Chapter 4
Aquatic Environment

Links for Enrichment and Further Learning

• Oceans online
• National Estuary Program
• Wikipedia Colorado River page

Study Questions / Quiz Prep. (Consult Required Reading and lecture notes for answers.)

1. Clouds. Where does their water come from?
2. What three possible future environmental situations await a rain drop?
3. How long does it take for the entire water content of the atmosphere to be replaced?
4. Define “specific heat.”
5. How does water’s specific heat property influence seasonal temperature changes in aquatic environments?
6. Refer to Figure 4.6 on page 71. At what depth is all red light absorbed (attenuated)?
7. What color penetrates farthest into the water?
8. At a depth of 100 m (about 330 ft.), how much light is left?
9. Refer to Figure 4.7 on page 72. Explain the shapes of the following curves:

• Summer
• Fall
• Winter

10. What is the salinity of the oceans?
11. What is the salinity of freshwater?
12. Give an example of a freshwater environment.
13. Refer to Figure 4.9 on page 75. Explain the shapes of the following curves:

• Summer
• Fall
• Winter

14. Refer to Figure 4.10 on page 75. At what depth is oxygen content at its minimum?
15. The more Co2 in the atmosphere, the <blank> CO2 dissolves in the water.
16. The more CO2 dissolved in the water, the <blank> carbonic acid forms in the water.
17. The more carbonic acid in the water, the <blank> acidic the water.
18. What causes ocean tides?
19. How does the environment change for a barnacle living on a rock in the intertidal zone?
20. Refer to Figure 4.16 on page 81. In an estuary, how does salinity change as you move from the ocean toward the river mouth? Why?
21. In an estuary, how does the salinity change as you move from the surface toward deeper water? Why?

Synthesis (These are not official study questions. But you should try to answer them on your own.)
There is something odd about the situations described below. See if you can identify the problem(s).

1. "Water, water everywhere, but nary a drop to drink."
2. A chemist considers two chemical solutions to be used radiator coolant for cars. Solution A has a very low specific heat. Solution B has a very high specific heat.
3. A fashion designer declares that a new, flaming red wetsuit is "the most chic at 50 feet."
4. Imagine if the moon, over billions of years, has been growing more massive by sweeping up the dust of passing comets.
5. A catfish farm is being built by placing cages at the mouth of the Goober River.
6. It is summertime on clear Lake Ripper. With surface water temperature at 90 degrees F, an amateur scuba diver prepares to explore the lake's bottom at 100 feet deep and chooses not to wear a wetsuit.
7. In an experimental forest plot, a scientist discovers that the decay rates for fallen leaves on the forest floor are different for leaves on the lake bottom.

Open Ocean

A rain cloud deposits salt-free water onto the open ocean. Seawater contains about 3.4% salt.

Long-lasting, freezing temperatures at the high latitudes (Arctic and Antarctic) cause water to freeze. Here, fragments of a continental glacier float near Antarctica.

Tropical ocean water is warm, provides a stable environment for solidified calcium carbonate. Corals, clams and other sea creatures make hard body parts from calcium carbonate salts dissolved in the water. Solidified calcium carbonate tends to dissolve faster in clod water.

Thermal vents on the deep, dark ocean floor. Chemosynthetic bacteria use chemical energy from salts emitted by the vents.

Coastal Ocean

Rocky coastal ocean. Pounding ocean waves scour the rocks of loose debris and steadily erode the continental face.

At low tide along the rocky coast, intertidal pools provide moisture for many animals and algae.

The Mississippi River dumps water, sediments, agricultural chemicals, and city trash into the Gulf of Mexico. Coastal oceans are powerfully influenced by runoff from the continent.

An estuary is a coastal embayment where a freshwater stream meets the sea. In this case, sediments have filled the bay to result in a broad coastal marsh.

A marsh is characterized by large areas of very shallow, slow-moving water.

Terrestrial Water Resources

Upstream, freshwater flows along the river channel as it cuts though the land. Along the way, this water may encounter episodes of fast or slow movement.

A lake. This water ultimately is derived from precipitation such as rain or snow.

Water Circulation Systems

Global water cycle. Energy from the sun heats surface water causing it to evaporate and enter the atmosphere in the form of water vapor. Water condenses into small cloud droplets when it encounters cooler temperatures aloft. Moving air masses carry clouds thousands of miles where moisture falls out of the sky as precipitation.

Global oceanic surface currents. Oceanic surface currents represent water moving in an assortment of gyres. In addition to transporting water, these currents also transport heat from the equator.

The big ocean conveyor. Mixed in with surface currents are vertical ocean currents. This drawing shows that equatorial surface currents collect heat, which is ultimately shed to the atmosphere by the time the surface currents reach thje North Atlantic. Once cooled, the water sinks to the ocean bottom, reemerging ahundred or more years later in the Indian or Pacific Oceans.

Light Penetration

Patterns of light penetration into water.

At about 20 feet deep, this diver's red weight belt is nearly colorless, while the color in his blue flotation vest is solid and true.

Lake Thermal Profiles

Seasonal, lake thermal profiles.

Lake Oxygen Profile

Seasonal lake oxygen profiles (right).

Ocean Oxygen Profile

Oceanic oxygen profile.

Estuary Salinity Patterns

Estuary salinity patterns.