Hypoxia and the Oxygen Squeeze
Duration
2 class periods (1 for activity and questions, 1 for mini observatory extensions)
Theme
Exploring how hypoxia occurs and its effect on marine life.
Objectives
Students will:
 Explore the role of dissolved oxygen in the marine environment.
 Explore and interpret the oxygen demands of different taxa
 Explore the mechanisms of hypoxia and oxygen renewal
 Use Ocean Networks Canada Data to investigate inter-relationships between dissolved
oxygen and other factors in different locations
Vocabulary
Hypoxia: Low oxygen; typically less than 1.5 ml/l
Anoxia: No oxygen
Asphyxiate: To be deprived of oxygen, usually to the point of death
PLOs Addressed (Activity + Extensions)
Grade(s)
8, 9, 10
8
8
10
Curriculum
Organizer
Processes of Science
Physical Science:
Fluids and Dynamics
Prescribed Learning Outcomes
A1 Demonstrate safe procedures.
A2 Perform experiments using the scientific method.
A3 Represent and interpret information in graphic form.
A4 (Grade 8 A5) Demonstrate scientific literacy.
A5 (Grade 8 A6) Demonstrate ethical, responsible, cooperative behaviour.
A6 (Grade 8 A7) Describe the relationship between scientific principles and technology.
A7 (Grade 8 A8) Demonstrate competence in the use of technologies specific to investigative
procedures and research.
C6 describe the relationship between solids, liquids, and gases, using the kinetic molecular theory
C9 recognize similarities between natural and constructed fluid systems
Earth and Space
Science:
Water Systems on
Earth
D3 describe factors that affect productivity and species distribution in aquatic environments
Life Science:
B3 explain various ways in which natural populations are altered or kept in equilibrium
Sustainability of
Ecosystems
10
Physical Science:
Chemical Reactions
and Radioactivity
C3 distinguish between organic and inorganic compounds
Background
Hypoxia means ‘low oxygen’. All fish and animals need to breathe in oxygen as part of the
process of respiration and in doing so, remove oxygen from their environment. Bacteria
decompose organic matter and also respire and use oxygen in their environments. Unlike the
atmosphere, which is about 21 percent oxygen, water can become depleted of oxygen when
respiration occurs in parcels of water which is not mixing with more oxygenated water. Oxygen
can enter the water in a number of ways, but all inputs takes place on or near the surface;
deep water gets its oxygen from oxygen rich surface water that “sinks” due to its temperature
or salt content. A small amount of oxygen enters the water via the air by atmosphere
exchange, but this is only within the first few meters. The majority of the ocean’s oxygen is
refreshed by wind and wave action, or as a byproduct of photosynthesis.
Hypoxia occurs when the oxygen in an environment falls below about 1.5 ml/l of oxygen. When
oxygen levels are low, it can cause stress on the animals in this environment. Some animals
such as jellyfish, have evolved a tolerance to low oxygen levels, while others, like crabs may be
forced out of the environment. If an animal is unable to get enough oxygen and cannot escape
the environment, it may asphyxiate and die.
Hypoxia can occur seasonally in areas where there are few mechanisms to refresh oxygen
levels, such as Saanich Inlet on the coast of Vancouver Island. Most of the year here, animals
are not found below 95m, there simply isn’t enough to breathe.
Hypoxia can also occur accidentally, for example, due to uncontrolled plankton blooms. In a
process known as eutrophication, an excess of nutrients (usually from human activity) enters
the water making it favorable for plankton to bloom. Although the phytoplankton initially
creates an abundance of oxygen as a byproduct of photosynthesis, as they die and decompose,
bacteria take oxygen from the environment. On this large scale, the bacteria use up most or all
of the oxygen in the water, rendering it hypoxic.
Materials:
200 cotton balls or other small counters
Large playing space
Hula hoops
Optional Creature cards, one per participant.
Procedure
Preparation
1. Spread the cotton balls out in a large playing area.
2. Place a few hula hoops into the playing space as well
3. See optional: Make creature cards, each needing a different oxygen level.
Activity
Discuss with students the needs of all living things to get oxygen from their environment. You
may also wish to discuss oxygen tolerances and eutrophication.
Activity 1
1. Take the students to the playing field, and explain that they are now animals within an
ocean ecosystem (the playing field).
2. The cotton balls represent oxygen molecules, and they will need to collect oxygen in
order to survive. For now, they can ignore the hula hoops.
3. Have the participants line up along one edge of the playing field. On GO, the players
enter the environment and pick up a cotton ball (oxygen) and then return to the start.
4. Discuss with students: was there enough oxygen for everyone? Did anyone struggle to
complete the task? Why or why not?
5. Repeat the action until one student is not able to get a cotton ball. Explain that the
environment has been depleted of oxygen, and is unable to support that student, and
thus, they have died ( or if you prefer, too exhausted to keep playing). That student
then sits out until the game is over.
6. Repeat the activity again, reminding students that if they are unable to get a cotton ball,
they have died (or are exhausted) and are out.
7. Optional: assign each student an animal specific to the environment, with each
assignment, the student is required to pick up a certain number of oxygen need to
survive (written on the card). For example, one student may be a shark, and they need
7 cotton balls to advance to the next round, a squat lobster might need 1 per round.
8. Keep playing until the playing field is devoid of oxygen. Discuss with the students, did
they notice any trends in the activity? If they were specific animals, did certain ecotypes
die off before others? Once large predators are gone, did the ecosystem support the
smaller animals for an extended period?
Activity two:
1. Explain to the students that they are now in a new environment (the hula hoops are still
in the field). In this environment, there is continual oxygen, but only in certain areas
(the hoops).
2. Invite students to enter the playing field and find a hoop of their choosing.
3. Tell the students that on “GO”, they must find a new hoop. Yell “Go” a few times, to
force the students to move hoops. You can make it more game like by playing music –
if the students are outside a hoop when the music stops, they did not make it to an
oxygen zone, and died.
4. After a few rounds, explain to the students that some of the oxygen zones have now
stopped producing oxygen, and are not able to support them (remove a few hoops). Tell
the students in the removed hoops they can move to a new hoop to find oxygen.
5. Continue playing with fewer hoops – remind the students that they must have most of
their body in a hoop in order to survive to the next round!
6. Continue to remove hoops, a few at a time, until the students are forced to squish into
one hoop!
7. Allow the students to try and squish into one hoop, being careful to make sure they are
doing so safely.
8. Debrief this activity, what was it like trying to get everyone into fewer hoops?
Discussion





Explain what happen in activity one in terms of abiotic and biotic factors in the
environment
Why did some animals last much longer than others in the same environment?
How would limiting an animal’s living space put stress on that animal to survive?
How can environmental conditions affect the success or failure of life in an area?
How might populations respond to limited oxygen? How might this benefit one species
while impacting another?
Grade 8

A water molecule is made of one hydrogen atom and two oxygen atoms, why can’t the
animals just breathe that?
Animals, like people, can only breathe oxygen that is not bound to another element.
Known as free oxygen, this is the ‘extra’ oxygen in the water. Gills and membranes
cannot break down molecules to get oxygen, so they must use what is present in the
water. Once this is gone, the animals will have nothing to breathe.

In this activity (1 or 2), which factors limited the number of species and individuals
present?
Oxygen (both the amount available and the individual needs of each animal) was the
main factor that limited species, though they may have also been limited by the shape
of the environment.

Using these activities and what you already know, which factors may affect species
distribution this environment?
Availably and distribution of oxygen, as well as availability and distribution of food and
predators. The landscape may also play a role as it may prevent oxygen renewals.
Grade 10

In what ways was the population altered during this activity?
As oxygen levels (and spaces) declined, animals were forced to “die off” or leave the
environment.

Which factors would need to change (and in what way) to achieve equilibrium between
the population and the environmental factors?
To reach equilibrium, the animals would need to consume oxygen in an equal rate to the
renewal of oxygen. If the consumption of oxygen exceeds the rate of renewal, the
animals will eventually die. If consumption is below the rate of renewal, this may make
it possible for other animals (such as predators) to enter the environment.

What was the relationship among the biotic and abiotic factors in this environment?
How did they change over time?
In this example, the biotic factors were dependent on abiotic oxygen, or abiotic
landscapes. Over time, as the oxygen (or livable space) was depleted, the animal
population also declines.

Would it be possible for humans to intervene (altering either biotic or abiotic factors),
and in what way?
Answers may vary.
Mini Observatory – All grades
Part 1
1. Brainstorm with the students: How might hypoxia impact the marine landscape? What
evidence (observable and data based) would you expect to see in a hypoxic
environment? Is hypoxia or even anoxia, guaranteed to have a negative impact on the
environment? Are some animals able to adapt to this conditions? What adaptations
might you expect to see?
One thing to keep in mind is the role of metabolic rate in the needs of animals. Metabolic rate,
or the amount of energy used to stay alive (for example, for internal organs to function, nerves
to run) is correlated with the respiration rate. Animals that have a lower metabolic rate, tend to
have a lower respiration rate. This means they need less oxygen to survive. In some animals,
temperature plays a large role in metabolic rate. For example, most fish are poikilothermic,
which means that their body temperature varies with their surroundings. In the deep ocean the
cold keeps their demand for oxygen low, because their metabolic rate is low too. This can
allow large fish to survive in areas with very low oxygen- they simply don’t need as much to live
comfortably.
2. Distribute the graphs from Barkley Canyon April 1 – Aug 27h. What do students notice
about the graph? This data is from approximately 385 meters depth.
a. Students may notice that over the 4 months, the water is consistently low in
oxygen, to the point of being at the defined level of hypoxia.
3. Draw the student’s attention to the slight dip in the graph, around June 1st to Aug 1st.
Explain they are going to take a closer look at that time period. Distribute the graph
from June 4- Aug 27. What do they notice about the oxygen levels? What biological
factors might they expect to see in this environment? What changes do they predict
might happen from June to Aug? What species do they predict to see more of when
oxygen levels are higher or lower? Remind the students that in this data, the changes in
oxygen are quite small – approximately 1 ml/l. How does that impact their predictions
about biology?
4. Next have the students selected 2 dates from the low period (approximately June 1st to
July 5th) and 2 dates from the high period (approximately July 16th- Aug 16th), that they
wish to view on camera. Have them brainstorm a list of questions and predictions for
the video data.
a. Log into Ocean Networks Canada’s SeaTube Pro using the Username and
Password provided to you.
b. If your page does not immediately display the NEPTUNE Observatory (see name
in upper left of page), from the green menu bar at the top, select a NEPTUNE
Observatory by clicking on “Tools”, select “Network Preference: […]”, and choose
“Switch to NEPTUNE Observatory”.
c. Make sure you are operating SeaTube Pro by clicking on “SeaTube” on the green
menu bar.
d. On the sidebar on the left, click the “+” next to “Barkley Canyon” to expand the
menu, and then click the “+” next to BC Upper Slope POD2. Choose “2014”, then
“June (or August)” and then any date in that range (the same date you’ve
selected form the graphed data). Click on a time period of your choice, but be
careful to select the same time period for all 4 comparisons.
Note: structures seen in the video are experiments being monitored by different
researchers. Your students are encouraged to comment on these structures and
to follow their progress in subsequent videos.
5. As the students watch the videos, encourage them to write down as many observations
as they can. Encourage them to watch the videos at least twice to get a good view of
everything. During the viewings students should be comparing as many factors between
the 2 time periods as they can. For example, do they notice an increase of animals with
an increase in oxygen? Do they notice different behaviors with different oxygen levels?
For example are the animals moving, lying down, and moving slowly? Quickly?
6. Have the groups discuss their findings. Did students who selected the same day reach
the same conclusions or questions? Why or why not? Discuss with students, why might
only 2 videos (per day) leave them limited in the conclusions they can draw? Would it be
necessary for them to watch every video that day to make a solid conclusion? What
other evidence might they use? Could restricting themselves to one species help make
stronger conclusions? How so?
Extensions


Have the students compare their data with a deeper location, such as POD 1, which is
set at 985m. This area is anoxic, with oxygen levels regularly below .35 ml/l. What
animals do they predict will appear here? What questions do they have about the
environment?
Monitor the data from your local observatory. Can you observe changes in your local
environment in relation to oxygen levels? What is the threshold for these animals? Do
they seem to be impacted when oxygen concentrations are well above hypoxic, but are
lower than other times of year for that area?