BIOMES

The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water.[1] Another definition is "any of the large bodies of water into which the great ocean is divided".[2] Separate names are used to identify five different areas of the ocean: Pacific (the largest) Atlantic, Indian, Southern (Antarctic), and Arctic (the smallest).[3][4] Seawater covers approximately 361,000,000 km2 (139,000,000 sq mi) of the planet. The ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth. Acting as a huge heat reservoir, the ocean influences climate and weather patterns, the carbon cycle, and the water cycle. The ocean covers ~70% of the Earth, sometimes called the "blue planet" Oceanographers divide the ocean into different vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column from surface to ocean floor throughout the open ocean. The water column is further categorized in other zones depending on depth and on how much light is present. The photic zone includes water from the surface to a depth of 1% of the surface light (about 200 m in the open ocean), where photosynthesis can occur. This makes the photic zone the most biodiverse. Photosynthesis by plants and microscopic algae (free floating phytoplankton) creates organic matter using light, water, carbon dioxide, and nutrients. Ocean photosynthesis creates 50% of the oxygen in earth's atmosphere[5]. This upper sunlit zone is the origin of the food supply which sustains most of the ocean ecosystem. Light only penetrates to a depth of a few hundred meters; the remaining ocean below is cold and dark. The continental shelf where the ocean approaches dry land is more shallow, with a depth of a few hundred meters or less. Human activity has a greater impact on the continental shelf.

Ocean temperatures depend on the amount of solar radiation reaching the ocean surface. In the tropics, surface temperatures can rise to over 30 °C (86 °F). Near the poles where sea ice forms, the temperature in equilibrium is about −2 °C (28 °F). Deep seawater temperature is between −2 °C (28 °F) and 5 °C (41 °F) in all parts of the ocean.[6] Water continuously circulates in the oceans creating ocean currents. These directed movements of seawater are generated by forces acting upon the water, including temperature differences, atmospheric circulation (wind), the Coriolis effect and differences in salinity.[7] Tidal currents originate from tides, while surface currents are caused by wind and waves. Major ocean currents include the Gulf Stream, Kuroshio current, Agulhas current and Antarctic Circumpolar Current. Collectively, currents move enormous amounts of water and heat around the globe. This circulation significantly impacts global climate and the uptake and redistribution of pollutants such as carbon dioxide by moving these contaminants from the surface into the deep ocean.

(source: wikipedia)

Rivers, creeks, lakes, ponds, and streams are all freshwater habitats. So are wetlands like swamps, which have woody plants and trees; and marshes, which have no trees but lots of grasses and reeds. Freshwater accounts for only three percent of the world’s water. (The rest is saltwater.) But despite that tiny amount, freshwater habitats are homes for more than 100,000 species of plants and animals. Fish living in freshwater habitats have plenty of company. Snails, worms, turtles, frogs, marsh birds, mollusks, alligators, beavers, otters, snakes, and many types of insects live there too. Some unusual animals, like the river dolphin and the diving bell spider, are freshwater creatures. Plants such as algae, cattails, water lilies, and aspen and willow trees help keep the water clean by using their root systems to filter pollution and excess nutrients from the water.

Lakes are formed by different acts of nature. Many appeared after glaciers moved across Earth during the last ice age, between 12,000 and 1.8 million years ago, and left giant bowl-shaped hollows in the land that filled with rainwater and runoff. Others were created when Earth’s crust shifted, leaving grooves and ridges to catch water. And sometimes when a volcano erupts, all the magma flows out. If the land collapses into the empty crater, it leaves holes that can turn into huge lakes. Crater Lake in Oregon was made this way. Rivers are created when melting snow or ice runs down mountains, following the grooves and channels of the land on the way to the sea—rivers always flow to an ocean. Wetlands, areas where the land is covered with water most of the time, often form in the land surrounding rivers that flood, or in areas where groundwater seeps up through the bedrock underneath the soil. Bedrock is made of different types of rocks like granite, sandstone and limestone. Water can seep through the cracks between these rocks, and it can dissolve limestone. Beavers can even create wetlands by building dams on rivers and streams.

(source: nationalgeographic)