Nanobeads to save coral reefs

C&I Issue 7, 2017

Coral reefs are the world’s most diverse ecosystems, yet they could be in danger of disappearing altogether in the next few decades. Rising temperatures are a big part of the problem, but so too it seems is a common ingredient of sunblock. Recent research is finding evidence of the damaging coral bleaching effects of oxybenzone even at levels as low as ppb, according to researchers at the ACS meeting in Washington in August 2017.

But now the team at the University of Puerto Rico, Mayaguez, has come up with a possible solution - to soak up the oxybenzone from contaminated seawater with biodegradable beads. In tests on seawater samples spiked with oxybenzone at 30ppm, the beads removed 95% of the compound within an hour, said lead researcher Felix Roman.

The problem with oxybenzone, Roman reported, is that it damages coral DNA. Around 40% of sunblock typically washes off at the beach, he continued; when one undergraduate student in the group stepped into the ocean after covering herself in oxybenzone sunblock, the water was found to contain an oxybenzone concentration of 1.3ppm within 10 mins. And the compound is also present in some shampoos and dishwashing detergents and other products.

To address the problem, Roman’s group has developed biodegradable beads made of an outer matrix of chitosan and algae, derived from fish and algae, and coated with sodium oleate that attracts oxybenzoate. An inner core of iron oxide nanoparticles allows the beads to be pulled from the sea with a low power magnet, Roman explained.

In future, he envisages that the beads could be chemically tailored to remove a range of contaminants from seawater. Bags of these magnetic nanobiocomposite beads could then be dragged along at the back of a boat to help remove target contaminants, especially in areas near vulnerable coral reefs.

The consequences of inaction to save the coral reefs could be disastrous, Roman warned. ‘Sixty per cent of the world’s coral reefs will be lost in the next 30 years. We could lose the entire ecosystem in the Great Barrier reef of Australia. Entire ecosystems capable of supporting thousands of species of organisms will be lost.’

While the use of oxybenzone is controlled in the EU, he said this is not yet the case in the US. Alternative physical sunscreens based on titanium and zinc generate reactive oxygen species that may be even more damaging to coral than oxybenzone.

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