Guam Long-term Coral Reef Monitoring Program Benthic Images since 2010

The Government of Guam's Comprehensive Long-term Monitoring at Permanent Sites in Guam project, also known as the Guam Long-term Coral Reef Monitoring Program (GLTMP), is a NOAA-funded project currently coordinated through the University of Guam Marine Laboratory. The program involves the regular, intensive collection of data for a suite of coral reef ecosystem health parameters at high priority reef areas (HPRAs) around Guam, as well as critical support for coral bleaching response and other activities carried out by the multi-partner Guam Coral Reef Response Team. The program currently utilizes a split-panel sampling approach, whereby a mix of permanent and non-permanent sampling stations (one sampling station = one transect) are visited within each HPRA. The HPRAs were selected by an advisory body comprised of reef managers, researchers, and technicians. The locations of the sampling stations within each HPRA are generated randomly using GIS software. Various coral reef surveys are carried out on an annual basis along the seaward slope between 7 and 15 m depth in the Tumon Bay Marine Preserve and in East Agana Bay, while surveys are carried out biennially within the Piti Bomb Holes Marine Preserve, the Achang Reef Flat Marine Preserve, the eastern side of the Cocos Barrier Reef (Cocos-East), and Fouha Bay. Surveys were also carried at along reef margin (1–2 m) and slope (2–15 m) of Western Shoals, in Apra Harbor, in 2011. The surveys, which are currently conducted by University of Guam Marine Laboratory biologists, and which were supported by NOAA PIRO through 2019, currently include benthic photo transects, stationary point count fish surveys, macroinvertebrate belt transects, and chain-length rugosity surveys. The GLTMP has conducted surveys at the Tumon and East Agana HPRAs since 2010 and the Piti HPRA since 2012. Data collection for the Achang and Cocos-East HPRAs began in 2014 and at the Fouha Bay HPRA in 2015. Baseline data is available for the Western Shoals HPRA from 2011 but this site has not been re-visited since its establishment due to shifting management priorities.

The data products described herein include the benthic photo transect images used to document the status and trends for benthic cover and composition at the monitoring sites mentioned above. Benthic cover and coral and algal generic diversity are currently assessed using digital photo transects. The still images provide a permanent record of the transects. Benthic cover estimates were initially derived from the photo transect images using Coral Point Count with Excel extensions (CPCe; Kohler and Gill 2006) point sampling software, but the web-based image analysis platform CoralNet (Beijborn et al. 2012, Beijborn 2015) was used beginning with the 2019 images.

The stated goals of the Guam Long-term Coral Reef Monitoring Program (GLTMP) are to determine the status and trends of selected coral reef ecosystem indicators to inform resource managers' decision-making process, provide managers with early notice of abnormal conditions, provide data to better understand the dynamic nature of the island's coastal ecosystems, allow resource agencies to meet certain legal and Congressional mandates, and measure progress towards performance goals. Benthic cover data collected by the GLTMP at several High Priority Reef Areas around Guam provide documentation of the structure and condition of the benthic communities at these sites; data from multiple visits can be used in time series analyses to determine trends in key ecosystem parameters.

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The following FGDC sections are not currently supported in InPort, but were preserved and will be included in the FGDC export:

- Spatial Reference Information (FGDC:spref),

Tumon Bay in 2010 (10 permanent and 10 non-permanent stations), 2012 (12 permanent and 9 non-permanent stations), 2014 (12 permanent and 4 non-permanent stations), 2015 (12 permanent and 10 non-permanent stations), 2017 (12 permanent and 10 non-permanent stations), 2018 (12 permanent stations), 2019 (12 permanent and 10 non-permanent stations), 2020 (12 permanent and 10 non-permanent stations); 2021 (12 permanent and 10 non-permanent stations); and 2022 (12 permanent and 10 non-permanent stations)

East Agana Bay in 2010 (10 permanent and 10 non-permanent stations), 2012 (10 permanent stations), 2014 (10 permanent stations), 2015 (10 permanent stations), 2017 (10 permanent and 12 non-permanent stations), 2018 (10 permanent stations), 2019 (9 permanent and 6 non-permanent stations), 2020 (10 permanent and 10 non-permanent stations), 2021 (10 permanent and 10 non-permanent stations), and 2022 (10 permanent and 10 non-permanent stations)

Western Shoals in 2011 (11 permanent and 12 non-permanent stations)

Piti in 2012 (10 permanent and 10 non-permanent stations), 2014 (10 permanent and 2 non-permanent stations), 2017/18 (8 permanent and 10 non-permanent stations), 2020 (10 permanent and 10 non-permanent stations), and 2022 (10 permanent and 10 non-permanent stations)

Achang in 2014 (11 permanent and 3 non-permanent stations), 2018 (10 permanent and 10 non-permanent stations), and 2021 (10 permanent and 10 non-permanent stations)

Cocos-East in 2014 (3 permanent and 2 non-permanent stations), 2018 (10 permanent stations), and 2021 (10 permanent and 10 non-permanent stations)

Fouha Bay in 2015 (13 permanent stations), 2019 (13 permanent stations), and 2021 (13 permanent stations)

While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, the University of Guam Marine Laboratory and the Guam Coastal Management Program cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. The University of Guam Marine Laboratory and the Guam Coastal Management Program make no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Tumon Bay

East Agana Bay

Western Shoals

Piti (Tepungan) Bay

Achang

Cocos-East

Fouha Bay

Not applicable

Not applicable

Data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive.

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Please cite the Guam Coastal Management Program when using data collected prior to October 2013. Guam Coastal Management Program, Guam Bureau of Statistics and Plans, Government of Guam. Please cite the University of Guam Marine Laboratory when using data collected after (and including) October 2013.

Example citation:

For data collected from 2010 to 2012:

Guam Coastal Management Program (2019). Guam Long-term Coral Reef Monitoring Program Benthic Images since 2010. NOAA's National Center for Environmental Information, https://www.fisheries.noaa.gov/inport/item/47788.

For data collected after 2012:

University of Guam Marine Laboratory (2019). Guam Long-term Coral Reef Monitoring Program Benthic Images since 2010. NOAA's National Center for Environmental Information, https://www.fisheries.noaa.gov/inport/item/47788.

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Benthic images are organized and edited on the desktop workstation of the Monitoring Program Coordinator, with backup copies of each image and associated data files stored on an external hard drive and with the GSuite cloud storage service. Between 2010 and 2018 images were analyzed using CPCe installations on the workstation or laptop computer of individual monitoring team members. CPCe output files generated by other team members were obtained by the coordinator and modified to conform to the directory structure of the coordinator's computer. Spreadsheets containing raw CPCe data from across multiple sites and years were generated by compiling .cpc files using CPCe and assembling the raw data within a single master spreadsheet. In 2021, benthic images obtained at the HPRAS beginning in 2019 were uploaded to CoralNet, a web-based image analysis platform. The CoralNet robot was initially trained using images and CPCe data from 2015-2018. Approximately 5% to 20% of annotations (depending on the site) suggested by the CoralNet robot for the 2019-2022 images exceeded the 80% confidence threshold set for the source, but a human observer still verified each annotation manually. Beginning with the 2023 images, a lower confidence threshold will be used and the CoralNet robot's annotations will be considered confirmed and will not be reviewed by a human observer. The use of a lower overall confidence threshold value is justified by the very high (>95%) accuracy obtained by the robot for targeted benthic classes.

Benthic photo transect images capture an accurate representation of the area of reef visible within the image frame. Images are color-corrected within Adobe Lightroom, but otherwise are not digitally manipulated to alter the original content.

Comparisons for a given site across time could potentially be affected by changes in the benthic photo transect methodology. These changes are as follows:

Transect length: Benthic photo transect length for all sampling stations except the Western Shoals site was 25 meters between 2010 and 2016 and, except for the Fouha Bay site, 30 m beginning in 2017. Benthic photo transect length for the smaller Western Shoals site was 15 m and remained at 25 meter for the Fouha Bay site.

Image spacing: Between 2010 and 2012 benthic photos were captured every 0.5 meters along both sides of the transect tape. Overlapping did not appear to be an issue for most of the images collected during this time period; however, significant overlapping of images for the Piti site in 2012 was observed and was addressed by analyzing only every other image. Photos were taken every 1 meter beginning in 2014 in order to avoid overlapping images, and beginning in 2017 images were only taken along the left side of the transect.

Image analysis: Prior to 2014 a total of 25 points (random stratified using a 5 x 5 grid) were used to analyze each image in CPCe. For photos analyzed since (and including) 2014, a total of 16 points (random stratified using a 4 x 4 grid) are used.

Image quality: Image quality has improved over time with the availability of digital cameras capable of capturing higher resolution images and with more advanced functionality. A Canon PowerShot A720 IS digital camera (8 Megapixel sensor; 3264x2448 pixel image resolution) was used between 2010 and 2011, a Nikon Coolpix 36300 (16 Megapixel sensor; 4608x3456 pixel image resolution) was used for most sampling stations in 2012; and a Canon PowerShot ELPH 300 HS (12 Megapixel sensor; 4000x3000 pixel image resolution) was used for a limited number of sampling stations in 2012. The lower resolution PowerShot A720 was again used in 2014 due to the loss of the Nikon Coolpix and PowerShot ELPH cameras. Beginning in 2015 a Sony Cybershot RX-100 (20 Megapixel sensor; 5472x3648 pixel image resolution) has been used. The higher image resolution achieved by the more recent cameras allows for greater taxonomic resolution during image analysis, and likely allows for greater accuracy in the identification of benthic features, particularly for features, such as turf algae, crustose coralline algae, and small corals, that can be difficult to discern at lower image resolutions.

Camera frame/monopod: Initially, the camera/housing was mounted to a PVC frame/quadrat structure that allowed the consistent positioning of the camera directly above a 0.5 x 0.5 m quadrat. Only the portion of the images within the quadrat were analyzed using CPCe. A decision was made prior to the 2017 field season to instead utilize a PVC monopod. The monopod extends 1.15 m vertically and has a horizontal piece that extends 0.28 m horizontally. The camera housing is mounted at the end of the horizontal piece, rather than directly atop the vertical piece, in order to reduce the amount of monopod present within the image frame. The field of view captured using the Sony RX100/monopod combination is approximately 50% larger than that obtained using the frame/quadrat. Images first obtained at each site using the monopod, which was adopted in 2017, include the transect tape in the far right of the image in order to allow for the delineation of a 0.5 m by 0.5 m area and thus allow the comparison of CPCe results obtained using the two differently-sized image analysis areas.

Only hard-bottom habitats are surveyed. Surveys are conducted annually to biennially for the Tumon and East Agana sites, but are conducted on a less frequent basis at other sites. In addition, while all permanent sampling stations are generally surveyed each sampling period, surveys are not always conducted at the full set of non-permanent stations for each site during each sampling period. Below is a summary of the number of permanent and non-permanent sampling stations surveyed each year for each site:

Tumon Bay: 2010 (10 perm, 10 non-perm); 2012 (12 perm, 9 non-perm); 2014 (12 perm, 4 non-perm); 2015 (12 perm, 10 non-perm); 2017 (12 perm, 10 non-perm); 2018 (12 perm, 0 non-perm); 2019 (12 perm, 10 non-perm); 2020 (12 perm, 10 non-perm); 2021 (12 perm,10 non-perm); 2022 (12 perm, 10 non-perm)

East Agana Bay: 2010 (10 perm, 10 non-perm); 2012 (10 perm, 0 non-perm); 2014 (10 perm, 0 non-perm); 2015 (10 perm, 0 non-perm); 2017 (10 perm, 12 non-perm); 2018 (10 perm, 0 non-perm); 2019 (9 perm, 6 non-perm); 2020 (10 perm, 10 non-perm); 2021 (10 perm, 10 non-perm); 2022 (10 perm, 10 non-perm)

Western Shoals: 2011 (11 perm, 12 non-perm)

Piti Bay: 2012 (10 perm, 10 non-perm); 2014 (10 perm, 2 non-perm); 2017-2018 (8 perm, 6 non-perm); 2020 (10 perm, 10 non-perm); 2022 (10 perm, 10 non-perm)

Achang: 2014 (11 perm, 3 non-perm); 2018 (9 perm, 6 non-perm); 2021 (10 perm, 10 non-perm)

Cocos-East: 2014 (3 perm, 4 non-perm); 2018 (10 perm); 2021 (10 perm, 10 non-perm)

Fouha Bay: 2015 (13 perm); 2019 (13 perm); 2021 (13 perm)

The analysis of images collected through 2022 is complete and the results have all undergone quality control. As of the publication of this metadata record images the analysis of images obtained in 2023 have not yet been completed.

Individuals designated to carry out the benthic photo transect survey are thoroughly trained in the survey protocol. However, on occasion incorrect camera settings may have been used, or low light conditions resulted in blurry images. If, upon review of the images, it is determined that high quality benthic cover data cannot be derived from the images due to poor image quality, an attempt may be made to revisit the sampling station(s) and obtain new photo transect images.

University of Guam Marine Lab resources and assets

The Benthic Photo Transect Survey methodology, employed by the Guam Long-term Coral Reef Monitoring Program since 2010