Sunscreen makes plants scream

By Ibrahim Ali
Elementary Category (Grades 4-6)
Experiment | Environment

Every year millions of people go into the ocean with sunscreen on. Have you ever wondered what affects these sunscreens have on underwater plants? There are 2 kinds of sunscreens, mineral-based and chemical-based. The chemical-based sunscreens absorb into the skin and protect against UV rays by dissolving the UV rays. They have chemicals that include Oxybenzone, Octinoxate, Avobenzone, Octisalate, etc. Out of these chemicals, Oxybenzone and Octinoxate are mainly used. They have harmful effects on coral reefs, algae, sea urchins and fishes. They cause coral bleaching by damaging the coral’s symbiotic algae (Zooxanthellae) that lead to low food quantity for the coral and the coral loses its colour.

Also, chemical-based sunscreens accumulate in tissues of fishes leading to diminished growth and gender shift. They also inhibit the growth of sea urchin embryos, damage immune and reproductive systems and cause deformed sea urchin offsprings. Also, chemical-based sunscreens accumulate in tissues of fishes leading to diminished growth and gender shift. These sunscreens diminish growth and photosynthesis in underwater plants like seagrass, algae etc. Research showed that these problems happened even at a very low concentration as low as 62 parts per trillion. The mineral-based sunscreens don’t absorb into the skin and reflect and scatter UV rays. Mineral-based sunscreens have minerals as main ingredients like zinc oxide and titanium dioxide. The mineral-based sunscreen is also known as a physical sunscreen because they only provide a barrier between sun and skin.

The standard Zinc Oxide and Titanium dioxide sunscreens leave a white opaque layer on the skin making them less liked. To avoid this, now they are coming in the form of Nanoparticles, this means that the zinc oxide and titanium dioxide are being broken down into microscopic pieces before they are added to sunscreen. These nano zinc oxide and nano titanium dioxide are not safe for marine life. They can affect the growth of coral reefs, algae, fish and sea urchins by interfering with their ability to get rid of toxic substances from their bodies. On the other hand, non-nano zinc oxide and titanium dioxide are considered to be safe for marine life. For my experiment, I exposed underwater plants to different mineral and chemical-based sunscreens for two weeks. The chemical-based sunscreens that contain Oxybenzone and Octinoxate had the most damaging effect on the underwater plants. the sunscreen containing Zinc Oxide and Titanium dioxide have the least damaging effect on the underwater plants.

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