National Coral Reef Monitoring Program: Stratified Random Surveys (StRS) of Coral Demography (Adult and Juvenile Corals) across Wake Island from 2014-03-16 to 2014-03-20 (NCEI Accession 0159162)

The data described here result from benthic coral demographic surveys for two life stages (juveniles, adults) across Wake Island in 2014. Juvenile colony surveys include morphology and size. Adult colony surveys record morphology, colony size, partial mortality in two categories - old dead and recent dead, cause of recent dead partial mortality, and non-lesion forming condition including bleaching and disease).
A two-stage 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 belt transects to collect juvenile and adult coral colony metrics. These data provide information on juvenile and adult coral abundance (density, proportion occurrence, and total colony abundance), size distribution, partial mortality, prevalence and abundance of recent mortality and cause, prevalence of disease and bleaching, and diversity.
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.

本数据集源自2014年在威克岛（Wake Island）周边海域开展的底栖珊瑚种群生态学调查（benthic coral demographic survey），覆盖珊瑚两个生活史阶段：幼体（juvenile）与成体（adult）。幼体珊瑚群落调查涵盖形态特征与个体尺寸；成体珊瑚群落调查则记录群落形态、群落规模，以及两类局部死亡（partial mortality）现象——陈旧死亡与近期死亡，同时记录近期局部死亡的诱因，以及无损伤病灶形成的健康异常状况（涵盖珊瑚白化（bleaching）与珊瑚病害（disease））。

本调查采用两阶段分层随机抽样设计（two-stage stratified random sampling, StRS），对美国太平洋全域的珊瑚礁生态系统开展普查。调查覆盖0至30米水深范围内绝大多数已测绘的珊瑚礁与硬质底栖生境（hard bottom habitat）区域。分层方案涵盖所有区域的岛屿、礁区与水深因子，主夏威夷群岛（Main Hawaiian Islands）还额外加入生境结构类型维度。采样工作量依据各层位的面积进行分配，样点在对应层位内随机布设。调查采用样带法（belt transect）采集幼体与成体珊瑚群落的各项测量指标。

本数据集涵盖的信息包括：幼体与成体珊瑚的丰度（密度、出现占比与群落总丰度）、尺寸分布、局部死亡情况、近期死亡的流行率与丰度及其诱因、珊瑚病害与白化的流行率，以及生物多样性。

两阶段分层随机抽样设计通过引入环境协变量进行分层，以及增加样点数量而非单样点内的样带数量，有效降低了估计方差。因此，使用样点层面的估计值及跨样点比较结果时需谨慎。