Sargassum, also often referred to as seaweed, is a naturally occurring seaweed that floats freely on the ocean surface and is abundant in the Atlantic Ocean and the Gulf of Mexico. It provides crucial habitat for many marine species, including endangered sea turtles, which, upon hatching on our beaches, make their way out to the sargassum to spend their juvenile years feeding and growing amongst the seaweed mats. It is also an important element in shoreline stability. Sargassum also provides nutrients to the shoreline and can replenish areas that suffer beach erosion due to hurricanes and storms, thereby helping to keep our shorelines resilient.
Over the past several years, South Florida and the Caribbean have experienced high levels of sargassum in coastal waters and on local beaches. Excessive amounts of sargassum in populated areas are causing concern worldwide.
Maintaining our beautiful beaches remains a priority for Miami-Dade County Parks, Recreation and Open Spaces Department. During Sargassum season clean-up crews operate on a daily basis to remove the buildup of seaweed on the water line. Below are frequently asked questions on sargassum, for your information.
Sargassum is a brown seaweed with berrylike air bladders, typically forming large floating masses. This brown seaweed is naturally occurring and is abundant in the Atlantic Ocean and the Gulf of Mexico. It provides crucial habitat for many marine species, including endangered sea turtles which, upon hatching on our beaches, make their way out to the Sargassum to spend their juvenile years feeding and growing amongst the seaweed mats.
It comes from the largest bloom of macroalgae in the world, the Great Atlantic Sargassum Belt (GASB), which blankets the surface of the tropical Atlantic Ocean from the west coast of Africa to the Gulf of Mexico. Impacts of warmer water temperatures and nutrient availability both from human-derived (deforestation and fertilizer) and natural sources (upwelling of deep-water nutrients to the surface) also cause the accumulation of Sargassum.
Sargassum season runs from March through October, and Sargassum now aggregates almost every year, starting in January/February in a massive belt north of the Equator, along the region where the trade winds converge. During the late winter and early spring months, Sargassum moves northward due to seasonal winds and currents. Later, in late spring and summer, this Sargassum belt may stretch across large portions of the Atlantic Ocean and drift into the Caribbean Sea and Gulf of Mexico via the North Equatorial and Caribbean current systems.
Sargassum has flourished in recent years due to the combination of increased nutrient runoff from the Amazon River, upwelling off the western coast of Africa, and changing water temperatures. According to scientists, Sargassum mats were first reported in the center of the North Atlantic during the 15th century, but these have historically been limited and discontinuous. In 2011, for the first time, the Sargassum mats in the Atlantic had grown to form a 5,550-mile-long belt extending from West Africa to the Caribbean Sea and Gulf of Mexico. Since then, the mats have become longer and more dense.
During Sargassum season, winds and currents push Sargassum ashore. The greatest accumulations of Sargassum on our beaches often happen during high tide, which we experience twice a day. Miami-Dade Parks, Recreation, and Open Spaces Department (PROS)’s Beach Operations crews generally tackle Sargassum early in the morning, prior to when the majority of beachgoers have arrived at the beach. Unfortunately, when the second tide arrives in the afternoon, depending on the winds, it often brings another wave of Sargassum to the shoreline.
According to the Florida Department of Health (DOH), the Sargassum itself is not harmful to the skin, but tiny sea creatures that live in Sargassum can cause skin rashes and blisters. As Sargassum decomposes, it also gives off a substance called hydrogen sulfide. Hydrogen sulfide has a very unpleasant odor that resembles rotten eggs, and this can irritate the eyes, nose and throat. If you have asthma or other breathing illnesses, you may be more sensitive to these symptoms. However, the levels of hydrogen sulfide in an area like the beach, with large amounts of airflow, are not expected to be harmful.
To protect yourself and your family from exposure to Sargassum, DOH advises the following:
- Always supervise children at the beach.
- Avoid touching or swimming near seaweed to avoid stinging by organisms that live in it.
- Use gloves if you must handle seaweed.
- Stay away from the beach if you experience irritation or breathing problems from hydrogen sulfide—at least until symptoms go away.
- Close windows and doors if you live near the beach.
- Avoid or limit your time on the beach if you have asthma or other respiratory problems.
We are monitoring evolving literature on the relationship between Sargassum and Vibrio vulnificus bacteria, including a recent study that suggests that this bacteria can “stick” to microplastics which increasingly live in our oceans and can become lodged in patches of Sargassum. According to the Florida Department of Health, people can get infected with Vibrio vulnificus when they eat raw shellfish, particularly oysters. The bacterium is frequently isolated from oysters and other shellfish in warm coastal waters during the summer months. Since it is naturally found in warm marine waters, people with open wounds can be exposed to Vibrio vulnificus through direct contact with seawater.
To reduce your chance of getting a Vibrio wound infection, DOH recommends the following:
- Water and wounds do not mix. Do not enter the water if you have fresh cuts or scrapes.
- Individuals who are immunocompromised, e.g. chronic liver disease, kidney disease, or weakened immune system, should wear proper foot protection to prevent cuts and injury caused by rocks and shells on the beach.
Water quality can be impacted by the decomposition of Sargassum. The Florida Department of Health (FDOH) monitors bacteria levels at the County's beaches through their Healthy Beaches program through the collection of water samples at various locations. The Miami-Dade County Division of Environmental Resource Management (DERM)'s surface water quality monitoring program also collects data across Biscayne Bay's watershed at over 120 locations, but these locations do not include recreational beaches. This program collects a range of water quality parameters monthly and these are entered into the state's water quality database.
- Although the conditions that are driving the abundance of Sargassum on our beaches today are expected to improve around October or November, the great Atlantic Sargassum belt may be the "new norm," according to a recent report by the American Association for the Advancement of Science. This means that Sargassum may become a regular sight on South Florida beaches during “Sargassum Season” (March through October).
Miami-Dade County has implemented an adaptive management strategy to manage Sargassum along its beaches under a permit issued by the State of Florida Department of Environmental Protection (FDEP). On a daily basis, along 17 miles of county beaches, the County's Parks, Recreation, and Open Spaces Department (PROS) Beach Operations team drives tractors with rear mounted blades along the shoreline at the high tide mark to mix and blend the Sargassum. This daily maintenance takes place along beaches from Government Cut to the Broward County line, and at Crandon Park beach.
In addition, at four state-approved “hot spot” locations that frequently experience heavy Sargassum buildup, a Miami-Dade County vendor removes Sargassum with specialized tractors that utilize barber rakes. These locations are:
- North of Haulover Cut
- South of Haulover Cut
- 22nd Street through 32nd Street in Miami Beach
- North of Government Cut jetty
Maintaining our beautiful beaches is a priority for Miami-Dade County, and approximately $9,600,000 is budgeted each year to maintain our beaches for residents and visitors, of which $3,900,000 is allocated specifically for Sargassum removal.
The excess Sargassum that is removed from specific areas of the beach pursuant to the Florida Department of Environmental Protection (FDEP) permit is transported to an approved County property. Once there, the Sargassum is allowed to dry and reduce in volume before it is disposed at an appropriate landfill.
Miami-Dade County is working with FDEP to identify a path forward on beneficial reuses of Sargassum, including requirements related to composting. The County is also calling on our state and federal government partners to allocate additional resources for Sargassum clean-up and research. As part of our long-term plan, Miami-Dade County is looking for innovative new solutions and technology to help us more efficiently manage Sargassum, including identifying potential beneficial reuses. To that end, the County recently issued Request for Information (RFI) EVN0000654 to solicit input regarding innovative and expedited ways to address current and future excessive Sargassum and process it for beneficial use. This solicitation process closed on May 19, 2023 and the County is currently evaluating responses.
The Florida Department of Environmental Protection (FDEP) regulates mechanized beach cleaning under the Florida Beach & Shore Preservation Act, Florida Statute Section 161. All Sargassum management by the County and its vendors must follow FDEP regulations.
During sea turtle nesting season, which runs from May through October and overlaps with the majority of Sargassum season, the use of heavy equipment to manage Sargassum on the beach is only allowed by special permit. During these months, the County's Parks, Recreation, and Open Spaces Department (PROS) works closely with FDEP and the Florida Fish and Wildlife Conservation Commission (FWC) to secure the required beach cleaning permits. To protect marine turtles, their nests, and hatchlings, every morning, prior to operating heavy
machinery on the beach, PROS' Sea Turtle team surveys for sea turtle nests and marks them for their protection. Once the survey is complete, the Beach Operations team proceeds to mechanically rake the beach. In higher density areas where marking every nest is not feasible, non-mechanical methods of cleaning, such as hand raking, may be necessary.
For more information on FWC guidelines, please read FWC Beach Cleaning Guidelines.
Sargassum, in normal amounts, provides habitat, food, protection, and breeding grounds for hundreds of diverse marine species, including commercially important species such as tuna and swordfish, that feed on the smaller marine life present in Sargassum mats. Normally, Sargassum may help to avoid beach erosion by catching windward sands. State and federal environmental resource agencies regulate the removal of the Sargassum from within the water. These agencies have not approved wholesale removal based on the ongoing benefits that Sargassum provides to the environment.
The “Seaweed Removal and Mechanical Beach Cleaning Solicitation RFP-01385" was competitively bid on October 7, 2019. The current contract is set to expire on April 30, 2025, at which point another competitive bidding process will take place. View the original bid documents.
The current “Seaweed Removal and Mechanical Beach Cleaning Agreement” (Agreement) provides for daily Sargassum removal in the “hot spot” areas identified in Appendix A - Scope of Services, Section 1, Background, subsections A., B., and C., as well as any additional locations requiring service at the discretion of the County as further set forth in Appendix A, Section 2.7, Addition and Deletion of Locations. For the remaining sections of the beach, Miami-Dade County's FDEP-approved beach cleaning permit allows the use of tractors with rear mounted blades to mix and turn the Sargassum along the high tide mark.
The beach cleaning schedule is outlined in the Agreement at Appendix B - Price Schedule, Section A., Payment Schedule. The schedule for Sargassum removal was developed to cover the extensive required level of service at the identified locations from March through October based on prior historical information. Other months are addressed as required. From March through October, the Contractor shall work a seven (7) days per week operation. During the months of November through February, the Contractor shall work as needed on a daily/weekly/monthly basis as determined by the County.
The contracted vendor works in the hot spot areas from early in the morning until the area is deemed unsafe to operate heavy equipment due to the volume of beach patrons in the area. It is not feasible to operate the necessary equipment later in the day due to the larger number of beachgoers, as removal operations would require additional resources, including the assistance of public safety officers to close sections of the beach for tractors to operate safely along the shoreline. During those times of year when the accumulations of Sargassum are greater, the County's contract provides for additional services as needed pursuant to Appendix A, Sections 2.6, Additional Services, and 2.7, Addition and Deletion of Locations, of the Agreement. View the original bid documents.
Miami-Dade County staff meets regularly with County partners from Monroe County to Martin County as well as members of our academic community to discuss strategies related to managing Sargassum. In addition, Miami-Dade County staff meet with the State and federal agencies as needed to discuss the regulatory requirements associated with the removal, handling and disposal of Sargassum. To learn more about the approaches that our local, state, and federal partners are taking, and for information being provided by those partners, you may visit their dedicated websites below:
- Broward County Natural Resources Division Sargassum
- Palm Beach County Environmental Resource Management, Beaches
- Monroe County Parks & Beaches
- Florida Fish and Wildlife Conservation Commission (FWC) Sargassum Bloom
- University of South Florida (USF) Optical Oceanography Laboratory Satellite-based Sargassum Watch System (SaWS)
- National Oceanic and Atmospheric Administration (NOAA) Atlantic Oceanographic and Meteorological Laboratory CoastWatch Sargassum Inundation Risk