Best Practices for Managing Beached Sargassum

Why Beached Sargassum Must Be Managed

Any beachfront property with a beach concession from ZOFEMAT has a legal responsibility to maintain that section of public beach.  In other words, property owners are legally obligated to manage any sargassum that washes up on their 20 meters of shoreline.  

All techniques for dealing with beached sargassum have a negative impact on the environment but the absolute worst option is to leave it on the beach where it builds up in a rotting mound that creates a “wall” of sargassum along the shoreline.  These walls not only release toxins that smell awful, are harmful to human health, and have a negative impact on tourism; they also directly contribute to the accumulation of excess sargassum in the bay.  Here’s why:

On any given day during Sargassum Season, local winds and currents push as much as 60 cubic meters of sargassum towards Half Moon Bay.  Even when a barrier is installed and deflecting a lot of this sargassum back out to sea, a daily influx of “residual sargassum” is still expected to get past the barrier and into the bay.  And once it’s entered the bay, this daily influx of sargassum can only exit the water by getting washed up on the beach via natural wave action.  When this natural wave action is impeded by “walls” of sargassum along the shore, new sargassum is prevented from getting washed up onto the beach.

The only way to prevent sargassum build up in the bay is to prevent sargassum build up on the beach!!

Sargassum buildup in the water causes even more environmental damage than sargassum build up on the beach.  Not only do ever growing rafts of sargassum block sunlight from reaching the reef, they also start to rot in the warm shallow waters of Half Moon Bay and release toxic chemicals like arsenic and hydrogen sulfide that can reach concentrations that are even more damaging to marine life than the release of raw sewage into the bay.  

DAILY management of beached sargassum is key to protecting our local marine ecosystem.  And with a barrier in place that deflects up to 70% of incoming sargassum away from the bay, the work of removing the 30% “residual sargassum” from the beach will be much less onerous than relying on manual beach cleaning to get 100% of incoming sargassum off the beach.

How To Manage Beached Sargassum

The goal of sargassum management is not to maintain a white sandy beach throughout Sargassum Season.  The most effective and economical way to manage beached sargassum is by maintaining a thin layer of dried sargassum that never exceeds 8” inches in depth.  This prevents beach erosion while still allowing natural wave action to continue washing sargassum up onto the beach for daily removal.

The left side of this photo shows what the beachfront should look like after daily management of beached sargassum.  The right side shows excess sargassum buildup that requires immediate management:

As soon as Sargassum Season starts, every property owner must inspect the 20 meter length of their beach concession(s) to evaluate how much new sargassum washed up on shore in the last 24 hours.  Depending on the quantity of new beached sargassum, one of the following actions must be taken:

1. DO NOTHING
   If the sargassum on the beach is less than 4” inches deep, no action is required
   
2. RAKE OUT TO DRY ON BEACH
   When sargassum along the water's edge reaches a depth of around 8”, inhouse maintenance staff should be dispatched to rake the buildup away from the breaking waves and spread out to dry on the sand in layers that are less than 8” inches deep
   
3. REMOVE TO DEPOSIT SITE OFF BEACH
   When there is too much sargassum to spread out to dry on the beach, in-house maintenance staff should be dispatched with a wheelbarrow to remove the top layer of sargassum and deposit it in a holding location.  

4. HIRE AN OUTSIDE SERVICE PROVIDER
   When the buildup is more than your in-house maintenance staff can handle in an hour or two, an outside service provider must be hired IMMEDIATELY to remove and truck the sargassum away to an approved sargassum disposal site.  

Here are some additional tips on managing beached sargassum:

• Instruct your property manager to have your in-house maintenance staff inspect the beach at the start of every work day.
  
• Under no circumstances should you allow a sargassum “wall” to develop along the shore.  This will only make matters worse by increasing erosion due to backwash, and increasing the amount of sargassum floating and rotting in the water.
  
• NEVER return sargassum to the water.  Although it is sometimes recommended to return small amounts of beached sargassum to the water, managing this practice among our various individual lots would take greater administrative supervision than can be provided by the HMB Sargassum Project volunteers.
  
• Whenever possible, ensure that daily beach cleaning begins during low tide.
  
•  In general it takes about one hour to manage one cubic meter of beached sargassum and two hours to manage two cubic meters of beached sargassum, etc.  This is true whether the sargassum is being spread out to dry in the sun or removed from the beach in a wheelbarrow.

• For sargassum LESS THAN 8 inches deep, use a rake to spread the it over a wider area to promote drying and desiccation before it starts to rot
  
• If necessary, spray sargassum with <Micro Organismos>, an organic product that slows rotting.  The spray can be used on the beach as well as on piles where sargassum is deposited by wheelbarrow.
  
• When beached sargassum must be shoveled into a wheel barrow, ensure your property manager has instructed workers to AVOID removing the bottom-most, sand-laden layers.
  
• Sargassum piles in temporary holding areas should be spaced and not taller than 50 cm to maximize air flow and drying, and minimize rotting.  
  
• When deposits grow to a height 50cm or more, an outside provider must be hired to truck the waste to an officially sanctioned disposal site where care is taken that toxins released by rotting sargassum do not leach into the mangrove or ground water.
  
• If your property does not have a suitable place to deposit sargassum that’s removed from the beach, please contact EPA Project Manager, Ivan Penie.

IMPORTANT NOTE:  

Unnecessary legal action delayed barrier installation in 2024.  The delay allowed so much excess sargassum to build up in the bay that the benefits of deflection will not be immediately apparent when the barrier is first installed.  Extra beach cleaning will still be required for a few weeks after the barrier goes in.  But once all the excess build up has washed up on the shore and been properly disposed of, sargassum quantities in the water will reach a new, much lower equilibrium.  The work required to manage beached sargassum will be significantly reduced.  

The amount of sargassum in the bay right now represents 100% of the sargassum that’s been coming towards Half Moon Bay since early March.  Once this excess build up is allowed to wash up on shore to get properly disposed of AND as long as daily beach cleaning practices are adopted by all, then on any given day, the amount of sargassum in the water will represent only about 30% of whatever new sargassum might have gotten past the barrier on the previous day.

Here’s a photo showing all the excess sargassum that — thanks to the LEGAL SHENANIGANS OF IF NEIGHBORS — will only go away if we let it wash up on shore and then manually remove it from the beach:

Only if ALL PROPERTIES in the HIZ follow the beach cleaning guidelines above can we reduce the amount of sargassum floating around in the bay.  But if we all DO COME TOGETHER over the next few weeks, beach cleaning will become a much easier job that can be handled in an hour or so by a single in-house maintenance person.