WHAT ARE FRESHWATER BIOMES From rushing rivers to calm lakes and soggy marshes freshwater biomes are some of the most varied in the world Freshwater biomes have one main thing in common they usually contain water with less than one percent salt compared to seawater which is 3 5 percent salt The freshwater four Rivers plus smaller streams are places where freshwater flows across land toward an ocean or lake Lakes along with ponds are areas of still water surrounded by land Wetlands are areas of land such as marshes bogs and wet meadows where water covers the soil for all or part of the year Estuaries are the places where rivers flow into the sea and the freshwater they contain meets and mixes with salty seawater Many rivers start as streams near the top of a mountain and their water flows quickly downhill Fact Focus Biome or Habitat Biomes are regions of the world such as deserts forests rivers oceans tundra and grassland that have a similar climate plants and animals A habitat is the specific place in a biome where a plant or animal lives 4
Freshwater life A whole range of living things has adapted to life in freshwater biomes Trees reeds irises and other plants grow in the damp soil at the water’s edge Some plants such as water lilies live in the water Freshwater animals such as tiny water fleas snails and fish live underwater Other animals including enormous crocodiles and anaconda snakes visit the water to feed Vital resource Freshwater plants and animals have an advantage over those living on dry land because they usually have a constant supply of water Living things are made up mostly of water and they need to constantly replenish this water to survive Skimmers fly low over freshwater lakes plowing their large beaks through the water as they go Their beaks snap shut to trap any fish they scoop up Amazing Adaptation Adaptations are special features or body parts that living things use to help them survive in a biome Diving beetles store air bubbles under their wing cases while they are at a lake’s surface They use the air bubbles as an air supply when they hunt underwater 5
FRESHWATER AROUND THE WORLD Only about three percent of Earth’s total water is freshwater and much of this is frozen at the North and South Poles The rest is found in freshwater biomes around the world Slow rivers change course over time eroding curved paths called meanders across the land Rivers and lakes Thousands of rivers around the world start on mountains or hills as tiny streams As streams flowing downhill join together they form rivers Moving water is powerful and wears away or erodes rock and soil as it rushes downhill When rivers reach flatter land they slow down Lakes form in dips in Earth’s surface The dips include areas scraped out by glaciers in the past or holes left after volcanoes have erupted The water in lakes comes from rivers rainfall melting snow or ice and even water from underground Yukon Mackenzie Missouri Rio Grande Mississippi Volga Ob Yenisey Danube Niger Nile Irtysh Indus Ganges Lena Amur Yellow River Yangtze Mekong Murray Darling The Amazon the Congo and the Yangtze are a few of the world’s largest rivers by volume Each is located in an area of moderate to heavy rainfall Amazon Paraná Congo Monthly heavy rain Seasonal heavy rain 6
Wetlands and estuaries Wetlands are damp areas of land that form where river lake or spring water soaks flat areas of soil Wetlands usually get wetter after rainy periods but some can dry up in drier spells of weather In estuaries water levels rise when tides carry seawater inland twice a day This makes the freshwater in the rivers salty At low tide the water level drops and the water becomes less salty again Plants and animals living in these areas are adapted to deal with the changes in the water levels and saltiness A range of animals including proboscis monkeys probe estuary mud for prey such as crabs in Borneo in Southeast Asia Fact Focus The Water Cycle Freshwater biomes depend on the water cycle This is the continual process of water moving from the land into the atmosphere and back again Water evaporates from the surface of freshwater biomes Later it condenses into droplets of water that form clouds When it rains water falls back to Earth and refills sources of freshwater 7
