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Several years ago, a wave of illnesses struck the members of Joleah Lamb’s dive team. Lamb, a marine ecologist at the University of California at Irvine, was investigating coral disease in Indonesia with his colleagues when they came down with dysentery, a type of gastroenteritis. This common condition can be caused by ingesting water contaminated with pathogenic bacteria such as Enterococcus. Although symptoms are usually mild, gastroenteritis can be fatal. Every year, gastroenteritis and related diseases kill millions of people around the world, especially children under five.

Lamb and his colleagues’ experiment led to a scientific discovery: the concentrations of Enterococcus Pathogens that can cause gastroenteritis are lower in some parts of the ocean than in others. Notably, the pathogens responsible for gastroenteritis are less common among seagrasses.

In a recent study, a team led by Fortunato Ascioti, an ecologist at the University of Palermo in Italy, used Lamb’s insights to estimate the global potential of seagrass beds as a coastal remediation service. Ascioti’s effort, which was independent of Lamb’s work, found that if all the world’s seagrasses provided this pathogen reduction service, they could be responsible for a reduction of up to 24 million cases. of gastroenteritis per year. The savings from seagrass remediation on healthcare alone could be worth up to US$74 million worldwide.

Ascioti explains that the finding is a rough estimate of the remediation potential of certain sea grasses. There are more than 70 species of seagrass, he says, and only a handful are known to have this effect. Based on current knowledge of these seagrass species, Ascioti and his team calculated that around eight million cases of gastroenteritis are likely prevented each year.

Lamb, who was not part of the research team on the global estimates, says that when it comes to assessing seagrasses, these projections of the potential reduction in gastroenteritis per year are conservative. “I would say this is just an estimate of the value of the seagrass remediation service reducing pathogens for a single type of disease,” she says.

This is because different seagrasses target different pathogens. Lamb’s study identified three species of seagrass, Acoroid enhalus, Thalassia hemprichiiand Cymodocea rotundatawhich are effective against gastroenteritis Enterococcus bacteria. But previous research has shown that seagrass beds endemic to the Mediterranean Ocean Posidonia can reduce the concentration of Escherichia coliwhile temperate waters Zostera Marina aid reduce pathogens in vibrio gender.

Seagrasses can also help clean the water for other marine species, including those harvested as seafood.

Whether society can harness this health power by planting seagrass is a complex question, says Lamb, because scientists don’t know exactly how seagrass does this job.

“We don’t know, at least in tropical systems, if [seagrasses] play complementary roles with each other, or whether a single species can have this pathogen-reducing effect,” says Lamb. Seagrass density may also play an important role, she notes. Further research is needed to understand if this service is retained in replanted grasslands.

Yet, with growing human populations living in coastal areas, mitigating disease-causing pathogens will only become more important.