Sunscreen chemicals may harm corals, but they're the tiniest player among reef threats

The dangers of certain sunscreens to coral reefs are believed by some Hawai`i legislators to be so dangerous that they are considering banning it.

Can they really be that bad? If they were, wouldn’t reefs where nobody swims be far healthier than those frequented by oil-slathered masses?

In our review of the science, it’s true that some of the chemicals in some sunscreens are harmful to reef organisms.

But as usual, this issue is complicated. 

While there has been much breathless prose arguing the hazards of sunscreens on reefs, there is also another side to this story. The other side is, essentially, that it is an issue, but a very minor one compared to the other challenges.

Also, even though folks worried about certain sunscreen products recommend using other products, some of those others may be dangerous to reefs too. And still more may use compounds that have not yet been thoroughly tested.

A 2008 research effort by Italian scientist Robert Danovaro argues that sunscreens can promote viral infections in tiny algae called zooxanthellae, and that can cause coral bleaching. Danovaro’s team looked at various components of sunscreens and found that in the laboratory, these had the strongest impact on coral bleaching: butylparaben, ethylhexylmethoxycinnamate, benzophenone-3 and 4-methylbenzylidene camphor.

Another of the key studies on the subject was published last year in the Archives of Environmental Contamination and Toxicology. The lead author was Craig Downs. It found that if certain corals were exposed to the active ingredient in many sunscreens, oxybenzone or benzophenone-3, they could harm corals and cause coral bleaching.

Oxybenzone is one of the chemicals in many sunscreens that shields your skin against ultraviolet radiation from the sun. And that reduces skin cancer risk.

Researchers found that if you expose coral cells to enough oxybenzone, it will kill them. At lower levels it will deform them, and will cause reef corals to expel their food-giving algae. When the algae are gone, the corals go white, a process called bleaching. Eventually the coral polyps can starve and die.

The study found that there can be impacts on coral larvae and cells at oxybenzone concentrations in the higher ranges found on Hawai`i beaches—notably heavily populated O`ahu beaches.

Thus, the authors wrote, “Oxybenzone poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.”

But there’s more to it than that. 

We’re still waiting for studies that link the health of reefs where there is a lot of sunscreen-drenched swimming compared to similar reefs that are pristine.

Coral reefs are being hit by all kinds of attacks, and coral reefs are bleaching in the Main Hawaiian Islands as well as in the Northwestern Hawaiian Islands, many of which are uninhabited and sunscreen-free.

Hawai`i is taking coral reef degradation seriously. Earlier this year, the Department of Land and Natural Resources released its Coral Bleaching Recovery Plan. It focuses on a number of reef threats, primarily warming waters.

It does not consider sunscreen issues.

That doesn’t mean sunscreen is invisible to the state. The state Division of Aquatic Resources has issued a statement of concern that “Researchers have found oxybenzone concentrations in some Hawaiian waters at more than 30 times the level considered safe for corals.”

Rather than slathering on sunscreens with oxybenzone (read the label), the state recommends other alternatives to prevent sunburn: “water resistant sunscreens, which are more likely to stay on your skin, and sunscreens that use mineral filters, such as zinc oxide or titanium dioxide. Also, rash guards or wet suits will reduce the area of exposed skin, and thus the amount of sunscreen needed for protection.”

But switching to any other sunscreen may not be the best answer. It depends on which one. Zinc oxide and titanium dioxide are also potential reef problems. This study suggests that titanium dioxide, as it breaks up in the marine environment, can be toxic to marine algae. Zinc oxide is believed to have similar impacts.

If you care about reefs, limiting your participation in adding harsh chemicals to the surf is important. But you should also be paying attention to some of the more serious threats to reefs—including climate change, sedimentation from the land and overfishing. 

This 2012 study looked at all the known causes of a 27-year decline in coral cover on the massive Australian Great Barrier Reef. None of them was sunscreen. 

The big culprits, after tropical cyclones, crown-of-thorns starfish and climate-related bleaching: “their high sensitivity to rising seawater temperatures, ocean acidification, water pollution from terrestrial runoff and dredging, destructive fishing, overfishing, and coastal development.”

 

© Jan TenBruggencate 2017

Keep your brain young--get up close and personal with kale, collard greens and cabbage

Here’s the latest bright shiny new study that tells you what your mother told you years ago.

Eat your vegetables.

The new study, published Dec. 20, 2017, in the journal Neurology, says that if you eat vegetables, your brain age is younger.

And if you eat a lot of veggies, it’s a lot younger.

“In a linear mixed model adjusted for age, sex, education, participation in cognitive activities, physical activities, smoking, and seafood and alcohol consumption, consumption of green leafy vegetables was associated with slower cognitive decline.

"The decline rate for those in the highest quintile of intake was … the equivalent of being 11 years younger in age,” said the authors, Martha Clare Morris, Yamin Wang, Lisa L. Barnes, David A. Bennett, Bess Dawson-Hughes and Sarah L. Booth. 

The article is entitled “Nutrients and bioactives in green leafy vegetables and cognitive decline: Prospective study.” Here’s a link to it. 

It seems like a well-done study, and it’s getting a lot of media attention. The authors studied nearly 1000 individuals aged 58 to 99, surveyed them about their eating habits, and did multiple health assessments over nearly a five-year period.

Are there particular vegetables that work best? The science team found that it’s those that contain vitamin K (phylloquinone), lutein, β-carotene, nitrate, folate, kaempferol, and α-tocopherol. 

That may be a meaningless list to most folks, but think leafy greens like kale, spinach, collard greens and even lettuce.

One caveat is that this study only looked at the things people were already eating. There are other studies that suggest benefits of other foods that are not commonly eaten. 

Wild foods in many cases may contain micronutrients that might not be available elsewhere, says this different study. 

That could be an argument for protecting wild endangered plants—they might have significant health benefits that domestic plants could lack. The study cites wild asparagus (Asparagus acutifolius), wild fennel (Foeniculum vulgare), a weed called maiden’s tears (Silene vulgaris).

Nettles are listed as important sources of vitamins, and of course in Hawai`i, folks have long made a tea out of the leaves of a pricker-less Hawaiian nettle, mamaki (Pipturus albidus).

A study in the Asian Journal of Agriculture and Rural Development cites some of the health benefits of a lot of veggies, including the crucifers like cabbage and broccoli, the aliums like onions and garlic, the chenopods like spinach and chard, and the solanaceous plants like tomatoes and peppers.

The upshot, as your mother always told you, eat them vegetables.

© Jan TenBruggencate 2017

Cool Hawaiian science: blend up some healthy leaves, spray on sickly plants, and create healthy plants

We are not alone, and we can’t be.

Whether human or plant or other species, we all live by John Donne’s rule: “No man is an Island, entire of itself; every man is a piece of the Continent, a part of the main.”

(Image:  The native mint P. kaalaensis in flower, with fungal

infection (white spots on leaves). Credit: Geoff Zahn.)

University of Hawai`i researchers, in an elegant new piece of work, show that even plants in the garden depend on a community of other organisms to protect them. Some of these natural allies live in the soil and root, in the stems and leaves, and even on the stems and leaves.

In this case, working with a native mint called Phyllostegia kaalaensis, professor Anthony Amend and researcher Geoff Zahn found that they could transplant disease resistance into a plant that otherwise was a severe risk of fungal attack.

The mint, which was once thriving in the wild, has been extinct in the wild since 2015. The ones still living in nurseries were extremely weak--perhaps because they were sprayed regularly with fungicides to prevent fungus attack. The fungicide kept them alive but also kept them weak, said Zahn.

As long as the plants remained so vulnerable, there was little hope of restoring them to the wild, where they would immediately be killed off.

Healthy native mint in the wild. Credit: Vincent Costello.

All it took was to blend up (actually blend, in a blender) the leaves of a related wild plant, which presumably contained whatever protective organisms lived with the wild plant. The donor plant was a related endangered Hawaiian mint from Molokai, Phyllostegia hirsuta. 

They sprayed the blended stuff onto nursery plants. And the plants that had been given this “transplant” of beneficial organisms were suddenly able to fight off fungal attack. The beneficial organisms are called endophytes, which are forms of life like fungi and bacteria that live inside the plant. 

Here’s now the University of Hawai`i press release put it:

“They took leaves from a closely related wild that plant was healthy and contained a typical mix of endophytes, blended them into a smoothie and sprayed the mixture onto the leaves of (the native mint)  to see if beneficial microbes could be transplanted from one species to another. They then subjected these plants, along with a control group, to the deadly powdery mildew. The plants that received the microbial spray were able to resist disease, those that didn’t receive the spray soon died.”

The research is simply remarkable. Nursery plants, generally planted in sterile media, are “alone.” They don’t have their natural biological communities around them. And as a result they are severely vulnerable. 

In this case, Amend and Zahn weren’t sure which of the constituents of the blended spray did the anti-fungal work, so they tested for it.

“Using DNA barcode sequencing to identifying which species were inside leaves before, during, and after the disease, Amend and Zahn determined the beneficial fungus that was most likely responsible for protection from disease: the yeast Pseudozyma aphidis. Those treated plants did so well, that they have since been planted out in the wild, and now represent the only wild population of P. kaalaensis on the planet.”

Zahn said this yeast can live both on the leaf surface and inside the plant's tissues. When they prepared the leaves for blending, they cleaned the exterior, so the protective fungus came from inside the tissues of the hirsuta. 

The National Science Foundation and the Army funded the research. Anend and Zahn were associated with the University of Hawai‘i at Mānoa botany department and the O'ahu Army Natural Resources Program. Zahn has since moved on to Utah Valley University.

Amend continues the work in Hawai`i, and also works with University of Hawai`i researcher Nicole Hynson, who is studying, among other things, beneficial organisms in the roots of plants.

This remarkable research builds on a growing understanding of the relationship between diverse life forms. 

Some years ago, researchers were able to save an exceedingly rare native orchid on Molokai.

The orchid did poorly in captivity, and did poorly when planted out in the wild. But when it was planted in soil that had been inoculated with soil from places where it had once grown, it did fine.

Growing with the soil organisms on which it depended, it survived. Alone, it did not.

We’re not even going to go here into the relationships between humans and their gut organisms. But whether you go by “no man an island” or “it takes a village,” the message is clear.

 © Jan TenBruggencate 2017