Two College of Engineering researchers are studying how aerosol emissions from sargassum seaweed affect the air we breathe by using air-monitoring sensors and analyzing seaweed, sediment, and water samples from a South Florida beach.
The sliver of sargassum seaweed 19-year-old Sofia Hoffman collected from the shoreline of Crandon Park Beach's Bear Cut Preserve looked more like a dying clump of grass than the fresh piece of marine algae it once was.
But the sample was exactly what she set out to find.
Hoffman, along with a group of other college students, planned to run a chemical analysis of the seaweed sample in a lab, searching for the presence of microbes that could play a role in fueling certain aerosol emissions.
It is all part of a University of Miami College of Engineering study that will examine how sargassum seaweed decomposing on beach shorelines affects South Florida's air quality.
"Surprisingly, we found that the literature on how rotting sargassum impacts the air we breathe is sparse. But it is an issue that needs more investigating because we know that as seaweed rots, it emits hydrogen sulfide, which can lead to respiratory problems," said Jiayu Li, assistant professor of mechanical engineering and the principal investigator of the study.
During the massive sargassum bloom of 2018, unprecedented masses of sargassum seaweed washed ashore at beaches in the Caribbean, Florida, and Mexico, emitting toxic fumes and wreaking havoc on coastal ecosystems and tourism as it decayed. Health care facilities in Martinique and Guadeloupe reported thousands of people showing up at clinics complaining of breathing problems.
Now, more massive patches of the brown-colored seaweed, known as the Great Atlantic Sargassum Belt, are headed this way, satellite images revealed earlier this year. Twice the width of the United States, the bloom set size records earlier this spring. And though scientists recently reported that the belt has decreased in size, the matts of seaweed are still a concern for beach managers and tourists.
As such, Li pointed out that her one-year study, which is funded by the National Science Foundation's (NSF) Rapid Response Research program, couldn't be timelier.
She and her team will deploy air-monitoring sensors about the size of small microwave ovens in predetermined areas at a South Florida beach, tracking sulfur emissions from the sargassum. They will also deploy canisters to collect aerosol samples that will be analyzed in a lab.
And as part of a third component of the study, they will collect sargassum, sediment, and water samples, analyzing the microbes that are present in them. "We believe that microbial communities may be controlling whatever's in the sargassum and resulting in possible emissions," said co-principal investigator Helena Solo-Gabriele, a professor in the Department of Chemical, Environmental, and Materials Engineering, whose research includes studying microbial contaminants in the water-sand interface.
Deployment of the sensors and the collection of samples will begin in earnest in late June or early July, the peak of the sargassum season.
Li, Solo-Gabriele, and seven students from the University's College of Engineering and other institutions recently visited Crandon Park to scout the beach as a potential site to deploy their sensors and take water and sediment samples. Miami-Dade Parks and Recreation is cooperating in the study.
During the one-hour visit to Crandon, Hoffman, a sophomore at Penn State University who is participating in the College of Engineering's Coastal Infrastructure Resilience Research summer program, and other students collected seaweed, sediment, and water samples they will use to practice how to test for the presence of microbes.
"I feel lucky to be a part of this because it's something that will have an impact on people living near coastlines, whether it's in the Caribbean or Florida," said Shahar Tsameret, a doctoral student in mechanical engineering who is studying under Li. "What's interesting about this project is that I'm studying mechanical engineering, but we're working with the new Center for Aerosol Science and Technology. Aerosols are a big part of public health. We all breathe air."
The study is not the first time Solo-Gabriele has conducted research on sargassum seaweed. In a previous project, she and her graduate assistant, Afeefa Abdool-Ghany, demonstrated that sargassum can be used to make an effective compost—a mixture of organic matter used as plant fertilizer.
The current NSF project in which Solo-Gabriele is partnering with Li is critical because "sargassum will continue to affect our coastlines as long as climate change worsens," she said.
"The knowledge gained over the course of this project is likely to increase our understanding of these types of events and better prepare us to respond to future events," Benjamin Brown-Steiner, director of the Atmospheric Chemistry Program at the NSF's Division of Atmospheric and Geospace Sciences, said of the study.
