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- Last Updated: Tuesday, 20 September 2016 11:45
Bermuda Alliance for Sargasso Sea (BASS)
Nature created something quite unique when she placed the picturesque islands of Bermuda in the fringe of the Sargasso Sea entirely secluded from any neighbouring island or continent. There are many fascinating and unique stories to tell about our islands rich and diverse culture and our remarkable oceanic environment but the Sargasso Sea in which we soak is a worthwhile narrative in itself.
Since its discovery 520 years ago by Christopher Columbus, the Sargasso Sea has gotten more than its fair share of negative press. With ships’ crews fearing their vessels would get entangled in the massive mats of seaweed and sailors reporting days spent adrift in the windless doldrums not to mention tales of the Bermuda Triangle, the Sargasso Sea was more the topic of legend and lore than scientific journals. But that’s all changing now that scientists are beginning to fully understand this dynamic open-ocean ecosystem and appreciate what Sylvia Earle called “the golden rainforest of the ocean”.
The Sea's uncannily calm properties are in complete contrast to the oceans around it which declare some of the strongest currents in the world; the Florida, Gulf Stream, Canary, North Equatorial, Antilles, and Caribbean currents. These interconnect to separate this sea from the rest of the tempestuous Atlantic almost like the eye of an enormous, and very slow, enduring hurricane which ensures the body of water within meanders slowly in an endless clockwise drift.
The Sargasso Sea is so named because of algae called Sargassum which lazily floats over its 5 million km2 expanse. The two most abundant species are Sargassum fluitans (broad-toothed gulfweed) and Sargassum natans (common gulfweed or spiny gulfweed) are unique among seaweeds because they are “holopelagic”, meaning they spend their entire life cycle free-floating in the water, never attaching to the bottom even for reproduction. Mats of interwoven self sustaining seaweed, embellished with their own floatation system, drift on the high seas and shelter a unique and remarkable community of open ocean animals. The fronds of the Sargassum are the only solid natural surface for hundreds of miles and therefore the only place where sedentary animals caught in the north Atlantic gyre can become attached. Living in abundance on, within and below the weed are a host of critters specially adapted to this unique habitat which provides refuge for over 145 species of invertebrate and 125 species of fish found only in this floating golden oasis.
Many of the animals have developed the art of camouflage to the point where they are practically indistinguishable from the surrounding seaweeds and others exhibit remarkable lifestyles which have also evolved for survival tied to this habitat. The fish you see here in camouflage garb waging guerrilla war in the Gulfweed jungles is a member of the anglerfish family. This Sargassum Fish sports a fleshy rod on its nose which it wiggles to lure prey fish (not infrequently its own smaller brethren); once within reach they are sucked into its ‘vacuum cleaner’ mouth. A master of stealth and deception, the Sargassum Fish has pectoral fins shaped and functioning like hands with which it grasps and pulls, swinging and climbing, often upside down, through its leafy realm. Take it into open water, and it will squirt water from round gill openings to propel itself, jet-like, as fast as it can, back into the safety of the yellow-brown thicket.
The seahorse, often associated with floating mats of Sargassum, gives its fishy nature away only because of a nervously fanning dorsal fin. Add to this a prehensile tail like a chameleon’s and a carapace like an armadillo’s, and you end up with a seahorse. But not only is this strange contraption perfectly viable, spending its days with the tail wrapped around algae and using its puckered mouth to suck up small crustaceans, it also has a rather unique family life. Unlike most other fishes, which release eggs and sperm simultaneously into the water, leaving their offspring to fend for themselves, seahorses eggs are incubated in the males’ brood pouch – it’s not mom but dad who is pregnant. Since it is the size of the male’s brood pouch which determines the number of young that can be successfully reared, rather than the female’s capacity to lay eggs, as in most other species, seahorse ‘stallions’ find themselves in the unique position of being hotly courted and jealously escorted by fillies. The second fish in this slide is the straight cousin of the crooked seahorse, the Sargassum Pipefish. It makes its home in floating Sargassum where it feeds on tiny, waterflea-like crustaceans and bristle worms. Quietly maneuvering its minute, toothless mouth close to the target, it suddenly expands its snout cavity, sucking the prey into it like a powerful pipette. Like the seahorse the male pipefish carries and broods the eggs in a pouch and essentially gives birth to hundreds of barely visible pipefish babies.
Resembling a not-quite-round pea with ten legs, this little crab will watch you with stalked eyes then suddenly dart away as you are trying to grab it – provided you can find it at all in its home the Sargassum. Generally yellowish-brown, it is extremely variable in colour. Some individuals sporting conspicuous white blotches that possibly mimic the sea mosses which dot the same community.
Judiciously picking its way through the Sargassum tangle, this raggedy slug feeds on minute hydroids (relatives of the Fire Coral), that form slender tree-like colonies on the seaweed. Since its prey can’t run away the camouflage outfit of the slug is clearly designed to make it invisible to predators from outside its Gulfweed world. Compare the slug’s wing-like projections with the fronds of its host plant to appreciate what a match this is.
The planehead filefish is often the most abundant species in our Sargassum collections. Its color and shape blend seamlessly with the seaweed. Appearing somewhat like squashed trunkfish, filefish are oddly-shaped fish often with dazzlingly cryptic patterns.
The Sargasso Sea is home and nursery ground to all five endangered Atlantic sea turtles. Heading to deep water immediately after hatching from their native beach, baby Green turtle literally get lost until, a few years later, they reappear, 10 pounds heavier, in the shallows of islands at the periphery of the Sargasso Sea. It is now clear that during these “lost years,” juveniles shelter, feed and grow in Sargassum until they settle on islands such as Bermuda to mature. Several decades later they embark on yet another long-distance trek that will take them home to their breeding grounds, usually off the very beach on which they were born themselves.