Sunscreens damage important protozoa in the sea. These are foraminifera – tiny, shell-bearing creatures that make a significant contribution to the global marine carbon and nitrogen cycle. Special active ingredients in sun creams marketed as “environmentally friendly” attack diatoms, which live in symbiosis with the foraminifera and are essential for their metabolism, Viennese researchers report in the journal “Scientific Reports”.
Foraminifera have been around for hundreds of millions of years. Because of their long-lived shells, they are important index fossils for past geological eras. Based on their housing, one can draw conclusions about the climate in the past.
The majority of foraminifera species live in the sea and feed on plant plankton (phytoplankton), i.e. algae. However, many foraminiferal species also use algae as a source of energy in other ways: Because the algae can carry out photosynthesis, the foraminifera live in symbiosis with them and are dependent on the ability of the algae to produce carbohydrates using sunlight.
“Due to the large amount of foraminifera in both deep and shallow waters and their uptake by phytoplankton, it can be assumed that they make a significant contribution to the global marine carbon and nitrogen cycle,” explains Petra Heinz from the Institute of Palaeontology at the University of Vienna in a broadcast. However, this function could be impaired by soiling with residues from sun creams, especially in coastal areas.
In their study, the researchers at the institute headed by Michael Lintner examined the large foraminifera species “Heterostegina depressa”, which lives in symbiosis with diatoms. They were able to show that the photosynthetic performance of diatoms is damaged by sunscreen.
For the study, the scientists selected four sunscreens, two of which are marketed as “environmentally friendly”. They also tested the effect of pure ensulizol, which is often used as a UV blocker in sunscreens.
They showed that ensulizol in particular had a strong negative impact on the diatoms. In addition, supposedly “environmentally friendly” sunscreens adversely affected the health of foraminifera more than conventional ones. “We assume that metal nanoparticles such as titanium dioxide or zinc oxide in ‘environmentally friendly’ sunscreens in particular cause this effect,” says Lintner. These substances had previously been classified as toxic to several microorganisms.