Barrier Islands

Near shore

high energy enviroment: wave beaking and wave runup

cross shore and along shore sand transport

contains sand bars and troughs

-home to small fish, shellfish, mole crabs

Beach

primarily bare sand

exposed to wave run up and tides

shifting sands, sun, strong winds, salt spray

-forging grounds for shore birds (gulls, terns, plovers)

-sea turtle nesting areas

Dune

form via wind blown sand captured by vegetation: AEOLIAN transport (sand moves waves)

large sand ridges; highest part of the barrier island

stabilized by vegetation; roots catch and hold sand

bio film

seaoats

American Sea Grass

Dominant in frontal dunes in the eastern U.S Rhizomes spread quickly, tolerate partial burial, and trap sand- building taller, more storm resistant dunes

Sea Oats

Key dune builder in warmer coastal regions. Tall growth and dense root slow wind, capture sand, and reinforce dune ridges

Bitter panicum

common on mid Atlantic islands

blue-green foliage and clumping form trap sand, creating vegetation- accretion feedbacks

ALL ACT AS ECOSYSTEMS ENGINEERS, and raise island elevation and reduce storm impacts

Hard Costal Conditions: Salt water and stress

waxy coatings and smaller leaf area reduce water loss and limit salt spray damage in saline soils

Hard Costal Conditions: Rooting and anchorage

Deep or spreading roots stabilize plants in shifting sand and help acsess scarce freshwater.

Hard Costal Conditions: Disturbance Recovery

Many dune grasses grow upward when partially buried and rebound quickly after storm and sand movement

help link physiology to enviromental pressure and natural selection

Barrier Flats

protect areas behind dunes

martitime grasslands to herbaceous plants and shrubs

generally not impacted ny larger storms, so saltwater forests can succeed

Salt Marsh

flooded only at high tide

low marsh: flooded frequently

plants cannot regulate high salinity and flooding compete for higher ground

-cordgrass common spartina

Lagoon

sheltered from waves

variable salinity values

estuarine waters support species like diamondback terrapin and fish

Inlets

fill back back in

remain in perpetuity flood tide delta formation

overwash can breach the width- splitting it in half

Island Migration

-lateral

-land sea-ward (islands migrate landward with sea level rise)

-higher topography reduces migration

Biogeography- interacts w/geomorphology altering evolution

vegetation retains and stabilizes dunes

Importance of Barrier Islands

protect coats

absorb and dissipate wave energy and storm urge

reduce coastal erosion

protects mainland ecosystems and communities

HABITAT DIVERSE ENVIROMENTS

NUTRIENT CYCLING

NATURAL LABORATORIES

Ghost crabs – Ocypode

Scavenger, predator on insects and other beach fauna; have been known to consume sea turtle eggs and small bird and hatchlings

• Live in burrows, often just above the high tide line. Leave to scavenge mainly at night

• Semi-terrestrial and breathe through moistened gills – must periodically moisten

them. Can use fine hairs located on the base of their legs to wick up water from

damp sand.

• Have some ability to adjust colors to match surroundings – enabling them to occupy various colors beach sands

Surf clams - Spisula

Surf zone to 180 ft deep

• Can live up to 35 years

• Suspension feeders

• Active burrowing polychaetes

Horseshoe crabs

Can spawn on outer beach areas

• Eggs are an important food source for many shorebirds

• Blood used as an indicator for bacterial contamination of vaccines

Terrestrial

Insects of various types common

• Spiders, scorpions

Threats Invertebrate Fauna

Development on Island

• Trampling on beach and shallow substrate

• Runoff and trash

• Beach renourishment

• Oak Island, Bald Head, Wrightsville Beach, Topsail, many others

• Effects at site and in borrow area

• Pets

• Factors affecting movement of Island and movement of inlets

Fish Ocean Side

Migratory route – offers some shallow water and wave pounded refuge

East coast: Shad, herring, striped bass, croaker, sharks

West coast: surfperch, salmon, sharks

spawning, temperature , food availability; staying close to shore may reduce predation

Shorebirds

Plovers, sandpipers, willets, oyster catcher, gulls

• Mostly foraging for exposed or shallow invertebrates and small fish

Wading birds

Herons, egrets

Consume shallow water fish and larger

invertebrates (e.g. blue crabs, oysters)

Diving birds

Pelicans, terns, cormorants,

• May use barrier island as roosting area

• Prey on small fish, shrimp, other

Many use barrier Islands as nesting area, especially ground nesting shorebirds

Birds – General Threats

Human disturbance (scaring birds, interrupt feeding)
Invasive species (ex: coyote)
Development (disrupt dunes + nearshore areas)
Dogs and cats
Beach renourishment
Loss of food sources
Toxic chemicals and metals
Trash
Island and inlet movement

Mammals: Aquatic

Certain seals and sea lions, including walrus in some locations

• May be more generally using ocean beaches rather than specifically barrier island beaches

Mammals: Terrestrial

Often depends on degree of separations from mainland

• Closer – more ephemeral users such as coyotes

• Further, may be much less use

• Some can have significant impact on shorebirds and sea turtles

Endangered Species: sea turtles

Kemp’s Ridley considered most endangered (most

recent nest estimate of 1947

• All but green sea turtle are considered endangered

• Many threats relate to beach nesting

Variety of issues facing ocean shorelines

Shoreline erosion

 Inlet migration

 Direct and indirect impacts of coastal

development (water quality, habitats,

recreational and commercial uses)

 Multi-use conflicts

 Aesthetics

Inlet Migration

An issue for certain types of coasts, including North and South Carolina

 Is an issue for Barrier Island development

 Shell Island example

Main Erosion Control Methods Used for Shorelines

• Beach renourishment

• Bulkheads (includes sand bags)

• Breakwaters / groins

• Revetments