Name: _________________________________________________  Period: _______________

Tolerance Ranges of Organisms in an Estuary

Estuaries, also called bays, salt marshes, lagoons or fjords, are shallow, partially enclosed coastal bodies of water where fresh and salt water meet and mix. Most estuaries occur where rivers empty into the ocean. Because river water is so full of organic (dead plant and animal) matter, estuaries are rich in nutrients and tiny water plants and animals, called plankton, are plentiful. Not surprisingly, estuaries are highly productive communities. Although they only represent 2 to 3 percent of the total ocean area, estuaries alone are responsible for 75 to 90 percent of all fish and shellfish caught each year. Abundant fish life, in turn, attracts hundreds of species of birds. Estuaries contain a diverse array of plant and animal life.

The makeup of all estuaries is not the same because some areas of an estuary may contain more fresh water than other, while other areas may contain more salt water. The pattern of salinity (amount of salt found in the water) is crucial to the diversity of organisms that live in an estuary.

Problem: How do changes in salinity of an estuary affect the biodiversity of the area?

Term review:

Estuary =

Organic matter =

Plankton =

Salinity =

Biodiversity =

Procedure:

1.      Arrange all the GREEN organism cards face up on your desk or lab table.

2.      Sort them by water preference (fresh, salt or fresh or salt).

3.      Read the following scenarios and decide how each situation would alter the water conditions in the estuary.

4.      Then determine the effects the salinity changes would have on each organism.

5.      Remove the cards that represent species that would decline or disappear from the estuary.

6.      Next examine the food sources for each organism.

7.      Remove the cards that represent species that would decline or disappear from the estuary because they no longer have a food source.

8.      Repeat steps 6 and 7 until you have a stable community.

 

Scenario 1: Start with all GREEN cards only.

After a severe drought, the river that feeds into the estuary almost dries up and ocean water invades the river channel. The estuary is now primarily filled with salt water.

1.      Which organisms disappear initially due to salinity changes?

 

2.      Which organisms later disappear due to lack of food?

 

Scenario 2: Start with all GREEN cards only.

After an unusually cold winter, a large amount of sea water freezes into icebergs. Because of this the sea level drops and the estuary is now primarily fed by the river.

 

1.      Which organisms disappear initially due to salinity changes?

 

2.      Which organisms later disappear due to lack of food?

 

Scenario 3: Start with all the green cards plus the following YELLOW cards:

FISH C lives in fresh water and eats any plankton.

Crab C lives in salt water and eats any plankton.

After a severe drought, the river that feeds into the estuary almost dries up and ocean water invades the river channel. The estuary is now primarily filled with salt water.

1.      Which organisms disappear initially due to salinity changes?

 

2.      Which organisms later disappear due to lack of food?

 

Scenario 4: Start with all the cards including the two yellow cards.

After an unusually cold winter, a large amount of sea water freezes into icebergs. Because of this the sea level drops and the estuary is now primarily fed by the river.

 

1.      Which organisms disappear initially due to salinity changes?

 

 

2.      Which organisms later disappear due to lack of food?

Mark a plus sign (+) if the organism lives, and mark a minus sign () if the organism dies in the table below.

 

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Plankton A

 

 

 

 

 

Plankton B

 

 

 

 

 

Clam A

 

 

 

 

 

Crab A

 

 

 

 

 

Crab B

 

 

 

 

 

Crab C

 

XXXXXXX

XXXXXXX

 

 

Fish A

 

 

 

 

 

Fish B

 

 

 

 

 

Fish C

 

XXXXXXX

XXXXXXX

 

 

Bird A

 

 

 

 

 

Bird B

 

 

 

 

 

Bird C

 

 

 

 

 

Total # of surviving species

 

 

 

 

 

Analysis: Did an increase in biodiversity (more different organisms) for scenario 3 and 4 make the estuary more or less stable? Explain you answer.

 

Use these cards to complete the lab Tolerance Ranges in an Estuary

Fish A

Plankton A

Salt water

Green card

Fish B

Fish A

Salt water

Green card

Plankton B

Crab larvae

Salt water

Green card

Clam A

Organic particles

Salt water

Green card

Bird A

Fish A

Salt or fresh water

Yellow card

Bird B

Crab B

Salt or fresh water

Green card

Bird C

Any plankton

Salt or fresh water

Green card

Plankton A

Organic particles

Fresh water

Green card

Crab A

Plankton B

Fresh water

Yellow card

Crab B

Any fish

Fresh water

Green card

Fish C

Any plankton

Fresh water

Yellow Card

Crab C

Any plankton

Salt water

Yellow card