1. Compare and Contrast What are some ways in which life in an aphotic zone might differ from life in a photic zone
Apply Concepts What is a wetland and why are they important
Predict How might a dam upriver affect an estuary at the river’s mouth
Review List the three major marine ecological zones and give two abiotic factors for each.

2. Ch 4 Ecosystems and Communities
4.5 Aquatic Ecosystems

3. Nearly three-fourths of Earth’s surface is covered with water.

4. Aquatic organisms are affected primarily by the water’s depth, temperature, flow, and amount of dissolved nutrients.

5. Water Depth
Sunlight penetrates only a relatively short distance through water
Photic zone
Sunlit region near the surface in which photosynthesis can occur
May be as deep as 200 meters in tropical seas
May be much, much less.

6. Photosynthetic algae (phytoplankton) live in the photic zone
Zooplankton (tiny free-floating animals)eat phytoplankton.

7. Aphotic zone Benthic zone Benthos Photosynthesis cannot occur
Rocks and sediments and on bottom of lakes and streams
Benthos
Aquatic organisms that live in the benthic zone.

8. Temperature and Currents
Warmer near the equator and colder near the poles
Deepest parts of lakes and oceans are often colder than surface waters
Currents can carry different temperature waters.

9. Nutrient Availability
Not consistent in aquatic habitats.

10. Freshwater ecosystems can be divided into three main categories: rivers and streams, lakes and ponds, and freshwater wetlands.

11. Rivers and Streams
Often originate from underground water sources in mountains or hills
Have plenty of dissolved oxygen but little plant life near source
Sediments build up and plants establish themselves downstream
Depend on terrestrial plants and animals that live along their banks for food.

12. Lakes and Ponds
Based on a combination of plankton and attached algae and plants
Water flows in and out of lakes and ponds and circulates between the surface and the benthos, distributing heat, oxygen, and nutrients.

13. Freshwater Wetlands Wetland May have flowing water
Water either covers the soil or is present at or near the surface for at least part of the year
May have flowing water
Nutrient-rich, highly productive, and serve as breeding grounds for many organisms
Purify and filter water
Freshwater bogs, freshwater marshes, and freshwater swamps.

14. Estuary Saltwater wetland Where river meets the sea Affected by tides
Spawning and nursery grounds for many ecologically and commercially important fish and shellfish species.

15. Marine Ecosystems
Ocean divided into zones based on depth and distance from shore:
Intertidal zone, the coastal ocean, and the open ocean.

17. Intertidal Zone
Submerged in seawater at high tide and exposed to air and sunlight at low tide
Barnacles and seaweed attached to rocks.

18. Coastal Ocean
Extends from the low-tide mark to the outer edge of the continental shelf
Water is brightly lit, and is often supplied with nutrients- very productive.

19. Open Ocean
Begins at the edge of the continental shelf and extends outward
More than 90 percent of the world’s ocean
Depth ranges from 500 m along to more than 10,000 m
Divided into photic and aphotic zones.

20. Photic Zone
Typically has low nutrient levels and supports only small phytoplankton
Most photosynthesis occurs in the top 100 meters of the open ocean.

21. Aphotic Zone
Permanently dark
Deepest parts of the ocean.