Exam 3 lecture 2

Nyberg BioS 101 UIC

1

Aquatic ecosystems

All life is dependent on WATER.

Salt- and fresh- water ecosystems have important differences.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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READING ASSIGNMENT

• Chapter 50.2

• A review of the Water lecture, x1 05, may help to understand this lecture.

• Your text does not describe the impact of humans on aquatic ecosystems.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

3

AQUATIC ECOSYSTEMS

• Freshwater

  • Lakes and Ponds

  • Wetlands

  • Streams and Rivers

• Saltwater

  • Estuaries

  • Oceans

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Water Cycle

• Rain drops condense out of air when water vapor is saturated as temperature cools.

• Ice and Groundwater are big fractions of the earth’s freshwater.

• Rivers transport materials, including ions, to the ocean.

• Energy from sun evaporates water.

Speaker Notes:

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Dust can get into the atmosphere. It can take a long time to settle out.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

5

Freshwater versus Saltwater

• Rain has dissolved gases, i.e., CO2, that make it acidic, but no mineral cations (except from dust).

• Saltwater is about 3% salt and has many cations.

• Cells of organisms have a concentration of cations less than saltwater, but greater than freshwater.

• Organisms in freshwater have to pump water out of their cells, while organisms in saltwater have to do work to keep water inside their cells.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

6

Life evolved in Saltwater

• Among the reasons life is thought of have evolved in saltwater is:

  • Most water on earth is in the oceans

  • Many phyla of animals live in saltwater and fewer live in freshwater

Speaker Notes:

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To keep salt water fish in an aquarium one needs ocean salt (same composition as the ocean) not just table salt.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

7

Water density and lake turnover

• Water is most dense at 4° C, e.g., ice floats.

• In temperate areas, the cold surface waters reach the same density as the bottom water in the spring and the water is mixed by wind.

• In fall the surface waters (with O2) sink to the bottom of a lake as they reach 4° C, bringing dissolved oxygen to the bottom.

Speaker Notes:

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Density changes in fluids cause parts to rise and to sink due to gracvity.

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Thermoclines and Lake Turnover

Exam 3 lecture 2

Nyberg BioS 101 UIC

8

Abrupt change of temperature with depth is known as thermocline.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Lake Michigan

• 6th largest freshwater lake in the world

• 3rd largest of the Great Lakes

• Ave depth = 85 m, Max = 282 m = 925 feet

• Volume = 4,920 km3, retention time 99 years

• Total drainage basin = 118,000 km2

  • IL drainage basin = 300 km2

Speaker Notes:

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Retention time = residence time.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Lake Michigan

Speaker Notes:

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Alliance for the Great Lakes has an adoptabeach@greatlakes.org program in March and April.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Water Crib
Where Chicago Water Comes From

Speaker Notes:

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The south crib is in the picture.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Fish of Lake Michigan

• Lake trout, Whitefish and Perch are the native fish of Lake Michigan

• The fauna has been dramatically altered by invasions and deliberate introductions.

  • Invaders

    • Sea Lamprey, Alewife, Round Gobi

  • Introductions

    • Smelt, Coho Salmon, Chinook Salmon

Speaker Notes:

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Strangely the native lake trout currently has to be stocked, because there is no natural population.

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Wetlands

• Kankakee and Calumet were huge wetlands of Chicagoland. The marshes have largely been drained or filled.

• Wetlands have high levels of biological activity because of the availability of water.

• An ephemeral wetland is one that is both wet and dry in same year.

Exam 3 lecture 2

Nyberg BioS 101 UIC

13

Speaker Notes:

A Natural History of the Chicago region by Joel Greenberg is a good source of information.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

14

Streams and Rivers

• Streams and rivers have a channel.

• Greater drops in elevation per unit length make the water flow faster.

• Rivers naturally meander, especially when elevation loss is slow.

• Many organisms stay in one place and let the current bring food to them.

Speaker Notes:

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Most streams and rivers carry dramatically different amounts of water during a year.

A 100 year flood is a flood so large that it is expected to occur only once in 100 years.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

15

Transportation by Rivers

• People have used rivers to get themselves to new places for a long time.

• People have also used flowing water to get rid of waste.

• Sanitary sewers collect excrement which flows to a processing place where nutrients are removed before water leaves the plant.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Estuary

• Rivers eventually flow into oceans.

• Frequently, sediments from the river accumulate to form shallow areas near the mouth of the river known as estuaries.

• Emergent plants and the mixing of nutrients from the river and the ocean make estuaries very productive.

Speaker Notes:

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The removal of sediments from the Mississippi River has lead to the erosion of marshes in Lousiana.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

17

Dead Zones

• Nutrients from the river are not always used up in the estuary.

• Nitrogen from the Mississippi River has resulted in increased algal growth in the Gulf of Mexico. Old algae sink to the bottom and their decomposition depletes the oxygen near the bottom.

• Fish flee the water without oxygen and from the fisherman’s point of view it is a ‘dead zone’.

Speaker Notes:

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Do you remember BOD, Biological Oxygen Demand, was a way to monitor the impacts of sewage effluent?

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Oceans

• Oceans cover almost 3/4ths of the earth’s surface. Most of the water on earth is saltwater.

• At 10 m under the water surface the pressure is equal to 1 atmosphere.

• Sunlight penetrates ocean to only 40 m and deep areas are dependent on currents for oxygen.

Speaker Notes:

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The water near the surface is quite different from the great depths.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Tides

• The gravitational attraction of the moon creates tides in the ocean.

• There are two high tides and two low tides per 25 hour period.

• The intertidal zone is the area between the high tide and low tide. Wave action keeps plants from growing on sand beaches.

Speaker Notes:

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Because the moon is revolving around the earth, it rises about 1 hour later each day.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

20

Shallow Ocean

• Most continents are surrounded by a ‘shelf’ of rock that means the ocean is relatively shallow (less than 200 m) near the shore.

• Continental shelfs are where almost all the ocean fishing occurs.

• This area is called the neritic zone.

Speaker Notes:

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There is a broad shelf off the east coast but a much smaller shelf on the west coast.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Overfishing

• There have been many examples of overfishing.

  • Sardine fishery of Monterey CA

  • Lake trout in Lake Michigan

  • Herring in the North Sea

  • Cod off MA and Canada

• Some overfished populations recover after fishing stops, but most have not recovered.

Speaker Notes:

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Of the four examples listed only herring in the North Sea could be said to have recovered. The Lake Trout in Lake Michigan are stocked.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Oxygen in Water

• Oxygen is not very soluble in water, 16 mg/l.

• If the water contains organic compounds metabolism can quickly use all the oxygen in the water, creating anaerobic conditions.

• BOD, biological oxygen demand, measures how much oxygen would be used in respiration of organics in water.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Energy Flow in Aquatic Systems

• Streams and small ponds typically get considerable inputs from the surrounding terrestrial environment, e.g., leaf litter.

• Phosphorus is usually the nutrient limiting growth of algae. Input from humans has resulted in ‘blooms’ of algae. Increase in growth of organisms is called eutrophication.

Speaker Notes:

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Exam 3 lecture 2

Nyberg BioS 101 UIC

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Eutrophication

• Clear water implies that the density of fine particles, including small organisms, is not high. Such lakes, including Lake Michigan, are called oligotrophic.

• Lakes with an abundance of by small organisms (and resulting high turbidity) are called eutrophic.

Speaker Notes:

While the prefix ‘eu’ means ‘good’, often such lakes have too much of a ‘good’ thing.

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Exam 3 lecture 2

Nyberg BioS 101 UIC

25

Vocabulary

• Freshwater

• Saltwater

• Eutrophication

• Algal bloom

• Biological Oxygen Demand, BOD

• Dead zone

• Overfishing

• Estuary

• Turnover

• Oligotrophic

Speaker Notes:

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