Transcript Estuary Powerpoint

JQ: What is an estuary?
The Kalalau Trail – Kauai
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-Estuaries - partially enclosed, coastal
and transition areas where fresh water
from rivers mixes with seawater (called
brackish)
ESTUARIES
-Estuaries are highly affect by humans
-Productivity and biomass are
extremely high
-Primary producers are sea grasses
that need good light and low sediment.
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NEW JERSEY ESTUARIES
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TYPES OF ESTUARIES
1. Drowned River Valleys or
Coastal Plain Estuaries
Formed when sea level rose due to
melting ice at the end of the last
ice age
Most common type
Examples – Chesapeake
Bay, Delaware Bay, Newark
Bay
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TYPES OF ESTUARIES
2. Bar-Built Estuary
Form when sediments accumulate
along the coast as sand bars and
barrier islands that act as a wall
between the ocean and fresh water
from rivers
Examples – Outer Banks, NC,
Texas Coast,
Long Beach Island, NJ
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TYPES OF ESTUARIES
3. Tectonic Estuaries
Formed when land sank or
subsided due to movements in the
crust
Example - San Francisco
Bay
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TYPES OF ESTUARIES
4. Fjords
Formed when advancing glaciers
cut deep valleys along a coast and
then the valleys were submerged
when sea level rose
Examples - Norway,
Alaska, New Zealand,
Puget Sound, WA
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JQ: Match the type of estuary to its
name or example:
A. Forms when crust
1. ____ Fjord
2. ____ Bar – built
3. ____ Drowned River Valley
4. ____ Tectonic Estuary
shifts/lowers
B. The result of flooded areas
due to melting of ice from
ice age
C. Formed in areas where
brackish water is contained
inside of a sand bar
D. Formed from valleys that
have been carved by
glaciers
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PHYSICAL CHARACTERISTICS OF ESTUARIES
1. Salinity – fluctuates from
place to place & time to time
- organisms that stay in one
place faced with dramatic
changes in salinity
Salty seawater is more dense
and stays on the bottom
Salt wedge of seawater forms under river runoff when the tide
comes in. This layers the salinity.
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SALT WEDGE – high river flow, low tide nutrients & sediments from river enter
estuary
WELL-MIXED – low river flow, moderate
tide – tidal turbulence mixes waters
together
PARTIALLY-MIXED – low river flow,
moderate tide – similar to well-mixed
with deeper channel
FJORD – small surface area, high river
flow, little tidal mixing
REVERSE – little river inflow, high
evaporation
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PHYSICAL CHARACTERISTICS OF ESTUARIES
2. Temperature – varies due to
shallow depths and large
surface areas
– organisms exposed at low
tide face even more drastic
daily and seasonal
temperature changes
3. Turbidity
- large amounts of suspended sediments reduce water clarity
- very little light penetrates water column
- particulate matter clogs filter feeders
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PHYSICAL CHARACTERISTICS OF ESTUARIES
4. Substrate – type of bottom – mostly sand & soft mud
- rivers carry large amount of sediment, organic matter AND
pollutants into estuaries
- infauna have a more stable environment than epifauna
because mud traps the salt
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5. Oxygen - depletion can occur in
the mud or in the water column due
to bacterial respiration (ANOXIA)
6. Nutrients - come from river
runoff and provides for a detritusbased food chain, inverted energy
pyramid increases productivity
7. Water Depth - zones are
determined by the tides, shallow
water restricts large predators
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8. Tides and currents - tidal ebb with river runoff cause net
flushing. Tides transport larvae and nutrients into the ocean.
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Types of estuarine communities:
- typically few species, with many individuals
1. Open Water
- enter and leave with
the tide
- vary with currents,
salinity & temperature
Murky water may limit
primary productivity of
phytoplankton in rest
of estuary
Fishes & shrimps use as nurseries
- take advantage of abundant food and safety from predators
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2. Sea Grass Communities primarily subtidal zones
where sea grasses can
stabilize the substrate
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Leaves of grass slow
currents, provide a place of
attachment to prevent
smothering in sediments, for
hiding places, and for food
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3. Mud Flats - or oyster reefs
- found in lower intertidal and subtidal zones
- bottoms of estuaries exposed at low tide (organisms experience
desiccation, wide temperature changes, predation, salinity changes)
- primary producers are diatoms & bacteria
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•Infauna live on
detritus brought in by
tides and rivers
•Deposit (mud) or
suspension feeders
(sandy)
Organisms include:
•Bivalves
•Burrowing shrimps
•oxygenate sediment
•Fiddler crabs
•Predators (snails, worms,
crabs)
MOST IMPORTANT PREDATORS IN MUDFLATS –
FISHES and BIRDS
•Fishes invade at high tide, birds invade at low tide
Figure 12.10
Wading shore birds most significant predator
•Varying lengths of bills may represent specialization in prey
Example of RESOURCE PARTIONING – sharing of a resource
by two or more species to avoid competition
4. Salt Marshes - also called tidal
marshes, wetlands, swamps or
mangrove communities
- develop when muddy sediments
allowed to accumulate-waves minimal
- muddy bottom held together by
roots
Producers are Spartina (cordgrass)
found mostly in intertidal water
Bacteria in the mud decompose dead
plant material and contribute a large
portion of the detritus in the estuary
Salt excreting leaves provide food
and habitat. Air tubes from the
leaves to the roots help oxygenate
plants living in anaerobic mud.
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Estuaries very productive ecosystems – WHY???
1. Nutrients brought in by tides and rivers
2. Nutrients released by nitrogen-fixing organisms
3. Decomposition of detritus
 most animals feed on dead organic matter
 more energy from decomposers than from
producers
4. Excess detritus exported to the open ocean by
outwelling
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LIVING IN AN ESTUARY – COPING WITH CHANGING SALINITY
(ADAPTATIONS)
Euryhaline – tolerate wide range
of salinities (most)
Stenohaline – tolerate narrow
range of salinities (few)
- limited to upper or lower
ends of estuary
Maintaining salt and water balance is challenging:
- change behavior (hide, close shell, move or swim away)
- develop high salt tolerances (salt-marsh plants), excrete salt,
accumulate water
- osmoconformers –salinity of body fluids vary with the water ex.
Most marine invertebrates like lobsters, mussels, etc
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- osmoregulators – keep salt concentration of body fluids
constant – ex. Most fish (like salmon)
LIVING IN AN ESTUARY – ADAPTING TO THE MUD
Disadvantages
- nothing to hold onto
- low oxygen caused by decay of
organic mater in mud
Advantage
- salinity fluctuations less drastic
Difficult to move through mud –
- Organisms stay put or move slowly
- Clams use siphons
Low oxygen
- some burrowers pump oxygen-rich water into burrow
- some have hemoglobin – high affinity for oxygen
- some can survive for days without oxygen
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Estuaries are usually the first dumping site for pollution and have
been severely damaged by dredge and fill operations.
Estuaries are important because they support a large commercial
seafood industry, prevent coastal erosion, provide recreation .
AND
Estuaries are the
sea’s nursery.
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