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The Sargasso Sea

The Sargasso Sea is located around the Bermuda Islands between Florida and the Azores in the southwestern North Atlantic and partly belongs to the area of the Bermuda Triangle. (Foto: NASA, SeaWiFS)

The Sargasso Sea is located around the Bermuda Islands between Florida and the Azores in the southwestern North Atlantic and partly belongs to the area of the Bermuda Triangle (see: ”Story” Atlantic Ocean). The sea has roughly the size of Australia.


The Gulf Stream and the North Equatorial Current encircles the Sargasso Sea, causing the oval-shaped sea to flow in a slow, clockwise drift. Both currents push warm water into the Sargasso Sea, which keeps the sea warm. Due to the rotation forces of the currents, the center of the Sargasso Sea is about one meter above the level of the surrounding Atlantic Ocean.


The warm currents also affect the weather in the area. It remains - like the water - mostly very calm, humid, and often stifling hot. Due to the hot temperatures, the Sargasso Sea has a high evaporation rate. However, the lack of rainfall fails to add fresh water into the sea, which causes a very high salinity.


The Sargasso Sea is named after the yellow-brown seaweed called Sargassum that is found there in great abundance. About eight species of seaweed occur in the Sargasso Sea. In the late 15th century the seaweed was named by Portuguese sailors who noticed the resemblance of floating Sargassum to a type of grape called ‘Salgazo’.


The sunlight deeply penetrates the clear blue waters of the sea supporting the abundant plant and animal life existing in this part of the Atlantic Ocean. Although about one third of the Atlantic's plankton is produced here, the Sargasso lacks the nutrients to significantly attract commercially valuable fish. However, many small marine animals like tiny crabs, shrimp and octopuses live on and in the partly dense mesh of Sargassum (seaweed species) on the water surface.


The Sargasso Sea is characterized by two different biological mysteries: the seaweed sargassum natans, and the eels, returning every year to this part of the Atlantic Ocean. In the 18th and 19th centuries, people wondered why there could no baby freshwater eels ever be found in Europe or America. This mystery was finally solved by a Danish biologist in the early 20th century. The answer leads to the Sargasso Sea.


Freshwater eels from Europe and the American continent will migrate to the Sargasso Sea at the age of about 10 years. They swim down rivers and creeks and even slither overland across wet meadows in their need to reach the Sargasso Sea. The eels have small capillaries under the skin to absorb oxygen directly from the surrounding air and they are protected from drying out by a thin layer of mucus.


Once arrived to the Sargasso Sea, they mate and the female eels will spawn their eggs – each up to 20 million - in the 20°C warm water. Then the female eels die. The eggs turn into very thin and flat, 6 millimeter long and almost transparent creatures feeding plankton with their small mouths. The ocean Gyre of the Sargasso Sea carries them around for the next three years. They grow to a size of about 80 millimeter. Then they migrate towards the continents and begin to gather in huge numbers at the mouths of rivers in order to migrate upstream.



Main islands

Bermuda Islands



Boundaries no continental coastlines
Areal extent and water depth:  
Total area > 3 Mill. km2
Maximum depth ~ 7,000 m
Hatteras and Nares abyssal plains > 5,500 m depth
Major Rises:  
Bermuda Rise < few 100m below sea level
Researcher Sea Mounts ~ 1,000m above sea floor
Surface water temperature mostly about 18°C
Air temperature > 20°C
Surface water salinity ~ 36.5 to >37 ‰

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