Sargassum Seaweed

What is Sargassum?

Sargassum is a genus of large brown seaweed (a type of algae) with berry-like air bladders that float in island-like masses that never attaches to the seafloor. These “berries” are actually gas-filled structures, called pneumatocysts, which are filled mostly with oxygen. Pneumatocysts add buoyancy to the plant structure and allow it to float on the surface. This floating habitat provides food, refuge, and breeding grounds for an array of animals such as fishes, sea turtles, marine birds, crabs, shrimp, and more. 

This natural element of the marine environment is carried close to shore by the currents and deposited along the shoreline with each incoming tide. The amount of seaweed that accumulates on our beaches varies seasonally, with higher than average accumulations observed from late spring into the fall months. Over the last few years, the volume of this seaweed has been increasing.

Sargassum is an important and key part of the ecological system.  The seaweed helps re-nourish the beach and keep it wide. If you take a close look at the clumps of seaweed you will find that it is teeming with sea life.

Seaweed washed ashore

Closeup of seaweed

Where does it come from, and why is it washing ashore?

Most sargassum grows off the shore of the Gulf of Mexico. Like all plants, it needs nitrogen, phosphorous, and sunlight to survive. In recent years, the sargassum has had its fair share of nitrogen, thriving on large amounts of fertilizer from the runoff of the Amazon River. The seaweed can also increase when upwelling in the eastern Atlantic brings cooler water and nutrients from the bottom of the ocean to the surface.

As the sargassum grows, it starts moving along ocean currents, which transport it from the Gulf to the Florida Current via the Loop Current, and then on to the Sargasso Sea, Tropical Atlantic, and the Caribbean. If winds are strong, it can end up near the Sahara desert, the Amazon River, or here on the Florida coast, bringing problems when it arrives en masse.

Beach Raker driving down shoreline

Is anything being done to clean it?

While the City of Deerfield Beach performs daily beach clean-up efforts, we need to be very careful not to affect turtle nests during turtle season (March 1 - October 31). For that reason, the Florida Department of Environmental Protection (DEP) has made mandatory guidelines that all cities and counties must follow:

  1. During turtle nesting season, any mechanical beach cleaning activities shall be confined to daylight and shall be limited to the average high tide mark line or debris line. 
  2. During turtle nesting season, a daily marine turtle survey is conducted before any cleaning can take place. Such surveys shall be completed after sunrise. Sometimes, based on the Broward County survey schedule, it is conducted AFTER people have already set up on the beach for the day. Unfortunately, that limits the mobility of the mechanical raker and limits the area that can be cleaned based on sunbathers. 
  3. In the event that turtle markers are lost for any reason, including vandalism or high water conditions, no mechanical beach cleaning shall be conducted until the nest has been identified and the marker restored. In the event that the nest cannot be relocated, the Broward County staff is to determine if beach cleaning can resume.

Additional Information