Healthy coral reefs and all waterways are the most valuable ecosystems on Earth. They provide billions of dollars in economic and environmental services, such as food and tourism.

However, these aquatic ecosystems around the world face serious threats from a number of sources, irresponsible fish harvesting practice, land-based pollution, coastal development, disease, and invasive species.

Scientists have also discovered that some of the chemicals found in sunscreen and other personal health products threaten the health of natural resources. How these, and other compounds, affect each ecosystems remains an active area of research. Researchers are reviewing the environmental impacts of sunscreen ingredients as part of a National Academy of Sciences study expected to be completed in 2021.

So far the results show that long-term exposure to ultraviolet (UV) filters -- including avobenzone, oxybenzone, and octocrylene -- is lethal for some organisms living in freshwater & saltwater environments. One of the largest sources of UV-filter contamination in both marine and freshwater environments is from sunscreen leaching off of the skin while swimming.

"We do know that UV-filters are particularly devastating to coral reefs and cause bleaching, but there has been almost no research on what the effects are to freshwater animals," explained Aaron Boyd, graduate student in the Department of Biological Sciences and lead author on the paper. "To address this, we examined the effects of UV-filters in the water flea, Daphnia magna."

The results show that exposure to UV-filters over a 48-hour period prevented the fleas from navigating through their environment. Exposure over a 14-day period -- similar to what might occur near popular beach areas -- proved lethal for the tiny crustaceans.

"This is particularly bad for a freshwater ecosystem as a whole, as Daphnia are an important part of the food chain for many smaller species of fish," added Boyd, who completed this research in collaboration with graduate student Connor Stewart, under the supervision of Assistant Professor Tamzin Blewett and Professor Keith Tierney.

"Losing a Daphnia population would put all of the species that rely on them at risk of starvation, and in certain conditions could cause the local ecosystem to collapse."

The good news, Boyd explained, is that the fleas were able to recover their ability to navigate through the water once the contamination was removed -- a good sign for environmental recovery.

"These chemicals are short-lived in the environment, so if we remove the sources of pollution, then there is a reasonable chance for the organisms in those environments to recover."

How sunscreen chemicals enter our environment: 

The sunscreen you apply may not stay on your skin. When we swim or shower, sunscreen may wash off and enter our waterways.

How sunscreen chemicals can affect marine life:

Green Algae: Can impair growth and photosynthesis.

Coral: Accumulates in tissues. Can induce bleaching, damage DNA, deform young, and even kill.

Mussels: Can induce defects in young.

Sea Urchins: Can damage immune and reproductive systems, and deform young.

Fish: Can decrease fertility and reproduction, and cause female characteristics in male fish.

Dolphins: Can accumulate in tissue and be transferred to young.

Chemicals in some sunscreens that can harm marine life include: Oxybenzone, Benzophenone-1, Benzophenone-8, OD-PABA, 4-Methylbenzylidene camphor, 3-Benzylidene camphor, nano-Titanium dioxide, nano-Zinc oxide, Octinoxate, Octocrylene