Abstract
Foraminifera are abundant unicellular organisms that play an important role in marine element cycles. A large benthic foraminifer obligatory bearing photosymbionts is Heterostegina depressa. We studied potential impacts of sunscreens available on the market on the activity of photosymbionts on H. depressa by means of pulse-amplitude modulated (PAM) fluorescence microscopy. We included four different sunscreens, with two of them sold as “conventional” and two more stated as “eco-friendly”. Further, the impact of pure Ensulizole (phenylbenzimidazole sulfonic acid) was tested, which is a common agent of sunscreens. Foraminifera were incubated at varying concentrations (10, 50 and 200 mgL−1) of different sunscreens and the pure Ensulizole for 14 days. The photosynthetic performance was measured after 1,3, 7 and 14 days. Pure Ensulizole had a strong negative impact on the photobionts, which was reflected by a significant reduction of the areal fluorescence signal. “Eco-friendly” sunscreens affected the health of foraminifera more severely compared to “conventional” ones. We assume that metal nanoparticles like titanium dioxide or zinc oxide of “eco-friendly” sunscreens are causing this impact, because these substances were already classified as toxic for several microorganisms.
Highlights
It turned out that sea surface temperature and salinity are key environmental factors that regulate the distribution of large benthic foraminifera, which might lead to a shift in distribution patterns due to climate change[10], Occhipinti-Amborgi[11]
We found that sunscreens reduce the metabolism of foraminifera, based on the decreasing amount of photosynthetic active symbionts, which are obligatory for large benthic foraminifera
We conclude that certain substances like Ensulizole and heavy metal nanoparticles lead to a substantial decrease of the photoactive area in Heterostegina depressa
Summary
Foraminifera are unicellular shelled microorganisms and abundant in the benthic and pelagic zone of o ceans[1,2]. Some families of LBFs (Amphisteginidae and Nummulitidae) can even be found in 130 m water depth with lower than 1% of the surface photosynthetically active r adiation[14] All these aspects highlight the importance of investigations on LBFs and will help to understand the relation between reef systems and global change. The estimated worldwide production of UV filters amounts up to 10 000 metric tons per year and has the potential of getting disposed in natural e nvironments[17] Some agents such as the common organic sunscreen Ensulizole (phenyl benzimidazole sulfonic acid) are resistant against microbial decomposition p rocesses[18]. Studies have shown that Ensulizole can have negative effects on organisms, for example by damaging DNA through the generation of reactive oxygen s pecies[20] As these substances are toxic for organisms including the photosymbionts of foraminifera, their application may lead to reduced vitality of the foraminiferal host and outcompeting by other taxa. We considered different sunscreens (both non-organic, conventional ones and eco-friendly sunscreens) and pure Ensulizole
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