1. < BackNext >PreviewMain Section 2 Marine Ecosystems Chapter 20 Life in the Ocean Abiotic Factors Marine ecosystems are shaped by abiotic factors including water temperature, water depth, and the amount of sunlight that passes into the water. Plankton Trillions of plankton live in the ocean. Plankton are tiny organisms that float near the surface of the water.

2. < BackNext >PreviewMain Section 2 Marine Ecosystems Chapter 20 Temperature Depth and Temperature The temperature of ocean water decreases as the depth of the water increases.

3. < BackNext >PreviewMain Section 2 Marine Ecosystems Chapter 20 Depth and Sunlight The Intertidal Zone The intertidal zone is the place where the ocean meets the land. The Neritic Zone As you move farther away from shore, into the neritic zone, the water becomes deeper. The Oceanic Zone In the oceanic zone, the sea floor drops sharply The Benthic Zone The benthic zone is the ocean floor. The deepest part does not get any sunlight.

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6. < BackNext >PreviewMain Section 2 Marine Ecosystems Chapter 20 A Closer Look Intertidal Areas Intertidal areas are found near the shore. These areas include mudflats, sandy beaches, and rocky shores. Coral Reefs Coral reefs are found in warm, shallow areas of the neritic zone. Reefs provide homes for many marine animals and plants. Estuaries An area where fresh water from rivers spills into the ocean is called an estuary. Plants and animals living in estuaries must be able to survive in a changing concentration of salt.

7. < BackNext >PreviewMain Section 2 Marine Ecosystems Chapter 20 A Closer Look, continued The Sargasso Sea An ecosystem called the Sargasso Sea is found in the middle of the Atlantic Ocean. The ecosystem contains floating rafts of algae. Polar Ice The Arctic Ocean and the ocean around Antarctica have icy waters, which are rich in nutrients. Many fishes, birds, and mammals live in this ecosystem.

8. < BackNext >PreviewMain Section 3 Freshwater Ecosystems Chapter 20 Stream and River Ecosystems Water in Streams and Rivers The water in brooks, streams, and rivers may flow from melting ice or snow. Or the water may come from a spring. Tributaries Each stream of water that joins a larger stream is called a tributary.

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10. < BackNext >PreviewMain Section 3 Freshwater Ecosystems Chapter 20 Pond and Lake Ecosystems Life near Shore The are of water closest to the edge of a lake or pond is called the littoral zone. The plants in the littoral zone are homes to small animals. Life Away from Shore The area of a lake or pond that extends from the littoral zone across the top of the water called the open-water zone. Beneath the open-water zone is the deep-water zone, where no sunlight reaches.

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12. < BackNext >PreviewMain Section 3 Freshwater Ecosystems Chapter 20 Wetland Ecosystems Marshes A treeless wetland ecosystem where plants, such as grasses, grow is called a marsh. Muskrats, turtles, frogs, and birds live in marshes. Swamps A wetland ecosystem in which trees and vines grow is called a swamp. Water lilies and other plants grow in standing water. Many fishes, snakes, and birds also live in swamps.

13. < BackNext >PreviewMain Section 3 Freshwater Ecosystems Chapter 20 From a Lake to a Forest Build Up of Sediments Water entering a standing body of water usually carries nutrients and sediments. These materials build up on the bottom of the lake or pond. Formation of a Wetland Over time, the pond or lake is filled with sediments. Plants grow in the new soil and the pond or lake starts becoming a wetland. The wetland then may develop into a forest.