Water Biomes

Water Biomes

The earth is filled with a variety of climates that give life to different plant species. A large area that shares the same weather patterns and plant species is known as a biome. Many experts agree that seven biomes make up our world. Water makes up three-fourths of Earth’s surface and creates two of its biomes: the freshwater biome and the marine or saltwater biome. The freshwater biome includes ponds, rivers, streams, and other bodies of water with little salt in them. The marine biome consists of the oceans, which contain plenty of saltwater.

Ponds and Lakes

The freshwater biome consists of many unmoving bodies of water known as ponds and lakes. A pond is a shallow hole where water builds up over time from falling rain. Plants grow around the pond and often spread across the bottom of the pond since the water is still shallow enough for sunlight to reach its depths. Temperature is consistent throughout and the water is still, with no waves. Due to its shallow depth, a pond may freeze solid in the winter or completely evaporate in the summer.

When a body of water grows larger and deeper than a pond, it becomes a lake. Lakes can stretch to thousands of square kilometers in size. Plants survive only near the shoreline because further out the water is too deep for adequate sunlight. Some lakes have waves. The temperature of a lake varies widely from top to bottom.

Lake Temperatures in Summer:

  • Top Layer: 19-25°C

  • Middle Layer: 8-19°C

  • Bottom Layer: 4-8°C

Since a lake is so deep, it cannot freeze solid. The top layer can freeze, however, and cut down on oxygen levels. This causes some plants and animals to die off, known as winterkill. In the summertime the opposite occurs. Algae, a plant-like organism found in lakes, can overproduce and die off in large numbers. The decaying algae lowers oxygen levels and kills off some of the plants and animals, known as summerkill. Summerkill and Winterkill can be a problem for those raising fish.

Rivers and Streams

Moving freshwater comes in the form of rivers and streams. The bottom of a river is the riverbed and the sides form its banks. Rivers are larger than streams and eventually flow out into the ocean. Combined, rivers and streams make up 3% of earth’s freshwater and help drain excess water away from the land.

Qualities of Rivers:

  • Large in size

  • Flow into the ocean

  • More abundant in areas of heavy rain

Qualities of Streams:

  • Smaller than rivers

  • Join other stream to form rivers

  • Known as tributaries when they form large rivers

When rivers, streams, and rainfall all flow to a single point where they then empty out into a large body of water, such as a lake or ocean, this is known as a watershed. Watersheds can carry pollution from inland and deposit it into these larger bodies of water. When a river meets the ocean, this point is known as the mouth of the river. It carries soil with it and the soil is deposited at the mouth of the river, where it slowly builds up into land over long periods of time. This new land is called a delta.

The last of the freshwater is found trapped inside glaciers. These frozen rivers are located in places such as Antarctica. It is a common misconception that glaciers don’t move, but the opposite is actually true. Though their progress is slow, glaciers found on high ground slowly move down toward the lower ground.

The Ocean

The ocean covers most of our planet and accounts for 97% of the water found on earth. It provides the fish we catch for food and many of the plants we use in cosmetics and even toothpaste. The ocean also works to regulate the temperature of our air and provides the moisture needed to create rainfall. While the ocean may look smooth on the surface, the ocean floor is actually covered in mountains, valleys, and even volcanoes, just like on dry land. 

Our Oceans:

  • Pacific Ocean – The Pacific Ocean separates North and South America from Asia and Australia. It is further divided into the North Pacific Ocean and the South Pacific Ocean.

  • Atlantic Ocean – The Atlantic Ocean separates the coasts of North and South America from the coasts of Europe and Africa.

  • Indian Ocean – The Indian Ocean separates Africa and southern Asia from Australia and stretches down toward the South Pole.

  • Arctic Ocean – The Arctic Ocean is found in the Arctic, the area where the North Pole is located.

  • Southern Ocean – The Southern Ocean encompasses Antarctica at the South Pole. Some argue that the Southern Ocean should not be considered a separate ocean at all, but generally it is included on the list.

The ocean is about 4,000 meters deep on average, but it can go quite deeper in some spots. The deepest known point in the ocean is the Mariana Trench. Located north of New Guinea, this trench stretches 2,500 kilometers long and varies in width from 70 kilometers to 338. The deepest point of this trench, called Vitjazdepth, is an astounding 11,035 meters deep. It’s not only the deepest known point in the ocean, but also the deepest known point on the entire planet.

The ocean contains varying levels of sodium chloride, the salt we use to season our foods. Salt flows into the ocean from the land. Rain runs through rocks and sand, collecting salt and other minerals on its journey to the ocean. When that water reaches the ocean, it deposits the salt and minerals. When water evaporates out of the ocean, the heavy salt is left behind.


Areas formed from a mixture of water and land, known as wetlands, occur near rivers and in places with heavy rainfall. Swamps, marshes, and bogs all fall under the title of wetlands. Wetlands are both water and land. While they consist of water, they also have thick vegetation growing in them. Often trees grow out of swamps and animal life is abundant.

Wetlands occur along rivers, streams, and other large bodies of water. When it rains, a river can overflow its banks and fill low-lying areas of land to form wetlands. In dry seasons the wetland may dry up completely. To be considered a wetland, the water must be present for part of the year.

In the past, people drained wetlands and filled them in to prevent them from filling with water. More recently people have begun to recognize the wetlands for the natural resources they provide. Many plants and animals call the wetlands home. Birds often migrate from wetland to wetland on their migration path, and some even go there to nest. The wetlands also prevent flooding by collecting overflow from rivers during heavy rain and prevent rivers and lakes from drying up by dumping water back into the river or lake during dry seasons. Despite these benefits, some people still drain wetlands.

Water Biomes Information

  • The World’s BiomesLearn what a biome is and what biomes make up our planet.

  • The Aquatic BiomeA detailed look at the aquatic biomes.

  • Marine BiomeDiscover the animals and plants that live in the marine biome, along with the health issues they’re facing.

  • Aquatic BiomeLearn about the aquatic biome and see images of the plants and animals that call it their home.

  • Life’s Little EssentialPBS explains why water is vital to the formation and survival of all living things.

  • The Water CycleAn animated diagram of the water cycle. Find out where water comes from.

  • Why is the Ocean Salty?Find out why the ocean is salty and just how salty it is.

  • Where is Earth’s Water Located? Find out how the water on our planet is distributed and how much is usable versus unusable.

  • Marine LifeLearn about marine life and see what plants and animals live in the ocean.

  • Wetland LifeDiscover the plants and animals that thrive in the wetlands.

  • Lake InformationFind out how lakes form and what changes their water levels.

  • Physical Features of the OceanThe ocean holds many surprised. Find out what the ocean floor is actually like.

  • FreshwaterThe Encyclopedia of Earth presents detailed facts and graphs on freshwater and everything there is to know about it.

  • All About GlaciersThe National Snow and Ice Data Center offers a breath-taking look at glaciers and facts about their attributes.

  • Icefields and GlaciersLearn where glaciers and icefields come from, along with what kinds of plant and animal life exist near glaciers.