Transcript Seawater flooded the land and was trapped by barrier

ESTUARIES
Estuaries are semi-enclosed,
transition areas where fresh water
mixes with salt water (called
brackish).
U.S. has nearly 900 estuaries.
Most were formed at the end of
the last glacial period by rising
sea level.
NOAA
Seawater flooded the land and
was trapped by barrier island
bays, river deltas and
earthquakes.
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
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Estuaries should have:
1. lower salinity with more
euryhaline organisms than
stenohaline organisms
2. good light and low suspended solids (silt) that allows the
primary producers (sea grasses) to grow
3. nutrients that come from river runoff and provide for a
detritus- based food chain; the inverted energy pyramid
increases productivity
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
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Productivity and biomass are extremely high. Specie diversity is
directly related to fluctuations in salinity, temperature, oxygen,
nutrients and light.
Salt wedges of seawater form under river runoff when the tide
comes in. This layers the salinity.
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
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The shallow water restricts
large predators.
Tidal ebb with river runoff causes a net flushing of estuaries
and the tides transport larvae and nutrients back into the ocean.
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
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The three most common estuarine environments are:
1. Salt marshes - also called
wetlands, swamps or mangrove
communities.
Producers like Spartina (marsh
hay and cord grass) are found
mostly in intertidal water.
During the summer, grasses die
and provide nutrients for crabs,
isopods, snails, and worms.
NOAA
However as warm weather
increases productivity, oxygen
depletion can occur.
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
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2. Mud Flats - or oyster reefs found in lower intertidal and subtidal
zones; primarily composed of bacteria and fungi that carry out
anaerobic metabolism.
NOAA
Infauna have a more stable environment than the epifauna because
mud traps the salt.
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3. Sea Grass Communities primarily subtidal zones where animals
find food and hiding places.
Sea grasses stabilize the substrate and air
tubes from the leaves to the roots help
oxygenate plants living in anaerobic mud.
NOAA
Salt excreting leaves of grass
slow currents and provide a
place of attachment to
prevent animals from
smothering in the sediments.
NOAA
NOAA
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Estuaries are usually the first dumping site for pollution and
industrial discharges.
Dredge and fill operations that improve navigation and drainage,
damage wildlife and stir up pollution trapped in sediments.
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People thought estuaries (swamps) could be “improved” by filling
them in for housing developments.
Retention ponds and detention lakes do not replace
estuaries if there is no outlet to the sea.
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Estuaries are important because
they support a large commercial
seafood industry, prevent coastal
erosion, trap sediments from
entering the sea, provide
recreation, wildlife habitat and …
Marine Biology and Oceanography© by Carol Matthews Published by Teaching Point
They are the
seas’ nursery!
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