Sargassum is commonly thought of as a mass of seaweed, but it is actually a brown algae that floats in the open ocean by gas-filled spheres, called pneumatocysts, found within its leaves and branches. It commonly refers to a genus of about 150 species of brown algae, belonging to the family Sargassaceae.
It is more than just a complex raft of algae; it’s a floating ecosystem. It got its name from where it was originally discovered: by Portuguese sailors in the Sargasso Sea.
Location & Formation
The Sargasso Sea spans over 600 miles wide and is over 1,800 miles long in the South Atlantic Ocean. This sea is unique in that it has no land borders but is rather formed by dynamic ocean currents, called an ocean gyre.
This unique sea is home to Sargassum which is holopelagic, meaning that this type of algae is free-floating and reproduces in the Sargassum mats rather than on the seafloor like most other seaweed.
The Sargassum Biomass
These dense brown algae mats house a vast diversity of marine species in and about the Atlantic Ocean, the Gulf of Mexico, and the Caribbean. It provides critical habitat for marine life including invertebrates, fish, turtles, fungi, and epiphytes. Over 100 species of invertebrates utilize the algae rafts as a food source and habitat.
Over 100 species of fish live in this brown algae; many make use of the mats in varying ways, from nurseries for egg laying to foraging to the refuge to living their entire lives within the floating ecosystem.
Some examples are the Sargassum fish, gray triggerfish, Sargassum frogfish, mahi mahi, amberjacks, marlin, tuna, and even sharks. This concentration of marine life attracts larger predators.
Many other oceanic creatures call these floating mats home too, including eels, worms, crabs, shrimp, and snails.
There are four species of sea turtles (loggerhead, hawksbill, green, and Kemp’s ridley) that use these brown algae mats as juvenile nurseries for foraging and seeking shelter.
Some marine birds that take advantage of the sargassum also include gulls, terns, plovers, godwits, and willets. Depending on where these seabirds live and forage, they may seek out the floating mats, or they might take advantage of the masses of algae that wash ashore.
Reproduction
Sargassum reproduction occurs both vegetatively and sexually. By vegetative means, the process takes place by fragmentation, where the algae break into pieces. Each individual piece then becomes a new plant with division and growth, remaining identical to the parent plant.
Sargassum uses the process of sexual propagation. Much like in humans, the female gamete (egg) is enlarged and immobile, while the male gametes (sperm) are small and motile. This fusion of female and male gametes gives the occasion for a new organism.
This brown algae reproduces and grows faster in warmer temperatures.
When is Sargassum Good vs Bad?
Although we’ve spoken about the abundant habitat it nurtures, sargassum is not always great for the environment. Let’s see some examples of when that might be the case:
Good
Sargassum assists with cleansing the water and absorbing carbon dioxide. Yet, if it doesn’t succumb to its weight and sink to the depths as a source of nutrients for marine life below, it inevitably finds its way to shore.
Once beached, this brown algae is far from useless. Depending on the scale of the stranding, it can act as a bulwark against erosion, nourishing dune plants and gradually restoring ravaged shorelines by tempering the harsh effects of wind and waves.
Rising ocean temperatures increase its growth, presenting a unique opportunity for industry application. Research has explored ways to harness this abundance for a myriad of purposes. From natural fertilizer and biofuel to skincare products and livestock feed, it has even been used in traditional Chinese medicine dating back to the 8th century.
Bad
While Sargassum has a few benefits, overwhelming quantities have become a frequent sight on our shores. Massive rafts can smother seagrasses and coral reefs before ultimately washing ashore, transforming into decomposing mounds of algae and biomass that give off a sulfuric acid and rotten egg smell.
The impact on tourism is undeniable as vacationers are deterred from beaches. Moreover, these dense mats of vegetation pose an obstacle for nesting turtles, hindering their ability to find suitable nesting spots and obstructing the path of hatchlings.
Resorts and local authorities are grappling with this predicament, seeking the least harmful methods to remove excess Sargassum. Some accumulations can reach depths of three feet or more, making heavy machinery a risky option that could damage vital nesting sites for birds and turtles.
Left unattended, the decomposing algae releases nitrogen and phosphorus, contaminating groundwater. In large quantities, it can even accelerate beach erosion. Most removal efforts rely on careful manual labor, utilizing wheelbarrows to preserve essential habitats and coastal ecosystems.
FAQs
What does Sargassum smell like?
Out in its normal habitat, Sargassum smells like any other seaweed. However, this changes when the raft of algae washes ashore and begins to decay. It is then that it starts to give off hydrogen sulfide gas, smelling like rotten eggs.
Can Sargassum be eaten?
Certain species of Sargassum can be eaten and have been used in Chines medicines for centuries. It can be boiled, fried, steamed, or dried. It can also be used in livestock feeds, as it’s rich in carbohydrates and amino acids.
Can Sargassum be burned?
Sargassum burns clean, producing less dust and smoke, making for a longer burn. In some Jamaican communities affected by large batches of Sargassum beaching itself, families are using the algae as a biofuel to cook the traditional jerk style or seasoning and cooking meat.
