By Kevin O’Brien
Members of the marine debris team of the PIFSC Coral Reef Ecosystem Division (CRED) returned to Honolulu on April 19 from a 21-day marine debris survey and removal effort at Midway Atoll. Since the last blog update on April 15, the 9-member team conducted an additional 6 days of operations, bringing the grand total for the entire mission to nearly 14 metric tons (13,795 kg) of derelict fishing gear and plastic debris removed from the reefs and shorelines of this remote atoll in the Papahānaumokuākea Marine National Monument and World Heritage Site.
In addition to the removal of debris, the team also conducted a pilot study of accumulation rates of marine debris in nearshore waters and along shorelines at Midway Atoll, continued to test protocols for assessment of benthic injuries related to marine debris, and surveyed for debris items potentially related to the Japan tsunami event of March 2011. Results from these secondary projects are not yet available at this early date.
What can be reported is the success of the main mission to survey and remove marine debris. In total, the team surveyed 43% of the shallow-reef areas of Midway Atoll that historically have been shown to contain high densities of marine debris. All derelict fishing gear found during in-water surveys was removed to mitigate entanglement of the Hawaiian monk seal (Monachus schauinslandi) and green sea turtle (Chelonia mydas), which are listed as endangered and threatened, respectively, under the Endangered Species Act.
Although the marine debris removed from shallow-water reefs was composed entirely of derelict fishing gear, the shorelines of Midway Atoll yielded a diverse range of debris types and items. Derelict fishing gear and plastics ≥10 cm in size were removed from the totality of the shoreline areas of Eastern Island and Spit Island and from portions of Sand Island. Debris was then transported by boat to the seaplane tarmac on Sand Island. Once there, shoreline debris was sorted and tallied by category. This tally of debris makes for an interesting look at the breakdown of the types of debris that accumulate at Midway. The table below shows the top 20 debris types, by quantity, that were removed from the shorelines of Midway Atoll during this mission.
In addition to the debris listed in the table at right, many random oddities were collected during shoreline work: toilet seats, golf clubs, plastic swords, umbrella handles, soccer balls, truck tires, a snowboard boot, a bowling ball, a fireman’s helmet, a 15-m plastic pipe, a traffic barrier, and, of course, the 23.5-ft fishing boat that was confirmed as lost in the 2011 Japan tsunami event, among other things.
“Just about anything you can imagine that humans use in their day-to-day lives, you can find it washed up on the beaches,” says Joao Garriques, a member of the CRED marine debris team, in reference to shoreline surveys at Midway Atoll. “You just can’t predict what you might find up there, 1200 miles from the nearest city.”
Management of all the small plastics during removal operations can be a challenge. This season, the team used large “bulk bags” that were 1.2 by 1.2 m and could be lifted easily by crane—the kind of bags used for transportation of gravel and sand—to facilitate the movement of small plastic debris between islands via inflatable boat. The bags worked well for management of the thousands of small debris items collected during shoreline surveys. The importance of the removal of these smaller plastic items is evident at Midway Atoll, because Laysan Albatross (Phoebastria immutabilis) and Black-footed Albatross (Phoebastria nigripes) chicks frequently can be seen chewing curiously on debris or becoming entangled in small net pieces.
“The amount of plastics in the environment up here is pretty alarming,” says James Morioka, a member of the CRED marine debris team, after witnessing the amount of debris present on the shoreline of Eastern Island after only 9 months of accumulation since the last marine debris mission at Midway Atoll ended in July 2012. “Just trying to keep up with it is kind of overwhelming.”
Now back in Honolulu, the marine debris team is demobilizing and processing data. The success of this mission was due in great part to the assistance of the partners of the PIFSC-CRED Marine Debris Project: U. S. Fish and Wildlife Service, Midway Atoll National Wildlife Refuge, NOAA Fisheries Pacific Islands Regional Office’s Damage Assessment Remediation and Restoration Program, NOAA Marine Debris Program, and Papahānaumokuākea Marine National Monument.