National Coral Reef Monitoring Program: Benthic Images Collected from Stratified Random Sites (StRS) across the Hawaiian Archipelago from 2013-05-01 to 2013-10-31 (NCEI Accession 0159144)

The data described here are benthic habitat imagery that result from benthic photo-quadrat surveys conducted along transects at stratified random sites across the Hawaiian archipelago in 2013 as a part of Rapid Ecological Assessment (REA) surveys for corals and fish.
A stratified random sampling (StRS) design was employed to survey the coral reef ecosystems throughout the U.S. Pacific regions. 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 in all regions, as well as habitat structure type in the Main Hawaiian Islands. 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 (percent 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.

本数据集所描述的数据为底栖生境影像，其源自2013年针对珊瑚与鱼类开展的快速生态评估（Rapid Ecological Assessment, REA）项目中，沿夏威夷群岛各分层随机样点的样带开展的底栖样方摄影调查所获取的成果。
本次调查采用分层随机抽样（Stratified Random Sampling, StRS）设计，对美国太平洋区域全境的珊瑚礁生态系统进行普查。调查覆盖范围涵盖0至30米水深范围内绝大多数已测绘的礁体与硬质底栖生境区域。分层方案包含所有区域的岛屿、礁区及水深维度，以及主夏威夷群岛的生境结构类型。采样工作量依据各层的面积进行分配，且样点在各层内随机布设。调查团队沿样带使用底栖样方摄影的方式采集底栖生境影像，最终用于估算相对丰度（盖度百分比）、出现频率、底栖群落分类组成以及相对属丰富度。
分层随机抽样设计通过利用环境协变量开展分层，以及增加样点采样量而非增加单个样点处的样带数量，有效降低了估计方差。因此，在使用样点水平的估计值以及开展样点间比较时需格外谨慎。