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Coastal Marine Ecology
From Rivers
To Reefs…
What is an
ESTUARY?...
A
semi-enclosed
coastal embayment
where fresh and
saltwater meet and
mix (brackish).
 In contrast to other
transitional ecosystems, estuaries
have few species of
permanent
residents.
Types of Estuaries…
 COASTAL
PLAIN: the most common
 Formed at the end of the last iceage due to rising sea level.
Example: Chesapeake Bay
the largest in the United
States.
Semi-enclosed bay or lagoon

Sandbars build up parallel to the coastline
and partially cut off waters behind them
from the sea.
Example of a lagoon estuary:

This creates a
shallow lagoon
behind the
sandbars,
which collects
runoff.
Pamlico Sound off
Cape Hatteras,
NC. The narrow
band of barrier
islands forms the
lagoon.
Physical Characteristics of Estuaries:

Conditions in estuaries vary a lot, which can
create a stressful environment for organisms:
Salinity- the dominant factor of the
estuarine environment is the
fluctuation in salinity.
- the major factor affecting salinity is
runoff from the surrounding watershed.
- when salinity is greatest at the
bottom and lowest near the surface, a
salt wedge forms.
Salinity Adaptations…
To survive, benthic
organisms must be
able to tolerate
frequent changes in
salinity.
 The great majority
of estuarine animals
are marine species.
 Oysters stop feeding
& close their shells
when salinity goes
down.
 Others burrow.

Salt Marsh Estuaries…
 Salt
marshes border temperate (4
seasonal changes) and sub-polar
estuaries and protected marine
shores worldwide.
 Form a transition area between
aquatic and terrestrial (land)
ecosystems.
 Communities
of emergent
plants (plants that stick up
out of the water), known as
HALOPHYTES, rooted in soils
alternately flooded & drained
by tidal action.
 Salt marshes act as “kidneys”
to filter water, “sponges” to
absorb high waters during
storms, and “nurseries” for
many valuable marine
species.
Life cycle of the edible pink shrimp:
Barrier Islands:
A string of sand isles
that runs parallel to
the Atlantic & Gulf
coasts.
 So called because
they protect the
mainland from
storms.
 295 major islands in
the 18 coastal states
from Maine to Texas.
 Florida is 1st with 80,
followed by SC w/35.

Barrier Islands:
Bordered on one
side by tidal
marshes, creeks
& rivers, and on
the other side by
beaches, sand
dunes, sand bars.
 Between lies the
maritime forest,
made up primarily
of oaks and palm
trees.

Cross-section of a typical barrier island
Secondary dunes
Swash zone
Ocean
Primary
dunes
Salt
Bay
marshes
Barrier
flat
Maritime forest
Cross section of a salt marsh
Tidal creek
Spartina
Black needle rush
Maritime forest
Tidal creek
Flora & Fauna of the Salt Marsh
 Plants:
salt marshes are one of the most
productive ecosystems on Earth, along
with rain forests, sea grass beds, kelp
forests and sugarcane fields.
 Salt marshes are so productive because of
the abundance of the salt marsh
cordgrass called Spartina.
 Also present are plants called black needle
rush, and salt pickle.
Salt marsh cordgrass Spartina

Spartina grows the
closest to the
banks of the tidal
creeks that wander
through the
marsh.
 It is a perennial
plant that, as it
dies off, produces
huge amounts of
detritus, that is
used for food.
“Where in the marsh are we???”
Spartina
(cord grass)
Salicornia
(pickle weed)
Juncus
(black needle
rush)
Animals of the Salt Marsh…
The most abundant animal is the fiddler crab
(Uca pugilator).
 As detritovores, they are an important link in
the food chain.
 Males have one large claw.

Fiddler crab burrows aerate the
mud which affects Spartina
growth.
Grass shrimp:
Abundant along both
Atlantic and Gulf
coasts.
 Also an important
link in the
estuary/salt marsh
food web.
 Detritovores.
 Can be collected at
high tide along grass
line.

Birds of the Salt Marsh…
Rarely does one
visit the salt
marsh that a
number of
different birds
can’t be seen.
 Great blue heron
 Pelican
 Sea gull
 Black skimmer
 Clapper rail

Mangrove Swamps…
A type of tree that
replaces salt
marshes.
 Found in warmer
tropical/subtropical
environments.
 4 types:

red, black, white
and buttonwood.

The most obvious
is the red mangrove because of
its “prop roots.”
Red Mangorves:
“The tree that walks.”
 Red mangroves produce
seedlings called
“propagules” that drop
from the tree and either
take root where they
fall, or drift away on the
tide.
 As they grow, they build
up more land as the
roots trap sediment
that otherwise would
have choked out coral
reefs.

Ecosystem from top to bottom!
One of Florida’s
true natives.
 Able to separate
fresh water
from salt water.
 Their roots
provide nursery
grounds for
many marine
species.
 Canopy provides
rookeries for
pelicans, etc…

Black Mangroves:
Found growing higher up
above the reach of high
tide than the red
mangrove.
 Are more salt tolerant
than the red even
though it is further out
of the water.
 Has distinctive roots
sticking up out of the
mud called
“pneumatophores.”

Beaches & Dunes: