Sargassum

My childhood memories are full of sunny summer days at Ft. Lauderdale beach. I can still see the mounds of seaweed that had to be stepped over to get to the ocean, and feel the tickle of floating seaweed rubbing against my skin as I swam in the surf.  It was fun to shake out the clusters of seaweed and see the small crabs and shrimp fall from its cover.  There were other things contained in the seaweed such as black tar and the stinging Portuguese man o’ war that had to be watched out for.

At the end of May this year, while seated at the ocean’s edge, those memories came rushing back to me, with a nostalgic filter of course. As a fresh batch of seaweed floated by, I admired how its light brown color was set off by the aqua of the sea and was amused by the exposed coral rocks that seemingly wore seaweed toupees, from fresh weed deposited by the high tide.

Wading birds flock to the seaweed, which is full of life.

Reality check!  A Miami news station had a feature about the FIFA world cup visitors who were turned off by our smelly beaches and weed filled waters.  Not what they expected, especially after coming from across country or from Europe.  The scourge of summer, from the viewpoint of South Florida resort managers, who have to field complaints about the stinky mess from June until September.

Floating mats of fresh seaweed eventually end up onshore and become a hazard that attracts flying insects and carries contaminants and bacteria.  Parents worry when their child has to wade through the junk in order to paddle board, kayak or launch a Hobie Cat. People with respiratory problems are at risk from the release of hydrogen sulfide and ammonia. 

A Great White Heron waiting for low tide when the cove will be shallow enough to wade in. There will be plenty of crabs, shrimp, and small fish to be had in the sargassum accumulated below.

Seaweed, also known as Sargassum, is a brown microalgae that never touches the sea floor, but instead drifts on the surface of the ocean.  Its name Sargassum originates from the Portuguese word sargaço, a type of grape or also a wild vine that grows in willow thickets.  The tiny balls that keep the weed afloat look like grapes. Christopher Columbus encountered a thick mat of weed while sailing in the Atlantic near the Bermuda Triangle, and with light winds prevailing, he feared getting stuck in it. Columbus had encountered the Sargasso Sea, an area that cannot be found on any map, but is defined by the convergence of four major Atlantic currents:  the Gulf Stream, the North Atlantic Current, the Canary Current and the North Atlantic Equatorial Current. 

Seaweed, also known as Sargassum. Its tiny balls keep the weed afloat.

The Florida Keys are one stop along the Great Atlantic Sargassum Belt which spans 5,000 miles from coastal West Africa to South America.  Winds and currents act like a conveyor belt that distributes the seaweed into the Atlantic and Caribbean Sea, and a “loop” current carries the seaweed around the coast of Florida into the Gulf of America. 

NOAA designates sargassum as essential fish habitat, for species including gray triggerfish, amberjacks and mahi mahi.  In the open ocean seaweed provides food or shelter for fish, crustaceans, turtles and seabirds.  When the weed hits the coastal flats, the wading birds flock to its floating mass, which is fresh and full of life.  I netted a bucket of fresh weed and shook it until the critters contained within it fell out.  There were shrimp and crabs galore.  I marveled as the crabs would approach the shrimp and start pinching.  The shrimp were translucent mini-me versions of jumbo shrimp. 

I netted a bucket of fresh weed and shook it until the critters contained within it fell out. There were shrimp and crabs galore.

Harvesting of sargassum is prohibited in U.S. federal waters (between 3 miles to 200 miles from shore.) Sargassum is not protected in Florida, as long as it has washed ashore naturally you can pick it up with your hands or with hand tools.  In State waters up to 100 pounds of sargassum can be removed from canals or nearshore waters with a recreational fishing license.  A commercial saltwater products license is needed to remove  more than 100 pounds according to the FWC.

Once near shore the weed makes its way into man-made canals and marinas and gets stuck. Keys boaters curse the seaweed as it fouls their props and canals get clogged with the weed. The trapped weed sinks, making the canal brown, due to the decaying weed, which depletes the oxygen in the water, resulting in fish kills. 

A boat ramp covered with weed. You must wade through the junk in order to paddle board, kayak or launch a Hobie Cat.

In Ft. Lauderdale small barges would run up and down the canals scooping up the seaweed with a fork.  Removal is a futile process, since the seaweed floats in every day.  Bubblers at the entrance to a canal may help keep it out.

Seaweed has the potential for use as fertilizer; it contains nitrogen, phosphorus and potassium (NPK), the same ingredients found in fertilizer, plus micro-nutrients. Since there is arsenic in seaweed, it might be best utilized on ornamental plants and palms, not food crops.

The weed was so thick the black birds could walk on top of it.