9.3 Lakes and freshwater wetlands

Main Idea As the Amount of water changes and the amount of sediments increases, lakes can be transformed into wetlands and eventually into dry land.

Origins of lakes Lakes-Bodies of water surrounded by land, form in different ways in surface depressions and in low areas.

Ways that lakes can form Oxbow lake

Ways that lakes can form Stream flow becomes blocked by sediment from landslides or other sources Other?

Ways that lakes can form Glaciers as glaciers move they form lakes by gauging out land and leaving behind a surplus of water when they melt. This is how a majority of the lakes in Michigan including the great lakes formed. Video

Lakes Undergo Change A lakes water supply is maintained by precipitation, runoff, and underground water sources. Over hundreds of thousands of years lakes will fill in with sediment and become part of the landscape

Eutrophication Nutrients added to lake by run off from surrounding watershed. video

Freshwater Wetland Wetland-are of land covered by water for part of the year. Includes Bogs Marshes Swamps

Bogs Non stream fed Receives water from precipitation Soil rich in sphagnum moss Breakdown of peat moss creates acids Very acidic Supports unusual plant species

Bogs

Marshes Form along mouths of rivers Constants supply and nutrients and water Lush marsh grasses Abundant wildlife

Swamps Low-lying areas near streams Can develop from marshes that have filled in to support growth of trees and shrubs As larger trees grow they shade the marsh plants causing them to die. Old swamps developed 200 million years ago developed in to present day coal reserves. How is coal formed 7:39

Wetlands and Water Quality Improve water quality Filtering system that traps pollutants, sediments, and bacteria Home to an abundance of wildlife

Feedback: Fertilizers such as nitrates and phosphates contribute to eutrophication.

Feedback: Plants take in carbon dioxide and release oxygen through photosynthesis.

Feedback: Wetlands serve multiple purposes at one time, making them valuable natural resources on Earth.

Feedback: Eutrophication is a natural process, but it can be sped up with the addition of nutrients, such as those found in fertilizers.