Benthic cover derived from structure from motion images collected during marine debris surveys at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands from 2021-09-13 to 2021-09-14 (NCEI Accession 0253462)
The benthic cover and fishing-net related data described in this dataset are derived from the GIS analysis of benthic orthophotos. Source imagery was collected by snorkelers using a Structure from Motion (SfM) approach from at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands (NWHI). This data was collected from September 13-14, 2021 as part of a joint marine debris removal mission with the NOAA Fisheries, Ecosystem Sciences Division (ESD) and non-profit organization Papahānaumokuākea Marine Debris Project aboard the charter vessel M/V IMUA.
This 2021 benthic cover dataset follows a 2018 benthic cover dataset from SfM surveys of net-impacted and paired control sites; sites were revisited in 2021 to compare the benthic composition of net-impacted sites to control sites three years after net removal. Only a subset of 2018 sites were successfully relocated in 2021, therefore new paired control sites were also included.
The photographs from each site were processed using Agisoft Metashape software to generate orthomosaic images that were analyzed in ArcGIS for benthic cover using a random point approach. For net-impacted sites, twenty random points were assigned to each orthophoto within the shapefile of the 2018 net polygon overlaid in the appropriate area. For control sites, the net shapefile from 2018 was overlaid in the center of the image and 20 random points were assigned within that polygon. For all sites, each point was classified into one of six benthic categories: algae, sand, bare substrate, coral, sponge, or crustose coralline algae (CCA). The annotated points for each site were converted to percent cover for each benthic category.
This 2021 benthic cover dataset follows a 2018 benthic cover dataset from SfM surveys of net-impacted and paired control sites; sites were revisited in 2021 to compare the benthic composition of net-impacted sites to control sites three years after net removal. Only a subset of 2018 sites were successfully relocated in 2021, therefore new paired control sites were also included.
The photographs from each site were processed using Agisoft Metashape software to generate orthomosaic images that were analyzed in ArcGIS for benthic cover using a random point approach. For net-impacted sites, twenty random points were assigned to each orthophoto within the shapefile of the 2018 net polygon overlaid in the appropriate area. For control sites, the net shapefile from 2018 was overlaid in the center of the image and 20 random points were assigned within that polygon. For all sites, each point was classified into one of six benthic categories: algae, sand, bare substrate, coral, sponge, or crustose coralline algae (CCA). The annotated points for each site were converted to percent cover for each benthic category.
Dataset Citation
- Cite as: NOAA Pacific Islands Fisheries Science Center, Ecosystem Sciences Division (2022). Benthic cover derived from structure from motion images collected during marine debris surveys at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands from 2021-09-13 to 2021-09-14 (NCEI Accession 0253462). https://www.ncei.noaa.gov/archive/accession/0253462. In Ecosystem Sciences Division, Pacific Islands Fisheries Science Center. Benthic cover and other related datasets derived from Structure-from-Motion (SfM) imagery of coral reef ecosystems in Pacific Islands Regions. [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://www.ncei.noaa.gov/archive/accession/PIFSC-SfM-DerivedData. Accessed [date].
Dataset Identifiers
ISO 19115-2 Metadata
gov.noaa.nodc:0253462
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Ordering Instructions | Contact NCEI for other distribution options and instructions. |
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NOAA National Centers for Environmental Information +1-301-713-3277 ncei.info@noaa.gov |
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NOAA National Centers for Environmental Information ncei.info@noaa.gov |
Time Period | 2021-09-13 to 2021-09-14 |
Spatial Bounding Box Coordinates |
West: -175.817246
East: -175.7902661
South: 27.82745706
North: 27.89114188
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Dataset Progress Status | Complete - production of the data has been completed Historical archive - data has been stored in an offline storage facility |
Data Update Frequency | As needed - NCEI Accession 0253462 was revised and a new version of the archival package was published. Updates to existing archival packages may provide additional files or replace obsolete files. The latest version contains the most complete and up-to-date representation of this archival information package. All of the files received prior to this update are available in the preceding version of this accession. Please see journal.txt in the /about directory for additional details on changes made. |
Supplemental Information | Note: The dataset abstract references source imagery. These images were not included with this submission. In this accession, NCEI has archived multiple versions of these data. The latest (and best) version of these data has the largest version number. |
Purpose | The purpose of the Structure from Motion (SfM) surveys at Pearl and Hermes Atoll is to understand how derelict fishing nets alter the benthic community composition of the reef, how these impacts last over time once the net is removed, and if the benthic community can recover over time. This study leveraged SfM, an emerging photogrammetry technique, to allow efficient data collection alongside marine debris survey and removal efforts. The Papahānaumokuākea Marine National Monument (PMNM) includes the 1200 nautical mile chain of atolls and islets known as the Northwestern Hawaiian Islands (NWHI) that are geographically positioned as a repository for marine debris. Marine debris circulates within the North Pacific Subtropical Gyre until it encounters the atolls of the NWHI. The Ecosystem Sciences Division (ESD) at NOAA Fisheries has conducted both ship- and shore-based missions in the NWHI to survey for and remove derelict fishing gear and many other types of marine debris. Exploratory and opportunistic efforts began in 1996 that evolved into ~annual cruises. |
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Last Modified: 2025-04-16T13:16:15Z
For questions about the information on this page, please email: ncei.info@noaa.gov
For questions about the information on this page, please email: ncei.info@noaa.gov