Common Water Weeds – Sargassum

If you commonly visit Florida beaches, you’ve likely experienced the effects of Sargassum.  This genus of macroalgae (seaweed), started making headlines back in 2015 when huge amounts of it started piling up and decaying on Caribbean island beaches such as the Dominican Republic, Barbados, Antigua, and Tobago. Then it hit the Caribbean coast of Mexico, and has also started appearing in large quantities on some Florida beaches. Hundreds of beaches have been affected while others remain clear depending on location.

Scientific Name: Sargassum. There are more than 300 different species of Sargussum.

Origins: Sargassum is a totally natural, brown, “bushy” seaweed. Because it’s not exotic, there are many species that have essentially been around forever. The Sargasso Sea is a portion of the Atlantic Ocean well-defined not by land boundaries but by ocean currents (on the west by the Gulf Stream, on the north by the North Atlantic Current, on the east by the Canary Current, and on the south by the North Atlantic Equatorial Current). It was given its name in the 15thcentury by Portuguese explorers because it reminded them of the wooly rock rose often found growing in the water wells of Portugal, where it was called sargaço. The currents defining the Sargasso Sea result in large amounts of Sargassum being present there.

Habitats: The various species of Sargassum can be found throughout temperate and tropical oceans. It typically likes shallow water and coral reefs. Some species grow attached to rocks and reefs but are broken loose during rough weather. Other species are able to thrive without ever being attached to anything.

Eco-Impacts: When it’s out on the water, Sargassum does serve as a food source for some species of herbivorous fishes and sea urchins. The seaweed patches also provide vital habitat to more than 100 species of various arthropods (shrimp, crabs, etc.), worms, mollusks, fish and even sea turtles. But when it washes ashore, it can become a serious problem. As described on the Sargassum Wikipedia page: “The algae wash ashore, pile up on beaches, and decay, often causing a foul odor, releasing fumes of Sulphur compounds that rust metals, can turn taps black in shore houses, damage modern conveniences, and cause respiratory problems, particularly for asthmatics. A doctor in Guadeloupe recorded 52 patients as having Sargassum-related symptoms. Insurance problems arise for tourist operators and homeowners, where the household and business losses do not fall into previous insurance categories. Wildlife also suffer; for example, sea turtle hatchlings die on their way to open water.” These giant mats of the seaweed can also pick up a lot of ocean garbage that can be hazardous to humans and animals alike. As for what’s causing the Sargassum infestations that clearly have a huge negative impact on tourism and local fishing operations, at this point there are only theories. Warmer water temperatures and shifting current patterns, both of which might be driven by global warming and climate change may be the blame, as well as increased nutrients from agricultural fertilizers that eventually wash into the ocean.