To document the increasing amount of plastic debris littering oceans and beaches, a team from Duke University Marine Laboratory in Beaufort, N.C., is taking part in a project that incorporates drones for collecting aerial images.
“We’ll be analyzing images sent back by the expedition to calculate the density of plastic debris washing up on beaches, identify what type of plastics it is and, hopefully, help trace it back to its sources,” says David W. Johnston, assistant professor of the practice of marine conservation ecology.
The first batch of images, collected by drones flying over remote beaches in and around the Azores archipelago in the North Atlantic, should be transmitted from the expedition’s ship back to Johnston and his students in Beaufort later this month.
The privately funded expedition, known as the Race for Water Odyssey, will leave Bordeaux, France, this week to begin its yearlong voyage to explore the five largest vortices of trash in the world’s oceans.
Discarded plastic, which slowly disintegrates into tiny flakes in the salt water, can travel for years along marine currents before accumulating in whirlpools of diffuse pollution known as vortices, or ocean gyres.
Documenting the extent and geographic location of the debris has been a challenge for scientists, Johnston explains, because of the remoteness of the gyres – which are located in the deep ocean, far from land – and because when the plastic breaks down, it becomes difficult to spot from traditional aerial images.
To help solve this problem, Johnston has helped develop an experimental drone-enabled imaging process the expedition will employ to document debris on remote beaches. The imaging technology, which will be mounted on a remote-controlled fixed-wing drone, uses a high-resolution, red-edge camera with a spectral response that “just makes plastic debris pop,” he says. “We should be able to use it to identify any plastic that’s two-and-a-half centimeters or larger.”
The expedition will also collect images using a regular high-resolution camera. Johnston and his masters and undergraduate students at the Marine Lab will compare these images to the red-edge spectral images to help identify what kinds of plastics are washing up on the beaches and try to identify their sources.
“It takes about three to four hours to process the data from each flight of the drone, and then another three to four days to analyze the images,” Johnston says. “The wavelengths of light reflected by plastics and captured by the red-edge camera images are so distinct that we can identify and analyze them by eye in the lab.”