Plastic pollution is all over the place these days. Billions of tons of it are jammed into landfills or float around in the sea, gradually breaking down into smaller and smaller fragments but never truly disappearing. This represents one of the most serious environmental problems of our time, and one that is not going to go away unless we change our use of plastics or develop new materials that are biodegradable.

And that’s just what scientists at the University of California San Diego have being doing over much of the past decade. The interdisciplinary team, including biologist Stephen Mayfield and chemists Michael Burkart and Robert “Skip” Pomeroy, have developed polyurethane foams that are made from algae and other biological sources, and that are consequently biodegradable by natural decomposers (bacteria and fungi) in the environment. The experts have used these foams in the manufacture of shoes, including flip-flops, the world’s most popular form of footwear, and have already tested their decomposition in terrestrial environments. Once buried in the soils, the shoes began to degrade within just 16 weeks.

Now, in new research, the team has tested whether these polyurethane foams made from bio-based monomers will decompose when immersed in seawater. Working with study coauthor Samantha Clements, a marine biologist and scientific diver at Scripps Institution of Oceanography, the researchers fixed samples of their foams and shoes to the Ellen Browning Scripps Memorial Pier and monitored how they changed, physically and chemically, using Fourier-transform infrared spectroscopy and scanning electron microscopy.