Marine Debris Survey and Removal Efforts in the Northwestern Hawaiian Islands from 1999 to 2021

The marine debris data included in this dataset are from annual in-water surveys conducted from 1999 to 2021 at the reefs, atolls and islands in the Northwestern Hawaiian Islands (NWHI) by the NOAA Pacific Islands Fisheries Science Center (PIFSC), Ecosystem Sciences Division (ESD) with funding from Papahanaumokuakea Marine National Monument (PMNM), and NOAA's Marine Debris (MDP) and Damage Assessment Remediation and Restoration (DARRP) Programs.

These surveys and removal efforts of marine debris were conducted primarily during ship-based missions to the NWHI, and also as fly-in missions. During a mission, surveys were conducted by divers based on small boats launched either from a ship or from the shore. Two survey methods were used to search for marine debris; tow and swim surveys. Tow surveys were used in the relatively even-depth (usually less than 10 meters deep), contiguous backreef habitats, typically at Midway Atoll, Kure Atoll and Pearl and Hermes Atoll. Two free-divers were towed behind a small boat to search for debris throughout the water column. Swim surveys were used primarily in the comparatively high-relief and patchy lagoonal reef habitats of Maro Reef and Pearl and Hermes Atoll. During swim surveys, two or more snorkelers swam across the reefs to search for debris while being directed by the small boats to follow pre-planned routes. Survey areas and routes were chosen based on regional reef morphology and past debris accumulation records.

During a survey, if debris larger than 0.012 cubic meters (size of a small toolbox) was encountered, descriptive information about the debris and its location (i.e., type, color, size, biofouling, estimated depth, substrate composition/color) were recorded and a GPS waypoint was taken. Debris was removed if determined to be safe to do so and without causing damage to the surrounding coral reef habitat. Once removed, the volume of removed debris was estimated and recorded. At the end of the survey or if the small boat reached its capacity, the boat returned to the ship or to the shore and the boats debris load was weighed and recorded. Up to 4 small boats in one day concurrently conducted surveys during a mission.