__________________________________________________________________________________________________
Story by Emma Bryce | 8/2/24 | Anthropocene Magazine
In our attempts to eat and drink more healthily, we may be doing unintentional harm to ecosystems. Researchers have evidence that the widespread artificial sweetener, sucralose, may be disturbing the growth of aquatic microorganisms that form the foundation of aquatic food webs.
The new study, published in the journal Environmental Monitoring and Assessment, builds on research showing that sucralose can’t be broken down by the human body, and can therefore enter wastewater systems and flow into the environment.
In fact, sucralose is so robust and difficult to degrade, that it has been used as a marker to track the pathway of anthropogenic waste into the environment.
Based on these facts, the researchers on the new study wanted to explore what the compound does once it gets into nature. In their native Florida, they collected multiple soil samples from freshwater and estuarine (brackish water) ecosystems, and took these back to the lab. Mainly, they were interested in the behavior of two groups of microorganisms in these soil samples: diatoms, a type of algae, and photosynthesizing microbes called cyanobacteria. Both are food for dozens of species, and so support an abundance of life.
The researchers then applied sucralose to their soil samples in varying quantities, and ran two separate sets of experiments on the treated soils. The first experiment examined how organisms reacted to the sucralose over a five day period; the second looked at their reaction over a 24-hour period to get a finer-grained perspective at their initial response to varying amounts of sucralose.
Using devices to detect fluorescence and carbon dioxide—both of which can track changing population density of algae and bacteria—the researchers made their first striking discovery.
When exposed to both high and low levels of sucralose, diatoms in the freshwater soil samples initially started to increase, before suddenly tanking by more than 50% after 12 hours. Their steep decline was notable compared to the control, where diatoms in soil samples untreated with sucralose continued to flourish over the five days. In the brackish soil samples, diatoms showed a slightly different, but overall also declining trend, compared to the controls.
Cyanobacteria had a more varied response. In the freshwater soil samples they seemed to prosper with sucralose, at times growing more abundantly even than the cyanobacteria in the control. But in brackish soils, cyanobacteria populations crashed under sucralose treatment.
The researchers can’t explain why some populations seemed to thrive then crash, and others managed to go on. But they do have some theories. “This most likely just comes down to the different microbial communities and how they choose to utilize or react to the sucralose,” says Amelia Westmoreland, a chemistry researcher based at the University of Florida at the time the study was done, and the paper’s lead author.
It’s possible that diatoms misidentify sucralose as a nutrient and rush to gorge themselves, before their systems inevitably fail to break it down and actually feed off of it—which could explain their population surge and then steep decline.
Meanwhile, a quirk of freshwater cyanobacteria biology is that they’re able to use sugars as a kind of protective armor to shield them against desiccation, and so sucralose might have helped them survive in the freshwater soils, explaining their higher populations there. But in the brackish soils, cyanobacteria seem to lack this advantage, which might be why they declined in those samples.
Whatever the cause, the study shows signs of imbalance linked to the artificial sweetener. When you consider that diatoms—the more sensitive of the two—fuels over 30% of the primary production in the marine food web, that could be a worry.
Does it mean we should hold the sweetener, for nature’s sake? Westmoreland thinks this would be premature, and emphasizes that her study was a pilot project designed to prompt more research. “As this was a high concentration applied in a controlled environment, there is no true measure of when this concentration may be evident in the ecosystem from waste,” she explains.
Still, it’s something to keep an eye on, she suggests. “We do know that sucralose does make it into the environment through wastewater. Over time, this can lead to higher concentrations of sucralose which may affect some ecosystems in the future.”
Westmoreland et. al. “Sucralose (C12H19Cl3O8) impact on microbial activity in estuarine and freshwater marsh soils.” Environmental Monitoring and Assessment. 2024.