DURHAM, N.C. – Faculty and students at the Duke University Marine Laboratory in Beaufort, N.C., will play a key role in a round-the-world expedition beginning this week to document the increasing amount of plastic debris littering the world’s oceans and beaches.
“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 year-long voyage to explore the five largest vortices of trash in the world’s oceans.
About eight million tons of plastic debris is dumped into the oceans each year. The discarded plastic, which slowly disintegrates into tiny flakes in the salt water, can travel for years along marine currents before accumulating in large, slowly-turning whirlpools of diffuse pollution known as vortices, or ocean gyres. Scientists have identified five such areas around the world, in the North and South Atlantic, the North and South Pacific, and the Indian oceans.
“This debris kills about one million sea birds a year, many of whom mistake it for small prey and choke to death while trying to ingest it,” says Johnson. “It also poses entanglement threats, promotes the spread of invasive species and toxins, and contributes to pollution in fisheries that are a key source of food for more than 3.5 million people living on islands within the gyres.”
Documenting the extent and geographic location of the debris has been a challenge for scientists, he explains, because of the remoteness of the gyres – all five of which are located in the deep ocean, far from land – and because when the plastic breaks down, it becomes incredibly 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.”
In addition to the Azores, the expedition will collect images of debris in and around Bermuda – which, like the Azores, lies within the North Atlantic debris vortex – and from Easter Island in the South Pacific, and Palmyra Atoll, Midway Atoll, Wake Atoll, the Mariana Islands and the island of Koror in the North Pacific.
After that, it will head to Chagos and Rodrigues islands in the Indian Ocean and the island of Tristan Da Cunha in the South Atlantic, before returning back to its home port of Bordeaux in March 2016.
The ship is scheduled to dock in New York City on April 8, where Johnston will join its crew for a presentation at the United Nations Environment Programme (UNEP).
Ari Friedlaender, associate professor of marine ecology at Oregon State University, is working with Johnston to analyze the images. Friedlaender is a 2006 PhD graduate of Duke’s Nicholas School of the Environment and a former faculty member at the Duke Marine Lab, which is part of the Nicholas School.
Johnston, Friedlaender and their students will contribute to the final report issued after the conclusion of the expedition. They also anticipate publishing independent peer-reviewed studies based on their findings.
You can learn more about it at the Race for Water Odyssey website.