat. Using high-
precision elevation data from nest sites,
researchers are beginning to carefully examine
the effects that sea level rise will have on
oystercatchers and other shore birds.156 To the
extent that estuarine and riverine beaches,
particularly on islands, survive better than barrier
islands, shorebirds like oystercatchers might be
able to migrate to these shores.157 Loss of beach
will also cause local elimination of beach-
dependent species such as the rare beetles found
in Calvert County, Maryland. Although the
northeastern beach tiger beetle is able to migrate
in response to changing conditions, suitable
beach habitat must be available nearby.158
The degree to which horseshoe crab populations
will decline as beaches are lost is currently
unclear. Early results of ongoing research funded
by New Jersey Sea Grant indicate that horseshoe
crabs also lay eggs in other intertidal habitats in
addition to estuarine beaches, such as sandbars
and the sandy banks of tidal creeks.159
Nonetheless, if these habitats are also inundated,
they will provide only temporary refuges for
horseshoe crabs.
Where horseshoe crabs decline because of loss of
suitable habitat for egg deposition, there can be
significant implications for migrating shorebirds,
particularly the red knot, which is a candidate for
the federal endangered species list. The red knot
feeds almost exclusively on horseshoe crab eggs,
and, to continue its migration, the bird nearly
doubles its weight by feeding on crab eggs.
Researchers from Virginia Tech and the New
156Rounds, R. and R.M. Erwin, 2002, "Flooding and sea level rise
at waterbird colonies in Virginia," presented at Waterbird Society
Meeting, November 2002, accessed on June 19, 2007 at:
http://www.vcrlter.virginia.edu/presentations/rounds0211/rounds
0211.pdf.
157McGowan et al., 2005, p. 150 (see note 81).
158USFWS, 1994, Recovery Plan for the Northeastern Beach
Tiger Beetle (Cicindela dorsalis dorsalis), USFWS, Hadley, MA.
159Research by Dr. Mark Botton of Fordham College and Dr. Bob
Loveland of Rutgers University, funded by New Jersey Sea
Grant; summarized online and accessed on June 19, 2007 at:
http://www.njmsc.org/Sea_Grant/Research_News/The_Importan
ce_Of_Marginal_and_Restored_Habitats.htm.
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[ >N 3,1 209 ]
Jersey Division of Fish and Wildlife report that
the number of horseshoe crab eggs is the most
important factor determining the use of mid-
Atlantic back-barrier beaches by red knots, and
documented a reduction in the number of red
knots throughout the Delaware Bay correlated
with a decline in horseshoe crabs (see also
Section 3.9 on Maryland and Delaware Coastal
Bays.160
3.1.8 CLIFFS
Cliffs and the sandy beaches sometimes present
at their bases are constantly reworked by wave
action, providing a dynamic habitat for cliff
beetles and birds. Little vegetation exists on the
cliff face because of constant erosion. Eroding
sediment augments nearby beaches. Cliffs are
present on Chesapeake Bay's western shore and
tributaries and its northern tributaries (see Photo
3.8), as well as in Hempstead Harbor on Long
Island's North Shore.
Erosion is driven by two key processes:
freeze/thaw and wave undercutting. Recession
rates for cliffs are higher in areas where
undercutting is the dominant erosion method; for
example, Wilcock and coworkers reported
historical erosion rates between 0.3 and 1 ft/yr
for freeze/thaw areas of Maryland's Calvert
Cliffs and rates between 2 and 3 ft/yr for wave
undercut areas.161 On the Sassafras, near its
entrance at the north end of Chesapeake Bay, the
cliffs are receding at rates of 0.9 to 1.4 ft/yr.162
Areas dominated by the freeze/thaw mechanism
frequently have beaches at their base (a higher
toe elevation) that protect the bottom of the slope
from wave energy.163
Effect of Sea Level Rise on Cliffs
Sea level rise may increase rates of cliff erosion
by decreasing the toe elevation, but ecological
impacts of such an increase in erosion rate are
uncertain. If erosion rates are too high, sudden
losses of the cliff face can endanger species that
depend on unvegetated cliffs (e.g., Puritan tiger
beetles). The armoring that is in place, or that
might be increased in response to accelerated sea
level rise, poses more evident threats to the cliff
ecology.
160Karpanty, S., J. Fraser, J. Berkson, L. Niles, A. Dey, and E.
Smith, 2006, "Horseshoe crab eggs determine red knot
distribution in Delaware Bay habitats," Journal of Wildlife
Management, 70:1704-1710.
161Wilcock, P.R., D.S. Miller, R.H. Shea, andR.T. Kerhin, 1998,
"Frequency of effective wave activity and the recession of coastal
bluffs: Calvert Cliffs, Maryland," Journal of Coastal Research
14(l):256-268.
162Maryland DNR, 2002, Sassafras Natural Resources
Management Area Land Unit Plan, Maryland DNR Resource
Planning Program, accessed on June 19, 2007 at
http://www.dnr.state.md.us/resourceplanning/sassafras.pdf.
163Toe elevation is the height of the beach before the bluff/cliff
begins.
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[ 210 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Photo 3.8. Emerald Beach along the Elk River in Maryland
Effects of Armoring on Cliffs
Cliffs and headlands could experience increased
erosion rates resulting from disruption in
longshore sediment transport as a result of
nearby sediment-trapping shoreline protections
(e.g., groinfields).164 Alternatively, if the cliff
base is armored, the erosion rates could decrease.
Either outcome could eliminate habitat for
endangered species that depend on varying rates
of erosion. According to the Maryland
Department of Natural Resource's wildlife
diversity conservation plan, naturally eroding
cliffs are "severely threatened by shoreline
erosion control practices."1,65 Because of the
sediment-trapping effects of many types of shore
protection, armoring in one area can diminish the
constant replenishment of sand necessary for
beach retention in nearby locations. Introducing
shoreline protections can subject adjacent cliff
areas to wave undercutting and higher recession
rates. Development and shoreline stabilization
structures that interfere with natural erosional
processes are cited as threats to bank-nesting
birds (e.g., bank swallows and belted
kingfishers) as well as two species of tiger
beetles (federally listed as threatened) at
Maryland's Calvert Cliffs.1®'167The majority of
the identified Puritan tiger beetles live in the
Calvert Cliffs, particularly in Calvert Cliffs State
Park on Chesapeake Bay's western shore.
lo4Wilcock et si. 1998, p. 259 (see note 161).
^Maryland DNR, 2005, p. 13 (see note 53).
I 'SI W S. 1993, Puritan Tiger Beetle (Cicindela pnritcma G,
Horn) Recovery Plan, Hadley, MA; USFWS, 1994 (see note
158).
lo7The Center for Conservation Biology at William & Mary,
1996, "Fieldwork concluded on bank-nesting bird study," in
Cornerstone Magazine, accessed on .Time 21, 2006, at
https://www.denix.osd.mil/denix/Public/ES-
Programs/Conservation/Legacy/Cornerstone/corner.html.
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