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HYPOXIA OR NOT?
MASTER TEACHER Lola Farmer
GRADES 6-8
OVERVIEW
This lesson provides the opportunity for students to compare and
contrast two estuaries: Long Island Sound, New York, and Laguna Madre,
Texas. They will sequence the events leading to a hypoxic event and decide
whether or not the Laguna Madre is suffering from hypoxia. The students
will identify the interdependence of man with these asterion ecosystems and how
humans have contributed to the situations causing a hypoxic event. They
will be asked to draw conclusions from observing some graphs of biomass created
by Dr. Ken Dunton from the University of Texas Marine Science Institute.
ITV SERIES
Ecology of an Estuary, 101 Polluting
America's Inland Seas
Mystery of the Laguna Madre
LEARNING OBJECTIVES
The student will:
*locate the two estuaries on the map of the United States
*Compare & Contrast Chart
*fill in a flow chart of the events that lead to and maintain
hypoxia
*act out a skit representing one of the four natural processes
that occur in an asterion ecosystem
*identify patterns of data when presented in graphic form: food
chain/energy transfer, role of plants in a H2O environment, hypoxia and
photosynthesis underwater
VOCABULARY
interdependence
hypoxia
metabolic activity
organism
metabolism
food web
hydrogen sulfide
phytoplankton
bacteria
estuary
photosynthesis
decomposition
respiration
ecosystem
zooplankton
food chain
hypersaline
MATERIALS
Compare & Contrast Charts
Interdependence Charts
Hypoxia Flow Chart
Affinity Chart Format
4 sets of skits
Construction paper
Scissors
Tape
Markers
VCR
TV
Remote Control
PREVIEWING ACTIVITIES
In a whole class group format ask students to identify the
societal systems in a community which humans are dependent upon for survival
everyday. Use the Affinity chart format in the appendix at the end
of this lesson to identify systems (examples: transportation, food, water,
housing). Once they have brainstormed all of these systems, have them
develop an interdependence chart showing how these systems are necessary in our
lives. Using the affinity chart format, ask them to brainstorm what
organisms are near and in an estuary (examples: plants, animals, birds,
snails, bacteria). Lead the students through the development of an
interrelationship/ interdependence chart of how these plants and animals are
dependent on each other for survival. During this development of concepts
you will be reviewing functions of each phylum of organisms within and around
the asterion ecosystem.
FOCUS FOR VIEWING
To give students a specific responsibility while viewing say,
"You are going to see video segments from two tapes. As you view
these segments, I want you to identify what humans have done which has altered
the natural interdependence of the water environments and how the water
environments have altered."
Start tape Polluting America's Inland Seas
where a view from outer space of Long Island Sound appears on the screen after
the title of the tape. The narrator is saying, "Viewed from space,
the Long Island Sound looks like a beautiful, pristine body of water." Pause
tape where the bow of the boat is moving through the water and the narrator
is saying, "...Connecticut, with it's wealth of fine harbors, is a boater's
paradise." Ask, "What is this body of water called? (Long Island
Sound.) Ask, "What are the three urban communities that are located
around Long Island Sound? (Long Island, New York City, and Connecticut.)
Locate Long Island Sound on a map of the United States.
Fast Forward tape through the two men talking on the
research vessel to one man pulling cable over "T shaped rope tie" on
boat. The narrator is saying "The Long Island Sound has been
designated by Congress as an estuary of National significance." Play
tape through man manipulating large equipment onto boat. Pause tape
after narrator says, "An estuary is a body of water where salt water from
the ocean mixes with fresh water from rivers." Ask, "Where are
estuaries located?" (Where salt water from the ocean mixes with fresh water
from rivers.)
Fast forward tape past graph labelled "Commercial
Landing of Oysters taken from Long Island Sound 1961 - 1985" through the
segment of men shucking oysters to water coming out of pipe depositing affluent
from water treatment plant into Long Island sound. Play tape where
the water is being deposited into Long Island Sound. The narrator is
saying, "Forty-four sewage treatment plants pour just under 1 billion
gallons of treated sewage everyday into the harbors, bays and rivers of Long
Island Sound." Pause tape at the view of Long Island Sound
small peninsula with house on it. The narrator is saying, "Sewage in
the water means contamination in the clam." Ask, "What happens when
humans pollute the estuaries where lobsters, oysters, and clams live?"
(Pollution in the water means contamination in the shellfish or filter feeding
organisms such as oysters and clams.) As an extension question, ask,
"How is man affected by these animals living in these waters?" (Man
depends on these animals to support the local economy, provide food for many
people and some men even depend on these animals as their sole source of income
for their family. If we eat these animals, we could get sick.)
Fast forward tape to the stern of a white boat in
frame at a dock. The narrator is saying, "How does this treated waste
water actually affect water quality?" Play tape. Pause tape
where water is being flushed down toilet with "N's & P's" flushing
with H2O down toilet. The narrator is saying, "Although our waste is
repulsive to us, to many organisms it is food, nutrients." Ask,
"What value does recycling water into our estuaries have?" (To some
types of organisms, it is food and nutrients.)
Resume tape. Pause tape where the round
phytoplankton is on the screen and the narrator is saying, "These are the
marine organisms that make up most of the living matter in an estuary."
Ask, "What makes up most of the living matter in an estuary?"
(Phytoplankton make up most of the living matter in an estuary.) Ask, "What
do they survive on?" (They survive on nutrients in the
water such as nitrogen and phosphorous.)
Resume tape. Pause tape where a person is walking into
a building. The narrator is saying, "The more nutrients, the more
phytoplankton, the more phytoplankton, the more oxygen." Ask, "Why are
phytoplankton valuable to an estuary?" (They produce the oxygen for the
water environment.) Ask, "Why does there need to be oxygen in the
waters of an estuary?" (So the animals that live in that environment can
breathe.)
Teach: Plants in the waters of an estuary give off oxygen
through the process of photosynthesis. When O2 is released into the water
from plants, it enters the water becoming dissolved oxygen. (DO)
Resume tape. Pause tape where the narrator is
saying, "The larger organisms can no longer survive in the absence of
O2, so they leave." Say, "The scientist just said the larger
organisms must leave the area due to lack of O2. If nutrients from human
waste support the increase of phytoplankton, and phytoplankton increase the
level of O2, why is there an absence of O2 in these waters?" (Oxygen is
used up by metabolic activity, bacteria begin to dominate and form hydrogen
sulfide during their metabolism.) Say,
"Let's view the next segment and see if we can identify
what occurs in an estuary that causes a decrease in the level of oxygen."
Resume tape. Pause tape where there is an underwater
scene of an oyster reef and the narrator is saying, "Oxygen is taken up by
these organisms during this decomposition process." Ask, "What
are the organisms that become abundant in an estuary after a phytoplankton bloom
occurs, and the dead phytoplankton drop to the bottom?" (Bacteria dominate
the environment once the phytoplankton die and drop to the bottom of the
estuary.) Ask, "What are these bacteria doing?" (They are using
up oxygen in the water to decompose the phytoplankton. The result of the
decomposition process is that the bacteria give off hydrogen sulfide gas which
then dominates the underwater environment and suffocated the other living
organisms.)
Resume tape. Stop tape after the narrator says,
"And dangerously low levels of O2 were recorded as far east and Fort
Jefferson." At this time, have the students (individually, in pairs, or in
small groups) complete the worksheet "The Dynamics of Hypoxia" Flow
Chart. They are to sequence the events that lead to hypoxia and fill in
the flow chart.
"Remember that we are wanting to identify what humans have
done which has altered the natural interdependence of the water environments we
are viewing. We have just finished viewing the Long Island Sound water
environment. Ask, "What is the most memorable affect of human presence in
Long Island Sound? (The affluent deposit of waste water into the Long Island
Sound waters and the occurrence of hypoxic events in the area.) Say, "Now
we are going to view another ecosystem that has also been influenced today by
man's decisions in the past. This estuary is located between Corpus
Christi, Texas, and Port Mansfield, Texas, between Padre Island and the mainland
of Texas."
Locate the Laguna Madre on the United States map.
Start tape Mystery of the Laguna Madre
after introduction where the words "The Mystery of the Laguna Madre"
come into view over the water and center over the beach area through the use of
computer graphics. The narrator is saying, "Of the eight bay systems
along the Texas coast, the ecosystem formed by the Upper Laguna Madre and Baffin
Bay are unique." Pause tape where there is a view of a beach
and the narrator is saying, "One of only five hypersaline estuaries
in the world." Ask, "What four characteristics of this environment
cause the Laguna Madre to be an estuary that is hypersaline?" (It is not
fed by freshwater rivers; no exchange with the Gulf of Mexico; lots of
evaporation; and hot, windy climate.)
Fast forward tape to a man pouring H2O off of a soil
sample. Dr. Paul Montagna is in the next screen, and you want to hear what
he has to say. He is saying, "The Upper Laguna Madre is a hypersaline
environment, and it's hypersaline because evaporation exceeds fresh water
input." Pause tape where the screen in showing an underwater
view of the Laguna Madre and the narrator is saying, "The Laguna's seagrass
beds are a nursery for juvenile fish, a place holding a lot of food and a place
where they can hide from predators." Ask, "How do the seagrass
beds benefit fish populations in this environment?" (The seagrass beds
serve as a nursery for fish in planktonic stages of development, provide lots of
food for these growing animals, and serve as a place for these growing animals
to hide from predators.) Ask, "Ultimately, who benefits from these seagrass
beds being in place in the Laguna Madre?" (Man.)
Fast forward tape through the third screen of Dr.
David McKee (man with a blue shirt on and a beard) to the view of the seagrass
bed immediately following Dr. McKee's third time on the screen. The
narrator is saying, "With its seagrass beds, the Laguna Madre is a vast
submerged wetland." Pause tape where the screen says
"The Laguna Madre is a series of hypersaline lagoons." It
includes the Upper Laguna Madre and Baffin Bay, the Lower Laguna Madre and
Laguna Tamaulipas in Mexico. Ask, "What other forms of life
depend on the health of the Laguna Madre, other than fish?" (Birds such a
skimmers, pelicans, cranes and ducks.) Ask, "Why do these birds stop
here?" (The birds stop to rest and feed on the animals found in the
seagrass beds.)
Fast forward tape to the screen with the house over
the water to the beach view. The narrator is saying, "Right now,
scientists are evaluating the affects of an unprecedented natural event."
Pause tape where there is an underwater view of brown tide. The
narrator is saying, "So murky, that sunlight was obscured and the seagrass
has had a hard time with photosynthesis." Ask, "What will happen
to the sea grasses if they don't have enough sunlight to carry on
photosynthesis?" (They cannot produce the sugar necessary to grow on.
They will not produce oxygen for the water environment. They will die.)
Ask, "If the Dissolved Oxygen levels decrease in the water, what else
happens?" (All organisms in the water that depend on the oxygen supply will
also die or move away from this area.)
Fast forward tape (three screens only) to view of
Laguna Madre grass beds at low tide to the underwater view of brown tide.
The narrator is saying, "If the brown tide goes away, the sea grass will
probably rebound." Pause tape where the boat is on the Laguna,
people are fishing. Dr. Paul Montagna is saying, "A food chain rests
on the things on the bottom, if you pull out a card from the bottom, the whole
thing falls down." Ask, "What is Dr. Montagna saying that is
occurring in the Laguna Madre with his simile about a 'house of cards'?"
(If you destroy the environment that supports the base of the food chain, the
whole system collapses.)
Fast forward tape through the interview with Cliff
Webb to the barrel in water near shore. The narrator is saying,
"The same shallowness and lack of circulation that make the Laguna
vulnerable to natural pressures, also come into play with man made
pressures." Pause tape where white pelicans are standing on sand of
island and the narrator is saying, "The Laguna remains relatively
pristine." Ask, "Why does waste stay in the Laguna?"
(There is no circulation, and lots of evaporation in the Laguna Madre.)
Fast forward tape to Ernie Butler's shrimp boat in
water (approximately 18 screens). Ernie Butler is silhouetted on the stern
of a shrimp boat working on the net. He is wearing a red cap and white
shirt. The narrator is saying, "Ernie Butler grew up on the
Laguna." Resume tape. Pause tape where the screen is showing
the John F. Kennedy Causeway across the Laguna Madre and the narrator says,
"Montagna lists the causeway as the leading artificial pressure on the
Laguna." Ask, "What affect has the causeway had on this
estuary?" (Water flow has been dammed. Seagrass beds and sandy
patches have been replaced with murky sediment and stagnate water.)
Resume tape. Pause tape to where cabins are on
the Laguna. The narrator is saying, "And the Laguna is being made to
serve as a sewer." Ask, "What happens when human waste is dumped
into an ecosystem?" (Phytoplankton blooms occur due to the increase in
phosphorous and nitrogen.)
Fast forward tape through Michael Ray GCCA/ Stocking
fish camera underwater to Dr. Paul Montagna. He is saying, "But
my main concern has been the habitat's ability to maintain healthy
populations." Stop tape where Michael Ray is standing in front
of the GCCA/CPL bulletin board entitled "Gulf Coast..." with
pictures. He is saying, "It won't do any good if there's not a
suitable habitat for those fingerlings to thrive, to grow and live." Ask,
"What pressures are causing the ecosystem to degrade?" (Pollution,
human waste, and the earthen dam John F. Kennedy Causeway built in 1950 and the
emergence of the brown tide.)
POSTVIEWING ACTIVITIES
At this time, the teacher should pass out the Compare and
Contrast chart found in the appendixes to this lesson. The students should
be able to work in small groups to compare notes and use other resources in the
room such as maps to complete the chart.
Once they have completed the compare and contrast chart, pass
out the set of graphs furnished by Dr. Ken Dunton, University of Texas
Marine Science Institute in Port Aransas. All this data is taken from his
study of the affects on the seagrass beds in the Laguna Madre since the
occurrence of the brown tide. The students should be given the opportunity
to peruse these graphs for about a minute. Have them to share with a
partner what they think these graphs are showing us, for about 30 seconds for
each person in the pair. Then have 4 or 5 volunteers share what they
believe the graphs are depicting. Then have the students look at each
graph independently and answer the following questions related to each graph.
They may raise their hands in a whole group class question and answer session.
Questions: What is the title of this graph/table? (Answers
will vary.) What is the independent variable? (This will always appear on the
X-Axis.) What is the dependent variable? (This variable will always appear on
the Y-Axis.) What does this graph/table show us? (Answers will vary.) What
pattern exists in this graph/table? (All tables/graphs are showing a
pattern of decline in light penetration, biomass, etc.)
As a whole class activity, have students write a statement
that explains what is happening to the sea grass beds in the Laguna Madre
according to the patterns that exist in the graphs/tables.
FINAL ASSESSMENT
Directions: Make up a skit that acts out the processes explained
in the following paragraphs.
Divide class into four groups. Each group will be given
scissors, construction paper, markers, tape. Each group will be given the
handout with paragraphs of information.
Group I "The Dynamics of Hypoxia"
Nitrogen and phosphate are added to a water environment. These added
nutrients provide food for the phytoplankton in the water. These
phytoplankton reproduce at a rapid rate. The water becomes the color of
the phytoplankton bloom. The phytoplankton die and fall to the bottom of
the water environment. Bacteria begin to do their job of decomposition.
Due to the added nutrients in the water for bacteria, the bacteria begin to
reproduce at a rapid rate. During the metabolic process the bacteria
consume dissolved oxygen out of the water and give off hydrogen sulfide.
Mobile organisms move to oxygenated waters. Immobile organisms are forced
to suffocate where they live. The organisms die. The bacteria become
the major source of living matter in the water environment. A deficiency
of dissolved oxygen exists.
Group II "The Brown Tide"
The Brown Tide is a brown algae that is common in all salt water estuarine
systems. They are a phytoplankton. During the winter of '89/'90, a
hard freeze came through the coastal bend in conjunction with a low tide.
This phenomenon caused the ground to freeze. The ground of the Laguna
Madre contains benthic & other organisms. Examples: worms,
euglena, sand dollars, starfish, squid, small fish. When the ground &
shallow waters froze, the organisms died. Bacteria became abundant due to
the increase in dead organic matter. During the decomposition process, the
bacteria give off hydrogen sulfide. A characteristic of the brown tide is
that it can thrive and survive in an environment rich in ammonia. The
brown tide phytoplankton bloom blocks out sunlight from the sea grass beds in
the Laguna Madre. When the sun light is blocked, the sea grasses are not
able to go through the process of photosynthesis, giving off oxygen in the form
of dissolved oxygen into the water or store sugars in their roots so the plants
can grow. This results in more dead grasses, reduced habitat for small
organisms, more organic matter to decompose, more hydrogen sulfide in the
ecosystem.
Group III "The Interdependence of Organisms and their
environment in an Estuary"
All phytoplankton are primary sources of energy. Primary sources
of energy convert radiant energy from the sun to sugar through the process of
photosynthesis. The byproduct of this process is the release of oxygen
into the water providing dissolved oxygen for the animals in the water
environment. Animals from the open water return to the nursery area to lay
their eggs forming zooplankton. Zooplankton eat the phytoplankton and
nutrients from inflow of river water. Larger zooplankton are eaten by
small fish, squid, and other animals. The smaller fish, crabs and shrimp
are eaten by the larger fish & birds.
Ultimately, man harvests the animals from the estuary to sell on the market.
Group IV "Photosynthesis & Respiration in Plants"
Plants convert radiant energy from the sun into sugars which they store in
their roots. During the daylight hours, the plants are continuously giving
off oxygen and producing glucose. Once the sun goes down, the plants begin
to use the sugars they have stored in their roots to grow. Throughout this
process, the plants are taking in oxygen to assist in the metabolic process of
breaking down the glucose and the byproduct of this process is CO2. When
the sun comes up, the plants begin this cycle again.
ACTION PLAN
Have students write to one of the scientists who were on the
tape. The students should ask the scientist to send some data of what they
have discovered since this video tape was made.
Dr. Paul Montagna
The University of Texas Marine
Science Institute
750 Channelview Drive
Port Aransas, Texas 78373
Once the data comes in, have the students write a summary of
the information they received from the scientists. Have them present their
conclusions to the class.
Invite Dr. Montagna, Dr. McKee or a GCCA/CPL representative
to come to the classroom and discuss their knowledge of the brown tide situation
as it relates to the Laguna Madre. Have a forum discussion panel.
Take a full day field trip to the GCCA/CPL fisheries sight,
the Laguna Madre and the University of Marine Science Institute in Port Aransas.
Focus for the Field Trip: "What is happening today, that may ensure that
the Laguna Madre remains pristine and continues to function as a healthy
ecosystem?"
EXTENSION
Have interested students find home pages or current research on
the WWW which will bring more information to the classroom about the situation
both Long Island Sound and the Laguna Madre are facing.
Have students research the issues surrounding the Laguna
Madre and Long Island Sound and have them present solutions to the situations
these ecosystems are facing.
Have students write a compare and contrast essay explaining
the similarities and differences between the two ecosystems.
"The Dynamics of Hypoxia"
Flow Chart
Sequence the following events and fill in the flow chart.
____ Nitrogen and phosphorous added to H2O.
____ Bacteria decompose dead phytoplankton.
____ Immobile organisms die due to lack of
dissolved
oxygen (CD).
____ Bacteria take in DO, give off hydrogen
suifide(H2S).
____ Phytoplankton bloom.
____ Mobile organisms leave area
____ Ohytoplankton die
____ Bacteria decompose organicmatter.
Flow Chart of Hypoxia
Compare & Contrast
Long Island Sound, NY
Laguna Madre, TX
| Location in United States |
Effect of Brown tide on underwater
light for the shoal grass (Halodule wrightii) in Laguna Madre
Pre-Brown Tide Post-Brown Tide
Total Annual Light
>5000 units <2400 units
(moles photons m-2 yr-2)
Daily Number of Hours
> 5 hrs
< 2 hrs
for maximum photosynthesis
(Hsat)
Percent Surface Light
> 40 % < 18 %
Source: K.Dunton, University of Texas
Marine
Science Institute
ANNUAL LIGHT REQUIREMENTS
(mol photons m-2 yr-1)
| |
Arctic Kelp
(Laminaria solidungula) |
South Texas Seagrasses (Halodule wrightii) |
| Surface PAR |
6100 |
12,500 |
| Underwater PAR |
45 - 50 |
2200 - 2400 |
| % SI |
0.7 - 1.0 |
18 - 20 |
VARIATIONS IN Hsat(h)
| YEAR |
SITE |
| LM - 151 |
EF |
| 1989 |
5.2 |
nd |
| 1990 |
1.4 |
3.3 |
| 1991 |
2.8 |
3.0 |
| 1992 |
1.6 |
4.5 |
Laguna Madre
Site 151
Laguna Madre
 Source:
K.Dunton, University of Texas Marine Science Institute
Updated: April 01, 2008
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