Seas

We explain what a sea is and what its characteristics are. Also, what types of seas exist, examples and their differences from the oceans.

What are the seas?

The sea is a portion of salt water smaller than the ocean and larger than a lake. Seas are usually differentiated from oceans because the seas are the areas close to the coasts and have a smaller area and depth than the oceans.

Seas and oceans occupy 70% of the earth's surface and, in many cases, it is difficult to delimit the border that separates one from another. While there are only five oceans in the world, there are more than 50 seas, including: the Caspian Sea, the Mediterranean Sea, the Caribbean Sea and the Black Sea.

The seas are also confused with large lakes But, unlike these, the seas are masses of moving water.

See also: Rivers

Characteristics of the seas

Some of the main characteristics of the seas are:

• Composition. The sea is made up of 96.5% pure water, while the remaining percentage (3.5%) corresponds to salts such as sodium, sulfates, magnesium, chlorine, potassium and calcium. The exact amount of salt depends on each particular sea, but is usually 35 mg per liter of water.
• Temperature. Sea temperatures depend on geographical location. Some seas maintain a constant temperature throughout the seasons, while in others the temperature fluctuates according to the ambient temperature. This is how in the seas of the Caribbean or Asia the water remains warm throughout the year and in seas like that of Japan the temperature varies. Sea temperatures are always higher than ocean temperatures, this is because the sun's rays reach the bottom of the sea and prevent temperatures from dropping too much.
• Tides. The seas present two types of movements: waves and ocean currents. Waves are shallow and remarkably visible while currents are underwater and only detected by specific instruments.
• Fauna. Within the seas you can find an immense variety of marine animals. The type of fauna that lives in each sea depends on the geographical location, depth, water temperature, among other characteristics. Some of the main marine animals are: sea turtles, fish, whales, dolphins, sharks, crabs, starfish, octopuses, manta rays, among many others.

Types of seas

There are three main types of seas:

• Littoral or coastal seas. They are areas in which, despite the fact that there is no clear dividing line between the sea and the ocean, the coastal sea is recognized because it has greater tidal range, slightly higher temperatures compared to the oceans, and is shallower. For example: the Norwegian Sea.
• continental seas. They are seas that are located entirely within one or several continents and are connected to the ocean by a narrow groove. Between the sea and the ocean there are differences in temperature and salinity. For example: the Mediterranean Sea.
• closed seas. They are seas that are completely isolated and are often confused with very large lakes. Generally these waters tend to contain a lower portion of salinity than the open sea. For example: the Dead Sea.

Difference between ocean and sea

There are no clear limits or parameters that allow us to differentiate an ocean from a sea, however, a fundamental difference between the ocean and the sea is that The seas are mostly in the vicinity of land while the oceans do not. In addition, they tend to be shallower and have warmer temperatures than the oceans.

The International Hydrographic Organization lists the seas and oceans around the world and marks that there is a difference between the two, but without any additional characteristics.

• Oceans

Main seas of the world

The International Hydrographic Organization gathered in its work Limits of Oceans and Seas (1953) more than sixty seas around the world. Some of the most extensive and recognized are:

• Caribbean Sea. It is one of the largest seas in the world with 2.7 million km². It is located east of Central America and north of South America.
• China Sea. It is located on the eastern coast of Asia and has an area of ​​3.5 million km². It is made up of islands and surrounds the coasts of countries such as China, Taiwan, Indonesia, Malaysia and the Philippines.
• Mediterranean Sea. It is a continental sea that is surrounded by Europe, Asia and Africa. It has an area of ​​2.5 million km² and its coasts are a great point of tourist attraction.
• Arabian Sea. It is located in southern Asia and is the largest sea in the world with 3.8 km². It is surrounded by countries like India, Pakistan, Oman and Yemen.
• Bering Sea. It is located north of the Pacific Ocean and has an area of ​​2 million km². It surrounds the coasts of Russia and Alaska, in the United States.

Other seas in the world are: the Black Sea, the Red Sea, the Baltic Sea, the Sea of ​​Japan, the North Sea, the Greenland Sea, the Beaufort Sea, the Adriatic Sea, among others.

Importance of the seas

More than half of the Earth's surface is covered by seas and oceans, so the conservation of these water masses is essential for the development of the Earth. The seas They are the habitat in which numerous animal and plant species live.so the care and conservation of the sea is essential to maintain the biodiversity that lives there.

The seas are important because of their diversity and also because They have among their functions to absorb carbon and supply a large amount of oxygen that is necessary for life on Earth. Furthermore, the seas are one of the fundamental pieces of the water cycle and provide living beings with this resource.

Sea much of the human population's food is obtained and it is one of the main sources of water. This environment is used by humans as a means of commerce and tourism and recreational activities are carried out there, such as water sports, and its coasts and beaches are used.

Due to the importance of the sea on the planet, it is essential that during the different practices or activities carried out in the marine environment the natural balance of this environment is not altered.

Pollution of the seas

Pollution of sea water is one of the great concerns of the 21st century. This pollution has various sources and affects both seas and oceans.

Some of the main forms of pollution of the seas are:

• Oil pollution. Oil spills that occur in the seas not only contaminate the water, but also affect the organisms that inhabit that natural environment.
• Plastic pollution. Plastics that are dumped into the sea take a long time to disintegrate and usually remain floating on the sea surface, which constitutes a risk for animal species that may mistake the waste for food.
• Residual contamination. There are many types of waste that are dumped indiscriminately into the sea. Some are untreated waste, others are fertilizers carried from the ground into waterways, and others are industrial waste. In some cases, these wastes are toxic.

Many non-profit organizations carry out campaigns to raise awareness about the importance of the sea and the consequences of its pollution. It is essential that organizations, governments and each person from their place contribute to maintaining the balance of the seas.

References:

• “About IHO” in International Hydrographic Organization.
• “The seas of the world” at AQUAE Fundación.
• “Why are oceans and seas important?” in CLME Plus.
• “Biodiversity and marine ecosystems maintain the health of the planet and sustain social well-being” at the UN.
• “Oceans” in Greenpeace.
• “Conserve and sustainably use the oceans, seas and marine resources” at the UN.