Transcript Issues in Coastal Management

Introduction to Barrier
Island Ecology
Biology 366 Ecology
16 April 2002
Barrier Island Transect
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Beach and Dunes
Shrub Thicket and Maritime Forest
Freshwater Wetlands
Tidal Marsh
Estuarine Waters/Sand and Mud
Flats
Dune Formation
Sand, moved by the process of
saltation, accumulates around
objects including vegetation and
flotsam
Dune Formation
• Elements required for dune
formation
Sand
Wind
Object
American
Beachgrass
(Ammophila
breviligulata)
Sea Oats (Uniola paniculata)
Panic Grass
(Panicum
amarum)
Saltmeadow
Cordgrass
(Spartina
patens)
Strand Line or Wrack Line
• Line of debris
at spring tide
• Debris is
called
“wrack”
• Most dunes
form here
Strand Line or Wrack Line
• Large quantities
of sand moved
across strand
• Common on
prograding
(growing) beaches
• Rare on eroding
beaches
Dune Environments
• Youngest strand lines lie most
seaward
• Multiple dune ridges form as strand
lines are colonized
Oldest - - - - - - > Youngest
Dune Environments
• Dunes and colonizing plants grow in
concert
Year 3
Year 2
Year1
Dune Environmental
Conditions
• Low soil
nutrients
(N and P)
• Desiccating
winds
• Blowing
sand
Dune Environmental
Conditions
• Air and soil
temperatures
are highly
variable
Dune Processes
• Unvegetated
dunes “migrate”
or move from <1 m
to >15 m annually
• Migrating dunes
engulf
surroundings
 Natural revegetation a long term
process
Blowouts
• Occur when
vegetation mantle
is destroyed
• Difficult to stop,
once started
• Creates
environment
called “slack”
Natural and Man-induced
Impacts on Dunes
• Oceanic overwash
• “erosion”
• Off-road vehicle (ORV)
traffic
• Sand fencing: wooden,
brush, trees
Washovers
Salt Aerosol Impacts
Salt aerosol effects on plants
Salt
aerosol
source
this
side
Source of Salt Aerosols
Salt Aerosols
Salt Aerosol Impact on
Plants
Source of
salt aerosol
(ocean side)
Salt Aerosol Impact on
Plants
• Generally decreases from
strand line, landward
• Highest on foredunes
• Lowest in slacks and lee of
dunes
Coastal Communities and
Processes
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Beach and Dunes
Shrub Thicket and Maritime Forest
Freshwater Wetlands
Tidal Marsh
Estuarine Waters/Sand and Mud Flats
Shrub Thicket
Environments
• Early colonizers
(survive low nutrients)
• Best examples are in
dune slacks
• Reduced salt aerosol
environment allows
arborescent vegetation
to flourish
Wax Myrtle (Myrica
pennsylvanica)
• Northern Bayberry is
common in thickets
from Cape Hatteras
northward into New
England
• Bayberry candles are
made from the waxy
coating on the berries
Yaupon (Ilex vomitoria)
Maritime Forest
Environments
• Develop under the
influence of salt aerosols
• Restricted distribution
• Shear edge created by
salt aerosols
Maritime Forest
Environments
• Species adapted
to:
– Low salt aerosols
– low soil nutrients
– sandy soils
• Salt aerosols
control location
and structure of the
maritime forest
Maritime Forest
Environments
• Vines are common
• Tree leaves small, thick, evergreen
Live Oak (Quercus virginiana)
Bear oak (Quercus illicifolia)
common along New England
maritime-influence forests
Southern Red Oak
(Quercus falcata)
Common in Mid-Atlantic maritime
forests
Red Cedar
(Juniperus virginiana)
ocean
Salt aerosol damage
American Holly (Ilex opaca)
Loblolly Pine (Pinus taeda)
Loblolly pine is
the most common
pine in the
maritime forest.
It typically is
successional and
is replaced by live
or laurel oak in
the southeastern
US.
Woodbine (Parthenocissus quinquefolia)
Dogwood (Cornus florida)
Poison Ivy
(Rhus toxicodendron)
Development of Maritime
Forests
• Develop on coastal
dune systems
• Sterile sandy soils
• Hummocky
topography
• Begin as scattered
shrubs
Natural Impacts on Maritime Forests
Impact of hurricanes on maritime forest
vegetation. Pines are typically snapped
off; cabbage palms survive. Live oak
and magnolia have branches and leaves
ripped off.
Large migrating dunes are capable
of overwhelming shrub and forest
vegetation
Significant Human Impacts
• Fragmentation occurs when
development occurs within a
continuous forest
Forest opened to
salt aerosol
impacts when
development
occurs
Freshwater Wetland
Environments
• Ponds,
swamps,
marshes
• Form where
water table
intersects
ground surface
Freshwater Wetland
Environments
Water flows from adjacent
dunes into slough between
dunes
• Receive
groundwater
input from
adjacent dunes
• Influenced by
groundwater
and rainfall
Freshwater Wetlands
• Cattails (Typha spp.)
• Bulrush (Scirpus spp.)
Tidal Marsh Environments
• Develop in areas
protected from
wave attack
• Topographically
flat, incised with
drainage creeks
Tidal Marsh Environments
• Alternately
exposed and
covered by
tides daily
• “Pulsestable”
environment
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Tidal Marsh Environment
• Saltmeadow
Cordgrass (Spartina
patens)
• Smooth Cordgrass
(Spartina
alterniflora)
Zonation
• Cordgrass
dominant
above and
below mean
tide level
• Many other
species
dominant
above average
high tides
Black Needlerush
(Juncus roemerianus)
Black Needlerush
Black Needlerush is common at the upper edge of the
tidal marsh where the tide floods only occasionally
Sea Lavender
(Limonium carolinianum)
Sea Ox-eye
(Borrichia
frutescens)
Glassworts
(Salicornia spp.)
These succulent plants grow in
the most saline environments in
the tidal marsh area
Formation of Tidal Marsh
• Sand and mudflats
colonized by smooth
cordgrass
– must reach critical
elevation
– seed falls on flats
– spread by rhizomes
Typical
environments
colonized by smooth
cordgrass primarily
by seeds
Formation of Tidal Marsh
Colonization
by Spartina
alterniflora
Sand flats are
colonized by
clumps of
smooth
cordgrass.
Alternatively, the
sand flats can be
colonized by
germinating
seeds of smooth
cordgrass.
Formation of Tidal Marsh
• Sand flats may
become
uniformly
vegetated in 25 years
• Creeks
become
incised as
community
matures
Human Impacts
• Finger canals
(now outlawed
in all states)
• Point and nonpoint source
runoff
Mudflats and Sandflats
• No rooted aquatic
vegetation
• Significant infauna
(clams, worms, etc.)
• Important habitat for
organisms in intertidal
environments
Submerged Aquatic
Vegetation
• Typically composed of
seagrasses
– Marine flowering plants
– 13 genera; 58 species
worldwide
• Grow in shallow subtidal
or intertidal water on soft
muds and sandy
sediments (some on
rocky substrates)
• Evolved from terrestrial
grasses
Turtle Grass,
Thalassia testudinum
Lifestyle Requirements for
Seagrasses
• Must be adapted to saline waters (true halophyte)
• Must be able to grow completely submerged
• Must be securely anchored in the substrate
(some species are anchored to rocky substrates)
• Must be able to flower, fruit and produce seeds in
water
• Leaves and stems lack waxy cuticle typical of
terrestrial plants
• Typically possess aerenchyma tissue for
bouyancy
Occurrence
• Worldwide in distribution
• In US, found on Atlantic, Pacific, and Gulf
coasts
• 90% of seagrasses in US are in Gulf of
Mexico
– Major beds in Chesapeake Bay, Florida, Texas
and California
• Occur primarily in “beds,” typically patchy
in nature
• Grasses typically found in 10-15 m of
water, but have been found down to 130
feet
Ecology of Seagrass Beds
• Seagrass beds are important to:
– Grazers—manatees, ducks, etc.
– Epiphyte grazers—feed on seagrass
epiphytes—sea urchins, fish, etc.
– Detritus feeders—feed on decaying
organic matter
– Shelter for conch, starfish, sand
dollars, etc
• Substrate and food for bay barnacles,
sea squirts, sponges, isopods,
amphipods, snails, seahorses,
anchovies, silversides, shrimp, blue
crabs, waterfowl and others
Ecology of Seagrass Beds
• Bind sediments with extensive rhizomes
and roots
• Baffle waves and currents
• Trap sediments/clear the water column
• Improve water quality by taking up
nutrients (epiphytes do the same)
• Important in oxygenating water
• Seagrass systems protected under federal
“no-net-loss” policy for wetlands
Vulnerability of Seagrass
Beds
• Conditions resulting in reduction of
seagrass beds
– Nutrient loading
– Light reduction
– Physical destruction
• Rate of loss: weeks to months
Propeller scars on seagrass
• Rate of recovery: years
beds near Windley Key,
– Vegetatively slow recovery
Florida Keys
– Seeding shows more rapid recovery
Common Seagrasses of the
Eastern and Gulf US
Turtle Grass
Thalassia testudinum
Shoal Grass
Halodule wrightii
Eel Grass
Zostera marina
Manatee Grass
Syringodium filiforme
Widgeon Grass
Ruppia maritima
Paddle Grass Halophila decipiens
Causes of Decline in
Seagrasses
• Dredge and fill
operations
• Mooring scars
• Propeller scars
• Vessel wakes
• Jet skis
• Fish and shellfish
harvesting
techniques
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Sewage outfalls
Thermal pollution
Disease
Storms
Ice scour
Epiphyte load
Burrowing shrimp
Green algae