The Sargasso Sea: A Unique Marine Environment
In the North Atlantic, roughly 590 miles east of Florida, a patch of water stands out for its calmness. Surrounding currents are strong, creating a distinct boundary. Within this ring lies the Sargasso Sea, an area of ocean remarkable for its different behavior compared to nearby waters.
Atop the surface, there’s golden-brown seaweed known as Sargassum, which floats thanks to tiny gas-filled bladders. This seaweed forms loose mats, riding the waves rather than sinking.
Numerous creatures like shrimp, bright young fish, and pale crabs navigate through these mats, finding food and shelter. Interestingly, the Sargasso Sea is the only sea named for a plant instead of a coastline.
Sailor Stories of the Sargasso Sea
Long before technology like satellites and ocean sensors existed, sailors encountered this peculiar region. Christopher Columbus noted in 1492 the fear of being stuck in these calm waters, worrying that the ships might “never again feel a breath of wind.”
Unknown to them, beneath the serene surface lay a vigorous system of currents. They were traversing the North Atlantic subtropical gyre, a massive loop that transports water from various latitudes.
These currents trap floating materials, explaining why Sargassum collects in this area. It also sheds light on the unique characteristics of this sea.
Flora and Fauna of the Sargasso Sea
From above, the Sargasso Sea resembles an expansive plant nursery nearly 800 miles wide. Scientists refer to these drifting mats as “habitat islands,” providing crucial shade, hiding spots, and food at the ocean’s surface.
Many animals, typically exposed in open waters, can seek refuge among the seaweed, avoiding predators. Porbeagle sharks glide near the edges of the mats, while Bermuda storm-petrels skim just above the water’s surface to snatch shrimp and small fish.
Surveys have identified over a hundred invertebrate species residing on Sargassum mats for their entire lives, until the mats eventually disintegrate. European and American eels start their journey as transparent larvae beneath the seaweed, riding currents either westward or eastward, depending on the species.
As they mature, they change and migrate into rivers, some venturing as far inland as Indiana, where they can live for decades in freshwater. Once matured, these eels swim back to the ocean, embarking on a 3,000-mile trek to spawn in the Sargasso Sea before they die. It’s fascinating that they return to the same vast region despite having no visible landmarks to guide them—a mystery that continues to baffle scientists.
Climate Impact of the Sargasso Sea
The Sargasso Sea contributes to the Earth’s climate system as well. In summer, temperatures rise to 82–86 °F, while in winter, they drop to approximately 64–68 °F. Warm, salty water flows north, while cooler water moves south.
This thermohaline exchange helps stabilize weather patterns across both sides of the Atlantic by influencing heat and moisture distribution in the atmosphere.
The open waters also absorb carbon dioxide, which tiny plankton utilize to build their shells. Upon death, their shells sink, effectively sequestering carbon and keeping it out of the atmosphere for extended periods.
Data collected since the 1950s near Bermuda shows that average temperatures in these waters have increased by about 1 °C since the 1980s. Warmer surface layers hinder vertical mixing, resulting in lower oxygen levels at depth and fewer nutrients rising to support plankton.
Taken together, research from drifting Argo floats and satellite scans positions the Sargasso Sea as a critical site for studying ocean acidification in the Atlantic.
A Trap for Atlantic Ocean Debris
Because the Sargasso Sea is centrally located among various surface currents, it has become a collection point for floating debris from the North Atlantic. These converging currents gather plastic bags, bottle caps, and derelict fishing gear within the swirling waters.
One survey estimated around 200,000 pieces of debris per square kilometer—about 518,000 pieces per square mile—spread over hundreds of miles. Underwater microphones capture the noises of cargo vessels as they cut through Sargassum mats, drowning out the lower-frequency calls of passing sperm whales while entangling juvenile turtles.
Policies for the Sargasso Sea
The Sargasso Sea Commission, established in 2014, has labeled this region a “haven of biodiversity.” It urges nations to direct ships around dense Sargassum mats and to establish marine protected areas. Additionally, governments are working on a treaty aimed at reducing plastic waste in the ocean while preserving important migratory corridors that traverse or border the Sargasso Sea.
Any changes in this “sea without shores” would have far-reaching consequences. If the Sargasso Sea were to alter its unique conditions, eels traveling from rivers in Newfoundland to the Gulf of Mexico might find an oceanic birthplace vanished due to warming. Humpback whales could arrive in the spring to discover their feeding areas depleted. Weather patterns over Europe might shift, and the Atlantic could absorb even more excess heat.
While it may appear to be just an empty blue expanse on a map, the Sargasso Sea plays a crucial role in both Earth’s climate and its marine ecosystems. The stillness of the water delivers a vital message: we must take steps to preserve this tranquil region or brace for increasingly intense and unpredictable changes.
