Village’s plans on seaweed need rethinking as a result of UM bacteria study of the burying option
Key Biscayne beaches these days are relatively clear of sea grasses from offshore beds and the annual influx of Sargassum, but Village of Key Biscayne officials know it’s just a matter of time before the beachfront is covered again.
Seaweed management on Key Biscayne is a constant learning process, said Key Biscayne Resiliency Director Roland Samimy. It involves weighing the desires of beachgoers who want to enjoy a pristine beach, against the high cost of removing seaweed or using the cheaper option of burying (or “integrating”) the seaweed about six inches deep,
The long-used practice of integrating seaweed in the sand is now in question as a University of Miami study initially shows the practice increases beach bacteria levels, ultimately impacting water quality for swimming. It also adds to the percentage of organic material on the beach, which in excess can be a problem.
The results of a year-long study by Dr. Helena Solo-Gabriele, professor and Associate Dean for Research at the University of Miami, College of Engineering, “indicated that elevated bacteria levels on the beach tend to be associated with decomposing seaweed and that seaweed integration into the beach sands is not advisable at levels that are beyond what would naturally occur.”
Miami Beach does not integrate seaweed into its sand.
The village is working with Miami Waterkeeper (MWK) to monitor bacteria levels at two oceanside stations: adjacent to the Beach Park, and the public access point located between Oceana and the Silver Sands Motel. According to the village manager’s report to council Dec. 8, also being monitored are two bayside locations: Key Biscayne Yacht Club, and the confluence of Pines Canal and the second finger canal past Smugglers Cove.
Water samples for bacteria analysis are collected weekly and the results are available to the public via the Swim Guide App. If a given day's sample result exceeds the Florida Department Of Health bacteria threshold (70 cfu/100ml), that location is resampled on the following day. Sampling locations where bacteria analysis reveals poor water quality, even after one sample, are indicated by a red site marker on the Swim Guide App.
The problem with seaweed, according to Samimy, is that it is constant and can be a huge problem following storms or hurricanes. Even with limited use of integration, the seaweed management options are limited, with each option on the list becoming more costly, he said.
The options include: 1) no raking at times when seaweed accumulation is at a low level; 2) rake and haul when seaweed accumulation exceeds an acceptable level; 3) rake and haul all the time.
“Some integration is ok if it doesn’t generate too much bacteria,” Samimy said. “But with hauling you end up losing more sand and it is extremely costly,’’
Samimy has contacted beach-raking vendors who could be asked to bid on beach grooming services once the council settles on a seaweed management strategy.
The UM study suggested the council consider “alternative approaches” to seaweed management, but only in conjunction with sustained beach monitoring. Samimy said the additional monitoring would ensure an alternative is working; if not, the village could pivot to select an alternative method.
“With information about water quality from the same locations taken over time, we can better inform the public and take action on issues that may lead to environmental or public health dangers,’’ he said.
The recent results from the UM Study initially linking seaweed with bacteria should help prompt long-sought discussions and decisions by the Key Biscayne Village Council as to how to proceed, Samimy said.
“They haven’t really taken up the discussion. I am going to start reaching out to the council members to encourage them to start making a plan to have the discussion and make a decision as to what they want to start trying out next and when. I don’t think there’s any hesitation on the part of the council. It just hasn’t happened yet,’’ he said.