Written by: Carlyn Scott, Science Communications Assistant
Floating macroalgae called Sargassum has been in the news recently, and not for good reason. Forming massive floating blooms that can stretch across the Atlantic Ocean, such as the 5,000-mile and 13-million-ton behemoth seen in April 2023, Sargassum can wash ashore in the Caribbean and Florida. Once on shore, the decomposing macroalgae can emit a mixture of dangerous gases, including hydrogen sulfide, that adversely affects the environment and human health.
A five-year, $3.2-million grant from the NOAA Monitoring and Event Response for Harmful Algal Blooms program aims to better forecast Sargassum blooms and prevent them from plaguing coastal communities. The USF College of Marine Science (CMS) will receive about half of the total funding amount with the remainder awarded to collaborators at Florida Atlantic University, the Caribbean Coastal Ocean Observing System (CariCOOS), NOAA Atlantic Oceanographic and Meteorological Laboratory, and the U.S. Virgin Islands Department of Planning and Natural Resources.
Brian Barnes who will lead the grant, has been a researcher in the Optical Oceanography Lab of Chaunmin Hu at CMS since 2013.
“Up until this point, we have been using very coarse resolution satellite data to observe Sargassum,” said Brian Barnes, assistant research professor and physical oceanographer at CMS and the project's principal investigator. “This grant will help us look at Sargassum at a finer spatial scale, and this capability will eventually allow the scientific community to provide real-time monitoring and forecasting.”
Barnes, who has studied Sargassum at the College of Marine Science’s Optical Oceanography Lab since 2015, will use satellite, hydrographic, and water-quality data to illuminate the effects of Sargassum on coastal waters and beaches in order to develop better forecasting solutions. The goal is to increase the scale at which researchers can monitor Sargassum blooms.
Scale matters with Sargassum. While large accumulations of Sargassum in offshore waters can easily be observed via satellite, the new monitoring system will allow researchers to observe smaller, but distinct patches, of Sargassum.
“The goal is to be able to put a single beach on alert when a Sargassum inundation is imminent, instead of alerting the entire Caribbean,” said Barnes.
This increased level of resolution will give coastal resource managers more time to prepare for and ameliorate the effects of inundation events. The team will also work directly with managers and other impacted groups to ensure that the new Sargassum monitoring systems are accurate and advantageous.
Yonggang Liu, associate research professor and director of the Ocean Circulation Lab at CMS, will partner with CariCOOS to couple the higher-resolution satellite images with coastal ocean circulation models. With the new models, researchers will be better able to forecast where Sargassum is most likely to come ashore.
“Starting with locations where Sargassum patches are identified in the satellite images, the models will allow for forecasts that predict where the algae will be in as little as three days,” Liu said.
A true color image from the Sentinel-2 satellite depicting Sargassum (green patches) near Caye Caulker, Belize in March 2023. The biggest patch measured about 10 acres. Photo credit: Chuanmin Hu.
Tracking Sargassum’s exact location is crucial. While offshore Sargassum is generally benign — and even beneficial for some wildlife – the macroalgae becomes a problem when it reaches coastlines. When Sargassum gets closer to shore include promoting hypoxia, a depletion of oxygen that can lead to fish kills, as well as releasing gases harmful to humans. The grant aims to understand Sargassum's biochemical influence on the water and coastal ecosystems.
“The College of Marine Science has tremendous expertise in the remote sensing arena and resident researchers are leading the way toward improved detection and monitoring of Sargassum blooms,” said Tom Frazer, professor and dean of CMS. “A more precise Sargassum forecasting system will provide communities in Florida and the Caribbean advanced warning that their beaches may be impacted, and allow them to better prepare for an inundation event. This award demonstrates our faculty’s strength in coordinating collaborative research that has the potential for real-world impact.”
Sargassum first became an issue in 2011 when researchers noticed a huge uptick in its abundance – now shown to be partially caused by nutrient enrichment, as detailed in a recent report co-authored by Chuanmin Hu, professor and director of the CMS Optical Oceanography Lab, who is also part of the Sargassum-forecasting project team.
The abundance of Sargassum has generally increased every year since, wreaking havoc on tourism industries and local economies when it washes ashore. By helping researchers better understand Sargassum’s impact on water quality, NOAA’s funding may lead to more effective management plans.
“We want to know what happens to those areas that are subject to huge influxes of Sargassum,” said Barnes. “This grant allows those areas most impacted by Sargassum, such as Puerto Rico and the United States Virgin Islands, to better prepare for potential inundation events and, with appropriate intervention, lessen devastating effects to their communities.”