Chapter 13. Chapter 13: Marine Ecosystems

What environmental conditions determine the location and makeup...?

Why You Should Care

Oceans cover 75% of the globe, but they are not a uniform set of ecosystems. The most important variables for ecosystems underwater are access to light, nutrients, and depth.

The most diverse and productive communities are those where photosynthesis is the highest— the shallow areas near to shore so they can capture nutrients running off the land (estuaries are shallow areas where freshwater rivers drain into the saltwater ocean). In tropical and subtropical waters, these saltwater ecosystems are the highly productive coral reefs. Colder waters closer to the poles create less productive ecosystems.

Farther out from the shallow coastal waters, ocean depth increases quickly and distance from estuaries causes nutrient levels to drop away quickly. In general, the ocean areas that are shallow enough to support photosynthesis (less than 600 feet down) are the most productive. As you go deeper (more than 600 feet down), productivity drops off sharply and ecosystems that are more dependent on decomposition become more important.

1.

Which of these ocean zones are directly dependent on phytoplankton (producers)?

A.

Hadal zones

B.

Coral reef zones

C.

Open ocean zones

D.

Deepwater zones (meso-, bathy-, and abyssal-pelagic zones)

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Correct.

Incorrect.

2.

Which of these zones are continuous with estuaries (water flows from one to the other)?

A.

Intertidal zones

B.

Epipelagic zones

C.

Hadal zones

D.

Coral reefs

999

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Correct.

Incorrect.

3.

Which of these ocean zones does not have sunlight?

A.

Estuaries

B.

Hadal zone

C.

Epipelagic zone

D.

Coral reefs

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Correct.

Incorrect.

4.

Why are diversity and primary productivity so high around the continental shelf?

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The continental shelf is close to the shore and receives nutrients flowing off the land and from the rivers. These nutrients are usually low in the seawater, so when the levels rise, ocean producers respond with higher productivity. This leads to larger food webs and a higher overall species diversity.

5.

Why are coral reefs often found near estuaries?

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Coral reefs have the highest productivity and diversity in the ocean. These both require higher levels of available nutrients that are only possible near estuaries.

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