Estuaries and Change
Chapter 37: Ecosystem Dynamics

Estuaries are areas where fresh water and salt water mix. Estuaries can support a large number of organisms because of their nutrient-rich environments. The amount of salt water in the estuary impacts the diversity of the organisms. In this activity, you will examine how the diversity of organisms in an estuary changes if you…

Try This

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Look at the organisms shown in the table.

Organism	Food Requirement	Water Requirement
Plankton 1	organic material	fresh
Plankton 2	crab larvae	salt
Clam	organic material	salt
Crab 1	plankton 2	salt
Crab 2	any fish	fresh
Fish 1	plankton 1	fresh
Fish 2	fish 1	salt
Bird 1	fish 1	salt or fresh
Bird 2	crab 2	salt or fresh
Bird 3	any plankton	salt or fresh

Analyze Your Results

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1. After a severe drought, the river that feeds into the estuary almost completely dries up. Ocean water invades the river channel and the estuary is primarily filled with salt water. Which species will increase in number? Which will decrease?
2. After a cold winter, a large amount of sea water freezes. The sea level drops and the estuary is now primarily filled with fresh water. Which species will increase in number? Which will decrease?

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