Teacher's Section: Oceanography Unit

Oceanography Unit

Introduction

Before students can understand an ecosystem, they must first understand the physical features that drive the biology of that ecosystem. In marine biology, discussions and activities on oceanography make learning the features of a marine ecosystem pertinent and applicable. This is a description of the activities done to accomplish the three-week unit objectives.

Objectives

describe and label the ocean topography and zonation and how they are formed.

describe the properties of water and how those properties form the marine environment

describe the features and formation of waves, currents and vertical water movements

apply oceanographic principles as to how marine organisms adapt, survive and reproduce

apply oceanographic principles as to why marine ecosystems are the way they are

Ocean Topography and Zonation Activities

Days One and Two - provide unlabeled diagrams of the following and label during a class discussion, with the teacher using an overhead of the diagrams:

Equatorial view of the oceans and continents (Fig. 1.8)
Top-view and side-view of large scale features of the seafloor (Fig. 1.9)
Marine climactic zones (Fig. 1.18)
Classification of marine environment zonation (Fig. 1.30)

(Sumich, 1992)

During the labeling process, discuss why there are large-scale features (plate tectonics), climactic zones (planet tilt and heating), and environmental zones (water depth, substrate/no substrate, light availability).

Possible Discussion Questions

1. What causes underwater mountain chains and trenches?

2. What is plate tectonics? How does it work?

3. What was "Pangea"? What is the evidence for plate tectonic movement?

4. How do plate tectonics affect marine biology?

5. What does the tilt of the planet cause?

6. How does tilt cause seasons?

7. What causes the earth to be divided into temperature zones?

8. How does the angle of the sun affect the heating of the earth?

9. What are the characteristics of shallow areas? What causes them?

10. What are the characteristics of deep areas? What causes them?

11. What types of organisms could live in those places? Why?

Days Three--Five

after dividing the students into four different groups, (for each diagram), allow the students to use teacher- or student-provided arts and crafts materials to construct scale 3-D models of their diagram, evaluated according to a teacher made rubric. Present to the class.

Properties of Water Activities

Day One

have a class discussion reviewing the physical properties of water, allowing the students to come up with the following list: boiling and melting points, surface tension, density, evaporation/freezing, solvent power and heat capacity. Review and discuss each property, leading into a discussion of how each property is important to biological processes and why it might be important to the marine environment in forming seawater and what problems it might create for life. Create a table on the board summarizing the information.

Possible Discussion Questions

1. What are some properties of water?

2. At what temperature does water boil? Melt? What causes these two points?

3. How can these two points be raised or lowered? How could that affect marine life?

4. What is unusual about the solid state of water? How could this be important to life?

5. What is evaporation? How would rates of evaporation affect ocean water?

6. Why would evaporation be important to marine life?

7. What is surface tension? Viscosity? What causes these phenomena?

8. How might surface tension and/or viscosity affect marine life?

9. What is density?

10. How would something more or less dense in pure water behave?

11. What could cause water to be more or less dense?

12. How could changes in density affect marine life? Why might it be important?

13. What is a solution? Why is water a good solvent? Why might this be important?

14. How might changes in salinity affect marine life? Why?

15. What is heat capacity? Why is the ability of water to absorb well important?

16. How might heat capacity affect marine life?

Days Two--Five

Do a learning cycle on the salinity/temperature/density relationship of seawater. Follow up with a discussion of the thermocline.

The Ocean in Motion Activities

Day One

have a class discussion to come up with the different ways in which water moves after allowing "think time" for the students to write their ideas down. Allow the students to speculate as to what causes the different types of water motion, how they help to form the physical environment, why they are important to the marine ecosystem and what problems they create for life. Merely discuss ideas—do not credit or discredit student answers. Organize the students into groups, assign each group a water motion type and instruct them on the expectations of how to do a graphic display. They will also devise a handout to give to the class during their presentation.

Possible Discussion Questions

1. How does water move? Does it just move horizontally?

2. What causes it to move? Just the moon? Just the wind? How?

3. What different factors about the wind could cause different size waves?

4. How do waves shape the physical environment? Why are they important?

5. What makes currents different from waves? What causes the difference?

6. How do currents shape the physical environment? Why are they important?

7. More Possible Ocean in Motion Discussion Questions

8. What would cause water to sink? Why?

9. Why would sinking water be important to marine life?

10. What would cause water to rise? Why?

11. Why would upwelling water be important to marine life?

12. What possible problems could these water motion types create for life?

Days Two—Five

allow the students to research and accomplish their graphic displays and present to the class.

Ocean Topography and Zonation Notes

A. Plate Tectonics

1. Earth’s crust is divided into a number of giant irregular plates

2. each plate is bounded by oceanic trench and ridge systems

3. new oceanic crust is formed continually along the axes of oceanic ridges and rises. As they grow, they move laterally in opposite directions, carrying bottom sediments and attached continental masses with them. (Fig. 1.5)

B. Global Temperature Gradient

1. Earth is tilted 18° , so one pole is tilted more directly to the sun than the other. The opposite pole is directed six months later.

2. Angle of received sun determines how much the Earth is heated. The more of an angle, the less heat; the more overhead, the more heat.

A. Topography
1. continental shelf - lowered shoreline of landmass. It is smooth and gently slopes seaward
2. shelf break—outer edge of shelf (120-200m)
3. continental slope—steep slope; boundary between the continental mass and the true ocean basin.
4. abyssal plain—flat, sediment-covered area (3000-5000m depths)
5. ridge and rise system—underwater mountain chain : isolated peaks form occasional islands (such as Iceland)
6. trench—areas deeper than 6000m. They are highly pressurized and often hot due to volcanic venting and they are important in seafloor spreading and plate tectonics.
7. seamounts—oceanic volcanic mountains that haven’t reached surface level
8. islands—volcanic masses above sea level. Often topped (atolls) or fringed (reefs) by coral areas.

Water Notes

A. Introduction

crucial to survival

80-90% of an organism

provides buoyancy and body support (no heavy skeletons)

important medium for metabolism

Pure Water

1. Not just liquid—large quantities as ice and vapor

2. asymmetrical dipole/causes Hydrogen bonds and uniqueness

3. viscosity and surface tension

Hydrogen bonds between molecules resist external forces (viscosity), thus reduces sinking, increases drag
forms flexible molecular "skin" (surface tension), which can support
both increase as temp decreases

4. density/temperature relationship

density increases as temp decreases.
however, switches at about 4° C, where the solid ice is LESS dense than the liquid
otherwise, oceans would freeze from bottom to up and winter survival would be impossible

5. heat capacity

water can absorb and give up heat energy without a large temp change
takes lots of heat to increase temperature, so large bodies of water can resist temperature fluctuations

6. solvent action

small size and polarity of water can easily pick apart most ionic salts and causes dissolving

.

A. Seawater About 3.5% is dissolved solutes from rocks, soil, and organisms as inorganic salts, dissolved gases, and organic compounds (detritus and others)

1. salinity—total amounts of dissolved salts in parts per thousand.

0 ppt at river mouths; Red Sea 40 ppt; varies little out in the open ocean.
Major ions: Cl^- Na⁺ SO₄^2-Mg²⁺ Ca²⁺ K⁺ HCO₃^- PO₄^3-NO₃^- (all needed for growth and maintenance)

2. temperatures

Life can be sustained from subfreezing to boiling, but mostly 0° to 30° C.
Saline water resists freezing (freezing point depression).
Boiling water at deep sea volcanic vents.

3. gases

lower temperatures = greater gas solubility (N₂, CO₂, O₂).
CO₂ mostly in the form of the weak carbonic acid, acting as a buffer system to keep ocean pH 7.5 - 8.4
O₂ comes from atmosphere and surface plants, so deep oxygen is rare and is replenished by slow diffusion and by cold (dense) sinking water.

Ocean in Motion Notes

A. Introduction

The ocean is always in motion.

This minimizes variations in salinity and temperature.
Disperses organisms and reproductive products.
Body wastes dispersed, essential nutrients are replenished.
sun is the driving force behind all oceanic circulation.

B. Waves

1. Waves are vertical disturbances of surface in a series of crests and troughs.
2. Solar heating of atmosphere causes winds, winds produce waves.

3. Size and energy of waves dependent upon wind’s velocity, duration and fetch.

4. Only the shape of the wave advances as an energy transfer. The molecules themselves travel in vertical circles.

C. Surface Currents

1. Currents are large-scale horizontal movements of water molecules.
2. Occurs in regions where winds are constant in direction and velocity.
3. Deeper water loses momentum due to viscosity at about 200m.
4. Due to Coriolis Effect, currents are deflected clockwise in the Northern Hemisphere from the wind direction, therefore currents generally flow from east to west.
5. Continental masses obstruct east-west flow, therefore there are countercurrents and continental boundary currents. (Fig. 1.25)
6. Patterns are general (Fig. 1.26), yet specific (Fig. 1.27).
7. El Niño is a famous warm-water current that causes changes in world-wide weather patterns.

D. Vertical Water Movements

1. Sinking caused by denser (colder and more saline from evaporation) water

also oxygen-rich; carries oxygen down to anoxic areas.
major sinking in colder latitudes (Fig 1.28)

2. Upwelling occurs in certain areas where the thermocline is favorable (next to non-existent).

upwelling waters are nutrient-rich; well-known fisheries are locations where large-scale upwelling occurs.

(figures 1.9, 1.5, 1.8, 1.18, and 1.25-1.29 from: Sumich, James L. Marine Life. Wm. C. Brown Pub, 1992.)