Monday, March 12, 2012

Our Sunlit Ocean - a Biological Pump

Did you know that there is a huge connection between our oceans and our atmosphere?  The top layer of oceans is soaked in sunlight during the daytime. This bright ocean layer is called the euphotic zone (euphotic means "well lit" in Greek) and is about 200 m (the depth of the ocean averages about 4,000 m) The temperature in this zone ranges from -2 to 40°C.
In this zone, there is enough light for photosynthesis to take place. In fact, most of the life in the ocean is found in this zone and there is heaps of food, although it is the smallest ocean zone in terms of volume of water.
 Most of the oxygen is produced by phytoplankton. Phytoplankton are the first link in the food chain in the ocean. Because of this food source, many animals also live in this zone. Photosynthesis is a process in which sunlight and carbon dioxide gas are converted into food (chemical energy contained in carbohydrates) and oxygen. We know about this with plants on land but it is just as an important process under water. They call it the “biological pump” here. The taking of light and carbon dioxide and converting it to oxygen.
Photosynthesis in the oceans creates approximately 90% of the Earth's oxygen!

Desert dust and carbon dioxide settle into the ocean and act as "fertilizer" to stimulate the growth of phytoplankton, enhancing the ocean's ability to absorb carbon dioxide from the atmosphere (the "biological pump). Over time, more than 90 % of the world's carbon has settled into the deep ocean.

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