Benthic Surveys in Vatia, American Samoa: benthic cover derived from analysis of benthic images collected during belt transect surveys of coral demography in 2015 and 2020

Jurisdictional managers have expressed concerns that nutrients from the village of Vatia, Tutuila, American Samoa, are having an adverse effect on the adjacent coral reef ecosystem. Excess nutrient loads promote increases in algal growth that can have deleterious effects on corals, such as benthic algae outcompeting and overgrowing corals. Nitrogen and phosphorus can also directly impact corals by lowering fertilization success, and reducing both photosynthesis and calcification rates. Land-based contributions of nutrients come from a variety of sources; in Vatia the most likely sources are poor wastewater management from piggeries and septic systems.

NOAA scientists conducted benthic surveys to establish a baseline against which to compare changes in the algal and coral assemblages in response to nutrient fluxes.

The benthic cover data described here were generated from the quantitative analysis of photoquadrat benthic images using image analysis software, whereby random points are projected on each image and the benthic elements falling directly underneath each point are identified. The images were collected at 18 and 24 stratified randomly selected sites in 2015 and 2020 respectively, during belt transect surveys of coral demography by the NOAA Ecosystem Sciences Division (ESD; former Coral Reef Ecosystem Program CREP). Five of the 18 sites surveyed in 2015 were resurveyed periodically in 2016 (January, March, June, September, and December) to assess any short-term temporal changes in the benthic composition.

The benthic cover data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive. The benthic images and coral demography data are described and archived separately.

These data were generated from benthic surveys undertaken in Vatia Bay to establish a comprehensive baseline, status, and trends for benthic composition and coral demographics, and are part of a broader NOAA Coral Reef Conservation Program (CRCP) funded projects led by NCCOS and ESD to assess eutrophication impacts on coral ecosystem health in the bay. These efforts feed into the higher-level CRCP objectives by establishing an in-situ tracking system to assess the effects of management and mitigation strategies and activities in the target watersheds to reduce land-based sources of pollution.

Lozada-Misa P, Schumacher BD, Vargas-Angel B. 2017. Analysis of benthic survey images via CoralNet : a summary of standard operating procedures and guidelines. Pacific Islands Fisheries Science Center, PIFSC Administrative Report, H-17-02, 169 p. https://doi.org/10.7289/V5/AR-PIFSC-H-17-02.

Vargas-Angel B, Schumacher BD. 2018. Baseline surveys for coral reef community structure and demographics in Vatia Bay and Faga'alu Bay, American Samoa. Pacific Islands Fisheries Science Center, PIFSC Special Publication, SP-18-002, 38 p. https://doi.org/10.7289/V5/SP-PIFSC-18-002.

and

Vargas-Angel B, Huntington B. 2020. Status and Trends Assessment of Benthic Coral Reef Communities in Vatia Bay, American Samoa, 2015 - 2020. Pacific Islands Fisheries Science Center, PIFSC Data Report, DR-20-020, 34p. https://doi.org/10.25923/r7dd-wg50, https://repository.library.noaa.gov/view/noaa/27437

Monthly water quality sampling for nitrate/nitrite, ammonium, urea, total nitrogen, orthophosphorus, and total phosphorus data are also collected as part of this project to quantify the nutrient dynamics of the Bay. These additional data are described separately by the NOAA National Centers for Coastal Ocean Science (NCCOS); see citation below.

Whitall, D, M Curtis, A Mason, B Vargas-Angel. 2019. Excess Nutrients in Vatia Bay, American Samoa: Spatiotemporal Variability, Source Identification and Impact on Coral Reef Ecosystems. NOAA Technical Memorandum NOS NCCOS 266. Silver Spring. 69 pages. doi:10.25923/j8cp-x570.

Raw survey data includes metadata for each survey; site characteristics; unique image name and individual point observations identified at three functional group levels of benthic cover: Tier 1 (e.g., hard coral, macroalgae, etc.), Tier 2 (e.g., massive, branching, foliose, encrusting, etc.), and Tier 3 (e.g., Astreopora sp, Favia sp, etc.).

Raw survey data derived from 2016 images includes metadata of each survey; site characteristics; unique image name and individual point observations at one functional group level of benthic cover: Tier 1 (e.g.,hard coral, macroalgae, etc.)

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, NOAA 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. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Vatia Bay, Tutuila, American Samoa

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NOAA Coral Reef Ecosystem Sciences Division (ESD) Data Sharing Recommendations, version 9.0 updated August 12, 2015:

The ESD welcomes the opportunity to collaborate on research issues contributing to the scientific basis for better management of marine ecosystems. The ESD has a very diverse set of field activities that generates large volumes of data using an array of data collection protocols.

The following recommendations are for your consideration as you use this data:

1) Data analyses should take all field exigencies into account. The most effective way to do this would be active collaboration with ESD principal investigators.

2) In all presentations, product releases, or publications using data generated by ESD, proper acknowledgement of both ESD and the individuals responsible for data collection is expected. Citing the DOI (if available) is preferred, a non-DOI example is listed below.

3) If you collect or generate data for the same study areas, ESD requests that you share relevant information on complimentary data collections.

4) Those receiving data are strongly urged to inform the ESD Data Management Team of any errors and discrepancies that are discovered during the course of using these data. They are further urged to bring to the attention of the Team all problems and difficulties encountered in using these data. This information is necessary in order to improve the collections and to facilitate more efficient and economical data processing and retrieval. The users are asked to supply copies of any missing data that may be located, and to provide information as to significant subsets and special aggregations of data that are developed in using the material provided.

Example citation:

"This publication makes use of data products provided by the Ecosystem Sciences Division (ESD), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), with funding support from the NOAA Coral Reef Conservation Program (CRCP). The analysis and interpretations presented here are solely that of the current authors."

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

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Please cite NOAA Ecosystem Sciences Division (ESD) when using the data.

Example

Cite as: Vargas-Angel, Bernardo; Ecosystem Sciences Division; Pacific Islands Fisheries Science Center (2022). Benthic Surveys in Vatia, American Samoa: benthic percent cover derived from analysis of benthic images collected during belt transect surveys of coral demography in 2015 and 2020. NOAA National Centers for Environmental Information. https://www.fisheries.noaa.gov/inport/item/31611

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PIFSC Oracle database view: MV_BIA_CNET_ANALYSIS_DATA

SELECT *

FROM MV_BIA_CNET_ANALYSIS_DATA

WHERE OBS_YEAR = 2015, 2020

AND SITE IN (SELECT SITE FROM LIST_OF_SITES WHERE COMMENT_ = 'VATIA')

Data sets derived from image analysis are highly reliable within the stipulated taxonomic context. Each time a production run is performed for a region a calibration exercise is conducted by all staff that will participate in that round of image analysis classification. Usually 100-150 photos are selected from the photos being processed as part of the production run series, or other region-relevant photo streams. Then, image analysis software assigns 10 random fixed points per photo. Each photo analyst is asked to classify the same set of points in each of the photos used as part of the calibration exercise. The goal of the calibration exercise is to assess inter-observer variability. Inter-observer variability rates are available upon request for each production run.

The data set derived from the image analysis is as good as the images themselves; poor images with low contrast, inappropriate white balance, or out of focus may have to be discarded. Therefore, percent cover estimates for some sites may derive from differing number of points between sites. Although the analysis process is statistically robust to allow for differing n (points) between sites, users should be aware of this limitation.

Classification is completed to the functional group/genus level (Tier 1-Tier 3).

The same method of image analysis was used at each surveyed site.

Quality control is enforced by means of point-to-point, inter-observer calibration exercises that are conducted before each image analysis production series. Training modules and standard operating procedures have also been developed and documented to ensure improved performance and consistent imagery analysis results produced by multiple analysts.

NOAA IRC and NOAA Fisheries ITS resources and assets.

The methodology to analyze benthic imagery using CoralNet to derive benthic cover values.

The data described here were derived from the analysis of benthic images collected along photo-quadrat surveys by the NOAA Ecosystem Sciences Division (ESD):

In 2015 photo quadrat images were taken every meter from the 1-m to the 15-m mark along TWO, 18-m transects per site (n = 30 images).

In 2020 photo quadrat images were taken every meter from the 1-m to the 30-m mark along one 30-m transect line (n = 30 images).