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Aquatic Biomes

About three quarters of our planet Earth is covered with water. Water is the common link among all the other biomes of the planet and it makes te largest biome of the biosphere. Water covers about 75% of the Earth's surface. The aquatic biomes from oceans to the rivulets are a wide variety of habitat. The water biome can host a wide variety of life-forms from the common algae to the mysterious deep sea creatures. 

In fact life began in the ocean billions of years ago when amino acids stared coming together; without water earth would have been a barren land and no organisms can sustain without water. There is a wide variety of temperatures in this biome, yet the areas with water tend to be more humid and cooler on the air temperature. 

Aquatic biome, like other biomes can be divided into two categories: Freshwater biome and Marine biome. 

Aquatic Biome



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Aquatic biomes are defined as the areas of ocean and other water bodies which have similar climatic condition on the Earth. Aquatic biomes are of two major regions marine and freshwater. Freshwater biome consists of the lakes, ponds, rivers, streams, and wetlands. The marine regions include oceans, coral reefs and estuaries. 


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Aquatic biome is a three dimensional habitat that can be divided into zones based on characteristics like temperature, depth, tidal flow and its closeness to landmass.
  • Based on the saline conditions of water marine water is divided into two major groups which include freshwater habitat and marine habitat. 
  • Another factor in which this biome can be distinguished is the degree of light penetration into the water. The zone which has enough light penetration to support photosynthesis is known as photic zone. The zone in which there is light penetration and does not support photosynthesis is known as aphotic or profundal zone. 
There are two types of aquatic biomes, the marine biome and the freshwater biome:
  • The marine biome consists of the oceans, seas, coral reefs and estuaries. These are habitats with high saline conditions. In these habitats we find mangrooves, salt marshes, and mudflats. Marine habitats consist of five zones - intertidal, neritic, oceanic pelagic, abyssal and benthic zones. 
  • Freshwater biomes are aquatic habitats with low saline conditions. The freshwater habitat is classified into  lotic (moving water bodies) and lentic (standing water bodies). Lotic forms includes streams and rivers. Lentic forms include bogs, lakes, ponds, and inland wetlands. Freshwater habitats are also influenced by land of the surrounding areas, the pattern and speed of water flow and the climatic condition. 


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Some of the key characteristics of aquatic biome are: 
  • Aquatic biome is the largest of all the biomes. 
  • It is dominated by water. 
  • Life first evolved in the aquatic habitat. 
  • It is a three-dimensional environment and it plays a major role in the world's climate. 

Aquatic Biome Climate

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Climatic conditions of the fresh water biome varies between fresh water and marine water biome. These biomes are distributed unevenly across the globe and so the climate of these biomes differ depending on the region. 

Freshwater Biome 
  • In the freshwater biome, the average temperature ranges from 65°F to 75°F in the summer and in the winter it is about 35°F to 45°F. 
  • The climate of this region is determined by a number of prominent factors like location, season and depth of water. 
  • As the water gets deeper the average temperature declines. This pattern of climatic variation is common in lakes with less water movement than river or stream. 
  • Precipitation in this biome also depends on the region of biome location. 
Marine Biome
  • The ocean has a significant influence on inland temperature whether the climate would be sunny or cloudy. 
  • Temperatures in the ocean differs according to the regions in which they are present. 
  • The temperatures may be freezing at the poles and in deep waters. It may be warm in the clear tropical waters. 
  • The average temperature of all oceans is about 4°C. Heat and light from the sun warms the surface water of the oceans, deep inside the oceans everywhere are cold and dark. 

Aquatic Biome Plants

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Marine Habitat: There are over one million plant species discovered in the oceans. Marine algae are the most important plant, as they supply much of the oxygen needed. Kelp is an important species of marine algae. This species provides food, shelter to a lot of sea creatures. Kelp is also used by humans in products like toothpaste and icecream. Kelps also act as buffer protecting the sandy beaches along the coast. Other important marine plant is phytoplankton which is the food for many ocean creatures. 

Freshwater Habitat: Plants and algae are important flora of the freshwater biome. They provide oxygen and food to animals of the freshwater. Plants which have strong roots and which have stems that can bend easily to movement of water are seen in rivers and streams. Still water has plants like lilies, algae, duckweed that float on surface also are seen cattails and reeds along the shore of the freshwater habitat. 

Aquatic Biome Animals

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The main varieties animals found in the marine water biome are whales, dolphins, seals and sharks. The other kind of fish that live in the sea are starfish, eels, walrus, crabs jelly fish and other salt water fish and many crustaceans. Bacteria, fungi, sea anemone and many other animals inhabit the marine waters. There are birds like seagulls which are dependent on marine water fishes for their living. 

The freshwater is home for many varities of fish, insects, amphibians and crustaceans. Many varieties of shell fish, shrimp also inhabit the freshwater biome. Many birds also are dependent on freshwater fishes and also bears also feed on freshwater fishes. 

Freshwater Biome

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Freshwater habitat has low salt concentration, there are differen types of freshwater regions standing water bodies like ponds and lakes, moving water bodies like streams and river and wetlands. 

Standing water like ponds and lakes are regions which range from just a few square kilometers to thousands of square kilometers. Ponds can be seasonal and can last only a couple of months while lakes can exist for hundreds of years or more. There is limited diversity in ponds and lakes. These regions are divided into three different zones like the littoral zone, limetic zone and profundal zone. Temperature varies seasonally in ponds and lakes. 

Freshwater Biome

Flowing water bodies like streams and rivers are water bodies which flow from one direction to other. They can be found everywhere, they can get headwaters from springs, snowmelt. 

Wetlands are standing water areas and they support aquatic plants. Marshes, swamps and bog are considered wetlands. Wetlands have highest species diversity of all ecosystems. 

Marine Biome

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The marine biome is the biggest biome of the Earth. The marine biome covers about 70% of the earth. This biome includes oceans like Pacific, Atlantic, Indian, Artic and Southern, it also includes Gulfs and Bays. Marine biome includes intertidal zones, oceans, coral reefs, benthic zones. The marine algae supply most of the world's oxygen supply and are carbon dioxide sinks. The evaporation of sea water in turn provides rain for the land.

Marine Biome
The marine habitat is divided into four separate zones: 
  • Intertidal zone - The zone where ocean meets the land. 
  • Open ocean or the Pelagic zone - The open ocean is usually cold, there is lot of temperature variation since there is thermal stratification as there is constant mixing of warm and cold ocean currents. 
  • Benthic zone - Is the area below the ocean. The bottom zone consists of sand, silt or dead organisms. 
  • Coral reefs - This zone is widely distributed in warm shallow water. The organisms of this region is mostly corals. 
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