មហាសមុទ្រ

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**មហាសមុទ្រ** គឺជាផ្ទៃទឹកធំល្ហល្ហេវមើលដាច់កន្លុយភ្នែក ជាសមុទ្រធំៗដែលមានទីតាំងចន្លោះ-រវោងដីទ្វីប។ Oceans are very big and they join smaller seas together. Together, the oceans are like one "ocean", because all the "oceans" are joined. Oceans (or marine biomes) cover 70% of our planet. 
The largest ocean is the Pacific Ocean. It covers 1/3 (one third) of the Earth's surface. The smallest ocean is the Arctic Ocean.
Different water movements separate the Southern Ocean from the Atlantic, Pacific and Indian oceans. It is also known as the Antarctic Ocean, because it covers the area around Antarctica. Older maps may not use the names Arctic Ocean and Southern Ocean. The deepest ocean is the Pacific ocean. The deepest point is the Mariana Trench, being about 11,000 metres (36,200 feet) deep. The deep ocean is characterized by cold temperatures, high pressure, and complete darkness. Some very unusual organisms live in this part of the ocean. They do not require energy from the sun to survive, because they use chemicals from deep inside the earth.

## ពណ៌ 
វាជាការខុសក្នុងការនិយាយថា មហាសមុទ្រមានពណ៌ខៀវ ពីព្រោះទឹកឆ្លុះបញ្ចាំងពីផ្ទៃមេឃពណ៌ខៀវ។ ទឹក​មាន​ពណ៌​ខៀវ​បន្តិច​ដែល​អាច​មើល​ឃើញ​តែ​ក្នុង​បរិមាណ​ទឹក​ច្រើន​ប៉ុណ្ណោះ។ ទោះជាយ៉ាងណាក៏ដោយ មូលហេតុចម្បងនៃពណ៌ខៀវ ឬពណ៌ខៀវ/បៃតង គឺថាទឹកស្រូបយកផ្នែកពណ៌ក្រហមនៃពន្លឺដែលចូលមក ហើយឆ្លុះបញ្ចាំងពីផ្នែកពណ៌បៃតង និងពណ៌ខៀវនៃពន្លឺ។
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## រុក្ខជាតិ និងសត្វ 
សារពាង្គកាយដែលរស់នៅក្នុងមហាសមុទ្រអាចរស់នៅក្នុងទឹកប្រៃ។ ពួកគេត្រូវបានប៉ះពាល់ដោយពន្លឺព្រះអាទិត្យ សីតុណ្ហភាព សម្ពាធទឹក និងចលនាទឹក។ សារពាង្គកាយមហាសមុទ្រផ្សេងៗគ្នារស់នៅជិតផ្ទៃទឹក ក្នុងទឹករាក់ និងក្នុងទឹកជ្រៅ។ សារពាង្គកាយរុក្ខជាតិតូចៗដែលរស់នៅជិតផ្ទៃ និងប្រើប្រាស់ពន្លឺព្រះអាទិត្យដើម្បីបង្កើតអាហារត្រូវបានគេហៅថា ផាំងតុន។ សត្វស្ទើរតែទាំងអស់នៅក្នុងមហាសមុទ្រអាស្រ័យដោយផ្ទាល់ឬដោយប្រយោលលើរុក្ខជាតិទាំងនេះ។ នៅក្នុងទឹករាក់ អ្នកអាចរកឃើញបង្កង និងក្តាម។ នៅក្នុងទឹកជ្រៅ សត្វសមុទ្រដែលមានរូបរាង និងទំហំខុសៗគ្នាជាច្រើនហែលឆ្លងកាត់មហាសមុទ្រ។ ទាំងនេះរួមមានត្រីជាច្រើនប្រភេទដូចជា ត្រីធូណា ត្រីដាវ និងថនិកសត្វសមុទ្រដូចជា ផ្សោត និងត្រីបាឡែន។ ផ្ទៃមេឃនៅពីលើមហាសមុទ្របើកចំហគឺជាជម្រករបស់សត្វស្លាបសមុទ្រធំៗដូចជា អាល់បាត្រូស។ Fish are a fine source of protein, so many people eat them. Fishing  are very important because they let people have jobs and give food to millions of people. Today, usually through ocean fishing, the ocean supplies about 2% of the calories needed by the people living on Earth. Tuna, anchovies, and herring are harvested close to the surface of the ocean. Pollock, flounder and cod are caught near the ocean floor. More than a million tons of herring are caught every year in the North Pacific and North Atlantic, and almost eight fish out of ten fish are eaten as food for humans. The other fish are used as , glue, and pet and other animal food.

## សីតុណ្ហភាពមហាសមុទ្រ 
There are many different ocean temperatures in the open ocean, both vertically (from top to bottom) and . Icebergs are made over very cold waters at either pole, while waters at the equator are pretty warm. Water cools and warms more slowly than land does, so land influenced by the ocean has later and milder seasons than land that is farther away from the ocean.

The surface part of the ocean, also called the *mixed layer*, is not much colder even when we go deeper down. Below this surface zone is a layer of sudden temperature difference, called a *thermocline*. This is a middle layer hat is from the surface zone down to about 2,600 feet (800 m). Thermoclines may happen only at seasons or , and may change depending on where and how deep it is. As evaporation happens, it begins cooling, and if the water evaporates very quickly, the water becomes saltier. The salty, cold water is , so it sinks. This is why warm and cold waters do not easily mix. Most animals and plants live in the warm upper layer. Below the thermocline, temperature in the deep zone is so cold it is just above freezing - between 32 &ndash 37.4 F (0 &ndash 3 C).

## ឯកសារយោង