Strange Seas

Ever heard of a sea with no coastline? It sounds like the stuff of legend, but the Sargasso Sea, nestled in the North Atlantic Ocean, is just that—a vast expanse of water without a traditional shore. Unlike other seas defined by their rocky or sandy borders, the Sargasso Sea is surrounded by the swirling currents of the North Atlantic Gyre, creating a unique maritime environment unlike any other.

The Sargasso Sea remains delineated not by land but by a series of powerful ocean currents, including the Gulf Stream, the North Atlantic Drift, the Canary Current, and the North Equatorial Current. The currents converge to form a massive, swirling vortex that isolates the Sargasso Sea from the rest of the Atlantic Ocean. This creates a distinctive marine environment with clear, deep blue waters that can be surprisingly calm due to the protective currents. Christopher Columbus is among the first Europeans to document this peculiar sea during the Age of Exploration. He was struck by the extensive mats of floating seaweed, which he described as forests in the sea. This seaweed, known as sargassum, is crucial in the Sargasso Sea’s unique ecosystem.

The Sargasso Sea, famous for its large floating mats of sargassum seaweed, is a microalgae equipped with tiny, gas-filled sacs that allow it to float. These mats stretch for hundreds of miles and provide crucial habitats for a variety of marine species. The seaweed also acts as a carbon sink, absorbing and storing atmospheric carbon dioxide, which helps mitigate the impacts of global warming. Historically, sargassum is known for serving as a navigational landmark for sailors, helping them to verify their location in the otherwise featureless ocean. However, in recent years, the increasing size of these mats has sparked concerns about their impact on coastal regions. When sargassum mats wash up on beaches, they decompose and release hydrogen sulfide, which can produce a foul odour and negatively affect tourism.

Teeming with life is the sea. There are floating seaweed islands that serve as a critical refuge for many specialised creatures. Some of these species are endemic to the Sargasso Sea, meaning they exist nowhere else on Earth. The sea is home to over 100 fish species, 145 vertebrates, and even ten different types of sharks. One of the most intriguing residents is the sargassum fish, which has evolved to camouflage itself within the seaweed, allowing it to ambush prey with incredible efficiency. The sea plays a key role in the life cycle of eels. These mysterious creatures travel thousands of miles from their European freshwater homes to spawn in the Sargasso Sea. Their young, known as leptocephali, then drift back to Europe, transforming into adult eels along the way.

Indeed, the sea is in a remote location. However, the Sargasso Sea is not immune to human impact. The North Atlantic Garbage Patch, a massive collection of plastic debris, affects the Sargasso Sea, entangling with sargassum mats and posing a threat to marine life. Efforts are underway to address this issue, including initiatives by organisations like The Ocean Cleanup and Five Gyres, which are working to remove plastic waste from the oceans. In 2014, the Hamilton Declaration for the Conservation of the Sargasso Sea was signed by various governments and organisations, pledging to monitor and protect this unique marine environment. This international commitment is crucial for preserving the Sargasso Sea’s ecological balance and ensuring its continued role as a haven for diverse marine species.

The Sargasso Sea truly stands out as a world unto itself—an oceanic oddity characterised by its lack of a traditional coastline, its floating seaweed, and its diverse marine life. Its mysteries and wonders continue to captivate scientists and explorers alike, highlighting the need for ongoing conservation efforts to protect this extraordinary part of our planet's natural heritage.