Study shows debris cleanups through the years have reduced marine life entanglements

Large-scale marine debris cleanups through the years have made a difference in saving Hawaiian monk seals.

A new study published in the Science journal shows a decline in entanglement rates among the endangered species at many sites in the Northwestern Hawaiian Islands during the past 25 years.

“Now we know that all the hard work and dedication of so many people and organizations that contributed to the Northwestern Hawaiian Islands marine debris cleanup did achieve its aim of reducing monk seal entanglement, saving seal lives and improving nearshore habitats,” said Jason Baker, marine biologist with the National Oceanic and Atmospheric Administration Fisheries Pacific Islands Fisheries Science Center Protected Species Division and the study’s lead author.

Scientists from the Pacific Islands Fisheries Science Center, the Papahānaumokuākea Marine Debris Project and the University of Hawai‘i Sea Grant College Program, or the Hawai‘i Sea Grant, have studied the devastating impacts of plastic pollution on marine mammals, sea turtles, fish and coral reefs for more than 40 years.

Nearly 90 Hawaiian monk seals were entangled in ghost nets between 2006 and 2014 in Papahānaumokuākea Marine National Monument.

“Thirty-two percent of the estimated 1,400 remaining Hawaiian monk seals are alive today due to marine debris disentanglement and other human intervention,” states the nonprofit Papahānaumokuākea Marine Debris Project’s website.

Mary J. Donohue, affiliate faculty with Hawai‘i Sea Grant and study co-author, has spent her career researching the devastating impacts of plastic pollution on marine mammals and coral reefs.

She served as chief scientist on the first systematic at-sea expeditions in Hawai‘i to document, study and remove marine debris from the Northwestern Hawaiian Islands.

“We’ve shown that you can, in fact, clean up at least parts of the ocean, and it can be consequential, particularly for species of conservation or cultural concern,” said Donohue. “For lasting solutions, we also need to reduce the input of fishing gear that becomes derelict, both from legal and illegal fisheries.”

The Papahānaumokuākea Marine Debris Project website states that 115,000 pounds of derelict fishing gear, or ghost nets, wash in from the open ocean annually, causing large-scale impact to coral reefs.

Masses of net and rope routinely break apart living corals and rip coral heads from the bottom as they tumble across the reef.

Researchers say plastic waste poses a triple threat to living organisms and the environment: the physical material itself, the chemicals associated with it and disease-causing microorganisms that hitchhike on it.

The longevity of plastic waste and its fragmentation results in impacts on multiple scales, from marine mammal entanglement in derelict fishing gear to tissue and cellular interactions with the tiniest nanoplastics.