National Coral Reef Monitoring Program: Benthic Cover Derived from Analysis of Benthic Images Collected during Stratified Random Surveys (StRS) across the Mariana Archipelago since 2014

This data has been combined into a US Pacific-wide InPort record:  https://www.fisheries.noaa.gov/inport/item/77771.

The data described here result from benthic photo-quadrat surveys conducted along transects at stratified random sites across the Mariana archipelago in 2014, 2017, and 2022 as a part of Rapid Ecological Assessment (REA) surveys for corals and fish.  Benthic habitat imagery were quantitatively analyzed using the Coral Point Count with Excel extensions (CPCe; Kohler and Gill, 2006) software from 2010-2014 and using the web-based annotation tool CoralNet (Beijbom et al. 2016) from 2015 to present.  Images are analyzed to produce three functional group levels of benthic cover: Tier 1 (e.g., hard coral, soft coral, macroalgae, turf algae, etc.), Tier 2 (e.g., Hard Coral = massive, branching, foliose, encrusting, etc.; Macroalgae = upright macroalgae, encrusting macroalgae, bluegreen macroalgae, and Halimeda, etc.), and Tier 3 (e.g., Hard Coral = Astreopora sp, Favia sp, Pocillopora, etc.; Macroalgae = Caulerpa sp, Dictyosphaeria sp, Padina sp, etc.). 

A stratified random sampling (StRS) design was employed to survey the coral reef ecosystems across the region. The survey domain encompassed the majority of the mapped area of reef and hard bottom habitats in the 0-30 m depth range. The stratification scheme included island, reef zone, and depth.  Sampling effort was allocated based on strata area and sites were randomly located within strata.  Sites were surveyed using photo-quadrats along transects to collect benthic imagery to ultimately produce estimates of relative abundance (benthic cover), frequency of occurrence, benthic community taxonomic composition and relative generic richness.

The StRS design effectively reduces estimate variance through stratification using environmental covariates and by sampling more sites rather than sampling more transects at a site.  Therefore, site-level estimates and site to site comparisons should be used with caution.

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Organization: National Oceanic and Atmospheric Administration, Department of Commerce